WO2022217588A1

WO2022217588A1 - Fine timing measurement in centralized wlan

Info

Publication number: WO2022217588A1
Application number: PCT/CN2021/087812
Authority: WO
Inventors: Haibo Wen; Kaibin Zhang; Fanxiang Bin
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy
Priority date: 2021-04-16
Filing date: 2021-04-16
Publication date: 2022-10-20
Also published as: CN117178603A

Abstract

Example embodiments of the present disclosure relate to devices, methods, apparatuses and computer readable storage media of fine timing measurement in the centralized WLAN architecture. The method comprises: establishing, at a wireless termination device, a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the wireless termination device connected to an access controller of the centralized WLAN; and causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the wireless termination device and the first terminal device. By means of the FTM request and response message pair, a network-side FTM procedure can be initiated between the wireless termination point of the centralized WLAN and the terminal device. As such, the potential transmission delay introduced by L2/L3 network elements is avoided and the RTT related to FTM can be determined more accurately.

Description

FINE TIMING MEASUREMENT IN CENTRALIZED WLAN

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to devices, methods, apparatus and computer readable storage media of fine timing measurement.

BACKGROUND

Wireless local area network (WLAN) has been widely used in indoor and outdoor environments for connecting terminal devices to the Internet, and it has also been identified as an ideal connectivity platform for the Internet of Things (IoT) . The terminal devices access the WLAN through access points (APs) . In a legacy standalone AP architecture, autonomous AP, which is also known as fat AP, typically supports wireless access, security, dialling and routing functions and the control plane and the data plane are locally implemented at the AP. Thus, there is no centralized controller in the network architecture. However, the APs have to be configured one-by-one, this may increase the difficulty in controlling or managing the separate APs, especially when the number of APs in the network is large, such as, in an enterprise network.

To simplify the management and control of the WLAN network, a centralized WLAN architecture has been defined in control and provisioning of wireless access points protocol (CAPWAP) . Specifically, in the centralized WLAN architecture, the access points, also known as fit APs or wireless termination points (WTPs) , only support the wireless access function, and a rest of the functions are provided by an access controller (AC) . In other words, the WTP acts as a managed role, and the AC acts as a management and control role. Moreover, asset tracking or positioning function is also implemented at the access controller by delivery action management frames with terminal devices.

SUMMARY

In general, example embodiments of the present disclosure provide a solution of fine timing measurement in centralized WLAN architecture.

In a first aspect, there is provided a wireless termination device. The wireless termination device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device at least to: establish a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the wireless termination device connected to an access controller of the centralized WLAN; and cause a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the wireless termination device and the first terminal device.

In a second aspect, there is provided an access controller. The access controller comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the access controller at least to: transmit, to a wireless termination device connected to the access controller, a FTM request message indicating a first terminal device; and receive, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.

In a third aspect, there is provided a method. The method comprises: establishing, at a wireless termination device, a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the wireless termination device connected to an access controller of the centralized WLAN; and causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the wireless termination device and the first terminal device.

In a fourth aspect, there is provided a method. The method comprises: transmitting, at an access controller of a centralized wireless local area network, WLAN, a FTM request message to a wireless termination device connected to the access controller, the FTM request message indicating a first terminal device within the centralized WLAN; and receiving, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.

In a fifth aspect, there is provided a first apparatus comprising: means for establishing a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the first apparatus connected to an access controller of the centralized WLAN; and means for causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the first apparatus and the first terminal device.

In a sixth aspect, there is provided a second apparatus comprising: means for transmitting a FTM request message to a wireless termination device connected to the second apparatus of a centralized wireless local area network, WLAN, the FTM request message indicating a first terminal device within the centralized WLAN; and means for receiving, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.

In a seventh aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the third aspect.

In an eighth aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fourth aspect.

Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

FIG. 1 shows a schematic diagram of an example deployment in a centralized WLAN system;

FIG. 2 shows an example environment in which example embodiments of the present disclosure can be implemented;

FIG. 3 shows a signaling chart illustrating a fine timing measurement procedure according to some example embodiments of the present disclosure;

FIG. 4A shows a flowchart of an example FTM request message according to some example embodiments of the present disclosure;

FIG. 4B shows a flowchart of an example FTM response message according to some example embodiments of the present disclosure;

FIG. 5 shows a flowchart of an example control message format according to some example embodiments of the present disclosure;

FIG. 6 shows a flowchart of an example method for fine timing measurement according to some example embodiments of the present disclosure;

FIG. 7 shows a flowchart of an example method for fine timing measurement according to some example embodiments of the present disclosure;

FIG. 8 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 9 shows a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish functionalities of various elements. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as fifth generation (5G) systems, Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) new radio (NR) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR Next Generation NodeB (gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology. The network device is allowed to be defined as part of a gNB such as for example in CU/DU split in which case the network device is defined to be either a gNB-CU or a gNB-DU.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. The terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “end device” , “stations” , “STA” , “user equipment” and “UE” may be used interchangeably.

FIG. 1 shows a schematic diagram of an example deployment 100 in a centralized WLAN system. As shown in FIG. 1, the legacy centralized WLAN system 100 includes wireless termination devices 110-1 to 110-3 (e.g., WTPs) , the L2/L3 network devices 112 and an access controller 120.

The wireless termination devices 110-1 to 110-3, which may collectively refer to wireless termination device 110, may be physical or network entities that include radio frequency antennas and other wireless elements for transmission and receipt of station traffic with wireless access network. The wireless termination devices 110-1 to 110-3 typically only support the wireless access function, and a rest of the functions, such as, security, dialling and routing functions as well as the control plane, the data plane and the management plane are provided by the access controller 120.

There are two working modes in the centralized WLAN architecture, that is, split-MAC mode, and local-MAC mode. In the split-MAC mode, all the L2 wireless data and management frames are encapsulated via the CAPWAP protocol and exchanged between the wireless termination device 110 and the access controller 120. The local-MAC mode allows the data frames to be either locally bridged or tunnelled as 802.3 frames. Further, action frames according to IEEE 802.11 are directly delivered between terminal devices (not shown in FIG. 1) , such as, UE/terminal and the access controller 120 via the wireless termination device 110. In other words, the wireless termination device 110 merely forwards the action frames without any processing.

As previously mentioned, the asset tracking or positioning function is implemented at the access controller 120 by delivery action management frames with terminal devices. Specifically, in order to obtain a location of the terminal device, the FTM is performed between the terminal device and the access controller 120. The FTM allows a station to determine its distance from another station. The Round-Trip-Time (e.g., RTT) related to a FTM session may be calculated via timestamps measured by a requesting station and a responding station, then the distance can be derived.

However, as shown in FIG. 1, all the action management frames delivered between the terminal device and the access controller 120 are forwarded by the wireless termination device 110 and as well as one or more L2/L3 network elements. As a result, a transmission delay between the wireless termination device 110 and the access controller 120 is introduced, and the RTT obtained from the FTM procedure is in fact the one between the terminal device and the access controller 120, rather than the one for the air interface. Based on such RTT, it is hard to derive an accurate distance from the terminal device to wireless termination device 110.

In order to solve the above and other potential problems, embodiments of the present disclosure provide an enhanced FTM mechanism for the centralized WLAN. In general, the WTP of the centralized WLAN is capable of performing FTM session with the terminal devices, rather than simply forwarding the FTM action frames from the terminal device to the access controller 120. Further, by means of the FTM request and response message pair, a network-side FTM procedure can be initiated between the wireless termination point of the centralized WLAN and the terminal device. As such, the potential transmission delay introduced by

layer

2 or 3 network elements is avoided and the RTT related to FTM can be determined more accurately.

FIG. 2 shows an example environment 200 in which example embodiments of the present disclosure can be implemented. As shown in FIG. 2, the network system 200 may be a centralized WLAN architecture, and at least include a wireless termination device 210, an access controller 220, and terminal devices 230-1 and 230-2 (which may be collectively referred to as terminal device 230) . The wireless termination device 210 and the access controller 220 connect the terminal device 230 to the Internet 240.

The wireless termination device 210 may be network devices, such as, fit APs or WTPs that support the wireless access function. In addition, the wireless termination device 210 may be provided with a FTM module (not shown) for performing FTM session with the terminal device 230. For example, the FTM module may implement the functions of FTM as per IEEE 802.11. The FTM session may be performed by delivery FTM frames (e.g., action management frames) between the wireless termination device 210 and the terminal device 230.

Depending on the initiator of the FTM session, the FTM session may include a network-side initiating FTM procedure and a UE-side initiating FTM procedure. In the context of the present disclosure, the station that initiates the FTM session may be referred to as a requesting station, and the other station that perform the FTM session with the requesting station may be referred to as a responding station.

The access controller 220 may be the network device that implements security, dialling and routing functions. In addition, the access controller 220 may provide access to the control plane, the data plane and the management plane of the centralized WLAN 200 to the wireless termination device 210.

The access controller 220 may initiate the network-side initiating FTM procedure. For example, the access controller 220 may transmit a FTM request message to the wireless termination device 210. The FTM request message may include a list of desired terminal devices (e.g., terminal devices 230-1 and 230-2) to be measured by using the FTM session.

The wireless termination device 210 may perform FTM sessions with the corresponding terminal devices in the list, and transmit a FTM response message indicating the RTT to the access controller 220, which will be discussed in details below.

The terminal devices 230 may access to the Internet 240 through the wireless termination device 210. In addition, the terminal devices 230 may initiate the UE-side initiating FTM procedure. For example, the terminal devices 230 may transmit an initial FTM request to the wireless termination device 210, and then the FTM session will be initiated between the terminal devices 230 and the wireless termination device 210.

It is to be understood that the number of network devices shown in FIG. 2 is given for the purpose of illustration without suggesting any limitations. The network architecture 200 may include any suitable number of terminal devices, WTPs and additional devices adapted for implementing implementations of the present disclosure. Although illustrated as mobile phones, the terminal device 230 may be other device than a mobile phone or a part of a mobile phone.

Depending on the communication technologies, the network architecture 200 may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Address (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency-Division Multiple Access (OFDMA) network, a Single Carrier-Frequency Division Multiple Access (SC-FDMA) network or any others. Communications discussed in the network 100 may conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation of communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.

Principle and implementations of the present disclosure will be described in detail below with reference to FIGs. 3 to 7. FIG. 3 shows a signaling chart illustrating a fine timing measurement procedure according to some example embodiments of the present disclosure. For the purpose of discussion, the process 300 will be described with reference to FIG. 2. The process 300 may involve the wireless termination device 210, the access controller 220 and the terminal device 230.

As mentioned above, depending on the initiator of the FTM session, the FTM session includes the network-side initiating FTM procedure and the UE-side initiating FTM procedure. As shown in FIG. 3, the phase 301 indicates the UE-side initiating FTM procedure, and the phase 302 indicates the network-side initiating FTM procedure. It should be understood that there is no limitation on the order of execution between the phase 301 and phase 302.

In phase 301, the terminal device 230-1 acts as the requesting station, while the wireless termination device 210 acts as the responding station. The terminal device 230-1 transmits 305 an initial FTM request to the wireless termination device 210. Upon receipt of the initial FTM request, the wireless termination device 210 transmits 310 an acknowledgement response to the terminal device 230-1. As such, a FTM session may be initiated between the wireless termination device 210 and the terminal device 230-1.

The wireless termination device 210 then transmits 315 a first FTM message with a first timestamp t ₁ to the terminal device 230-1. The first timestamp t ₁ may indicate the time for transmission the first FTM message at the wireless termination device 210.

Upon receipt of the first FTM message, the terminal device 230-1 transmits 320 a first acknowledgement message for the first FTM message to the wireless termination device 210. The wireless termination device 210 receives the first acknowledgement message with a fourth timestamp t ₄. In other words, the fourth timestamp t ₄ may indicate the time for receipt of the first acknowledgement message at the wireless termination device 210.

From the perspective of the terminal device 230-1, it may also determine timestamps related to the FTM session, for example, a second timestamp t ₂ for receipt of the first FTM message at the terminal device 230-1 and a third timestamp t ₃ for transmission of the first acknowledgement message at the terminal device 230-1. With the first, second, third and fourth timestamps t ₁ to t ₄, the RTT related to the FTM session may be determined as below:

RTT= (t4-t1) - (t3-t2) (1)

For example, the wireless termination device 210 may then transmit 325 a second FTM message indicating the first timestamp t ₁ and the fourth timestamp t ₄ to the terminal device 230-1. The terminal device 230-1 may then determine the RTT related to the FTM session based on the timestamps t ₁ to t ₄, for example, according to the above equation (1) .

Alternatively, the terminal device 230-1 may transmit a third FTM message indicating the second timestamp t ₂ and the third timestamp t ₃ to the wireless termination device 210. Likewise, the wireless termination device 210 may then determine the RTT related to the FTM session based on the timestamps t ₁ to t ₄, for example, according to the above equation (1) .

Based on the RTT, a distance between the terminal device 230-1 and the wireless termination device 210 can be determined as below:

where C represent the velocity of light.

In phrase 302, the wireless termination device 210 acts as the requesting station and the terminal device 230-1 acts as the requesting station. The access controller 220 transmits 335 a FTM request message indicating the terminal device 230-1 to the wireless termination device 210. In some example embodiments, the FTM request message may indicate a list of terminal devices, for example, terminal devices 230-1 and 230-2.

FIG. 4A shows a flowchart of an example FTM request message according to some example embodiments of the present disclosure. As shown in FIG. 4A, the FTM request message may include a field of “number of UE” that specifies the number of terminal device with which the wireless termination device 210 may initiate FTM sessions, and a field of “MAC address list” that specifies the MAC addresses of the terminal device that will work as responding STA of the FTM sessions.

Upon receipt of the FTM request message, the wireless termination device 210 may initiate a FTM session with the terminal device indicated in the FTM request message. Additionally, the wireless termination device 210 may initiate further FTM sessions with the terminal devices other than the terminal device 230-1 in the list, for example, terminal device 230-2.

By way of example, the wireless termination device 210 transmits 340 an initial FTM request to the terminal device 230-1. The terminal device 230-1 may then transmit 345 an acknowledgement response to the wireless termination device 210.

During the FTM session, the wireless termination device 210 may receive 350 a first FTM message with a second timestamp t ₂ from the terminal device 230-1. The second timestamp t ₂ may indicate the time for receipt of the first FTM message at the wireless termination device 210.

Upon receipt of the first FTM message, the wireless termination device 210 transmits 355, to the terminal device 230-1, a first acknowledgement message for the first FTM message with a third timestamp t ₃. The third timestamp t ₃ may indicate the time for transmission of the first acknowledgement message at the wireless termination device 210.

From the perspective of the terminal device 230-1, it may also determine timestamps related to the FTM session, for example, a first timestamp t ₁ for transmission of the first FTM message at the terminal device 230-1 and a fourth timestamp t ₄ for receipt of the first acknowledgement message at the terminal device 230-1.

With the first, second, third, and fourth timestamps t ₁ to t ₄, the RTT related to the FTM session may be determined. For example, the wireless termination device 210 may receive 360 a second FTM message from the terminal device 230-1, and the second FTM message may indicate the first timestamp t ₁ and the fourth timestamp t ₄. Based on the first, second, third, and fourth timestamps t ₁ to t ₄, the RTT related to the FTM session may be determined. For another example, the RTT may be determined at the terminal device 230-1, and the terminal device 230-1 may transmit a third FTM message including the RTT to the wireless termination device 210.

The wireless termination device 210 transmits 365 a FTM response message indicating the RTT related to the FTM, session between the wireless termination device 210 and the terminal device 230-1. The RTT may indicate a distance between the wireless termination device 210 and the terminal device 230-1.

In some example embodiments, the wireless termination device 210 may transmit the FTM response including the first, second, third and fourth timestamps t ₁ to t ₄. As such, with the timestamps t ₁ to t ₄, the access controller 220 may determine the RTT according to the above equation (1) .

In some example embodiments, the wireless termination device 210 may transmit the FTM response including the RTT. Additionally the FTM response message may further indicate a mapping relation between the terminal devices 230-1 and 230-2 in the list and corresponding RTTs. FIG. 4B shows a flowchart of an example FTM response message according to some example embodiments of the present disclosure. As shown in FIG. 4B, the FTM response message includes information, such as <MAC address, RTT> pair, with respect to each terminal device in the list that works as the responding station.

FIG. 5 shows a flowchart of an example control message format according to some example embodiments of the present disclosure. As shown in FIG. 5, the FTM request and response messages are based on the CAPWAP Control protocol. All CAPWAP Control messages are encapsulated within a CAPWAP Header, immediately following the control header.

It should be understood that the above FTM session initiated between the terminal device 230-1 and the wireless termination device 210 is given as an example for FTM without any limitation to the embodiments of the present disclosure, other FTM session including much or less transmission or reception of FTM messages or timestamps may also be possible.

According to the embodiments of the present disclosure, there is provided a solution of fine timing measurement, which is beneficial to a centralized WLAN. In the FTM process, the WTP is able to directly perform the FTM session with the terminal device without introducing transmission delay from other L2/L3 network elements. By means of the FTM request and response message pair, a network-side FTM procedure can be initiated between the WTP of the centralized WLAN and the terminal device. As such, the RTT related to FTM can be determined more accurately.

FIG. 6 shows a flowchart of an example method 600 for fine timing measurement according to some example embodiments of the present disclosure. The method 600 can be implemented at a wireless termination point, e.g., the wireless termination device 210 described with reference to FIG. 2.

At 610, the wireless termination device 210 establishes a FTM, session with a first terminal device within a centralized WLAN, for example, the terminal device 230-1. The wireless termination device 210 may be the WTP and connected to the access controller 220 of the centralized WLAN.

The FTM session may be a network-side initiating FTM procedure or a UE-side initiating FTM procedure. In the embodiments of the network-side initiating FTM procedure, the wireless termination device 210 may initiate a FTM session with the first terminal device 230-1 based on FTM request received from the access controller 220. In these cases, the wireless termination device 210 may act as a requesting station of the FTM session and the first terminal device 230-1 may act as a responding station of the FTM session.

Specifically, in the network-side initiating FTM procedure, the wireless termination device 210 may receive a FTM request from the access controller 220. The FTM request message may indicate a list of terminal devices comprising the first terminal device, for example, a list of terminal devices 230-1 and 230-2. In response to the FTM request message, the wireless termination device 210 may initiate the FTM session with the first terminal device 230-1. Additionally, the wireless termination device 210 may initiate further FTM sessions with the terminal devices other than the first terminal device in the list, such as, the terminal device 230-2.

As an example of the above embodiments, in response to the FTM request message, the wireless termination device 210 may transmit an initial FTM request to the first terminal device 230-1. The wireless termination device 210 may receive, from the first terminal device 230-1, a first FTM message with a second timestamp t ₂. The second timestamp t ₂ may indicate a time for receipt of the first FTM message at the wireless termination device 210. The wireless termination device 210 may transmit, to the first terminal device 230-1, a first acknowledgement message for the first FTM message with a third timestamp t ₃. The third timestamp t ₃ may indicate a time for transmission of the first acknowledgement message at the wireless termination device 210.

From the perspective of the first terminal device 230-1, it may also determine timestamps related to the FTM session, for example, a first timestamp t ₁ for transmission of the first FTM message at the first terminal device 230-1 and a fourth timestamp t ₄ for receipt of the first acknowledgement message at the first terminal device 230-1.

The wireless termination device 210 may then receive a second FTM message from the first terminal device 230-1, and the second FTM message may indicate the first timestamp t ₁ and the fourth timestamp t ₄. Based on the first, second, third, and fourth timestamps t ₁ to t ₄, the RTT related to the FTM session may be determined, which will be discussed in details below.

In the embodiments of the UE-side initiating FTM procedure, the wireless termination device 210 may act as the responding station, and the first terminal device 230-1 may act as the requesting station. In this case, the wireless termination device 210 may receive an initial FTM request from the first terminal device 230-1. In response to, the wireless termination device 210 may establish the FTM session with the first terminal device 230-1.

Specifically, in response to the initial FTM request, the wireless termination device 210 may transmit, to the first terminal device 230-1, a first FTM message with a first timestamp t ₁. The first timestamp t ₁ may indicate a time for transmission of the first FTM message at the first terminal device 230-1. The wireless termination device 210 may receive, from the first terminal device 230-1, a first acknowledgement message for the first FTM message with a fourth timestamp t ₄. The fourth timestamp t ₄ may indicate the time for receipt of the first acknowledgement message at the first terminal device 230-1.

From the perspective of the first terminal device 230-1, it may also determine timestamps related to the FTM session, for example, a second timestamp t ₂ for receipt of the first FTM message at the first terminal device 230-1 and a third timestamp t ₃ for transmission of the first acknowledgement message at the first terminal device 230-1.

The wireless termination device 210 may then transmit a second FTM message indicating the first timestamp t ₁ and the fourth timestamp t ₄ to the first terminal device 230-1 for determining, by the first terminal device 230-1, the RTT based on the first, second, third and fourth timestamps t ₁ to t ₄. Alternatively, the first terminal device 230-1 may transmit a third FTM message indicating the second timestamp t ₂ and the third timestamp t ₃ to the wireless termination device 210 for determining, by the wireless termination device 210, the RTT based on the first, second, third and fourth timestamps t ₁ to t ₄. The embodiments of the present disclosure are not limited in this regard.

At 620, the wireless termination device 210 causes the RTT related to the FTM session to be determined. The RTT may indicate a distance between the wireless termination device 210 and the first terminal device 230-1.

In the case of the network-side initiating FTM procedure, the wireless termination device 210 may transmit a FTM response to the access controller 220, and the FTM response includes the first, second, third and fourth timestamps t ₁ to t ₄ for determining the RTT by the access controller 220. For example, the access controller 220 may determine the RTT based on the above equation (1) .

Alternatively, in the case of the network-side initiating FTM procedure, the wireless termination device 210 may determine the RTT based on the first, second, third, and fourth timestamps t ₁ to t ₄, for example, according to the above equation (1) . The wireless termination device 210 may then transmit, to the access controller 220, a FTM response including the RTT. In addition, the FTM response message may further indicate a mapping relation between the terminal devices (e.g., terminal devices 230-1 and 230-2) in the list and corresponding RTTs.

In the case of the UE-side initiating FTM procedure, the wireless termination device 210 may transmit a second FTM message indicating the first timestamp t ₁ and the fourth timestamp t ₄ to the first terminal device 230-1 for determining, by the first terminal device 230-1, the RTT based on the first, second, third and fourth timestamps t ₁ to t ₄. For example, the first terminal device 230-1 may determine the RTT based on the first, second, third and fourth timestamps t ₁ to t ₄, for example, according to the above equation (1) . Alternatively, the wireless termination device 210 may receive a third FTM message indicating the second timestamp t2 and the third timestamp t3 from the first terminal device 230-1, and the wireless termination device 210 may determine the RTT based on the first, second, third and fourth timestamps t1 to t4, for example, according to the above equation (1) .

According to the example embodiments of the present disclosure, the WTP of the centralized WLAN is capable of establishing the FTM session with the terminal device without any potential transmission delay caused by other L2 or L3 network elements in the centralized WLAN. As such, the RTT related to FTM can be determined more accurately. Further, the RTTs as well as the corresponding terminal devices can be delivered between the WTP and the access controller by means of the FTM request and response message pair.

FIG. 7 shows a flowchart of an example method 700 for fine timing measurement according to some example embodiments of the present disclosure. The method 700 can be implemented at an electronic device in a centralized WLAN, e.g., the access controller 220 described with reference to FIG. 2.

At 710, the access controller 220 transmits, to a wireless termination device 210 connected to the access controller 220, a FTM request message indicating a first terminal device, such as, the terminal device 230-1. In some example embodiments, the FTM request message may indicate a list of terminal devices, for example, terminal devices 230-1 and 230-2.

By way of example, the FTM request message may include a field of number of UE that specifies the number of terminal devices with which the wireless termination device 210 may initiate FTM sessions, and a field of MAC address list that specifies the MAC addresses of the terminal devices that will work as responding STA of the FTM sessions.

At 720, the access controller 220 receives, from the wireless termination device 210, a FTM response message indicating a RTT related to the FTM session between the wireless termination device 210 and the first terminal device 230-1. The RTT may indicate a distance between the wireless termination device 210 and the first terminal device 230-1. In some other example embodiments, the FTM request and response messages may be FTM action frames.

In some example embodiments, the FTM response message may include the RTT. The RTT may be determined by either the wireless termination device 210 or the first terminal device 230-1 based on timestamps obtained from the FTM session. Further, in a case where the FTM request message indicates a list of terminal devices 230-1 and 230-2, the FTM response message may further indicate a mapping relation between the terminal devices 230-1 and 230-2 in the list and corresponding RTTs. For example, the FTM response message may include a mapping relation between the MAC addresses of the terminal devices 230-1 and 230-2 in the list and the corresponding RTTs.

In some other example embodiments, the FTM response message may include a plurality of timestamps obtained from the FTM session. The access controller 220 may then determine the RTT based on the plurality of timestamps. The timestamps obtained from the FTM session may indicate transmission and receipt time of at least one FTM message delivered between the first terminal device 230-1 and the wireless termination device 210, one of which acts as a requesting station, while the other one acts as a responding station.

From the perspective of the wireless termination device 210, upon receipt of the FTM request message from the access controller 220, the wireless termination device 210 may initiate the FTM session with the first terminal device 230-1. In this case, the wireless termination device 210 acts as the requesting station and the first terminal device 230-1 acts as the responding station.

In the above case, the timestamps obtained from the FTM session may include, for example, a first timestamp for transmission of a first FTM message from the first terminal device 230-1 to the wireless termination device 210, a second timestamp for receipt of the first FTM message at the wireless termination device 210, a third timestamp for transmission a first acknowledgement message from the wireless termination device 210 to the first terminal device 230-1, and a fourth timestamp for receipt of the first acknowledgement message at the first terminal device 230-1. The access controller 220 may determine the RTT based on the first, second, third, and fourth timestamps, for example, as shown in the above equation (1) .

It should be understood that the above FTM session initiated between the first terminal device 230-1 and the wireless termination device 210 is given as an example for FTM without any limitation to the embodiments of the present disclosure, other FTM session including much or less transmission or reception of FTM messages or timestamps may also be possible.

According to the example embodiments, a network-side FTM procedure can be initiated between the WTP of the centralized WLAN and the terminal devices without any potential transmission delay caused by other L2 or L3 network elements in the centralized WLAN. Further, by means of the FTM request and response message pair, the access controller is able to obtain more accurate RTTs associated with a list of desired terminal devices from the WTP. As such, either a distance between the WTP and the terminal device or a position of the terminal device within the centralized WLAN can be determined precisely.

In some example embodiments, a first apparatus capable of performing the method 600 (for example, the wireless termination device 210) may comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the wireless termination device 210. In some embodiments, the means may comprise at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured to, with the at least one processor, cause performance of the first apparatus.

In some example embodiments, the first apparatus comprises: means for establishing a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the first apparatus connected to an access controller of the centralized WLAN; and means for causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the first apparatus and the first terminal device.

In some example embodiments, the means for establishing the FTM session comprises: means for receiving a FTM request from the access controller, the FTM request message indicating a list of terminal devices comprising the first terminal device; and means for in response to the FTM request message, initiating the FTM session with the first terminal device.

In some example embodiments, the first apparatus further comprises: means for in response to the FTM request message, initiating further FTM sessions with the terminal devices other than the first terminal device in the list.

In some example embodiments, the means for establishing the FTM session further comprises: means for in response to the FTM request message, transmitting an initial FTM request to the first terminal device; means for receiving, from the first terminal device, a first FTM message with a second timestamp; means for transmitting, to the first terminal device, a first acknowledgement message for the first FTM message with a third timestamp; and means for receiving, from the first terminal device, a second FTM message indicating a first timestamp for transmission of the first FTM message at the first terminal device and a fourth timestamp for receipt of the first acknowledgement message at the first terminal device.

In some example embodiments, the means for causing the RTT to be determined comprises: means for transmitting, to the access controller, a FTM response comprising the first, second, third and fourth timestamps for determining the RTT by the access controller.

In some example embodiments, the means for causing the RTT to be determined comprises: means for determining the RTT based on the first, second, third, and fourth timestamps; and means for transmitting, to the access controller, a FTM response comprising the RTT.

In some example embodiments, the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.

In some example embodiments, the means for establishing the FTM session comprises: means for in response to an initial FTM request received from the first terminal device, establishing the FTM session with the first terminal device.

In some example embodiments, the means for establishing the FTM session comprises: means for in response to the initial FTM request, transmitting, to the first terminal device, a first FTM message with a first timestamp; and means for receiving, from the first terminal device, a first acknowledgement message for the first FTM message with a fourth timestamp.

In some example embodiments, the means for causing the RTT to be determined comprises: means for transmitting a second FTM message indicating the first timestamp and the fourth timestamp to the first terminal device for determining, by the first terminal device, the RTT based on the first timestamp, a second timestamp for receipt of the first FTM message at the first terminal device, a third timestamp for transmission of the first acknowledgement message at the first terminal device, and the fourth timestamp.

In some example embodiments, a second apparatus capable of performing the method 700 (for example, the access controller 220) may comprise means for performing the respective steps of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the access controller 220. In some embodiments, the means may comprise at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured to, with the at least one processor, cause performance of the second apparatus.

In some example embodiments, the second apparatus comprises: means for transmitting a FTM request message to a wireless termination device connected to the second apparatus of a centralized wireless local area network, WLAN, the FTM request message indicating a first terminal device within the centralized WLAN; and means for receiving, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.

In some example embodiments, the FTM response message comprising the RTT.

In some example embodiments, the FTM request message indicates a list of terminal devices comprising the first terminal device, and the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.

In some example embodiments, the FTM response message comprising a plurality of timestamps obtained from the FTM session, and the second apparatus further comprises: means for determining the RTT based on the plurality of timestamps.

In some example embodiments, the FTM request message and the FTM response message comprise action management frames.

FIG. 8 is a simplified block diagram of a device 800 that is suitable for implementing embodiments of the present disclosure. The device 800 may be provided to implement the communication device, for example the wireless termination device 210 or the access controller 220 as shown in FIG. 2. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more transmitters and receivers (TX/RX) 840 coupled to the processor 810.

The TX/RX 840 is for bidirectional communications. The TX/RX 840 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 810 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 824, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 822 and other volatile memories that will not last in the power-down duration.

A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 820. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 820.

The embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to FIGs. 6-7. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 830 may be tangibly contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. FIG. 8 shows an example of the computer readable medium 900 in form of CD or DVD. The computer readable medium has the program 830 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, device, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the

methods

600 and 700 as described above with reference to FIGs. 6-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing device, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, device or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A wireless termination device, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device at least to:

establish a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the wireless termination device connected to an access controller of the centralized WLAN; and

cause a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the wireless termination device and the first terminal device.
The wireless termination device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device to establish the FTM session by:

receiving a FTM request from the access controller, the FTM request message indicating a list of terminal devices comprising the first terminal device; and

in response to the FTM request message, initiating the FTM session with the first terminal device.
The wireless termination device of Claim 2, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the wireless termination device to:

in response to the FTM request message, initiate further FTM sessions with the terminal devices other than the first terminal device in the list.
The wireless termination device of Claim 2 or 3, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the wireless termination device to establish the FTM session by:

in response to the FTM request message, transmitting an initial FTM request to the first terminal device;

receiving, from the first terminal device, a first FTM message with a second timestamp;

transmitting, to the first terminal device, a first acknowledgement message for the first FTM message with a third timestamp; and

receiving, from the first terminal device, a second FTM message indicating a first timestamp for transmission of the first FTM message at the first terminal device and a fourth timestamp for receipt of the first acknowledgement message at the first terminal device.
The wireless termination device of Claim 4, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device to cause the RTT to be determined by:

transmitting, to the access controller, a FTM response comprising the first, second, third and fourth timestamps for determining the RTT by the access controller.
The wireless termination device of Claim 4, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the wireless termination device to cause the RTT to be determined by:

determining the RTT based on the first, second, third, and fourth timestamps; and

transmitting, to the access controller, a FTM response comprising the RTT.
The wireless termination device of Claim 6, wherein the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.
The wireless termination device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device to establish the FTM session by:

in response to an initial FTM request received from the first terminal device, establishing the FTM session with the first terminal device.
The wireless termination device of Claim 8, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the wireless termination device to establish the FTM session by:

in response to the initial FTM request, transmitting, to the first terminal device, a first FTM message with a first timestamp; and

receiving, from the first terminal device, a first acknowledgement message for the first FTM message with a fourth timestamp.
The wireless termination device of Claim 9, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the wireless termination device to cause the RTT to be determined by:

transmitting a second FTM message indicating the first timestamp and the fourth timestamp to the first terminal device for determining, by the first terminal device, the RTT based on the first timestamp, a second timestamp for receipt of the first FTM message at the first terminal device, a third timestamp for transmission of the first acknowledgement message at the first terminal device, and the fourth timestamp.
An access controller, comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the access controller at least to:

transmit, to a wireless termination device connected to the access controller, a FTM request message indicating a first terminal device; and

receive, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.
The access controller of Claim 11, wherein the FTM response message comprising the RTT.
The access controller of Claim 11, wherein the FTM request message indicates a list of terminal devices comprising the first terminal device, and the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.
The access controller of Claim 11, wherein the FTM response message comprising a plurality of timestamps obtained from the FTM session, and the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the access controller to:

determine the RTT based on the plurality of timestamps.
A method comprising:

establishing, at a wireless termination device, a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the wireless termination device connected to an access controller of the centralized WLAN; and

causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the wireless termination device and the first terminal device.
The method of Claim 15, wherein establishing the FTM session comprises:

receiving a FTM request from the access controller, the FTM request message indicating a list of terminal devices comprising the first terminal device; and

in response to the FTM request message, initiating the FTM session with the first terminal device.
The method of Claim 16, further comprising:

in response to the FTM request message, initiating further FTM sessions with the terminal devices other than the first terminal device in the list.
The method of Claim 16 or 17, wherein establishing the FTM session further comprises:

in response to the FTM request message, transmitting an initial FTM request to the first terminal device;

receiving, from the first terminal device, a first FTM message with a second timestamp;

transmitting, to the first terminal device, a first acknowledgement message for the first FTM message with a third timestamp; and

receiving, from the first terminal device, a second FTM message indicating a first timestamp for transmission of the first FTM message at the first terminal device and a fourth timestamp for receipt of the first acknowledgement message at the first terminal device.
The method of Claim 18, wherein causing the RTT to be determined comprises:

transmitting, to the access controller, a FTM response comprising the first, second, third and fourth timestamps for determining the RTT by the access controller.
The method of Claim 18, wherein causing the RTT to be determined comprises:

determining the RTT based on the first, second, third, and fourth timestamps; and

transmitting, to the access controller, a FTM response comprising the RTT.
The method of Claim 20, wherein the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.
The method of Claim 15, wherein establishing the FTM session comprises:

in response to an initial FTM request received from the first terminal device, establishing the FTM session with the first terminal device.
The method of Claim 22, wherein establishing the FTM session comprises:

in response to the initial FTM request, transmitting, to the first terminal device, a first FTM message with a first timestamp; and

receiving, from the first terminal device, a first acknowledgement message for the first FTM message with a fourth timestamp.
The method of Claim 23, wherein causing the RTT to be determined comprises:

transmitting a second FTM message indicating the first timestamp and the fourth timestamp to the first terminal device for determining, by the first terminal device, the RTT based on the first timestamp, a second timestamp for receipt of the first FTM message at the first terminal device, a third timestamp for transmission of the first acknowledgement message at the first terminal device, and the fourth timestamp.
A method comprising:

transmitting, at an access controller of a centralized wireless local area network, WLAN, a FTM request message to a wireless termination device connected to the access controller, the FTM request message indicating a first terminal device within the centralized WLAN; and

receiving, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.
The method of Claim 25, wherein the FTM response message comprising the RTT.
The method of Claim 25, wherein the FTM request message indicates a list of terminal devices comprising the first terminal device, and the FTM response message further indicates a mapping relation between the terminal devices in the list and corresponding RTTs.
The method of Claim 25, wherein the FTM response message comprising a plurality of timestamps obtained from the FTM session, and the method further comprises:

determining the RTT based on the plurality of timestamps.
A first apparatus comprising:

means for establishing a fine timing measurement, FTM, session with a first terminal device within a centralized wireless local area network, WLAN, the first apparatus connected to an access controller of the centralized WLAN; and

means for causing a round-trip time, RTT, related to the FTM session to be determined, the RTT indicating a distance between the first apparatus and the first terminal device.
A second apparatus comprising:

means for transmitting a FTM request message to a wireless termination device connected to the second apparatus of a centralized wireless local area network, WLAN, the FTM request message indicating a first terminal device within the centralized WLAN; and

means for receiving, from the wireless termination device, a FTM response message indicating a round-trip time, RTT, related to a fine timing measurement, FTM, session between the wireless termination device and the first terminal device, the RTT indicating a distance between the wireless termination device and the first terminal device.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 15-24.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 25-28.