Patent Description:
Wireless communication technologies are moving the world toward an increasingly connected and networked society. The rapid growth of wireless communications and advances in technology has led to greater demand for capacity and connectivity. Other aspects, such as energy consumption, device cost, spectral efficiency, and latency are also important to meeting the needs of various communication scenarios. In comparison with the existing wireless networks, next generation systems and wireless communication techniques need to provide support for an increased number of users and devices, as well as support for higher data rates, therein requiring improved location and measurement accuracy and efficiency.

<CIT> relates to methods for determining location of a device by exchanging a plurality of messages with one or more devices.

<CIT> relates to a procedure for determining distance (or angle) between a pair of electronic devices wirelessly connected to one another.

<CIT> relates to a station that receives a schedule from a reference device in a wireless network.

This document relates to methods, systems, and devices for location information determination based on timing measurements, which enable a wireless station to determine its location when, for example, GPS is not available.

In the following description, although numerous features may be designated as optional, it is nevertheless acknowledged that all features comprises in the independent claims are not to be read as optional.

In one exemplary aspect, a wireless communication method is disclosed. The method includes transmitting, by a communication apparatus, a timing request to a subset of a plurality of network devices, where the timing request comprises a respective expected response time for each of the subset of the plurality of network devices, receiving, at a plurality of times, a plurality of timing measurements from each of the subset of the plurality of network devices, where each of the plurality of times is based on the corresponding expected response time, and the plurality of timing measurements comprises a respective time of arrival (ToA) timestamp and a respective time of departure (ToD) timestamp, and determining a location information of the communication apparatus based on an estimate of a round trip delay that is computed using a difference of the respective ToA and ToD timestamps from the plurality of timing measurements.

In another exemplary aspect, a wireless communication method is disclosed. The method includes transmitting a plurality of initial timing requests to a plurality of network devices, receiving a plurality of initial timing responses from a subset of the plurality of network devices, transmitting a timing request to the subset of the plurality of network devices, where the timing request identifies transmission resources to be used by each of the subset of the plurality of network devices, receiving, over the respective transmission resources, a plurality of timing measurements from the subset of the plurality of network devices, where the plurality of timing measurements comprises a respective ToA timestamp and a respective ToD timestamp, and determining a location information of the apparatus based on an estimate of a round trip delay that is computed using a difference of the respective ToA and ToD timestamps from the plurality of timing measurements.

In yet another exemplary aspect, a wireless communication method is disclosed. The method includes transmitting, to a group of network devices, a timing request soliciting time measurement responses, the timing request including information for receiving the time measurement responses in a collision-free manner, receiving, in the collision-free manner, the timing measurement responses from at least some network devices from the group, where each timing measurement response includes a first field indicative of a reception time at which a corresponding network device received the timing request and a second field indicative of response time at which the corresponding network device transmitted its timing measurement response, and determining a location of the communication apparatus based on the timing measurement responses.

In yet another exemplary aspect, a wireless communication method is disclosed. The method includes receiving, from a communication apparatus, a timing request comprising a first ToD, an expected response time (ERT), and an identification of a transmission resource, and transmitting, at a calculated time and over the transmission resource, a timing measurement that comprises a ToA timestamp and a second ToD timestamp, wherein the ToA timestamp corresponds to when the timing request was received, wherein the second ToD timestamp corresponds to the calculated time, and wherein the second ToD is equal to a sum of the ToA timestamp and the expected response time.

In yet another exemplary aspect, the above-described methods are embodied in the form of processor-executable code and stored in a computer-readable program medium.

In yet another exemplary embodiment, a device that is configured or operable to perform the above-described methods is disclosed.

Wireless communication systems can include a network of one or more access points (APs) to communicate with one or more wireless stations (STAs). An AP can emit radio signals that carry management information, control information or users' data to one or more wireless stations, and a station can also transmit radio signals to the access point in the same frequency channel via time division duplexing (TDD) or in a different frequency channel via frequency division duplexing (FDD).

IEEE <NUM> is an asynchronous time division duplexing technology used by a wireless local area network (WLAN). The basic unit of WLAN is called a basic service set (BSS). An infrastructure BSS is the BSS with stations that communicate through associating with an Access Point (AP) to connect to the wired network or Internet. In a BSS, both access point and stations share the same frequency channel via using Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) technology, a kind of TDD mechanism, for multiple access and data transmission.

The Global Positioning System (GPS) is a widely used positioning mechanism in wireless communication systems and consumer products. To get the geo-positioning information, the GPS receiver receives signals from at least four GPS satellites. This GPS mechanism may work well in outdoor cases, but not well for indoor environments as the signals from GPS satellites are too weak to penetrate indoors for the GPS receiver to acquire and synchronize with. Therefore, it is beneficial to have geo-positioning mechanisms other than GPS for indoor and/or outdoor environment.

Typical geo-positioning mechanisms for the indoor environment include Wi-Fi-based received signal strength indication (RSSI) measurements and Time of Arrival (ToA) measurements. The RSSI-based method leverages the characteristics of radio signal transmission decay as travelling, and uses the measured RSSI to derive the distance between the transmitter and receiver. On the other hand, ToA-based methods rely on the timing measurement from the initiating station transmitting the measurement signal to receiving the response signal sent from the responding station. Due to space limitations in an indoor environment, the timing measurement method should be very precise, otherwise the timing measurement error may render the measurement results unusable.

A single RSSI or ToA measurement from a reference station cannot be used to determine the position of requesting station precisely. In order to accurately determine the location of a station, multiple distance measurements to multiple reference stations (e.g., APs), whose geo-locations are known in advance, may be required. With multiple measured RSSI or ToA information, a positioning mechanism (e.g., triangulation or fingerprinting) can be used to locate the station that is communicating with those reference stations.

In dense network deployments, however, multiple measurements would reduce the efficiency of the medium/resource usage and may cause air-link traffic congestion when many stations attempt to get their location information.

The rSTA then sends a TM Report to the iSTA.

The procedure described in <FIG>, however, suffers from drawbacks that results in decreases efficiency and more traffic. These drawbacks include:.

Embodiments of the disclosed technology improve, among other things, the efficiency of timing measurement via point-to-multi-point timing measurement exchanges, e.g., the multi-user timing measurement (MU-TM) protocol.

<FIG> shows an example of WLANs for multi-user timing measurement protocol. A wireless communication network (<NUM>) in the example includes three Access Points (APs) <NUM>, <NUM>, and <NUM>, which form three BSSs <NUM>, <NUM>, and <NUM> respectively. The WLAN <NUM> also contains one wireless station (<NUM>) which may associate with AP1 <NUM> in this example. Three BSSes may be overlapped in the coverage area so that the wireless station (<NUM>) could be able to receive/transmit the radio signal from/to those APs, <NUM>, <NUM> and <NUM>.

The APs <NUM>, <NUM> and <NUM> are MU-TM capable access points and broadcast the MU-TM capability information in the management frame periodically or per-request, such as beacon frames, probe response frames, etc. Those APs are operating in the same frequency channel and may support wider bandwidth such as <NUM> or <NUM> in addition to <NUM> bandwidth.

The station <NUM> is in the coverage area of three BSSs. It can receive the management and other types of frames from all the APs <NUM>, <NUM> and <NUM>. The APs broadcast the MU-TM capability indication in the management frames such as beacon frames. If the station <NUM> receives the management frames of APs and knows that MU-TM are supported, it may perform the MU-TM based message exchanges with the APs <NUM>, <NUM> and <NUM> for the geo-positioning. The station <NUM> may also acquire the local map, floorplan and other geographic reference information from APs <NUM>, <NUM> and <NUM> so that it can determine its relative position to those reference points.

<FIG> illustrates an example of message exchanges of the MU-TM protocol. In this example, the timing measurement for geo-positioning involves one initiating station (iSTA), and three responding stations (rSTA1), (rSTA2) and (rSTA3). The responding stations could be Access Points (APs) or other stations which could provide references of geo-location for the iSTA to determine its position from MU-TM measurements.

MU-TM protocol message exchanges may consist of two phases:.

During the MU-TM preparation and measurement phases, the responding stations rSTA1, rSTA2 and rSTA3 may use the timing reference transmitted in iSTA for fine timing synchronization. The detail of an exemplary MU-TM message exchanges is as follows:.

Similarly, iSTA can calculate the RTD between iSTA and rSTA2, iSTA and rSTA3 respectively: <MAT> and <MAT>.

The iSTA may stop sending further MU-TM attempt if the difference between RTD1(n) and RTD1(n-<NUM>), RTD2(n) and RTD2(n-<NUM>) and RTD3(n) and RTD3(n-<NUM>) are less than a threshold. In other embodiments, the differences may be compared to distinct thresholds. The iSTA may optionally send the MU-TM report including its location information to the associated station.

<FIG> illustrates an example of MU-TM message exchange from the time domain point of view. As shown therein, the steps in the time-domain include:.

The transmission time of MU-TM Request or Response is determined by the transmission rate the message size. The fixed time delay Td should be set to the value greater than the maximum propagation delay between the initiating station and any responding station so that two consecutive transmissions of MU-TM Responses would not collide each other in the time domain. For example, for coverage of <NUM> from the iSTA, the Td could be set to <NUM>.

In some embodiments, the iSTA may stop sending further MU-TM attempt if the difference between two consecutive RTD measurements are less than the given threshold. The iSTA may calculate its position to the reference stations based on the timing measurement results, or send the timing measurement report to a location determination server through the AP which it associates with. The location server will then calculate the location information of the iSTA and send the information back.

In some embodiments, the iSTA may explicitly terminate the MU-TM measurement phase via sending a CF-End frame once the timing measurement completes or implicitly terminate via MU-TM OP time-out.

In some embodiments, to support the multi-user timing measurement mechanism, serval MU-TM messages are needed. To that end, an MU-TM capable responding station (e.g., AP) should broadcast the MU-TM support indication so that an MU-TM initiating station could easily identify and perform MU-TM based timing measurement with it. An MU-TM capable station may include the MU-TM support indication in the BSS Capability or the Neighbour BSS report. <FIG> shows examples of MU-TM support indication in the HE Capability IE and Neighbour BSS report IE, respectively.

<FIG> illustrate examples of MU-TM message formats which can be used for either initial MU-TM Request/Response in the preparation phase or the MU-TM Request/Response in the timing measurement phase. The MU-TM Request can be a Null Data Packet Announcement (NDPA) like frame and the MU-TM Response can be a Null Data Packet (NDP) type of frame in the MU-TM measurement phase.

The MU-TM Request contains fields shown in <FIG>, which include:.

The MU-TM Response contains fields shown in <FIG>, which include:.

During the MU-TM measurement phase, an rSTA may send an NDP based MU-TM Response in an MU-TM attempt except for the last one. If an NDP based MU-TM Response is sent, no MAC frame is attached to the NDP based MU-TM Response. In the last MU-TM attempt, the rSTA shall include in the MU-TM Response the ToA (for example ToA1 for rSTA1) and ToD (for example, ToD1 for rSTA1) averaged with the ToA and ToD values in previous MU-TM attempts. Therefore the iSTA can apply the averaged ToA1 and ToD1 to calculate the RTD between iSTA and rSTA1.

After the MU-TM OP is established among the iSTA and multiple rSTAs, the iSTA may start the first MU-TM attempt with rSTAs. It may repeat the attempt multiple times to improve the timing measurement accuracy. As the information in the MU-TM Request would be same or similar in every MU-TM attempt, the iSTA may simplify the MU-TM Request to further improve MU-TM protocol performance.

In some embodiments, if the iSTA performs the MU-TM message exchanges with the same rSTAs as the initial MU-TM Request and uses similar parameters like RUs and ERTs, the iSTA can set the Number of Users to "<NUM>" (or other special value) to instruct rSTAs to derive the parameters from the setting in the previous MU-TM Request, and not include an individual User Info fields in this MU-TM Request. The rSTAs shall derive RUs, ERTs and other parameters from the previous MU-TM Request.

For example, ERT1(i) for the ith MU-TM measurement can be derived as <MAT>.

Here, ERT1(i-<NUM>) are either included in the (i-<NUM>) MU-TM Request or further derived from previous request or the initial MU-TM Request. Similarly, ERT2(i) and ERT3(i) for ith MU-TM measurement attempt can be derived as <MAT> and <MAT>.

<FIG> shows the wireless communication method <NUM>. The method <NUM> includes, at step <NUM>, transmitting, by a communication apparatus, a timing request to a subset of a plurality of network devices, where the timing request comprises a respective expected response time for each of the subset of the plurality of network devices. In some embodiments, the timing request identifies a transmission resource associated with each of the subset of the plurality of network devices. The communication apparatus may be, for example, a smartphone, a laptop, a tablet, an Internet of Things (IoT) device, or another hardware platform capable of wireless communication.

The method <NUM> includes, at step <NUM>, receiving, at a plurality of times, a plurality of timing measurements from each of the subset of the plurality of network devices, where each of the plurality of times is based on the corresponding expected response time, and the plurality of timing measurements comprises a respective time of arrival (ToA) timestamp and a respective time of departure (ToD) timestamp. For example, the frame formats shown in <FIG> may be used for the MU-TM request and the MU-TM response, respectively.

The method <NUM> includes, at step <NUM>, determining a location information of the communication apparatus based on an estimate of a round trip delay that is computed using a difference of the respective ToA and ToD timestamps from the plurality of timing measurements. Some example equations for the location determination are described in the present document.

In some embodiments, the method <NUM> further includes transmitting, to the plurality of network devices, a plurality of initial timing requests on a plurality of frequency channels, and receiving a plurality of initial timing responses from the subset of the plurality of network devices on a respective frequency channel of the plurality of frequency channels, as described in the context of the MU-TM preparation phase. In an example, the plurality of initial timing requests is transmitted in an identical timeslot.

In some embodiments, the method <NUM> further includes repeating steps <NUM> and <NUM> a number of times, where a ToA timestamp and a ToD timestamp is received each of the number of times from each of the subset of the plurality of network devices, and refining the estimate of the round trip delay based on a plurality of the ToA timestamps and ToD timestamps.

In some embodiments, the method <NUM> further includes transmitting, after the steps <NUM> and <NUM> are repeated the number of times, a termination message.

In some embodiments, the method <NUM> further includes transmitting a report comprising the location information of the communication apparatus to the subset of the plurality of network devices.

<FIG> shows an example of a wireless communication method, in accordance with some embodiments of the presently disclosed technology. This example includes some features and/or steps that are similar to those shown in <FIG>, and described above. At least some of these features and/or components may not be separately described in this section. The method <NUM> includes, at step <NUM>, transmitting a plurality of initial timing requests to a plurality of network devices.

The method <NUM> includes, at step <NUM>, receiving a plurality of initial timing responses from a subset of the plurality of network devices.

The method <NUM> includes, at step <NUM>, transmitting a timing request to the subset of the plurality of network devices, where the timing request identifies transmission resources to be used by each of the subset of the plurality of network devices.

The method <NUM> includes, at step <NUM>, receiving, over the respective transmission resources, a plurality of timing measurements from the subset of the plurality of network devices, where the plurality of timing measurements comprises a respective ToA timestamp and a respective ToD timestamp.

The method <NUM> includes, at step <NUM>, determining a location information of the apparatus based on an estimate of a round trip delay that is computed using a difference of the respective ToA and ToD timestamps from the plurality of timing measurements.

<FIG> shows an example of a wireless communication method, in accordance with some embodiments of the presently disclosed technology. This example includes some features and/or steps that are similar to those shown in <FIG> and <FIG>, and described above. At least some of these features and/or components may not be separately described in this section. The method <NUM> includes, at step <NUM>, transmitting, to a group of network devices, a timing request soliciting time measurement responses, the timing request including information for receiving the time measurement responses in a collision-free manner. In some embodiments, the collision-free manner comprises time-division multiplexing (TDM). In some embodiments, the collision-free manner comprises frequency-domain multiplexing (FDM). In some embodiments, other collision-free communication techniques such as code division multiplexing may be used.

The method <NUM> includes, at step <NUM>, receiving, in the collision-free manner, the timing measurement responses from at least some network devices from the group, where each timing measurement response includes a first field indicative of a reception time at which a corresponding network device received the timing request and a second field indicative of response time at which the corresponding network device transmitted its timing measurement response.

The method <NUM> includes, at step <NUM>, determining a location of the communication apparatus based on the timing measurement responses.

In some embodiments, the method <NUM> further includes repeating steps <NUM> and <NUM> a number of times, where the first and second fields are received the number of times from the at least some network devices from the group, and refining the location of the communication apparatus based on the first and second fields that were received the number of times.

In some embodiments, the method <NUM> further includes transmitting, to the group of network devices, a report comprising the location of the communication apparatus.

<FIG> shows an example of a wireless communication method, in accordance with some embodiments of the presently disclosed technology. This example includes some features and/or steps that are similar to those shown in <FIG>, <FIG> and <FIG>, and described above. At least some of these features and/or components may not be separately described in this section. The method <NUM> includes, at step <NUM>, receiving, from a communication apparatus, a timing request comprising a first time of departure (ToD), an expected response time (ERT), and an identification of a transmission resource.

The method <NUM> includes, at step <NUM>, transmitting, at a calculated time and over the transmission resource, a timing measurement that comprises a time of arrival (ToA) timestamp and a second ToD timestamp, where the ToA timestamp corresponds to when the timing request was received, where the second ToD timestamp corresponds to the calculated time, and where the second ToD is equal to a sum of the ToA timestamp and the ERT.

In yet another exemplary aspect, another method based on the embodiments of the disclosed technology enable a wireless system to implement a timing measurement protocol between a wireless station and multiple wireless reference stations for geographic-positioning the wireless station, and may include transmitting a timing measurement request to a plurality of wireless reference stations simultaneously and receiving their timing measurement responses sequentially.

In yet another exemplary aspect, another method based on the embodiments of the disclosed technology enable a wireless system to initiate the timing measurement with a plurality of wireless reference stations, and to subsequently perform a multi-user timing measurement preparation phase and a timing measurement phase.

In yet another exemplary aspect, another method based on the embodiments of the disclosed technology enable a wireless system to identify MU-TM-capable wireless reference stations, and set up the timing measurement period with those wireless reference stations in the multi-user timing measurement preparation phase. The method may include, in the initial multi-user timing measurement, transmitting a request that includes the identified wireless reference stations, allocated resource units and expected response time for transmitting the timing measurement responses from a plurality of wireless reference stations. A plurality of wireless reference stations transmit the timing measurement responses over the allocated resource unit(s) at the specified time slot.

In yet another exemplary aspect, another method based on the embodiments of the disclosed technology enable a wireless system to instruct a plurality of responding wireless reference stations to transmit a timing measurement response at the specified time so that a plurality of timing measurement responses from a plurality of wireless reference stations can be distributed in time domain to avoid signal collision at the receiving side.

In yet another exemplary aspect, another method based on the embodiments of the disclosed technology enable a wireless system to repeat the same multi-user timing measurement procedure with the same plurality of wireless reference stations. With a plurality of timing measurements from a plurality of wireless reference stations, the timing measurement initiating wireless station can improve the geographic-positioning accuracy progressively. The timing measurement initiating wireless station may stop the timing measurement procedure once the measurement result is satisfied.

<FIG> is a block diagram representation of a portion of a communication apparatus, in accordance with some embodiments of the presently disclosed technology. The apparatus <NUM> can include processor electronics <NUM> such as a microprocessor that implements one or more of the techniques presented in this document. The apparatus <NUM> can include transceiver electronics <NUM> to send and/or receive wireless signals over one or more communication interfaces such as antenna(s) <NUM>. The apparatus <NUM> can include other communication interfaces for transmitting and receiving data. Apparatus <NUM> can include one or more memories (not explicitly shown) configured to store information such as data and/or instructions. In some implementations, the processor electronics <NUM> can include at least a portion of the transceiver electronics <NUM>. In some embodiments, at least some of the disclosed techniques, modules or functions are implemented using the apparatus <NUM>.

It is intended that the specification, together with the drawings, be considered exemplary only, where exemplary means an example and, unless otherwise stated, does not imply an ideal or a preferred embodiment. As used herein, the use of "or" is intended to include "and/or", unless the context clearly indicates otherwise.

Claim 1:
A method for wireless communication, comprising:
a) transmitting (<NUM>), by a communication apparatus (<NUM>), a timing request to a subset of a plurality of network devices, wherein the timing request comprises a respective expected response time for each of the subset of the plurality of network devices, and wherein the expected response time corresponds to a transmission time of a timing measurement that is received from the corresponding network device of the plurality of network devices;
b) receiving (<NUM>), at a plurality of times, a plurality of timing measurements from each of the subset of the plurality of network devices, wherein each of the plurality of times is based on the corresponding expected response time, and the plurality of timing measurements comprises a respective time of arrival, ToA, timestamp and a respective time of departure, ToD, timestamp;
c) determining (<NUM>) a location information of the communication apparatus (<NUM>) based on an estimate of a round trip delay that is computed using a difference of the respective ToA and ToD timestamps from the plurality of timing measurements;
repeating steps a) and b) a number of times, wherein a ToA timestamp and a ToD timestamp is received each of the number of times from each of the subset of the plurality of network devices, and wherein the round trip delay is computed for each of the number of times for each of the subset of the plurality of network devices; and
ceasing repeating steps a) and b) when a difference between consecutive round trip delays is less than a threshold.