CLASSIFICATION OF AN APS PAIR AS A LINE-OF-SIGHT PAIR OR A NON-LINE-OF-SIGHT PAIR

Abstract

An example procedure and a network device are presented. The example network device configures a first access point (AP) and a second AP to communicate over a first frequency and receives a first set of Fine Timing Measurement (FTM) metrics between the first AP and the second AP over the first frequency from one or both, or the first AP or the second AP. Furthermore, the network device reconfigures the first AP and the second AP to communicate over a second frequency and receives a second set of FTM metrics between the first AP and the second AP over the second frequency from one or both, or the first AP or the second AP. Finally, based on the first set of FTM metrics and the second set of FTM metrics, the network device determines whether the first AP and the second AP are in line of sight (LoS).

Description

BACKGROUND

[0001] A networked infrastructure implementing a wireless local area network (WLAN) typically includes access points located at various points within a facility to provide wireless connectivity for client devices. Client devices, such as laptops, PCs, and smartphones, can connect to an access point (AP) on the WLAN to exchange data. With advancements in wireless fidelity (Wi-Fi) technology, the latest APs are designed to self-locate within the networked infrastructure. Specifically, these self-locating APs can determine the relative positions of other APs in the vicinity. Knowing the location of APs within the network infrastructure helps client devices connect to the correct APs.Furthermore, such location knowledge helps network administrators and service providers to efficiently locate, update and / or maintain wireless-enabled devices such as access points and client devices in the WLAN. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] One or more examples in the present disclosure are described in detail with reference to the following illustrations. The illustrations serve only for clarification and merely represent examples. Fig. This shows an example of a networked system in which various examples presented here can be implemented. Fig. shows a block diagram of an example network device that is able to classify an AP pair as a line-of-sight (LoS) pair or as a non-line-of-sight (NLoS) pair. Fig.shows a flowchart of an example procedure for classifying an AP pair as a LoS pair or NLoS pair. Fig. shows a flowchart of another example procedure for classifying an AP pair as a LoS pair or NLoS pair. Fig. shows a block diagram of an example access point that is capable of timestamping a direct wireless path signal. Fig. shows a flowchart of an example procedure for timestamping a direct wireless path signal. Fig. shows a graphical representation of the signal strength values ​​recorded by an AP. Fig. shows a flowchart of another example of a method for timestamping a direct wireless path signal. Fig. shows a flowchart of an example procedure for adjusting a timestamp parameter, e.g., a threshold value. Fig.shows a flowchart of an example procedure for adjusting a timestamp parameter, such as a search window. Fig. shows an example of a computer system.

[0003] The illustrations are not exhaustive and do not limit the present disclosure to the exact form that is revealed. DETAILED DESCRIPTION

[0004] Distance measurement techniques such as the Fine Timing Measurement (FTM) protocol, supported by the IEEE 802.11mc specification, are increasingly used to enable access points (APs) to determine their relative positions. Distance measurement using the FTM protocol involves exchanging messages between an initiator (e.g., an AP initiating an FTM session) and a responder (e.g., an AP responding to the initiator during the FTM session) to determine the distance between the initiator and one or more responders. Based on the messages exchanged between the initiator and one or more responders, the initiator can determine its position relative to the responders. In some implementations, the distances measured using FTM can be used to automatically generate a location map of these APs within the networked infrastructure.

[0005] It is evident that an accurate estimation of the distance between two wireless devices, such as access points (APs), is useful for applications like determining the precise indoor positioning of APs within a networked infrastructure. This distance estimation is primarily achieved by estimating the time a wireless signal takes to travel from one wireless device to another. Accurate timestamping of the wireless signal plays a crucial role in this process of estimating the signal's propagation time.

[0006] Typically, wireless network devices like access points (APs) are ceiling-mounted in large indoor spaces and generally point downwards. Furthermore, various physical obstacles such as walls, pillars, and doors may be present, preventing a clear line-of-sight (i.e., unobstructed) positioning of the APs. In such network implementations, a signal from a first access point to a second access point that is not in the line of sight of the first may take multiple paths before reaching the second access point. In particular, such AP positioning can negatively impact the performance of applications that use distance measurements for location determination with field-to-mover (FTM) to estimate pairwise distances between APs and automatically create a map of these APs.Especially access points (APs) primarily mounted on the ceiling, with their antennas pointing downwards towards their customers, have little chance of establishing direct wireless path signals between them. In such a network configuration, a strong initial reception of a signal transmitted by the first AP at the second AP may not always occur via a direct path. The term "direct path" as used here can refer to a straight path between the two APs. The direct path can be the shortest path between the two APs. A wireless signal traveling along the direct path is referred to as a direct wireless path signal.

[0007] Conventional methods generally determine the initial strong signal reception to estimate the distance between the first and second access points (APs). Since this initial strong reception is not always the reception via the direct path between the two APs, the distance estimated using conventional methods can be inaccurate. Furthermore, the presence of physical obstacles between the APs can complicate the timing task, as one of the multipath signals may follow the shortest direct path, while the other signals may have taken longer, non-direct paths, potentially leading to an overestimation of the actual distance.

[0008] To address the challenges mentioned above, methods and systems are presented, in examples consistent with the teachings of this revelation, that enable more accurate timestamping of the signals and thus more accurate positioning of the APs. Specifically, the proposed solution includes (A) a classification technique comprising a method and system for classifying a pair of APs as a line-of-sight (LoS) pair or a non-line-of-sight (NLoS) pair, and (B) a timestamping technique comprising a method and system for accurately timestamping the signals received by the APs. In some examples, the method and system for accurately timestamping the signals can utilize the classification of the AP pair to further improve the accuracy of the timestamping. Furthermore, a technique for dynamically tuning the timestamping parameters used in the timestamping technique is presented.

[0009] As mentioned previously, achieving line-of-sight (LoS) coverage within buildings is not always possible, especially over large areas. Therefore, to more accurately determine the arrival time of a direct wireless signal, it is advantageous to first ascertain whether the two communicating access points (APs) are within line of sight or out of line. Determining line of sight is typically difficult because the connections between APs are static. Consequently, conventional solutions that rely on fluctuations in received signal strength and distance measurements to determine line of sight are not applicable.Instead, the proposed classification technique in some examples involves the use of channel diversity to more accurately determine whether the access points are line-of-sight or out of line of sight. Since signal measurements vary considerably when switching from one channel to another, signal propagation on out-of-line paths also varies because the phase and reflection coefficients fluctuate, resulting in different superpositions of the multipath reception of the signal at the receiving access point.

[0010] In particular, the proposed method for determining whether a first and second access point (AP) are within line of sight involves first configuring the first and second APs with a network device to communicate over a first frequency (e.g., a first Wi-Fi channel). The network device can be any network device, such as a WLAN controller or a remote computer system, connected to and configured to communicate with the first and second APs. The network device can then configure the first and second APs to perform a Field Transmittance (FTM) sequence and collect an initial set of FTM metrics, such as FTM distance and signal strength. Signal strength can be representative of the power (generally expressed in milliwatts or decibel-milliwatts) of the wireless signal received by a particular AP, such as the first or second AP.In some examples, the received signal strength can be expressed as an RSSI (Received Signal Strength Indicator) value between the first and second access points (APs). The FTM distance is the distance between the first and second APs, estimated using the techniques proposed in the FTM protocol. The network device can receive the first set of FTM metrics from one or both APs, either the first or the second.

[0011] Furthermore, the network device can reconfigure the first and second access points (APs) to communicate over a second frequency (e.g., a second Wi-Fi channel) that differs from the first, execute another FTM sequence, and collect a second set of FTM metrics. The network device can then determine whether the first and second APs are within line of sight based on both sets of FTM metrics. Specifically, changes in FTM metrics across different frequencies can be affected by potential obstacles in the signal. The network device uses the magnitude of these changes to determine whether the first and second APs are within line of sight.

[0012] In some examples, the proposed timestamping technique also relies on the fact that the signal via a direct path precedes all other paths and is not necessarily the strongest. In other words, in an AP-to-AP distance setting, the signal component corresponding to the direct path (line-of-sight path) may be significantly attenuated compared to non-line-sight reflections. Therefore, instead of marking the timestamp of the strongest received signal as the time of arrival on the direct path, the proposed timestamping technique involves identifying all peaks within a window of a certain size preceding the highest peak. Then, the rising edge of the first (earliest) peak value to exceed a certain threshold within this window is determined.The timestamp of such a rising slope can be marked as the timestamp for the arrival time of the direct path.

[0013] In one example implementation, a first access point (AP) can receive a multitude of signals (e.g., multipath propagating signals) from a second AP and record the signal strength and arrival times of these signals. The first AP can then identify peak signal strength values ​​within a search window preceding the highest signal strength value from the recorded values ​​and select a timestamp on the rising edge of the earliest peak, which exceeds a threshold, as the arrival time of a direct wireless path signal.

[0014] In some examples, the threshold used in timestamping techniques can be derived from the highest percentiles of the number of values ​​that comprise the channel impulse response with its multitude of signals. The threshold can be determined, for example, based on the signal strength values ​​in the search window. Specifically, the first AP can sort the signal strength values ​​in the search window in ascending order and then select a signal strength from the sorted values ​​at a predefined percentile of the total number of signal strength values. For example, if a channel impulse response contains one hundred (100) signal strength values, the first AP can sort these signal strength values ​​in ascending order and mark the threshold that corresponds approximately to the fifth-highest value among these 100 values, i.e., the 95th.

[0015] In some examples, classifying an AP pair—including the first AP and the second AP—as a line-of-sight (LoS) or non-line-of-sight (NLoS) pair helps in adjusting the timestamp described above. Specifically, after determining the AP pair's classification, the first AP can adjust the search window and / or threshold based on the AP pair classification to improve timestamp accuracy. The AP pair classification indicates whether the first AP and the second AP are in line of sight or out of line of sight to each other. For example, the search window can be widened if the first AP and the second AP are out of line of sight (i.e., the AP pair is an NLoS pair), or the search window can be narrowed if the first AP and the second AP are in line of sight to each other (i.e., the AP pair is an LoS pair).Furthermore, in some examples, the threshold can be lowered if the AP pair is identified as an NLoS pair. Conversely, the threshold can be raised if the AP pair is identified as a LoS pair.

[0016] For the NLoS-AP pair, the direct signal path can be extremely attenuated or completely blocked, resulting in the actual timestamp being well before the maximum peak. As can be seen, increasing the search window and / or decreasing the threshold percentile would help classify an earlier peak as the direct wireless path signal, thus increasing the chances of correctly identifying the signal as the direct wireless path signal. Conversely, decreasing the search window and / or increasing the threshold percentile for the LoS-AP pair would result in a later peak being used as the timestamp, thus avoiding some noise and underestimating the range measurement.Therefore, the proposed technique improves the accuracy of timestamping for both LoS and NLoS-AP pairs by adaptively adjusting the search window and / or threshold.

[0017] The following detailed description refers to the accompanying drawings. It is expressly stated that the drawings serve only for illustration and description. Although several examples are described in this document, modifications, adaptations, and other implementations are possible. Accordingly, the following detailed description does not limit the disclosed examples. Instead, the proper scope of the disclosed examples can be defined by the accompanying claims.

[0018] Before describing examples of the disclosed systems and methods in detail, it is useful to describe an example of a network installation in which these systems and methods could be implemented in various applications.

[0019] Fig.This shows an example of a networked System 100, in which various examples presented here can be implemented. System 100 can be a small network of devices or a large network of devices. The small network of devices could be, for example, a home network. The large network of devices could be an organization, a university, a public facility (e.g., a shopping mall, an airport, a train station, a bus station, a stadium, etc.), or an office network with a large number of networked devices. In some examples, the networked System 100 can be implemented in any type of setting, such as a home or an organization like a business, an educational institution, a government agency, a healthcare facility, or any other type of organization.

[0020] The networked system 100 can be a network infrastructure comprising multiple wireless and wired devices that communicate with each other and / or with an external device or system. In the example implementation of Fig. For illustrative purposes, it is shown that the networked system 100 comprises three devices, e.g., one network device 102 and two access points (APs) 104 and 106. It should be noted that the examples presented here do not account for the specific features (e.g., types and number) of the devices in Fig.The devices shown are limited. In one example implementation, network device 102 can be part of a wireless local area network (WLAN) set up via APs 104 and 106. In certain other examples, network device 102 can be located outside the WLAN set up via APs 104 and 106. For example, network device 102 can be deployed in a cloud infrastructure and communicate with APs 104 and 106.

[0021] In some examples, network device 102 can be a network controller, such as a WLAN controller, that can configure and manage APs 104, 106, and / or other devices like switches, routers, other APs, and / or client devices, if present in system 100. In some examples, network device 102 itself can be an AP or provide AP functionality. In other implementations, network device 102 can provide router functionality for APs 104 and 106. Furthermore, in some implementations, network device 102 can be a computer system hosted in a cloud infrastructure remote from APs 104 and 106.

[0022] A wireless network device, such as one of the APs 104 or 106, can be a combination of hardware, software, and / or firmware configured to provide wireless network connectivity for client devices (not shown). In some examples, the APs 104 or 106 may be implemented with one or more radios to assist them in communicating with the respective client devices and other wireless-enabled devices. Each radio can operate within a specific range of radio frequencies known as a Wi-Fi band, such as the 2.4 GHz Wi-Fi band, the 5 GHz Wi-Fi band, the 6 GHz Wi-Fi band, and so on.

[0023] Client devices can connect to APs 104 and 106 to communicate with each other and / or with other devices directly or indirectly connected to APs 104 and 106. Specifically, APs 104 and 106 can provide network connectivity for the respective client devices, allowing them to access the WLAN and / or the internet via APs 104 and 106. In some examples, APs 104 and 106, the client devices, and network device 102 can be configured to communicate using wireless communication techniques specified in one or more IEEE 802.11 (Institute of Electrical and Electronics Engineers) standard specifications.Examples of client devices that can connect to APs 104 and 106 include desktop computers, laptops, servers, web servers, authentication servers, Authentication Authorisation Accounting (AAA) servers, Domain Name System (DNS) servers, Dynamic Host Configuration Protocol (DHCP) servers, Internet Protocol (IP) servers, Virtual Private Network (VPN) servers, network policy servers, mainframes, tablet computers, e-readers, netbook computers, televisions and similar displays (e.g., smart TVs), content receivers, set-top boxes, personal digital assistants (PDAs), mobile phones, smartphones, virtual terminals, video game consoles, virtual assistants, Internet of Things (IoT) devices, and the like.

[0024] The access points (APs) 104 and 106 can communicate with the network device 102 via their respective connections 108A and 108B. Connections 108A and 108B can be wired and / or wireless interfaces. For example, connections 108A and 108B can be wired or wireless connections over a public or private network, such as the internet, or another communications network, to enable connectivity between APs 104 and 106 and the network device 102. Connections 108A and 108B can include telecommunications lines, such as telephone lines, broadcast coaxial cables, fiber optic cables, satellite communications, cellular communications, and the like. In some examples, connections 108A and 108B can include any number of intermediate network devices, such as switches, routers, gateways, servers, and / or controllers.

[0025] It is obvious that indoors, especially in large areas, it is not always possible to place specific pairs of access points (APs) in a line of sight to each other. As previously noted, such AP positioning can negatively impact the performance of applications that use distance measurements for location tracking with FTM to estimate the pairwise distances between APs and automatically create a map of these APs. In particular, APs primarily mounted on ceilings, with their antennas designed to communicate downwards towards their customers, have little chance of having direct wireless path signals between them. This can ultimately lead to the misidentification of a direct wireless path signal and compromise the accurate timing of the direct wireless path signal.

[0026] In some examples consistent with the teachings of the present disclosure, the network device 102 can assist the APs 104 and 106 in more accurately identifying and timestamping the direct wireless path signals between two APs, leading to more accurate positioning of the APs. Specifically, the network device 102 can be configured to classify an AP pair formed by APs 104 and 106 as a line-of-sight (LoS) pair (i.e., APs 104 and 106 are in line of sight to each other) or as a non-line-of-sight (NLoS) pair (i.e., APs 104 and 106 are not in line of sight to each other) by applying the instructions 110 stored in the network device 102 (in Fig.as “LoS-NLoS classification instructions”). In particular, the proposed classification technique implemented by Network Device 102 utilizes channel diversity to more accurately determine whether the APs are line-of-sight or out of line of sight. Signal measurements can vary considerably when measurements are taken over multiple channels. Specifically, signal propagation on out-of-line paths generally varies because the phase and reflection coefficients fluctuate, resulting in different superpositions of the multipath reception of the signal at the receiving AP. Network Device 102 uses these characteristics of multi-channel signal propagation to determine whether the APs are line-of-sight or out of line of sight. Further details on how Network Device 102 determines AP pair classification are provided in conjunction with the Fig. described in the section “AP pair classification”.

[0027] Furthermore, in some examples, APs 104 and 106 can implement a technique for identifying a direct wireless path signal between APs 104 and 106 and for timestamping the arrival of such a direct wireless path signal. In some examples, APs 104 and 106 can each execute timestamping instructions 112 and 114, respectively, to timestamp the arrival of the direct wireless path signal. The proposed timestamping technique, implemented by one of APs 104 or 106, is based on the fact that the signal via a direct path precedes all other paths and is not necessarily the strongest. In other words, in an AP-to-AP distance setting, the signal component corresponding to the direct path (line-of-sight path) can be significantly weaker compared to non-line-sight reflections.Instead of marking the timestamp of the strongest received signal as the time of arrival on the direct path, a receiving AP of AP 104, 106 therefore identifies all peaks within a window of a certain size that precedes the highest peak.

[0028] Furthermore, the receiving AP identifies a rising edge of the first (earliest) peak that exceeds a threshold within this search window and timestamps the time of such a rising edge as the arrival time of the direct path. In some examples, the receiving AP of APs 104 and 106 can derive the threshold used in the timestamping technique mentioned above based on the highest percentiles of the values ​​that comprise the channel impulse response, which includes the majority of the signals. The threshold can be determined, for example, based on the signal strength values ​​in the search window. Specifically, the first AP can sort the signal strength values ​​in ascending order and then select a signal strength at a predefined percentile of the total number of signal strength values ​​from the sorted signal strength values.Additional details about how the network device 102 identifies and timestamps the direct wireless path signal are provided in conjunction with the . Fig. described in a section entitled “TIMESTAMPING OF THE DIRECT WIRELESS PATH SIGNAL”.

[0029] In some examples, classifying an AP pair consisting of APs 104 and 106 as a LoS pair or NLoS pair helps in adjusting the timestamp described above. Specifically, after determining an AP pair classification, the first AP can adjust the search window and / or threshold based on the AP pair classification to improve timestamp accuracy. For example, the search window can be increased if APs 104 and 106 form an NLoS pair, or the search window can be decreased if APs 104 and 106 form a LoS pair. As can be seen, increasing the search window and / or decreasing the threshold percentile would help classify an earlier peak as the direct wireless path signal, thereby increasing the chances of correctly identifying the signal as the direct wireless path signal.On the other hand, reducing the search window and / or increasing the threshold percentile for the LoS-AP pair would result in a later peak being used as the timestamp, thus avoiding some noise and an underestimation of the range measurement. Therefore, the proposed technique improves the accuracy of the timestamp for both LoS and NLoS-AP pairs by adaptively adjusting the search window and / or the threshold. Furthermore, in some examples, the threshold can be reduced when APs 104 and 106 form an NLoS pair. Conversely, the threshold can be increased when APs 104 and 106 form the LoS pair. Details on how network device 102 identifies and timestamps the direct wireless path signal are provided in conjunction with the [reference to be added]. Fig. described in the section “COUNTING THE TIMESTAMPING PARAMETERS”.

[0030] For easier illustration, clarity, and better organization of the information, the following description is divided into three sections, labeled "AP Pair Classification," "Timestamping of the Direct Radio Link Signal," and "Coordination of the Timestamp Parameters." This division of the description into the aforementioned sections is in no way intended as a limitation. AP-PAAR CLASSIFICATION

[0031] This section describes in detail how a network device, such as network device 102, classifies an AP pair consisting of APs 104 and 106 as a LoS pair or NLoS pair. Exemplary details are provided using the Fig. described.

[0032] Fig. This shows a block diagram of an example Network Device 200. The Network Device 200 from Fig. Can an example be network device 102 from Fig.In certain examples, network device 200 can be implemented as a controller, such as a WLAN controller. Alternatively, in some implementations, network device 102 can be a computer system in a cloud infrastructure. Specifically, network device 200 can be configured to determine an AP pair classification for each AP pair in a networked system, such as networked system 100. Fig. .

[0033] The network device 200 can contain a processing resource 202 and / or a machine-readable storage medium 204 so that the network device 200 can perform several operations, which are described in more detail below. In particular, the network device 200 implements a classification machine 206 to determine the AP pair classifications. For illustration, the classification machine 206 and the elements within the classification machine 206 are represented by the dashed outline, as they represent digital units that can be in the form of data and / or instructions that can be executed by a physical processing resource, such as the processing resource 202.

[0034] The processing resource 202 can be a physical device, such as a central processing unit (CPU), a microprocessor, a graphics processing unit (GPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), other hardware devices capable of retrieving and executing instructions stored in the machine-readable storage medium 204, or combinations thereof. In one example, the processing resource 202 can retrieve, decode, and execute the instructions stored in the machine-readable storage medium 204 to determine the AP pair classifications. Alternatively or in addition to executing the instructions, the processing resource 202 can include at least one integrated circuit (IC), control logic, electronic circuits, or combinations thereof comprising multiple electronic components for performing the functions to be executed by the network device 200.

[0035] The machine-readable storage medium 204 can be non-transient and is alternatively referred to as a non-transient machine-readable storage medium that does not include any transient transmission signals. The machine-readable storage medium 204 can be any electronic, magnetic, optical, or other storage device capable of storing data and / or executable instructions. Examples of the machine-readable storage medium 204 include RAM, NVRAM, EEPROM, a storage drive (e.g., SSD or HDD), flash memory, and the like. The machine-readable storage medium 204 can be encoded with the classification engine 206, which assists in determining the AP pair classifications. The classification engine 206 contains program data 208 and program instructions 210, which the processing resource 202 uses to determine the AP pair classifications.The program instructions 210 can be an example of the LoS-NLoS classification instructions 110 from . Fig. be.

[0036] The program data 208 can store a variety of data that can be received, used, and / or generated by the processing resource 202 when the processing resource 202 executes the program instructions 210. For example, the processing resource 202 can store data such as FTM metrics received from the APs. Furthermore, the processing resource 202 can store an AP classification database containing information about the AP pair classification for one or more AP pairs in the networked system 100.

[0037] In accordance with examples consistent with the present disclosure, the network device 200 can execute the classification engine 206 by means of the processing resource 202, which executes the program instructions 210, to determine a classification of an AP pair, e.g., an AP pair consisting of APs 104 and 106 of Fig. is formed. In particular, the processing resource 202 can, in some examples, execute one or more of the program instructions 210 to process the data associated with the Fig. The program instructions 210 can, for example, contain instructions 212, 214, 216, 218, and 220. In particular, instructions 212, when executed by the processing resource 202, can cause the processing resource 202 to execute an initial AP (e.g., AP 104 of Fig. ) and a second AP (e.g., AP 106 from Fig.) to configure them to communicate over a first frequency. Furthermore, instructions 214, when executed by processing resource 202, can cause processing resource 202 to receive a first set of FTM metrics between the first AP and the second AP over the first frequency from one or both, the first AP or the second AP.

[0038] Furthermore, instructions 216, when executed by processing resource 202, can cause processing resource 202 to reconfigure the first AP and the second AP to communicate over a second frequency different from the first. Additionally, instructions 218, when executed by processing resource 202, can cause processing resource 202 to receive a second set of FTM metrics between the first AP and the second AP over the second frequency from one or both of the first AP or the second AP. Furthermore, instructions 220, when executed by processing resource 202, can cause processing resource 202 to determine, based on the first set of FTM metrics and the second set of FTM metrics, whether the first AP and the second AP are in line of sight (LoS).

[0039] Although not shown, in some examples the machine-readable storage medium 204 may be encoded with certain additional executable instructions to perform other operations carried out by the network device 200, without limiting the scope of the present disclosure.

[0040] In Fig. A flowchart of an example procedure 300 for classifying an AP pair is presented. The in Fig. The steps shown can be performed from any suitable device, e.g., a network device (e.g., network device 102 from Fig. or the network device 200 of Fig.In some examples, the appropriate device may include a processing resource capable of retrieving and executing instructions stored in a machine-readable storage medium. The processing resource and machine-readable storage medium may be exemplary representatives of the processing resource 202 and the machine-readable storage medium 204 of the network device 200. Alternatively, or in addition to retrieving and executing instructions, the processing resource may include one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits. For illustration, the following refer to Fig. The described examples relate to the classification of an AP pair, which includes a first AP (e.g., AP 104 of Fig. ) and a second AP (e.g., AP 106 from Fig. ) includes.

[0041] In step 302, the network device can configure a first AP and a second AP to communicate over a first frequency. Specifically, the network device can send the same channel settings to both the first and second APs, so that the first and second APs establish a first Wi-Fi channel as their operating channel. The channel setting can include information about the first Wi-Fi channel, such as a channel identifier, a number, and / or a frequency range. The first Wi-Fi channel can be one of the Wi-Fi channels specified in the existing IEEE 802.11 standards or a new channel that can be introduced. In some examples, the network device can also instruct the first and second APs to begin a first FTM sequence.

[0042] Furthermore, in step 304, the network device can receive an initial set of FTM metrics between the first and second APs over the first frequency from either or both APs. The APs can generate the FTM metrics by performing ranging during the initial FTM sequence, according to the FTM protocol specified in IEEE 802.11mc. Either the first or second AP can initiate the FTM by sending a ranging request to the other AP. The wireless device initiating a ranging request is referred to as the initiator, and the wireless device receiving the ranging request is referred to as the responder. The initial FTM sequence, according to the FTM protocol described in the IEEE 802.11mc specification, involves exchanging messages between the initiator and the responder to determine the distance between them.Based on the messages exchanged between the initiator and the responder, the initiator can determine its position relative to the responder. In the given example, either the first or the second AP can act as the initiator and the other as the responder. Specifically, in the examples presented here, the AP acting as the initiator is responsible for determining the FTM metrics, such as the FTM distance and signal strength value between the first and second APs. It should be noted that the present invention is not limited to the technique of determining the FTM metrics. In some examples, the APs can implement standard techniques and / or protocols, such as those described in the IEEE 802.11mc specification, to calculate the FTM distances and signal strength. The network device can record the first set of FTM metrics in program data, for example, in program data 208 (see [reference]). Fig. ).

[0043] Once the first FTM sequence is complete and the first set of FTM metrics has been reported, the networking device can reconfigure the first and second access points (APs) in step 306 to communicate over a second frequency. Specifically, this second frequency differs from the first. Similar to what was described in conjunction with step 302, the networking device can send another common channel setting to the first and second APs to reconfigure them in step 306. This new channel setting can specify details about a second Wi-Fi channel, such as a channel identifier, number, and / or frequency range. The second Wi-Fi channel, which differs from the first, can be one of the Wi-Fi channels specified in the existing IEEE 802.11 standards or a new channel that might be introduced in the future.Furthermore, the network device can instruct the first AP and the second AP to begin a second FTM sequence.

[0044] Furthermore, in step 308, the network device can receive a second set of FTM metrics between the first and second APs over the second frequency from one or both APs. Specifically, after reconfiguration and receiving the instruction to perform the second FTM sequence, either the first AP or the second AP can initiate a ranging request and generate the second set of FTM metrics (e.g., FTM distance and signal strength) by performing ranging according to the FTM protocol specified in IEEE 802.11mc. The network device can record the second set of FTM metrics in program data, for example, in program data 208 (see [reference]). Fig. ).

[0045] After receiving the first and second sets of FTM metrics, the network device in step 310 can determine, based on these metrics, whether the first and second APs are line-of-sight (i.e., whether the AP pair is a line-of-sight pair). Measurements taken during the FTM sequences can vary considerably if the FTM distance measurement is performed over different frequencies, such as different Wi-Fi channels. This is because signal propagation varies along non-line-of-sight paths due to fluctuating phase and reflection coefficients, resulting in different superpositions of the multipath signal reception at the receiving AP. Accordingly, the network device can look for such variations in the received FTM metrics to determine whether the first and second APs are line-of-sight.In some examples, the network device can derive additional parameters such as standard deviations and means of the FTM metrics and classify the AP pair as a LoS pair or NLoS pair based on these derived parameters. Further details regarding the classification of the AP pair are provided in conjunction with [reference to relevant documentation]. Fig. described

[0046] In Fig. A flowchart of another example procedure 400 for classifying an AP pair is presented. The in Fig. The steps shown can be performed by any suitable device, such as a network device (e.g., network device 102 from Fig. or the network device 200 of Fig. ). In some examples, the appropriate device may be a processing resource (e.g., the processing resource 202 of Fig.) for retrieving and executing instructions stored in a machine-readable storage medium (e.g., the machine-readable storage medium 204 of Fig. ) are stored. Alternatively or additionally to retrieving and executing instructions, the processing resource can comprise one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits. For illustration, the following correspond to Fig. described examples of the classification of an AP pair, which includes a first AP (e.g., AP 104 of Fig. ) and a second AP (e.g., AP 106 from Fig. ) includes.

[0047] In step 402, the network device can tune the first and second access points (APs) to communicate with each other on a first Wi-Fi channel. Specifically, for this channel tuning in step 402, the network device can transmit the same channel settings, corresponding to the first Wi-Fi channel, to both the first and second APs. Upon receiving the channel setting, the first and second APs can configure the first Wi-Fi channel as their operating channel. The channel setting can include information about the first Wi-Fi channel, such as a channel identifier, a number, and / or a frequency range. The first Wi-Fi channel can be one of the Wi-Fi channels specified in the existing IEEE 802.11 standards or a new channel that can be introduced.In step 402, for example, the network device can tune the first AP and the second AP to operate on channel 36 of the Wi-Fi frequency spectrum.

[0048] Furthermore, in step 404, the network device can instruct the first AP to initiate an initial FTM sequence with the second AP over the first Wi-Fi channel. The network device can send an FTM start command to one of the APs (e.g., the first AP) and instruct the first AP to begin an initial FTM sequence. In response, the first AP can assume the role of initiator and send an initial FTM request to the second AP, thereby informing the second AP that the first FTM session has begun. The first AP can then wait for an acknowledgment from the second AP.

[0049] Upon receiving an acknowledgment from the second access point (AP), the first AP can begin transmitting one or more ranging packets (also known as FTM packets) to the second AP. During an FTM session, the first access point can send one or more FTM packets sequentially or concurrently. For each FTM packet, the responder can send an acknowledgment to the initiator. Based on the timestamps of the FTM packets and their respective acknowledgments, the initiator can calculate an initial set of FTM metrics, such as the FTM distance and the received signal strength (expressed as RSSI values ​​– received signal strength indicator). The FTM distance can be an estimated distance between the initiator and the responder and is determined using techniques described in IEEE standards, such as IEEE 802.11mc.

[0050] The FTM distances and RSSI values ​​determined during the first FTM sequence are referred to as the initial FTM distances and initial RSSI values, respectively. For example, the first set of FTM metrics can be calculated for each FTM exchange that includes an FTM packet and a corresponding acknowledgment. Therefore, if the initial FTM sequence consists of three FTM exchanges, the initiator can calculate the initial FTM distance and initial RSSI value for each exchange. Table 1 below shows an example of an initial set of FTM metrics calculated by the first AP in the initial FTM sequence with three FTM exchanges over the first Wi-Fi channel. Table 1 - Example of the first set of FTM metrics FTM exchange in the first FTM sequence First FTM distances in meters (m) First RSSI values ​​in decibel milliwatts (dBm) 1 10 -50 2 11 -52 3 10.5 -51

[0051] In step 406, the power supply can receive the first set of FTM metrics from the first AP. After completion of the first FTM sequence, the first AP can transmit the first set of FTM metrics to the power supply.

[0052] Furthermore, in step 408, the network device can reconfigure the first and second access points (APs) by adjusting them to communicate on a second Wi-Fi channel. Similar to what was described in conjunction with step 402, the network device can send another common channel setting to the first and second APs, but this time the network device can specify a second Wi-Fi channel that is different from the first. Accordingly, the first and second APs can then designate the second Wi-Fi channel as their operating channels for future communication. For example, during the reconfiguration in step 408, the network device can set the first and second APs to operate on channel 48 of the Wi-Fi frequency spectrum.

[0053] Additionally, in step 410, the network device can instruct the first AP to initiate a second FTM sequence with the second AP over the second Wi-Fi channel. Specifically, the network device can send the FTM start command to one of the APs (e.g., the first AP) and instruct the first AP to begin the second FTM sequence. The first AP can act as the initiator and complete the second FTM sequence in a manner similar to that described in conjunction with step 404. In some examples, the second FTM sequence also includes one or more FTM exchanges, which comprise FTM packets and corresponding acknowledgments. During the second FTM sequence, the first AP can determine a second set of FTM metrics (e.g., FTM distances and RSSI values) over the second Wi-Fi channel. The FTM distances and RSSI values ​​determined during the second FTM sequence are referred to as the second FTM distances and second RSSI values, respectively.

[0054] Table 2 shows an example of FTM metrics calculated by the first AP in the first FTM sequence with three FTM exchanges over the second Wi-Fi channel. Table 2 - Example of a second set of FTM metrics FTM exchange in the second FTM sequence Second FTM distance in meters (m) Second RSSI values ​​in decibel milliwatts (dBm) 1 15 -60 2 16 -62 3 17 -61

[0055] Furthermore, in step 412, the first AP can report the second set of FTM metrics to network device 102.

[0056] Similarly, in some examples, in step 414, the network device can reconfigure the first and second APs to communicate over a third Wi-Fi channel (e.g., channel 136 of the Wi-Fi spectrum), and in step 416, instruct the first AP to initiate a third FTM sequence. In response, the first AP can report a third set of FTM metrics (see Table 3) to the network device. The FTM distances and RSSI values ​​obtained during the third FTM sequence are referred to as the third FTM distances and third RSSI values, respectively. Table 3 - Example of the third set of FTM metrics FTM exchange in the third FTM sequence Third FTM distance in meters (m) Third RSSI values ​​in decibel milliwatts (dBm) 1 8 -45 2 7 -46 3 6 -45

[0057] In some examples, after the FTM metrics have been calculated over a predefined number of Wi-Fi channels, the network device can determine classification features in steps 412-418. These classification features can include, for example, a standard deviation of the FTM distances, a mean of the FTM distances, a standard deviation of the RSSI values, and a mean of the RSSI values.

[0058] Furthermore, in step 418, the first AP can report the third set of FTM metrics to network device 102. It should be noted that the examples provided are not limited with respect to the number of AP reconfigurations. The number of AP reconfigurations can be adjusted by a user, such as an administrator of the networked system in which the APs are deployed.

[0059] For example, in step 420, the network device can determine an FTM distance standard deviation (FTMDIST_STDEV) based on the calculated FTM distances. For instance, depending on the number of FTM sequences performed, the network device can use the calculated FTM distances (e.g., the first FTM distances, the second FTM distances, and the third FTM distances) to determine the FTM distance standard deviation. For the FTM distance values ​​shown in Tables 1, 2, and 3, the FTM distance standard deviation for the AP pair is 4.

[0060] In some examples, the network device in step 422 can also determine an FTM distance average (FTMDIST_MEAN) based on the calculated FTM distances. For example, depending on the number of FTM sequences performed, the network device can use the available FTM distances (e.g., the first FTM distances, the second FTM distances, and the third FTM distances) to calculate the FTM distance average. For the FTM distance values ​​shown in Table 1, Table 2, and Table 3, the FTM distance average for the AP pair is 11.1.

[0061] Furthermore, in some examples in step 424, the network device can determine an RSSI standard deviation (RSSI_STDEV) based on the calculated RSSI values. For example, depending on the number of FTM sequences performed, the network device can use the available RSSI values ​​(e.g., the first RSSI values, the second RSSI values, and the third RSSI values) to calculate the RSSI standard deviation. For the RSSI values ​​shown in Tables 1, 2, and 3, the RSSI standard deviation for the AP pair is 6.9.

[0062] Furthermore, in some examples in step 426, the network device can determine an RSSI mean (RSSI_MEAN) based on the calculated RSSI values. For example, depending on the number of FTM sequences performed, the network device can use the available RSSI values ​​(e.g., the first RSSI values, the second RSSI values, and the third RSSI values) to calculate the RSSI mean. For the RSSI values ​​shown in Table 1, Table 2, and Table 3, the RSSI standard deviation for the AP pair is -52.4.

[0063] Once the classification features are determined, the network device can, in step 428, determine a classification of the AP pair formed by the first AP and the second AP based on these features. For example, the classification features corresponding to the AP pair (the first AP and the second AP) can define a feature vector corresponding to the AP pair (FV_AP1AP2), as shown in Equation 1. FV_AP1AP2=[FTMDIST_STDEV,FTMDIST_MEAN,RSSI_STDEV,RSSI_MEAN]

[0064] For the examples shown with the aid of Tables 1-3, the feature vector corresponding to the AP pair formed by the first AP and the second AP can be [4, 11.1, 6.9, -52.4]. As can be understood, in a given small or large network, there can generally be more than two APs forming more than two AP pairs. Accordingly, using the similar technique described above, the network device can also compute the feature vectors corresponding to several other AP pairs in a networked system, e.g., networked system 100 of Fig. .

[0065] After calculating the feature vectors for the AP pairs in the networked system, the network device can apply a clustering procedure to these feature vectors to group the APs into two clusters. One cluster indicates that the AP pair is a LoS pair, and the other indicates that the AP pair is a NLoS pair. Examples of clustering techniques implemented by the network device include centroid-based clustering, density-based clustering, distribution-based clustering, or combinations thereof. It should be noted that the network device can implement any suitable clustering technique capable of classifying the AP pairs based on the determined feature vectors.

[0066] In certain other examples, the network device can be implemented with artificial intelligence to classify the AP pair based on classification features. In such examples, the network device can implement one or more machine learning (ML) models that are trained to classify AP pairs based on these features during a training phase. Such trained ML models can then be deployed on the network device to derive a classification for a given AP pair based on the respective classification features. TIMESTAMPING OF THE DIRECT RADIO LINK SIGNAL

[0067] This section describes a technique for timestamping a direct wireless path signal through an access point (AP), for example, a receiving AP of APs 104 or 106. As mentioned earlier, the direct path can refer to a straight path between the sending AP and the receiving AP. Exemplary details of the proposed timestamping technique are provided in conjunction with the following. Fig. described.

[0068] Fig. This shows a block diagram of a sample AP 500. The AP 500 from Fig. can be any wireless network device, e.g., one of the APs 104, 106 from Fig. , which receives wireless multipath signals and must timestamp one of the multipath signals that corresponds to the direct path between the two APs

[0069] The AP 500 can contain a processing resource 502 and / or a machine-readable storage medium 504 to perform several operations, which are described in more detail below. Specifically, the AP 500 implements a timestamp engine 506 to identify and timestamp a direct radio path signal received from a transmitting AP. For illustration, the timestamp engine 506 and elements within the timestamp engine 506 are represented by the dashed outline, as they are digital entities that can be in the form of data and / or instructions executable by a physical processing resource, such as the processing resource 502.

[0070] The processing resource 502 can be a physical device, such as a central processing unit (CPU), a microprocessor, a graphics processing unit (GPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), other hardware devices capable of retrieving and executing instructions stored in the machine-readable storage medium 504, or combinations thereof. In one example, the processing resource 502 can retrieve, decode, and execute the instructions stored in the machine-readable storage medium 504 to identify and timestamp a direct wireless path signal received from a transmitting access point.Alternatively or in addition to executing the instructions, the processing resource 502 may include at least one integrated circuit (IC), control logic, electronic circuits or combinations thereof, containing multiple electronic components to perform the functions to be carried out by the AP 500.

[0071] The machine-readable storage medium 504 can be non-transient and is alternatively referred to as non-transient machine-readable storage, which does not include any transient transmission signals. The machine-readable storage medium 504 can be any electronic, magnetic, optical, or other storage medium capable of storing data and / or executable instructions. Examples of machine-readable storage media 504 include RAM, NVRAM, EEPROM, a storage drive (such as an SSD or HDD), flash memory, and the like. The machine-readable storage medium 504 can be encoded with the timestamp engine 506, which aids in the identification and timestamp of a direct wireless path signal. The timestamp engine 506 contains program data 508 and program instructions 510 for managing client device roaming.

[0072] The program data 508 can store a variety of data that can be received, used, and / or generated by the processing resource 502 when the processing resource 502 executes the program instructions 510. In some examples, the program data 508 can contain a database, also called a signal log, that stores the signal strength value and arrival time of each of the multiple signals. Furthermore, in some examples, the processing resource 502 can store in the program data 510 the timestamp values ​​of the direct wireless path signals that the processing resource 502 can identify by executing the program instructions. Additionally, in some examples, the processing resource 502 can store information such as the threshold and the search window in the program data 510.

[0073] In accordance with examples consistent with the present disclosure, the AP 500 can execute the timestamping machine 506 via the processing resource 502, which executes the program instructions 510 to determine a classification of an AP pair, e.g., an AP pair defined by APs 104 and 106 of Fig. is formed. In particular, the processing resource 502 can, in some examples, execute one or more of the program instructions 510 to process the data associated with the Fig.For example, program instructions 510 can contain instructions 512, 514, 516, and 518. Specifically, instruction 512, when executed by processing resource 502, can cause processing resource 502 to receive a plurality of signals from a second AP. Furthermore, instruction 514, when executed by processing resource 502, can cause processing resource 502 to record a signal strength value and arrival time corresponding to each of the multiple signals. Additionally, instruction 516, when executed by processing resource 502, can cause processing resource 502 to identify one or more peak signal strength values ​​in a search window preceding a highest signal strength value from the signal strength values.Furthermore, when executed by the processing resource 502, instructions 518 can cause the processing resource 502 to select a timestamp on a rising edge of an earliest peak value greater than a threshold as the arrival time of the direct wireless path signal.

[0074] Although not shown, in some examples the machine-readable storage medium 504 may be encoded with certain additional executable instructions to perform other operations that are executed by the AP 500 (e.g., one or more of those listed in the Fig. steps described), without limiting the scope of the present disclosure.

[0075] In Fig. A flowchart of an example procedure 600 for timestamping direct wireless path signals is presented. This is shown in Fig.The described procedure can be performed by an access point (AP) receiving multi-path propagation signals. Multi-path propagation signals represent multiple propagations (i.e., signals) of an omnidirectional packet sent from a sender (e.g., another AP or wireless communication device). One of these wireless signals may propagate along the straight path (i.e., the direct path), while the other wireless signals may propagate along non-direct, longer paths. A wireless signal that propagates along the shortest or most direct path is called a direct wireless path signal.

[0076] Signals propagating over multiple paths can, for example, be the multiple propagations of an omnidirectionally transmitted packet, such as an FTM packet or an acknowledgment of the FTM packet. The distance between the sending AP and the receiving AP can be determined more accurately based on such direct-path wireless signals than on other non-direct-path wireless signals. By performing Procedure 600 of Fig. The receiving AP can identify the direct wireless path signal from the received multipath propagation signals and timestamp it. In some examples, the timestamp of the direct wireless path signal can then be used to estimate the distance between the sending AP and the receiving AP according to the FTM techniques described in the IEEE 802.11 standard specifications.

[0077] The suitable device for carrying out method 600 of Fig. The processing resource may include a processing resource for retrieving and executing instructions stored in a machine-readable storage medium. The processing resource and machine-readable storage medium may be exemplary representatives of the processing resource 502 and the machine-readable storage medium 504 of AP 500. Alternatively, or in addition to retrieving and executing instructions, the processing resource may include one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits.

[0078] In step 602, a first access point (AP) receives a multitude of signals (e.g., multipath propagation signals) from a second AP. The first AP is the receiving AP, and is also referred to as the receiving AP. The second AP is the sending AP, and is also referred to as the transmitting AP. Depending on the paths the multipath propagation signals take to reach the first AP, they can arrive at the first AP at different time intervals. For example, path length and / or reflections caused by obstacles such as walls, doors, etc., and their material properties, can lead to varying signal delays, causing the packets to reach the first AP at different time intervals.It's possible that only one of these wireless signals took the direct path, while the rest, propagating via multiple paths, took a longer, non-direct route. Therefore, a signal with the highest signal strength isn't always the one taking the shortest or most direct wireless path. Consequently, such a signal with the highest signal strength might not be useful for accurately timestamping the direct wireless path signal. Therefore, the first access point (AP) can perform the following steps to locate and timestamp the direct wireless path signal.

[0079] Furthermore, the first access point in step 604 can record a signal strength value and arrival time for each of the multiple signals. Specifically, the first AP maintains a database, also known as the signal log, in which the signal strength value and arrival time for each of the multiple signals are stored. In some examples, a log entry containing the signal strength value and arrival time for a signal can be created in the signal log after the signal has been received in step 602. Fig. Figure 700 shows a graphic representation depicting the signal strength values ​​logged by the first access point. For easier illustration, Figure 700 is shown by... Fig. simultaneously with Fig. described. In Fig.Reference numbers 702 and 704 represent an X-axis and a Y-axis, respectively. X-axis 702 represents the signal strength in milliwatts (mW), and Y-axis 704 represents the time in nanoseconds (ns). Furthermore, a line graph 703 depicts fluctuations in the signal strength of the radio signals received by the first access point.

[0080] Back to Fig. In step 606, the first AP can identify one or more peak signal strength values ​​within a search window that precedes the highest signal strength value from the signal strength values. The term "search window" as used here can refer to a predetermined time period that depends on a threshold value, which is a function of the signal strength values ​​(described in conjunction with...). Fig.It goes without saying that signals propagating via multiple paths can be attenuated to varying degrees during propagation along the respective wireless paths and due to the presence of multiple obstacles in those paths. Accordingly, the signal strength values ​​of the received signals can vary. From the signal strength values, the first access point can determine peak values ​​(see Fig. ) in the search window, which precede the highest signal strength value. In the graphical representation, 700 of Fig. The search window is, for example, marked with the reference number 706, and the highest signal strength value (also referred to as the "maximum peak") is marked with the reference number 708. Furthermore, the reference numbers 710, 712, and 714 represent peak values ​​of the signal strength (also referred to as "peaks") preceding a radio signal, with the maximum peak being 708.

[0081] Once the peak values ​​have been identified, the first AP in step 608 can select a timestamp on the rising edge of an earliest peak that is greater than the threshold as the arrival time of the direct wireless path signal. The threshold is calculated based on the signal strength values ​​of the signals propagating over multiple paths and received by the first AP, which, in conjunction with a Fig. The described procedure is described. In some examples, the first AP can identify the first wireless signal received during the rising edge of the earliest peak that is greater than the threshold. Fig.The threshold is represented by a horizontal dashed line 716. Accordingly, the first AP can select a wireless signal with the signal strength value marked by a point 718 as the direct wireless path signal. Furthermore, the first AP can select the arrival time (labeled "T1") of this direct wireless path signal (i.e., the projection of point 718 onto the x-axis 702) as the timestamp of the direct wireless path signal. In another example, the first AP can select a time (labeled "T2") at the beginning (labeled with the reference number 720) of the rising edge above the threshold as the timestamp of the direct wireless path signal.

[0082] In Fig. A flowchart of an example procedure 800 for timestamping the direct wireless path signal is shown. The procedure 800 of Fig. is an example of procedure 600 from Fig.In particular, this can be in Fig. The described procedures are performed by an access point (e.g., one of APs 104, 106) that receives signals propagating over multiple paths and timestamps the arrival of the direct wireless path signals. Certain details previously described in Fig. Those already described will not be repeated here for the sake of brevity. Furthermore, Procedure 800 describes certain additional steps that are useful for the AP in determining the threshold. A suitable device for carrying out the procedure is required. Fig.The processing resource may include a processing resource for retrieving and executing instructions stored in a machine-readable storage medium. The processing resource and machine-readable storage medium may be exemplary representatives of the processing resource 502 and the machine-readable storage medium 504 of AP 500. Alternatively, or in addition to retrieving and executing instructions, the processing resource may include one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits.

[0083] In step 802, a first AP (i.e., a receiving AP - an AP that receives multipath propagating signals) receives a multitude of signals (e.g., multipath propagating signals) from a second AP (i.e., a sending AP - an AP that sends an omnidirectional packet).

[0084] Furthermore, the first AP in step 804 can record a signal strength value and arrival time for each of the multiple signals. Specifically, the first AP maintains a signal log in which the signal strength value and arrival time of each of the multiple signals are stored. In some examples, a log entry containing the signal strength value and arrival time for a signal can be created in the signal log after the signal has been received in step 602.

[0085] Furthermore, in step 806, the first AP can identify one or more peak signal strength values ​​in a search window that precedes a highest signal strength value from the signal strength values. It is understood that signals propagating over multiple paths may be attenuated to varying degrees during propagation over the respective wireless paths and due to the presence of multiple obstacles in those paths. Accordingly, the signal strength values ​​of the received signals can vary. Based on the different signal strength values, the first AP can identify peak values ​​(see Fig. ) in the search window, which precede the highest signal strength value.

[0086] Furthermore, the first AP can determine a threshold based on the signal strength values ​​of the signals received by the first AP. To determine the threshold, the first AP can sort the signal strength values ​​in ascending order in step 808. After the signal strength values ​​are sorted in ascending order, the first AP can select a signal strength at a predefined percentile of a total number of signal strength values ​​in step 810. For example, if the predefined percentile is set to 95, the first AP can select the signal strength at the 5th percentile. tenSelect a percentile as the threshold. In one example, the predefined percentile can be selected by a user (e.g., an administrator). In some examples, the predefined percentile can also be customized and / or dynamically determined based on an AP classification (as described previously). The first AP can then use this threshold to locate and timestamp the direct wireless path signal.

[0087] In particular, the first AP in step 812 can identify an earliest peak value that is greater than the threshold. The first AP can compare the recorded signal values ​​in order of their arrival time with the threshold to determine the earliest peak value that is greater than the threshold.

[0088] Furthermore, in step 814, the first AP can select a timestamp on the rising edge of the earliest peak that exceeds the threshold as the arrival time of the direct wireless path signal. In some examples, the first AP can identify the first wireless signal received on the rising edge of the earliest peak that exceeds the threshold. In another example, the first AP can select a time at the beginning of the rising edge above the threshold as the timestamp of the direct wireless path signal. VOICE OF TIMESTAMP PARAMETERS

[0089] Classifying an AP pair (described in the section "AP Pair Classification")—including the first AP and the second AP, which are the LoS pair or NLoS—can be useful when adjusting the timestamping of the direct wireless path signal (described in the section "Timetamping of the Direct Wireless Path Signal"). Specifically, the first AP can be configured to identify the AP pair classification associated with an AP pair [consisting of the first AP (the receiving AP) and a second AP (the transmitting AP sending the multipath propagation signals to the receiving AP)], and adjust the timestamping parameters, such as the search window and / or threshold, based on the AP pair classification to improve timestamping accuracy.

[0090] Fig.shows a flowchart of an example procedure 900 for adjusting a timestamp parameter, such as a threshold value, which is used in the procedures of Fig. The 900 procedure of Fig. can be performed by a suitable device, for example an AP that carries out the Fig. or Fig.The described procedure is carried out. The suitable device may include a processing resource for retrieving and executing instructions stored in a machine-readable storage medium. The processing resource and machine-readable storage medium may be exemplary representatives of the processing resource 502 and the machine-readable storage medium 504 of AP 500. Alternatively or in addition to retrieving and executing instructions, the processing resource may include one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits.

[0091] In particular, the first AP in step 902 can identify an AP pair classification associated with an AP pair that includes the first AP (i.e., a receiving AP) and the second AP (i.e., the transmitting AP—an AP that sends the propagating signals to the first AP). The network device stores one AP pair classification for each AP pair in a networked system, for example, networked system 100 of Fig., in the AP pair classification database. In one example, the AP pair classification can be determined by the network device in a manner similar to what is described in the AP PAIR CLASSIFICATION section. In another example, a user, such as a network administrator, can manually set the AP pair classification, and this manually set AP pair classification can be stored in the AP pair classification database. In one example, the first AP sends an AP pair classification query to the network device (for example, network device 102 of Fig. In response to the AP pair classification request, the network device can send the AP pair classification to the first AP.

[0092] In another example, the first AP can search an AP pair classification store to find a classification tag associated with the AP pair (i.e., the AP pair comprising the first AP and the second AP). Specifically, the APs in the networked system can maintain a local list of their neighboring APs. Furthermore, the APs can download the AP pair classification for their respective neighboring APs from the network device, such as network device 102. Similarly, the first AP can have downloaded the AP pair classification corresponding to each of its neighboring APs from the network device into its AP pair classification store. Accordingly, to identify the AP pair classification of the first AP and the second AP, the first AP can search its AP pair classification store.

[0093] Furthermore, the first AP in step 904 can perform a check to determine whether the classification of the AP pair indicates that it is an NLoS pair.

[0094] If step 904 determines that the AP pair classification indicates the AP pair is an NLoS pair, the first AP in step 906 can decrease the threshold. Conversely, if step 904 determines that the AP pair classification indicates the AP pair is not an NLoS pair (i.e., the AP pair is a LoS pair), the first AP in step 908 can increase the threshold. In some examples, the amount by which the threshold is increased or decreased can be adjusted and controlled by the user. In some examples, the first AP can increase (in step 908) or decrease (in step 906) the threshold by a fixed, predefined amount.

[0095] For the NLoS-AP pair, the direct signal path can be extremely attenuated or completely blocked, resulting in an actual timestamp well before the maximum peak. Reducing the threshold percentile would help detect an earlier peak than the direct radio signal, increasing the likelihood of correctly identifying the direct radio signal. Such a threshold reduction can improve timestamp accuracy.

[0096] Fig. shows a flowchart of an example procedure 1000 for adjusting a timestamp parameter, such as a search window, which is used in the procedures of Fig. The procedure 1000 of Fig. can be performed by a suitable device, for example an AP that carries out the Fig. or Fig.The described procedure is carried out. The suitable device may include a processing resource for retrieving and executing instructions stored in a machine-readable storage medium. The processing resource and machine-readable storage medium may be exemplary representatives of the processing resource 502 and the machine-readable storage medium 504 of AP 500. Alternatively or in addition to retrieving and executing instructions, the processing resource may include one or more electronic circuits containing electronic components for performing the functionality of one or more instructions, such as an FPGA, ASIC, or other electronic circuits.

[0097] In particular, the first AP in step 1002 can identify an AP pair classification associated with an AP pair comprising the first AP (i.e., a receiving AP) and the second AP (i.e., the transmitting AP—an AP that sends the propagating signals to the first AP). The first AP can be one or more of those associated with step 902 of Fig. Apply the described techniques to determine the classification of the AP pair.

[0098] Furthermore, the first AP in step 1004 can perform a check to determine whether the classification of the AP pair indicates that it is an NLoS pair.

[0099] If, in step 1004, the AP pair classification indicates that the AP pair is an NLoS pair, the first AP in step 1006 can expand (or enlarge) the search window. Conversely, if, in step 1004, the AP pair classification indicates that the AP pair is not an NLoS pair (i.e., the AP pair is a LoS pair), the first AP in step 1008 can shrink the search window. In some examples, the extent of the search window expansion or shrinkage can be customizable and controlled by the user. In some examples, the first AP can expand (in step 1006) or shrink (in step 1008) the search window for a fixed, predefined duration.

[0100] As previously mentioned, the direct signal path for the NLoS-AP pair can be extremely attenuated or completely blocked, resulting in a timestamp that is far ahead of the maximum peak value. Reducing the search window for the LoS-AP pair would result in a timestamp closer to the maximum peak of the direct wireless signal, thus avoiding some noise and underestimating the range measurement. Increasing the search window for the NLoS pair also causes the first AP to establish an earlier peak value than the direct radio path signal, increasing the probability of correctly identifying the direct radio path signal. Therefore, the proposed technique improves the accuracy of the timestamp for both the LoS and NLoS-AP pairs by adaptively adjusting the search window and / or threshold.

[0101] Fig.This shows a block diagram of an example computer system 1100, in which various examples described here can be implemented. In one example, computer system 1100 can be configured to use a network device such as network device 102. Fig. works and can perform various operations that are shown in one or more of the earlier drawings (e.g. Fig. ) are described. In another example, the computer system 1100 can be an access point, like one of AP 104, 106, and can perform various operations described in one or more of the earlier drawings (e.g. Fig.Examples of devices and / or systems that can be implemented as Computer System 1100 include desktop computers, laptops, servers, web servers, authentication servers, AAA servers, DNS servers, DHCP servers, IP servers, VPN servers, network policy servers, mainframes, tablet computers, e-readers, netbook computers, televisions and similar monitors (e.g., smart TVs), content receivers, set-top boxes, PDAs, mobile phones, smartphones, virtual terminals, video game consoles, virtual assistants, IoT devices, and the like.

[0102] The computer system 1100 can include a bus 1102 or other communication mechanisms for transmitting information, a hardware processor, also referred to as the processing resource 1104, and a machine-readable storage medium 1105 connected to the bus 1102 for processing information. In some examples, the processing resource 1104 can include one or more CPUs, semiconductor-based microprocessors, and / or other hardware devices capable of retrieving and executing instructions stored in the machine-readable storage medium 1105. The processing resource 1104 can retrieve, decode, and execute instructions to configure MLO for SSIDs.Alternatively or in addition to retrieving and executing instructions, the processing resource 1104 may contain one or more electronic circuits that contain electronic components for performing the functionality of one or more instructions, such as an FPGA, an ASIC, or other electronic circuits.

[0103] In some examples, the machine-readable storage medium 1105 may include main memory 1106, such as RAM, a cache, and / or other dynamic storage devices, connected to the bus 1102 to store information and instructions to be executed by the processing resource 1104. The main memory 1106 may also be used to store temporary variables or other intermediate information during the execution of instructions to be carried out by the processing resource 1104. Such instructions, when stored in storage media accessible to the processing resource 1104, make the computer system 1100 a specialized machine adapted to perform the operations specified in the instructions.The machine-readable storage medium 1105 may further include a read-only memory (ROM) 1108 or another static storage device connected to the bus 1102 to store static information and instructions for the processing resource 1104. Furthermore, the machine-readable storage medium 1105 may include a storage device 1110, such as a magnetic disk, an optical disk, or a USB flash drive, etc., which may be connected to the bus 1102 to store information and instructions.

[0104] In some examples, the bus 1102 of the computer system 1100 can be connected to a display 1112, such as a liquid crystal display (LCD) (or a touchscreen), to show information to a computer user. In some examples, an input device 1114, including alphanumeric and other keys (physical or software-generated and displayed on a touchscreen), can be connected to the bus 1102 to transmit information and command selections to the processing resource 1104. In some examples, another type of user input device, such as a cursor controller 1116, can also be connected to the bus 1102. The cursor controller 1116 can be a mouse, a trackball, or cursor directional keys.The cursor controller 1116 can transmit directional information and command selections to the processing resource 1104 to control cursor movement on the display 1112. In some other examples, the same directional information and command selections as with the cursor controller can be implemented by receiving touch inputs on a touchscreen without a cursor.

[0105] In some examples, the Computer System 1100 may include a user interface module for implementing a graphical user interface (GUI), which can be stored on a mass storage device as executable software code that is executed by the computer device(s). This and other modules may include components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables.

[0106] The 1100 computer system also includes a network interface 1118, which is connected to bus 1102. Network interface 1118 provides two-way data communication and is connected to one or more network links, which in turn are connected to one or more local area networks (LANs). For example, network interface 1118 could be an ISDN (Integrated Services Digital Network) card, a cable modem, a satellite modem, or a modem to establish a data communication connection to a corresponding type of telephone line. Alternatively, network interface 1118 could be a LAN (Local Area Network) card or a wireless communication device (e.g., a Wi-Fi chip / module).

[0107] In some examples, the machine-readable storage medium 1105 (e.g., one or more of the main memory 1106, the ROM 1108, or the storage device 1110) stores instructions 1107 (marked with dashed outlines) which, when executed by the processing resource 1104, can cause the processing resource 1104 to perform one or more of the methods / operations described herein. The instructions 1107 can be stored in main memory 1106, ROM 1108, or the storage device 1110. In some examples, the instructions 1107 can be distributed across main memory 1106, ROM 1108, or the storage device 1110. In some examples, when executed by the processing resource 1104, the instructions 1107 can cause the processing resource 1104 to perform one or more of the operations described herein. Fig.are described. In some other examples, instructions 1107, when executed by processing resource 1104, can cause processing resource 1104 to execute one or more of the actions described in the Fig. .

[0108] Unless explicitly stated otherwise, the terms and expressions used in this document, as well as their variations, are to be understood as non-restrictive and open-ended. For example, the term "including" is to be understood as "including, without limitation" or the like. The term "example" is used to provide illustrative examples of the subject under discussion, not as an exhaustive or limiting list. The terms "a" or "an" are to be understood as "at least one," "one or more," or the like. The presence of expansive words and expressions such as "one or more," "at least," "but not limited to," or similar expressions in some cases is not to be understood as implying that the narrower case is intended or required when such expansive expressions are absent.Furthermore, the term "and / or," as used here, refers to and includes all possible combinations of the listed elements. It is also understood that, although the terms "first," "second," "third," etc., may be used here to describe different elements, these elements should not be restricted by these terms, as these terms are only used to distinguish one element from another unless otherwise specified or the context makes otherwise clear.

Claims

[1] Procedure comprising the following: Configuring a first access point (AP) and a second AP by a network device to communicate over a first frequency; Receiving an initial set of Fine Timing Measurement (FTM) metrics between the first AP and the second AP over the first frequency from one or both, the first AP or the second AP, by the network device; Reconfiguring the first AP and the second AP by the network device to communicate over a second frequency that differs from the first frequency; Receiving a second set of FTM metrics between the first AP and the second AP over the second frequency from one or both, the first AP or the second AP, by the network device; and Determine, via the network device, whether the first AP and the second AP are in line of sight (LoS), based on the first set of FTM metrics and the second set of FTM metrics. [2] Method according to claim 1, wherein the configuration comprises tuning the first AP and the second AP to communicate with each other on a first Wireless Fidelity (Wi-Fi) channel. [3] Method according to claim 1, wherein the reconfiguration comprises the coordination of the first AP and the second AP to communicate with each other on a second Wi-Fi channel. [4] The method of claim 1 further comprising: Instructing the first AP via the network device to initiate an initial FTM sequence with the second AP over the first frequency, after the first AP and the second AP have been configured to communicate over the first frequency; and Instructing the first AP by the network device to initiate a second FTM sequence with the second AP over the second frequency after the first AP and the second AP have been reconfigured to communicate over the second frequency, wherein both the first FTM sequence and the second FTM sequence include one or more FTM exchanges. [5] Method according to claim 4, wherein: the first set of FTM metrics includes one or more initial FTM distances between the first AP and the second AP, one or more initial signal strength values ​​between the first AP and the second AP, or both, determined during the first FTM sequence; and The second set of FTM metrics includes one or more second FTM distances between the first AP and the second AP, or one or more second signal strength values ​​between the first AP and the second AP, or both, determined during the second FTM sequence. [6] The method of claim 5 further comprising the calculation of one or more of the following quantities by the network device: a first standard deviation of one or more first FTM distances and one or more second FTM distances; and a first mean value from the one or more first FTM distances and the one or more second FTM distances. [7] The method of claim 6 further comprising classifying a pair of the first AP and the second AP into one of two clusters based on the first standard deviation or the first mean or several of them. [8] The method of claim 6 further comprising the calculation of one or more of the following elements: a second standard deviation of one or more of the first signal strength values ​​and of one or more of the first signal strength values; and a second mean value from the one or more first signal strength values ​​and the one or more first signal strength values. [9] The method of claim 8 further comprising classifying a pair of the first AP and the second AP into two clusters based on the first standard deviation, the first mean, the second standard deviation or the second mean using a clustering technique. [10] Method according to claim 9, wherein the clustering technique comprises centroid-based clustering, density-based clustering, distribution-based clustering or combinations thereof. [11] Network device with: a machine-readable storage medium that stores executable instructions; and a processing resource coupled to the machine-readable storage medium, wherein the processing resource is configured to execute one or more of the instructions to: Configure a first access point (AP) and a second AP to communicate on a first frequency; Receiving an initial set of Fine Timing Measurement (FTM) metrics between the first AP and the second AP over the first frequency of one or both, the first AP or the second AP; Reconfigure the first AP and the second AP so that they communicate via a second frequency that differs from the first frequency; Receiving a second set of FTM metrics between the first AP and the second AP via the second frequency from one or both, the first AP or the second AP; and Determine if the first AP and the second AP are in line of sight (LoS) based on the first set of FTM metrics and the second set of FTM metrics. [12] Network device according to claim 11, wherein: To configure the first AP and the second AP, the processing resource is configured to execute one or more of the commands to synchronize the first AP and the second AP to communicate with each other on a first Wireless Fidelity (Wi-Fi) channel; and To reconfigure the first AP and the second AP, the processing resource is configured to execute one or more of the instructions to tune the first AP and the second AP to communicate with each other on a second Wi-Fi channel. [13] Network device according to claim 11, wherein the processing resource is configured to execute one or more of the instructions to: instruct the first AP to initiate an initial FTM sequence with the second AP over the first frequency, after the first AP and the second AP have been configured to communicate over the first frequency; and instruct the first AP to initiate a second FTM sequence with the second AP over the second frequency after the first AP and the second AP have been reconfigured to communicate over the second frequency, with both the first FTM sequence and the second FTM sequence including one or more FTM exchanges. [14] Network device according to claim 13, wherein: the first set of FTM metrics includes one or more initial FTM distances between the first AP and the second AP, one or more initial signal strength values ​​between the first AP and the second AP, or both, determined during the first FTM sequence; and The second set of FTM metrics includes one or more second FTM distances between the first AP and the second AP, or one or more second signal strength values ​​between the first AP and the second AP, or both, determined during the second FTM sequence. [15] Network device according to claim 14, wherein the processing resource is configured to execute one or more of the instructions to compute one or more of the following elements: a first standard deviation of one or more first FTM distances and one or more second FTM distances; a first mean value from the one or more first FTM distances and the one or more second FTM distances; a second standard deviation of one or more of the first signal strength values ​​and of one or more of the first signal strength values; and a second mean value from the one or more first signal strength values ​​and the one or more first signal strength values. [16] Network device according to claim 15, wherein the processing resource is configured to execute one or more of the instructions to classify a pair of the first AP and the second AP into two clusters based on the first standard deviation, the first mean, the second standard deviation or the second mean. [17] Non-transitory machine-readable medium that stores instructions which can be executed by a processing resource, wherein the instructions include: Instructions to configure a first access point (AP) and a second AP to communicate over a first wireless fidelity (Wi-Fi) channel; Instructions for receiving an initial set of Fine Timing Measurement (FTM) metrics between the first AP and the second AP over the first Wi-Fi channel from one or both, the first AP or the second AP; Instructions to configure the first AP and the second AP to communicate over a second Wi-Fi channel that is different from the first Wi-Fi channel; Instructions for receiving a second set of FTM metrics between the first AP and the second AP over the second Wi-Fi channel from one or both, the first AP or the second AP; and Instructions to determine whether the first AP and the second AP are in line of sight (LoS) based on the first set of FTM metrics and the second set of FTM metrics. [18] Non-transitory machine-readable medium according to claim 17, wherein: the first set of FTM metrics includes one or more initial FTM distances between the first AP and the second AP, one or more initial signal strength values ​​between the first AP and the second AP, or both, determined during an initial FTM sequence; and The second set of FTM metrics includes one or more second FTM distances between the first AP and the second AP, or one or more second signal strength values ​​between the first AP and the second AP, or both, determined during a second FTM sequence. [19] Non-transitory machine-readable medium according to claim 18, wherein the instructions further comprise: Instructions for calculating a first standard deviation of one or more first FTM distances and one or more second FTM distances; Instructions for calculating a first mean of one or more first FTM distances and one or more second FTM distances; Instructions for calculating a second standard deviation of one or more initial signal strength values ​​and of one or more initial signal strength values; and Instructions for calculating a second mean value from the one or more first signal strength values ​​and the one or more first signal strength values. [20] Non-transitory machine-readable medium according to claim 19, wherein the instructions further include instructions for classifying a pair of the first AP and the second AP into two clusters based on the first standard deviation, the first mean, the second standard deviation or the second mean.

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