WO2021081657A1

WO2021081657A1 - User detection using radio-frequency (rf) signals

Info

Publication number: WO2021081657A1
Application number: PCT/CA2020/051465
Authority: WO
Inventors: Karim ISMAIL; Amir GHODS
Original assignee: Carleton University
Priority date: 2019-11-01
Filing date: 2020-10-30
Publication date: 2021-05-06

Abstract

A user of a computing device may be detected, and their location determined, based on radio frequency signals transmitted by the computing device. The RF signals may be for example Bluetooth or Wi-Fi signals that are received by a localization device. The localization device comprises a plurality of RF receivers for receiving the transmitted RF signals. The RF receivers are synchronized by a single local master clock signal, allowing the localization device to determine the computing device's location based on a time difference of arrival of the transmitted signal at the receivers.

Description

USER DETECTION USING RADIO-FREQUENCY (RF) SIGNALS

TECHNICAL FIELD

[0001] The current disclosure relates to detection of users using RF signals, and in particular to determining user locations using RF signals.

BACKGROUND

[0002] The localisation of a user, or more accurately a computing device of a user, can be done by trilateration of RF signals transmitted by the user’s device, or by RF signals received at the device and transmitted by different transmitters. For example, Bluetooth beacons transmitted from known locations can be received by a device and used to determine the device’s location relative to known locations of the transmitters. One method of determining a distance from the device to the transmitters is to use the Received Signal Strength Indicator (RSSI), however, the location determination using RSSI values is typically inaccurate.

[0003] Another technique to determine a device’s location is to use time-of-flight (TOF) measurements, which uses the time of flight of a signal between the device and separate transmitters, or receivers, in order to determine the device’s locations. While TOF plus triangulation can provide an accurate location, it requires precise clock synchronization between all of the transmitters and receivers in order to accurately determine the location.

[0004] Additional, alternative and/or improved systems, devices and techniques for determining a location of a user is desirable.

SUMMARY

[0005] In accordance with the present disclosure there is provided a location determination device comprising: a master clock providing a synchronization signal; three or more radio frequency (RF) receivers each synchronized to the synchronization signal of the master clock and outputting a received signal; signal processing functionality for identifying a transmission signal within each of the received signals; location determination functionality for performing multilateration using a time difference of arrival (TDOA) between arrival times of the identified signals within each of the received signals to estimate a location of a user device that transmitted the transmission signal.

[0006] In a further embodiment of the location determination device, the signal processing functionality comprises functionality for identifying and rejecting reflections of the transmission signal within each of the received signals.

[0007] In a further embodiment of the location determination device, the transmission signal transmitted by the device comprises a unique identifier associated with the user device

[0008] In a further embodiment of the location determination device, the transmission signal transmitted by the device further comprises an indication of a transportation mode of the user device.

[0009] In a further embodiment of the location determination device, the transportation mode is selected from: walking; running; biking; and driving.

[0010] In a further embodiment of the location determination device, the device further comprises a communication radio for transmitting an indication of the estimated location of the user device.

[0011 ] In a further embodiment of the location determination device, the communication radio transmits the indication of the estimated location to one or more of: the user device; one or more additional user devices; and a remote server.

[0012] In a further embodiment of the location determination device, each of the three or more RF receivers comprise a Bluetooth receiver or a Wi-Fi receiver.

[0013] In a further embodiment of the location determination device, the three or more RF receivers comprise one of: four RF receivers; five RF receivers; six RF receivers; seven RF receivers; eight RF receivers; nine RF receivers; and ten RF receivers. [0014] In a further embodiment of the location determination device, the three or more RF receivers comprise four RF receivers.

[0015] In accordance with the present disclosure there is further provided a user device comprising: a memory storing instructions; and a processor for executing the instructions stored in the memory, which when executed configure the user device to: determine a transportation mode of the user device; set a transmission frequency based on the determined transportation mode; periodically transmit a radio frequency (RF) transmission signal including a unique identifier associated with the user device; receive location information of one or more remote devices; and provide an alert to a user of the user device based on the received location information.

[0016] In a further embodiment of the user device, the instructions stored in memory, which when executed by the processor further configure the user device to: determine a predicted path of each of the one or more remote devices based on the received location information; determine a possible collision with the user of the user device based on the predicted paths of the one or more remote devices, wherein the alert is provided when a possible collision is determined.

[0017] In a further embodiment of the user device, the received location information comprises an indication of a possible collision between the user of the user device and at least one of the one or more remote devices, wherein the alert provides an alert to the user about the possible collision.

[0018] In a further embodiment of the user device, the received location information comprises predicted paths of each of the one or more remote devices and wherein the instructions stored in memory, which when executed by the processor further configure the user device to: determine a possible collision with the user of the user device based on the predicted paths of the one or more remote devices, wherein the alert is provided when a possible collision is determined.

[0019] In accordance with the present disclosure there is further provided a location server comprising: a memory storing instructions; and a processor for executing the instructions stored in the memory, which when executed configure the user device to: receive location information of a plurality of remote devices; determine a predicted path of each of the plurality of remote devices based on the received location information; determine possible collisions between the plurality of remote devices based on the determined paths; and when a possible collision is determined, send an alert to the remote devices involved in the determined possible collision.

[0020] In accordance with the present disclosure there is further provided a system for locating users comprising: a plurality of location determination devices as described above; and a plurality of user devices as described above.

[0021] In a further embodiment, the system further comprises one or more location servers as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] [0009] Further features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0023] FIG. 1 depicts a system for user detection using RF signals;

[0024] FIG. 2 depicts a device for user detection using RF signals;

[0025] FIG. 3 depicts a method of user detection using RF signals; and [0026] FIG. 4 depicts a method of providing alerts based on user locations.

DETAILED DESCRIPTION

[0027] The location of computing devices that are capable of emitting radio frequency (RF) signals, which may include for example Bluetooth signals and/or Wi-Fi signals, can be determined by a locating device. The locating device includes at least three RF receivers that are all synchronized to a common clock signal of the locating device.

Each of the RF receivers will receive a transmitted signal at different times based on the location of the transmitting device. Trilateration, or multilateration when additional receivers are used, may be used to determine the transmitting device’s location relative to the location device using the Time Difference of Arrival (TDOA) of the signals. The location devices may be placed in known locations, such as at specific locations along a roadside, allowing the actual location of the devices to be determined. Additionally or alternatively, the locating devices may be moveable, such as by mounting to a vehicle, allowing the determination of the location of devices relative to, for example, the vehicle. The location of devices may be tracked over time to allow a possible path of the device to be determined, which may be used to, for example, determine possible collisions between the devices, users, vehicles, etc. Additionally, or alternatively, the information may be used to provide information about devices in the vicinity of the location device, which in turn could be used to control traffic lights, cross walks, etc. Although various example uses of the location information are described, it will be appreciated that other applications are possible.

[0028] In contrast to location determination techniques that are based on time of flight techniques which require precise timing synchronization by all of the transmitting and receiving devices, the location device described herein uses time difference of arrival between a plurality of receivers within the same device, which allows all of the receivers to be synchronized to a single clock signal local to the location device. Accordingly, the location devices can be easily deployed in different locations.

[0029] As described in further detail below, the technology comprises a sensor arrangement that may be [i] deployed on the roadside or [ii] deployed on a mobile platform such as vehicles, autonomous vehicles. Each sensor arrangement may detect transmitted RF signals such as [i] Wi-Fi and/or [ii] Bluetooth signals, emitted from electronic devices such as cell phones carried by users in the transmission range of the sensor arrangements deployed for example along the roadside. The devices may transmit the signals either [i] through normal usage of the device or [ii] with an installed application for helping in locating the device such as a Location Safety App. The sensor arrangement makes use a Time Difference of Arrival (TDA) technology to determine the location of the signal source, i.e. the transmitting device. Three or more receivers are located within the sensor arrangement with associated antennas placed at a known distances from each other receive. An RF signal ping from the mobile device is received at each antenna/receiver at different times and a hyperbolic trilateration, or multilateration, method determines the position of the signal source.

[0030] Although locations of devices may be determined based on received RF transmissions that are transmitted as a result of the normal operation of the device, a Location Safety App may be used on the mobile device to actively send RF ‘pings’ to facilitate the precise locating of the device. The Location Safety App may activate the periodic RF pinging when it detects motion using for example onboard accelerometers. The motion may be classified into various modes of transportation such as [i] walking,

[ii] biking, or [iii] vehicular usage. The Location Safety App may send signal pings to the sensor arrangement for localization and determination of the travel mode (i.e. pedestrian and cyclist). The sensor arrangement receives the signal and can [i] share the position of the individual to other vehicles through DSRC or 5G communication, [ii] share the information with infrastructure control components such traffic signals, or [iii] utilize this information to avoid collisions involving the smartphone carrying party.

[0031] In addition to possible fixed deployments such as at known locations along a roadside, the sensor arrangement can also operate in a mobile mode in which it can be installed in or on a moving vehicle and the position of the signal source is determined relative to the vehicle position.

[0032] The sensor arrangements comprises signal processing functionality to process received signals from the plurality of receivers and eliminate or reduce the effect of random delay and multi-path of the transmitted signal. The three or more receivers report the reception of the signal from the mobile device with a deterministic delay and the system should be able to determine if the received signal is a reflected signal. Temporal measurement accuracy of the received transmitted signals should be at nanosecond precision or less.

[0033] As opposed to time-of-flight methods, the use of TDA does not require complicated time synchronization between receivers nor an application running on the source device where the signal is transmitted from to synchronize the transmission of the signal. In addition to not requiring complex synchronization, the sensor arrangement can locate the devices using relatively low-power Wi-Fi or Bluetooth pings or other RF transmissions sent from devices.

[0034] FIG. 1 depicts a system for user detection using RF signals. The system 100 comprises a number of locating devices 102a, 102b (referred to collectively as locating devices 102). Each of the locating devices 102 have at least three RF receivers and associated antennas. Although depicted as having three RF receivers in FIG. 1 , it is possible to incorporate additional RF receivers so that each location device 102 has four, five, six, seven, eight, nine, ten or more RF receivers. Each of the locating devices 102 is able to locate the source of a signals received at the receivers using Time Difference of Arrival (TDA) and trilateration. The use of three RF receivers in the locating device 102 may provide adequate or acceptable location accuracy, however the location accuracy may be improved with the use of additional RF receivers. Each of the locating devices 102 may be located at fixed known locations, or may be mobile, such as being mounted on a vehicle.

[0035] A number of devices 104a, 104b, 104c (referred to collectively as devices 104) may each transmit RF signals, such as Wi-Fi or Bluetooth pings that are detected by one or more of the locating devices 102. The devices 104 may be mobile devices carried by users 106a, 106b or may be devices 104c associated with a vehicle 108 or other means of transportation. Each of the locating devices 102 may receive signal from a plurality of different devices and locate each of the different devices. Each of the devices 104 may be configured to provide various functionality 110, including for example localization functionality 112. The localization functionality may provide various functionality including detecting a mode of transportation of the device. As depicted, the devices 104 may be carried by a person 106a that is walking, or possibly jogging or running, by a person that is riding a bicycle 106b or in a vehicle. The localization functionality 112 may determine the mode of transportation and communicate the mode of transportation to other devices, including for example the location devices 102. Additionally or alternatively, the determined mode of transportation may be used to set the frequency at which the device transmits pings.

The localization functionality 112 may provide further functionality including for example determining paths of devices based on location information from the locating devices 102. The paths can be displayed to the user, or may be processed to determine possible collisions. Additionally or alternatively, the localization functionality 112 may receive alerts from other devices for providing to the user of the device.

[0036] The users’ devices 104 as well as the locating devices 102 may communicate with each other, possibly directly, or through a cellular or other wireless infrastructure 114. The devices 102 and 104 may communicate with one or more remote servers 116 over a network 118. The remote servers 118 may provide various functionality including for example, tracking the devices 104. The device tracking may be used for various purposes including controlling of other devices such as traffic lights, doors, digital signs etc. Further, the information of the tracked devices may be used for tracking usage patterns of infrastructure etc.

[0037] FIG. 2 depicts a device for user detection using RF signals. The location device 200 may be used as any of the location devices 102. The device 200 may be positioned in a known location and will detect a transmitted RF signal 201 . The transmitted signal 201 is received by three or more antennas 202a, 202b, 202c (referred to collectively as antennas 202) each of which is connected to a respective receiver 204a, 204b, 204c (referred to collectively as receivers 204). The receivers 204 may be for example Bluetooth or Wi-Fi receivers or transceivers, although other RF technologies may be used. The device 200 further includes a local master clock 206 that provides a clock signal 208 to each of the receivers 204. Accordingly, each of the receivers are tightly synchronized with each other and so the relative time that the transmitted signal 201 is received at each receiver can be determined. The signals 210a, 210b, 210c from the receivers 204 are provided to signal measurement functionality 212 for processing the signals 210. The signal measurement functionality 212 may detect the transmitted signals, i.e. the Bluetooth or Wi-Fi ping signals, within the received signals. As depicted schematically by the different signals 210a, 210b, 210c the transmitted signal is received at the different receivers at different times. The processed signals 214a, 214b, 214c may be provided to other signal processing functionality 216 that can verify the signals and reject reflections of the transmitted signal within the received signals. Once the received signals have been processed to identify the locating ping and remove any reflections, multilateration functionality 218 may determine the location of the signal source using the time difference of arrival of the transmitted signal received at each of the receivers.

[0038] The determined location may be provided to localization processing functionality 220. The functionality 220 may, for example, track the location of devices over time.

The functionality 220 may also determine if devices are in close proximity to each other or on possibly colliding paths. Alerts may be transmitted to one or more devices providing information about devices in their vicinity, or possibly on a colliding path. The alerts or other information may be transmitted by one or more wired or wireless radios 222. The radio may communicate with other devices such as user devices 104, locating devices 102, remote servers 118 or other devices including for example traffic lights, cross walk signals, etc.

[0039] FIG. 3 depicts a method of user detection using RF signals. The method 300 depicts functionality provided by a user device such as one of the user devices 104 and a location device such as one of the location devices 104. The user device may detect motion of the device and determine a transportation mode of the device (302). The transportation mode may be selected from a set of transportation modes such as walking, running, biking or driving. The transportation mode may be used to set a beacon frequency (304). For example, beacons may be transmitted more frequently when driving compared to walking. The user device may then transmit locating beacons (306). The locating beacons may be transmitted for example by a Bluetooth or Wi-Fi radio of the user device. The locating beacons may include information identifying the user device in order to allow tracking of the device across time. Additionally or alternatively the beacon may include information such as the determined transportation mode, and/or additional information. The transmitted beacon is then detected by each of the receivers of the locating device (308). The received signals from each of the receivers is processed in order to determine location information (310). The location information may include for example the location of the device and/or an estimated path of the device. The location information may include the location information of the device as well as other devices possibly in the vicinity of the device. The location information may be transmitted (312) to other devices including for example one or more user devices, one or more locating devices and/or one or more remote servers. The location information may be received (314) at the user device and processed (316). The location information may be processed to identify possible collisions or other conditions requiring notifying a user. A location notification may be provided to the user (318), such as for example alerting a user about the presence of other devices in their vicinity. The location notification may be a visual notification and audio notification, and/or a haptic notification.

FIG. 4 depicts a method of providing alerts based on user locations. The method 400 depicts functionality that may be provided by a location device and a remote server.

The location device may determine the location of devices based on received wireless signals. The location information may be transmitted (401 ) by the location device and received at the remote location (404). The location information may provide the location of one or more devices. The remote server may process the information in various ways. For example, the location information of different devices may be used to determine paths of the different devices (406) and using the predicted paths, detect possible collisions between devices (408). Based on possible collisions, the remote server may determine possible alerts (410). For example, different devices may be associated with different alerts, that is devices for a user walking may differ from a user driving a car. For example, if two users are walking on a collision course, no alert may be needed as it is assumed the two people will adjust their path to avoid each other. In contrast, if a person driving in a car and a person walking are on a collision course they may both be alerted of a possible collision. Other ways of determining alerts are possible, including based on user preferences, determined locations of devices, determined paths of devices as well as possibly other information such as weather conditions, historical data, etc. Once the alerts are determined, they may be transmitted (412). The method 400 depicts the transmitted alerts being received at the location device and then provided to a user (414). The notification may be broadcast from the location device to all user devices in the vicinity, or may be sent to individual user devices. Additionally or alternatively, the location server may be transmit the alerts to individual devices.

[0040] It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention. Although specific embodiments are described herein, it will be appreciated that modifications may be made to the embodiments without departing from the scope of the current teachings. Accordingly, the scope of the invention should not be limited by the specific embodiments set forth, but should be given the broadest interpretation consistent with the teachings of the description as a whole.

Claims

WHAT IS CLAIMED IS:

1. A location determination device comprising: a master clock providing a synchronization signal; three or more radio frequency (RF) receivers each synchronized to the synchronization signal of the master clock and outputting a received signal; signal processing functionality for identifying a transmission signal within each of the received signals; location determination functionality for performing multilateration using a time difference of arrival (TDOA) between arrival times of the identified signals within each of the received signals to estimate a location of a user device that transmitted the transmission signal.

2. The location determination device of claim 1 , wherein the signal processing functionality comprises functionality for identifying and rejecting reflections of the transmission signal within each of the received signals.

3. The location determination device of claim 1 or 2, wherein the transmission signal transmitted by the device comprises a unique identifier associated with the user device

4. The location determination device of claim 3, wherein the transmission signal transmitted by the device further comprises an indication of a transportation mode of the user device.

5. The location determination device of claim 4, wherein the transportation mode is selected from: walking; running; biking; and driving.

6. The location determination device of any one of claims 1 to 5, further comprising a communication radio for transmitting an indication of the estimated location of the user device.

7. The location determination device of claim 6, wherein the communication radio transmits the indication of the estimated location to one or more of: the user device; one or more additional user devices; and a remote server.

8. The location determination device of any one of claims 1 to 7, wherein each of the three or more RF receivers comprise a Bluetooth receiver or a Wi-Fi receiver.

9. The location determination device of any one of claims 1 to 8, wherein the three or more RF receivers comprise one of: four RF receivers; five RF receivers; six RF receivers; seven RF receivers; eight RF receivers; nine RF receivers; and ten RF receivers.

10. The location determination device of claim 9, wherein the three or more RF receivers comprise four RF receivers.

11. A user device comprising: a memory storing instructions; and a processor for executing the instructions stored in the memory, which when executed configure the user device to: determine a transportation mode of the user device; set a transmission frequency based on the determined transportation mode; periodically transmit a radio frequency (RF) transmission signal including a unique identifier associated with the user device; receive location information of one or more remote devices; and provide an alert to a user of the user device based on the received location information.

12. The user device of claim 11 , wherein the instructions stored in memory, which when executed by the processor further configure the user device to: determine a predicted path of each of the one or more remote devices based on the received location information; determine a possible collision with the user of the user device based on the predicted paths of the one or more remote devices, wherein the alert is provided when a possible collision is determined.

13. The user device of claim 11 or 12, wherein the received location information comprises an indication of a possible collision between the user of the user device and at least one of the one or more remote devices, wherein the alert provides an alert to the user about the possible collision.

14. The user device of any one of claims 11 to 13, wherein the received location information comprises predicted paths of each of the one or more remote devices and wherein the instructions stored in memory, which when executed by the processor further configure the user device to: determine a possible collision with the user of the user device based on the predicted paths of the one or more remote devices, wherein the alert is provided when a possible collision is determined.

15. A location server comprising: a memory storing instructions; and a processor for executing the instructions stored in the memory, which when executed configure the user device to: receive location information of a plurality of remote devices; determine a predicted path of each of the plurality of remote devices based on the received location information; determine possible collisions between the plurality of remote devices based on the determined paths; and when a possible collision is determined, send an alert to the remote devices involved in the determined possible collision.

16. A system for locating users comprising: a plurality of location determination devices according to any one of claims 1 to 10; and a plurality of user devices according to any one of claims 11 to 14.

17. The system of claim 16, further comprising one or more location servers according to claim 15.