阅读说明：本技术 用无线信号进行精确的短程定位 (Accurate short range positioning with wireless signals ) 是由 C·拉比 于 2017-10-03 设计创作，主要内容包括：在无线通信网络中的通信设备的定位确定由定位设备支持,定位设备接收[230]来自主定位蜂窝小区的紧密同步信号；从中确定[232]它们的实际到达时间与理论到达时间之间的多个时间差；基于由所述时间差调整的接收到的紧密同步信号同步[234]定位蜂窝小区时钟；以及在由所述同步确定的时间处,向所述通信设备发射[236]定位信号。所述定位信号包括所述定位蜂窝小区的标识符,并且所述定位信号以不干扰由所述无线通信网络发送的定位导频信号的方式发送。所述定位设备可以替代地从另一定位蜂窝小区而不是主定位蜂窝小区接收同步信号。(Location determination of a communication device in a wireless communication network is supported by a positioning device, the positioning device receiving [230] a tight synchronization signal from a primary positioning cell; determining [232] therefrom a plurality of time differences between their actual arrival times and theoretical arrival times; synchronizing [234] a positioning cell clock based on the received tight synchronization signal adjusted by the time difference; and transmitting [236] a positioning signal to the communication device at a time determined by the synchronization. The positioning signal includes an identifier of the positioning cell and is transmitted in a manner that does not interfere with a positioning pilot signal transmitted by the wireless communication network. The positioning device may alternatively receive a synchronization signal from another positioning cell instead of the primary positioning cell.)

1. A method implemented by a positioning cell for supporting positioning determination of a communication device in a wireless communication network, the method comprising:

receiving, by the positioning cell, a plurality of close synchronization signals from a primary positioning cell;

determining, by the positioning cell, a plurality of time differences between arrival times of the plurality of close synchronization signals and theoretical arrival times of the plurality of close synchronization signals, wherein the theoretical arrival times are corrected by theoretical time-of-flight along a direct line-of-sight path from the primary positioning cell to the positioning cell;

synchronizing the positioning cell based on one or more of the received close synchronization signals adjusted by one or more of the plurality of time differences, wherein the synchronizing comprises synchronizing clocks in the positioning cell;

transmitting, by the positioning cell, a positioning signal to the communication device in the wireless communication network at a time determined by the synchronized clock; wherein the positioning signal comprises data indicating an identifier of the positioning cell; wherein the positioning signals are transmitted in a manner that does not interfere with positioning pilot signals transmitted by the wireless communication network.

2. The method of claim 1, wherein the plurality of close synchronization signals received from the primary positioning cell are synchronized by the primary positioning cell to a synchronization signal from another primary positioning cell, a cellular network, a WiFi network, or a satellite navigation system.

3. The method of claim 1, wherein the data indicating the identifier of the positioning cell comprises a local Physical Cell Identity (PCI) and no global cell identity.

4. The method of claim 1, wherein the transmission of the positioning signal uses multiplexing such that the positioning signal is orthogonal to a pilot signal sent by the wireless network.

5. The method of claim 1, further comprising: receiving, by the positioning cell from the primary positioning cell, data indicative of a time difference between a measured arrival time of the positioning signal at the primary positioning cell and a theoretical arrival time of the positioning signal at the primary positioning cell; and

determining, by the positioning cell from the data indicative of time difference, an adjustment in transmission timing of a subsequent positioning signal from the positioning cell.

6. A method implemented by a positioning cell for supporting positioning determination of a communication device in a wireless communication network, the method comprising:

receiving, by the positioning cell, a close synchronization signal from a first positioning cell, wherein the close synchronization signal is synchronized by the first positioning cell to a close synchronization signal received by the first positioning cell from a primary positioning cell synchronized to a cellular network, a WiFi network, or a satellite navigation system;

transmitting, by the positioning cell, a positioning signal to the communication device in the wireless communication network after a predetermined time period after reception of the received synchronization signal; wherein the positioning signal comprises data or timing indicating an identifier of the positioning cell.

7. The method of claim 6, wherein the positioning signal is transmitted in a manner that does not interfere with a positioning pilot signal transmitted by the wireless communication network.

Technical Field

The present invention relates generally to techniques for locating wireless communication devices using RF electromagnetic waves. More particularly, the present invention relates to a technique for positioning using positioning signals from a plurality of positioning cells.

Background

There are many applications for accurately locating wireless communication devices in a room or place (e.g., a store or mall, stadium, parking lot, building, business, factory). Most solutions today use bluetooth, WiFi, UBW (ultra wide band), cameras or motion sensors. All these solutions have drawbacks, however, for example, a typical accuracy of not more than 5 m.

Disclosure of Invention

In one aspect, the present invention provides a method implemented by a positioning cell for supporting a positioning determination of a communication device in a wireless communication network. The method comprises the following steps: receiving, by the positioning cell, a plurality of close synchronization signals from a primary positioning cell; determining, by the positioning cell, a plurality of time differences between arrival times of the plurality of close synchronization signals and theoretical arrival times of the plurality of close synchronization signals, wherein the theoretical arrival times are corrected by theoretical time-of-flight along a direct line-of-sight path from the primary positioning cell to the positioning cell; synchronizing the positioning cell based on one or more of the received close synchronization signals adjusted by one or more of the plurality of time differences, wherein the synchronizing comprises synchronizing clocks in the positioning cell; and transmitting, by the positioning cell, a positioning signal to the communication device in the wireless network at a time determined by the synchronized clock, wherein the positioning signal includes data indicative of an identifier of the positioning cell, and wherein the positioning signal is transmitted in a manner that does not interfere with a positioning pilot signal transmitted by the wireless network.

Preferably, the plurality of close synchronization signals received from the primary positioning cell are synchronized by the primary positioning cell to a synchronization signal from another primary positioning cell, a cellular network, a WiFi network, or a satellite navigation system. Optionally, the data indicating the identifier of the positioning cell comprises a local Physical Cell Identity (PCI) and no global cell identity. Preferably, the transmission of the positioning signal uses multiplexing such that the positioning signal is orthogonal to a pilot signal sent by the wireless network.

The method may further comprise: receiving, by the positioning cell from the primary positioning cell, data indicative of a time difference between a measured arrival time of the positioning signal at the primary positioning cell and a theoretical arrival time of the positioning signal at the primary positioning cell; and determining, by the positioning cell from the data indicative of the time difference, an adjustment in transmission timing of a subsequent positioning signal from the positioning cell.

In another aspect, the present invention provides a method implemented by a positioning cell for supporting a positioning determination of a communication device in a wireless communication network. The method comprises the following steps: receiving, by the positioning cell, a synchronization signal from a first positioning cell, wherein the synchronization signal is synchronized by the first positioning cell to a tight synchronization signal received by the first positioning cell from a primary positioning cell synchronized to a cellular network, a WiFi network, or a satellite navigation system; and transmitting, by the positioning cell, a positioning signal to the communication device in the wireless network after a predetermined time period after reception of the received synchronization signal, wherein the positioning signal comprises data or timing indicating an identifier of the positioning cell. Preferably, the positioning signal is transmitted in a manner that does not interfere with a positioning pilot signal transmitted by the wireless network.

Drawings

Fig. 1 is a block diagram illustrating locating a cell in accordance with some embodiments of the present invention;

FIG. 2 is a flow chart summarizing a method implemented by a positioning cell for supporting positioning determination of a communication device in a wireless communication network

FIG. 3 is a block diagram illustrating a system for locating a communication device connected to a cloud in accordance with some embodiments of the present invention;

fig. 4A is a schematic diagram showing a set of positioning cells in a venue where we place some positioning cells in line of sight (close to line of sight) relative to other positioning cells in order to achieve close synchronization between all positioning cells, according to some embodiments of the invention;

fig. 4B is a schematic diagram illustrating minimum conditions in terms of line-of-sight visibility between positioning cells allowing tight synchronization, according to some embodiments of the invention;

fig. 4C is a schematic diagram illustrating another example of a minimum condition in terms of line-of-sight visibility between positioning cells that allow tight synchronization, according to some embodiments of the invention;

fig. 4D is a generic transmission diagram of a close synchronization signal (between positioning cells) and a positioning signal (towards the communication device) according to some embodiments of the invention;

FIG. 4E is a diagram illustrating a method of unifying close synchronization and positioning signals, according to some embodiments of the present invention;

FIG. 4F is a timing diagram illustrating a method of performing tight synchronization in a first phase (which is later a positioning signal), according to some embodiments of the invention;

FIG. 4G is a graph showing how the cells in FIG. 4F may be connected geographically from the point of view of L oS.

Fig. 5 is a flow diagram illustrating a state machine for locating cells in accordance with some embodiments of the invention.

Fig. 6 is a flow diagram illustrating a state machine of a communication device according to some embodiments of the invention.

Fig. 7 is a schematic diagram showing the transmission of tight synchronization and positioning signals, and the expected time drift before accurate synchronization and calibration is achieved.

The drawings are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It is to be understood that the invention can be practiced with modification and alteration, and that the invention be limited only by the claims and the equivalents thereof.

Detailed Description

Embodiments of the present invention may be implemented and deployed in connection with various different existing wireless communication or positioning systems. Possibilities include cellular networks using licensed spectrum, WiFi or Bluetooth (Bluetooth) networks using unlicensed spectrum, or satellite navigation systems. Although such examples will be used herein to describe embodiments of the invention for purposes of illustration, those skilled in the art will recognize that the invention is not limited to these specific examples. After reading this description, those skilled in the art will understand how the present invention may be implemented in different and alternative wireless environments.

The use of cellular technology for positioning may be advantageous because cellular networks are always on-line, have low power consumption, low interference, and may be controlled by the operator observed time difference of arrival (OTDOA) positioning is a known method that provides a positioning accuracy of 20m-200m however, there is no reliable accuracy less than 10 meters, may be provided indoors and outdoors everywhere, and is scalable indoor or location based cellular or other positioning solutions.

In some embodiments of the invention, (3G or 4G) cellular observed time difference of arrival (OTDOA) positioning is enhanced by increasing the number of virtual cell sites, by adding additional positioning cells. A positioning cell is a femtocell (femtocell) that transmits a special positioning beacon, but does not necessarily provide other forms of cellular service as a typical base station or access point does. These positioning cells automatically learn the identity and synchronization of the cellular networks around them, automatically configure themselves (by means of the network, configuration equipment and configuration server), and then transmit their own positioning beacons only during the time intervals in which the cellular phone listens for positioning beacons from the cellular network, without interfering with the network. Such positioning beacons may be referred to by other terms in different contexts, for example, they may be referred to as p-beacons, positioning pilots (positioning pilots), or positioning signals.

The connection between the positioning cell and the cellular network may be direct or mediated through a configuration device 206 (fig. 3) connected to the cellular network; for example, a cell phone or another locating cell, and uses WiFi, bluetooth, or cellular connectivity. The communication between the positioning cell and the communication device 202 used by the user to obtain the user's location may be in a licensed spectrum of the cellular network or in an unlicensed spectrum.

Thus, an aspect of some embodiments of the invention relates to a positioning system configured for use with the location solver 204 and the communication device 202 synchronized with the cellular network, wherein the positioning system comprises a plurality of positioning cells. Each positioning cell includes a transceiver configured to transmit and receive radio frequency signals, a memory unit configured to store data, and a processing unit configured to process the data and to control operation of the transceiver. At least one of the positioning cells is connected to or can hear the cellular network, and the positioning cell is configured to transmit a corresponding positioning signal (i.e., a positioning pilot, or a positioning beacon) that can be received by the communication device 202 in a frequency used by the cellular network. The positioning cell is also configured to receive a synchronization signal transmitted by the cellular network. The synchronization signal is a signal from the cellular network that enables a device or positioning cell to roughly or tightly synchronize with the transmitting macrocell 220 and locate a time slot at which the positioning cell can safely transmit without interfering with the cellular network. The synchronization signals preferably include cell primary or secondary synchronization signals, cell reference signals, cell positioning signals (pilots), broadcast or multicast information to identify and locate various signals and time slots. Coarse synchronization is on the order of 100ns to 1000ns, while tight synchronization is on the order of 3ns to 30 ns. Each positioning signal includes data indicating an identifier of the positioning cell that transmitted the positioning signal. The position solver 204 may be part of the communication device or a separate device, with the position solver 204 being in communication with the communication device 202. The position resolver is configured to: (i) receiving first data from the communication device 202 indicating an arrival time of a positioning signal to the communication device 202, each data indicating an arrival time being appended with an identifier of an associated positioning cell; (ii) processing the time of arrival and using the known location of the positioning cell to determine the location of the communication device 202 relative to the positioning cell, e.g., using multilateration; and (iii) send second data indicative of the location to the communication device 202, or to an application in the cloud 210.

Optionally, the positioning cells are associated with respective Physical Cell Identities (PCIs), the positioning cells not necessarily having a global cell identity in the cellular network.

Preferably, the positioning signals are designed such that they do not interfere with the cellular network. For example, the positioning signal may comprise a first positioning signal orthogonal in the time domain to a positioning pilot of the cellular network; a second positioning signal orthogonal to a positioning pilot of the cellular network in the frequency domain; and/or a third positioning signal transmitted during a gap when no positioning pilot or other data is transmitted by a macro cell of a nearby cellular network, wherein preferably the third positioning signal has a transmit power below a threshold power so as not to drown out positioning pilots transmitted by any further macro cells at the same time.

Preferably, prior to receiving the synchronization signal, the positioning cell is configured to perform an analysis of the cellular network and to synchronize with the cellular network based on the analysis in order to determine an appropriate timing for reception at each period for a respective time interval within which the cellular synchronization signal is expected to arrive at the respective positioning cell. Locating a cell may further improve its accuracy of synchronization with the cellular system by: using cellular positioning signals or cell reference signals and correcting for known distances from the cellular network macrocell 220 (we mean with macrocell a cellular communication network cell, which may be a macrocell, picocell or small cell, capable of transmitting positioning signals and deployed by a cellular network operator but which is not a positioning cell that is the subject of this application; macrocell may also mean an access point, satellite transceiver or other transceiver from a general wireless network). Alternatively, they may be roughly synchronized to the cellular system by: using a less accurate signal, such as a primary or secondary synchronization signal, or not correcting for distance to the macrocell. Preferably, at least one positioning cell (such as a primary positioning cell) should perform this operation and roughly or closely synchronize to the cellular network in order to locate the time slot allocated for transmitting the positioning signal without interfering with the cellular network. The location cell of the customizable software may be selected as the master or slave device by the installer automatically or manually. Such a positioning cell selected as the primary cell is preferably centered to some extent in most other positioning cells, or so that it can hear the cellular network. The remaining positioning cells will then closely synchronize with the primary positioning cell. Coarse synchronization with the cellular network and tight synchronization between locating cells are typically performed wirelessly, but may also be performed using a wired connection.

Optionally, the positioning cell configuration is used to analyze the cellular network by: receiving a plurality of synchronization signals from a plurality of multi-operator cells of a cellular network; the arrival times of the plurality of signals are averaged using predetermined information indicative of the distance traveled by each of the plurality of synchronization signals and a constant timing offset between the synchronization signals associated with different operators and frequency bands.

Optionally, the positioning cell configuration is used to analyze the cellular network by: a predetermined filter is applied to the plurality of synchronization signals to reduce the effect of fluctuations in the synchronization of the macro cells of the cellular network.

The positioning cell may be configured to transmit positioning signals in a spectrum of a given operator in the cellular network, in a spectrum of multiple operators in the cellular network, and/or in an unlicensed spectrum in the cellular network that is not associated with any operator.

Optionally, the positioning cell is configured to initially connect to the configuration device 206 without using the cellular network, receive information about the cellular network from the configuration device 206, and only subsequently listen to the cellular network based on the received information about the cellular network.

Optionally, each positioning cell periodically transmits a positioning pilot at a predetermined period (e.g., 1 second or 10 seconds). The communication device stores predetermined periods and configurations and can thus listen for a positioning pilot during a short interval of each period without requiring a search phase for a positioning signal. This period may be the same on all sites where the system is used and is substantially synchronized with some common time. Alternatively, each site may be assigned a different time slot within the cycle in order to increase the capacity to locate cells. Any operator wishing to use the system should have synchronized networks, i.e. synchronized macro cells. In addition, an operator may instruct its users to listen to the positioning signals of another operator (if both operators have an agreement), or the operator may instruct its users to listen to positioning signals transmitted in unlicensed frequency bands.

Optionally, any given positioning cell is configured to listen to at least one previous positioning cell (i.e., a positioning cell that was transmitted earlier in the current positioning opportunity); determining a time difference between the arrival time of a positioning signal (or close synchronization signal) transmitted by a previous positioning cell and a theoretical arrival time that would occur if the positioning signal transmitted by the previous positioning cell took the shortest path from the previous positioning cell to the given positioning cell; and transmitting the respective positioning signal a time interval after receiving the positioning signal of the previous positioning cell, said time interval being equal to the predetermined transmission timing minus the time difference.

Optionally, a given positioning cell is configured to determine a time difference less a shortest path distance between the positioning cell and a previous positioning cell provided by, for example, server 204.

Optionally, the positioning cells are divided into groups; positioning cells belonging to any same group are configured to transmit respective positioning signals at the same time, which is different from the time when cells in other groups transmit their positioning signals; the cells of each group of positioning cells are configured to transmit respective positioning signals simultaneously with other positioning cells in the same group, or in rapid succession at respective times after the synchronization signal; any group of first positioning cells is configured to listen for second positioning signals transmitted by a different group of second positioning cells; the first positioning cell is configured to determine a time difference between a time of arrival of a second positioning signal at the first positioning cell and a corresponding theoretical time of arrival that would occur if the second positioning cell were synchronized with the first unit cell; the first positioning cell is configured to transmit data indicating a difference with the second positioning cell, either wired or wirelessly; the second positioning cell is configured to adjust a transmission timing of the second positioning signal according to the difference so as to synchronize with the first positioning cell. In some embodiments, there may be more than one first positioning cell and more than one second positioning cell.

Optionally, the plurality of first positioning cells are configured to receive at least some of the second positioning signals transmitted by the second positioning cells, the first positioning cells belonging to the same first group or a plurality of different first groups; the first positioning cell is configured for creating a plurality of respective time difference maps (maps) between times of arrival of second positioning signals and respective theoretical times of arrival that would occur if the second positioning cell were synchronized with the first positioning cell; the first positioning cell is configured to send data indicative of the respective map to at least some of the second positioning cells, either wired or wirelessly; each second positioning cell is configured for receiving a plurality of maps and for extracting therefrom respective data relating to time differences associated with second positioning signals transmitted by the second positioning cell relative to the plurality of first positioning cells; each second positioning cell is configured to process data extracted from the plurality of maps to determine a respective adjustment in a respective transmission timing of a particular positioning signal to synchronize with the plurality of second positioning cells in a current cycle or in a subsequent cycle and to synchronize with the plurality of first positioning cells.

Optionally, the map comprises information representative of the quality of positioning signals transmitted by some of the second positioning cells; and each second positioning cell is configured to determine the respective adjustment by calculating a weighted average of time differences relative to the plurality of first positioning cells, each weight applied to a time difference being a measure of the quality of the positioning signal associated with the time difference.

Optionally, each first positioning cell is configured to receive at least some second positioning signals transmitted by at least some second positioning cells, which do not belong to the group of first positioning cells. Optionally, at least one group consists of a single positioning cell. Optionally, the at least one group consists of two or more positioning cells. Optionally, a given positioning cell is allocated to more than one group.

Optionally, the at least one first positioning cell is configured to determine the time difference by one of: having access to a distance of shortest path from at least one second positioning cell and calculating a time difference; the time of arrival of the second positioning cell is relayed to a configuration device or a configuration server and the time difference is received from the configuration device or the configuration server.

Optionally, each first positioning cell is configured to determine the map by one of: having access to information indicative of distances of the first positioning cell from at least some of the second positioning cells and calculating a time difference between a time of arrival of the second positioning signal and a corresponding theoretical time of arrival that would occur if the second positioning cell were synchronized with the first positioning cell; the time of arrival of the second positioning cell is relayed to a configuration device or a configuration server and the map is received from the configuration device or the configuration server.

Optionally, (i) the first positioning cell is a primary positioning cell synchronized with the cellular network, the primary positioning cell configured to transmit a close synchronization signal every cycle in response to receipt of the synchronization signal every cycle (400D in fig. 4D). A close synchronization signal from a master positioning cell or a slave positioning cell is a signal that enables close synchronization between the master positioning cell and the slave positioning cell and is transmitted in the same frequency band or a different frequency band, in a licensed or unlicensed frequency band; the tight synchronization signal 400d may be a positioning pilot 402d of the master or slave positioning cell, or alternatively some reserved signal using a lower power or shorter burst; close synchronization enables synchronization to an accuracy of about 1 meter (i.e., about 3 ns). Additionally, (ii) the plurality of second positioning cells are slave positioning cells configured to turn on for a predetermined length of time at each cycle in order to listen for a close synchronization signal; receiving a tight synchronization signal; and transmitting a second positioning signal 402d a predetermined time period after receiving the close synchronization signal 400d such that the second positioning signal is received by the communication device 202 shortly after the communication device 202 receives the first positioning pilot while the communication device 202 is still listening; the idea is that the user does not wait too long between the master and slave positioning signals in order to save the battery; but more importantly, we have the following constraints: the slaves transmit relatively quickly after hearing the master beacon before their timing drifts. The drift may be a few meters per second or a few meters per 10 seconds. Therefore, the slave device should transmit shortly after the master device beacon. Additionally, (iii) the master positioning cell is configured to receive the slave positioning signal and compile a map of time differences between the arrival times of the slave positioning signal and corresponding theoretical arrival times that would occur if the slave positioning cell were synchronized with the first positioning master positioning cell; in this case, the master device does not transmit at the same time as the slave device. Additionally, (iv) the master positioning cell is configured to send data indicative of the map to the slave positioning cell; this calibrates the second positioning cells (slave positioning cells) with each other, but it does not calibrate the master positioning cell with the slave positioning cells. From time to time, another group should be formed in order to calibrate the primary positioning cell. Additionally, (v) each slave positioning cell is configured to extract respective information indicative of a respective adjustment to the transmission timing of a respective slave positioning signal for a subsequent period from data of the indication map; (vi) in a subsequent period, each slave positioning cell is configured to adjust the transmission time and to adjust the start and end of the predetermined length of time.

Optionally, the master positioning cell is in line of sight with all slave positioning cells.

As shown in 404D of fig. 4D, the positioning cells are provided with a time gap from the reception of the transmission between the reception of the close synchronization signal and the transmission of the positioning signal (or the transmission of another close synchronization signal) in order to allow them sufficient processing time between the reception of the signal and the transmission of their own signal after readjusting their synchronization.

Coarse synchronization, tight synchronization and RF calibration procedures

A primary positioning cell roughly synchronizes to the network and, with the aid of a configuration device and a configuration server, to locate a time slot in which the positioning cell may transmit in a licensed band without interfering with the cellular network, or a time slot in which it may transmit in a given licensed or unlicensed band at a given time that may be quickly located by a communication device without extensive searching.

The slave positioning cell obtains this coarse synchronization by listening for messages in the licensed or unlicensed spectrum from the master positioning cell or by listening to the cellular network; and they obtain the remaining configurations from the configuration device and the configuration server.

Less than one second (ideally 1ms to 100ms before) before the positioning cells transmit their positioning signals, the master positioning cell 410 transmits a tight synchronization signal 406, one or more first slave positioning cells 412a, 412b (as shown in fig. 4A) in the direct line of Sight (L ine-of-Sight) (L oS) to the master positioning cell will hear the tight synchronization signal 406, these first slave positioning cells 412a, 412b will estimate their arrival times, will subtract the theoretical time of flight of the signal, will learn how much their clocks are shifted relative to the signal, and will then adjust their clocks to realign with the signal and resynchronize with the master positioning cell.

Within milliseconds after re-synchronizing their clocks, the first slave positioning cells 412a, 412b will in turn send tight synchronization signals, preferably that will be heard by one or more second slave positioning cells 414a, 414b, 414c in direct L oS to the first slave positioning cell, will estimate their time of arrival, will subtract the theoretical time of flight of the signals, will learn how much their clocks drift with respect to the signals, and will then adjust their clocks to realign with the signals and re-synchronize with the master positioning cell.

And so on until all slave positioning cells are synchronized with the master positioning cell. At this stage, all positioning cells will transmit positioning signals in the same or different frequency band as the closely synchronized frequency band simultaneously or in quick succession, less than 1 second before their clocks drift. Alternatively, the close synchronization signal itself is a positioning signal and does not require retransmission of the positioning signal.

In order for the tight synchronization process to work during the preliminary initialization process, the configuration device and configuration server inform each positioning cell of its role and the positioning cell it should listen and synchronize, and the distance or time of flight to that positioning cell the transmitting positioning cell and the listening positioning cell will ideally be in direct L oS to get the best synchronization accuracy the configuration device and configuration server build a graph with L oS links and paths moving from the master positioning cell to each slave positioning cell like a tree starting from the master positioning cell and branching to a first set of slave positioning cells and then branching again to a second set of slave positioning cells, and so on until all slave positioning cells have been reached.

As shown in fig. 7, the master positioning cell 702 and the slave positioning cells i 704 and j 706 transmit a close synchronization signal or positioning signal 708. In this example, each positioning cell also listens to positioning cells that have been transmitted earlier. In this example, the transmission period 710 is an ideal time delay between transmissions of the cells and can be achieved once accurate synchronization and correction is performed. However, we observe time drift due to clock differences and RF differences between the hardware that locates the cells.

Let us assume that positioning cell j listens to positioning cell i in order to find its synchronization error. The general formula of the time of arrival estimate of the close synchronization or positioning signal received from positioning cell i measured by positioning cell j is:

t_ij＝d_ij+(τ_i+s_ib)-(τ_j-s_jb)+n_ij

wherein t is_ijIs the measured time of arrival of the tight synchronization signal sent by positioning cell i and received by positioning cell j. Tau is_i722 is a time reference in positioning cell i, and τ_j722 is a time reference in locating cell j. The time reference refers to the time reference 720 of the primary positioning cell (which τ is 0). Thus, τ_iAnd τ_jIs the accumulated drift relative to the previous positioning opportunity and will be recalibrated during each tight synchronization opportunity. s_ibRespectively, s_jb724, is a receive-to-transmit RF calibration error that adds to the time offset of the positioning cell i (respectively, positioning cell j) relative to the primary positioning cell, and the tight synchronization signal is transmitted on frequency band b, which depends on the TX and RX electronics, temperature, and frequency band b of each positioning cell. Tau is_xAnd s_x(where x is the index i or ib, etc.) the main difference between these is, for example, τ_xIs short term drift that varies due to clock and drift estimation inaccuracies, and s_xIs a long term drift with temperature change. Tau is_xShould be estimated in each cycle of, for example, 10 seconds. And s_xCan be estimated in each cycle of, for example, 1 hour. Furthermore, if the frequency band used by the close synchronization signal is different from the frequency band used by the positioning signal, s_xMay depend on the frequency band used by the close synchronization signal.

It is assumed that all the time amounts are normalized to distance by multiplying them by the speed of light. d_ijIs the distance the signal travels from positioning cell i to positioning cell j. n is_ijIs the estimated noise.

We will explain later how to determine s by locating the cell_ib、s_jb. We now assume that they are known. d_ijDetermined by the network installer, stored in the configuration server, and copied by the configuration server and the configuration device into the receiving positioning cell j. τ if the positioning cell i has been properly synchronized (earlier, before sufficient drift occurs again) to the primary positioning cell_i+s_ib＝0。t_ijIs estimated as the time of arrival of the tight synchronization signal. Ideally, n_ijIs a small noise that can be ignored under the L oS condition, therefore, locating cell j can be based on

τ_j≈t_ij-d_ij-s_jb

Its time reference is calculated and corrected. Its transmission will be aligned with the transmission of the primary positioning cell plus the desired time period.

The method further comprises calibrating the RF transceiver of the slave positioning cell with respect to the master positioning cell, i.e. estimating the quantity s for a given frequency band b with respect to the frequency band in which the positioning signal is transmitted_jbThe process is represented by RF calibration and may be implemented periodically or from time to time as the positioning cell transmits positioning signals in the desired frequency band, by having the positioning cell listen to a neighboring positioning cell, preferably in direct L oS (402 in fig. 4A, 4B, 4℃) in this context, a neighboring positioning cell is defined as a positioning cell that can be heard by the positioning cell of interest in direct L oS. a non-neighboring positioning cell is defined as a positioning cell that cannot be heard by the positioning cell of interest in direct line of sight, i.e. it is located in a non-line of sight (N L OS) and its signal may be blocked by obstacles or may suffer from multi-path interference (e.g. signal bouncing off a wall.) for example, each of fig. 4B, 4C, 4E, 4F shows a L oS path (straight dashed line) connecting a sequence of positioning cells (triangles representing positioning cells).

For example, fig. 4E shows an even group 482 and an odd group 481 fig. 4F shows an even group 484 and an odd group 485 fig. odd numbered cells may listen to neighboring even numbered positioning cells when they transmit positioning signals the latter and likewise even numbered cells may listen to neighboring odd numbered positioning cells when they transmit their positioning signals, in addition at least one even numbered positioning cell should be given the opportunity to listen to the positioning signal of at least one odd numbered positioning cell or vice versa and preferably have a direct L oS visibility 450 fig. 4G shows how the positioning cells in fig. 4F may be geographically connected from the point of view L oS this scheme is also shown in fig. 4D positioning signals 402D are first transmitted from odd numbered positioning cells (the odd numbered positioning cells listen to the positioning cells), from the odd numbered positioning cells to the remaining RF transmitting cells (the odd positioning cells are subsequently calibrated), and the remaining RF transmitting cells are subsequently monitored (from the odd positioning cells to the odd positioning cells).

The positioning signal need not start with the primary positioning cell, and the primary positioning cell may not necessarily play a particular role in the positioning signal (unless the positioning signal and the close synchronization signal are combined into the same signal). The master positioning cell plays an important role in the tight synchronization process because it defines the timing ticks that all slave positioning cells should accurately track. Furthermore, the slave positioning cell may not directly listen to the master positioning cell; it may listen to (intermediate) slave cells that are already closely synchronized with the master positioning cell.

Each positioning cell measures the time difference between the positioning signals of at least two neighboring positioning cells that it neighbors in direct L oS if a positioning cell is only neighboring one positioning cell in direct L oS, such cell cannot participate in the following process.

The estimation formula for the time of arrival of the signal sent by the positioning cell i, i' and received by the positioning cell j is given by:

t_ij＝d_ij+(τ_i+s_ib)-(τ_j+s_jb)+n_ij

wherein the amounts have been described above, and wherein_x+s_xIs the residual with respect to the correction that has been made so far. These residuals are equal to 0 if there is no drift and no change due to RF.

Subtracting the two formulas and ignoring the small noise yields:

(τ_i′+s_i′b)-(τ_i+s_ib)≈t_i′j-t_ij-d_i′j+d_ij＝∈_i′ij

right hand item ∈_i'ijIs a small drift error between positioning cells i and i' and is measured by positioning cell j. Term (tau)_i+s_ib)＝∈_iIs a small drift error that can be obtained recursively through the path connecting the primary positioning cell with positioning cell i, therefore, term ∈_iWill be corrected in a recursive manner (after correcting the terms of all previous positioning cells linking the positioning cell i to the primary positioning cell) and will converge to zero. Thus, the only remaining items are

(τ_i′+s_i′b)≈∈_i′ij

And may be estimated by positioning cell j and forwarded to positioning cell i' for correction. Since the positioning cell i' assumes it has corrected its own τ_i'Therefore, amount ∈_i'ijWill be equal to s_i'bAny variation in (a). Thus, positioning cell i' adds this amount to the memory for s_i'bInternal value of (cumulative correction). In case of estimation error, this value will be corrected at the next RF calibration opportunity. Therefore, it is preferable not to delay the next RF calibration opportunity significantly.

Initially, for the frequency band, quantity s_i'bMay be initialized to zero or a reasonable value. After the first RF calibration procedure, we determine its value for band b. Then we track its value, which typically changes slowly over time due to temperature changes. We can also measure its values for different frequency bands in which tight synchronization can occur.

Multipoint positioning procedure

As shown in fig. 6, the positioning process of the communication includes the steps of: 602 receiving positioning signals from a number of positioning cells and measuring a time of arrival of each positioning signal; 604 forwarding the measurements to a position resolver, the position resolver being positionable within the communications device; 606 the location solver performs a multilateration operation on the measurements to calculate the location of the communication device, which requires knowledge of the location of the positioning cells and the transmission time of each positioning cell; 608 sends the estimated location back to the communication device.

Close synchronization of multiple domains with at least one positioning cell in an intersection

Two or more cross-domains may optionally be tightly synchronized to improve the accuracy of the overall communication device.

Optionally, the system comprises a plurality of master positioning cells and a plurality of slave positioning cells, wherein: the primary positioning cells are configured for synchronizing with each other; after synchronization, the master positioning cell is configured to transmit a respective close synchronization signal at each cycle, and each slave positioning cell is configured to: receiving a plurality of close synchronization signals, calculating theoretical arrival times of the close synchronization signals by using respective known distances of the slave positioning cell from the master positioning cell; calculating a plurality of differences, each difference being a difference between a theoretical arrival time associated with a respective master device and an arrival time of a close synchronization signal of the respective master device; selecting the minimum reliability difference (where reliable means, for example, the lowest acceptable SNR level, or other lowest quality level, of the received signal); and transmitting the slave positioning signal a predetermined time after the arrival time of the close synchronization signal associated with the smallest reliability difference.

Optionally, the primary positioning cells are not in line of sight with each other, and close synchronization between them is achieved by following a path from the line of sight link of the primary positioning cell, the path passing through one or more secondary positioning cells and reaching the secondary primary positioning cell. Each positioning cell listens to a signal from a preamble, synchronizes with the preamble, and then transmits its own positioning signal.

This step is performed before close synchronization with the remaining slaves. Basically, two or more domains appear as one large domain, where a tight synchronization signal is quickly forwarded to a secondary master device to in turn quickly start scheduling to its neighboring slave positioning cells. Optionally, the master slave device is located towards the intersection of two or more domains to speed up the tight synchronization phase.

Optionally, (i) the primary positioning cell comprises a primary positioning cell and a plurality of secondary primary positioning cells; (ii) the positioning cells are subdivided into 3 groups: a primary master positioning cell group, a secondary master positioning cell group and a slave positioning cell group; (iii) the primary positioning cell is configured to transmit a primary close synchronization signal upon receiving a synchronization signal from the cellular network, and the secondary primary positioning cell is configured to listen to the primary positioning cell, synchronize to the close synchronization signal, and then transmit a corresponding secondary close synchronization signal a predetermined time after the primary close synchronization signal; (iv) each slave positioning cell is configured to: receiving a plurality of primary close synchronization signals, calculating theoretical times of arrival of the primary close synchronization signals by using respective known distances of the secondary positioning cells from the primary positioning cell; calculating a plurality of differences, each difference being a difference between a theoretical arrival time associated with a respective primary positioning cell and an arrival time of a respective primary close synchronization signal; selecting a minimum reliability difference; and transmitting the slave positioning signal a predetermined time after the arrival time of the master close synchronization signal associated with the smallest reliable difference.

Optionally, cloud service 210 includes multiple processing elements distributed across multiple sites.

Optionally, the cloud service 210 is configured for using a processing unit associated with locating a cell and/or a configuration server.

Another aspect of some embodiments of the invention relates to a positioning system configured for use with a position resolver and a communication device 202 synchronized with a cellular network, the positioning system comprising a plurality of positioning cells. Each positioning cell comprises: a transceiver configured to transmit and receive radio frequency signals and associated with a non-volatile memory unit configured to store data; a processing unit configured for processing data and for controlling the operation of the transceiver; and a power supply configured to power the transceiver. At least one of the positioning cells is connected to the cellular network, and the positioning cells are configured to transmit, in response to receipt of synchronization signals transmitted by the cellular network, respective positioning signals receivable by the communication device 202 in frequencies used by the cellular network, each positioning signal including data indicative of an identifier of the positioning cell transmitting the positioning signal; a position resolver is in communication with the communication device 202, the position resolver configured to: receiving first data from the communication device 202 indicative of an arrival time of the positioning signal to the communication device 202, each data segment indicative of the arrival time being appended to an identifier of the associated positioning cell; processing the time of arrival and determining the location of the communication device 202 relative to the positioning cell using the known location of the positioning cell; and send second data indicative of the location to the communication device 202[ or to the cloud ]. The positioning cell comprises a master positioning cell and a plurality of slave positioning cells, the master positioning cell being synchronized with the cellular network and configured to transmit a close synchronization signal in each cycle in response to receipt of a synchronization signal in each cycle; from the positioning cell configuration for: turning on for a predetermined length of time each cycle to listen for a tight synchronization signal; receiving a tight synchronization signal; and transmitting a second positioning signal a predetermined time period after receiving the close synchronization signal such that the second positioning signal is received by the communication device 202 shortly after the communication device 202 receives the first positioning pilot while the communication device 202 is still listening.

Optionally, each slave positioning cell is configured to transmit during a respective time slot such that the slave positioning cells are configured to sequentially transmit one after the other in rapid succession.

Optionally, each slave positioning cell is configured to: listening for at least one previous primary or secondary positioning cell; determining a time difference between the arrival time of the secondary positioning signal transmitted by the previous primary or secondary positioning cell and a theoretical arrival time that would occur if the primary or secondary positioning signal transmitted by the previous primary or secondary positioning cell took the shortest path from the previous primary or secondary positioning cell to a given secondary positioning cell; and transmitting the corresponding slave positioning signal a time interval after receiving the positioning signal of the previous master positioning cell or the slave positioning cell, said time interval being equal to the predetermined delay minus the time difference.

Fig. 1 shows the structure of the positioning cell of the present invention. The positioning cell 100 of the present invention includes: a transceiver 102 configured to receive and transmit Radio Frequency (RF) signals, and associated with a power supply 104; a storage unit 106 configured to store data; and a processing unit 108 configured to receive, process and output data, and to control the operation of the transceiver in accordance with the stored, input or output data. The transceiver 102 is configured, inter alia, to transmit a positioning signal comprising data indicating the identity of the positioning cell that has transmitted the signal.

In the embodiment of fig. 1, positioning cell 100 is a self-contained device comprising transceiver 102, respective storage unit 106 and respective processing unit 108. The positioning cell 100 may be connected to an external power supply 104, as shown, or it may include its own internal power supply. The positioning cell may be implemented in the form or part of a cellular base station (e.g., a macrocell, microcell, picocell, or femtocell), a gateway device (e.g., a home DOCSIS modem/router), or other wireless device (e.g., a WiFi access point). It may also be implemented as a dedicated positioning cell.

Fig. 2 summarizes the steps of a method implemented by a positioning cell for supporting positioning determination of a communication device in a wireless communication network. At step 230, the positioning cell receives a plurality of close synchronization signals from the primary positioning cell. At step 232, the positioning cell determines a plurality of time differences between the arrival times of the plurality of close synchronization signals and the theoretical arrival times of the plurality of close synchronization signals. The theoretical time of arrival is corrected by a theoretical time of flight from the primary positioning cell to the positioning cell along the direct line-of-sight path. In step 234, the positioning cell synchronizes its clock based on one or more of the received close synchronization signals adjusted by one or more of the plurality of time differences. At step 236, the positioning cell transmits a positioning signal to a communication device in the wireless network at a time determined by its closely synchronized clock; wherein the positioning signal comprises data or timing indicating an identifier of the positioning cell; wherein the positioning signals are transmitted in a manner that does not interfere with positioning pilot signals transmitted by the wireless network.

Referring now to fig. 3, fig. 3 is a block diagram illustrating a positioning system according to some embodiments of the invention.

The system 200 comprises a plurality (two or more) of positioning cells 100a, 100b, 100c, at least one of which is in direct or indirect communication with a macro cell 220 of a cellular network and with a cloud 210. The system 200 is configured for use with a location solver 204 and a communication device 202 that communicates with a cellular network. The communication device 202 may be a cellular phone, a tablet, a laptop computer and is configured to receive a positioning signal 330 from the positioning cell 100a, 100b, 100 c. The communication device 202 records the arrival times of the different positioning signals and sends the arrival times and the identifiers of the positioning cells attached to each arrival time to the position resolver 204. The position solver 204 may optionally reside within the communication device; if it resides outside the communication device (e.g., in the cloud), communication between the communication device and the position resolver occurs over, for example, WiFi, Bluetooth, or cellular signals. The location resolver 204 has access to data indicative of the location of the positioning cell, which may have been entered into the location resolver at system 200 set-up, periodically updated by the configuration server 208 and cloud 210, or may be included in the positioning signal. By processing the time of arrival and using the known location of the locating cell, the location solver 204 calculates the location of the communication device 202 relative to the locating cell. The location resolver sends data indicative of the calculated location to the communication device 202 or to the cloud 210.

In order for their positioning signals to be detected by the communication device 202, the positioning cells are configured to transmit positioning signals when the receiver of the communication device is actively receiving signals from the cellular network. Furthermore, to determine the location of the communication device 202 with high accuracy (e.g., 1-3 meters), the positioning cells 100a, 100b, 100c are closely synchronized with each other.

First, and optionally, the system 200 will be coarsely or closely synchronized with the cellular network. Second, tight synchronization between the positioning cells is established. Third, RF calibration of the transmitter and receiver is performed.

For best accuracy, tight synchronization is preferably achieved by tight synchronization signals 332 sent by the positioning cells and received by the other positioning cells, under line-of-sight conditions. The closely synchronized signals may themselves be positioning signals, or they may be different signals, e.g., shorter data packets having lower power. When transmitting a tight synchronization signal, if transmitting in the same frequency band, (unless expensive hardware is implemented) the positioning cell cannot listen to other tight synchronization signals; thus, the positioning cells take turns sending and listening to other tight synchronization signals. When a positioning cell receives a tight synchronization signal from another positioning cell, it determines the time of arrival of the signal and subtracts the expected time of flight of the signal.

Synchronizing with cellular networks

Initially, as shown in steps 500, 502 and 504 of fig. 5, the primary master positioning cell and possibly more master positioning cells and slave positioning cells are turned on and assumed to be connected to an AC power source or powered by a battery. For battery-powered positioning cells, some procedures are minimized as explained below in order to extend battery life. To initially program and accept network assistance information, the positioning cell may communicate with a nearby user configuration device 206 (e.g., a telephone or primary positioning cell) with appropriate credentials for network assistance data, such as via a bluetooth or WiFi connection, or via a direct cellular connection between the primary positioning cell and the network (particularly the configuration server 208). The assistance data provides operator information, the frequency band and bandwidth to listen to, the Physical Cell Id (PCI) of the neighboring macro cell, the PCI of the neighboring positioning cell (if known), the frame type, the cyclic prefix type, the number of antenna ports, etc. The aim of the assistance data is to greatly simplify the hardware in the positioning cell and enable low cost software defined radio; and an optional battery-operated slave positioning cell enabled, which may last for several months before the battery has to be recharged; the positioning cell may alternatively be solar powered and include a battery.

Via assistance data, a positioning cell tunes to listen to a cellular network (e.g., L TE (4G)) (function 502). positioning cell enters a monitoring mode and listens to all bands and cellular system operators provided by the assistance data in case L TE (4G), the positioning cell listens for synchronization signals and collects signals (PSS/SSS) to find the frame synchronization and Physical Cell Id (PCI) of the strongest macrocell of the cellular network.

The best operator, i.e. the operator with the nearest macro cell, can be determined by measuring the energy in each frequency band. Optionally, a Received Signal Strength Identifier (RSSI) in each band is measured. In some embodiments of the invention, RSSI may be measured in the RF block without enabling the baseband (BB) block of the transceiver. The strongest RSSI typically signals the best operator.

The positioning cell determines its frequency error accurately and efficiently by listening to the strongest macro cell on the network from any or all operators via its cell-specific reference signal (CRS) pilot or other signal. Since the positioning cell is fixed and is not expected to have any Doppler effect (from motion), listening to the strongest cell from any or all operators can provide accurate frequency error estimates at low processing cost, the signal generally being of good quality. The positioning cell may further average the frequency error estimates from several macro cells or use a weighted average where the weight for each macro cell is a function of the SNR received from each macro cell. Alternatively, to save power, the positioning cell may choose to estimate the frequency error using only the signal of the strongest macro cell (from all network operators). This process can be used during initialization and tracking of frequency errors.

The positioning cell determines timing synchronization (520) based on the strongest cell PSS (any network operator), which automatically provides timing for the remaining networks if they are synchronized (and given a fixed time offset between operator and frequency band, which is provided via assistance information). To decode PSS of strong cells, correlation may be limited to one or a few bits (i.e. only adder) to avoid using multipliers. Thus, one or several bits of the quantized PSS reference sequence may be used in the receiver and correlated with the one or several bits of the quantized received signal from the macro cell or the strongest macro cell. This reduces power consumption. The timing of other macro cells belonging to the same frequency band, different frequency bands, or different network operators may be derived from the timing of the macro cell. The timing is derived by adding a timing offset that the configuration server provides to locate the cell. In order to provide timing offset information, the configuration server must first obtain the timing offset information, e.g. from measurements performed by other positioning cells, by the communication device, by the small cell, or directly from a database of the network operator, etc. For example, if the location of the positioning cell or communication device is known and its distance to two macro cells is known, the positioning cell or communication device listens to at least two macro cells from two different network operators, it may be determined that the time offset between their PSS signals is up to a 5ms repetition period. It reports the measurements to the configuration server together with the macro cell identity, the frequency bands to which each belongs and the network operator. The configuration server subtracts the approximate time of flight from each macro cell to the positioning cell from the measurements (note that no precise time offset is required since this process is part of the coarse synchronization process). Thus, the configuration server obtains one measurement of the timing offset between the PSS signals of two different network operators (or two different frequency bands). To reduce measurement noise, the timing offset is further averaged over many measurements from multiple positioning cells or communication devices. Furthermore, if the location of the macro cell is unknown to the configuration device, averaging may reduce errors due to unknown distances between the positioning cell or communication device and the macro cell. The configuration server may thus create an internal database of PSS timing offsets between each frequency band and between each network operator. The database will be local to each area (e.g., a city, or a portion of a city, or a segment of a road). The configuration server may then provide this information to another positioning cell in order to infer timing offsets of some frequency bands relative to another frequency band that the positioning cell has listened to. Thus, the positioning cell may listen to the strongest available macro cell and determine the timing of all other macro cells.

More accurate timing may be obtained from the CRS pilots of strong cells and may supplement the information obtained from the PSS signal. Likewise, the CRS reference signal of the strong cell may be quantized to several bits, and the CRS signal received from the macro cell may also be quantized to several bits (before and/or after Fast Fourier Transform (FFT)).

Optionally, for the few strongest cells (any operator), the positioning cell (via CRS pilots) measures and provides a differential time of arrival measurement. This information may be sent to configuration device 206 and then sent to cloud service 210 for further processing. The cloud service 210 connects to the configuration server and locates the cell through the configuration device. The cloud service 210 serves as a central control unit for the network and is configured to process data and requests, manage databases, and coordinate the operation of the positioning units. Cloud services 210 may include one or more processing units and/or storage units, which may be centrally located or may be distributed across multiple locations. The cloud service 210 may communicate with a processing unit and a storage unit associated with the positioning cell and/or with the configuration server in order to perform some of its operations. The connection with cloud services 210 may be wired or wireless and may be implemented via any type of network, such as the internet and/or a cellular network. By knowing the (approximate) location of the positioning cell, the cloud service 210 can determine an approximate distance between the positioning cell and the measured macro cell of the cellular network. This information may be used to advance the transmission of the locating cell so that it better aligns the macro cell's symbols on the transmitter side, although this is sometimes undesirable and the timing of the locating cell may be set relative to the time of arrival at the receiver side of the closest and strongest cell (per frequency band), possibly with some timing delay to account for other receptions from other more distant macro cells. Alternatively, the configuration device 206 may inform the positioning cell 100 of the desired timing advance for a given cell of the cellular network, since the configuration device 206 (assuming it is connected to the strongest cell) has access to this information through its cellular network connection, or through a known approximate distance to the cell site. This information may be used for timing advance or timing alignment in the positioning cell 100, as required by some predefined protocols, so that the positioning signal sent by the positioning cell is time aligned with the positioning signal from the macro cell. This procedure is not required if the communication device does not use the positioning signals of the macro cell for its positioning operation, except for the positioning signals of the positioning cell.

When used with a 4G/L TE cellular network, the positioning cell 100 obtains a 5ms half frame boundary from the PSS signal the positioning cell 100 may decode one SSS of a strong cell to obtain a 10ms boundary and its identity and scrambling code are provided by the configuration device 206 or the positioning cell 100 may infer a 10ms boundary by trying two hypotheses of CRS pilots (e.g., trying zero pilots in those subframes every 5 ms) and its identity and scrambling code are provided by the configuration device 206.

Next, the positioning cell 100 is configured for determining a System Frame Number (SFN), which is typically found by decoding the physical broadcast channel PBCH. But this is a relatively expensive operation. Thus, two variations for replacing PBCH decoding are provided.

In a first variation, the positioning cell 100 decodes only the strongest cell PBCH without requiring Viterbi (Viterbi) decoding or low-cost decoding using convolutional codes (e.g., Fano (Fano) decoder). There is enough repetition and interleaving, the number of antennas is known, some bits can be known using low cost channel estimation, and the PBCH can be decoded at relatively low cost if the average SNR is accumulated to 10dB, which is typical for strong cells.

In a second variation, the configuring device 206 provides the SFN number it knows without decoding the PBCH. To achieve this, the configuration device 206 needs to connect to the positioning cell 100 with 10ms time resolution. A bluetooth-like protocol between locating cell 100 and configuring device 206 should provide such an option at the hardware or firmware level with a timestamp so that when a packet is decoded by the upper layers, the time at which it was sent can be determined. This time is used by the positioning cell 100 to determine what the SFN at that point is.

Similar to the PRS signals, the positioning cell and the communication device may report to the configuration server the timing offset between SFN numbers of macro cells of different frequency bands or different network operators. The configuration server can create and maintain a database of timing offsets between SFN numbers. It may then inform another positioning cell of the timing offset between the SFN numbers of the various macro cells. The SFN number is mainly used to enable the positioning cell to obtain information on the superframe structure or general timing in a given frequency band, which enables it to know when to transmit positioning signals that are roughly or closely synchronized with the cellular network or with some wireless networks. For example, the configuration server may inform the positioning cell, in particular the primary positioning cell, that it may send a positioning signal at time T when the SFN number of the first macro cell will be equal to T1, or equivalently when the SFN number of the second macro cell will be equal to T2. SFN provides a 10ms boundary. Part of the timing within the 10ms boundary is provided by the PSS timing offset. Since the (primary) positioning cell has already decoded at least one PSS at least on the SFN and from a strong cell, it can then infer the SFN number and PSS timing of the second macro cell given the information provided by the configuration server. If it is instructed that it transmits a positioning signal in the frequency band of the second macrocell at a given coarse or fine timing, it knows how to find that timing.

The Positioning Reference Signal (PRS) configuration and the virtual PCI with its own configuration are provided to the positioning cell 100 by a configuration server. The positioning cell 100 may then begin transmitting PRS pilots (positioning signals) initially without tight synchronization but with coarse synchronization at a known time to prevent interference to the cellular network.

Note that the configuration server may be decentralized, local to the venue, and decide on its own to allocate PCI and positioning signals to positioning cells. However, it would need to coordinate with a centralized configuration server that ensures that all sites make appropriate decisions and avoids inter-site interference.

In some embodiments of the invention, if the locating cell restarts, the entire process for that cell is restarted using the connection with the configuration device 206. The configuration device 206 may, at some point, detect lost PRS pilot transmissions by the positioning cell and trigger a request to reinitiate the process. This procedure may also be used after battery replacement or recharging, or if macro cells of the cellular network restart or change configuration. However, the parameters and decisions may be stored in some memory unit within the positioning cell and reused after a restart to reduce the length of the start-up procedure.

If the PRS configuration of any operator in the cellular network changes, the PRS information in the positioning cell must be updated via a licensed or unlicensed band message and via a configuration device.

Locating the cells 100, 100a, 100b, 100c may improve emergency response by providing more accurate location. Furthermore, as will be explained below, they may remain fully orthogonal (code/time/frequency orthogonal) to other PRSs from the cell of the cellular network. Alternatively, if operators share the PRS burden, they may mute more macro cells in some PRS slots and have the positioning cells transmit only during those times when the macro is muted.

Once all positioning cells are configured and coarsely synchronized (e.g., by messages from the configuration server and configuration device, and a graph or tree of how the transmission sequence should be performed (fig. 4B, 4C, 4E)), a tight synchronization process 522 may begin, followed by a positioning signal transmission 524. The positioning cell may then receive other tight synchronization signals or positioning signals from other positioning cells and perform a calibration procedure 540, which improves the tight synchronization 522, as shown in step 530.

Design of positioning signals transmitted by positioning cells

Optionally, to prevent the PCI assigned to the positioning cell from being confused with the PCI of the macro cell belonging to the cellular network, a set of PCIs may be reserved for each positioning cell. Or a virtual PCI may be selected, which may be a recycled PCI for a given macro cell; to prevent collision or confusion between the positioning signal of the macrocell and the positioning signal of the positioning cell, the latter may transmit its positioning signal with a certain cyclic time offset if transmitted simultaneously; the cyclic time shift may be performed by using a phase ramp in the frequency domain, or by a cyclic shift of each symbol in the time domain. For example, if the macrocell is no more than 5km from the positioning cell and has a channel no more than 4km, the PCI of the macrocell can be cycled with a cyclic shift of 10 km. If the distance and channel are smaller than the non-limiting exemplary values described above, several positioning cells may use different shifts provided that the channel impulse responses do not collide. Each channel from a given positioning cell to the communication device 202 occupies a certain amount of time within an OFDM symbol. After the last audible echo is received by the channel in the communication device 202, any remaining echo is too weak to produce any significant difference in the received signal. For example, the total duration of the channel is 10 microseconds. For example, if the OFDM symbol is 70 microseconds, we can fit 7 channels, where each channel is cyclically shifted in the time domain to occupy 10 microseconds of the 70 microseconds.

Optionally, to further increase the orthogonality between the signals of the cellular network transmitted by the macro cell 220 and the signals transmitted by the positioning cells 100a, 100b, 100c, a time domain cover code may be added to each positioning cell, assuming the device is not moving too fast, such that the time domain (OFDM) symbols are multiplied by, for example, +1 or-1, in order to make them orthogonal after averaging the nearby symbols, this is a correct assumption for the present system, which is configured for positioning a communication device 202 traveling at very low speed in a small environment, by using (cyclic) time shifts and orthogonal time cover codes (for a given fixed scrambling code, i.e. a fixed recycling PCI), the space of the PCI may be increased sufficiently to allow more virtual PCIs allocable to the positioning cell.

Alternatively, the time slots reserved for indoor and venue positioning cells are completely devoid of any macro cell transmission, and therefore the positioning signals can be designed specifically for short range scenarios, independent of macro cells, so that a large number of positioning cells can coexist in around 1 ms.

The virtual PCIs may request standard changes, or they may be part of proprietary solutions and proprietary products.

Regarding the selection of the operator or operators in the cellular network, it should be noted that each positioning cell 100 requires a virtual PCI for each operator and each frequency band they use. To conserve RF resources, the positioning cell may transmit on one (or several frequency bands) at a time. In the case where a positioning cell needs to transmit positioning signals (PRS pilots) on two or more frequency bands (e.g., belonging to two or more operators) at the same time, the positioning cell may alternate between the two (or more) frequency bands, with each alternate time being transmitted on one of them. This is a PRS muting mechanism, for example, where the positioning cell should transmit once every X seconds, but it instead transmits once every 2X seconds. Every other transmission is muted. Optionally, the cloud service 210 is notified of the silent mode and it notifies the user device.

In some embodiments of the invention, adjacent multi-band and/or multi-operator positioning signals may be concatenated into one frequency band, transmitted simultaneously or nearly simultaneously (e.g., a few milliseconds apart), when feasible, which effectively results in a wider frequency band. Alternatively, locating the cells ensures the same phase/amplitude and well-known timing for each band transmission. In this embodiment, a communication device 202 with wide frequency band capability (e.g., carrier aggregation) may combine positioning signals received from multiple frequency bands/operators less than a few milliseconds apart in phase to obtain a more accurate determination of its location. This is possible if the channel of the communication device 202 does not change much between the two interband transmissions. For example, for a pedestrian, the time between two band transmissions (to be concatenated) should be less than 10 ms. If the channel of the communication device 202 has changed substantially between the other locations measured, the positioning signals received from the multiple frequency bands/operators may be combined in power rather than in phase.

In some embodiments of the invention, the positioning cell is configured to transmit on a unique frequency band from a first operator, while the communication devices 202 associated with other second operators know on which frequency band the positioning cell transmits and can tune to such frequency band for determining their own location. In this case we save bandwidth for the second operator. Alternatively, a first operator providing the service may charge a premium to users (and corresponding applications) associated with a second operator. This is particularly useful if the second operator does not have a synchronized network and can rely on the first operator to provide indoor location services. In a related embodiment, for example, the operator may choose to transmit PRS every 600ms instead of every 200 ms. Two other operators may also choose to send PRSs every 600ms, preferably interspersed or staggered at constant intervals. The communication device 202 listens to a certain operator and may then use regular intervals to listen to PRSs of different operators. Thus, for a slow moving communication device 202, the solution provides more stations with better geometry to perform position location. In other words, instead of each operator carrying the full cost of PRS transmissions (i.e., reserving bandwidth for PRS), in order to allow acceptable mobile positioning based only on its own network, the burden or cost may be shared between two or more operators. Each operator transmits fewer instances of the PRS pilot (e.g., every 2X seconds or every 3X seconds, rather than every X seconds). Then, while an operator mutes its own transmissions, another operator performs its own transmissions (again, at a rate of every 2X or 3X seconds). Transmissions from two or more operators may be staggered evenly in time (which ensures best performance for fast moving devices) or located very close in time (with long quiet periods) so that the device wakes up and listens to all operators, performs positioning operations, and returns to sleep quickly, one after the other, in one slot. Alternatively, at the expense of speed, it is advantageous for the battery life of the device (since the transmissions are not uniformly staggered in the time domain, but are transmitted adjacent to each other with long null periods)

The above-described scheme enables saving PRS slots and reserving them for positioning cells in various locations.

Positioning cells controlled by a cellular network (e.g., using a licensed spectrum) may transmit/transmit positioning signals (PRS pilots) in an unlicensed spectrum. There is a good incentive to use the unlicensed spectrum because the positioning signals transmitted by the positioning cells are completely transparent and invisible to the operator of the cellular network. Thus, interference between the cellular network and the positioning system is eliminated. However, due to unmanageable interference, unlicensed bands do not guarantee the same quality of service and accuracy in any scenario and in any environment.

The communication device 202 may listen for positioning signals using its WiFi, Bluetooth, or other modules.they may have similar (or identical) structures to those used in cellular licensed bands.the cloud service 210 informs the communication device 202 that the band is an unlicensed band with a given center frequency and bandwidth.

In some embodiments of the invention, given a short range and an indoor channel, a positioning cell may transmit a positioning signal designed for licensed or unlicensed spectrum to allow for shorter range and indoor channels. In particular, the symbols and FFT size may be much shorter to reduce power consumption or memory requirements. The symbols may still be overlaid on the PRS region of the cellular network and they may be orthogonal to the PRS signal of the cellular network, but the user equipment may be informed that these are shorter symbols.

Positioning WiFi synchronization between cells

Thus far, the description has been primarily directed to systems and methods for locating a communication device 202 via transmission of a locating signal in a cellular frequency or in a frequency for which the locating cell operates similar to a cell and is designed for this purpose.

This section relates to systems that reuse the positioning cells of deployed or to-be-deployed WiFi stations or Access Points (APs). The techniques described below require only software upgrades in the communication device and WiFi station; some options will also be described including hardware changes to the communication device 202 and/or WiFi station. With the upgrade, the WiFi AP may work like a positioning cell.

It should be noted that, in general, WiFi stations are limited by the listen-before-talk (L BT) constraint, where each station first senses its radio environment before it starts transmitting.

Each AP typically transmits WiFi beacons every 102.4ms, which may span 20 MHz. The band is not wide enough to achieve reliable positioning within 1 meter. However, in 802.11ac, the data transmission bandwidth in the AP can be as high as 80 or 160MHz, which is sufficient for 1 meter accuracy.

Today's 802.11ac accurate positioning works by measuring the round-trip delay between the communication device 202 (e.g., mobile phone) and each AP. The technique includes sending and receiving data packets (at least one data packet in each direction, with a wide frequency band) to each AP. This technique drains the battery of the communication device because the communication device 202 must exchange communications with each AP in the vicinity, send data packets for each positioning measurement, and decode the data packets. Assuming a desired accuracy of 1m, if the communication device 202 moves a few meters, the transmission of data packets to and from each AP must begin again. Furthermore, because this technique uses a large amount of bandwidth for exchanging messages, it is not scalable as the number of communication devices in a venue grows.

In order to reduce power consumption and message exchange, the inventors have adopted techniques similar to the synchronized networks described above.

Once tightly synchronized, every 102.4ms, the normal beacon from the AP will appear at some predetermined time with no drift or with minimal drift that is periodically corrected. However, since the carrier is sensed in the unlicensed band, the beacon may be slightly shifted while waiting for another transmission to end.

In an embodiment, the AP is configured to transmit a p-beacon (p-beacon) (positioning beacon or positioning signal, and which also acts as a close synchronization signal). Each AP transmits a p-beacon at a desired period (e.g., every 1s, 5s, or 10). The location where the AP is located determines the period. In some locations, the network is not heavily loaded, so p-beacon transmissions per 1s or less are possible and scalable without impacting network capacity. Optionally, all p-beacons are transmitted with a predetermined and adjacent timing within their transmission period, which enables the communication device 202 to quickly listen for all p-beacons transmitted in rapid succession and thus save battery. The normal beacons may include data indicating where all p-beacons are located relative to the normal beacons. In this way, the communication device 202 need not search for a p-beacon. Instead, the AP is synchronized to the cellular network (or to satellite navigation) and informed by the configuration server and cloud of where the communication device 202 is to locate the p-beacon without decoding any normal beacons. The positioning p-beacon may be an orthogonal waveform in time and/or frequency (orthogonal cover code over OFDM symbols, or one beacon every few OFDM symbols, and orthogonal cyclic shift beacons over OFDM symbols). The p-beacon includes pilots for measuring time of flight.

In the simplest scheme, each AP will send several OFDM symbols containing the primary pilot, followed by the next AP, and so on. Small gaps between transmissions may be used. A typical or special preamble may precede the OFDM symbol. This results in minimal or no changes to the hardware/firmware.

The p-beacon may include only a preamble instead of transmitting an OFDM symbol.

The configuration server reserves time for the p-beacons appropriate for the venue based on the client requirements. The time is synchronized with the cellular network or other network. Since the cellular network SFN period is 10.24 seconds, this time will also be synchronized with the 102.4ms normal WiFi beacon, and thus the normal beacon and the p-beacon will not drift relative to each other. For example, the repetition period may be of the order of 1s or 5s or 10 s. The cellular network may inform the communication device of the location of the p-beacon in the entire area or city. Thus, the communication device can quickly locate the p-beacon without doing any search.

Unlike normal beacons, p-beacons are broadband (e.g., 80 or 160MHz) across the domain and need not be normal data packets. The p-beacons are optionally set to very short bursts and may contain only fields (preamble, optionally dummy but known data, optionally Orthogonal Frequency Division Multiplexing (OFDM) pilots without data, etc.) sufficient to compute the channel estimate (i.e., time of arrival). The communication device 202 estimates the channel without performing any data decoding.

In principle, if the transmission of the p-beacons is synchronous, and has a known transmission timing for each p-beacon, a time difference of arrival (TDOA) multilateration can be performed to locate communication device 202. However, due to the need for carrier sensing in unlicensed spectrum, the p-beacon may have to be delayed until another transmission terminates and may thus be shifted in time. The time shift breaks the synchronicity and the transmission timing is no longer known.

To address this time-shifting problem, when an AP must delay its transmission due to another ongoing transmission, it is configured to time-shift the p-beacon relative to the missing original transmission timing by an amount that is a multiple of a fixed and known time unit (or distance unit). For example, the delay is a multiple of 200 meters (i.e., 600ns), or a multiple of 1000m (i.e., 3 us). The time unit must be longer than the longest expected time of flight between the AP and the communication device, or between the AP and another AP that may be listening. By shifting the p-beacon by a multiple of 200m (i.e., 600ns), the communication device 202 can determine that there is a shift (since it is longer than any actual channel) and that it needs to subtract a multiple of 200m from the measured arrival time, i.e., modulo 200m (otherwise the arrival time appears too late to be invalid; the subtraction of the multiple of 200m corrects for the problem). Thus, without knowing the delayed transmission of the exact transmission timing, the communication device 202 can still ascertain the time shift by using modulo 200m arithmetic. Thus, although the AP must delay its transmission, conventional TDOA multipoint positioning can be used as if the transmissions were synchronized.

Alternatively, to prevent yet another transmission from another device during the 600ns wait, the AP may reserve the medium by starting to transmit dummy bits (as distinguished from the p-beacon signal) until the p-beacon may start at the 600ns boundary. In essence, the AP passes through the dummy bit reservation medium while waiting for the ideal start time of the p-beacon. This approach enables some deployed APs to provide accurate positioning via software upgrades.

This ensures that the transmission of p-beacons is closely synchronized to the first master AP. so it is useful to create a transmission order such that each AP has the opportunity to hear the master AP or another AP. preferred order of earlier transmissions such that the next transmitting AP is in L oS relative to the previously transmitted AP and so on until all APs are covered in a tree-like manner.

The primary AP may further roughly synchronize to the cellular network, which enables the communication device 202 to quickly locate all p-beacons without any search, and without decoding any normal beacons, in order to be able to listen to the cellular network, the primary AP typically requires a hardware upgrade, instead, the communication device 202 is software upgraded to assist the primary AP and all APs to synchronize to the cellular network, when the communication device 202 enters the premises (or is some distance away from any one AP), the AP synchronizes its p-beacons to the device clock of the communications already synchronized to the cellular network, the remaining APs will notify them to apply an increment in timing to correct their timing, as needed, via, for example, a WiFi message, only the p-beacons need to be readjusted in time to realign it to the cellular network, while normal beacons may remain anywhere in time, after a few hours, the p-beacons only shift by 1ms, which is still short for the communication device 202 to search for the p-beacons, which may be further informed from the AP to the indoor AP that the communication device 202 can obtain further information about the normal beacons, if the p-beacons are needed to be moved from the AP to the wireless network, the WiFi network, or the AP can not detect further when the normal beacons, the AP-beacon, and the WiFi information is available.

Synchronization to satellite navigation system

In further embodiments, the systems, methods, and devices described herein may be applied based on the use of satellite navigation system ("satnav") technology, such as the U.S. Global Positioning System (GPS), global navigation satellite system for european galileo or russia (G L ONASS), this is particularly useful if at least the primary positioning cell is located outdoors, and if the system does not use licensed bands, but only unlicensed bands for positioning signals (e.g., WiFi signals are used as positioning signals within the venue).

In an embodiment, a primary positioning cell may be configured to receive navigation messages sent from a plurality of satellites. Those skilled in the art will appreciate that the decoding and combining of messages from multiple satellites may be used to determine the location of the primary positioning cell and establish an accurate time reference.

As described herein, the close synchronization signal may be constructed in the form of a 3GPP (e.g., L TE) PRS pilot.

In an embodiment, a system or configuration server determines a convenient universal time T and repetition period P by which a primary positioning cell may initiate transmission of positioning signals and close synchronization signals (e.g., in an unlicensed band). In this case, the primary positioning cell may obtain the universal time by listening to the satellite navigation signal, or if it cannot hear the satellite navigation signal, find the universal time T by listening to a macro cell from the cellular network and applying a predetermined time offset; this assumes that the macrocell itself is synchronized with the satellite navigation signal, and the configuration server can learn the time offset between the macrocell signal (particularly the superframe number and 10ms boundary) and the preselected universal time T, and inform the primary positioning cell of this time offset. Furthermore, to prevent drift between the satellite navigation signals, the cellular network signals, and the potential WiFi beacon signals, the repetition period P may be selected to be a multiple of 102.4ms or a multiple of 512 ms.

Asynchronous options

In an embodiment, positioning cells in a venue are closely synchronized and calibrated to each other, but are not synchronized to external systems such as cellular networks or satellite navigation signals. In this case, the timing of locating the cell will drift over time relative to the external system. When a communication device enters a venue, it will have to search for a location signal as it drifts over time.

In an embodiment, a regular beacon of a WiFi access point transmitted every 102.4ms may provide information about the timing and periodicity of positioning signals within a venue. Thus, the communication device can discover the signal by listening for a normal beacon without having to search for many seconds for a positioning signal.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Some features described in the context of various embodiments are not considered essential features of those embodiments, unless the embodiments do not work without these elements.

Furthermore, various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. It will become apparent to those of ordinary skill in the art, after reading this document, that the illustrated embodiments and their various equivalents may be implemented without limiting the illustrated examples. For example, block diagrams and accompanying descriptions should not be construed as mandating a particular architecture or configuration.