阅读说明：本技术 确定无线系统中的用户设备的位置的方法 (Method for determining the position of a user equipment in a wireless system ) 是由 费利克斯·马尔霍夫斯基 杜鲁门·普雷瓦特 于 2013-12-10 设计创作，主要内容包括：公开了一种用于确定具有一个或更多个扇区的无线系统中的用户设备UE的位置的方法,所述一个或更多个扇区中的每个扇区由一个或更多个天线形成,所述方法包括：确定来自不同扇区的两个或更多个天线的特定参考信号在UE处的到达时间；利用包括高分辨率谱估计的一个或更多个多径抑制算法来解析所述特定参考信号；确定所述到达时间的差异,以确定所述天线或扇区的基线与来自所述UE的入射能量之间的角度；以及使用所述角度来确定所述UE的位置。(Disclosed is a method for determining a location of a user equipment, UE, in a wireless system having one or more sectors, each of the one or more sectors being formed by one or more antennas, the method comprising: determining times of arrival at the UE of specific reference signals from two or more antennas of different sectors; resolving the particular reference signal using one or more multipath mitigation algorithms comprising a high resolution spectrum estimate; determining a difference in the time of arrival to determine an angle between a baseline of the antenna or sector and incident energy from the UE; and determining a location of the UE using the angle.)

1. A method for determining a location of a user equipment, UE, in a wireless system having one or more sectors, each of the one or more sectors formed by one or more antennas, the method comprising:

determining times of arrival at the UE of specific reference signals from two or more antennas of different sectors;

resolving the particular reference signal using one or more multipath mitigation algorithms comprising a high resolution spectrum estimate;

determining a difference in the time of arrival to determine an angle between a baseline of the antenna or sector and incident energy from the UE; and

determining a location of the UE using the angle.

2. The method of claim 1, wherein one of the different sectors is a serving sector and one of the different sectors is not a serving sector.

3. The method of claim 1, wherein a distance between the two or more antennas or sectors is smaller relative to a distance from the two or more antennas or sectors to the UE.

4. A method for determining a location of a user equipment, UE, in a wireless system having one or more sectors, each of the one or more sectors formed by one or more antennas, the method comprising:

determining times of arrival of a particular reference signal from the UE at two or more antennas from different sectors;

resolving the particular reference signal using one or more multipath mitigation algorithms comprising a high resolution spectrum estimate;

determining a difference in the time of arrival to determine an angle between a baseline of the antenna or sector and incident energy from the UE to the two or more antennas or sectors; and

determining a location of the UE using the angle.

5. The method of claim 4, wherein one of the different sectors is a serving sector and one of the different sectors is not a serving sector.

6. The method of claim 4, wherein a distance between the two or more antennas or sectors is smaller relative to a distance from the two or more antennas to the UE.

Technical Field

The present embodiments relate to wireless communication and wireless network systems and systems including RTLS (real time location services) for Radio Frequency (RF) based identification, tracking and location of objects.

Background

RF-based identification and location systems for determining the relative or geographic location of objects are commonly used for tracking individual objects or groups of objects as well as for tracking individuals. Conventional positioning systems have been used for position determination in open outdoor environments. An RF-based Global Positioning System (GPS) and an assisted GPS are commonly used. However, conventional positioning systems suffer from certain inaccuracies when positioning objects in closed environments (i.e., indoors) as well as outdoors. Although cellular wireless communication systems provide excellent data coverage in urban and most indoor environments, the positioning accuracy of these systems is limited by self-interference, multipath, and non-line-of-sight propagation.

Indoor and outdoor positioning inaccuracies are mainly due to the physics of RF propagation, in particular to loss/attenuation of RF signals, signal scattering and reflection. The loss/attenuation and scattering problems can be addressed by employing narrow band ranging signals and by operating at low RF frequencies, for example, in the VHF band or lower (see co-pending application No. 11/670,595).

However, at VHF and lower frequencies, multipath phenomena (e.g., RF energy reflections) are less severe than at UHF and higher frequencies, and the effects of multipath phenomena on positioning accuracy make position determination less reliable and less accurate than what is needed by the industry. Accordingly, there is a need for a method and system that: the method and system are used to suppress the effects of RF energy reflections (i.e., multipath phenomena) in RF-based identification and location systems that employ narrowband ranging signals.

In general, conventional RF-based identification and location systems suppress multipath by employing wide Bandwidth ranging signals, for example, by exploiting the broadband signal properties for multipath suppression (see S.Salous, "Inder and Outdoor UHF multimedia with a 90MHz Bandwidth", IEEE colloid on Propaulion characteristics and Related System technologies for Beyond Line-of-Sight Radio, 1997, pp. 8/1 to 8/6). See also Chen et al, patent US 2011/0124347 a1, where the positioning accuracy versus required PRS bandwidth is shown in table 1. From this table, for an accuracy of 10 meters, a bandwidth of 83MHz is required. In addition, spatial diversity and/or antenna diversity techniques are used in some cases.

However, spatial diversity may not be an option in many location tracking applications because it leads to an increase in the required architecture. Similarly, antenna diversity has limited value because at lower operating frequencies, such as VHF, the physical size of the antenna subsystem becomes too large. A related example is U.S. patent No. 6,788,199, which describes a system and method for locating objects, people, pets, and personal belongings.

The proposed system employs an antenna matrix to suppress multipath. The system optionally operates at UHF in the 902-. It is well known that the linear dimension of an antenna is proportional to the wavelength of the operating frequency. In addition, the area of the antenna matrix is proportional to the ratio of the square and volume of the linear dimension to the cube of the linear dimension, since in antenna arrays, the antennas are typically separated by 1/4 or 1/2 of wavelengths. Thus, at VHF and lower frequencies, the size of the antenna matrix will significantly affect the portability of the device.

On the other hand, due to the very limited frequency spectrum, narrow bandwidth ranging signals are not suitable for multipath mitigation techniques currently used by conventional RF-based identification and location systems. The reason for this is that: the ranging signal distortion (i.e., the variation in the signal) caused by multipath is too small for reliable detection/processing of the presence of noise. In addition, due to the limited bandwidth, when these ranging signal direct line-of-sight (DLOS) paths are separated from the delayed ranging signal paths by small delays, the narrow bandwidth receiver cannot distinguish between the ranging signal direct line-of-sight (DLOS) paths and the delayed ranging signal paths because the narrow bandwidth receiver lacks the required time resolution that is proportional to the bandwidth of the receiver (e.g., the narrow bandwidth has an integral effect on the input signal).

Accordingly, there is a need in the art for a multipath mitigation method and system for object identification and location that uses narrow bandwidth ranging signals and operates at VHF frequencies or lower and UHF band frequencies or higher.

Tracking and location functionality needs primarily exist in wireless networks. The multipath mitigation method and system for object identification and location described in the co-pending application No.12/502,809 may be utilized in most available wireless networks. However, some wireless networks have communication standards/systems that require the incorporation of technology into the wireless network to fully benefit from the various ranging and positioning signals described in the co-pending application No.12/502,809. In general, these wireless systems can provide excellent data coverage over a wide area and in most indoor environments. However, the available positioning accuracy of these systems is limited by self-interference, multipath, and non-line-of-sight propagation. As an example, the standardized positioning technology for LTE (long term evolution) standard of the recent 3GPP release 9 has the following method: 1) a-GNSS (assisted global navigation satellite system) or a-GPS (assisted global positioning system) as a main method; and 2) enhanced Cell-ID (E-CID) and OTDOA (observed time difference of arrival) including DL-OTDOA (downlink OTDOA) as a backup method. While these methods can meet current mandatory FCC E911 emergency positioning needs, the accuracy, reliability, and availability of these positioning methods fall short of those of LBS (location based services) or RTLS system users who require highly accurate positioning within buildings, malls, downtown corridors, and the like. Furthermore, the upcoming FCC 911 requirements are more stringent than the existing FCC 911, except that a-GNSS (a-GPS) may exceed the positioning capabilities of existing technologies/methods. It is well known that the accuracy of a-GNSS (a-GPS) is very good in open space but very unreliable in urban/indoor environments.

At the same time, the accuracy of other techniques/methods is severely affected by multipath and other radio wave propagation phenomena. Thus, it is not possible to meet the upcoming FCC 911 requirements and LBS requirements. Positioning techniques/methods other than DL-OTDOA and E-CID positioning techniques/methods are listed below. The U-TDOA concept is similar to OTDOA, but uses a Location Measurement Unit (LMU) installed at a cell tower (cell tower) to calculate the location of the phone. The above is designed for the original 911 requirements (already designed). LMUs are deployed only on 2G GSM networks and require major hardware upgrades for 3G UMTS networks. U-TDOA has not been standardized for support of 4G LTE or WiMAX. In addition, LMUs are not used in LTE deployments. Like other methods, the accuracy of U-TDOA suffers from multipath. The LTE standardization group may forgo the additional hardware of the LUM and reform U-TDOAs, e.g., UL-OTDOA, in accordance with DL-OTDOA. Note that: DL-OTDOA is standardized in release 9.

Another competitor to the upcoming FCC 911 demand is RF fingerprinting. This technique is based on the principle that each location has a unique Radio Frequency (RF) signature, such as a fingerprint pattern, that can identify the location by a unique set of values including measurements of signal strength of neighboring cells, etc. However, this technique suffers from the fact that it requires a large database and a long training period. In addition, unlike a true unique human fingerprint, RF signatures repeat at multiple different locations due to RF propagation phenomena. Furthermore, as the environment, including weather, changes, the database becomes stale, e.g., the signature quickly becomes stale. This makes the task of maintaining the database burdensome. The number of cell towers that can be listened to has a significant impact on accuracy-readings from multiple (8 or more) towers need to be obtained for reasonable accuracy (60 meters as claimed by Polaris wireless). Thus, in a suburban environment, accuracy drops to 100 meters (see Polaris wireless location technology overview, 7 months 29 days from Polaris wireless). In addition, there is a significant change (up to 140%) in the estimated position using handset antenna orientation (see MicrocopicExamination of an RSSI-Signature-Based antenna Localization System by Tsung-Han Lin et al).

Although there are several reasons why the RF fingerprinting database is unstable, one of the main reasons is multipath. Multipath is highly dynamic and can change the RF signature instantaneously. In particular, in severe multipath environments such as indoors, people and elevators move; furniture, cabinets, equipment placement variations will produce different multipath profiles, for example, severely affecting the RF signature. In addition, small changes in physical location (3-dimensional) cause significant changes in RF signatures, indoors and similar environments. This is a result of the combination of multipath, which makes the RF signature 3-dimensional, and short wavelengths, which produce significant RF signature variations over 1/4 wavelength distances. Thus, in such an environment, the number of points in the database must increase exponentially.

There are less accurate positioning methods, such as RTT, RTT + CID, including methods based on received signal strength. In the latter case, however, the RF propagation phenomenon causes the signal strength to vary by 30dB to 40dB over distances of wavelengths that can be significantly less than meters in wireless networks. This seriously affects the accuracy and/or reliability of the method based on the received signal strength. Furthermore, the accuracy of all these methods suffers from multipath.

Accordingly, there is a need in the art for more accurate and reliable tracking and positioning capabilities for wireless networks, which may be achieved through multipath mitigation techniques.

Positioning Reference Signals (PRS) are added in release 9 of LTE 3GPP and are intended to be used by User Equipment (UE) for OTDOA positioning (multipoint positioning type). TS36.211 version 9 technical Specification entitled "Evolved Universal Radio Access (E-UTRA); physical Channels and modulation.

As noted, PRS may be used by UEs for downlink observed time difference of arrival (DL-OTDOA) positioning. The release 9 specification also requires that neighboring base stations (enbs) be synchronized. This removes the last obstacle of the OTDOA method. PRS also improves UE hearability at UEs of multiple enbs. Note that release 9 specifications do not specify eNB synchronization accuracy, with 100ns being suggested in some proposals. UL-TDOA is currently in the research phase and is expected to be standardized in 2011.

The DL-OTDOA Method according to the Release 9 specification is detailed in U.S. patent application publication No. 2011/0124347A 1 to Chen et al entitled "Method and Apparatus for UE Positioning in LTENetworks. Release 9DL-OTDOA suffers from multipath phenomena. Some multipath mitigation may be achieved by the increased PRS signal bandwidth. However, this therefore results in increased scheduling complexity and longer time between UE position determination. In addition, for networks with limited operating bandwidth, such as 10MHz, the best possible accuracy is about 100 meters, as shown in Table 1 of Chen et al. These numbers are the result in an optimal situation scenario. In other cases, particularly when the DLOS signal strength is significantly lower (10-20 dB) compared to the reflected signal strength, a significantly larger (two to four times) positioning/ranging error results.

Chen et al describes a variation of UL-TDOA location, also based on PRS, known as uplink positioning reference signals (UL-PRS). Chen et al proposes improved neighbor cell hearability and/or reduced scheduling complexity, however Chen et al does not teach any method to address the mitigation of multipath. Thus, the accuracy of Chen et al is not better than that of version 9 according to the accuracy of the DL-OTDOA method.

According to Chen et al, the DL-OTDOA method and the UL-TDOA method are suitable for outdoor environments. Chen et al also noted that DL-OTDOA methods and UL-TDOA methods do not perform well in indoor environments such as buildings, campuses, etc. Several reasons have been pointed out by Chen et al to illustrate the poor performance of these methods in indoor environments. For example, in a Distributed Antenna System (DAS) that is typically employed indoors, each antenna does not have a unique ID.

According to Chen, the end result is: in both release 9 systems and cell tower based systems (e.g., Chen et al UL-TDOA), the UE device cannot distinguish between multiple antennas. This phenomenon prevents the use of the multipoint positioning method employed in the UL-OTDOA system of release 9 and Chen. To address this problem, Chen et al adds hardware and new network signals to an existing indoor wireless network system. Furthermore, in case of active DAS, the optimal accuracy (lower error limit) is limited to 50 meters. Finally, Chen et al does not address the effect of multipath on positioning accuracy in an indoor environment, where multipath is the most severe (compared to outdoors) and in many cases produces a positioning error much larger (2X-4X) than the claimed positioning error.

The modifications to the indoor wireless network antenna system taught by Chen et al are not always possible because of the enormous effort and high cost required to upgrade an existing system. Furthermore, in the case of an active DAS, the optimal theoretical accuracy is only 50 meters, and in practice this accuracy is significantly lower due to RF propagation phenomena including multipath. Meanwhile, in a DAS system, signals generated by multiple antennas will exhibit reflections, such as multipath. Thus, if all antenna positions are known, location determination in a DAS environment can be provided without additional hardware and/or new network signals, for example using a multilateration and location consistency algorithm, if signal paths from individual antennas can be resolved. Accordingly, there is a need in the art for accurate and reliable multipath resolution for wireless networks.

Disclosure of Invention

The present embodiments are directed to a method and system for Radio Frequency (RF) based identification, tracking and location of objects including a Real Time Location Service (RTLS) that substantially obviates one or more of the disadvantages of the related art. The proposed (exemplary) method and system uses narrow bandwidth ranging positioning signals. According to an embodiment, RF-based tracking and localization is implemented on the VHF band, but can also be implemented on lower bands (HF, LF, and VLF) as well as on UHF and higher frequencies. RF-based tracking and positioning employs multipath mitigation methods that include techniques and algorithms. The proposed system may use software implemented digital signal processing and software defined radio technology. Digital signal processing may also be used.

Standard FPGAs and standard signal processing hardware and software can be used to construct the system of an embodiment for very small incremental cost of the device and the overall system. At the same time, the accuracy of RF-based identification and location systems employing narrowband ranging signals can be significantly improved.

Transmitters and receivers for narrow bandwidth ranging/positioning signals, such as VHF, are used to identify the location of a person or object. Digital Signal Processing (DSP) and Software Defined Radio (SDR) techniques may be used to generate, receive, and process narrow bandwidth ranging signals and perform multipath mitigation algorithms. Narrowband ranging signals are used to identify, locate and track people and objects in a half-duplex mode of operation, a full-duplex mode of operation or a simplex mode of operation. Digital Signal Processing (DSP) and Software Defined Radio (SDR) techniques are used in multipath mitigation processors to implement multipath mitigation algorithms.

The method described herein employs the multipath mitigation processor and multipath mitigation techniques/algorithms described in co-pending application No.12/502,809, which improves the accuracy of the tracking and positioning system implemented by the wireless network. The present embodiments may be used in all wireless systems/networks and include a simplex mode of operation, a half-duplex mode of operation, and a full-duplex mode of operation. The embodiments described below operate with wireless networks employing various modulation types including OFDM modulation and/or variations thereof. Thus, the embodiments described below operate with LTE networks and are also applicable to other wireless systems/networks.

The approaches described herein are based on one or more reference/pilot signals and/or synchronization signals of the network, and may also be applicable to other wireless networks including WiMax, WiFi, and White Space. Other wireless networks that do not use reference signals and/or pilot/synchronization signals may employ one or more of the following types of alternative embodiments as described in the co-pending application No.12/502,809: 1) dedicating a portion of the frame to a ranging signal/ranging signal element as described in co-pending application No.12/502,809; 2) embedding ranging signal elements (see co-pending application No.12/502,809) in the transmit/receive frame; and 3) a ranging signal element (described in co-pending application No.12/502,809) with data embedded therein.

These alternative embodiments employ the multipath mitigation processor and multipath mitigation techniques/algorithms described in the co-pending application No.12/502,809 and may be used in all modes of operation: simplex, half duplex, and full duplex.

The following integration can be done with little or no incremental cost relative to the device and the overall system: the integration of multipath mitigation processors and multipath mitigation techniques/algorithms described in the co-pending application No.12/502,809 with OFDM-based wireless networks and the integration of other wireless networks with reference signals/pilot signals and/or synchronization signals. At the same time, the positioning accuracy of the network and the system can be obviously improved. As described in the embodiments, implementing RF-based tracking and positioning on a 3GPP LTE cellular network would clearly benefit from the localization of the multipath mitigation methods/techniques described in the co-pending application No.12/502,809. The proposed system may use digital signal processing implemented in software or hardware.

Additional features and advantages of the embodiments will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments. The advantages of the embodiments will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of embodiments, as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification, illustrate embodiments and together with the description serve to explain the principles of the embodiments. In the drawings:

fig. 1 and 1A illustrate narrow bandwidth ranging signal frequency components in accordance with an embodiment;

figure 2 illustrates exemplary wide bandwidth ranging signal frequency components;

3A, 3B, and 3C illustrate block diagrams of master and slave units of an RF mobile tracking and location system according to an embodiment;

FIG. 4 illustrates a synthesized wideband baseband ranging signal of an embodiment;

FIG. 5 illustrates elimination of signal precursors by cancellation according to an embodiment;

fig. 6 illustrates precursor cancellation with fewer carriers according to an embodiment;

FIG. 7 illustrates an embodiment of a one-way transfer function phase;

FIG. 8 illustrates an embodiment of a positioning method;

fig. 9 shows LTE reference signal mapping;

fig. 10 illustrates an embodiment of an enhanced Cell ID + RTT positioning technique;

FIG. 11 illustrates an embodiment of an OTDOA positioning technique;

fig. 12 illustrates the operation of a time observation unit (TMO) installed at an operator's eNB facility, in accordance with an embodiment;

FIG. 13 illustrates an embodiment of a wireless network location device diagram;

fig. 14 illustrates an embodiment of locating a downlink ecosystem for a wireless network for enterprise applications;

FIG. 15 illustrates an embodiment of locating a downlink ecosystem for a wireless network in wide application of the network;

fig. 16 illustrates an embodiment of locating an uplink ecosystem for a wireless network for enterprise applications;

FIG. 17 illustrates an embodiment of locating an uplink ecosystem for a wireless network in wide application of the network;

figure 18 illustrates an embodiment of a UL-TDOA environment that may include one or more DAS and/or femto cell/small cell antennas;

figure 19 shows an embodiment of UL-TDOA as in figure 18 that may include one or more cell towers that may be used in place of DAS base stations and/or femto cells/small cells;

fig. 20 shows an embodiment of cell-level positioning;

figure 21 illustrates an embodiment of serving cell and sector ID positioning;

FIG. 22 shows an embodiment of E-CID plus AoA positioning;

fig. 23 shows an embodiment of AoA positioning;

FIG. 24 shows an embodiment of TDOA with wide inter-receive antenna distance and close inter-receive antenna distance;

FIG. 25 illustrates an embodiment of a three sector deployment; and

fig. 26 illustrates an embodiment of antenna port mapping.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

The present embodiments relate to methods and systems for RF-based identification, tracking and localization of objects, including RTLS. According to embodiments, methods and systems employ narrow bandwidth ranging signals. The embodiments operate in the VHF band, but may also be used in the HF, LF, and VLF bands as well as the UHF band and higher frequencies. Embodiments employ a multipath mitigation processor. The use of a multipath mitigation processor improves the accuracy of tracking and positioning achieved by the system.