阅读说明：本技术 一种用于可移动物体的低功耗定位系统及定位方法 (Low-power-consumption positioning system and positioning method for movable object ) 是由 斯考特·J·卡特 于 2016-03-03 设计创作，主要内容包括：提供了使用全球导航卫星系统(GNSS)用于定位可移动物体的低能耗技术。被附接至可移动物体的或被包括在可移动物体中的移动站能够与固定的基站双向地进行通信以确定可移动物体的位置。移动站可以向基站传达估计位置并且从基站接收移动站可见的GNSS卫星组。移动站能够从来自该卫星组的GNSS信号获取卫星定时信息并且向基站传达最低限度处理的卫星定时信息。基站能够确定移动站的位置并且将该位置传达回至移动站。通过将许多的处理卸载至基站,减少了移动站的能量消耗。(Low energy consumption techniques for locating movable objects using Global Navigation Satellite Systems (GNSS) are provided. A mobile station attached to or included in a movable object can bi-directionally communicate with a fixed base station to determine the position of the movable object. The mobile station may communicate the estimated position to the base station and receive a set of GNSS satellites visible to the mobile station from the base station. The mobile station can acquire satellite timing information from GNSS signals from the set of satellites and communicate minimally processed satellite timing information to the base station. The base station can determine the location of the mobile station and communicate the location back to the mobile station. By offloading much of the processing to the base station, the energy consumption of the mobile station is reduced.)

1. A positioning system for a movable object, the positioning system using a Global Navigation Satellite System (GNSS), the positioning system comprising:

a mobile station configured to be associated with a movable object, the mobile station comprising:

a mobile GNSS receiver configured to receive GNSS signals;

a mobile transceiver configured to communicate over a communication link including frequencies in an unlicensed Radio Frequency (RF) band; and

a mobile station hardware processor programmed to:

wake up at a time or under conditions specified in sleep parameters;

estimating a position of the mobile station;

estimating a direction of the mobile station;

transmitting, via the mobile transceiver, the estimated position of the mobile station, the estimated direction of the mobile station, and the local mobile clock value to the base station;

receiving information associated with a GNSS clock and acquisition parameters from a base station;

updating a local mobile clock value based at least in part on information associated with the GNSS clock;

causing a mobile GNSS receiver to acquire GNSS signals based at least in part on the acquisition parameters;

transmitting information related to chip transitions in the acquired GNSS signals to a base station;

receiving, from a base station, an updated location and information associated with updated sleep parameters;

updating the sleep parameter based at least in part on information associated with the updated sleep parameter from the base station; and is

And returns to sleep;

the positioning system further comprises a base station, the base station comprising:

a base station GNSS receiver configured to receive signals from a plurality of GNSS satellites;

a base transceiver station configured to communicate over a communication link that includes frequencies in the unlicensed Radio Frequency (RF) band; and

a base station hardware processor programmed to:

receiving an estimated position, an estimated direction, and a local clock value of the mobile station over the communication link;

transmitting one or more messages associated with updating a local mobile station clock value to a base station clock value representative of time of a GNSS satellite;

estimating acquisition parameters for the GNSS satellites based at least in part on the estimated position of the mobile station;

determining an estimated direction based in part on the mobile station based at least on the ordered list of GNSS satellites;

transmitting an ordered list of GNSS satellites with associated code phase information to the mobile station via the communication link;

receiving chip conversions from a mobile receiver via the communication link;

calculating an updated position of the mobile station using at least the chip transitions from the mobile receiver; and is

The updated location and information associated with the updated sleep parameters are transmitted to the mobile station.

2. The positioning system of claim 1, wherein the mobile station comprises one or more non-GNSS sensors including a Very Low Frequency (VLF) sensor, a rotation sensor, a vibration sensor, a heading sensor, a magnetic field sensor, an optical sensor, an RF sensor, an Electronic Article Surveillance (EAS) sensor, an ultrasonic sensor, an accelerometer, or a gyroscope.

3. The positioning system of claim 2, wherein the mobile station is configured to estimate its initial position and its orientation after exiting sleep mode based at least in part on information provided by one or more non-GNSS position sensors.

4. The positioning system of claim 1, wherein to determine the ordered list of GNSS satellites, the base station hardware processor is programmed to further determine a queue of GNSS satellites on the ordered list using an antenna pattern of the mobile station.

5. The positioning system of claim 4, wherein the weak directional GNSS satellite platoon of the antenna pattern is reduced.

6. The positioning system of claim 1, wherein the base station hardware processor is further programmed to synchronize the base station clock value to a time representative of the GNSS satellite.

7. The location system of claim 1, wherein the mobile station hardware processor is programmed to estimate a direction of the mobile station based on data from a dead reckoning sensor associated with the mobile station.

8. The location system of claim 1, wherein the mobile station hardware processor is programmed to estimate the direction of the mobile station based on a history of the location of the mobile station.

9. A method for positioning a movable object, the method comprising:

under control of a mobile station configured to be attached to or included in or on a movable object, the mobile station including a Global Navigation Satellite System (GNSS) receiver and transceiver configured to communicate bi-directionally over an RF link having an RF link frequency in a Radio Frequency (RF) band unlicensed for cellular communication:

determining an estimated position of the mobile station by non-GNSS techniques;

determining an estimated direction of the mobile station by non-GNSS techniques;

communicating the estimated position and the estimated direction of the mobile station over the RF link;

receiving satellite acquisition information over an RF link, the satellite acquisition information including a set of GNSS satellites predicted to be visible at an estimated position of a mobile station and a GNSS code phase associated with each GNSS satellite in the set;

obtaining GNSS signals from at least some of the set of GNSS satellites;

determining, at least in part, from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some GNSS satellites in the set;

communicating chip transition time information over the RF link; and

an updated position of the mobile station is received over the RF link, the updated position being determined based at least in part on the chip transition time information.

10. The method of claim 9, wherein determining the estimated position of the mobile station by non-GNSS techniques comprises determining the estimated position via dead reckoning.

11. The method of claim 9, wherein determining the estimated direction of the mobile station by non-GNSS techniques comprises determining the estimated position via dead reckoning or by a history of the position of the mobile station.

12. The method of claim 9, further comprising synchronizing a clock of the mobile station with a base station clock, wherein the base station clock is synchronized with time representative of the GNSS satellites.

13. The method of claim 9, wherein determining chip transition time information associated with GNSS code phases of the at least some GNSS satellites in the set comprises: calculating a quality indicator for the at least some of the GNSS satellites in the set, the quality indicator being associated with a quality of the GNSS signals received by the mobile station.

14. The method of claim 13, wherein the quality indicator comprises information associated with one or more of GNSS signal power, peak width in correlator output, or signal-to-noise ratio.

15. The method of claim 9, wherein determining chip transition time information comprises searching for chip transitions within a shift window based at least in part on an estimate of error in clock synchronization.

16. A mobile station configured to be attached to or included in or on a movable object, the mobile station comprising:

global Navigation Satellite System (GNSS) receiver and

a transceiver configured to communicate bi-directionally over a Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication,

the mobile station is configured to:

determining an estimated position of the mobile station by non-GNSS techniques;

determining an estimated direction of the mobile station by non-GNSS techniques;

communicating the estimated position and the estimated direction of the mobile station over the RF link;

receiving satellite acquisition information over an RF link, the satellite acquisition information including a set of GNSS satellites predicted to be visible at an estimated position of a mobile station and a GNSS code phase associated with each GNSS satellite in the set;

acquiring GNSS signals from at least some of the set of GNSS satellites;

obtaining GNSS signals from at least some of the set of GNSS satellites;

determining, at least in part, from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some GNSS satellites in the set;

communicating chip transition time information over the RF link; and

an updated position of the mobile station is received over the RF link, the updated position being determined based at least in part on the chip transition time information.

17. A method for positioning a movable object, the method comprising: under control of a base station, the base station comprising a Global Navigation Satellite System (GNSS) receiver and transceiver configured to communicate bi-directionally over an Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication:

receiving an estimated position of a movable object over an RF link;

receiving an estimated direction of the movable object over the RF link;

determining satellite acquisition information based at least in part on the estimated position and the estimated direction of the movable object, the information comprising a set of Global Navigation Satellite System (GNSS) satellites predicted to be visible at the estimated position of the movable object and a GNSS code phase associated with each GNSS satellite in the set;

communicating the satellite acquisition information over an RF link;

receiving chip transition time information associated with acquiring GNSS code phases from at least some of the GNSS satellites in the set over an RF link;

determining an updated position of the movable object based at least in part on the chip transition time information; and

the updated position is communicated over an RF link.

18. The method of claim 17, further comprising synchronizing a base station clock to a clock associated with a GNSS satellite.

19. The method of claim 17, further comprising queuing the set of GNSS satellites according to a ranking criterion.

20. The method of claim 19, wherein the ordering criterion comprises an antenna pattern of a GNSS antenna associated with the moving object or the presence of an obstacle in the vicinity of the moving object that can prevent reception of GNSS signals from satellites.

21. A base station, comprising:

a Global Navigation Satellite System (GNSS) receiver; and

a transceiver configured to communicate bi-directionally over a Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication,

the base station is configured to:

receiving an estimated position of a movable object over an RF link;

receiving an estimated direction of the movable object over the RF link;

determining satellite acquisition information based at least in part on the estimated position and the estimated direction of the movable object, the information comprising a set of Global Navigation Satellite System (GNSS) satellites predicted to be visible at the estimated position of the movable object and a GNSS code phase associated with each GNSS satellite in the set;

communicating the satellite acquisition information over an RF link;

receiving chip transition time information associated with acquiring GNSS code phases from at least some of the GNSS satellites in the set over an RF link;

determining an updated position of the movable object based at least in part on the chip transition time information; and

the updated position is communicated over an RF link.

22. A system for analyzing satellite acquisition data, the system comprising:

a non-transitory data storage configured to store satellite acquisition data related to attempts by a mobile station that is capable of moving in a tracking area to acquire signals from Global Navigation Satellite System (GNSS) satellites; and

a base system configured to communicate with a mobile station over a radio link, the base system comprising a hardware processor in communication with the non-transitory data store, the hardware processor programmed to:

analyzing the satellite acquisition data using a machine learning algorithm; and

generating GNSS satellite selection criteria for a plurality of mobile stations based at least in part on the machine learning analysis, the satellite selection criteria comprising an ordered list of GNSS satellites;

wherein the base system is configured to transmit satellite selection criteria comprising an ordered list of GNSS satellites to the mobile station to enable the mobile station to preferentially select a satellite selection therefrom to acquire signals.

23. The system of claim 22, wherein the hardware processor is programmed to infer from the machine learning analysis the presence of an obstacle that prevents reception of GNSS satellite signals at a particular location in a tracking area or in a particular direction.

24. The system of claim 22, wherein the hardware processor is programmed to:

accessing geospatial data of a Geographic Information System (GIS); and

and determining that no obstacle exists in the GIS geographic space data.

25. The system of claim 22, wherein the model of the tracking area includes a location of an obstacle.

26. The system of claim 23, wherein the hardware processor is programmed to not list satellites in a particular orientation relative to the tracking area in an ordered list of satellites in communication with a mobile station, wherein the presence of the obstruction prevents reception of GNSS satellite signals.

27. The system of claim 22, wherein the machine learning algorithm comprises a neural network, a decision tree, a support vector machine, a probabilistic method, a bayesian network, or a data mining algorithm.

28. The system of claim 22, wherein at least one of the mobile stations is attached to or in a shopping cart or to or in or on a wheel of a shopping cart.

29. The system of claim 22, wherein the tracking area comprises a portion of a parking lot associated with a store.

30. The system of claim 22, wherein the satellite acquisition data comprises an indication that a mobile station failed to acquire a GNSS satellite.

31. The system of claim 30, wherein the satellite acquisition data includes an indication of: the width of the peak in the correlator output exceeds a threshold.

32. The system of claim 22, wherein the hardware processor is programmed to infer that a mobile station is malfunctioning from a machine learning analysis of the satellite acquisition data.

33. The system of claim 32, wherein the hardware processor is programmed to mark a mobile station as a candidate for maintenance.

34. The system of claim 22, further comprising the mobile station, wherein the mobile station comprises:

a Radio Frequency (RF) mobile communication system configured to operate an RF link having an RF link frequency in an RF band unlicensed for cellular communication;

a mobile GNSS receiver; and

a dead reckoning system including a non-GNSS sensor is configured to use measurements from the non-GNSS sensor to provide an estimated position of a mobile station.

35. A system for analyzing satellite acquisition data, the system comprising:

a non-transitory data storage configured to store satellite acquisition data related to attempts by a mobile station that is capable of moving in a tracking area to acquire signals from Global Navigation Satellite System (GNSS) satellites; and

an infrastructure system configured to wirelessly communicate with a mobile station, the infrastructure system comprising a hardware processor in communication with the non-transitory data storage, the hardware processor programmed to:

analyzing the satellite acquisition data using a machine learning algorithm; and

generating a queue of satellites visible in a tracking area that a mobile station is capable of moving based at least in part on a machine learning analysis;

wherein the base system is configured to transmit a queue to a mobile station.

36. The system of claim 35, wherein the hardware processor is programmed to learn from the machine learning analysis the presence of an obstacle that prevents GNSS satellite signal reception at: (1) a particular position in the tracking area, or (2) a particular orientation relative to the tracking area.

37. The system of claim 35, wherein the machine learning algorithm comprises a neural network, a decision tree, a support vector machine, a probabilistic method, a bayesian network, or a data mining algorithm.

38. The system of claim 35, wherein the mobile station is attached in or on a shopping cart, or in or on a wheel of a shopping cart.

39. The system of claim 35, wherein the satellite acquisition data comprises: an indication that the GNSS satellite was not acquired by the mobile station.

40. The system of claim 35, wherein the hardware processor is programmed to infer that a mobile station is malfunctioning based on a machine learning analysis of the satellite acquisition data.

41. The system of claim 35, wherein the base system comprises a base station in communication with a remote server over a network.

42. The system of claim 35, further comprising the mobile station, wherein the mobile station is configured to use the ordering to select a satellite from which to acquire a signal.

43. The system of claim 35, further comprising the mobile station, wherein the mobile station is configured to use satellite selection criteria to select satellites to be used for position estimation.

44. The system of claim 35, wherein the hardware processor, in generating the rankings, is configured to rank first visible satellites higher than second visible satellites based on determining that it is more desirable to use the first visible satellites for position estimation.

45. The system of claim 35, wherein the satellite selection criteria specifies an order in which the mobile station attempts to acquire signals from satellites when there is a particular incident.

46. The system of claim 35, wherein the satellite selection criteria specifies that a first satellite is to be used by the mobile station for backup when the mobile station is unable to acquire signals from a second satellite.

47. The system of claim 35, wherein the hardware processor, in generating the ordered list, is configured to rank a first visible satellite higher than a second visible satellite based on determining that it is more desirable to use the first visible satellite for position estimation.

48. The system of claim 35, wherein the base system comprises a base station in wireless communication with the mobile station, and comprising a computing device in communication with the base station over a wireless network.

49. The system of claim 48, wherein the hardware processor is in the computing system.

Technical Field

The present disclosure relates generally to systems and methods for locating movable objects, and more particularly to providing low power consumption location systems and location methods for movable objects using Global Navigation Satellite Systems (GNSS) when low energy is used on the movable objects.

Background

GNSS technology can be used to determine the location of a movable object. A GNSS can include a constellation of earth-orbiting satellites each broadcasting an encoded Radio Frequency (RF) signal. The constellation may include 27 or more satellites, so that at any time there are many satellites in the sky (above the horizon) in almost any particular region of the earth. A GNSS receiver is capable of receiving signals from a plurality of satellites that are visible to the receiver (e.g., above the receiver's horizon) and processing the received signals to determine the receiver's position relative to the earth.

Disclosure of Invention

Estimating the position of a movable object using GNSS may require significant energy consumption in a GNSS receiver at the movable object, since the GNSS receiver must acquire GNSS signals from multiple GNSS satellites and process the GNSS signals. There is a need for systems and methods that can provide a position fix or position estimate for a movable object using GNSS while using lower energy at the movable object in determining the position estimate. As used herein, location and position are generally used interchangeably unless the context clearly dictates otherwise.

In one embodiment, a mobile station attached to or included in a movable object can bi-directionally communicate with a fixed base station to determine the position of the movable object. The two-way communication may be a Radio Frequency (RF) link in an RF band (non-cellular communication band) that is not licensed by the radio communication department. The mobile station may communicate the estimated location to the base station. The estimated position may be based on dead reckoning by the movable object or based on information from non-GNSS position sensors on the movable object. The mobile station can receive from the base station a set of GNSS satellites that are visible to the mobile station. The mobile station can acquire satellite timing information from GNSS signals from the set of satellites and communicate minimally processed satellite timing information to the base station. The base station can determine the location of the mobile station and communicate the location back to the mobile station. By offloading much of the GNSS location processing to the base station (which is typically powered by the main power system), the energy consumption of the mobile station (which may be battery powered) is reduced.

In various embodiments, a low energy GNSS positioning system may use pseudolites that transmit GNSS-like signals to a mobile station over an unlicensed RF band that is close in frequency to GNSS satellite transmission frequencies. A GNSS receiver in a mobile station is capable of receiving signals on both GNSS satellite transmission frequencies and pseudolite transmission frequencies. In some such embodiments, the pseudolite transmission frequency is in the range of 1626.5MHz to 1645.5 MHz.

Embodiments of the low energy GNSS positioning techniques described herein can be used in applications including, but not limited to: the mobile cart is positioned in a retail store environment (e.g., a shopping cart), a warehouse environment (e.g., a warehouse cart), a medical facility (e.g., a medical equipment cart, a hospital bed), or a transportation hub (e.g., a luggage cart). Other applications include low energy usage states for other types of movable objects, including humans or animals. In other applications, the movable object can include an object that can move under its own power (e.g., an electric vehicle, a golf cart, a motorized device, an off-road vehicle, etc.) or an object that can be moved by another vehicle or mechanism (e.g., a trailer, a container, a pallet, heavy equipment, etc.).

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Neither this summary nor the following detailed description is intended to define or limit the scope of the inventive subject matter.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 illustrates an example system setup involving a low energy GNSS mobile system;

FIGS. 2A and 2B illustrate an example embodiment of a low energy GNSS mobile system;

FIG. 3 illustrates example processing functions and communication functions performed in a low energy GNSS mobile system;

FIG. 4 illustrates an example active period of a mobile station;

FIG. 5 illustrates example pre-processed GNSS data;

FIGS. 6A and 6B illustrate example operational scenarios of a low energy GNSS mobile system;

FIG. 7A illustrates a flow for synchronizing clocks of mobile stations;

FIG. 7B illustrates a flow for synchronizing clocks of mobile stations involving a link repeater;

FIG. 8 illustrates an example embodiment of a low energy GNSS mobile system including pseudolites;

FIG. 9 illustrates an example state diagram related to a low energy GNSS mobile system in an example retail application.

Throughout the drawings, reference numerals may be reused to indicate correspondence between reference elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the present disclosure.

Detailed Description

Overview of satellite navigation

Global Navigation Satellite Systems (GNSS) include a constellation of orbiting satellites that provide position information to GNSS receivers on earth. A GNSS receiver acquires and processes Radio Frequency (RF) signals from multiple GNSS satellites to determine the position of the receiver. For example, satellite signals include navigation data (e.g., ephemeris (precise satellite orbit data), almanac (satellite network data and ionosphere correction parameters), and satellite atomic clock data) that can be used to determine the position and velocity of satellites relative to the earth. The satellite signal also includes a code sequence that uniquely identifies the satellite. The information in the satellite signal is encoded as a phase modulation of the RF carrier frequency. The frequency of the phase modulation is referred to as the chip rate.

GNSS receivers can measure satellite signals and time align the code sequences of the receiver generated and receiver measured versions to identify the time of arrival (TOA) of a defined point in the code. The GNSS satellite clocks are synchronized. TOA data taken from three satellites in view of the receiver can be used to determine the three-dimensional position of the receiver if the receiver clock is synchronized to the satellite clock. However, since the GNSS receiver is typically not synchronized to the satellite clocks, the signals from the fourth satellite are used to determine the time offset between the receiver clock and the satellite clocks. GNSS signals acquired from four satellites can be converted into the position (e.g., longitude, latitude, and altitude) of a receiver in a geodetic system. In practice, signals from more than four satellites visible to the receiver may be acquired to provide enhanced accuracy or error detection or correction. Indeed, depending on the constellation geometry, the presence of nearby buildings, vehicles, structures or terrain (e.g., hills, locations of receivers in actual canyons or urban canyons), elevation cut-off angles (e.g., using only satellites above the cut-off angle), etc., 6 to 12 satellites may be simultaneously visible at a particular location.

The systems and methods disclosed herein can be used with any type of GNSS including, for example, the NAVSTAR Global Positioning System (GPS), the russian global navigation satellite system (GLONASS), the european union galileo positioning system, the indian regional navigation satellite system, the chinese BeiDou (BeiDou or COMPASS) navigation satellite system, and the like. In many of the exemplary embodiments described below, the systems and methods are described with reference to a GPS system, but this is for purposes of illustration and not limitation.

In GPS, each satellite continuously transmits navigation information at two carrier frequencies: l1 (at 1575.42MHz) and L2 (at 1227.60 MHz). The navigation information is encoded using a pseudorandom noise (PRN) code, and the carrier frequency is modulated with the code. A variety of codes are used, including coarse/acquisition (C/a) codes and fine (P) codes, which can be encrypted (by modulation using an encryption (W) code) to provide an encrypted P (y) code (which can only be decrypted with a classified decryption key). The C/a code is modulated only onto the L1 carrier frequency, while the p (y) code is modulated onto both the L1 and L2 carrier frequencies. The PRN code is different for each satellite in the constellation so the GPS receiver can determine from which satellite the navigation signal was received. The chip rate of the C/A code is 1.023MHz and the chip rate of the P code is 10.23 MHz.

The navigation messages are also modulated onto the carrier frequency (at a much lower modulation frequency than the C/a code or the p (y) code). The navigation information includes satellite ephemeris (precise orbit data), atomic clock parameters, and almanac (coarse orbit and state information for all satellites in the constellation). The ephemeris for each satellite is updated every two hours, typically four hours, while the almanac is typically updated every day.

Because all of the navigation information is modulated onto the same L1 carrier frequency, the signal must be separated (e.g., decoded) after demodulation by the receiver. If the almanac information has been previously acquired by the receiver, the receiver can select satellites to listen to (e.g., those satellites that are visible to the receiver). If the almanac information is unknown to the receiver, the receiver can search until a lock is obtained on one of the satellites. To obtain the lock, there must be an unobstructed line of sight from the receiver to the satellite. The receiver can then take the almanac from the satellites and determine the other satellites it should listen to (e.g., those above the horizon at the receiver's location at that time). When it detects the signal of each satellite, the receiver is able to identify the satellite by its distinctive C/a pattern. The receiver can determine the TOA information needed for position determination by, for example, cross-correlating a C/a code replica generated by the receiver with the C/a codes in the received satellite signals. The TOA information from the four satellites provides sufficient information to determine the position of the receiver.

Example overview of Low energy GNSS positioning techniques

One possible drawback of many GNSS receivers is that a large amount of power is required to search for and acquire signals from GNSS satellites, obtain an almanac, determine which satellites in the constellation to listen to, acquire a plurality of satellite signals, and process the acquired signals to determine the position of the receiver. For example, starting from a cold start (where the receiver clock has a large time offset and the latest almanac received from the satellites has expired), the receiver may take tens of minutes to get the satellites in view and obtain a good position estimate, which may require a large amount of energy. Maintaining locks on the satellite will also use energy. For applications where the receiver is connected to an external power source (e.g., a 120 volt wall outlet), this energy use may not be an issue. However, for receivers powered by small batteries, this energy usage may quickly drain the battery and cause the receiver to power down (requiring replacement or recharging of the battery) after a relatively short period of time. In many commercial applications, it may be disadvantageous to have to regularly replace or recharge the GNSS receiver battery, for example, where the position of many objects (each with a separate receiver) is being tracked. Accordingly, there is a need for satellite navigation systems and methods that provide for the location of a movable object while reducing or minimizing energy consumption.

The following provides a high-level, illustrative description of example low-energy GNSS positioning techniques. In this example, the mobile station is attached to, on, or in a movable object. The mobile station can be powered by a battery. Fixed base stations are located in known, generally fixed locations and are typically powered by a non-battery power source (e.g., a 120 volt wall outlet). The fixed base station enables the mobile station to obtain an accurate GNSS positioning (fix) faster and with lower average battery power. The mobile station has a rough idea of its position at any given time (possibly by dead reckoning based on the last known position of the mobile station, but possibly by some other positioning technique such as measurement of Received Signal Strength Indicator (RSSI) from RF access points, optical identification of optical beacons, etc.). As the mobile station moves, the base station will generally be close enough to the mobile station that a reliable bi-directional RF link can be established between the base station and the mobile station most of the time so that the mobile station and the base station can exchange information. In other examples, an optical communication link (e.g., infrared) may additionally or alternatively be created.

The base station has an RF antenna, GNSS processing capability, etc. to track all (or substantially all) of the GNSS satellites within view of the mobile station's position. When the mobile station determines that it needs an accurate GNSS positioning, the mobile station and base station are able to perform the following actions in this example operating scenario.

1. The mobile station sends a message to the base station informing the base station of the mobile station's best guess or estimate of its current position.

2. By receiving clock timing information from the base station, the mobile station synchronizes its local clock to the base station clock. The clock of the base station can be kept synchronized with the GNSS time used by the GNSS satellites.

3. The base station calculates which GNSS satellites are able to provide the best position fix (e.g., precise position) for the mobile station, and when each broadcast of these satellites will next be at the code boundary of the mobile station's position. The base station may also calculate some additional parameters to help the mobile station quickly acquire the satellites, such as doppler corrections for low-bearing satellites, such as modified correlator coefficients of a receiver in the mobile station. The base station can use a coarse acquisition C/a code or an encrypted precision p (y) code (for improving position accuracy without using a carrier phase method). The current state of the encryption (W) code of each selected satellite can be used in some embodiments.

4. Then, the base station transmits the information calculated in the precise action to the mobile station. As an optional implementation optimization, a clock update can be performed to improve the mobile station's estimation of its clock drift.

5. Using GNSS receiver baseband processing techniques, the mobile station runs its GNSS receiver at the correct time window using information from previous actions to acquire code phase transitions from satellites in view.

6. The mobile station then sends the minimally processed measurements to the base station.

7. The base station performs navigation equation processing and sends an update of the mobile station's true position to the mobile station. Since the base station is fixed, the moving position is automatically differentially corrected with respect to the base station. Thus, low-energy GNSS positioning techniques can be beneficial for automatically correcting atmospheric errors, which is a major source of error in GNSS positioning accuracy.

By offloading much of the GNSS processing from the mobile station to the base station, the energy usage of the mobile station is significantly reduced. The mobile station may wake up and retrieve satellite data at the right time (as determined by the base station), transmit the data to the base station (for further processing), and then go back to sleep after it receives its precise location from the base station. All this also serves to reduce the energy consumption of the mobile station.

Example pseudolite

Existing devices, known as pseudolites (for pseudo-satellites), transmit (to varying degrees) signals that mimic the structure of GNSS signals, so a properly equipped GNSS receiver is able to maintain position fix by receiving GNSS signals from pseudolites when there are less than a minimum number of GNSS satellites in view, including the case where there are no satellites in view. Pseudolites can be fixed in place to establish, at least in part, a ground-based positioning network. The GNSS receiver can be configured to receive signals from one or more pseudolites and/or one or more GNSS satellites to determine its position. One market for pseudolites is mining, because GNSS RF signals cannot penetrate mines. Pseudolites can be placed in urban canyons, retail shopping centers, warehouses, indoor environments (where GNSS signals are blocked or weakened), and the like, to allow position determination of objects in those spaces. In practice, pseudolites are almost always fixed in place.

Existing pseudolites transmit at widely separated frequencies, from the GPS 1560MHz to 1590MHz (L1) and 1215MHz to 1240MHz (L1) RF carrier frequencies, such as in the unlicensed 900MHz to 928MHz frequency band. This typically requires that the pseudolite compatible receiver include a 900MHz antenna and receiver analog front end in addition to the L1 (and/or L2) antenna and analog front end, which substantially increases the size and cost of the pseudolite compatible receiver as compared to other equivalent GPS receivers without pseudolite capability.

However, in the united states (according to the Federal Communications Commission (FCC) guidelines) and in some other countries, unlicensed transmitters operating in the frequency range of 1626.5MHz to 1645.5MHz are permitted. This frequency range is close enough to the GPS L1 frequency that single antenna and analog receiver operation over the entire frequency range (e.g., 1560MHz to 1590MHz and 1626.5MHz to 1645.5MHz) is feasible without sacrificing significant performance compared to other equivalent receiver designs that operate only in the GPS L1 frequency range. Thus, the pseudolites may broadcast signals in the frequency range of 1626.5MHz to 1645.5MHz (having a GNSS signal structure or a GNSS-like signal structure) to GNSS receivers operating in the frequency ranges of 1560MHz to 1590MHz and 1626.5MHz to 1645.5MHz, which are capable of receiving both orbiting GNSS satellite signals and terrestrial pseudolite signals. The receiver is capable of position determination using satellite signals and/or pseudolite signals, which advantageously allows the receiver to determine its position even when fewer (or no) desired GNSS satellites are visible to the receiver.

The transmit power allowed by a licensing agency (e.g., the FCC) in the 1626.5MHz to 1645.5MHz band is generally much less than that allowed in the 900MHz to 928MHz band, so these 1626.5MHz to 1645.5MHz pseudolites may typically not have pseudolites in the 900MHz to 928MHz range. But for some applications an achievable range with a frequency band of 1626.5MHz to 1645.5MHz may be sufficient and cost and size reduction of the mobile station may be commercially advantageous. If the 1626.5MHz to 1645.5MHz pseudolite is not continuously transmitting, it is allowed to generate a field strength of 500 μ V/m at a distance of 3 meters in the United states or-41 dBm Effective Isotropic Radiated Power (EIRP) within a 1MHz bandwidth according to 47 C.F.R.15.209. If the desired pseudolite receives a power of-121 dBm at the mobile station, which is equivalent to a very strong signal for a GNSS receiver, the pseudolite's free-space range is about (-41 dBm- (-121dBm))/2 ═ 40dB (3 meters) or 300 meters.

In contrast to conventional pseudolites, which typically always transmit, when combined with the low-energy GNSS system architecture described herein, it becomes possible for a 1626.5MHz to 1645.5MHz pseudolite to transmit when needed (e.g., under control of a base station processing element, which knows when a mobile station will listen to the pseudolite). Various embodiments of this "only on demand" mode may have advantages, such as: due to FCC regulations applicable to unlicensed transmitters in the 1626.5MHz to 1645.5MHz frequency band, the transmission power and range of the pseudolite can be increased if it is only intermittently operated (so the average transmission power of the pseudolite is in compliance with regulations even if the peak transmission power of the pseudolite exceeds the regulations for a sufficiently short period of time). For example, if the pseudolite is configured to transmit no more than once every ten seconds, the allowable field strength in the united states increases to 12,500 μ V/m at a distance of 3 meters, providing an enhancement in the 25-fold range, according to 47c.f.r.15.231 (e). In some such embodiments, the average power consumption of the pseudolite may be greatly reduced, making it easier for the pseudolite to be powered by solar energy, wind energy, or some other non-mains power source.

Example applications of Low energy GNSS techniques

The disclosed system and method for low energy GNSS positioning of movable objects can be used in many applications, particularly in any application where the mobile station has a limited energy source (e.g., a battery). Examples of applications include retail environments (e.g., tracking the location of shopping carts), warehouse environments (e.g., tracking warehouse carts, inventory collection robots, etc.), transportation hub environments (e.g., tracking baggage carts in airports), medical facility environments (e.g., tracking medical carts or medical devices), etc. Low energy GNSS techniques can be used for object location applications where the location of any type of movable tangible object is to be determined (e.g., by attaching a mobile station to the object). The movable object can be any type of movable inanimate object (e.g., a cart, valuables, inventory, portable items, etc.) or a movable animate object (e.g., a person, pet, animal, livestock, etc.).

By using one or more pseudolites transmitting in an unlicensed band around the L1 frequency (e.g., 1626.5 MHz-1645.5 MHz), the disclosed systems and methods may be able to provide accurate positioning in an indoor environment or in an environment where orbiting satellites are frequently blocked from view.

Example Low energy GNSS Mobile System settings

FIG. 1 illustrates an example system set-up diagram relating to a low-energy GNSS mobile system. The environment may include an indoor space and an outdoor space. Line 116 shows the boundary separating the indoor space from the outdoor space. Receiving signals from GNSS satellites useful for position estimation requires a line of sight that is unobstructed between the GNSS receiver and the satellites. Thus, in order to determine the position of an object indoors, information may need to be included in addition to signals from GNSS satellites, which are typically obstructed or weakened indoors. As described herein, one or more pseudolites can be used in indoor space or where GNSS satellites are routinely obstructed.

A Base Station (BS)120 with a GNSS antenna 124 is installed as part of the setup, typically together with a base station located indoors to protect it from weather elements. The indoor installation also provides convenient access to energy sources, such as 120V main power outlets. Therefore, the energy consumption of the base station is generally not a constraint on the system. The GNSS antenna 124 is typically mounted in a position that has good line-of-sight visibility to the plurality of GNSS satellites 104 in the GNSS constellation around the earth. For example, installation of a base station and its GNSS antenna generally positions the antenna so that the antenna has an unobstructed line of sight to all or nearly all (e.g., four or more) of the GNSS satellites on the horizon. A Central Control Unit (CCU)128 may be operably connected to base stations 120 and may be capable of providing processing, data storage, and network access services.

The low energy GNSS mobile system has one or more mobile stations 160, the mobile stations 160 being movable or configured to be attached to or included in or on a movable object. As described herein, the mobile station 160 can be provided in the wheels of a human-propelled movable cart (e.g., a shopping cart) or in other portions of the cart (e.g., the frame or handlebars), or in or on inventory to be tracked, attached to personnel or animals, or the like. Tracking the position of the mobile station or the position of an object to which the mobile station is attached is a primary function of the GNSS mobile system. The mobile station 160 includes a GNSS receiver for receiving GNSS signals. Such GNSS signals may be transmitted by GNSS satellites 104 or pseudolites 180. The mobile station also includes a radio link for bi-directional communication with the base station. The mobile station may also include other devices or components associated with position estimation. For example, a wireless transceiver may be used to establish communication with the wireless access point 108. The location of the mobile station may be estimated through such communication (e.g., via Received Signal Strength Indicator (RSSI) measurements). One or more electrical, electromagnetic, magnetic, or optical sensors can provide location information from signals emitted by one or more beacons 112. For example, the mobile station 160 may perform a dead reckoning procedure to estimate its position. In contrast to base stations, mobile stations typically have a limited energy source, such as a battery (replaceable or rechargeable).

As described above, estimating a position using GNSS satellite signals requires an unobstructed line of sight from at least three or four GNSS satellites to a GNSS receiver. This requirement poses a challenge for indoor GNSS receivers. As will be described in connection with fig. 8, one or more pseudolites 180 are capable of providing GNSS signals (or GNSS-like signals) for use in position estimation. Thus, pseudolites are typically located indoors. Pseudolites are also useful outdoors, for example, in urban environments where high-rise buildings, passing vehicles, etc. can block the line of sight of GNSS satellites.

The optional network connection with the base station can provide information beneficial to low energy GNSS mobile systems. For example, the base station 160 may obtain more frequent or timely updates of the timing data for various GNSS satellites over the network. The updated timing data allows the base station to synchronize its clock with the satellite clock with better accuracy. The network connection allows the base station to obtain information about weather conditions, updated ionospheric models, GNSS ephemeris or almanac. The base station may use such information to provide better data to the mobile station to assist in the location estimation of the mobile station. The network connection may be used to provide remote control functions and/or monitoring functions. For example, a remote server may be connected to multiple base stations via a network to monitor the status of the base stations and/or associated mobile stations to perform data aggregation, data mining, or other data analysis of mobile station location information. CCU 128 may be connected to base station 160 via a network. In some embodiments, the functionality of the CCU is included in the base station, and vice versa.

Example tracking or containment applications

In fig. 1, the opening 136 shows a space through which an object can move from an indoor space to an outdoor space, and vice versa. The boundary between the interior/exterior of the chamber may include any number of openings. The entrance/exit of the building is an example of an opening 136. Line 132 shows the exit field where the movement of the mobile station can be detected through opening 136. The exit field may be established by, for example, an access point 108 or beacon 112 located near the opening 136, a Very Low Frequency (VLF) signal line (e.g., a signal having a frequency in the unlicensed RF band below approximately 9 kHz), an Electronic Article Surveillance (EAS) system, a Radio Frequency Identification (RFID) system, an ultrasonic transmitter, etc. The exit field may be in the shape of a line, the shape of the antenna reception pattern, or some other shape. The mobile station 160 can include a sensor that senses the exit field and takes appropriate action in response to the sensing. For example, a mobile station sensing exit field 132 can determine that its current position is at opening 136. The mobile station may use the position information to update or reset a dead reckoning system that the mobile station estimates its position.

In the illustration of fig. 1, the area within which the mobile station needs to be tracked is surrounded by a tracking area boundary 144. Since the tracking area may be beyond the communication range between the base station and the mobile station, one or more link repeaters 140 may be used to relay messages between the base station and the mobile station. The link repeater is further described below in conjunction with fig. 7B.

In some applications and as shown in fig. 1, the movable object may be located in or tracked within a confinement region surrounded by confinement boundary 148, a free-roaming region within warning region boundary 152, and a warning region 156 between warning region boundary 152 and confinement region boundary 148. The movable object may be allowed to move freely within the free-roaming region, but if the object moves within the warning region, it may be warned that it is approaching the restricted area boundary 148. Different corrective actions may be taken depending on where the object is located (e.g., no action in a free-roaming area, warning in a warning area, and restricting action when an object passes a restrictive boundary (on the way out)). If the movable object moves from outside to inside the restricted area (e.g., the object returns to a free-roaming area), additional or different actions may be taken.

For example, in a retail store application, an indoor area may represent a store. The mobile station may be mounted in or on a shopping cart. The free-roaming area may include a store and a parking lot associated with the store. The shopping cart can move freely within the free roaming area. The restricted area boundary 148 may include a perimeter outside of the parking lot. The shopping cart may be prevented from leaving the confined area, for example, by a braking mechanism that prevents movement of the cart after the cart leaves the confined area (e.g., by locking or inhibiting rotation of the cart wheels). The warning area can represent an area between the free roaming area and the restricted area. The shopping cart may provide a warning (e.g., an audio signal or a visual signal) upon entering the warning area to warn a person pushing the shopping cart that the cart is approaching a location where the shopping cart will be braked. As another example, in livestock tracking applications, an electronic device (included with or separate from the mobile station) may be attached to the animal to be tracked or restrained. The device may emit a sound to alert the animal when the animal walks to the armed zone. When the animal walks beyond the restricted area, the device may apply a light stimulus to train the animal not to leave the restricted area. The boundaries of the bounding (or warning) area can be different for different movable objects moving around the tracking area. The boundaries of the restricted (or warning) area can be dynamic and, for example, based on the elements or behavior of the movable object (e.g., a sick animal may be included in an area different from a healthy animal). In some embodiments, the base station determines (or receives) an update of the limit (or warning) boundary and communicates the update to the appropriate mobile station (or mobile stations) over the RF link.

Example Low energy GNSS Mobile System implementation

FIG. 2A illustrates an example embodiment of a low energy GNSS mobile system. For illustrative purposes, one GNSS satellite 104, one base station 120, and one mobile station 160 are shown, but this is not a limitation. The GNSS satellites broadcast their GNSS data. Both the base station and the mobile station may receive GNSS satellite broadcast signals via their respective antennas 124 and 264. The base station and mobile station also include wireless links (e.g., RF transceivers 236, 276 for the base station and mobile station, respectively) to communicate with each other. To reduce the energy consumption of the mobile station, the mobile station may transmit at a lower power level on the radio link than the base station. The base station may periodically transmit a ready signal to indicate its availability. In the united states, the base-mobile radio link is capable of using an unlicensed RF band (e.g., a band in which transmissions do not require a license from a radio communications authority), such as 900MHz to 928MHz, 2.400GHz to 2.483GHz, or 5.8GHz (e.g., a band from 5.725GHz to 5.875 GHz). The unlicensed RF bands may include bands in industrial, scientific, and medical (ISM) RF bands (e.g., B-mode bands) or non-cellular RF bands (e.g., bands outside of those licensed for RF cellular communications). Unlicensed ISM bands can include bands below 1GHz (in different countries or regions), such as 315MHz to 316MHz, 426MHz to 430MHz, 430MHz to 432MHz, 433.05MHz to 434.79MHz, 779MHz to 787MHz, 769MHz to 935MHz, and 863MHz to 870 MHz.

In addition to the antenna 124, the base station 120 is shown to include a GNSS receiver 228, a processor and data storage unit 232, and a radio link 236. A GNSS receiver receives electromagnetic signals from GNSS satellites and converts information embedded in or associated with the signals into a digital data format for processing and storage by a processor and a data storage unit. The processor calculates various data to supply to the mobile station. Such data is useful for a mobile station to estimate its position using GNSS signals with low power consumption, which preserve battery life. The processor generates a message that communicates with the mobile station over the radio link. The processor also processes messages received from the mobile station or CCU 128. The base station 120 can be powered by a mains power supply.

The illustrated mobile station 160 includes an antenna 264, a GNSS receiver 268, a processor and data storage unit 272, a radio link 276, a power supply 296, and a position sensor 280. The mobile station receives GNSS signals via antenna 264. A GNSS receiver receives electromagnetic signals from GNSS satellites and converts information embedded in or associated with the signals into a digital data format suitable for processing and storage by a processor and a data storage unit. The processor calculates various data to supply to the base station. These data are useful for the base station in estimating the position of the mobile station. The processor generates a message that communicates with the base station over the radio link. The processor also processes messages received from the base station.

The position sensor 280 can provide non-GNSS position estimates, e.g., a position sensor that produces measurements that do not include measurements of GNSS satellite signals. One or more non-GNSS sensors (e.g., accelerometers, magnetometers, Inertial Measurement Units (IMUs), gyroscopes, magnetic heading sensors, compasses, wheel rotation sensors, pedometers, gait sensors, optical sensors, VLF sensors, EAS sensors, RFID sensors, RF sensors, ultrasonic sensors, etc.) can be included in the mobile station and used, at least in part, by the position sensors to estimate position (e.g., via a dead reckoning algorithm). In some cases, the location sensor 280 may be capable of determining location directly from measurements (e.g., a VLF sensor sensing VLF groundwire at a particular location), while in other cases, the location sensor may use other components or other sensors for location determination (e.g., a pedometer used with a compass and dead reckoning algorithms). The pedometer or gait sensor can comprise an accelerometer or IMU. For example, the position sensor 280 can be a dead reckoning sensor that includes a magnetic sensor (e.g., a compass) to provide a heading of the mobile station. The dead reckoning sensors can also include wheel rotation sensors to provide an estimated distance traveled by a mobile station attached to an object having wheels. A combination of magnetic heading and range estimation can be used in a dead reckoning algorithm to provide a position estimate for the mobile station. A sensor measuring a Received Signal Strength Indicator (RSSI) can provide an estimated distance between the mobile station and the wireless access point 108. The optical sensors or RF sensors can provide a location estimate based on signals emitted by one or more optical beacons, ultrasound beacons, or RF beacons 112 that are located throughout the tracking area 144 or at certain locations within the tracking area 144. For example, an ultrasonic sensor or RF sensor can measure time-of-flight from signals received from an ultrasonic beacon or RF beacon, respectively, which can be converted to a distance from the beacon based on speed of sound or speed of light, respectively. Multiple beacons can be used to triangulate a non-GNSS position of a mobile station.

As an example of such a non-GNSS sensor, if the mobile station is restricted (for whatever reason) to passing through a portal at a known location (e.g., opening 136 shown in fig. 1), an RF sensor on the mobile station may detect short-range signals from an RF transmitter or beacon mounted on or near opening 136. The RF signal can include the position of the opening, providing a good position estimate for the mobile station (e.g., for resetting the dead reckoning position estimate). The RF sensor can be configured for Near Field Communication (NFC), Bluetooth Low Energy (BLE), IEEE 802.15, or any other type of wireless networking protocol.

The power supply 296 of the mobile station 160 can include a battery (e.g., replaceable or rechargeable), a capacitor (e.g., a high energy density capacitor such as a supercapacitor), or any other non-mains energy source suitable for use with a movable object. Combinations of the foregoing may be used. Such power supplies 296 typically have a limited energy reserve (e.g., amount of battery capacity). As discussed, a drawback of many conventional GNSS receivers is their relatively high power requirements, resulting in a relatively short life of the power supply 296. Embodiments of the low energy GNSS system described herein can reduce power consumption in the mobile station, resulting in a substantially longer lifetime of the power supply 296.

FIG. 2B illustrates another example embodiment of a low energy GNSS mobile system. For illustrative purposes, one GNSS satellite 104, one base station 120, and one mobile station 160 are shown, but not by way of limitation. The GNSS satellites broadcast their GNSS data. Both the base station and the mobile station are capable of receiving GNSS satellite broadcast signals through their respective antennas and Low Noise Amplifier (LNA) units 244, 284. Both the base station and the mobile station also include wireless links (e.g., transceivers 236, 276 for the base station and mobile station, respectively) to communicate with each other.

In addition to the antenna and LNA unit 244, the illustrated base station 120 includes a GNSS receiver divided into an analog portion 248A and a digital portion 248B, a processor and data storage unit 232, a radio link 236, and a precision clock support component 252. The LNA is capable of amplifying low power GNSS signals with only a slight reduction in signal-to-noise ratio (SNR). The precision clock support component provides the functionality to synchronize the base station clock to the GNSS satellite clock and to help synchronize the mobile station clock to the base station clock. Since the base station is (typically) not energy limited, it can continuously receive GNSS satellite signals and keep its clock synchronized with the GNSS satellite clock. The energy-constrained mobile station is able to synchronize its clock to the base station clock on an as-needed basis. By two pairwise synchronizations of clocks, the mobile station clock can be synchronized (indirectly) to the GNSS satellite clock, enabling the mobile station to take signals from GNSS satellites with lower energy consumption than unsynchronized clocks.

The illustrated mobile station 160 includes an antenna and LNA unit 284, a GNSS receiver divided into an analog portion 288A and a digital portion 288B, a processor and data storage unit 272, a radio link 276, a dead reckoning sensor 280A, an alternative precision position sensor 280B, and a precision clock support 292. The mobile station receives GNSS signals through an antenna and LNA unit 284.

A GNSS receiver receives electromagnetic signals from GNSS satellites and converts information embedded in or associated with the signals into a digital data format for processing and storage by a processor and a data storage unit. Analog GNSS signals are typically sampled and digitized by an analog-to-digital converter (ADC) at the interface between the analog and digital portions of the receiver. An advantage of a low power GNSS receiver system in accordance with embodiments of the present disclosure is that the processing required for the digital portion of the GNSS receiver and the resulting reduction in power consumption is reduced. For example (and as further described herein), the mobile station can begin sampling at or near the code boundary using timing data on the code boundary in the GNSS signals received from the base station, and sample a shorter block of GNSS signals than the mobile station if the start of sampling is independent of the code boundary. As a result, the circuitry in the digital portion 288B, such as Digital Signal Processing (DSP) filters and correlators, can be smaller and more energy efficient than conventional GNSS receivers.

The position sensor is capable of providing a non-GNSS position estimate. For purposes of illustration, dead reckoning sensor 280A is separate from the alternative fine positioning sensor 280B. The dead reckoning sensor may be an inertial system including a combination of magnetic sensors, rotation sensors or gyroscopes, accelerometers, and a microcontroller to convert direction and distance data into position data. Alternative precision position sensors may include other position sensors, including those described above in connection with FIG. 2A. In some embodiments, the inertial system may be reset and have its accumulated error cleared by taking an estimated position estimated by a non-GNSS sensor (e.g., an RF sensor to detect short range signals from transmitters at a portal of known location) or from the GNSS system as a new initial position. Thus, position drift errors in the dead reckoning estimates may be reduced so that the mobile station 160 continuously has a reasonably accurate estimate of its position.

In some embodiments, Two-Way communication between a mobile station and a base station can use the communication protocol described in U.S. patent No.8,463,540 for Two-Way communication system for Tracking Locations and states of wheeled vehicles (Two-Way communication systems for Tracking Locations and states of wheelvehicles), which is incorporated herein by reference in its entirety. In some embodiments, the bidirectional communication between the mobile station and the base station may be in an unlicensed frequency band in the united states, for example, 900MHz to 928MHz, 2.4GHz to 2.483GHz, or 5.850GHz to 5.925 GHz. In some embodiments, the mobile station is capable of implementing the Navigation techniques (e.g., dead reckoning) described in U.S. patent No.8,046,160, "Navigation Systems and methods for wheeled Objects," which is incorporated herein by reference in its entirety. The two-way communication protocols and dead reckoning techniques described in these patents may be particularly advantageous for low energy GNSS system embodiments in which the mobile station is attached to or included in a human-propelled wheeled cart (e.g., in the frame or wheels of a shopping cart). The mobile station of some such wheeled cart embodiments may utilize a Power source including a wheel Power generator, such as described in U.S. patent No.8,820,447, "Power Generation Systems and methods for wheeled Objects" which is incorporated herein by reference in its entirety.

Example Low energy GNSS Mobile System processing and communication flows

FIG. 3 illustrates an example processing function and communication function provided for a mobile station and performed by a base station in a low energy GNSS mobile system. The functions performed by the mobile station appear in the left hand box. The functions performed by the base station appear in the right hand box.

In block 301, the mobile station wakes up at a time specified in its sleep parameters, or when conditions specified in its sleep parameters are met. The sleep parameters may be stored in memory 272. The clock oscillator in the mobile station may require a warm-up time to settle. Thus, the mobile station may monitor an attribute of the oscillator, such as short term frequency drift, to determine whether the oscillator is stable within a predetermined range. The mobile station estimates its current position, block 302. Such an estimate may be based on output from a dead reckoning sensor and/or another non-GNSS position sensor as described in connection with fig. 2A and 2B. Such an estimate may include a current estimated position of the mobile station and, optionally, an uncertainty metric associated with the estimated position. For example, the position and uncertainty estimate may be represented as a series of positions. In case the non-GNSS sensor based position estimation does not depend on the stability of the clock oscillator, the estimation may be performed during warm-up of the oscillator. After the clock oscillator becomes stable, the mobile station transmits its position estimate and its local clock value to the base station via radio link 276. The local clock value can be captured at a fixed time relative to the start of the transmission and saved to the mobile station's local memory, as shown in block 317. Clock synchronization is described further below in conjunction with fig. 7A and 7B.

The base station receives a message from the mobile station via radio link 236, block 303. The base station updates its model of the mobile station clock based at least in part on the local clock value in the message from the mobile station. The base station calculates a clock correction value for the mobile station and transmits the value to the mobile station, as shown in block 304. At block 306, the base station estimates which GNSS satellites are most likely in view of the mobile station. Such estimation can be based at least in part on an estimated current position of the mobile station that is included in a message from the mobile station.

Such estimation of the visible satellites can include additional considerations, such as reducing or minimizing dilution of precision (DOP, e.g., geometric dilution of precision (GDOP)) in the direction of interest. The base station also calculates the code phase and, optionally, the doppler shift associated with each satellite included in the information transmitted to the mobile station. This information (e.g., satellite acquisition information) transmitted from the base station to the mobile station includes at least a set of satellites for which the mobile station is able to attempt to acquire signals and a code phase on the C/a code and/or W code associated with each satellite (e.g., the time of broadcast by each satellite in the set will be next at a code boundary of the location of the mobile station) in block 307. The set of satellites can be provided as a list of visible satellites and, in some cases, as an ordered list in which more desirable satellites (for accurate position estimation) are ordered higher than less desirable satellites. Queuing is further described below.

While the position can be determined based on signals from as few as four GNSS satellites (assuming the mobile clock is not synchronized with the satellite clock) and as few as three GNSS satellites (assuming the mobile clock is sufficiently synchronized with the satellite clock), the group can include more than three or four satellites to provide an alternative in situations where not all of the minimum number of satellites are visible to the mobile station or produce a signal at the mobile station with a high received SNR. The information may also include a doppler shift associated with each satellite in the set. For a mobile station moving at a velocity less than the velocity of a GNSS satellite, the doppler shift is substantially independent of the individual mobile station. In contrast, the doppler shift depends on the location of a single satellite and is greater for satellites near the horizon. The information sent to the mobile station may additionally include initialization parameters for the mobile station GNSS receiver, such as parameters for a frequency locked loop or a Phase Locked Loop (PLL).

The satellites in the set may be queued according to one or more ordering criteria. For example, satellite signals that are closely aligned along the direction of movement of the mobile station may provide better resolution for position estimation. Thus, for a mobile station moving over flat terrain, satellites near the horizon may provide better resolution signals for terrestrial position estimation. However, signals from satellites near the horizon reach the mobile station over longer ionospheric paths and may be subject to greater error than signals from high-altitude satellites. Signals from satellites near the horizon also tend to have larger doppler shifts. Thus, queuing the satellites involves balancing the reactionary factors such as those discussed above. Queuing may also depend on the availability of additional information such as updated ionospheric models.

The satellite acquisition information from the base station may also include selection information useful for the mobile station to determine from which GNSS satellite in the set to derive GNSS signals. The selection information may include an order of satellites to be retrieved, where the order may be based on contingency. For example, if no contingency occurs, a first capture order is used, and if a contingency occurs, a second capture order is used. By way of example, such selection information can include two satellites that are located in close proximity, such that if the mobile station is unable to obtain a good quality signal from one satellite, the mobile station can skip acquiring signals from the other satellite. To illustrate, both satellites #4 and #5 in the set may be located near the mountain from the mobile station's perspective, such that if the mobile station is unable to obtain a good quality signal from satellite #4, the mobile station should skip acquiring the signal from satellite #5 because the signal may also be blocked by the mountain. As another example, satellite position information may be used to specify a primary satellite and a back-up satellite that are both in the direction of interest. If the mobile station is unable to obtain a good signal from the primary satellite, the mobile station can attempt to obtain a signal from the corresponding backup satellite. As an illustration, it is assumed that the satellite #3 is located in the moving direction of the mobile station. Satellite #7 is located in the opposite direction, 180 ° from satellite # 3. The signals from these two satellites may be able to provide good resolution in the position estimate in the direction of movement. Thus, if the mobile station is unable to get a good signal from satellite #3, then the signal from satellite #7 in the group may be better than the signals from satellites #5 and #6 because of its higher queue, the mobile station will normally try to get signals from satellites #5 and #6 before satellite # 7. A description of the directions of interest and additional example factors for queuing satellites is discussed below in conjunction with fig. 6A and 6B.

The mobile station receives clock correction information from the base station, block 305. The mobile station then corrects its clock, for example by adjusting a PLL to adjust the clock rate of the mobile station. After the clock correction, the clock of the mobile station is synchronized with the clock of the base station. Since the base station's clock can and may be synchronized to the GNSS satellite clock, the mobile station clock is also synchronized to the GNSS satellite clock after clock correction.

At block 308, the mobile station receives a set of satellites and associated acquisition information from a base station. Using this information from the base station, the mobile station is able to acquire GNSS signals. With a clock synchronized to the GNSS satellite clock and code phase timing information provided by the base station, the mobile station can begin acquiring GNSS satellite signals at a precise time, such as at or near code phase transitions). Thus, the mobile station can start acquisition at the correct time and acquire only a small block of signals, rather than potentially searching for code phase transitions multiple times to obtain a large block of GNSS signals, thereby saving a significant amount of energy. For example, a 10 μ s long block of signals (e.g., 2,000 digital samples sampled at 200 MHz) may be sufficient. In other cases, the mobile station may search for GNSS signals for a time period in a range of less than 1 μ s, 1 μ s to 100 μ s, 100 μ s to 1000 μ s, or more.

At block 309, the digitized baseband raw data is transferred from the GNSS receiver to the processor 272. Depending on the implementation of the analog part of the receiver, this raw data may be in-phase only (I) or in-phase and quadrature simultaneously (Q).

The processor pre-processes the digitized baseband raw data, block 310, primarily in obtaining chip transition times that are sent to the base station, block 311. To estimate the chip transition time from a GNSS signal, the mobile station can start despreading the acquired signal from the code used by the first satellite in the sorted list, continue descending from the list, and stop after obtaining a good signal from the minimum number of satellites needed for positioning. As explained above, the minimum number of satellites is three or four depending on whether the mobile station's clock is synchronized with the satellite clock. The reference spreading codes associated with each satellite are stored in the mobile station, for example in data storage 272. The despread signal, e.g., the output of the correlator, includes attributes indicative of the quality of the corresponding received signal, e.g., power, width of the peak in the correlator output (e.g., 3-dB), and SNR. The mobile station is able to calculate these quality indicators with low power consumption.

The determination of the quality of the received signal may be based in part on one or more properties associated with the despread signal. The criteria for high quality signals may depend on many factors, such as the performance of the mobile station's GNSS receiver, the availability of external assistance information (e.g., the latest ionospheric model), the desired or required level of accuracy of the position estimate, the source and nature of GNSS signal distortion (e.g., wideband and narrowband interference), and so forth. In some cases, in some operational scenarios, the signal quality that is considered good for an embodiment may not be sufficient for another embodiment in a different situation, in a different operational scenario. Thus, the following examples of quality signals are not limiting.

For example, a peak width of 3-dB in the correlator output may be considered good if it is a fraction of the chip time, such as 1/4, 1/2, or 3/4 of the chip time. For example, half of the chip time for a 10.23MHz P (Y) chip rate translates to less than 49 nanoseconds. Different fractions of different chip rates (e.g., 3/4) translate into different widths. As another example, a conventional GNSS receiver in acquisition mode (e.g., taking GNSS satellite signals from a cold start) may require higher received signal power (e.g., up to 4 to 16dB) than a receiver in tracking mode. For example, the nominal GPS power on the L1C/a code received at the earth's surface 5 degrees from the horizon is about-129 dBm at the input of the LNA (assuming isotropic antenna and average no-rain weather). The nominal GPS power on the p (y) code received under equivalent conditions is-132 dBm, about 3dB lower. In acquisition and tracking mode, the specified performance levels of received signal strength measured by a conventional GPS L1 receiver at the LNA input (e.g., at or above a minimum level at which signal quality can be considered good) may be-150 ± 3dBm and-160 ± 3dBm, respectively, leaving a margin for degradation conditions where the moisture content in the atmosphere is high. One or more of the factors described above may alter these specified performance levels. Embodiments of the mobile station GNSS receiver may function similarly to conventional GNSS receivers in tracking mode when not operating in autonomous mode. However, some applications may impose design goals on embodiments of GNSS receivers. For example, some retail store shopping carts and livestock tracking applications described herein may not allow for good antenna designs (e.g., isotropic), such as 0dBic gain, near the horizon of the mobile station. Base stations that are not significantly limited by factors such as size, shape, and weight can be designed with good non-moving antennas. However, for mobile station antennas that may need to be placed, for example, in the handle of a shopping cart or in a collar placed around the neck of an animal, a compromise in performance may be required. Thus, good received signal strength for a GNSS receiver in the non-autonomous mode may be closer to a conventional GNSS receiver in the acquisition mode, e.g., -150 + -3 dBm at the LNA input.

As discussed herein, clock synchronization between the mobile station and the base station may be sufficient to enable a minimum of three GNSS satellites to be used for position estimation. Acquiring GNSS signals from three satellites instead of four may reduce power consumption. However, the clock synchronization may be poor enough that the resulting position estimate (from three satellites) is not particularly accurate (although it may be available in some cases where accuracy is less important). Thus, in many commercial scenarios, the minimum number of satellites acquired by a mobile station is often four.

The particular satellite despread by the mobile station may or may not be the first three or the first four from the sorted list of base stations. For example, a line of sight to one of the preceding satellites may be temporarily blocked by an object. In this case, the mobile station may not be able to obtain a good signal from this satellite. In this manner, the mobile station does not despread signals from more satellites than are necessary to determine the position of the mobile station, thereby reducing the energy consumption associated with GNSS position determination. Furthermore, since the list of satellites from the base station can be queued to some extent according to their visibility from the mobile station, traveling according to the queue in the list can minimize the number of satellites from which signals are despread by the mobile station, except for unexpected reasons such as temporary congestion.

The mobile station can also calculate the SNR for each satellite for which the mobile station is attempting to receive its signal. SNR is a quality indicator of the received signal and can be calculated with low power consumption. The mobile station may send the calculated SNR to the base station as part of a message, block 311. The mobile station is also able to verify that there is no code phase error, as shown in block 318. The code phase error may have different causes including clock synchronization errors, mobile station position estimation errors (block 302), GNSS signal propagation path errors, etc. If the mobile station detects a code phase error, the mobile station may take one or more corrective actions. For example, the mobile station may return to block 302 and repeat its process therefrom, which may correct the error (e.g., by resynchronizing the mobile station clock to the base station clock). The mobile station may increase the width of the search window to obtain peaks from the correlators, which may help to resolve the error if it is due to the error in the estimated position of the mobile station. The mobile station may determine that the signal from the satellite associated with the code phase error cannot (at this point) be successfully acquired and continue to pre-process the signal from another satellite on the acquisition list or take another action in response.

By using codes in GNSS signals with higher chip rates, the mobile station can fine tune its timing accuracy to an accuracy of, for example, a fraction (e.g., one quarter) of a chip. For example, the chip rate of the fine (P) code in the GPS system is 10 times the chip rate of the C/A code. The mobile station does not reference the fine (P) code because the fine (P) code is encrypted with the military key. However, to determine chip transitions in the navigation message, the mobile station can rely on the encryption key, a low frequency change in the encrypted (W) code, and cannot decrypt the encrypted p (y) code. The chip transitions can be located by shifting the digitized GNSS signal relative to the correlator window and locating the peak in the correlator output. By synchronizing to the (indirect) clock of the GNSS satellite clock, the mobile station according to the present disclosure is able to locate the correlator peak within a smaller shift range than conventional GNSS receiver/processors. For example, a shift window of ± 2 μ s may be sufficient, assuming that the clock synchronization error through the base-mobile RF link and the 4-sigma code phase tolerance level is normally distributed. Assuming that the chip spacing is short relative to the shift range (which is possible if p (y) is used), the shift range can be based primarily on the clock synchronization accuracy of the mobile station in acquiring the chip sequence including the chip conversions in baseband. For example, if the clock error is assumed to be normally distributed, several (e.g., 1, 2, 3, 4, or more) sigma shift windows are typically sufficient. The expected clock synchronization sigma is in the order of 0.5 x (1/RF link bit rate). Thus, in an embodiment where the RF link bit rate is about 1Mbps, the shift window may be about ± 2 μ β for the 4-sigma shift range. In other embodiments, the displacement rate can range from about 0.5 μ s to about 10 μ s, 10 μ s to 1000 μ s, or some other range.

As a result of the fine tuning of the timing accuracy of the mobile station, in some embodiments, the circuitry for the correlators in the digital portion of the GNSS receiver/processor in the mobile station is smaller and consumes less power than those in conventional GNSS receiver/processors. In a system that uses p (y) codes for timing, the message sent from the base station to the mobile station can include code phase information for the encrypted (W) code for each visible satellite, block 307.

The base station receives a message from the mobile station, block 312. Using the satellite signal conversion timing information in the message, the base station can compute the position of the mobile station by solving GNSS navigation equations (e.g., computing position/velocity/time (PVT) solutions)). The timing information may be sufficient for the mobile station to update the calculation of the location, in which case the base station moves to block 313. On the other hand, the timing information may become insufficient and the base station is unable to calculate an updated position of the mobile station. In this case, the process returns to block 306 and repeats from there. The sufficiency of the timing information may be determined from a confidence level with respect to a desired level of accuracy associated with the position estimate. The confidence level may in turn be based on the quality indicator sent by the mobile station. The desired level of accuracy may be different in different environments or applications. The uniformity of the estimates derived from the calculation of timing information associated with different satellites at the same message can also provide a measure of confidence level. For example, if the errors in the PVT solutions calculated for the signals of the majority of satellites included in the timing information message are close to each other, while the errors in the PVT solutions of the minority of satellites included in the timing information message are very different from all others (including, for example, being far from each other in the minority), the confidence level of the estimates from the majority of the constellation may be high, while the confidence level of the estimates from the minority of the constellation may be low. The confidence of the correlator peak can be indicated by quality indicators such as the sharpness of the peak (e.g., full width at half maximum), the SNR of a particular satellite at a particular time, and the like.

The base station can update its path record associated with the mobile station, block 313. The base station can also calculate updated sleep parameters or updated sleep areas for the mobile station. The base station then transmits the updated position to the mobile station. The base station can also transmit updated sleep parameters or updated sleep area information to the mobile station. In the case where the mobile station's movement or action is directed by or through the base station, the base station can calculate and transmit instructions to the mobile station to indicate its movement or action. The base station may also calculate and transmit data to assist the mobile station in adjusting its non-GNSS position sensors.

At block 314, after receiving the message from the base station, the mobile station updates its own position (based on the updated position received from the base station) and, optionally, adjusts or resets its position sensor, such as an inertial measurement system or a dead reckoning system. If the message also includes updated sleep parameters or updated sleep zone information, the mobile station can update its sleep parameters or be explicitly stated or derivable from information related to the sleep zone in the message. The mobile station may redirect its movement or action, if any, based on instructions from the base station. The mobile station can then transmit an Acknowledgement (ACK) message and place itself in sleep mode (based on the sleep parameters), as shown in block 315. The mobile station will then wake up and restart from block 301 according to its sleep parameters. The base station receives the ACK message from the mobile station and the process completes one cycle, block 316.

The base station or mobile station may determine the sleep parameter based on a number of considerations. For example, in a geofencing application (e.g., a shopping cart containment application or a livestock containment application described herein), the dormancy parameter may be based in part on a current distance or a predicted distance at a future time between the mobile station and a boundary or obstacle in a restricted area within the geofence or boundary 148. The dormancy parameter can account for dynamic geofences, where the boundaries of the geofence change over time or other parameters. The distance between two mobile stations may be a factor in determining the sleep parameters needed to avoid collisions. The sleep parameters may include explicit wake or sleep conditions or information that the mobile station can use to calculate the wake or sleep conditions. Sleep refers to an inactive state of the GNSS part of the mobile station. Other parts of the mobile station may remain active. For example, the processors and sensors may remain active while the GNSS component is in a sleep state to monitor an environment or state, calculate new wake-up conditions based on changing environments or states, and process dead reckoning data.

The functionality described with reference to fig. 3 is intended to illustrate, but not limit the scope of the present disclosure. In other examples, one or more of the processing blocks may be rearranged, combined, or deleted.

Example autonomous mode and standalone mode

The low energy GNSS mobile system is capable of implementing an autonomous mode for use when the mobile station is not in contact with the base station. A mobile station may lose contact with a base station for various reasons, such as temporary communication path blockage, temporary base station interruption, or the station being out of communication range. Low energy GNSS mobile systems can reduce this occurrence by employing redundant base stations or by optionally using the link repeater 140 described herein. In autonomous mode, the mobile station may compute its position from GNSS signals via conventional GNSS methods. In autonomous mode, the mobile station may use the cached ionospheric model to at least partially correct errors in the position determination. A mobile station in a low energy GNSS mobile system can reduce the energy consumption of autonomous mode by sacrificing the accuracy of the position estimate. For example, not maintaining the GNSS receiver for the (relatively long) time required to receive ionospheric grid corrections via space-based augmentation services (SBAS) can reduce energy, albeit possibly at the cost of accuracy. Acquiring pseudoranges from satellites includes acquiring chip conversions and performing position estimation. Multiple captured pseudoranges can improve the accuracy of the PVT solution. Therefore, acquiring fewer pseudoranges per satellite can also reduce energy, again possibly at the cost of accuracy.

Low energy GNSS mobile systems are also capable of implementing standalone mode. In this mode, the mobile station does not provide an initial position estimate to the base station (see, e.g., block 302 of fig. 3). The base station may perform the estimation at block 306 using its own position or the last calculated position of the mobile station as the initial position of the mobile station. This mode can be effective when the mobile station is not traveling far from the base station or between successive processing cycles. The frequency of the processing cycles may be adjusted to increase the effectiveness of the independent mode. This mode is useful when non-GNSS position sensors are not available on the mobile station.

Example Low energy GNSS Mobile System Activity timing

Fig. 4 shows an example of an activity period of an example mobile station. Graph 404 schematically shows an example of an activity burst in a mobile station. The horizontal axis represents time. The vertical axis represents power consumption. Between these bursts are sleep periods in which at least the GNSS part of the mobile station is put in a sleep mode and consumes little energy. The active duty cycle is low to keep the overall energy consumption low and can be adjusted based on considerations such as the speed of the mobile station, the proximity of the mobile station to a tracking area boundary or another mobile station, etc.

Graph 408 magnifies one burst of activity in graph 404. The horizontal axis represents time (at a different scale than the horizontal axis in graph 404). The vertical axis represents power consumption (on the same scale as the vertical axis in graph 404). The numbers associated with the bursts in graph 408 correspond to the block numbers in fig. 3. In the processing loop shown in fig. 3, there is a burst of activity within the mobile station. The width of the burst schematically shows the duration of the activity associated with the block in fig. 3. The average power consumed by the activities associated with the blocks in fig. 3 is shown highly schematically for a burst. For this illustrative example, the following list shows the duration and average power. These values are provided to illustrate the disclosure, not to limit the disclosure. Different implementations can have different sets of values. Furthermore, different operational scenarios using the same low-energy GNSS implementation may also result in different sets of values. For example, if system and environmental conditions allow the position estimate to use a smaller number of received p (y) chips (e.g., 1,000 is used for the following estimates), the power consumption associated with blocks 309 and 310 may be reduced.

Graph 412 schematically shows an example of code phase conversion in a GNSS signal. With clock synchronization and code phase information from the base station, the mobile station can initiate its signal acquisition based on the timing of the code phase transition (e.g., a particular chip transition) in block 309. Thus, the GNSS receiver of the mobile station can be switched on to acquire GNSS signals in a relatively short period of time, thereby reducing energy consumption.

Example preprocessed GNSS data

FIG. 5 illustrates example pre-processed GNSS data. In response to its receipt of the GNSS signals, the mobile station generates pre-processed GNSS data 500 and transmits the data to the base station, e.g., as shown in blocks 311 and 312 of fig. 3. In this example, the pre-processed data 500 includes estimated chip transition times for several satellites in the set of visible satellites transmitted by the base station, such as the satellites for which the mobile station is attempting to acquire signals. The data 500 optionally includes a quality indicator of the signal from each of the number of satellites. The mobile station may indicate in the pre-processed data when the mobile station fails to acquire signals from the satellite. In the illustration, the mobile station cannot acquire satellite # 3. Thus, the preprocessed data associated with satellite #3 is shown as unavailable (N/A). To compensate for the failure to acquire satellite #3, the mobile station acquires satellite #7 and includes the preprocessed data for satellite # 7. Satellite #7 may be substituted for satellite #3 due to directional considerations, as described above in connection with the description of block 307 in fig. 3.

The amount of pre-processing done in the mobile station and the content of the pre-processed data may vary based on factors such as technology, complexity of design, and energy consumption limitations. One of the main goals of low energy GNSS mobile systems is to reduce the power consumption of the mobile station. This implementation may be beneficial because it may reduce the power consumption of the mobile station by performing more preprocessing and transmitting shorter preprocessed data messages (which may use less power to transmit shorter messages). This may be because advances in semiconductor technology reduce power consumption associated with processing. On the other hand, power consumption associated with transmission may be at least partially limited by physics and may not scale directly with advances in technology. Thus, the low energy GNSS system may perform an optimization process to select the amount of pre-processing to be performed for the mobile station and the amount of pre-processed data 500 to send to the base station.

Example machine learning

The base station or remote server (e.g., CCU 128) may accumulate statistics regarding the mobile station's ability to acquire signals from GNSS satellites. Such statistics may be used to improve models of base stations of the tracking area, mobile station conditions, and/or future satellite selections. For example, in pre-processed data 500, the mobile station may additionally indicate that satellite #3 is unavailable because the peak in the correlator output is too wide. If over time statistics show that a particular mobile station often experiences similar acquisition failures for satellites in a certain direction relative to the mobile station, the base station can conclude that the mobile station is malfunctioning or the base station can incorporate mobile station defects in this direction in its mobile station model. The base station may then mark the mobile station as a candidate for maintenance or may eliminate satellites in that particular direction in a sorted list of future satellites transmitted to the mobile station. As another example, if a mobile station statistically displayed in a particular location in the tracking area (e.g., within boundary 144) generally has a problem in acquiring satellite signals from a satellite from a direction, the base station may infer that some obstacle exists in that direction and update its model of the tracking area. This may be useful when, for example, the map of the tracking area used by the base station has no (up-to-date) elevation information.

In various implementations, the base station or CCU may process the accumulated satellite acquisition statistics using machine learning algorithms to update an environmental model of the mobile station's movement, learn about the presence of previously unknown obstacles (and block GNSS signals from certain directions), or learn other patterns that may be used to transmit better satellite acquisition parameters to the mobile station. Machine learning algorithms may include neural networks, decision trees, support vector machines, probabilistic statistical methods (e.g., bayesian networks), data mining, and the like. Machine learning techniques can be supplemented with Geographic Information Systems (GIS) that analyze or provide geospatial data about the tracking environment.

Example operational scenarios

FIG. 6A illustrates an example of some operational scenarios of a low power GNSS mobile system. The dashed line 620 represents the boundary of the tracking area. Curves 640 and 660 represent the movement of two mobile stations, mobile a and mobile B, respectively. The open circles on the graph represent the position when the mobile station wakes up from sleep mode. The filled circles on the graph represent the position of the mobile station when it enters sleep mode. The small arrow from the open circle shows the direction of interest at that position/time. The direction of interest may include a direction toward a nearby mobile station or other obstacle (e.g., to avoid a collision) or a direction toward the nearest portion of the tracking area boundary 620 (e.g., where restrictive actions may occur in a geo-fence scenario). Six arrows around the perimeter show the position of the GNSS satellites with respect to the tracking area.

When more GNSS satellites are visible from the mobile station, it can be beneficial for the base station to rank the satellites based at least in part on their contribution to accuracy in the direction of interest. The position estimate has different degrees of uncertainty in different directions relative to the direction of the satellite on which the signal forms the basis of the estimate. GDOP is the source of this effect. As another example, it is generally desirable to determine the position of a mobile station with a greater degree of accuracy in the direction of movement of the mobile station.

The direction of interest associated with the location of mobile station a is the direction of its movement when it wakes up for the first and second times in the illustration in fig. 6A. This provides two small arrows showing close alignment with the curves at the two leftmost open circles 644 and 648 on curve 640. Thus, since satellites #1 and #4 are more closely aligned with the direction of interest than the other satellites, the base station may queue the two satellites higher up in the first wake-up period (starting with the empty circle 644). Since satellites #1 and #4 are in almost opposite directions from the perspective of mobile station a, using both in position estimation also reduces GDOP. For the same reason, the base station may be biased toward satellites #2 and #5 when ordering satellites for a second wake-up period (starting with open circle 648). When mobile a wakes up a third time in the illustration (starting with open circle 652), mobile B is approaching mobile a, as shown by curve 660 and open circle 664. Because collision avoidance is an important consideration, the direction of interest associated with mobile a is directed toward mobile B. Thus, the base station can be biased toward the most closely aligned satellite #2 along the direction of interest (although in the opposite direction). During a fourth wake-up period (beginning with open circle 656), mobile a approaches the tracking area boundary 620. Thus, the main direction of interest points to a point on the boundary closest to mobile a.

Implementations of low energy GNSS mobile systems can estimate the bearing or direction of movement of a mobile station in one or more ways. For example, the mobile station can estimate its position based on data from a dead reckoning sensor. The base station or mobile station can estimate the position of the mobile station based on a history of the location of the mobile station. The history may be based on GNSS data, non-GNSS data, or a combination of both.

FIG. 6B illustrates another example of an operational scenario for a low energy GNSS mobile system. The graphical representations are similar to those used in fig. 6A. Additionally, fig. 6B shows a rectangle 692 representing a structure that may block a line of sight to a satellite. The structure may be a building, a hill, a large vehicle (e.g., a truck), etc. The wing lobes attached to the hollow circle schematically represent the antenna pattern associated with the mobile station GNSS antenna.

In the case where the antenna pattern of the mobile station GNSS antenna is not hemispherical, the base station may include the antenna pattern and the orientation of the mobile station as factors in ordering the satellites. The base station can resist selection of satellites in the weak direction of the mobile station's antenna pattern. By reducing the queuing of satellites in the weak direction of the antenna pattern, the base station can reduce the likelihood that the mobile station will process a weak signal or not be able to acquire satellites at all due to the antenna pattern, thereby reducing the energy consumption of the mobile station. For example, during the second wake-up period (beginning with open circle 688 on curve 680), a base station with knowledge of the mobile station's antenna pattern and bearing can bias satellites #3 and #6 and reject satellites #1 and #4 in the sorted list.

In the case where the base station has information relating to the local environment, the base station can take this information into account when selecting a satellite. In the illustration, a structure 692 is present in the tracking region. The structure blocks the line of sight between satellite #7 and the mobile station during the first wake-up cycle (starting with open circle 684 on curve 680). The structure also blocks the line of sight between satellites #1 and #6 and the mobile station during the same wake-up period. Therefore, the base station can resist the mobile station from selecting the satellites #7, #1, and #6 using the information on the satellites, the structures, and the positions of the mobile station. The obstacle bias can exceed or outweigh the antenna pattern bias.

As described above, the low energy GNSS system can analyze the satellite acquisition behavior obtained from the mobile station to learn the tracking area. For example, structure 692 may not be initially present in GIS information about the tracking region, but via machine learning, the presence of the structure may be deduced from the satellite acquisition data. Thus, these embodiments of the GNSS system can continuously or periodically update their knowledge of the tracking area, acquisition mode of the mobile station, etc., to provide better estimates of the satellite acquisition parameters.

Example flow of clock synchronization for Low energy GNSS Mobile stations

Fig. 7A shows a flow for synchronizing clocks of mobile stations. To continuously maintain clock synchronization with the GNSS satellite clock, energy consumption is expensive. The base station connected to the external power supply is not energy limited and therefore can maintain continuous clock synchronization with the GNSS satellites. Mobile stations, on the other hand, are typically powered by a limited energy source and may not be burdened with maintaining continuous clock synchronization without draining their power supply. Thus, the mobile station can synchronize its clock on an as needed basis only. For example, the mobile station may synchronize its clock at the beginning of each wake-up period (or every third, fifth, tenth, or hundredth wake-up period). In addition, the mobile station may be subjected to various environmental stresses, such as temperature cycling, physical shock and vibration, and the like. Environmental stress may damage or disturb the mobile station's clock oscillator, increasing the timing error of the oscillator, and increasing the need for clock synchronization of the mobile station.

Precision timing protocols such as the dual message clock synchronization algorithm in the Institute of Electrical and Electronics Engineers (IEEE)1588 standard can be applied to low energy GNSS mobile systems for clock synchronization processors or controllers can apply frequency and phase compensation to digitally controlled oscillators (NCO). Long term error sources associated with the oscillator can be compensated for, resulting in zero average short term jitter. Low energy GNSS mobile systems are implemented to enable the clock of a mobile station to be indirectly synchronized to the GNSS satellite clocks by a clock in a base station. Synchronization may be accomplished through multiple communication messages and processing in the mobile station.

In fig. 7A, the mobile station 160 initiates a clock synchronization sequence by Transmitting (TX) its local time to the base station 120 and time stamping the transmission (shown by (1A) and (1B)). Upon Reception (RX) of a transmission, the base station time stamps the reception according to its local clock (1C). Since the base station's clock is synchronized to the GNSS satellite clock, the value of the base station clock is the same as the value of the satellite clock at the same time. Then, the base station responds by transmitting the reception timestamp value (1C) and also time-stamping the response ((2A) and (2B)). The mobile station receives the message (2A) and time stamps the reception according to the local clock of the mobile station (2C). The base station sends another message to the mobile station including the timestamp value of the last transmission by the base station (2B). The mobile station receives the second message (3A)) and time stamps its reception (3B). The mobile station can then synchronize its clock to the base station's clock based on the locally acquired time value and the time value transmitted from the base station. As part of the synchronization, the mobile station can correct the speed of light to account for communication path delays. The phrase "timestamp the transmission" (or receive/respond) includes, but is not limited to, stamping the exact time at a known time relative to the time the origin of the transmission (or reception) of the message passed through some system element, e.g., the time when the origin of the message signal was transmitted from the antenna, the time 5 μ s after the origin of the message was received at the receiver input, etc. The base station or mobile station may include time stamping hardware in the fine clock support blocks 252 and 292. A message that includes a special timestamp data field and/or value can trigger the timestamp hardware to capture the timestamp. The offset of the time stamp, which should be excluded in the clock synchronization process, can be characterized and reduced or eliminated from the process.

An advantage of a mobile station having a clock that is time synchronized to the base station clock and thus synchronized to the GNSS satellite clock is that fewer (three rather than four) satellites are required to provide an accurate position estimate for the mobile station.

The example clock synchronization algorithm shown in fig. 7A may rely on the assumption that a direct RF path exists between the base station and the mobile station. For example, the algorithm may compensate for the length of time it takes for a message to be transmitted between the two stations based on a nominal distance of the direct path calculated using the position of the base station and the estimated position of the mobile station. There may be cases where this assumption is incorrect. For example, a temporary barrier such as a truck may be present in the direct RF path between the base station and the mobile station. In this case, the RF signal can travel on a reflected path between the two stations rather than a direct path.

The reflected path can degrade the RF signal so that the two stations cannot establish communication over the direct path. If this occurs, the two stations can attempt to establish communication through the link repeater, if available, or the mobile station can enter autonomous mode until communication is established with the base station. In embodiments where the base station transmits at a higher power level on the RF link than the mobile station, the mobile station may be provisioned with the transmit power level of the base station. The mobile station can use the information about the transmit power level of the base station, the actual receive power level of the RF signal from the base station, the transmit power level of the mobile station, and/or the receiver sensitivity of the base station to determine whether the base station can receive communications from the mobile station over the RF link.

The RF signal from the base station that determines the actual received power may be a ready signal indicating the availability of the base station. If the mobile station determines that a message from the mobile station cannot be received by the base station under the current conditions of the RF path, the mobile station may enter an autonomous mode, may temporarily increase its transmit power on the RF link (at the expense of possibly increased energy consumption), and/or the two stations may communicate with their link repeaters with a direct RF path through the two stations (including clock synchronization messages) to give three example responses.

If communication over an RF link between two stations can be established over a reflected path, the actual length of time for the message to travel between the two stations may be longer than expected over the direct path. Longer propagation times can introduce timing offsets to the mobile station's clock relative to the base station's clock if not compensated for. This timing offset, in turn, can reduce the accuracy of the position estimate or cause code phase errors during position estimation. Small timing offsets may reduce the accuracy of the position estimate. An example of a small timing offset is an offset on the chip time scale or less, e.g., less than 100 nanoseconds at 10.23MHz P (Y) chip rate, which translates to a difference of about 100 feet between the direct and reflected paths at the speed of light. Larger timing offsets can lead to code phase errors in the position estimation process. Examples of larger timing offsets are offsets on the order of several chip times, such as hundreds (e.g., 500, 700, etc.) nanoseconds at 10.23MHz P (Y) chip rate, or on the order of hundreds (e.g., 500, 700, etc.) feet between the direct and reflected paths. The cutoff between large and small timing errors typically varies from implementation to implementation. The exemplary values provided above are for illustration and not for limitation.

One way to reduce the likelihood of code phase error due to lack of a direct path is to increase the width of the search window to obtain peaks from the correlators in the mobile station (although possibly at the expense of increased power consumption by the mobile station). The cutoff between the magnitude time errors can increase as the search window width increases. It is also feasible to detect the reflected path by the actual RF path loss (transmit power minus receive power). If the actual RF path loss is much greater than expected, taking into account the nominal distance and the two antenna gains, the mobile station or base station can infer that the received RF signal traveled via a reflected path. In response, the mobile station may temporarily increase the width of the search window, or the two stations may be clock synchronized through a link repeater having a direct RF path with the two stations to give two example responses.

Example flow involving clock synchronization of Link repeaters

One or more link repeaters 140 optionally can be used to relay messages between the base station and the mobile station, where the tracking area may extend beyond the communication range between the base station and the mobile station, or objects may block a direct RF path from the base station to a location where the mobile station may perform GNSS position estimation. Where one or more link repeaters are used, the link repeaters are typically installed such that a mobile station at any location in the tracking area (e.g., the area enclosed by the boundary 144) can communicate directly or indirectly with the base station through the one or more link repeaters. Communications between the base station and the mobile station may be relayed through one or more link repeaters. As the location of the mobile station changes, different link repeaters and/or different numbers of link repeaters may participate in the communication between the mobile station and the base station. The link repeater can communicate with the base station (e.g., via an RF link) and relay messages of the base station to the mobile station (e.g., also via an RF link).

Like the base station, the link repeater may transmit at a higher power level on the radio link than the mobile station. The link repeater may periodically transmit a ready signal to indicate its availability. The base station may instruct the link repeater to turn off transmission of the ready signal when no mobile station is communicating by virtue of the link repeater, and may instruct to turn on transmission of the ready signal when the mobile station is communicating by virtue of the link repeater. Fig. 7B illustrates an example flow of synchronizing the clock of the mobile station 160 through the link repeater 140. Alphanumeric references indicate similar actions or events as in fig. 7A. For example, (1A) represents a local time message from the mobile station 160 in both fig. 7A and 7B. Actions or events associated with the link repeater 140 are labeled with a corresponding alphanumeric reference, with a small "i" appended to the end. For example, (1Ai) represents a local time message from the link station 140. As another example, (4) represents synchronization of mobile station clocks; (4i) indicating synchronization of the link repeater clocks.

The embodiment shown in fig. 7B is a two-part process. Each of the two parts involves similar actions to those shown in fig. 7A. In the first part, after the mobile station initiates the clock synchronization sequence, the link repeater synchronizes its clock to the clock of the base station. At the end of the first portion, the clock in the link repeater is synchronized to the base station clock, and thus to the GNSS satellite clock. In the second part, the mobile station synchronizes its clock to the clock of the link repeater. At the end of the second portion, the clock in the mobile station is synchronized with the link repeater clock, and thus with the GNSS satellite clock. Where multiple link repeaters relay communications between the mobile station and the base station, the embodiment shown in fig. 7B may be extended to cover multiple link repeaters.

Other embodiments may be utilized. For example, if the link repeater remains synchronized with the base station clock (e.g., in the background), the processing of the first part shown in fig. 7B may not be necessary. Furthermore, if the delay through the link repeater can be accurately characterized, it may not be necessary to synchronize the clocks of the link repeaters. In other embodiments, the link repeater's clock may be periodically or continuously synchronized with the base station clock, and not necessarily only in response to a request from the mobile station. The clock of the mobile station can be synchronized to the link repeater clock on an as needed basis.

Example pseudolite System implementation

As described above, pseudolites are capable of providing GNSS signals when the line of sight of GNSS satellites is obstructed. FIG. 8 illustrates an example embodiment of a low energy GNSS mobile system including pseudolites. For illustrative purposes, one GNSS pseudolite 840, one base station 120, and one mobile station 160 are shown, but not by way of limitation. The base station 120 and the mobile station 160 are generally the same as shown in the example shown in fig. 2A. Pseudolite 840 includes GNSS transceiver 848, processor and data storage unit 852, radio link 276 and solar panel 844.

When a pseudolite is installed, its precise location may be entered and stored in its data storage. Pseudolites include position data when generating navigation messages (similar to position data transmitted from GNSS satellites) that are transmitted via navigation signals. The navigation signals can include GNSS-like signals. Additionally or alternatively, the position data of the pseudolite can be stored in a data memory of the base station. The base station may transmit the location data to the mobile station via a base station-mobile radio link. Because the position of a pseudolite typically does not change (e.g., it is fixed), or only changes infrequently (e.g., if the pseudolite is relocated), the base station may send the pseudolite position information to the mobile station once (e.g., for a fixed pseudolite) or as needed (e.g., if the pseudolite is relocated). The mobile station can store the location data in its data store. For position estimation purposes involving pseudolites, position data stored in the base station or mobile station can replace position data (ephemeris) in GNSS satellite signals; the position data may be omitted in the GNSS signals from the pseudolites. For purposes of this disclosure, GNSS signals from pseudolites may not include the same or similar data structures as those used in GNSS satellite signals in some cases. For example, a GNSS-like signal from a pseudolite may include data spread in such a way that the mobile station can obtain chip transition times from the signal. The data in the GNSS-like signals may include a set of chip transitions for a particular synchronization time. GNSS-like signals can include timing codes (similar to C/a codes or p (y) codes) modulated onto pseudolite carrier frequencies. The GNSS-like signals may be extended such that the same correlator in the GNSS receiver that analyzes the GNSS signals from the satellites can additionally or alternatively analyze the GNSS-like signals from the pseudolites. The pseudolite navigation signal may include information that uniquely identifies the pseudolite, for example, the navigation signal may modulate a PRN code on the pseudolite carrier frequency.

The pseudolite transmits GNSS signals or GNSS-like signals via transmitter 848. The mobile station receives GNSS signals through its antenna and receiver. Pseudolites may communicate with base stations over the same unlicensed RF band used for base station-to-mobile communications, as shown in fig. 8. Alternatively, the pseudolite may communicate with the base station through a wired connection.

As described in the summary, in some embodiments it may be advantageous to use an unlicensed frequency band that is close to the frequency band used by GNSS satellites. For example, unlicensed bands exist in the united states in the frequency range of 1626.5MHz to 1645.5MHz, approaching the GPS L1 band. As a result, embodiments of the mobile station may include a tunable antenna and an analog receiver that may function in both the unlicensed frequency band and the L1 frequency band. The use of a tunable antenna and analog receiver for the two frequency bands typically means that the mobile station is able to receive from GNSS satellites or pseudolites at any given time, rather than simultaneously.

In various embodiments, the pseudolite RF transmission band can have a bandwidth of less than about 10MHz, 20MHz, 30MHz, or 50MHz, or can be in the range of about 10MHz to 100MHz, and the pseudolite RF transmission band can have a carrier frequency separated from the GNSS satellite carrier transmission frequency (e.g., L1) by less than about 100MHz, less than about 75MHz, less than about 60MHz, less than about 50MHz, or less than about 25 MHz. Currently in the united states, FCC regulations are such that the only large block of spectrum around L1 and allowed unlicensed use is 1.6265GHz to 1.6455GHz, so the maximum allowed bandwidth of the pseudolite RF transmission band currently in the united states is 18MHz, with the signal centered at 1.6355 GHz. However, the 18MHz bandwidth is sufficient to encode signals having the same chip rate of 10.23MHz as the p (y) code.

In a low energy GNSS mobile system, a base station can transmit a set of satellites and associated code phases to a mobile station. The mobile station then acquires GNSS signals based on the code phase timing information provided by the base station. Thus, the base station is actually able to determine the timing of acquisition of GNSS signals by the mobile station. The base station can instruct the pseudolite to transmit when the mobile station is expected to initiate signal acquisition. Since the mobile station acquires GNSS signals only for a short time, the pseudolites can only transmit for a correspondingly short time. The pseudolite can suspend transmission of its GNSS signals until the mobile station again seeks to acquire signals from the pseudolite. It is beneficial in case legitimate operation in the unlicensed band is determined based on the average transmission power. For example, the Federal communications Commission specifies that it is allowed to increase the transmit power by up to 20dB over a duty cycle. The low duty cycle of the transmission allows for an actual transmission power (in a short time) that is much higher than the legal licensed average. The higher actual transmit power translates into a higher SNR or longer communication range from the pseudolite.

Furthermore, multiple GNSS satellites transmit simultaneously. Even slight timing errors in GNSS receivers can cause intersymbol interference between signals from different satellites, thereby reducing the received SNR. In the case where the installation of a low power GNSS mobile system includes multiple pseudolites, the base station may instruct each pseudolite to transmit at a different time to eliminate inter-symbol interference and an increasing received SNR in mobile stations with the receiver off-timing. In embodiments where each pseudolite transmits at a different time, the PRN codes used by all the pseudolites can be the same, since intersymbol interference is not a significant issue. However, different pseudolites may use different PRN codes to allow authentication or error checking. The base station may configure the sleep parameters that are transmitted to all mobile stations in the vicinity so that all mobile stations will seek to acquire signals from the same pseudolite at the same time.

If the base station determines that there are no mobile stations in the vicinity of the pseudolite, the base station may instruct the pseudolite to remain off. This reduces the energy consumption of the pseudolite even further. The power consumption of the pseudolite may be low enough that alternative energy sources, such as solar panels 844, may be used. Other alternative energy sources include wind power.

The pseudolite may synchronize its local clock to the base station clock, which itself represents the GNSS satellite time, just prior to the pseudolite transmitting its GNSS-like signals, using a clock synchronization method similar to that used by the mobile station to synchronize its clock to the base station clock (see, e.g., the description with reference to fig. 7A). Such synchronization may be advantageous for power limited pseudolites because conventional pseudolites normally use a relatively high-power temperature-compensated crystal oscillator (TCXO) plus a GNSS receiver to correct for long-term drift of the pseudolite clock. Keeping the TCXO and GNSS receiver running consumes considerable power and, of course, increases hardware costs.

In some embodiments, the pseudolite only transmits when commanded by the base station (e.g., because the mobile station requires a pilot signal from the pseudolite), and the pseudolite may not always require an accurate clock. Pseudolites used with mobile stations in autonomous mode (e.g., when the RF link to a base station is lost) will generally transmit quasi-continuously, as the pseudolite will generally not know when the mobile station needs to perform a position fix. In some such embodiments, the pseudolite is able to run a clock synchronization protocol in the background whenever it communicates with the base station (possibly via a link repeater) and avoid having to run a GNSS receiver and TCXO, which reduces energy usage.

Example State diagrams relating to Low energy GNSS positioning systems in retail applications

FIG. 9 illustrates an example state diagram relating to a low energy GNSS positioning system in an example retail store application. In this example application, the human-propelled shopping cart would be located and included within a confinement boundary (e.g., the perimeter of a parking lot near the store). As mentioned above, the mobile station 160 can be disposed in the wheels of the shopping cart and/or in other parts of the cart (e.g., the frame or handlebars). The mobile station 160 may be attached to a shopping cart, or be an integral part of a cart. The mobile station 160 may have components located in different parts of the cart, such as a GNSS section in the cart frame or handlebars (where the GNSS antenna can more easily receive signals from orbiting satellites) and dead reckoning sensors in the cart wheels (where wheel rotation can be measured to estimate travel distance). In a retail store installation, the GNSS antenna 124 of the base station 120 can be placed on the back of the store, away from the customer's line of sight, if cumbersome or unsightly. The base station 120 may be located inside a store. Pseudolite 180 can be used inside a store (where GNSS signals are blocked or weak) or outside a store (if surrounding buildings, terrain, or vehicular traffic block GNSS satellite signals). Link repeaters 140 can be placed throughout the tracking area to enhance the RF signal between the base station and the mobile station.

Referring to FIG. 2A, a mobile station 160 disposed in or on a shopping cart includes a non-GNSS dead reckoning sensor 280 (e.g., a magnetic heading sensor and a rotation sensor in a wheel) to determine a dead reckoning position of the cart. The cart may include a brake that, when actuated, prevents movement of the cart. For example, the wheels of the cart may include brakes that lock or inhibit rotation of the cart wheels. The cart may also include sensors for sensing when the cart is approaching or passing a warning boundary or a restrictive boundary. For example, the cart wheel can include an RF receiver that senses VLF signals embedded in the line at the boundary or RF signals from wireless access points that emit the outfield. As will be described with reference to the state transitions shown in fig. 9, upon receiving the boundary signal, the cart may perform containment actions (e.g., provide a warning or actuate a brake) to maintain containment of the shopping cart within a restricted area (e.g., to reduce theft of the cart).

The example state diagram in FIG. 9 illustrates the state of a mobile station that includes a GNSS portion and a dead reckoning sensor mounted on or within a shopping cart. In the operational scenario shown in fig. 9, the location of a shopping cart is tracked outside the store (e.g., in a parking lot); however, this is for illustration and not limitation (other embodiments may track cart movement within a store). A warning signal may be generated when the cart is within a warning area, such as warning area 156 in fig. 1. When the cart leaves a restricted area, such as the restricted area within the restricted boundary 148 in fig. 1 (which may be the periphery of a parking lot outside the store), the cart brake may be activated to inhibit movement of the cart. The electric vehicle retriever can be used to collect vehicles at a parking lot and return them to a cart collection area.

The example state diagram of fig. 9 may be implemented, for example, by the mobile processor 272 in the mobile station. For illustrative purposes, the description of FIG. 9 begins with the run state 904. However, this is not a limitation. The mobile station may complete the state diagram from another operational state. Further, the state diagram in fig. 9 is an example, and in other retail applications, the states shown can be combined, rearranged, or omitted, and additional or different states may be included.

At state 904, the cart is inside the store; the GNSS part of the mobile station of the cart is inactive to save energy. In addition to a possible motion detector (e.g., one of an accelerometer or dead reckoning sensor) that detects when the cart starts moving, the non-GNSS portion of the mobile station can also be inactive. The motion detector may be continuously or periodically active. The mobile station remains in state 904 as long as motion detection does not detect motion that exceeds the selected motion threshold. If the motion detector detects motion that exceeds the selected motion threshold, the mobile station transitions to state 908.

At state 908, the mobile station of the cart wakes up partially in the store. At least the motion detector and exit field sensor (which senses motion through opening 136 in fig. 1) are active. Other parts of the mobile station may or may not be active. The state transitions back to state 904 if the motion sensor does not detect any motion state that exceeds a selected motionless threshold (which may or may not be the same as the selected motion threshold governing the transition from state 904 to state 908) for at least a timeout period. If the exit field sensor detects movement through an opening out of the store, the mobile station can set the starting coordinates of its dead reckoning sensor to the coordinates associated with the opening (as may be detected by the exit field sensor) and the state transitions to 912.

At state 912, at least the exit field sensor and the dead reckoning sensor are active. Dead reckoning sensors, including wheel rotation sensors, maintain a count of the rotations of the cart wheels. If the exit field sensor detects movement back to the store through the opening, the state transitions back to state 908. If the cart reaches a minimum spin count threshold (indicating a minimum distance traveled) while outside the store, the state transitions to state 916.

In state 916, the GNSS portion of the mobile station wakes up and is active and initiates a GNSS location determination process, for example by communicating with the base station as shown in FIG. 3. If the mobile station obtains a good GNSS position and the position is not within the warning region, the mobile station can update the minimum rotation count and return to state 912. If the mobile station cannot obtain a good position fix, it may repeat in state 916, e.g., from block 312 back to block 306 in FIG. 3. If the mobile station is unable to establish a link with the base station, the mobile station may enter an autonomous mode as described above. If the mobile station obtains a good position fix and the position fix is within the warning region, the state transitions to state 920.

In state 920, the mobile station provides an alert, such as by an audible or visual signal, to alert the person pushing the cart that it is approaching the confinement boundary. The dead reckoning sensor continues to estimate the cart position by counting wheel rotations. If the count reaches a minimum rotation count threshold applicable to the warning region, then the state transitions to state 924.

In state 924, the GNSS portion of the mobile station wakes up and is active and initiates a GNSS location determination process, for example as shown in FIG. 3. Such a location determination process may have a stricter target accuracy than the process associated with state 916, as there is a need to determine how close the cart is to the limiting boundary with more rigorous accuracy. The location determination process may emphasize a certain direction of interest (e.g., a direction toward the limiting boundary), such as illustrated by the open circle 656 in fig. 6A. If the location indicates that the cart is somehow returned to the store, the state will transition back to state 908. If the location indicates that the cart is no longer within the warning area but is still outside the store, the state transitions back to state 912. If the positioning indicates that the cart is still within the warning area, the state transitions back to state 920 (e.g., and another warning is provided). If the positioning indicates that the cart is outside the restricted area, a cart restriction action can be performed. For example, the cart brake can be activated to inhibit cart movement and/or an alarm message can be sent to the base station or central control unit. The state transitions to state 928 indicating that the cart is braked (or locked) outside of the restricted area. If the mobile station is unable to obtain a good position fix, it may repeat in state 924, e.g., from block 312 back to block 306 in FIG. 3. If the mobile station is unable to establish a link with the base station, the mobile station may enter an autonomous mode as described above.

At state 928, movement of the cart a greater distance outside the restricted area has been prohibited, which may reduce or prevent theft of the cart. The cart remains in this position awaiting collection by a human operator or electric vehicle retriever. For example, the mobile station may wait to retrieve a message in response to an alert message sent from the cart during transition to state 928. The retrieval information can be communicated to the mobile station by a human operator with a remote control or by a cart retriever, indicating that the cart should be taken care of by a store clerk. The cart undergoes a retrieval process in which the cart brakes may be deactivated, allowing retrieval of the cart. The state transitions to state 932.

At state 932, if the exit field sensor detects (e.g., by detecting the exit field 132) a movement of the cart back to the store through the opening 136 during the retrieval process, the state transitions back to state 908. Otherwise, the state transitions to state 916 where the mobile sensor initiates the GNSS positioning determination process to obtain its location (which may be outside of the store).

While the foregoing example retail application is described with reference to shopping carts, this is for illustration and not limitation. In another retail application, handheld shopping baskets can be located and tracked. The basket may include a pedometer for estimating the gait of the customer and a compass for estimating the direction of the customer as part of the dead reckoning position estimation, rather than using wheel rotation to measure distance. Further, in shopping basket applications, instead of using a cart brake, the shopping basket may include an alarm that is activated when the shopping basket leaves the restricted area.

Furthermore, low energy GNSS technology can be used in non-retail applications that utilize human-propelled wheeled carts, such as locating warehouse carts in a warehouse environment, baggage carts in an airport, or medical carts or wheeled beds in a medical environment, and the like.

Example livestock tracking applications involving Low energy GNSS positioning systems

The low energy GNSS mobile system can be used for livestock tracking. Many of the general principles of this application are similar to those described above for the example retail application. Some specific points of application are described below. Livestock includes, but is not limited to, livestock, cows, horses, or other types of livestock raised on farms or agricultural sites.

A mobile station in a livestock tracking application can include a GNSS portion and a dead reckoning sensor for providing a non-GNSS based position estimate. The dead reckoning sensors can include accelerometers or magnetometers, and optionally MEMS (micro-electro-mechanical systems) gyroscopes. The mobile station component can be disposed in or on a collar worn by the animal, or on a tag attached to the animal (e.g., on the ear or leg). A tag comprising a mobile station may be attached to a collar or strap worn by the animal. In some cases, the collar or tag may include a solar panel that provides power to the mobile station. The GNSS receiver and power supply may also be in or on the collar, although not necessarily in the same physical housing as the dead reckoning sensor. For example, a small Printed Circuit Board Assembly (PCBA) including electronics and a GNSS antenna can be disposed on top of the collar (such that the GNSS antenna can receive signals from GNSS satellites or pseudolites in view), and a battery compartment can be disposed on the bottom of the collar. The collar may be designed such that the PCBA can be retained at or near the top, such as by placing a majority of the concentrated mass of the collar at the bottom. Other designs or arrangements may take into account livestock comfort factors or farm logistics usage considerations.

The mobile station attached to the animal is capable of providing a motion profile of the animal. The main indicators of illness or estrus can be partly deduced from the exercise profile. These primary indicators can provide valuable information for livestock management. The collar may include a health monitor, such as a body temperature sensor, to further assist in tracking the health of the animal. The mobile station can communicate the herd's motion profile or health information to a base station or central control unit for analysis and data mining operations. In some embodiments, the mobile station includes (or is in communication with) other animal sensors such as a thermometer, a microphone, and the like.

The speed of movement of the animal can be determined by a pedometer algorithm running on an accelerometer or magnetometer, plus optionally a gyroscope. The pedometer algorithm can be adjusted for the particular animal to which the collar is attached, for example measuring the gait of a cow. Because the dead reckoning parameter variability between individual cows (or other animals) in one herd can be generally much greater than the dead reckoning parameter variability between individual carts in the example retail application described above, machine learning can be implemented to understand the gait of the animals. Machine learning algorithms may include neural networks, decision trees, support vector machines, probabilistic statistical methods (e.g., bayesian networks), data mining, and the like. In machine learning, GNSS positioning using low energy GNSS mobile systems can be used to obtain accurate trajectories of animals. From the accurate trajectory, new parameters of the dead reckoning algorithm (e.g., gait detection) can be derived. The derivation of the new dead reckoning parameters can be done at the processor of the mobile station, the base station, the central control unit, or a remote server connected via a network. An embodiment may trade off the energy consumption for this derivation process (e.g., reduction of raw data) in the processor of the mobile station with the energy consumption for communicating raw data over the radio link to the base station, similar to that described above in connection with fig. 5.

Pseudolites as described above are capable of providing accurate position data associated with an animal as it enters or remains in an indoor structure, such as a barn or milking stall. Although such structures may be at least partially open, GNSS satellites may not be observed within such structures, or satellite signals may degrade in such structures, particularly for structures covered with metal roofs.

A livestock owner, such as a dairy farmer, may wish to use embodiments of the GNSS positioning system described herein to obtain information including: (1) when each animal reaches a particular location of the structure (e.g., barn, milking stall, etc.) or outside (e.g., trough, water supply, sunny area, etc.); (2) how long the animal stays there, and how long it takes en route between specific areas; (3) how anxious or calm the animal's motor characteristics or characteristics, the condition of the animal's general health status, en route between different locations and locations of interest; or (4) how herds aggregate and move together, or how individual groups aggregate and move together (e.g., animal a approaches a herd of animals B, C and D and then exits). For example, this information can be used to keep track of the social hierarchy of herds, monitoring instability in dominance relationships. The animal owner may be less concerned with the location versus time curve of the animal, except that the curve may be necessary to provide a piece of information of the owner's herd. In other cases, the livestock owner may wish to analyze the position versus time curves of certain high value animals (e.g., breeding thoroughbred) to track their movements and interactions with other animals (e.g., mares).

The livestock tracking application may have different system parameters than the retail store shopping cart containment application. For example, in animal tracking applications, the requirements for position estimation accuracy may be lower, particularly if the tracking area (e.g., pasture) of the animal application is larger than the shopping cart containment area (e.g., parking lot). Nonetheless, the various embodiments of the low energy GNSS movable object positioning systems described herein can be used in any application. The foregoing are merely example applications of the disclosed GNSS technology. In other embodiments, low energy GNSS positioning technology can be used for other tracking applications (e.g., locating or tracking any type of human-propelled cart).

Additional aspects and examples

In aspect 1, a system for positioning a movable object, the system comprising: a mobile station and a base station, the mobile station configured to be associated with a movable object and comprising: a Radio Frequency (RF) mobile communication system configured to operate an RF link having an RF link frequency in an RF band unlicensed for cellular communication; a mobile Global Navigation Satellite System (GNSS) receiver; and a dead reckoning system comprising a non-GNSS sensor, the dead reckoning system configured to use measurements from the non-GNSS sensor to provide an estimated position of the mobile station; the base station is located at a fixed location and includes: a base RF communication system configured to bidirectionally communicate with a mobile communication system over the RF link; a base GNSS receiver; and a hardware processor, wherein the base station is configured to: receiving an estimated position of the mobile station determined by the dead reckoning system from the mobile station over the RF link; determining satellite acquisition information comprising a set of GNSS satellites predicted to be visible at the estimated position of the mobile station and a GNSS code phase associated with each GNSS satellite in the set, the set of GNSS satellites comprising at least a minimum number of GNSS satellites; communicating satellite acquisition information to the mobile station over the RF link; receiving chip transition time information associated with a set of GNSS satellites from a mobile station over an RF link; determining an updated position of the mobile station based at least in part on the chip transition time information; and communicating the updated position to a mobile station over an RF link, and wherein the mobile station is configured to: communicating an estimated position of the mobile station determined by the dead reckoning system to the base station over the RF link; receiving satellite acquisition information from a base station over an RF link; obtaining GNSS signals from at least some of the set of GNSS satellites; determining from the acquired GNSS signals chip transition time information associated with GNSS code phases of the at least some of the GNSS satellites in the set; and communicating the chip transition time information to a base station over an RF link.

In aspect 2, the system of aspect 1, wherein the movable object comprises a human-propelled cart having wheels.

In aspect 3, the system of aspect 2, wherein the human-propelled cart comprises a shopping cart.

In aspect 4, the system of aspect 2, wherein the non-GNSS sensor comprises a magnetic heading sensor and a wheel rotation sensor.

In aspect 5, the system of aspect 1, wherein the movable object comprises a human or animal and the non-GNSS sensor comprises a pedometer and a magnetic heading sensor.

In aspect 6, the system of any of aspects 1 to 5, wherein the RF link frequency ranges from 426MHz to 435MHz, 779MHz to 787MHz, 863MHz to 870MHz, 900MHz to 928MHz, 2.400GHz to 2.483GHz, or 5.725GHz to 5.875 GHz.

In aspect 7, the system of any of aspects 1-6, wherein the minimum number of GNSS satellites is greater than or equal to 4.

In aspect 8, the system of any of aspects 1-7, wherein the satellite acquisition information further comprises doppler shift information associated with satellites in the set of GNSS satellites.

In aspect 9, the system of any of aspects 1 to 8, wherein the satellite acquisition information further comprises initialization parameters of the mobile GNSS receiver, the initialization parameters comprising parameters for a frequency locked loop or a phase locked loop.

In aspect 10, the system of any of aspects 1 through 9, wherein the base station is configured to queue the set of GNSS satellites according to one or more ordering criteria.

In aspect 11, the system of aspect 10, wherein the ranking criteria comprises one or more of: whether the satellite is along a direction of travel or a direction of interest of the mobile station, whether the satellite is near the horizon of the mobile station, the height of the satellite above the horizon of the mobile station, the doppler shift of the satellite, the ionospheric propagation error of the satellite, the location proximity information of at least two satellites, the antenna pattern of a GNSS antenna of the mobile station, or an obstacle present near the mobile station that can inhibit reception of GNSS signals from the satellite.

In aspect 12, the system of any of aspects 1 through 11, wherein the satellite acquisition information includes selection information associated with an order in which the mobile station should attempt to acquire GNSS signals from satellites in the set of GNSS satellites.

In aspect 13, the system as in aspect 12, wherein the order is based at least in part on whether an incident occurred.

In aspect 14, the system of any of aspects 1 through 13, wherein the base station is configured to determine the set of GNSS satellites based at least in part on reducing or minimizing the spread of precision factor.

In aspect 15, the system of any of aspects 1 to 14, wherein the chip transition time information further comprises a quality indicator of the at least some GNSS satellites in the set, the quality indicator being associated with a quality of GNSS signals received by the mobile GNSS receiver.

In aspect 16, the system as in aspect 15, wherein the quality indicator comprises information associated with one or more of GNSS signal power, peak width in correlator output, or signal to noise ratio.

In aspect 17, the system of any of aspects 1 through 16, wherein the mobile station and the base station are configured to exchange clock timing information over the RF link, and the mobile station is configured to synchronize the mobile station clock to a base station clock representing the time of the GNSS satellite based at least in part on the timing information.

In aspect 18, the system of any of aspects 1-17, wherein the minimum number of GNSS satellites is greater than or equal to 3.

In aspect 19, the system of any of aspects 1 to 18, further comprising a link repeater, wherein the mobile station and the base station are each configured to communicate bi-directionally over the RF link with the link repeater.

In aspect 20, the system of any of aspects 1 to 19, wherein the mobile station comprises a mobile station clock, the link repeater comprises a link repeater clock, the base station comprises a base station clock representing a time of the GNSS satellite, and wherein the mobile station and the link repeater are configured to synchronize the mobile station clock with the link repeater clock, and the link repeater and the base station are configured to synchronize the link repeater clock with the base station clock.

In aspect 21, the system of any of aspects 1-20 further comprises a pseudolite configured to communicate a navigation signal to the mobile station.

In aspect 22, the system of aspect 21, wherein the mobile station is configured to: acquiring a navigation signal from a pseudolite; determining a pseudolite chip transition time associated with the navigation signal; and communicating the pseudolite chip transition time to the base station over an RF link.

In aspect 23, the system of aspect 22, wherein the base station is configured to determine an updated position of the mobile station based at least in part on the pseudolite chip transition times.

In aspect 24, the system of any of aspects 21-23, wherein the pseudolite is configured to communicate the navigation signal at a pseudolite carrier frequency within a GNSS satellite signal carrier frequency range of 100 MHz.

In aspect 25, the system of aspect 24, wherein the pseudolite carrier frequency is in a range of 1626.5MHz to 1645.5 MHz.

In aspect 26, the system of any of aspects 1 to 25, wherein the mobile station is configured to store the sleep parameter comprising a time or a condition when the mobile station is to wake up and begin communicating with the base station.

In aspect 27, the system of any of aspects 1 to 26, wherein the mobile station is configured to: including an autonomous mode in which the mobile station calculates its position using GNSS signals derived from GNSS satellites; and operating in the autonomous mode when the mobile station is unable to receive communications from the base station over the RF link.

In aspect 28, the system of any of aspects 1 to 27, wherein the base station comprises a network connection to a data source providing one or more of: GNSS ephemeris, GNSS almanac, ionospheric correction model, or weather conditions.

In aspect 29, the system of any of aspects 1 through 28, wherein the base station is configured to obtain information related to satellite acquisition of the mobile station.

In aspect 30, the system of any of aspects 1-29, wherein the system is configured to analyze information related to satellite acquisitions of the mobile station using machine learning techniques to update a model of a tracking area in which the movable object moves, a condition associated with the mobile station, or a determination of a set of GNSS satellites predicted to be visible at an estimated location of the mobile station.

In aspect 31, the system of any of aspects 1 through 30, wherein to determine the chip transition time information associated with the GNSS code phases of the at least some of the GNSS satellites in the set, the mobile station is configured to search for a chip transition within the displacement window based at least in part on an estimate of an error in clock synchronization between the mobile station and the base station.

In aspect 32, the system of aspect 31, wherein the displacement window is in a range of 0.5 μ β to 10 μ β or 1 μ β to 1000 μ β.

In aspect 33, the system of any of aspects 1-32, wherein the GNSS comprises a Global Positioning System (GPS), and the mobile GNSS receiver and the base GNSS receiver comprise GPS receivers. In the system of any one of aspects 1 to 33, the base station comprises a mains powered supply and the mobile station comprises a non-mains powered supply. The non-mains power supply can include a battery, a capacitor (e.g., an ultracapacitor or supercapacitor), or a solar cell.

In aspect 34, a method for locating a movable object, the method performed by a mobile station configured to be associated with the movable object and a base station located at a fixed location, the mobile station and the base station configured to communicate bi-directionally over a Radio Frequency (RF) link, the RF link having an RF link frequency in an RF band that is unlicensed for cellular communications, the method comprising: determining, by the mobile station, an estimated position of the mobile station via a dead reckoning technique; communicating, by the mobile station, the estimated position of the mobile station over the RF link; receiving the estimated location by a base station over an RF link; determining, by a base station, satellite acquisition information comprising a set of Global Navigation Satellite System (GNSS) satellites that are predicted to be visible at an estimated position of a mobile station and a GNSS code phase associated with each GNSS satellite in the set, the set of GNSS satellites comprising at least a minimum number of GNSS satellites; communicating satellite acquisition information to the mobile station over the RF link through the base station; obtaining GNSS signals from at least some of the set of GNSS satellites; determining, by the mobile station, from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some of the GNSS satellites in the set; communicating chip transition time information over an RF link by a mobile station to a base station; determining, by the base station, an updated position of the mobile station based at least in part on the chip transition time information; and communicating the updated position to the mobile station over the RF link through the base station.

In aspect 35, the method of aspect 34, wherein the movable object comprises a human-propelled cart having wheels.

In aspect 36, the method of aspect 35, wherein the human-propelled cart comprises a shopping cart.

In aspect 37, the method of aspect 34 or aspect 35, wherein determining the estimated position of the mobile station by the mobile station via dead reckoning techniques includes determining the estimated position using measurements from a magnetic heading sensor and a wheel rotation sensor.

In aspect 38, the method of aspect 34, wherein the movable object comprises a human or animal, and wherein determining the estimated position of the mobile station via a dead reckoning technique by the mobile station comprises determining the estimated position using at least one accelerometer.

In aspect 39, the method of any one of aspects 34 to 38, wherein the RF link frequency ranges from 426MHz to 435MHz, 779MHz to 787MHz, 863MHz to 870MHz, 900MHz to 928MHz, 2.400GHz to 2.483GHz, or 5.725GHz to 5.875 GHz.

In aspect 40, the method of any of aspects 34 to 39, further comprising queuing, by the base station, the set of GNSS satellites according to one or more ranking criteria.

In aspect 41, the method of aspect 40, wherein the ranking criteria comprises one or more of: whether the satellite is along a direction of travel or a direction of interest of the mobile station, whether the satellite is near the horizon of the mobile station, the height of the satellite above the horizon of the mobile station, the doppler shift of the satellite, the ionospheric propagation error of the satellite, the location proximity information of at least two satellites, the antenna pattern of a GNSS antenna of the mobile station, or an obstacle present near the mobile station that can inhibit reception of GNSS signals from the satellite.

In aspect 42, the method of any of aspects 34 to 41, further comprising determining, by the base station, selection information associated with an order in which the mobile station should attempt to acquire GNSS signals from satellites of the set of GNSS satellites.

In aspect 43, the method of any one of aspects 34 to 42, wherein determining, by the base station, satellite acquisition information comprising a set of GNSS satellites predicted to be visible at the estimated position of the mobile station comprises determining the set of GNSS satellites based at least in part on reducing or minimizing a spread of precision factor.

In aspect 44, the method of any one of aspects 34 to 43, wherein determining, by the mobile station, from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some GNSS satellites in the set comprises calculating a quality indicator of the at least some GNSS satellites in the set, the quality indicator being associated with a quality of the GNSS signals received by the mobile station.

In aspect 45, the method as in aspect 44, wherein the quality indicator comprises information associated with one or more of GNSS signal power, peak width in correlator output, or signal to noise ratio.

In aspect 46, the method of any of aspects 34 to 45, further comprising: exchanging clock timing information over an RF link between a mobile station and a base station; and synchronizing, by the mobile station, the mobile station clock to a base station clock representing a time of the GNSS satellite based at least in part on the timing information.

In aspect 47, the method of any of aspects 34 to 46, further comprising: synchronizing a mobile station clock with a link repeater clock between the mobile station and the link repeater; and synchronizing the link repeater clock with a base station clock representing the time of the GNSS satellite between the link repeater and the base station.

In aspect 48, the method of any of aspects 34 to 47, further comprising: obtaining navigation information from a pseudolite by a mobile station; determining, by the mobile station, a pseudolite chip transition time associated with the navigation information; communicating the pseudolite chip transition time over an RF link by a mobile station to a base station; and determining, by the base station, an updated position of the mobile station based at least in part on the pseudolite chip transition time.

In aspect 49, the method of aspect 48, wherein the navigation signal is at a pseudolite carrier frequency within a GNSS satellite signal carrier frequency range of 100 MHz.

In aspect 50, the method of aspect 49, wherein the pseudolite carrier frequency is in a range of 1626.5MHz to 1645.5 MHz.

In aspect 51, the method of any of aspects 34 to 50, wherein determining, by the mobile station from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some of the GNSS satellites in the set comprises searching for chip transitions within a shift window based at least in part on an estimate of an error in clock synchronization between the mobile station and the base station. In other aspects, the method as in any of aspects 34 to 51 is such that the base station comprises a mains powered supply and the mobile station comprises a non-mains powered supply. The non-mains power supply can include a battery, a capacitor (e.g., a supercapacitor), or a solar cell.

In aspect 52, a positioning system for a movable object, the positioning system using a Global Navigation Satellite System (GNSS), and the positioning system comprising: a mobile station configured to be associated with a movable object, the mobile station comprising: a mobile GNSS receiver configured to receive GNSS signals; a mobile transceiver configured to communicate over a communication link including frequencies in an unlicensed Radio Frequency (RF) band; a non-transitory data store configured to store computer-executable instructions; and a hardware processor coupled to the non-transitory data storage, wherein the computer executable instructions, when executed by the hardware processor, cause the mobile station to: wake up at a time specified in the sleep parameters or under one or more conditions specified; estimating a position of the mobile station; transmitting, via the mobile transceiver, the estimated position of the mobile station and the local mobile clock value to the base station; receiving information associated with a GNSS clock and acquisition parameters from a base station; updating a local mobile clock value based at least in part on information associated with the GNSS clock; causing a mobile GNSS receiver to acquire GNSS signals based at least in part on the acquisition parameters; transmitting information related to chip transitions in the acquired GNSS signals to a base station; receiving, from a base station, an updated location and information associated with updated sleep parameters; updating the sleep parameter based at least in part on information associated with the updated sleep parameter from the base station; and returns to sleep. The positioning system further comprises a base station, the base station comprising: a base GNSS receiver configured to receive signals from a plurality of GNSS satellites; a base transceiver station configured to communicate over a communication link that includes frequencies in the unlicensed Radio Frequency (RF) band; a non-transitory data store configured to store computer-executable instructions; and a hardware processor coupled to the non-transitory data storage, wherein the computer executable instructions, when executed by the hardware processor, cause the base station to: receiving an estimated position of the mobile station and a local clock value over the communication link; transmitting one or more messages associated with updating a local mobile station clock value to a base station clock value representative of time of a GNSS satellite; estimating acquisition parameters for the GNSS satellites based at least in part on the estimated position of the mobile station; transmitting an ordered list of GNSS satellites with associated code phase information to the mobile station via the communication link; receiving chip conversions from a mobile receiver via the communication link; calculating an updated position of the mobile station using at least the chip transitions from the mobile receiver; and transmitting the updated location and information associated with the updated sleep parameters to the mobile station.

In aspect 53, the positioning system of aspect 52, wherein the mobile station comprises one or more non-GNSS sensors, the non-GNSS sensors comprising a Very Low Frequency (VLF) sensor, a rotation sensor, a vibration sensor, a heading sensor, a magnetic field sensor, an optical sensor, an RF sensor, an Electronic Article Surveillance (EAS) sensor, an ultrasonic sensor, an accelerometer, or a gyroscope.

In aspect 54, the positioning system of aspect 53, wherein the mobile station is configured to estimate its initial position after exiting the sleep mode based at least in part on information provided by the one or more non-GNSS position sensors.

In aspect 55, a method for positioning a movable object, the method comprising: under control of a mobile station configured to be attached to or included in or on a movable object, the mobile station includes a Global Navigation Satellite System (GNSS) receiver and transceiver configured to communicate bi-directionally over an Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication: determining an estimated position of the mobile station by non-GNSS techniques; communicating the estimated position of the mobile station over the RF link; receiving over an RF link satellite acquisition information comprising a set of GNSS satellites predicted to be visible at an estimated position of the mobile station and a GNSS code phase associated with each GNSS satellite in the set; obtaining GNSS signals from at least some of the set of GNSS satellites; determining, at least in part, from the acquired GNSS signals, chip transition time information associated with GNSS code phases of the at least some GNSS satellites in the set; communicating chip transition time information over the RF link; and receiving an updated position of the mobile station over the RF link, the updated position determined based at least in part on the chip transition time information.

In aspect 56, the method of aspect 55, wherein determining the estimated position of the mobile station via non-GNSS technology comprises determining the estimated position via dead reckoning.

In aspect 57, the method of aspect 55 or aspect 56 further comprises: the clock of the mobile station is synchronized to a clock representing the time of the GNSS satellites.

In aspect 58, the method of any of aspects 55 to 57, wherein determining chip transition time information associated with the GNSS code phases of the at least some GNSS satellites in the set comprises calculating a quality indicator for the at least some GNSS satellites in the set, the quality indicator being associated with a quality of a GNSS signal received by the mobile station.

In aspect 59, the method as in aspect 58, wherein the quality indicator comprises information associated with one or more of GNSS signal power, peak width in correlator output, or signal to noise ratio.

In aspect 60, the method of any of aspects 55 to 59 further comprises: acquiring a navigation signal from a pseudolite; determining a pseudolite chip transition time associated with the navigation signal; and communicating the pseudolite chip transition time over the RF link.

In aspect 61, the method of any of aspects 55 to 60 further comprises: if the mobile station is not capable of communicating over the RF link, a position is determined from GNSS signals from the GNSS satellites.

In aspect 62, the method of any of aspects 55 to 61, wherein determining the chip transition time information comprises searching for a chip transition within a shift window based at least in part on an estimate of an error in clock synchronization.

In aspect 63, a mobile station configured to be attached to or included in or on a movable object, the mobile station comprising a Global Navigation Satellite System (GNSS) receiver and transceiver configured to communicate bi-directionally over an Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication, the mobile station configured to perform the method of any of aspects 55-62.

In aspect 55, a method for positioning a movable object, the method comprising: under control of a base station comprising a Global Navigation Satellite System (GNSS) receiver and transceiver configured to communicate bi-directionally over a Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication: receiving an estimated position of a movable object over an RF link; determining satellite acquisition information comprising a set of Global Navigation Satellite System (GNSS) satellites predicted to be visible at an estimated position of the movable object and a GNSS code phase associated with each GNSS satellite in the set; communicating the satellite acquisition information over an RF link; receiving chip transition time information associated with acquiring GNSS code phases from at least some of the GNSS satellites in the set over an RF link; communicating chip transition time information over the RF link; determining an updated position of the movable object based at least in part on the chip transition time information; and communicating the updated location over the RF link.

In aspect 65, the method of aspect 64 further comprises synchronizing a clock of the base station to a clock associated with the GNSS satellite.

In aspect 66, the method of aspect 64 or aspect 65, further comprising queuing the set of GNSS satellites according to one or more ordering criteria.

In aspect 67, the method of aspect 66, wherein the ranking criteria comprises one or more of: whether the satellite is along a direction of movement or a direction of interest of the movable object, whether the satellite is near the horizon of the movable object, the height of the satellite above the horizon of the movable object, the doppler shift of the satellite, the ionospheric propagation error of the satellite, the positional proximity information of at least two satellites, the antenna pattern of a GNSS antenna of the mobile station, or an obstacle present near the movable object that can inhibit reception of GNSS signals from the satellite.

In aspect 68, the system of any of aspects 64-67, wherein determining satellite acquisition information includes determining selection information associated with an order in which to attempt to acquire GNSS signals from satellites in the set of GNSS satellites.

In aspect 69, the method of any of aspects 64-68, wherein determining satellite acquisition information comprises determining a set of GNSS satellites based at least in part on reducing or minimizing a spread factor of precision.

In aspect 70, a base station comprising a Global Navigation Satellite System (GNSS) receiver and transceiver configured to bidirectionally communicate over a Radio Frequency (RF) link having an RF link frequency in an RF band unlicensed for cellular communication, the base station configured to perform the method of any of aspects 64-69.

In aspect 71, a system for analyzing satellite acquisition data, the system comprising: a non-transitory data storage configured to store satellite acquisition data related to attempts by a mobile station that is capable of moving in a tracking area to acquire signals from Global Navigation Satellite System (GNSS) satellites; and, a hardware processor in communication with the non-transitory data storage, the hardware processor programmed to: analyzing the satellite acquisition data using a machine learning algorithm; and, analyzing, based at least in part on the machine learning, one or more of: a module for updating the tracking area, or a GNSS radio selection criteria for the mobile station.

In aspect 72, the system of aspect 71, wherein the hardware processor is programmed to access Geographic Information System (GIS) information for the tracking area.

In aspect 73, the system of aspect 71 or aspect 72, wherein the hardware processor is programmed to infer from the machine learning analysis the presence of an obstacle that prevents reception of GNSS satellite signals at a particular location in the tracking area or in a particular direction.

In aspect 74, a pseudolite for communicating navigation information includes a transmitter configured to communicate a navigation signal at a pseudolite carrier frequency within a 100MHz Global Navigation Satellite System (GNSS) satellite signal carrier frequency.

In aspect 75, the pseudolite of aspect 74, wherein the pseudolite carrier frequency is in a range of 1626.5MHz to 1645.5 MHz.

In aspect 76, a pseudolite as in aspect 74 or aspect 75, wherein the navigation signal includes a timing code modulated onto a pseudolite carrier frequency.

In aspect 77, the pseudolite of aspect 76, wherein the timing code comprises a pseudorandom noise (PRN) code.

In aspect 78, a receiver configured to operate with the pseudolite of any one of aspects 74-77, wherein the receiver comprises circuitry configured to receive both a GNSS satellite signal carrier frequency and a pseudolite carrier frequency.

In aspect 79, the receiver of aspect 78, wherein the GNSS satellite signal carrier frequency is in the 1560MHz to 1590MHz range and the pseudolite carrier frequency is in the 1626.5MHz to 1645.5MHz range.

Other information

The various illustrative logical blocks, modules, and processes described herein may be implemented or performed with a machine such as a computer, processor, Digital Signal Processor (DSP), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor may be a microprocessor, a controller, a microcontroller, a state machine, a combination thereof, or the like. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors or processor cores, one or more graphics or streaming processors, one or more microprocessors in conjunction with a DSP, or any other such configuration.

Furthermore, certain embodiments of the subject object positioning system of the present disclosure may be mathematically, computationally, or technically complex enough, for example, to apply dedicated hardware (e.g., FPGA or ASIC) or one or more physical computing devices (using appropriate executable instructions) to perform functions due to the computational effort or complexity involved (e.g., analyzing GNSS captured data or object position information collected from a large number of movable objects) or providing results (e.g., statistical information about object positions) in substantially real-time.

The states of the blocks or processes described herein may be embodied directly in hardware, in a software module stored in a non-transitory memory and executed by a hardware processor, or in a combination of the two. For example, each of the processes described above may also be embodied directly in, or fully automated by, a software module (stored in memory) executed by one or more machines, such as a computer or a computer processor. A module may reside in non-transitory computer readable medium such as RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, optical disk, memory capable of storing firmware, or any other form of computer readable (e.g., storage) medium. A computer readable medium can be coupled to the processor such that the processor can read information from, and write information to, the computer readable medium. In the alternative, the computer readable medium may be part of the processor. The processor and the computer readable medium may reside in an ASIC. The computer-readable medium may include non-transitory data storage (e.g., hard disk, non-volatile memory, etc.).

The processes, methods, and systems may be implemented in a networked (or distributed) computing environment. For example, a central control unit or base station may be implemented in a distributed, networked computing environment. Network environments include enterprise-wide computer networks, intranets, Local Area Networks (LANs), Wide Area Networks (WANs), Personal Area Networks (PANs), cloud computing networks, crowd-sourced computing networks, the internet, and the world wide web. The network may be a wired or wireless network, a terrestrial or satellite network, or any other type of communication network.

Depending on the embodiment, certain actions, events, or functions of any process or method described herein may be performed in a different order, may be added, merged, or eliminated altogether. Thus, in some embodiments, not all described acts or events are required to implement the process. Further, in some embodiments, actions or events may be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or via multiple processors or multiple processor cores, rather than sequentially. No element or act is essential or essential to all embodiments in any device, system, or method, and the disclosed devices, systems, and methods can be arranged in other ways than shown or described.

Unless specifically stated otherwise, or otherwise understood in the context of usage, conditional language, e.g., "can or result," may or may not (light or may), "(e.g., (e.g.)", etc., as used herein, is generally intended to mean that certain embodiments include certain features, elements, and/or states, but other embodiments do not. Thus, such conditional language is not generally intended to imply that features, elements, and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether such features, elements, and/or states are included or are to be performed in any particular embodiment. The terms "comprising" or "including", "having", and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude other elements, features, acts, operations, and the like. Furthermore, the term "or" is used in an inclusive sense (and not in an exclusive sense), so that when used, for example, to connect a list of elements, the term "or" refers to one, some, or all of the list of elements.

Unless expressly stated otherwise, or otherwise understood in the context of usage, joint language such as the phrase "X, Y and at least one of Z" is used generically to express that an item, term, etc. may be X, Y or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present. When referring to an element, the article "a" or "an" or "the" refers to one or more of the element, unless the context clearly dictates otherwise.

While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the logical blocks, modules, and processes illustrated may be made without departing from the spirit of the disclosure. As will be recognized, certain embodiments of the present invention described herein may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others.