Wireless Station Ranging Using Channel State

Abstract

Techniques are described for using channel state information to determine a distance between a wireless station (STA) and a wireless access point (AP). The AP determines channel state information corresponding to the STA. The AP determines one or more fine timing measurement (FTM) parameters based on the channel state information. Multiple FTM messages are transmitted between the AP and the STA based on the one or more FTM parameters. The STA is configured to determine an estimated distance to the AP based on the multiple FTM messages.

Description

Technical Field

[0001] Embodiments presented in this disclosure generally relate to wireless communication. More specifically, one or more embodiments disclosed herein relate to determining a distance between a wireless station and a wireless access point using channel state information. Background Art

[0002] Fine Timing Measurement (FTM) techniques can allow an initiating wireless station (STA) to range to a responding STA and calculate the location of the initiating STA. The initiating STA can be any suitable wireless device, including a laptop computer, a smart phone, a tablet computer, other suitable user equipment, or a wireless network infrastructure device. The responding STA can also be any suitable wireless device, but in an embodiment, the responding STA is a wireless access point (AP) that participates in the ranging process by time-stamping the required wireless messages and negotiating distance parameters, including burst size, burst frequency, etc. For example, the AP can time-stamp a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit (PPDU).

[0003] However, the initiating STA does not have access to the AP's knowledge of the wireless network structure and radio frequency (RF) conditions. This may require the initiating STA to seek an excessive number of ranging requests from the AP. For example, the number of ranging requests for all initiating STAs can be determined during laboratory testing regardless of the environment to ensure that ranging is accurate enough (e.g., sufficient for accurate ranging in the most stringent environment) in the vast majority (e.g., 99.9%) of the envisioned deployments. But this may result in unnecessary message transmission because most initiating STAs are actually located in less stringent environments and do not actually require so many requests to determine the distance to the AP. This excessive ranging, which greatly exceeds the number of requests actually required to characterize the environment and determine the distance from the initiating STA to the AP in most deployments, is not desirable. Such excessive ranging wastes scarce WiFi propagation time, causes unplanned contention, and degrades the user's Quality of Experience (QoE). Additionally, ranging may be inaccurate, especially in a reflective environment. Brief Description of the Drawings

[0004] To be able to understand in detail the manner in which the above-recited features of the present disclosure can be obtained, a more specific description of the present disclosure briefly summarized above can be made by reference to the embodiments, some of which are illustrated in the drawings. However, it should be noted that the drawings illustrate typical embodiments and should not be considered restrictive; other equivalent embodiments are contemplated.

[0005] Figure 1 Determining the distance between a STA and an AP is shown according to one embodiment.

[0006] Figure 2 is a schematic diagram showing message transmission of FTM technology according to an embodiment.

[0007] Figure 3 is a block diagram showing a wireless STA and an AP according to an embodiment.

[0008] Figure 4 is a flowchart for ranging between a STA and an AP using FTM and channel quality according to an embodiment.

[0009] Figure 5 is a flowchart for determining channel quality according to an embodiment.

[0010] Figure 6 is a flowchart for improved ranging between a STA and an AP in a reflective environment according to an embodiment.

[0011] Figures 7A to 7B shows the position estimation of a wireless STA among multiple APs according to an embodiment.

[0012] For ease of understanding, the same reference numerals are used whenever possible to identify the same elements shared by the drawings. It is contemplated that the elements disclosed in one embodiment can be beneficially used in other embodiments without specific recitation. Detailed Description

[0013] Overview

[0014] The embodiments described herein include a method. The method includes determining channel state information at a wireless AP corresponding to a STA. The method further includes determining one or more FTM parameters at the AP based on the channel state information. The method further includes transmitting a plurality of FTM messages between the AP and the STA based on the one or more FTM parameters, wherein the STA is configured to determine an estimated distance to the AP based on the plurality of FTM messages.

[0015] The embodiments further include a wireless AP, which includes a processor and a memory storing a program. When the program is executed on the processor, operations are performed. The operations include determining channel state information corresponding to a wireless STA. The operations further include determining one or more FTM parameters based on the channel state information. The operations further include transmitting a plurality of FTM messages between the AP and the STA based on the one or more FTM parameters, wherein the STA is configured to determine an estimated distance to the AP based on the plurality of FTM messages.

[0016] The embodiment further includes a wireless STA, which includes a processor and a memory storing a program. When the program is executed on the processor, operations are performed. The operations include receiving, from a wireless AP, one or more FTM parameters, where the AP is configured to determine one or more FTM parameters based on channel state information corresponding to the STA. The operations further include transmitting a plurality of FTM messages between the STA and the AP based on the one or more FTM parameters. The operations further include determining an estimated distance to the AP based on the plurality of FTM messages.

[0017] Example embodiment

[0018] In an embodiment, ranging between any wireless STA and AP can be improved by using channel quality observations to determine FTM ranging parameters and improve FTM calculations for another arbitrary STA. For example, the AP can use an angle of arrival (AoA) antenna to determine general channel quality characteristics of a set of arbitrary STAs. This channel quality information can be used to negotiate FTM parameters, thereby improving ranging from the STA to the AP while avoiding unnecessary messaging. FTM is merely an example of a suitable ranging technique, and other techniques can be used. Additionally, the channel quality information can be used to improve FTM calculations.

[0019] In an embodiment, the AP can include an AoA analysis feature that can be used to capture channel state information (CSI) on n antennas (e.g., 32 antennas). The AP can compare the observed CSI of a given antenna communicating with the STA to a reference value and estimate the relative position of the STA and the AP. This can allow the AP to estimate the position of a remote STA, but does not help the STA measure its relative position to the AP because the STA does not have access to the channel state information.

[0020] However, the CSI can provide information about the deployment environment of the AP. For example, the CSI can be used to distinguish an AP with good line of sight (LOS) to the STA in a high-ceiling open space from an AP with limited LOS or non-line-of-sight (NLOS) in a low-ceiling, multi-compartment environment. The CSI can also be used to identify the stability of the wireless channel experienced by the STA (e.g., stationary versus unstable). In an embodiment, by comparing continuously measured CSI and the temporal correlation of the CSI trajectory of a given client, the AP can identify whether the position of a given STA remains unchanged (stationary) or is moving (unstable).

[0021] In an embodiment, this CSI information can be used to improve ranging using FTM or other suitable ranging techniques. For example, when the STA is not moving, a single longer burst of FTM messaging may be sufficient and multiple bursts may not be required. As another example, when the STA is moving, a series of shorter bursts of FTM messaging may be more effective in capturing the peaks and valleys of an unstable mobile channel.

[0022] Furthermore, in an embodiment, the CSI profile on a subcarrier of a given STA can indicate whether the wireless propagation environment includes multiple paths (e.g., reflected in multiple peaks and valleys of the CSI in the frequency domain) or is dominated by a direct LOS path (e.g., reflected in a relatively flat CSI profile in the frequency domain). This can be used to further improve ranging. For example, as described above, CSI can be used to distinguish an AP with a direct LOS to the STA from an AP with an NLOS to the STA. In the case where the AP estimates a direct LOS to the STA, a small number of short FTM bursts can be used, but in the case where the AP estimates an NLOS, a large number of short FTM bursts can be used.

[0023] When the AP estimates multiple paths (e.g., reflections), the STA may overestimate the distance to the AP by using FTM because the signal will take longer to propagate between the STA and the AP due to reflections. In this example, the randomness of the signal can be used to estimate the extent of the multipath delay spread and improve the distance estimate from FTM (e.g., by modifying the timestamp values of the reflected multipath delay spread included during FTM messaging). This provides more accurate ranging by the STA.

[0024] Figure 1 Determining the distance between a STA and an AP according to one implementation is shown. The indoor environment 100 includes multiple APs 102A - H and multiple STAs 104A - C. Each STA 104A - C can determine its distance to an AP using FTM techniques (e.g., by exchanging timestamped messages). Example FTM techniques are discussed in more detail with respect to Figure 2 For example, STA 104A can use FTM techniques to estimate the length of the distance 110 between STA 104A and AP 102A.

[0025] STA 104A can similarly use FTM technology to estimate the distance 112 to AP 102H. STA 104B can use FTM technology to estimate the distance 114 to AP 102G. STA 104C can use FTM technology to estimate the distance 116 to AP 102C. The STA can use this location information for a variety of management purposes, including selecting an AP for connection and configuring various radio transmission and other parameters. The location information can also be used for a variety of application purposes, including augmented reality, social networking, healthcare monitoring, inventory control, etc.

[0026] Figure 2 is a schematic diagram showing message transmission of FTM technology according to an embodiment. As described above, FTM is merely an example of a suitable ranging technology, and other technologies may be used instead of or in addition to FTM. In an embodiment, FTM is initiated by STA 204 to determine the distance to AP 202. The clocks of STA 204 and AP 202 are not synchronized, so the STA and the AP must exchange a series of timestamps to identify the time it takes for a wireless signal (e.g., a WiFi signal) to propagate between STA 204 and AP 202. This time can be used to estimate the distance between STA 204 and AP 202 because the time it takes for the signal to travel that distance is proportional to that distance (e.g., based on the speed of light).

[0027] STA 204 transmits an FTM request 210 to AP 202. AP 202 responds with an Ack 212 (e.g., an acknowledgment). In an embodiment, Ack 212 includes FTM parameters determined by AP 202. These parameters will be discussed further below. Additionally, in an embodiment, STA 204 and AP 202 can negotiate the FTM parameters, thus exchanging messages identifying the parameters to be used.

[0028] At time T1, AP 202 transmits an FTM ping 214 to STA 204. STA 204 receives the FTM ping 214 at time T2. At time T3, STA 204 transmits an Ack 216. Then, AP 202 transmits an FTM ping 218 to STA 204 at time T5. This FTM ping 218 includes timestamps T1 and T4 identifying the times when AP 202 transmitted FTM ping 214 and received Ack 216.

[0029] STA 204 receives the FTM ping 214 at time T6. Then STA 204 can use the timestamps T1, T2, T3, and T4 (T1 and T4 are received from AP 202, and T2 and T3 are locally recorded by STA) to calculate the round-trip time of the message transmission between STA 204 and AP 202. In an embodiment, this can be used to estimate the distance between STA 204 and AP 202 using the following equation: 2 * distance = ((T4 - T1) - (T3 - T2)) * c. In this equation, c is the speed of light, (T4 - T1) calculates the total round-trip time, and (T3 - T2) removes the turnaround time between receiving the FTM ping 214 and transmitting the Ack 216 at the STA.

[0030] However, in an embodiment, due to potential interference, movement of the STA, measurement errors, etc., the round-trip time measurement results may not be precise enough. Therefore, repeated measurements can be used to improve the accuracy of the distance estimate.

[0031] As Figure 2 shown, two additional round-trips can be used to improve the accuracy: FTM Ping 218 and Ack 220, and FTM Ping 222 and Ack 224. In an embodiment, the final FTM Ping 226 provides the timestamps T9 and T12 to STA 204 to allow calculation of the round-trip time between FTM Ping 222 and Ack 224, but the propagation time of the FTM Ping 226 itself is not used for distance estimation. Figure 2 The two additional round-trips shown are for illustration only. More or fewer round-trips can be used. Additionally, many different parameters can be configured, including the time between round-trips, the number of round-trips in a burst, etc.

[0032] Figure 3 is a block diagram showing a wireless STA 300 and an AP 350 according to an embodiment. STA 300 includes a processor 302, a memory 310, and a network component 320. The processor 302 generally retrieves and executes programming instructions stored in the memory 310. The processor 302 can be included to represent a single central processing unit (CPU), multiple CPUs, a single CPU with multiple processing cores, a graphics processing unit (GPU) with multiple execution paths, etc.

[0033] The network component 320 includes the components necessary for the STA 300 to interface with the wireless communication network as described above with respect to Figures 1 to 2 the STA 300. For example, the network component 320 can include a WiFi or cellular network interface component and associated software.

[0034] Although the memory 310 is shown as a single entity, the memory 310 may include one or more memory devices having memory blocks associated with physical addresses, e.g., random access memory (RAM), read only memory (ROM), flash memory, or other types of volatile and / or non-volatile memory. The memory 310 generally includes program code for performing various functions related to the use of the STA 300. Although alternative implementations may have different functions and / or combinations of functions, the program code is generally described as various functional "applications" or "modules" within the memory 310.

[0035] Within the memory 310, the locator module 312 includes the FTM module 316. In an embodiment, the FTM module 316 facilitates FTM ranging as described above with respect to Figure 2 FTM is merely one example of a suitable ranging technique, and other techniques may be used. The locator module 312 helps identify the distance of the STA 300 from an AP (e.g., AP 350) and helps identify the location of the STA 300 using the distance information (e.g., in an indoor environment). This will be further discussed with respect to Figure 4 and subsequent figures.

[0036] The AP 350 includes a processor 352, a memory 360, and network components 370. The processor 352 generally retrieves and executes programming instructions stored in the memory 360. The processor 352 is included to represent a single central processing unit (CPU), multiple CPUs, a single CPU having multiple processing cores, a graphics processing unit (GPU) having multiple execution paths, etc.

[0037] The network components 370 include the components necessary for the AP 350 to interface with a wireless communication network as described above with respect to Figures 1 to 2 For example, the network components 370 may include a WiFi or cellular network interface component and associated software.

[0038] Although the memory 360 is shown as a single entity, the memory 360 may include one or more memory devices having memory blocks associated with physical addresses, e.g., random access memory (RAM), read only memory (ROM), flash memory, or other types of volatile and / or non-volatile memory. The memory 360 generally includes program code for performing various functions related to the use of the AP 350. Although alternative implementations may have different functions and / or combinations of functions, the program code is generally described as various functional "applications" or "modules" within the memory 360.

[0039] Within memory 360, the channel quality module 362 uses the angle of arrival module 364 (e.g., using multiple angle of arrival antennas) to identify channel quality information. The FTM module 366 facilitates the use of FTM techniques to allow the STA (e.g., STA 300) to identify its distance from the AP 350. This will be further discussed with respect to Figure 4 and subsequent figures.

[0040] Figure 4 is a flowchart 400 showing ranging between a STA and an AP using FTM and channel quality according to an embodiment. At block 402, the AP (e.g., Figure 3 the AP 350 shown) receives an FTM request (e.g., Figure 3 the FTM request 210 shown) from the STA (e.g., Figure 2 the STA 300 shown). As described above, FTM is merely a suitable technique for ranging between a STA and an AP, and other suitable techniques may be used. As described above, FTM generally works well in a laboratory environment, but in some cases, there may be drawbacks in practice. For example, FTM may be inaccurate or may waste bandwidth in a reflective or obstacle-filled environment. As another example, a non-optimal access point may respond to an FTM message from a STA, resulting in other problems. In an embodiment, channel quality information and other techniques may be used to improve FTM.

[0041] At block 404, the channel quality module (e.g., Figure 3 the channel quality module 362 shown) determines the channel quality of the channel with the STA. In an embodiment, two parameters may be used to characterize the channel quality: stability (i.e., coherence) and delay spread (i.e., power delay profile). In an embodiment, stability measures the coherence of the channel and may be used to determine various FTM parameters, including how often to transmit FTM bursts for accurate ranging from the STA to the AP. In an embodiment, delay spread may be used to determine additional FTM parameters, including how many FTM samples to include in an FTM burst for accurate ranging from the STA to the AP. This will be further discussed below with respect to Figure 5 further.

[0042] At block 406, the FTM module (e.g., Figure 3 the FTM module 366 in the AP 350 shown) determines FTM parameters based on the channel quality information. In an embodiment, the FTM module may determine FTM channel sounding parameters based on the channel quality information. For example, the FTM module may determine the number of FTM bursts, the duration, the FTM frames per burst, and other suitable parameters based on the channel quality information.

[0043] For example, a channel with a relatively high delay spread (e.g., 100 ns) may require a greater number of bursts to achieve a high level of positioning accuracy (e.g., the STA may be NLOS to the AP). In contrast, a channel with a relatively low delay spread (e.g., 5 ns) may require fewer bursts (e.g., the STA may be in LOS to the AP). Similarly, a stationary channel with a relatively high coherence time (Tc) of 200 ms can be characterized by a longer burst period (e.g., 1 / 5 s), while a more unstable channel can be forced to be characterized using a shorter burst period (e.g., 10 ms), while the channel may stabilize. In an embodiment, determining the FTM parameters can be a negotiation between the AP and the STA. For example, the AP can propose initial parameters, and the STA can either agree to these parameters or propose modified parameters.

[0044] At block 408, the FTM module uses the FTM parameters to find the distance from the STA to the AP. For example, the FTM module can use the number of bursts, the duration, the FTM frames per burst, and other parameters to transmit the FTM message in a suitable manner (e.g., as Figure 2 shown) to determine the distance from the STA to the AP. In an embodiment, this greatly improves the use of bandwidth and the number of messages transmitted, while also improving the accuracy of the ranging.

[0045] In an embodiment, the channel quality determination (e.g., as described above with respect to block 404 and below with respect to Figure 5 is occurring in real time with the FTM technique. Additionally, the FTM module can monitor the channel quality over time and modify the FTM parameters throughout the FTM process. In an embodiment, the AP can identify changes in the channel quality over time and can modify the FTM parameters based on the changes. For example, the AP can determine that an obstacle (e.g., a person) has appeared between the STA and the AP. Thus, the AP can modify the FTM parameters to improve the FTM process (e.g., provide shorter bursts with longer wait times between bursts).

[0046] In an embodiment, the FTM module can further track the FTM measurement results over time and discard FTM messages or outliers that appear to be inaccurate. This can be done by the FTM module in the AP (e.g., Figure 3 the FTM module 366 shown) or the FTM module in the STA (e.g., Figure 3completed by the FTM module 316 shown. In an embodiment, this can be done without using channel quality information. Alternatively, channel quality information can be used to identify inaccurate or abnormal messages. For example, if the channel quality reflects an obstacle between the STA and the AP, then a longer propagation time for the FTM message may be accurate. However, if the channel quality reflects a high-quality channel between the STA and the AP (e.g., a clear LOS), then a longer propagation time for the FTM message may be inaccurate.

[0047] Figure 5 is a flowchart for determining channel quality according to an embodiment. In an embodiment, Figure 5 corresponds to Figure 4 the block 404 shown. At block 502, the channel quality module (e.g., Figure 3 the channel quality module 362 in the AP 350 shown) receives channel state information.

[0048] In an embodiment, existing channel quality solutions can be used. For example, many APs use an antenna array on the AP (e.g., 32 antennas) to determine AoA information and estimate channel quality. FTM (and similar technologies) use time-of-arrival (TOA) information (e.g., the rising edge of the PPDU preamble) for ranging. This means that channel quality information (e.g., channel state information (CSI)) from any orthogonal frequency division multiplexing (OFDM) PPDU preamble received by the antenna array can be used for a given 20 MHz channel. In an embodiment, the channel quality information determined by the AoA antenna is used, but not the AoA information itself. The use of the AoA antenna is just an example of a technique for determining channel quality, and other techniques can be used. Additionally, the AoA antenna technique can be used to further refine the channel estimate because it allows many different, time-separated but spatially correlated channel samples. For example, 32 samples can be used (e.g., 8 samples of 4 elements every 4 ms).

[0049] At block 504, the channel quality module determines channel stability. As described above, channel stability is a parameter of channel quality that can be used to determine FTM parameters. In an embodiment, channel stability (i.e., coherence) can be determined based on measuring the phase and / or amplitude of the signal over time. A channel with significant changes in phase and / or amplitude is less coherent than a channel with stable phase and / or amplitude.

[0050] For example, assume that the AP includes 32 antennas for determining AoA information. For example, by averaging samples, each group of 4 overlapping samples can be considered a channel sample. This can be repeated (i.e., sampling 4 antennas in different groups until all 32 antennas are sampled) until the channel coherence time (T C ) can be formed. In an embodiment, this requires a sufficient number of repetitions to cover an appropriate coherence time. The channel quality module can estimate T C for a relatively stable time. This can distinguish a moving STA from a stationary STA, but includes non-motion-related distortions. In addition, FTM transmissions with relatively long intervals can be discarded because such FTM transmissions are less likely to be accurate and only a data burst sequence is selected. This can improve accuracy.

[0051] At block 506, the channel quality module determines the delay spread. The delay spread is another parameter of the channel quality that can be used to determine FTM parameters. In an embodiment, this can be determined by estimating the individual path delays of the channel. For example, long training field (LTF) samples (e.g., 32 LTF samples) can be used with the AoA antennas to identify offset peaks in the subcarriers. This can be used to estimate the individual path delays of the subcarriers and determine the delay spread of the channel.

[0052] Figure 6 is a flowchart 600 showing improved ranging between a STA and an AP in a reflective environment according to one embodiment. At block 602, the channel quality module (e.g., Figure 3 the channel quality module 362 in the AP 350 shown) determines whether the AP and the STA are in a multipath environment. As described above, the CSI profile on the subcarriers of a given STA can indicate whether the wireless propagation environment includes multiple paths (e.g., reflected in multiple peaks and valleys of the CSI in the frequency domain) or is dominated by a direct LOS path (e.g., reflected in a relatively flat CSI profile in the frequency domain). If the wireless propagation environment between the AP and the STA includes multiple paths, then the process proceeds to block 604. If the wireless propagation environment between the AP and the STA does not include multiple paths, then the process ends.

[0053] At block 604, the channel quality module estimates the reflection pattern. In an embodiment, the channel quality module can use the randomness of the signal to estimate the degree of multipath delay spread between the AP and the STA and improve the distance estimate from FTM (e.g., by modifying the timestamp value of the reflected multipath delay spread included in the FTM messaging process). This can improve ranging using FTM because when the AP estimates multiple paths, the STA may overestimate the distance to the AP by using FTM because the signal will take longer to travel between the STA and the AP due to reflections.

[0054] At block 606, the FTM module (e.g., Figure 3 The FTM module 366 in the AP 350 shown in the figure uses the reflection mode to determine the distance between the STA and the AP. For example, the FTM module 366 can instruct the STA (e.g., Figure 3 The locator module 312 in the STA 300 shown in FIG. 1 applies one or more coefficients to the timestamp value (eg, Figure 2 The timestamp shown) is used to improve the accuracy of distance estimation in a reflective environment. That is, the locator module can apply a coefficient to modify the timestamp value so that the FTM calculation takes into account the reflection path and improves the accuracy of the distance estimation.

[0055] Figure 7A 700 among multiple APs 702A-C in an environment 700 according to one embodiment. In an embodiment, the STA 704 determines its position relative to the APs 702A-C. In addition, in an embodiment, the environment 700 is reflective, creating multiple transmission paths between the STA 704 and the APs 702A-C. Assume that the STA 704 and the APs 702A-C do not implement Figure 6 With the improved FTM technique shown, the position estimate can only determine that STA 704 is within area 710. This is because environment 700 is reflective, and therefore the FTM technique between STA 704 and APs 702A-C is not very accurate.

[0056] Figure 7B 7 shows a position estimation of a wireless STA 714 between multiple APs 712A-C in an environment 750 according to one embodiment. In an embodiment, the STA 714 determines its position relative to the APs 712A-C. In addition, in an embodiment, the environment 750 is also reflective, creating multiple transmission paths between the STA 714 and the APs 712A-C. However, the STA 714 and the APs 712A-C are not necessarily aligned with each other. Figure 6 The reflective environment shown implements the improved FTM technique. Therefore, the location of STA 714 can be narrowed down to area 720 (less than Figure 7A This is because Figure 6 The improved FTM technique shown makes the FTM technique between the STA 714 and the APs 712A-C more accurate in the reflective environment 750.

[0057] In the present disclosure, various embodiments are referenced. However, the scope of the present disclosure is not limited to the specifically described embodiments. Instead, any combination of the described features and elements, whether or not related to different embodiments, is contemplated for implementing and practicing the contemplated embodiments. Additionally, when an element of an embodiment is described in the form of "at least one of A and B", it should be understood that embodiments including only element A, only element B, and including both element A and element B are all contemplated. Furthermore, although some embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether a given embodiment achieves a particular advantage does not limit the scope of the present disclosure. Accordingly, the various aspects, features, embodiments, and advantages disclosed herein are illustrative only and are not to be considered elements or limitations of the appended claims unless expressly recited in one or more of the claims. Similarly, references to "the invention" should not be construed as a generalization of any inventive subject matter disclosed herein and should not be considered an element or limitation of the appended claims unless expressly recited in one or more of the claims.

[0058] As will be recognized by those skilled in the art, the embodiments disclosed in the present disclosure may be embodied as a system, method, or computer program product. Accordingly, the various embodiments may be in the form of a full hardware embodiment, a full software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, which are generally referred to herein as "circuits," "modules," or "systems." Additionally, the embodiments may be in the form of a computer program product embodied in one or more computer-readable media having computer-readable program code embodied thereon / to be executed by one or more processors to perform any method described herein.

[0059] The program code embodied on the computer-readable media may be transmitted using any appropriate medium, including but not limited to wireless, wired, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0060] Computer program code for performing the operations of the various embodiments of the present disclosure may be written in any combination of one or more programming languages, including object-oriented programming languages (such as Java, Smalltalk, C++, etc.) and conventional procedural programming languages (such as the "C" programming language or similar programming languages). The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network (including a local area network (LAN) or a wide area network (WAN)), or the remote computer may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0061] Aspects of the present disclosure are described with reference to the flowchart illustrations and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments presented in the present disclosure. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for implementing the functions / acts specified in the (one or more) block(s) of the flowchart illustration and / or block diagram.

[0062] These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other devices to operate in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means that implement the functions / acts specified in the (one or more) block(s) of the flowchart illustration and / or block diagram.

[0063] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer-implemented process, such that the instructions executed on the computer, other programmable data processing apparatus, or other devices provide a process for implementing the functions / acts specified in the (one or more) block(s) of the flowchart illustration and / or block diagram.

[0064] The flowchart illustrations and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of the possible implementations of systems, methods, and computer program products according to various embodiments. In this regard, each block in the flowchart illustration or block diagram may represent a module, segment, or portion of code that contains one or more executable instructions for implementing a particular logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by a special purpose hardware-based system that performs a particular function or act, or by combinations of special purpose hardware and computer instructions.

[0065] In view of the foregoing, the scope of the present disclosure is determined by the appended claims.

Claims

1. A method for wireless communication, comprising: Determining channel state information at a wireless access point (AP) corresponding to a wireless station (STA), wherein determining the channel state information includes: Using multiple angle-of-arrival (AoA) antennas at the AP to determine at least one of the following: (i) a channel stability measurement corresponding to the AP and the STA and (ii) a delay spread measurement corresponding to the AP and the STA; Determining, at the AP, one or more fine timing measurement (FTM) parameters based on the channel state information including at least one of the stability measurement result and the delay spread measurement result; and Transmitting a plurality of FTM messages between the AP and the STA based on the one or more FTM parameters, wherein the STA is configured to determine an estimated distance to the AP based on the plurality of FTM messages.

2. The method according to claim 1, wherein, Determining the channel state information includes: Using the multiple AoA antennas to determine the channel stability measurement corresponding to the AP and the STA; and Using the multiple AoA antennas to determine the delay spread measurement corresponding to the AP and the STA.

3. The method according to claim 2, wherein, Determining the one or more FTM parameters at the AP based on the channel state information includes: Determining a burst period of the plurality of FTM messages based on the channel stability measurement result; and Determining a burst size of the plurality of FTM messages based on the delay spread measurement result, wherein transmitting the plurality of FTM messages between the AP and the STA is based on the burst period and the burst size.

4. The method according to any one of claims 1-3, further comprising: After transmitting a first FTM message of the plurality of FTM messages, determining, at the AP, modified channel state information corresponding to the STA; And Determining, at the AP, a second one or more FTM parameters based on the modified channel state information, wherein transmission of at least one FTM message of the plurality of FTM messages is based on the second one or more FTM parameters.

5. The method according to any one of claims 1-3, further comprising: Determining that the transmission between the AP and the STA includes multiple paths, wherein the STA is configured to determine an estimated distance to the AP based on the determined multiple paths.

6. The method according to claim 5, wherein Determining the estimated distance to the AP based on the determined multiple paths includes: Estimating a reflection pattern between the AP and the STA; Identifying a plurality of timestamps associated with transmitting the plurality of FTM messages between the AP and the STA; Calculating one or more coefficients associated with the plurality of timestamps based on the reflection pattern; and Determining the estimated distance to the AP based on the plurality of timestamps and the one or more coefficients.

7. The method according to any one of claims 1-3, further comprising: Receiving a first FTM message; And Discarding the first FTM message based on the determined channel state information.

8. The method according to claim 7, wherein, Determining that the estimated distance is not based on the discarded first FTM message.

9. A wireless access point (AP) includes: A processor; And A memory storing a program that, when executed on the processor, performs operations including: Determining channel state information corresponding to a wireless station (STA), where determining the channel state information includes: At the AP, using multiple angle of arrival (AoA) antennas to determine at least one of the following: (i) a channel stability measurement result corresponding to the AP and the STA and (ii) a delay spread measurement result corresponding to the AP and the STA; Determining one or more fine timing measurement (FTM) parameters based on the channel state information including at least one of the stability measurement result and the delay spread measurement result; and Transmitting multiple FTM messages between the AP and the STA based on the one or more FTM parameters, where the STA is configured to determine an estimated distance to the AP based on the multiple FTM messages.

10. The wireless AP according to claim 9, wherein, Determining the channel state information includes: Using the multiple AoA antennas to determine the channel stability measurement result corresponding to the AP and the STA; and Using the multiple AoA antennas to determine the delay spread measurement result corresponding to the AP and the STA.

11. The wireless AP according to claim 10, wherein, Determining the one or more FTM parameters based on the channel state information includes: Determining a burst period of the multiple FTM messages based on the channel stability measurement result; and Determining a burst size of the multiple FTM messages based on the delay spread measurement result, where transmitting the multiple FTM messages between the AP and the STA is based on the burst period and the burst size.

12. The wireless AP according to any one of claims 9 to 11, the operations further include: Receiving a first FTM message; And Discarding the first FTM message based on the determined channel state information, where determining the estimated distance is not based on the discarded first FTM message.

13. The wireless AP according to any one of claims 9 to 11, the operations further include: Determining that a transmission between the AP and the STA includes multiple paths, where the STA is configured to determine an estimated distance to the AP based on the determined multiple paths.

14. The wireless AP according to claim 13, wherein, Determining the estimated distance to the AP based on the determined multiple paths includes: Estimating a reflection pattern between the AP and the STA; Identifying multiple timestamps associated with transmitting the multiple FTM messages between the AP and the STA; Calculating one or more coefficients associated with the multiple timestamps based on the reflection pattern; and Determining the estimated distance to the AP based on the multiple timestamps and the one or more coefficients.

15. A wireless station (STA) includes: A processor; And A memory storing a program that, when executed on the processor, performs operations including: Receive one or more fine timing measurement (FTM) parameters from a wireless access point (AP), where the AP is configured to determine the one or more FTM parameters based on channel state information corresponding to the STA, and where the AP is configured to determine the channel state information based on at least one of the following determined using multiple angle of arrival (AoA) antennas at the AP: (i) a channel stability measurement result corresponding to the AP and the STA and (ii) a delay spread measurement result corresponding to the AP and the STA; Transmit a plurality of FTM messages between the STA and the AP based on the one or more FTM parameters; and Determine an estimated distance to the AP based on the plurality of FTM messages.

16. The wireless STA according to claim 15, wherein, The AP is configured to determine the channel state information based on the following: Determine the channel stability measurement result corresponding to the AP and the STA using the multiple AoA antennas; Determine the delay spread measurement result corresponding to the AP and the STA using the multiple AoA antennas, and where the AP is configured to determine the one or more FTM parameters based on the following: Determine the burst period of the plurality of FTM messages based on the channel stability measurement result; and Determine the burst size of the plurality of FTM messages based on the delay spread measurement result, where the transmission of the plurality of FTM messages between the AP and the STA is based on the burst period and the burst size.

17. The wireless STA according to claim 15 or 16, further comprising: Determine that the transmission between the AP and the STA includes multiple paths; and Determine an estimated distance to the AP based on the determined multiple paths.

18. A computer-readable storage device carrying computer-readable program code for causing one or more processors to execute the method according to any one of claims 1 to 8.

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