Method and system for wireless device positioning

Abstract

The present disclosure describes methods and systems for estimating the position of a mobile terminal. The position of a mobile terminal can be estimated based on measurement timing information of reference signals transmitted by a plurality of base stations and received by the mobile terminal, compensated for non-line-of-sight (NLOS) delay times from the reference signal propagation times. The NLOS delay times can be estimated using one or more positioning anchors. Alternatively, the NLOS delay times can be estimated using multiple spatially separated antennas of the mobile terminal, by jointing with other mobile terminals, or by using other approximation methods. The methods provided by the present disclosure facilitate more accurate position estimates for high-precision mobile positioning applications.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods and systems for geopositioning of wireless devices in wireless communication networks. BACKGROUND

[0002] Wireless communication technology is driving the world towards rapidly growing network connectivity. In many applications, such as Industrial Internet of Things (IIoT) and V2X applications (including vehicle-to-infrastructure, vehicle-to-network, vehicle-to-pedestrian applications, etc.), it can be desirable to accurately determine the geographical position of various wireless devices and network nodes. For example, a position estimate can be derived from a distance estimate based on a measurement of the propagation time of a wireless reference signal from a network node or device with a known geographical position. Distance estimates between wireless devices based on reference signal propagation time can become inaccurate when the reference signal is transmitted through multiple reflections rather than a direct path. SUMMARY

[0003] The present disclosure describes methods and systems for estimating the reference signal transmission delay time between wireless network nodes or devices due to multiple reflections and / or refractions. The estimated transmission delay is used to more accurately estimate the geographical position of a wireless device based on, for example, hyperbolic or triangular positioning techniques, using measured time of arrival (TOA) information and / or other timing information of the reference signal.

[0004] In some embodiments, a method performed by an anchor device is disclosed. The method can comprise receiving reference signals transmitted from a plurality of wireless network nodes; obtaining geographical positions of the plurality of wireless network nodes; determining time delays in signal propagation times of the reference signals that exceed respective line-of-sight (LOS) transmission times; and transmitting the time delays to a positioning server or a mobile terminal to enable the positioning server or the mobile terminal to perform geopositioning of the mobile terminal.

[0005] In some other embodiments, a method performed by a positioning service node in a wireless communication network is disclosed. The method can comprise obtaining a set of timing measurement information associated with reference signals transmitted by a plurality of wireless network nodes and received by a mobile terminal; obtaining geographical positions of the plurality of wireless network nodes; estimating time delays in signal propagation times of the reference signals that exceed respective LOS transmission times; compensating the set of timing measurement information with the estimated time delays to obtain compensated timing measurement information; and determining a geographical position of the mobile terminal based on the compensated timing measurement information and the geographical positions of the plurality of wireless network nodes.

[0006] In some other embodiments, a method performed by a mobile terminal is disclosed. The method can include receiving reference signals from a plurality of wireless network nodes; measuring reference signal propagation times of the received reference signals; obtaining estimated time delays of the reference signal propagation times that exceed corresponding LOS transmission times; and transmitting the estimated time delays and the reference signal propagation times to a positioning service node, or transmitting compensated reference signal propagation times to the positioning service node based on the reference signal propagation times compensated by the estimated time delays, to cause the positioning service node to estimate a geographic position of the mobile terminal.

[0007] Various apparatuses or systems are also disclosed. Each of these apparatuses or systems includes a processor, where the processor is configured to implement any of the above-described methods.

[0008] Computer-readable media are also disclosed. Such computer-readable media include instructions that, when executed by a computer, cause the computer to perform any of the above-described methods.

[0009] Other aspects and alternatives of the above-described embodiments and implementations thereof are described in more detail in the following drawings, descriptions, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 Reference signal transmissions via non-line-of-sight (NLOS) rather than line-of-sight (LOS) paths are shown, along with transmission time delays therebetween.

[0011] Figure 2 A portion of an example wireless communication network configured for estimating NLOS time delays to improve geographic positioning of wireless devices is shown.

[0012] Figure 3 An example embodiment for estimating NLOS time delays for wireless positioning anchors is shown.

[0013] Figure 4 An example embodiment for using wireless positioning anchors to estimate NLOS time delays to improve geographic positioning of wireless devices is shown.

[0014] Figure 5 Another example embodiment for using multiple antennas of a wireless device to estimate NLOS time delays to improve geographic positioning of the wireless device is shown.

[0015] Figure 6 Yet another example embodiment for using multiple neighboring wireless devices to estimate NLOS time delays to improve geographic positioning of a wireless device is shown. DETAILED DESCRIPTION

[0016] The techniques and examples of the implementations and / or embodiments in this disclosure can be used to improve the geolocation performance of wireless devices in wireless communication networks. The term “exemplary” is used to mean “an example of” and, unless otherwise noted, is not intended to mean ideal or preferred examples, implementations or embodiments. The various implementations can be embodied in various forms, and thus, the disclosure or claimed subject matter is intended to be construed as not being limited to any one embodiment set forth below. The various implementations can take different forms, and thus, the scope of the disclosure or claimed subject matter is intended to be construed as not being limited to any one embodiment set forth below. The various implementations can take different forms, and thus, the scope of the disclosure or claimed subject matter is intended to be construed as not being limited to any one embodiment set forth below. The various implementations can be embodied as a method, device, component, or system. Thus, embodiments of the disclosure can take the form of an apparatus, a software program, a firmware program, or any combination thereof.

[0017] As an introduction, many applications in new generation wireless communication networks require high-precision geolocation of various network devices. Such applications include, but are not limited to, Industrial Internet of Things (IIoT) and V2X applications (including vehicle-to-infrastructure, vehicle-to-network, vehicle-to-pedestrian applications, etc.).

[0018] The geolocation of a wireless network device (mobile or fixed) can be obtained based on estimating the distance between the wireless network device and other network devices with known locations, using hyperbolic or triangular positioning methods. Such distances can be estimated, for example, by measuring the time of flight or time of arrival of wireless signals transmitted between network devices. Wireless signals designed for these time measurements can be referred to as reference signals (as understood by one of ordinary skill in the art, such reference signals can be designed for purposes other than timing measurements, e.g., power control). In particular, assuming direct line-of-sight (LOS) wireless signal propagation, the distance between two wireless devices can be estimated by multiplying the time of flight of a reference signal transmitted between the two wireless devices by the propagation speed of the reference signal (e.g., close to the speed of light, denoted by c).

[0019] The LOS assumption for reference signals can not always hold. For example, as shown in Figure 1 in a wireless network such as a fourth generation (4G) and fifth generation (5G) cellular network, a mobile terminal 102 can be located in an urban environment where one or more base stations 104 relied on by the mobile terminal 102 for geolocation can not be in direct line-of-sight of the mobile terminal 102 (e.g., the direct LOS path 180 can be blocked by an obstacle such as a building). Thus, reference signals transmitted from these base stations can arrive at the mobile device after multiple reflections and / or diffractions 182. In other words, these reference signals can actually take a non-line-of-sight (NLOS) path (as shown by the solid arrows in Figure 1 instead of an LOS transmission path (as shown by the dashed arrows in Figure 1 As shown in Figure 1As shown, the transmission time t2 of the reference signal transmitted via the NLOS path will be longer than the transmission time t1 of the corresponding LOS signal.

[0020] Therefore, using the measured reference signal transmission time under the LOS assumption will lead to an overestimation of the distance between the mobile device and each base station, resulting in inaccurate hyperbolic or triangulation positioning of the mobile device. The excessive time delay due to the transmission path lengthening caused by multiple NLOS reflections and / or refractions can be expressed as Δτ = t2 - t1. Without specification, the average delay value Δτ ≈ 39 ns, for example, would result in a corresponding distance estimation error of approximately 12 meters, leading to unacceptable positioning accuracy in many of the aforementioned high-precision positioning applications. Therefore, it is crucial to estimate the excessive transmission time delay of the reference signal due to NLOS path lengthening and to use this transmission time delay to facilitate more accurate geolocation of the mobile device.

[0021] This disclosure generally relates to methods, apparatus, and systems for estimating the transmission time delay of a reference signal due to NLOS reflection and / or refraction, and for using the estimated transmission time delay to improve the geolocation accuracy of mobile devices in wireless communication networks. While the following example embodiments may be provided in the context of estimating the NLOS time delay of a reference signal in 4G or 5G cellular networks, the basic principles of this disclosure are generally applicable to geolocation of fixed or mobile wireless network devices and wireless infrastructure beyond 4G or 5G networks.

[0022] Network architecture

[0023] Figure 2 A portion of a wireless network 200 for implementing various embodiments of this disclosure is shown. For example... Figure 2 As shown, the wireless network includes user equipment or mobile terminal 102, base stations 104, 106, and 108, location anchors 130, 132, and 134, and location server 101. These different components of the wireless network 200 can communicate with each other through various wireless interfaces, as shown in 140. Some of these devices may alternatively communicate with each other through wired communication interfaces. For example, location server 101 may communicate with base stations 102-104 via a wired communication interface. Similarly, in addition to or alternative to wireless communication interfaces, location anchors 130-134 may also communicate with base stations and / or location server 101 via wired communication interfaces.

[0024] In the context of 4G (including LTE) or 5G cellular networks, base stations 102, 104, and 106 may include any type of radio access point within a radio access network (RAN), such as a 4G base station, a 5G NR base station, a 5G central unit base station, or a 5G distributed unit base station (various 5G base stations may alternatively be referred to as next-generation node B or gNB). Location anchors 130-134 may be distributed throughout the wireless network 200 to aid in the positioning of the mobile terminal. Location anchors 130-134 may be fixed at known geographical locations. Alternatively, location anchors 130-134 may be periodically repositioned, with their locations optimized to aid in the positioning of the mobile terminal. The UE or mobile terminal 102 may include, but is not limited to, mobile phones, smartphones, tablets, laptops, in-vehicle communication devices, roadside communication devices, sensor devices, smart appliances (e.g., televisions, refrigerators, and ovens), or other devices capable of wireless communication over the network.

[0025] like Figure 2 As shown, each of the mobile terminal 102, base stations 104-108, and positioning anchors 130-134 may include transceiver circuitry 114 coupled to one or more antennas 116 to enable wireless communication with other components of the network 200. The transceiver circuitry 114 may be coupled to one or more processors 120, which may also be coupled to memory 122 or other storage devices. Memory 122 may store instructions or code therein that, when read and executed by processor 120, enable processor 120 to perform various network functions. For example, these network functions may include those related to NLOS time delay estimation and positioning of the mobile terminal.

[0026] Furthermore, in the context of 4G or 5G cellular networks, the location server 101 (which may also be referred to as a location service node) can be implemented as a standalone server, module, logical entity, or functional unit within any other network node. For example, the location server 101 can be implemented as part of or within a Location Management Function (LMF), Serving Mobile Location Center (SMLC), Evolved Enhanced SMLC (E-SMLC), or Secure User Plane Location (SUPL) Location Platform (SLP), which assists in locating mobile terminals by collecting measurements and other information from various network nodes to manage the location of the mobile terminal. As another example, the location server 101 can be integrated with any other function of the core network of the underlying wireless communication network. Additionally, the location server 101 can be implemented as part of one or more access network nodes (e.g., one or more base stations). The location server 101 can be centralized or distributed. Figure 2As shown, the positioning server 101 can include one or more processors 110, which can be further coupled to a memory 112 or other storage device. The memory 112 can store therein instructions or code, which when read and executed by the processor 110, cause the processor 110 to implement various network functions. For example, these network functions can include functions related to NLOS time delay estimation and positioning of mobile terminals. In some implementations, the positioning server 101 can also include an interface for wireless communication with other components of the network 200.

[0027] Although only three base stations, three positioning anchors, one mobile terminal, and one positioning server are shown in Figure 2 , they are not limited thereto. Any number of these devices can be deployed and / or supported in the network 200.

[0028] Functionality of positioning anchors

[0029] The positioning anchors 130-134 can be configured to provide a reference NLOS time delay for positioning a mobile terminal adjacent to the positioning anchor, as the NLOS delay time of a reference signal from a base station at a neighboring network device in a geographic location is relevant. Figure 3 Example functionality of the positioning anchors 130-134 is shown. In some example implementations, the positioning anchors 130-134 can measure a transmission time of a wireless reference signal from the base stations 104-108 to determine a length of a signal transmission path from the base station to the positioning anchor and derive the NLOS time delay based on the measured signal transmission path length and known locations of the base station and the positioning anchor.

[0030] As a basic principle, since the geographic coordinates of each positioning anchor and each base station are known, a propagation time tl from a base station to a positioning anchor in a LOS environment can be calculated from the geographic coordinates of the base station and the positioning anchor. The NLOS time t2 can be estimated or measured according to a normal time of arrival (TOA) estimation / measurement method. Thus, the NLOS excess time delay (also referred to as NLOS time delay) can be estimated as Δτ = t2 - tl.

[0031] With reference to Figure 3 , the following example steps can be implemented to obtain the NLOS time delay at each positioning anchor:

[0032] Step 0: As shown in 302 of Figure 3 , a reference signal is transmitted from each of the i-th base stations to the j-th positioning anchor that receives the reference signal.

[0033] Step 1: The positioning server 101 transmits location information (x bi , ybi ).

[0034] Step 2: The jthpositioning anchor calculates the LOS propagation time between the ithbase station and the jthanchor as tj= sqrt[(x pi -x bi ) 2 +(y pi -y bi ) 2 ] / c, using the positioning anchor's location information (x pi , y pi ) and the ithbase station location information (x bi , y bi ).

[0035] Step 3: The TOA estimation algorithm is used to estimate the actual transmission time of the reference signal from the ithbase station to the jthpositioning anchor, t2.

[0036] Step 4: The jthpositioning anchor can optionally feedback the NLOS time delay (t2-t1) and the anchor's location information (x pi , y pi ) to the positioning server 101 or the mobile terminal, as shown in 310 and 320 of Figure 3 .

[0037] After the above process, the NLOS time delay between each base station and each positioning anchor can be obtained. The above process can be performed in real time as needed for mobile terminal positioning (an example mobile terminal positioning process is described below). Real-time measurement of NLOS can be beneficial as they track dynamic environmental changes and variations that can change the reference signal transmission path. Alternatively, these anchor NLOS time delays can be measured in advance, or they can be updated periodically.

[0038] Mobile terminal positioning using one or more positioning anchors

[0039] Once the NLOS time delays between base stations and positioning anchors are determined as described above, they can be used as reference NLOS time delays for mobile terminal positioning.

[0040] Referring to Figure 4 , in some example embodiments, the following steps can be taken to estimate the position of a mobile terminal:

[0041] Step 1: Transmit a reference signal from each base station to a mobile terminal 102 that receives the reference signal, as shown in 402 of Figure 4 .

[0042] Step 2: The mobile terminal 102 measures the Reference Signal Time Difference (RSTD) based on the TOA of the reference signals from the base stations. Such measurement information can be referred to as a set of timing measurement information. Such timing measurement information can include any type of timing measurement of the reference signals, including but not limited to TOA, RSTD, received-transmitted time difference or transmitted-received time difference of the reference signals.

[0043] Step 3: The mobile terminal feeds back the RSTD to the positioning server.

[0044] Step 4: The positioning server estimates the position of the mobile terminal based on the measured RSTD (or measured reference signal transmission path length, or the above general timing measurement information) and the known positions of the base stations.

[0045] Step 5: The positioning server selects one or more positioning anchors as reference anchors according to the positions of the one or more positioning anchors and the estimated position of the mobile terminal. For example, one or more positioning anchors closest to the estimated position of the mobile terminal can be selected as the reference anchors. Specifically, a single closest anchor can be selected as the reference anchor. The basic principle is that the anchor closest to the mobile terminal can have similar environmental conditions in terms of multiple reflections and / or refractions of the reference signals from the base stations, and thus can be used as a reference anchor for estimating the NLOS time delay in the reference signals of the mobile terminal.

[0046] Step 6: The positioning server obtains the reference NLOS time delay from the reference NLOS time delays of the one or more selected reference positioning anchors (e.g., averaged when more than one reference positioning anchor is selected, or directly using the reference NLOS delay time when a single reference positioning anchor is selected).

[0047] Step 7: The positioning server can use the reference NLOS time delay to compensate the above measured RSTD and / or TOA of the mobile terminal to obtain a compensated RSTD and / or a compensated TOA.

[0048] Step 8: The positioning server can then use the compensated RSTD and / or TOA and the known positions of the base stations to obtain the final position of the mobile terminal.

[0049] In some other example implementations for estimating the position of the mobile terminal, some of the above steps can be performed by the mobile terminal instead of the positioning server, as shown in the following steps:

[0050] Step 1: Transmit reference signals from each base station to the mobile terminal 102 receiving the reference signals, as shown in 402 of Figure 4

[0051] ​Step 2: The mobile terminal 102 measures the RSTD based on the TOA of the reference signals from the base stations.

[0052] Step 3: The mobile terminal estimates its position based on the measured RSTD (or measured reference signal transmission path length) and the known positions of the base stations.

[0053] Step 4: The mobile terminal selects one or more positioning anchors as reference anchors from the positions of the one or more positioning anchors and the estimated position of the mobile terminal. For example, one or more positioning anchors closest to the estimated position of the mobile terminal can be selected as reference anchors. In particular, a single closest anchor can be selected as a reference anchor. The basic idea is that the anchor closest to the mobile terminal can have similar environmental conditions in terms of multiple reflections and / or refractions of the reference signals from the base stations and can thus be used as a reference anchor for estimating the NLOS time delay in the reference signals of the mobile terminal.

[0054] Step 5: The mobile terminal obtains the reference NLOS time delay from the reference NLOS time delays of the one or more selected reference positioning anchors (e.g., averaged when more than one reference positioning anchor is selected or directly using the reference NLOS delay time when a single reference positioning anchor is selected).

[0055] Step 6: The mobile terminal can optionally compensate the measured RSTD and / or TOA with the reference NLOS time delay to obtain a compensated RSTD and / or a compensated TOA.

[0056] Step 7: The mobile terminal feeds back the measured or compensated RSTD / TOA and the reference NLOS time delay and the positions of the reference positioning anchors to a positioning server.

[0057] Step 8: If the compensation has not been done at the mobile terminal, the positioning server can use the reference NLOS time delay to compensate the above measured RSTD and / or TOA of the mobile terminal to obtain a compensated RSTD and / or a compensated TOA.

[0058] Step 9: The positioning server can then use the compensated RSTD and / or TOA and the known positions of the base stations to obtain the final position of the mobile terminal.

[0059] The above embodiments are merely examples. One of ordinary skill in the art recognizes that any other way of distributing the various steps among the various network elements can be derived based on the above principles and that these ways are within the scope of the present disclosure.

[0060] NLOS delay time and position estimation using multiple antennas

[0061] In some other embodiments, when the distance, relative position, or relative position offset between the multiple antennas are known, for example, it is assumed that the multiple antennas experience similar NLOS delay times with respect to the reference signals transmitted from the respective base stations due to the spatial proximity of the antennas, the multiple spatially separated antennas in the mobile terminal can be used to estimate the position of the mobile terminal. In particular, the multiple antennas can be used to estimate the NLOS delay times. The estimated NLOS delay times can then be used to compensate the measured RSTDs and / or TOAs for position estimation of the mobile terminal.

[0062] For example, the mobile terminal can include N spatially separated antennas at different positions. The relative positions of the different antennas are known. For example, the relative distance between two antennas can be known and denoted as d, and the NLOS delay times can be estimated according to the N antennas. For example, assuming two antennas are available, and according to the RSTD algorithm, the position (x, y) of the first antenna can be estimated based on equation (1) as:

[0063]

[0064] And the position (x', y') of the second antenna can be estimated based on equation (2) as:

[0065]

[0066] where x i,1 = x i - x1,y i,1 = y i - y1denotes the coordinate difference between the i-th base station in the n base stations and the reference base station (the first BTS); r i,1 + Δr = r i - r1denotes the distance difference between the i-th base station and the reference base station; and Δr = Δτχc denotes the distance difference corresponding to Δτ. Assuming that the antenna positions (x, y) and (x', y') are close to each other, it can be considered that their NLOS delay times are equal. In addition, the distance d between the first antenna and the second antenna is known:

[0067] (x - x') 2 + (y - y') 2 = d 2 .

[0068] In this way, Δτ or the NLOS delay time with respect to each base station can be obtained by using the above combined equations.

[0069] Referring Figure 5 In some example embodiments, the NLOS delay times can be estimated using the following steps:

[0070] Step 1: As shown in 502, the mobile station transmits a reference signal to the mobile terminal, and the mobile terminal receives the reference signal via multiple antennas 510 and 512. Figure 5

[0071] Step 2: The mobile terminal estimates the TOA between the jthbase station and the ithantenna ij .

[0072] Step 3: The mobile terminal feeds back the TOA ij and the relative distance between the antennas to the positioning server 101.

[0073] Step 4: The positioning server estimates the NLOS delay time Δτ based on the TOA ij and the relative distance between the antennas based on the above equation.

[0074] In some other embodiments, some of the above steps can be performed by the mobile terminal instead of the positioning server. For example, the estimation of the NLOS delay time can be performed by the mobile terminal instead of the positioning server. In this case, the mobile terminal can not need to perform the above step 3, and step 4 can be performed by the mobile terminal instead of the positioning server.

[0075] Once the NLOS delay time is obtained by the positioning server or the mobile terminal, and the mobile terminal feeds back the NLOS delay time to the positioning server, the position of the mobile terminal can be estimated in a similar manner as previously described. For example, in some embodiments, the positioning server can obtain the compensated TOA ij based on the measured TOA ij and the NLOS delay time Δτ. For example, the compensated TOA ij may be estimated as TOA ij - Δτ. The positioning server can then use the compensated TOA ij to compute the position of the mobile terminal.

[0076] The above embodiments are merely examples. It is understood by those of ordinary skill in the art that any other way of distributing the various steps among the various network elements described above can be derived based on the principles described above, and such ways are within the scope of the present disclosure.

[0077] Joint positioning of multiple mobile terminals at different locations

[0078] In some embodiments, multiple mobile terminals can be used to jointly estimate their positions. Referring to Figure 6 ​The mobile terminals, shown as 604-610, can be located at different locations. They can be located very close to each other. Therefore, it can be assumed that their NLOS time delays of the reference signals from the various base stations are the same. Further assuming that one antenna from each mobile terminal is used to receive the reference signals from the base stations (as shown in 602), the above multi-antenna approach can be used to estimate the NLOS time delays of the mobile terminals. Then, the location of each of the mobile terminals 604-610 can be estimated in a similar manner as discussed above for the location estimation of the multi-antenna mobile terminals, and as shown below:

[0079] Step 0: The positioning server determines a set of N mobile terminals for joint positioning. The selection of the set of mobile terminals can be based on spatial proximity and / or environmental similarity, for example.

[0080] Step 1: The ithmobile terminal estimates the TOA between the jthbase station and the ithmobile terminal ij .

[0081] Step 2: The ithmobile terminal estimates the distance d between the ithmobile terminal and the kthmobile terminal ik (This is equivalent to the distance d between the independent antennas described above, except that here the distance d ik is estimated instead of known).

[0082] Step 3: The mobile terminals can feedback the TOA ij and d ik to the positioning server.

[0083] Step 4: Then, the positioning server computes the NLOS delay time Δτ using similar equations described above for the multi-antenna implementation, based on the received TOA ij , d ik and the known locations of the base stations.

[0084] Step 5: The positioning server then obtains the compensated TOA ij , e.g., TOA ij - Δτ, based on the NLOS delay time Δτ and the TOA ij .

[0085] Step 6: The positioning server can then compute the locations of the mobile terminals using the compensated TOA ij and the known locations of the base stations.

[0086] Some of the mobile terminals described above can use multiple antennas. In this way, the above implementation and the multi-antenna implementation can be combined.

[0087] The above implementation methods are merely examples. It will be understood by those skilled in the art that any other way of distributing various steps among various network elements can be derived based on the above principles, and such ways are within the scope of this disclosure.

[0088] Direct solution of NLOS delay time

[0089] In some other implementations, the NLOS delay time can be directly approximated from the timing measurement of the reference signal. For example, suppose the estimated distance from the mobile terminal (x, y) to the i-th base station (xi, yi) is r. i Then the actual LOS distance is r. i -Δr i , where Δr i =Δτ i ×c is the NLOS delay time Δτ relative to the i-th base station. i The corresponding distance difference. Therefore:

[0090]

[0091] By subtracting the above formula (1) from formula (i) (i = 2, ..., n), the following result is obtained.

[0092]

[0093] in,

[0094]

[0095] Assume Δr i Much smaller than r i Then Δr i 2 -Δr1 2 ≈0, therefore:

[0096] f(Δr1,Δr i )≈r i 2 -r1 2 +K i -K1+2(Δr i -Δr1)

[0097] The above equation can be simplified to:

[0098]

[0099] Among them, a i,1 ≈0.5*(r i 2 -r1 2 +K i -K1), Δr i,1= Δr i - Δr1.

[0100] The set of equations above contains n-1 equations and n+1 variables (x, y, and Δr i,1 for i = 2,..., n). To obtain a solution for Δr i,1 , the two smallest Δr i,1 values can be approximated and brought into the equations, thereby reducing the number of variables to n-1, matching the number of equations. Thus, Δr i,1 needs to be ordered to determine the two smallest Δr i,1 . In some embodiments, two Δr i,1 are randomly selected in the equations above can be set to zero. For each random selection, the other Δr i,1 can be solved. Among all the solutions, the two smallest Δr i,1 can be determined as the two Δr i,1 solutions. These smallest Δr i,1 can then be input into the equations above, and the other Δr i,1 and (x, y) can then be obtained by solving these equations. In some other embodiments, the mobile terminal can determine the probability of it being in LOS communication with each base station, and rank the base stations according to these probabilities. The Δr i,1 corresponding to the two base stations with the highest LOS probability can be set to zero or some other small value in the equations above to solve for the remaining Δr i,1 . For example, the LOS probability of reference signal propagation between a base station and a terminal can be measured, e.g., based on the signal strength or power ratio of detected reference signals along various LOS and / or NLOS signal paths from the base station to the mobile terminal (the signal strength due to different signal paths can be obtained from time domain analysis of the detected reference signals). Alternatively, the measured TOA can be used as an indication of the LOS probability of a base station. For example, a smaller TOA can correspond to a higher LOS probability, as a base station closer to the mobile terminal can be subject to less NLOS delay. Once the LOS probabilities are ranked, the Δr i,1 corresponding to the two or more highest LOS probabilities (or highest priorities) can be set to zero or some other small value, and the Δr i,1 associated with the other reference signal transmissions can thus be solved based on the equations above. Once all Δr i,1 are determined, the NLOS delay times can be obtained through this example process. Once the NLOS delay times are obtained, the position of the mobile terminal can be estimated in accordance with the various embodiments described above.

[0101] The above description and drawings provide specific examples and implementations of the described subject matter. However, the described subject matter can be practiced in a variety of ways, and the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting as to a specific embodiment of the described subject matter. The scope of the described subject matter encompasses numerous alternatives, modifications and equivalents to the features and embodiments described and / or illustrated herein. For example, the subject matter can be implemented in hardware, software, firmware, non- transitory computer readable medium, or any combination thereof. For example, the method embodiments described above can be implemented by a component, a device, or a system including a memory and a processor, by executing computer code stored in the memory.

[0102] Throughout the specification and claims, the term "comprising" or variations such as "comprise" or "comprises" is not necessarily limited to instances in which every feature or element enumerated is required. Likewise, the term "sub-comprising" or variations such as "sub-comprise" or "sub- comprises" is not necessarily limited to instances in which every feature or element enumerated is required. Also, the use of "or" means "and / or" unless strictly stated otherwise. Moreover, the phrase "in one embodiment / implementation" as used herein does not necessarily refer to the same embodiment, although it can. Also, the phrase "in another embodiment / implementation" as used herein does not necessarily refer to a different embodiment, although it can. For example, the subject matter can be implemented in a variety of ways, such as in a method, device, system, or non-transitory computer-readable medium.

[0103] Generally, the terminology can be understood at least partially from a context in which the terminology is used. For example, terms such as "and", "or", or "and / or" as used herein can encompass a variety of items, including one of each item, one of multiple items, multiple of each item, etc. Similarly, the term "one or more" as used herein can describe any characteristic, structure, or property either in a singular sense or in a plural sense depending on the context in which the term is used. Similarly, terms such as "a", "an", or "the" as used herein can be understood to mean either a singular sense or a plural sense depending on the context in which the term is used. Also, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but instead can allow for existence of other factors not necessarily expressly described, again, depending on the context in which the term is used.

[0104] Reference throughout this specification to features, advantages, or similar language does not mean that all of those features and advantages in connection with the solution can be achieved in any single implementation. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one implementation of the solution. Thus, discussions of features and advantages, and similar language, throughout the specification may, but do not necessarily, refer to the same embodiment.

[0105] Furthermore, the described features, advantages, and characteristics of the solution can be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages can be recognized in certain embodiments that can not be present in all embodiments of the solution.

Claims

1. A method performed by a positioning service node in a wireless communication network, comprising: obtaining a set of timing measurement information associated with reference signals transmitted by a plurality of wireless network nodes and received by a mobile terminal; obtaining geographical positions of the plurality of wireless network nodes; obtaining an estimate of a time delay exceeding a corresponding line-of-sight, LOS, transmission time in a signal propagation time of the reference signals by selecting at least one anchor device from a plurality of anchor devices of the wireless communication network and obtaining the time delay from anchor time delays associated with the plurality of wireless network nodes and the selected at least one anchor device; compensating the set of timing measurement information with the estimated time delay to obtain compensated timing measurement information; and determining a geographical position of the mobile terminal based on the compensated timing measurement information and the geographical positions of the plurality of wireless network nodes. The plurality of anchor devices comprises a plurality of fixed network nodes distributed in the wireless communication network.

2. The method of claim 1, wherein, The anchor time delays associated with the at least one selected anchor device are predetermined and reported to the positioning service node by the at least one selected anchor device or estimated in real-time.

3. The method of claim 1, wherein, The anchor time delays associated with the at least one selected anchor device are predetermined by the positioning service node based on anchor reference signal timing measurements reported by the at least one selected anchor device.

4. The method of claim 1, wherein, Obtaining the anchor time delays comprises determining the anchor time delays as anchor signal propagation times of anchor reference signals transmitted from the plurality of wireless network nodes to the at least one selected anchor device exceeding corresponding anchor reference signal LOS transmission times.

5. The method of claim 1, wherein, The corresponding anchor reference signal LOS transmission times are determined based on the geographical positions of the plurality of wireless network nodes and the geographical positions of the at least one selected anchor device.

6. The method of claim 5, wherein, Selecting the at least one anchor device comprises selecting the at least one anchor device being geographically closest to an estimated geographical position of the mobile terminal.

7. The method of claim 1, wherein, Determining the estimated geographical position of the mobile terminal based on the set of timing measurement information and the geographical positions of the plurality of wireless network nodes.

8. The method of claim 7, wherein, Obtaining the anchor time delays associated with the plurality of wireless network nodes comprises obtaining the anchor time delays by averaging different anchor time delays associated with different anchor devices of the plurality of wireless network nodes and the at least one selected anchor device.

9. The method of claim 1, wherein, The set of timing measurement information comprises signal transmission times of reference signals from the plurality of wireless network nodes to the mobile terminal.

10. The method of claim 1, wherein, The set of timing measurement information is further associated with two or more different antennas of the mobile terminal.

11. The method of claim 1, wherein, The set of timing measurement information comprises signal transmission times of reference signals from the plurality of wireless network nodes to each of two or more different antennas of the mobile terminal.

12. The method of claim 11, wherein, 13. The method of claim 12, further comprising obtaining an inter-antenna spacing between the two or more different antennas. ​ 14. The method of claim 13, wherein, Obtaining the time delay comprises estimating a time delay in the signal propagation time of the reference signals beyond the respective LOS transmission time based on the set of timing measurement information, the inter-antenna distance and the geographical positions of the plurality of wireless network nodes.

15. The method of claim 1, further comprising receiving a second set of timing measurement information associated with reference signals transmitted by the plurality of wireless network nodes and received by a second mobile terminal, wherein, Obtaining the time delay associated with the mobile terminal comprises estimating the time delay based on the set of timing measurement information, the second set of timing measurement information, the geographical positions of the plurality of wireless network nodes and an estimated distance between the mobile terminal and the second mobile terminal.

16. The method of claim 15, wherein, The estimated distance between the mobile terminal and the second mobile terminal is derived from a first estimated position of the mobile terminal and a second estimated position of the second mobile terminal.

17. The method of claim 16, wherein: The first estimated position of the mobile terminal is obtained based on the set of timing measurement information and the geographical positions of the plurality of wireless network nodes; and The second estimated position of the second mobile terminal is obtained based on the second set of timing measurement information and the geographical positions of the plurality of wireless network nodes.

18. The method of claim 1, wherein, Obtaining the time delay comprises estimating the time delay based on the set of timing measurement information and NLOS delay times resolved from prioritizing NLOS delay times according to a LOS probability ranking of the reference signals propagating between the wireless network nodes and the mobile terminal and the geographical positions of the plurality of wireless network nodes ranked by the LOS probability.

19. The method of claim 18, wherein, The timing measurement information comprises RSTDs or TOAs and the LOS probability is determined based on the RSTDs or TOAs, wherein a smaller RSTD or TOA corresponds to a higher LOS probability.

20. A method performed by a mobile terminal, comprising: receiving reference signals from a plurality of wireless network nodes; measuring reference signal propagation times of the received reference signals; obtaining an estimated time delay in the reference signal propagation times beyond respective line-of-sight, LOS, transmission times, wherein the estimated time delay is obtained from an anchor device and the anchor device is selected from a plurality of candidate anchor devices based on an estimated distance of the anchor device to the mobile terminal; and transmitting the estimated time delay and the reference signal propagation times to a positioning service node or a compensated reference signal propagation time based on the reference signal propagation times compensated by the estimated time delay to enable the positioning service node to estimate a geographical position of the mobile terminal.

21. The method of claim 20, further comprising compensating the reference signal propagation times with the estimated time delay to obtain the compensated reference signal propagation time.

22. The method of claim 20, wherein, The estimated time delay is determined by the anchor device by determining an anchor time delay in an anchor signal propagation time of an anchor reference signal transmitted from the plurality of wireless network nodes to the anchor device beyond a respective anchor reference signal LOS transmission time.

23. The method of claim 20, wherein, Measuring the reference signal propagation times of the received reference signals comprises measuring the reference signal propagation times by at least two different antennas of the mobile terminal.

24. The method of claim 23, wherein, The obtaining the estimated time delay comprises determining the estimated time delay based on reference signal propagation times associated with the plurality of wireless network nodes and the at least two different antennas, geographical positions of the plurality of wireless network nodes, and distances between the at least two different antennas.

25. A method performed by an anchoring device, comprising: receiving a reference signal transmitted from a plurality of wireless network nodes; obtaining geographical positions of the plurality of wireless network nodes; determining a time delay in a signal propagation time of the reference signal exceeding a corresponding line-of-sight, LOS, transmission time; and transmitting the time delay to a positioning server or a mobile terminal to enable the positioning server or the mobile terminal to perform geographical positioning of the mobile terminal, wherein the anchoring device is selected from a plurality of candidate anchoring devices based on an estimated distance of the anchoring device to the mobile terminal.

26. The method of claim 25, further comprising transmitting a geographical position of the anchoring device to the positioning server or the mobile terminal to enable the positioning server or the mobile terminal to perform geographical positioning of the mobile terminal based on the time delay and the geographical position of the anchoring device.

27. The method of claim 25, wherein, determining a time delay in a signal propagation time of the reference signal exceeding a corresponding LOS transmission time comprises: determining the signal propagation time of the reference signal based on a reception time of the reference signal at the anchoring device; determining a LOS distance between the plurality of wireless network nodes and the anchoring device; and determining the time delay based on the signal propagation time and the LOS distance.

28. A network node comprising a processor, wherein, The processor is configured to implement the method according to any one of claims 1-19.

29. A mobile terminal comprising a processor, wherein, The processor is configured to implement the method according to any one of claims 20-24.

30. An anchoring apparatus comprising a processor, wherein, The processor is configured to implement the method according to any one of claims 25-27.

31. A computer program product comprising a non-transitory computer readable program medium having computer code stored thereon, the computer code, when executed by a processor, causes the processor to implement the method according to any one of claims 1 to 27.

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