WO2021030819A2

WO2021030819A2 - System and method for map-assisted location estimation

Info

Publication number: WO2021030819A2
Application number: PCT/US2020/062700
Authority: WO
Inventors: Arkady Molev-Shteiman; Elyes BALTI; Xiao-Feng Qi
Original assignee: Futurewei Technologies, Inc.
Priority date: 2020-12-01
Filing date: 2020-12-01
Publication date: 2021-02-18
Also published as: WO2021030819A3

Abstract

Location estimation for a communication device includes estimating a measured channel impulse response (CIR) associated with each of a plurality of sources based upon a reference signal, determining a time of arrival for a path for each source based upon the measured CIR, and determining combinations of the sources. A predicted location and a predicted time of departure is determined for each combination based upon a predetermined location associated with the source and the determined time of arrival. For each combination, a predicted CIR of the combination is determined based upon the predicted location and predicted time of departure, and a distance measure is determined between the measured CIR and the predicted CIR. A minimum distance from among the distance measures is determined. An estimated location of the communication device is determined based upon the predicted location of the communication device associated with the determined minimum distance.

Description

System and Method for Map-Assisted Location Estimation

TECHNICAL FIELD

The present disclosure relates generally to a system and method for digital communications, and, in particular embodiments, to a system and method for map-assisted location estimation.

BACKGROUND

Location estimation of user equipment (UE), particularly in indoor environments, has become a desirable feature for new communication standards. An example use case may include determining the location of a UE during an emergency. A conventional approach to indoor location estimation utilizes opportunistic signals received by the UE from distributed access points, such as Wi-Fi access points, within the environment. In this conventional approach, a time-of-arrival of signals received by the access points from the UE is determined and used in with access point location data to estimate a location of the UE. However, conventional location estimation assumes line of sight (LoS) propagation. When one or more access points are blocked by an object or multipath reflections occur within the environment, location estimation is problematic using conventional approaches.

Therefore, there is a need for systems and methods to provide accurate and reliable UE location estimation for use in environments subject to blocking and/or multipath reflections.

SUMMARY

Example embodiments provide for a system and method for map-assisted location estimation.

In accordance with an example embodiment, a method for map-assisted location estimation includes estimating, by a communication device, a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimating based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location. The method further includes determining, by the communication device, a time of arrival associated with at least one path between each source and the communication device, the determining based upon the measured CIR associated with the source, and determining, a plurality of combinations of the sources, each combination including one or more of the plurality of sources. The method further includes determining, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determining of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path, and determining, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure. The method further includes determining, for each combination, a distance measure between the measured CIR and the predicted CIR, determining a minimum distance from among the distance measures for the plurality of combinations, and determining an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

Optionally, in any of the preceding embodiments, the method further includes receiving, by the communication device, the at least one reference signal from each of the plurality of sources.

Optionally, in any of the preceding embodiments, the method further includes receiving, by the communication device, location information indicative of the predetermined location for each of the plurality of sources.

Optionally, in any of the preceding embodiments, the location information comprises coordinates associated with the predetermined location.

Optionally, in any of the preceding embodiments, the method further includes the coordinates comprise three-dimensional coordinates.

Optionally, in any of the preceding embodiments, the location information is received from a channel database.

Optionally, in any of the preceding embodiments, the method further includes determining a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

Optionally, in any of the preceding embodiments, determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

Optionally, in any of the preceding embodiments, determining the predicted CIR of the combination utilizes a ray-tracing function.

Optionally, in any of the preceding embodiments, the communication device comprises a user equipment (UE).

Optionally, in any of the preceding embodiments, each of the plurality of sources includes an access point.

In accordance with another example embodiment, a communication device, comprises a non- transitory memory storage comprising instructions, and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to estimate a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimate based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location. The one or more processors further execute instructions to determine a time of arrival associated with at least one path between each source and the communication device, the determination based upon the measured CIR associated with the source, determine a plurality of combinations of the sources, each combination including one or more of the plurality of sources, and determine, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determination of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path. The one or more processors further execute instructions to determine, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure, determine, for each combination, a distance measure between the measured CIR and the predicted CIR, determine a minimum distance from among the distance measures for the plurality of combinations, and determine an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

Optionally, in any of the preceding embodiments, the one or more processors further execute the instructions to receive the at least one reference signal from each of the plurality of sources.

Optionally, in any of the preceding embodiments, the one or more processors further execute the instructions to receive location information indicative of the predetermined location for each of the plurality of sources.

Optionally, in any of the preceding embodiments, the coordinates comprise three-dimensional coordinates.

Optionally, in any of the preceding embodiments, the method further includes the one or more processors further execute the instructions to determine a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

Optionally, in any of the preceding embodiments, the method further includes determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path. Optionally, in any of the preceding embodiments, determining the predicted CIR of the combination utilizes a ray-tracing function.

In accordance with another example embodiment, a non-transitory computer-readable media storing computer instructions, that when executed by one or more processors, cause the one or more processors to perform the steps of estimating, by a communication device, a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimate based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location, and determining, by the communication device, a time of arrival associated with at least one path between each source and the communication device, the determination based upon the measured CIR associated with the source. The one or more processors further perform the steps of determining, a plurality of combinations of the sources, each combination including one or more of the plurality of sources, and determining, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determination of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path. The one or more processors further perform the steps of determining, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure, determining, for each combination, a distance measure between the measured CIR and the predicted CIR, determining a minimum distance from among the distance measures for the plurality of combinations, and determining an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

Optionally, in any of the preceding embodiments, the computer instructions cause the processor to perform the step of receiving the at least one reference signal from each of the plurality of sources.

Optionally, in any of the preceding embodiments, the computer instructions cause the processor to perform the step of receiving, by the communication device, location information indicative of the predetermined location for each of the plurality of sources. Optionally, in any of the preceding embodiments, the computer instructions cause the processor to perform the step of determining a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

In accordance with another example embodiment, a communication device includes a memory storage comprising instructions, and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to perform a method as in any of the preceding embodiments.

Practice of the foregoing embodiments may provide for accurate and reliable communication device location estimation in environments subject to blocking and/or multipath reflections using a deterministic procedure that does not require initial knowledge of device location and may have a lower computational complexity than existing procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates a diagram of an embodiment wireless communications network;;

Figure 2 illustrates an example communication system for location estimation within a three- dimensional (3D) environment;

Figures 3A-3B illustrate example diagrams of a conventional location estimation procedure;

Figure 4 illustrates an example of line-of-sight (FoS) path extraction for a signal having a multipath signature according to example embodiments presented herein;

Figure 5 illustrates an example diagram of a blockage problem for four anchors location estimation;

Figures 6A-6B illustrate example diagrams of multipath signature location estimation;

Figure 7 illustrates an example diagram of four anchor location estimation in accordance with an embodiment;

Figure 8 illustrates an example diagram of anchor association according to an embodiment;

Figure 9 illustrates a flow diagram of first example operations occurring in a UE for location estimation without map assistance in accordance with an embodiment; Figure 10 illustrates an example diagram of a distance measurement between a measured CIR and a predicted CIR;

Figure 11 illustrates a flow diagram of second example operations occurring in a UE for location estimation with map assistance in accordance with an embodiment;

Figure 12 illustrates an example simulation environment for generating simulation results using map-assisted location estimation in accordance with one or more embodiments;

Figures 13A-13D illustrate simulation results for the simulation environment of Figure 12;

Figure 14 illustrates a flow diagram of third example operations occurring in a communication device for location estimation in accordance with an embodiment;

Figure 15 illustrates an example communication system;

Figures 16A and 16B illustrate example devices that may implement the methods and teachings according to this disclosure; and

Figure 17 is a block diagram of a computing system that may be used for implementing the devices and methods disclosed herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments are discussed in detail below that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the embodiments, and do not limit the scope of the disclosure.

FIG. 1 illustrates a network 100 for communicating data. The network 100 includes a base station 110 having a coverage area 101, a plurality of mobile devices 120, and a backhaul network 130. As shown, the base station 110 establishes uplink (dashed line) and/or downlink (dotted line) connections with the mobile devices 120, which serve to carry data from the mobile devices 120 to the base station 110 and vice-versa. Data carried over the uplink/downlink connections may include data communicated between the mobile devices 120, as well as data communicated to/from a remote-end (not shown) by way of the backhaul network 130. As used herein, the term “base station” refers to any component (or collection of components) configured to provide wireless access to a network, such as an enhanced base station (eNB), g node B (5G wireless), a macro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelessly enabled devices. Base stations may provide wireless access in accordance with one or more wireless communication protocols, e.g., long term evolution (LTE), LTE advanced (LTE-A), 5G Wireless, High Speed Packet Access (HSPA), Wi-Fi 802.1 la/b/g/n/ac, etc. As used herein, the term “mobile device” refers to any component (or collection of components) capable of establishing a wireless connection with a base station, such as a user equipment (UE), a mobile station (STA), and other wirelessly enabled devices. In some embodiments, the network 100 may comprise various other wireless devices, such as relays, low power nodes, etc.

Figure 2 illustrates an example communication system 200 for location estimation within a three- dimensional (3D) environment 210. The communication system 200 includes a UE 220, a first access point (AP0) 230, a second access point (API) 240, a third access point (AP2) 250, and a fourth access point (AP3) 260. Access points (APs). Each of the first AP 230, the second AP 240, the third AP 250, and the fourth AP 260 are located at known three-dimensional coordinates (x, y, z) within the 3D environment 210. In the communication system 200, an estimated location of the UE 220 within the 3D environment 210 is desired to be determined using a location estimation procedure as further described herein.

A point coordinates vector is defined as: p = [x, y,z\ (1)

The distance between two points is denoted as:

Figure 3A illustrates an example diagram 300 of a conventional location estimation procedure. In the conventional location estimation procedure a UE (TX) 302 is located within an environment having four APs including APs RX0306, RX1 308, RX2 308, and RX3 310. The four APs measure a time of arrival (ToA) of signals transmitted by the UE 302. The ToA-based location estimation algorithm requires four reference APs, also referred to herein as anchors k, with known coordinates. For uplink-based estimation, each anchor synchronously measures the ToA of a reference signal sent by the UE. For downlink-based estimation, the UE measures the ToA of reference signals that were simultaneously sent by each anchor.

A vector contains four anchor coordinates defined as:

^PA = [ PA (0) , PA (1), PA (2), PA (3)] (3) where each element p_A (k) is the anchor k coordinates.

A ToA vector is defined as:

T_A = [t_A (0) t_A (1) , t_A (2) , t_A (3)] (4) where t_A [k ) is the ToA of the reference signal from anchor k for downlink estimation or to anchor k for uplink estimation. The location of UE p_u and reference signal time of departure (ToD) t_u can be found as:

[Pu_, ^tu ] = SolveNav ( P_A,T_A ) (5) where SolveNav ( ) denotes resolving the navigation equation:

where c is the speed of light. The expression (6) contains four equations and four unknowns (TOD t_u and three UE coordinates p_U ).

In the example of Figure 3, from the location of each access point (anchor) k and the measured TOA ( x_{RX k} , y_{RX k} , y_{RX k},t_{RX k} ) , a location of the UE and time of departure for the signals

( x_{RX k} , y_{RX k} , y_{RX k} , t_{RX k} ) can be determined by resolving the navigation equation:

Figure 3B illustrates received signals 311 associated with each of APs RXO 306, RX1 308, RX2 308, and RX3 310. A received signal 312 associated with RX2308 has an amplitude hO(t) and a To A of t0, a received signal 314 associated with RX1 306 has an amplitude hl(t) and a To A of tl, a received signal 316 associated with RX3 310 has an amplitude h2(t) and a ToA of t2, and a received signal 318 associated with RXO 304 has an amplitude h3(t) and a ToA of t3. Using the known ToA values of t0, t1, t2, and t3 and known location coordinates of RXO 306, RX1 308, RX2 308, and RX3 310, the navigation equation (7) may be solved to determine an estimated location of UE 302.

Conventional four anchor location estimation is effective for line-of-sight (LoS) components, but is prone to error for non-LoS components such as for multipath signals. If a channel is sufficiently wideband, a multipath signal may be filtered by choosing only the first arriving path as the LoS path. Figure 4 illustrates an example 400 of LoS path extraction for a signal having a multipath signature 402. In the example of Figure 4, the multipath signature 402 includes four pulses 404, 406, 408 and 410 arriving at times t0, t1, t2, and t3, respectively. By performing a filtering operation 412, the first arriving path associated with ToA t0 is chosen as the LoS path.

However, when a LoS path is blocked, the first arriving path may be a reflected path. As a result, inserting the ToA associated with the reflected path in the navigation equation may cause a large error in location estimation. Moreover, no trivial solution exists to distinguish if the received signal includes a LoS component or not.

Figure 5 illustrates an example diagram 500 of a blockage problem for four anchors location estimation. In the example, a blocker 502 is positioned between the UE 302 and the AP RX0304. The blocker 502 is an object, such as a person or man-made object (signage, building or other structure), capable of blocking signal transmission between the UE and the AP RX 304. In the example of Figure 5, the blocking of AP RX0304 results in the ToA data associated with AP RX0304 being unknown. As a consequence, the location of the UE 302 cannot accurately be resolved using conventional four anchor location estimation.

Each location within an environment may have a unique channel impulse response (CIR), also referred to as a multipath signature. In non-LoS situations, knowledge of the multipath signature of different locations in the environment may be used to estimate location of a UE.

Figure 6A illustrates an example diagram 600 of multipath signature location estimation. A UE 602 transmits a signal and an AP 604 receives the signal from a direct path 606 and three reflected paths 608a-608c, each have a different associated ToA. As a result, a multipath signature 610 is produced as illustrated in Figure 6B.

A popular approach that employs multipath signatures for location estimation is that of artificial intelligence-based fingerprinting. An advantage of the artificial intelligence-based fingerprinting approach is that it has high robustness. However, articular intelligence-based fingerprinting requires a long training period that may not be practical in certain situations and is non- deterministic.

A deterministic approach for multipath signature location estimation is that of direct positioning in which an entire room space is scanned in 3D to find a location for which CIR prediction generating by a ray-tracing function is maximally close to channel estimation results. Direct positioning may significantly improve accuracy because it employs multipath information for location estimation. However, direct positioning has a large computational complexity and may only be usable when an initial location is predicted by other methods to improve location accuracy. Another deterministic method of location estimation that does not scan the entire space is based on angle of arrival (AoA) estimation and requires that the AP be equipped with an antenna array having multiple antennas.

In contrast to existing location estimation methods, the map-assisted location estimation procedures described herein with respect to various embodiments is fully deterministic, does not require initial knowledge of UE location, and has a lower complexity because it does not require space scanning. In addition, map-assisted location estimation procedures described herein with respect to various embodiments are based on ToA measurements and is suitable for use with APs having single antennas as well as antenna arrays. Accordingly, various embodiments described herein resolve the problem of location estimation with an insufficient number of reference signals, such as when some multipaths are blocked, and estimates location based on unique multipath signatures.

A multipath may be modeled as originating from an additional virtual (mirror) source such as modeling a ground bounce in mobile channels. The single bounce idea can be extended to more complex propagation scenarios where each reflecting surface requires an additional virtual source to model its contribution to the received signal. Multiple bounces can accounted for in a similar manner by adding more mirror sources.

A multi- AP channel is defined as a vector with length N _AP, where N _AP, is the total number of APs as follows:

H(t)1=[ h 0 ( t ) , h 1 ( t ) , ... , (t)] (8)

Each element m of this vector is the CIR of AP number m. For downlink signals, the channel may be represented as the superposition of real and mirror sources and may be expressed as:

where is the Dirac function, m is the receiver index, p_U is the location of the UE receiver, t_U, is the time of departure (ToD) of the reference signal according to the UE clock, p_{m k} is the location of the k- th source (real and mirror) of the AP m transmitter, and N_MP is the total number of sources associated with an AP.

The delay between points with locations P_u and p_{m k} is equal to:

The complex amplitude of paths between points with location P_u and p_{m k} is the product of the reflection coefficients experience by the path, free space path losses, and corresponding phase shift which is given by:

where l is the carrier wavelength, and r(p_u , p_{m k} ) is equal to:

where r_{m n} is the reflection coefficient of the n-th order reflector that gives rise to source k, N_K is the number of reflections, and v ( p_{m k} ) is the visibility sector of source with location p_{m k} .

The multi-source approach is more suitable for downlink channel representation because the location of virtual sources is static and can be precalculated. Due to channel reciprocity, the channel may be represented as the superposition of virtual transmitters (sources) and the superposition of virtual receivers (sinks), termed herein as a multisink representation.

Similar to the multisource channel, an uplink multisink channel can be expressed by Equation (8), where p_u is the location of the UE transmitter, and p_{m k} is the location of the virtual sink k associated with AP m receiver. The multi-sink approach is more suitable for uplink channel representation because the location of virtual sources is static and can be precalculated.

In accordance with various embodiments, information about the location of virtual sources/sinks can be stored into a channel database as information that in compressed form represents 3D map of the environment. The channel database may store information regarding both virtual and real sources/sinks. Virtual and real sources/sink are denoted herein with respect to various embodiments as virtual APs (VAs). Equation (9) expresses a channel as a function of UE location and information stored in the channel database (i.e., a 3D map of the environment. Equation (9) may be defined as a ray-tracing function of the form:

and a ray-tracing vector function may be defined as:

Assuming that each location has a unique CIR, also called a multipath signature, location information may be extracted from the multipath signature.

According to a spatial channel model given by Equation (9), each physical AP has a list of VA’s and one real AP. Denote p_s (m,k) as the location VA k that originates from physical AP m.

Denote the number of VAs that originate from physical AP m as n_P (m ) . For each physical AP, the list of ToAs for each path that arrives to this AP for uplink or from this AP for downlink is extracted from the CIR (i.e., multipath signature). Denote t_s ( in, k ) as the ToA of path k that belongs to AP m. Denote the number of ToAs that belong to AP m as n_T (m) . It should be noted that in general, the number of VAs is not necessarily equal to the ToAs list size. The number of ToAs may be smaller than the number of VAs due to blockage of part of the passes. The number of ToAs may also be large than the number of VAs due to reflections from unknown surface. For example, a person entering into a room may block some expected paths and also generate reflections that are unexpected. In accordance with various embodiments, VAs, sources for downlink or sinks for uplink, are used as four anchors to estimation a UE location according to the navigation equation (5).

Figure 7 illustrates an example diagram 700 of four anchor location estimation in accordance with an embodiment. A UE 702 receives downlink signals from one real source VA 0704, and three virtual sources VA 1 706, VA 2708, and VA 3710. A multipath channel presented as a superposition of the original and virtual sinks is represented using a ray-tracing function according to Equation (15) below:

Where. is the transmitter location . is the receiver sink k location is the sink k complex amplitude is the number of sinks is the reflection coefficient l of sink k is the number of reflection of sink k

An aspect of four anchor location estimation is determining which ToA is associated with each VA. To resolve association between APs and ToAs, one or more embodiments utilize inherent redundancy in the multipath environment. Figure 8 illustrates an example diagram 800 of anchor association according to an embodiment. For each selected anchor, several options exist to associate a ToA from the ToA list. A four anchors location association operation is given by the following expressions: p_A(k) = p_s(m_p(k),k_p(k)), k = 0,1, 2, 3 (16) t_A(k) = t_s(m_T(k),k_T(k)), k = 0,1, 2, 3 (17) where vector m_p, k_p, m_T, and k_T are elements of anchor association vectors:

M_p =[m_p(0),m_p(l),m_p(2),m_p(3)] (18)

K_p = [k_p (0) ,k_p(l),k_P(2),k_p (3)] (19)

M_T = \m_T (0) , m_T (1) , m_T (2) , m_T (3)] (20)

Anchor association operations (16) and (18) are denoted as: P_A =P_S(M_P,K_p ), T_A =T_S(M_T,K_t) (21) where P_s is the matrix of V A locations with elements p_s ( in, k ) and size N _AP X max ( n_T ) , T_s is the matrix of physical anchors paths ToAs with elements t_s ( m,k ) and size N_AP X max ( n_t ) , and N_AP is the physical AP number.

The VAs location matrix P_s is precalculated from the 3D-map of the environment and physical AP locations. The matrix of physical anchors paths ToA’s T_s is extracted from each of physical anchors channel estimation (i.e., multipath signature).

An AP and ToA association combination index is defined as n_C0MB and the total number of possible combinations as N_C0MB : n_COMB — 0,1, · · · , N_COMB — 1 (22)

The anchor association vectors that belong to the combination n_C0MB are defined as:

In a particular embodiment, a total number of combinations is given by:

Where: CNfunc is the combination number function

Sn is the vector of sinks number per receiver with lenght equal to N

Tn is the vector of ToAs number per receiver with lenght equal to N

N is the vectors length (at first iteration is equal to receivers number) An is the anchors number (at first iteration is equal to 4)

In accordance with one or more embodiments, a procedure for location estimation of an UE includes determining the possible N_C0MB combinations of anchor association. For each combination of anchor associations: the location is estimated by resolving the four anchors navigation Equation (5), regenerating the CIR according to the model of Equation (13), determining a distance between the received multipath signature and a reconstructed (or estimated) multipath signature using a distance measure. The estimated location of the UE is determined by choosing the location having the minimal distance among the distance measures of all of the combinations.

Figure 9 illustrates a flow diagram of first example operations 900 occurring in a UE for location estimation without map assistance in accordance with an embodiment. In the embodiment illustrated in Figure 9, no 3D map information indicating a location of each virtual AP is required. In 902, the UE 302 estimates a measured channel impulse response (CIR) for each of a number of APs in the environment. (t) is the channel impulse vector in which each element m of the

channel estimation results vector is the channel estimation of AP m as follows:

In 904, the UE 302 extracts a ToA matrix T_s including a ToA associated with one or paths between the UE 302 and an AP based upon the measured CIR associated with the AP. T_s is the matrix of physical anchors paths ToAs with elements t_s ( m , k ) . In 906, the UE 302 determines all possible anchor combinations n=0. 1, .. N_¥MB -1· When there is no 3D map information, the list of VAs that belong to each physical AP includes a single element that represents the real source/sink only. The path associated with the VA is the first arriving path. Therefore, the ToA associated with the VA is the ToA having the smallest value. In such as cause, the number of possible anchor combinations, N_COMB, is equal to:

In 908, for each possible anchor combination the UE 302 assigns the selected anchor combination:

P_A = P_RX (M_p (n), K_p (n)) (26)

In 910, the UE solves the navigation equation (5) for P_A and T_A to determine a predicted location P_u of the UE 302 and predicted reference signal ToD t_U for each path associated with the anchor combination: [ p_U , t_U ] = SolveNav ( P_A,T_A ) (27)

In 912, the UE 302 reconstructs the multipath signature to determine a predicted CIR of the anchor combination based upon the predicted location p_U and predicted ToD t_U using a ray-tracing function.

T_s=H(t) = RTF (pu(n), (n)) (28) In 914, the UE 302 determines a distance between the measured CIR and the predicted CIR using a distance measure. In a particular embodiment, the distance measure is of the form:

The distance measure of Equation (29) is based upon a sum of squares of a difference in between measured ToAs and estimated ToAs. In another particular embodiment, the distance measure may be of the form:

Figure 10 illustrates an example diagram 1000 of a distance measurement between a measured CIR and a predicted CIR for an anchor combination based upon measured ToAs and estimated To As using the distance measure of Equation (29).

Referring again to Figure 9, in 916, the UE 302 determines whether distance measures for each of the anchor combinations have been computed. If distance measures for all of the possible anchor combinations have not been determined, the UE 302 repeats 908, 910, 912, and 914 for the next anchor combination. If distance measures have been computed for all of the anchor combinations, in 918 the UE finds the distance measure having the minimal value, and determines that the predicted location associated with the determined minimal distance is the estimate location of the UE 302.

Figure 11 illustrates a flow diagram of second example operations 1100 occurring in a UE for location estimation with map assistance in accordance with an embodiment. In the embodiment illustrated in Figure 11, 3D map information indicating a location of each virtual AP is available. In 1102, the UE 302 extracts a virtual AP location matrix P_s for one or more of the physical APs based upon the location of the physical AP obtained from the 3D map of the environment. The virtual AP location matrix P_s includes the physical APs and the extracted virtual APs. In a particular embodiment, the 3D map information is received from a channel database.

In 1104, the UE 302 estimates a measured channel impulse response (CIR), (t) , for each of

the physical APs and virtual APs in the matrix P_s. In 1106, the UE 302 extracts a To A matrix T_s including a ToA associated with one or paths between the UE 302 and an AP based upon the measured CIR associated with the AP. T_s is the matrix of physical anchors paths ToAs with elements t_s (m,k) . In 1108, the UE 302 determines all possible anchor combinations n= 0, 1, ..., NCOMB -1·

In 1110, for each possible anchor combination the UE 302 assigns the selected anchor combination:

P_A = P_RX (M_p (n), K_p (n)) (31) In 1112, the UE solves the navigation equation (5) for P_A and T_A to determine a predicted location p_v of the UE 302 and predicted reference signal ToD t_U for each path associated with the anchor combination:

[Pu,t_U] = SolveNav ( P_A,T_A ) (32)

In 1114, the UE 302 reconstructs the multipath signature to determine a predicted CIR of the anchor combination based upon the predicted location p_v and predicted ToD t_U using a ray-tracing function.

H(t) = RTF (_Pu(n), (n)) (33)

In 1116, the UE 302 determines a distance between the measured CIR and the predicted CIR using a distance measure. In 1118, the UE 302 determines whether distance measures for each of the anchor combinations have been computed. If distance measures for all of the possible anchor combinations have not been determined, the UE 302 repeats 1110, 1112, 1114, and 1116 for the next anchor combination. If distance measures have been computed for all of the anchor combinations, in 1120 the UE finds the distance measure having the minimal value, and determines that the predicted location associated with the determined minimal distance is the estimate location of the UE 302.

Figure 12 illustrates an example simulation environment 1200 for generating simulation results using map-assisted location estimation in accordance with one or more embodiments. The simulation environment includes a rectangular room with a length 6m, a depth 4m, and a height 3.2m. The walls, ceiling, and floor of the room are flat and have a reflection coefficient equal to 1. A UE is disposed in the room. On each of the room walls, 9 APs with the following coordinates are deployed:

[0.0, 0.8, 2.4]

[0.8, 0.0, 2.0]

[6.0, 3.2, 2.8]

[5.2, 4.0, 1.6]

[0.0, 3.2, 2.6]

[5.2, 0.0, 2.2]

[6.0, 0.8, 3.0]

[0.8, 4.0, 1.8]

[3.0, 2.0, 3.2]

The number of active APs is a simulation parameter. A simulation condition includes that all second order reflections are ignored. Therefore, each AP has 6 VAs - one real for LoS and five virtual for reflections from 3 walls (opposite to AP, left and right from AP), the ceiling, and the floor. The location of the UE is random with uniform distribution in the room. The LoS path for each AP can be optionally blocked, and one path for each AP representing reflection from an unknown reflective surface can be optionally inserted.

Figures 13A-13D illustrate simulation results for the simulation environment of Figure 12. Figure 13A shows simulation results for a location estimation algorithm without map assistance when the FoS path is blocked for one AP. The number of APs is equal to 5, 6, 7 and 8. As shown in Figure 13 A, five APs are insufficient for reliable location estimation. An increase of the number of APs significantly improves location estimation quality. Eight APs is sufficient for reliable location estimation when one FoS path is blocked for one of the APs.

Figure 13B shows simulation results for a location estimation algorithm without MAP assistance when the FoS path is blocked for two APs. The number of APs is equal to 6, 7, 8 and 9. As shown in Figure 13B, six APs is insufficient for reliable location estimation. An increase in the number of APs again significantly improves location estimation quality. Eight APs is sufficient for reliable location estimation when one FoS path is blocked for one of the APs.

Figure 13C shows simulation results for map-assisted location estimation for a single AP with normal propagation, a single AP with blocked FoS path. A single AP with blocked FoS path and one extra path two APs with blocked FoS path and one extra path for each AP. Figure 13C illustrates that FoS blockage and inserting of extra paths cause performance degradation.

However, this degradation is not catastrophic. Adding an extra AP, even with blockage and extra path insertion, resolves these problems and significantly improves performance even relative to a single receiver with normal propagation.

Figure 13D shows simulation results for map-assisted location estimation for 1, 2, 3 and 4 APs with a blocked FoS path and one extra path for each AP. For reference, performance of convention FoS based on four anchors location estimation is also shown. Figure 13D illustrates that an increase of the number of APs improves performance of location estimation. When the number of APs is larger than 2, the map-assisted location estimation described herein with respect to various embodiments significantly outperforms conventional four anchors location estimation by incorporating environment information into the location estimation.

Figure 14 illustrates a flow diagram of third example operations 1400 occurring in a communication device for location estimation in accordance with an embodiment. In 1402, a communication device estimates a measured channel impulse response (CIR) associated with each of a plurality of sources based upon at least one reference signal associated with each of the plurality of sources. Each source has an associated predetermined location. In at least one embodiment, the communication device is a UE. In another embodiment, the communication device is an access point. In at least one embodiment, each of the plurality of sources includes an access point.

In at least one embodiment, the communication device receives the at least one reference signal from each of the plurality of sources. In at least one embodiment, the communication device receives location information indicative of the predetermined location for each of the plurality of sources from a channel database. In a particular embodiment, the location information includes coordinates, such as 3D coordinates, associated with the predetermined location.

In at least one embodiment, the communication device may determine one or more virtual sources associated with at least one of the sources, and the virtual sources are included in the plurality of sources for further calculations.

In 1404, the communication device determines a time of arrival associated with at least one path between each source and the communication device based upon the measured CIR associated with the source. In 1406, the communication device determines a plurality of combinations of the sources, each combination including one or more of the plurality of sources.

In 1408, the communication device determines, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

In at least one embodiment, determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

In 1410, the communication device determines, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure. In a particular embodiment, determining the predicted CIR of the combination utilizes a ray-tracing function. In 1412, the communication device determines for each combination, a distance measure between the measured CIR and the predicted CIR. In 1414, the communication device determines a minimum distance from among the distance measures for the plurality of combinations.

In 1416, the communication device determines an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

Figure 15 illustrates an example communication system 1500. In general, the system 1500 enables multiple wireless or wired users to transmit and receive data and other content. The system 1500 may implement one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), or non-orthogonal multiple access (NOMA).

In this example, the communication system 1500 includes UEs 1510a-1510c, radio access networks (RANs) 1520a-1520b, a core network 1530, a public switched telephone network (PSTN) 1540, the Internet 1550, and other networks 1560. While certain numbers of these components or elements are shown in Figure 1500, any number of these components or elements may be included in the system 1500.

The UEs 1510a-1510c are configured to operate or communicate in the system 1500. For example, the UEs 1510a- 1510c are configured to transmit or receive via wireless or wired communication channels. Each UE 1510a-1510c represents any suitable end user device and may include such devices (or may be referred to) as a user equipment or device (UE), wireless transmit or receive unit (WTRU), mobile station, fixed or mobile subscriber unit, cellular telephone, personal digital assistant (PDA), smartphone, laptop, computer, touchpad, wireless sensor, or consumer electronics device such as a tablet, interactive (“smart”) watch or other interactive user wearable device, and the like.

The RANs 1520a-1520b here include base stations 1570a-1570b, respectively. Each base station 1570a-1570b is configured to wirelessly interface with one or more of the UEs 1510a-1510c to enable access to the core network 1530, the PSTN 1540, the Internet 1550, or the other networks 1560. For example, the base stations 1570a-1570b may include (or be) one or more of several well-known devices, such as a base transceiver station (BTS), a Node-B (NodeB), an evolved NodeB (eNodeB), a Next Generation (NG) NodeB (gNB), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router. The UEs 1510a-1510c are configured to interface and communicate with the Internet 1550 and may access the core network 1530, the PSTN 1540, or the other networks 1560.

In the embodiment shown in Figure 15, the base station 1570a forms part of the RAN 1520a, which may include other base stations, elements, or devices. Also, the base station 1570b forms part of the RAN 1520b, which may include other base stations, elements, or devices. Each base station 1570a-1570b operates to transmit or receive wireless signals within a particular geographic region or area, sometimes referred to as a “cell.” In some embodiments, multiple-input multiple- output (MIMO) technology may be employed having multiple transceivers for each cell.

The base stations 1570a-1570b communicate with one or more of the UEs 1510a-1510c over one or more air interfaces 1590 using wireless communication links. The air interfaces 1590 may utilize any suitable radio access technology. It is contemplated that the system 1500 may use multiple channel access functionality, including such schemes as described above. In particular embodiments, the base stations and UEs implement 5G New Radio (NR), LTE, LTE-A, or LTE-B. Of course, other multiple access schemes and wireless protocols may be utilized.

The RANs 1520a-1520b are in communication with the core network 1530 to provide the UEs 1510a- 1510c with voice, data, application, Voice over Internet Protocol (VoIP), or other services. Understandably, the RANs 1520a-1520b or the core network 1530 may be in direct or indirect communication with one or more other RANs (not shown). The core network 1530 may also serve as a gateway access for other networks (such as the PSTN 1540, the Internet 1550, and the other networks 1560). In addition, some or all of the UEs 1510a- 1510c may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies or protocols. Instead of wireless communication (or in addition thereto), the UEs may communicate via wired communication channels to a service provider or switch (not shown), and to the Internet 1550.

Although Figure 15 illustrates one example of a communication system, various changes may be made to Figure 15. For example, the communication system 1500 could include any number of UEs, base stations, networks, or other components in any suitable configuration.

Figures 16A and 16B illustrate example devices that may implement the methods and teachings according to this disclosure. In particular, Figure 16A illustrates an example UE 1610, and Figure 16B illustrates an example base station 1670. These components could be used in the system 1500 or in any other suitable system.

As shown in Figure 16 A, the UE 1610 includes at least one processing unit 1600. The processing unit 1600 implements various processing operations of the UE 1610. For example, the processing unit 1600 could perform signal coding, data processing, power control, input/output processing, or any other functionality enabling the UE 1610 to operate in the system 1500. The processing unit 1600 also supports the methods and teachings described in more detail above. Each processing unit 1600 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 1600 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

The UE 1610 also includes at least one transceiver 1602. The transceiver 1602 is configured to modulate data or other content for transmission by at least one antenna or NIC (Network Interface Controller) 1604. The transceiver 1602 is also configured to demodulate data or other content received by the at least one antenna 1604. Each transceiver 1602 includes any suitable structure for generating signals for wireless or wired transmission or processing signals received wirelessly or by wire. Each antenna 1604 includes any suitable structure for transmitting or receiving wireless or wired signals. One or multiple transceivers 1602 could be used in the UE 1610, and one or multiple antennas 1604 could be used in the UE 1610. Although shown as a single functional unit, a transceiver 1602 could also be implemented using at least one transmitter and at least one separate receiver.

The UE 1610 further includes one or more input/output devices 1606 or interfaces (such as a wired interface to the Internet 1550). The input/output devices 1606 facilitate interaction with a user or other devices (network communications) in the network. Each input/output device 1606 includes any suitable structure for providing information to or receiving information from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen, including network interface communications.

In addition, the UE 1610 includes at least one memory 1608. The memory 1608 stores instructions and data used, generated, or collected by the UE 1610. For example, the memory 1608 could store software or firmware instructions executed by the processing unit(s) 1600 and data used to reduce or eliminate interference in incoming signals. Each memory 1608 includes any suitable volatile or non-volatile storage and retrieval device(s). Any suitable type of memory may be used, such as random access memory (RAM), read only memory (ROM), hard disk, optical disc, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like.

As shown in Figure 16B, the base station 1670 includes at least one processing unit 1650, at least one transceiver 1652, which includes functionality for a transmitter and a receiver, one or more antennas 1656, at least one memory 1658, and one or more input/output devices or interfaces 1666. A scheduler, which would be understood by one skilled in the art, is coupled to the processing unit 1650. The scheduler could be included within or operated separately from the base station 1670. The processing unit 1650 implements various processing operations of the base station 1670, such as signal coding, data processing, power control, input/output processing, or any other functionality. The processing unit 1650 can also support the methods and teachings described in more detail above. Each processing unit 1650 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 1650 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

Each transceiver 1652 includes any suitable structure for generating signals for wireless or wired transmission to one or more UEs or other devices. Each transceiver 1652 further includes any suitable structure for processing signals received wirelessly or by wire from one or more UEs or other devices. Although shown combined as a transceiver 1652, a transmitter and a receiver could be separate components. Each antenna 1656 includes any suitable structure for transmitting or receiving wireless or wired signals. While a common antenna 1656 is shown here as being coupled to the transceiver 1652, one or more antennas 1656 could be coupled to the transceiver(s) 1652, allowing separate antennas 1656 to be coupled to the transmitter and the receiver if equipped as separate components. Each memory 1658 includes any suitable volatile or non volatile storage and retrieval device(s). Each input/output device 1666 facilitates interaction with a user or other devices (network communications) in the network. Each input/output device 1666 includes any suitable structure for providing information to or receiving/providing information from a user, including network interface communications.

Figure 17 is a block diagram of a computing system 1700 that may be used for implementing the devices and methods disclosed herein. For example, the computing system can be any entity of UE, access network (AN), mobility management (MM), session management (SM), user plane gateway (UPGW), or access stratum (AS). Specific devices may utilize all of the components shown or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The computing system 1700 includes a processing unit 1702. The processing unit includes a central processing unit (CPU) 1714, memory 1708, and may further include a mass storage device 1704, a video adapter 1710, and an EO interface 1712 connected to a bus 1720.

The bus 1720 may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, or a video bus. The CPU 1714 may comprise any type of electronic data processor. The memory 1708 may comprise any type of non-transitory system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In an embodiment, the memory 1708 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs.

The mass storage 1704 may comprise any type of non-transitory storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus 1720. The mass storage 1704 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, or an optical disk drive.

The video adapter 1710 and the EO interface 1712 provide interfaces to couple external input and output devices to the processing unit 1702. As illustrated, examples of input and output devices include a display 1718 coupled to the video adapter 1710 and a mouse, keyboard, or printer 1716 coupled to the I/O interface 1712. Other devices may be coupled to the processing unit 1702, and additional or fewer interface cards may be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for an external device.

The processing unit 1702 also includes one or more network interfaces 1706, which may comprise wired links, such as an Ethernet cable, or wireless links to access nodes or different networks. The network interfaces 1706 allow the processing unit 1702 to communicate with remote units via the networks. For example, the network interfaces 1706 may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/receive antennas. In an embodiment, the processing unit 1702 is coupled to a local-area network 1722 or a wide-area network for data processing and communications with remote devices, such as other processing units, the Internet, or remote storage facilities.

It should be appreciated that one or more steps of the embodiment methods provided herein may be performed by corresponding units or modules. For example, a signal may be transmitted by a transmitting unit or a transmitting module. A signal may be received by a receiving unit or a receiving module. A signal may be processed by a processing unit or a processing module. Other steps may be performed by an estimating unit/module and/or a determining unit/module. The respective units or modules may be hardware, software, or a combination thereof. For instance, one or more of the units or modules may be an integrated circuit, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

Moreover, the scope of the disclosure is not intended to be limited to the particular embodiments described herein, as one of ordinary skill in the art will readily appreciate from this disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

WHAT IS CLAIMED IS:

1. A method, comprising: estimating, by a communication device, a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimating based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location; determining, by the communication device, a time of arrival associated with at least one path between each source and the communication device, the determining based upon the measured CIR associated with the source; determining, by the communication device, a plurality of combinations of the sources; determining, by the communication device for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determining of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path; determining, by the communication device for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure; determining, by the communication device for each combination, a distance measure between the measured CIR and the predicted CIR; determining, by the communication device, a minimum distance from among the distance measures for the plurality of combinations; and determining, by the communication device, an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

2. The method of claim 1, further comprising: receiving, by the communication device, the at least one reference signal from each of the plurality of sources.

3. The method of any of claims 1-2, further comprising: receiving, by the communication device, location information indicative of the predetermined location for each of the plurality of sources.

4. The method of claim 3, wherein the location information comprises coordinates associated with the predetermined location.

5. The method of claim 4, wherein the coordinates comprise three-dimensional coordinates.

6. The method of claim 3, wherein the location information is received from a channel database.

7. The method of any of claims 1-6, further comprising: determining a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

8. The method of any of claims 1-7, wherein determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

9. The method of any of claims 1-8, wherein determining the predicted CIR of the combination utilizes a ray-tracing function.

10. The method of any of claims 1-9, wherein the communication device comprises a user equipment (UE).

11. The method of any of claims 1-10, wherein each of the plurality of sources includes an access point.

12. A communication device, comprising: a non-transitory memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to: estimate a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimate based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location; determine a time of arrival associated with at least one path between each source and the communication device, the determination based upon the measured CIR associated with the source; determine a plurality of combinations of the sources, each combination including one or more of the plurality of sources; determine, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determination of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path; determine, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure; determine, for each combination, a distance measure between the measured CIR and the predicted CIR; determine a minimum distance from among the distance measures for the plurality of combinations; and determine an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

13. The communication device of claim 12, the one or more processors further executing the instructions to receive the at least one reference signal from each of the plurality of sources.

14. The communication device of any of claims 12-13, the one or more processors further executing the instructions to receive location information indicative of the predetermined location for each of the plurality of sources.

15. The communication device of claim 14, wherein the location information comprises coordinates associated with the predetermined location.

16. The communication device of claim 15, wherein the coordinates comprise three- dimensional coordinates.

17. The communication device of claim 14, wherein the location information is received from a channel database.

18. The communication device of any of claims 12-17, the one or more processors further executing the instructions to determine a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

19. The communication device of any of claims 12-18, wherein determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

20. The communication device of any of claims 12-19, wherein determining the predicted CIR of the combination utilizes a ray-tracing function.

21. The communication device of any of claims 12-20, wherein the communication device comprises a user equipment (UE).

22. The communication device of any of claims 12-21, wherein each of the plurality of sources includes an access point.

23. A non-transitory computer-readable media storing computer instructions, that when executed by one or more processors, cause the one or more processors to perform the steps of: estimating, by a communication device, a measured channel impulse response (CIR) associated with each of a plurality of sources, the estimating based upon at least one reference signal associated with each of the plurality of sources, each source having an associated predetermined location; determining, by the communication device, a time of arrival associated with at least one path between each source and the communication device, the determining based upon the measured CIR associated with the source; determining, a plurality of combinations of the sources, each combination including one or more of the plurality of sources; determining, for each combination, a predicted location for the communication device and a predicted time of departure from the source to the communication for each path associated with each of the sources of the combination, the determining of predicted location based upon the predetermined location associated with the source and the determined time of arrival associated with the path; determining, for each combination, a predicted CIR of the combination based upon the predicted location and predicted time of departure; determining, for each combination, a distance measure between the measured CIR and the predicted CIR; determining a minimum distance from among the distance measures for the plurality of combinations; and determining an estimated location of the communication device based upon the predicted location of the communication device associated with the determined minimum distance.

24. The non-transitory computer readable medium of claim 23, the computer instructions cause the processor to perform the step of receiving the at least one reference signal from each of the plurality of sources.

25. The non-transitory computer readable medium of any of claims 23-24, the computer instructions cause the processor to perform the step of receiving, by the communication device, location information indicative of the predetermined location for each of the plurality of sources.

26. The non-transitory computer readable medium of any of claims 23-25, the computer instructions cause the processor to perform the step of determining a virtual source associated with at least one of the sources, wherein the virtual source is included in the plurality of sources.

27. The non-transitory computer readable medium of any of claims 23-26, wherein determining the predicted location predicted time of departure comprises solving a navigation equation based upon the predetermined location associated with the source and the determined time of arrival associated with the path.

28. A communication device, comprising: a memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the one or more processors execute the instructions to: perform the method as in any of claims 1-11.