Backscattering device ranging and positioning

Abstract

A method and devices for backscattering device (BD) ranging and positioning are disclosed. According to one aspect, a method includes receiving a backscattered fine time measurement (BFTM) frame from a second device and a reflected BFTM frame from the BD. The reflected BFTM frame may be one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD (25) from the second device (22)A time difference of arrival between the BFTM frame received from the second device and the reflected BFTM frame received from the BD is determined. The method also includes determining a position of the BD based at least in part on triangularization using positions of the first device and the second device as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first and second distances.

Description

[0001] BACKSCATTERING DEVICE RANGING AND POSITIONING

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications, and in particular, to backscattering device ranging and positioning.

[0004] BACKGROUND

[0005] The Institute of Electrical and Electronic Engineers (IEEE) has developed and continues to develop standards for other types of wireless communication networks, including Wireless Local Area Networks (WLANs), including Wireless Fidelity (WiFi) networks and Bluetooth networks. WLANS include wireless communication between access points (APs) and non-access point stations (non-AP STAs). Such IEEE standards include IEEE 802.1 la / b / g / n / ac / ax and IEEE 802.15.

[0006] The Fine Time Measurement Procedure

[0007] The fine time measurement (FTM) protocol is used to estimate time of flight (ToF). FTM was first presented in IEEE 802.1 Imc. In the FTM protocol, the ToF is used to estimate the distance between two nodes. The distance may then be used by several nodes to estimate the position of one node using triangulation. The FTM exchange protocol may be initiated by any STA.

[0008] The principle in FTM is that STAs send FTM frames back and forth between each other. The FTM frames have two key technological features, timestamps and preambles. The preambles (short training field (STF), long training field (LTF)) are used for time synchronization and determination of when the frame is received and the timestamps are used to derive the ToF.

[0009] Ambient Powered Devices (AMP)

[0010] The AMP topic interest group (TIG) in IEEE 802.11 is investigating the possibility of standardizing medium access control (MAC) and PHY layer for AMP devices. One type of AMP devices are called backscatter devices (BD) and function by reflecting an illuminated radio signal. Information may be carried in the reflection by applying a modulation. The reflection may be frequency shifted compared to the illuminating signal. An example of a backscattered setup is shown in FIG. 1.

[0011] Referring to FIG. 1, the STA acts as an “illuminator” to the BD such that it may send data to the AP. In general, assume that the STA and the AP may both send data immediately to the BD. Furthermore, typically prior to any reception or transmission by the BD, an energizing signal needs to be transmitted to energize the circuitry in the BD. This may either be sent by an AP or a STA. The illuminating signal is most commonly sent by the STA and received by the AP, but the opposite is also possible. Furthermore, if a STA (or AP) is full duplex (or sub band full duplex) capable, it may act both as the device sending the illuminating signal and recipient of the reflected signal simultaneously.

[0012] Sub-band full duplex is a communication scheme where a single frequency band is partitioned into sub-bands for down-link (DL) and up-link (UL) transmissions, and both can take place simultaneously. The purpose is to improve throughput, coverage and reduce latency of the UL communication by allowing UL reception during DL transmission.

[0013] A problem with the existing FTM protocol is that it requires a ping-pong like behavior of frames being sent between two STAs, where the frames are populated with some timestamps. The BD is not as capable as a STA and cannot carry out the FTM protocol.

[0014] SUMMARY

[0015] Some embodiments advantageously provide methods and devices for backscattering device ranging and positioning.

[0016] A protocol and method are introduced to perform ranging of BDs. It assumes positional knowledge of the illuminating and receiving device (typically an AP and a STA, or two APs). The APs and STAs may obtain this knowledge through, for example, FTM and triangularization.

[0017] Using the protocols disclosed herein, an ellipsoid may be derived with the position of the AP and STA being the focal points, and the BD residing somewhere on the surface of the ellipsoid. By using the protocol between multiple devices, triangularization using ellipsoids (instead of spheres as normal triangularization) may be used to determine the position of the BD.

[0018] According to one aspect, a method in a first device for performing ranging of a backscatter device, BD, is provided. The method includes receiving a backscattered fine time measurement, BFTM, frame from a second device and a reflected BFTM frame from the BD, the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD from the second device. The method also includes determining a difference in time of arrival at the first device between the BFTM frame received from the second device and the reflected BFTM frame received from the BD. The method further includes determining a sum of a first distance between the first device and the second device and a second distance between the second device and the BD based at least in part on the difference in time of arrival. The method also includes determining a position of the BD based at least in part on triangularization using positions of the first device and the second device as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first distance and the second distance.

[0019] According to this aspect, in some embodiments, the second device is collocated with the first device. In some embodiments, the first device and second device share a duplexing capability. In some embodiments, the difference in time of arrival is based at least in part on one or more of a time measurement, a power measurement and an angle of arrival. In some embodiments, the method includes receiving a plurality of reflected BFTM frames from the BD, each reflected BFTM frame arriving at the BD from one of a plurality of second devices. In some embodiments, the position of the BD is determined as a point of intersection of a plurality of ellipsoids. In some embodiments, the method includes determining a position for each BD of a plurality of BDs based at least in part on reflected BFTM frames received from each BD of the plurality of BDs. In some embodiments, the reflected BFTM frame received from the plurality of BDs are shifted in frequency by different amounts to facilitate their separation at the first device. In some embodiments, the BFTM frame from the second device and the reflected BFTM frame are received in measurement bursts.

[0020] According to another aspect, a first device configured to perform ranging of a backscatter device, BD, is provided. The first device is configured to: receive a backscattered fine time measurement, BFTM, frame from a second device and a reflected BFTM frame from the BD, the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD from the second device. The first device is also configured to determine a difference in time of arrival at the first device between the BFTM frame received from the second device and the reflected BFTM frame received from the BD. The first device is further configured to determine a sum of a first distance between the first device and the second device and a second distance between the second device and the BD based at least in part on the difference in time of arrival. The first device is also configured to determine a position of the BD based at least in part on triangularization using positions of the first device and the second device as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first distance and the second distance.

[0021] According to this aspect, in some embodiments, the second device is collocated with the first device. In some embodiments, the first device and the second device share a duplexing capability. In some embodiments, the difference in time of arrival is based at least in part on one or more of a time measurement, a power measurement and an angle of arrival. In some embodiments, the first device is configured to receive a plurality of reflected BFTM frames from the BD, each reflected BFTM frame arriving at the BD from one of a plurality of second devices. In some embodiments, the position of the BD is determined as a point of intersection of a plurality of ellipsoids. In some embodiments, the first device is configured to determine a position for each BD of a plurality of BDs based at least in part on reflected BFTM frames received from each BD of the plurality of BDs. In some embodiments, the reflected BFTM frame received from the plurality of BDs are shifted in frequency by different amounts to facilitate their separation at the first device. In some embodiments, the BFTM frame from the second device and the reflected BFTM frame are received in measurement bursts.

[0022] According to yet another aspect, a method in a second device to perform ranging of a backscatter device, BD, is provided. The method includes receiving a request from a first device to transmit a backscattered fine time measurement, BFTM, frame to the BD. The method also includes energizing the BD. The method also includes transmitting the BFTM frame to the BD and to the first device.

[0023] According to this aspect, in some embodiments, the method includes sending a command to the BD indicating that a ranging session is to be performed. In some embodiments, the command includes an indication of an amount of frequency shift to be applied by the BD to the BFTM frame. In some embodiments, the request includes an indication of a frequency shift to be applied by the BD to the BFTM frame. In some embodiments, the first device and the second device are collocated. In some embodiments, the method includes illuminating a plurality of BDs with the BFTM frame.

[0024] According to another aspect, a second device configured to perform ranging of a backscatter device, BD, is provided. The second device is configured to receive a request from a first device to transmit a backscattered fine time measurement, BFTM, frame to the BD, energize the BD, and transmit the BFTM frame to the BD and to the first device.

[0025] According to this aspect, in some embodiments, the second device is further configured to send a command to the BD indicating that a ranging session is to be performed. In some embodiments, the command includes an indication of an amount of frequency shift to be applied by the BD to the BFTM frame. In some embodiments, the request includes indicates a frequency shift to be applied by the BD to the BFTM frame. In some embodiments, the first device and the second device are collocated. In some embodiments, the second device is further configured to illuminate a plurality of BDs with the BFTM frame.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0028] FIG. l is a diagram of a station (STA) illuminating a backscatter device (BD) that reflects the illuminating signal toward the access point (AP);

[0029] FIG. 2 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;

[0030] FIG. 3 is a block diagram of a network node in communication with a wireless device over a wireless connection according to some embodiments of the present disclosure;

[0031] FIG. 4 is a flowchart of an example process in a network node configured as an AP STA or non-AP STA for backscattering device ranging and positioning;

[0032] FIG. 5 is a flowchart of an example process in a wireless device configured as an AP STA or non-AP STA for backscattering device ranging and positioning;

[0033] FIG. 6 is a sequence diagram of an example ranging protocol according to principles disclosed herein;

[0034] FIG. 7 is a protocol represented as a time diagram according to principles disclosed herein;

[0035] FIG. 8 is a geometrical representation of one example scenario for applying principles disclosed herein; FIG. 9 shows an example ranging process that includes a backscattering device (BD) according to principles disclosed herein;

[0036] FIG. 10 shows an triangularization process using 2 STAs according to principles disclosed herein;

[0037] FIG. 11 shows another triangularization process using 2 AP-STAs according to principles disclosed herein;

[0038] FIG. 12 shows another triangularization process using 2 STAs and 2 AP-STAs according to principles disclosed herein;

[0039] FIG. 13 is an example protocol for simultaneous ranging of multiple BDs according to principles disclosed herein; and

[0040] FIG. 14 is an example topology for simultaneous ranging of multiple BDs according to principles disclosed herein.

[0041] DETAILED DESCRIPTION

[0042] Before describing example embodiments in detail, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to backscattering device ranging and positioning. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0043] As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. 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,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

[0044] In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections.

[0045] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. 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,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0046] The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of an access point (AP), non-AP station, base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), relay node, donor node controlling relay, transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

[0047] In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The WD herein may be any type of wireless device capable of communicating with a network node or another WD over radio signals, such as non-AP STA or AP STA. The WD may also be a radio communication device, target device, device to device (D2D) WD, machine type WD or WD capable of machine to machine communication (M2M), low-cost and / or low-complexity WD, a sensor equipped with WD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.

[0048] Note that although terminology from one particular wireless system, such as, for example, an IEEE 802.11 wireless system, may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

[0049] Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0051] Some embodiments are directed to backscattering device ranging and positioning. Returning to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 2 a schematic diagram of a communication system 10, according to an embodiment, such as an IEEE 802.11 communication system, which may comprise an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as wireless access points (AP) (also referred to as AP STAs 16), each wireless access points defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first wireless device (WD) 22a (also referred to as a non-AP STA) located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD is in the coverage area or where a sole WD is connecting to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include many more WDs 22 and network nodes 16.

[0052] Also, it is contemplated that a WD 22 may be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a WD 22 may have dual connectivity with a network node 16 that supports a Third Generation Partnership Project (3GPP) cellular wireless communication system. Note that in some embodiments, the network node 16 may be an AP STA or a non-AP STA. Also, in some embodiments, the wireless device 22 may be an AP STA or a non-AP STA.

[0053] A network node 16 may be configured to include a BFTM frame receiver 24 which may be configured to receive a backscattered fine time measurement, BFTM, frame from a second device and a reflected BFTM frame from a backscatter device (BD) 25, the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD from the second device. A wireless device 22 is configured to include a BFTM frame transmitter 26 which is configured to transmit a BFTM frame to the BD 25 and to another STA.

[0054] Example implementations, in accordance with an embodiment, of the WD 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 3.

[0055] The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the WD 22. The hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a WD 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves. For example, the radio interface 20of the network node 16 may include the BFTM frame receiver 24 which may be configured as described herein.

[0056] In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and / or read from) the memory 40, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read- Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read- Only Memory).

[0057] Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16. Processor 38 corresponds to one or more processors 38 for performing network node 16 functions described herein. The memory 40 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and / or processing circuitry 36, causes the processor 38 and / or processing circuitry 36 to perform the processes described herein with respect to network node 16.

[0058] The communication system 10 further includes the WD 22 already referred to. The WD 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the WD 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves. For example, the radio interface 46 of the wireless device 22 may include BFTM frame transmitter 26 which may be configured as described herein..

[0059] The hardware 44 of the WD 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0060] Thus, the WD 22 may further comprise software 56, which is stored in, for example, memory 54 at the WD 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the WD 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the WD 22.

[0061] The processing circuitry 50 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by WD 22. The processor 52 corresponds to one or more processors 52 for performing WD 22 functions described herein. The WD 22 includes memory 54 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 56 and / or the client application 58 may include instructions that, when executed by the processor 52 and / or processing circuitry 50, causes the processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to WD 22.

[0062] In some embodiments, the inner workings of the network node 16 and WD 22 may be as shown in FIG. 3 and independently, the surrounding network topology may be that of FIG. 2. The wireless connection 32 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve.

[0063] The various units shown in FIGS. 2 and 3 may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

[0064] FIG. 4 is a flowchart of an example process in a network node 16 configured as a first device for backscattering device ranging and positioning. The network node 16 may be an AP STA or a non-AP STA. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the BFTM frame receiver 24), processor 38, and / or radio interface 30. Network node 16 such as via processing circuitry 36 and / or processor 38 and / or radio interface 30 is configured to receive a backscattered fine time measurement, BFTM, frame from a second device 22 and a reflected BFTM frame from the BD 25, the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD 25 from the second device 22 (Block S10). The method also includes determining a difference in time of arrival at the first device 16 between the BFTM frame received from the second device 22 and the reflected BFTM frame received from the BD 25 (Block S12). The method further includes determining a sum of a first distance between the first device 16 and the second device 22 and a second distance between the second device 22 and the BD 25 based at least in part on the difference in time of arrival (Block S14). The method also includes determining a position of the BD 25 based at least in part on triangularization using positions of the first device 16 and the second device 22 as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first distance and the second distance (Block SI 6).

[0065] In some embodiments, the second device 22 is collocated with the first device 16. In some embodiments, the first device 16 and second device 22 share a duplexing capability. In some embodiments, the difference in time of arrival is based at least in part on one or more of a time measurement, a power measurement and an angle of arrival. In some embodiments, the method includes receiving a plurality of reflected BFTM frames from the BD 25, each reflected BFTM frame arriving at the BD 25 from one of a plurality of second devices. In some embodiments, the position of the BD 25 is determined as a point of intersection of a plurality of ellipsoids. In some embodiments, the method includes determining a position for each BD 25 of a plurality of BDs 25 based at least in part on reflected BFTM frames received from each BD 25 of the plurality of BDs 25. In some embodiments, the reflected BFTM frame received from the plurality of BDs 25 are shifted in frequency by different amounts to facilitate their separation at the first device 16. In some embodiments, the BFTM frame from the second device 22 and the reflected BFTM frame are received in measurement bursts.

[0066] FIG. 5 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. The wireless device 22 may be an AP STA or a non-AP STA. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 50 (including the BFTM frame transmitter unit 26), processor 52, and / or radio interface 46. Wireless device 22 such as via processing circuitry 50 and / or processor 52 and / or radio interface 46 is configured to receive a request from a first device 16 to transmit a backscattered fine time measurement, BFTM, frame to the BD 25 (Block SI 8). The method also includes energizing the BD 25 (Block S20). The method also includes transmitting the BFTM frame to the BD 25 and to the first device 16 (Block S22).

[0067] According to this aspect, in some embodiments, the method includes sending a command to the BD 25 indicating that a ranging session is to be performed. In some embodiments, the command includes an indication of an amount of frequency shift to be applied by the BD 25 to the BFTM frame. In some embodiments, the request includes an indication of a frequency shift to be applied by the BD 25 to the BFTM frame. In some embodiments, the first device 16 and the second device 22 are collocated. In some embodiments, the method includes illuminating a plurality of BDs 25 with the BFTM frame.

[0068] Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for backscattering device ranging and positioning.

[0069] A ranging protocol scheme based at least in part on the FTM protocol but adopted to work with BDs 25 is disclosed. Assume that the position of the AP 16 and the STA 22 is known. Furthermore, the AP 16 may be a STA 22 and / or the STA 22 may be an AP 16. Using the proposed protocol between multiple devices provides the problem of triangularization of ellipsoids. This is more complex than triangularization of spheres, but well known in the literature. Methods are disclosed to obtain the ellipsoids and how APs 16 and STAs 22 may be used to obtain several ellipsoids. The following disclosure focusses on two dimensional ellipses, although principles disclosed herein apply to three dimensional ellipsoids as well.

[0070] FIG. 6 is a flow diagram that shows an example by which the command to perform ranging comes from the AP 16. The frames may be implemented as follows:

[0071] 1. The Command: Ranging is sent by the AP 16 to initiate the ranging process. It may be optional since the STA 22 could be the initiator of the process. It may also be sent by the STA 22 to the AP 16;

[0072] 2. An acknowledgement (ACK) is sent to acknowledge the Command: Ranging. These two frames may act as request to send / clear to send (RTS / CTS), offering channel protection in the network. Alternatively, an independent RTS / CTS procedure may be applied before the protocol begins;

[0073] 3. The STA 22 first energizes the tag, such that it may receive the consequent ranging command frame notifying the BD 25 that the ranging protocol is about to start. It then sends the Ranging Command to the BD 25, typically, but not limited to, a wake-up-packet, e.g., according to IEEE 802.1 Iba wake-up radio (WUR).

[0074] 4. The STA 22 sends a second energize frame to enable the BD 25 to reflect the Backscattered FTM (BFTM) frame. Since there is no information that needs to be carried in this frame, an null data packer (NDP) frame is sufficient, but any PHY packed data unit (PPDU) may be used as the BFTM frame. This energize frame may be optional if the BD 25 does not require more energy;

[0075] 5. The BFTM frame is sent from the STA 22 to both the AP 16 and the BD 25. The BFTM frame may for example be a 20 MHz frame sent on a first channel;

[0076] 6. The BD 25 reflects the BFTM frame and optionally frequency shifts it by an offset corresponding to the bandwidth (BW) of the frame. The frequency shift may be needed to avoid interference between the two signals. The reflected BFTM may for example be received by the AP 16 on a second channel;

[0077] 7. The AP 16 receives the first BFTM frame on a first channel at time t and the second BFTM frame on a second channel at time t2. The AP 16 may use these to derive

[0078] 8. Steps 4-7 may constitute a BFTM burst, and multiple such bursts may be applied N times to average several

[0079] The key frame in the “BFTM burst” is the BFTM frame. A receiving device may determine the arrival time of the illuminating BFTM frame and the arrival time of the reflected BFTM frame to perform the ranging. The BFTM frame may be reflected in the same frequency band as the illuminating BFTM frame. Alternatively, to avoid interference, the BFTM frame may be reflected in a frequency band that is shifted from the frequency band of the illuminating BFTM frame by the bandwidth of a BFTM frame As an example, assume that the AP 16 has reserved 40 MHz bandwidth, i.e. a channel that is an aggregation of a first 20 MHz channel and a second 20 MHz channel. This is better visualized in the next FIG. 7.

[0080] FIG. 7 represents a protocol in a different manner. Along the x-axis is time and on the y-axis is bandwidth. In this example, assume the AP 16 communicates to the STA 22 using a 40 MHz BW. In this example, the illuminating BFTM is being sent only over 20 MHz, and the reflected BFTM is sent over the other 20 MHz The full BW may be protected to as large extent as possible with legacy preambles and RTS / CTS.

[0081] Refer to the time the illuminating BFTM is received by the AP 16 as G and the time the reflected BFTM as t2. Then, the AP 16 may use tr, t2and the known position of the AP 16 and the STA 22 to do something equivalent to ranging.

[0082] FIG. 8 is a representation of a STA 22, BD 25 and AP 16. The illuminating BFTM and the reflected BFTM are also shown along with the times they are received by the AP 16.

[0083] FIG. 9 is an example where the position of the STA 22 and the position of the AP 16 are known. Therefore, the AP 16 knows 2c a-priori. Note: the distance between the STA 22 and the AP 16 if referred to as 2c because it is common to refer to the distance between the center of an ellipse to one of its focal points with the letter c. The AP 16 may derive the sum -length where capital C is the speed of light and tdi^ = t2— Using this, it turns out that the AP 16 knows that the BD 25 is placed somewhere along the ellipse shown as a dotted line in FIG. 9. The positions of the AP 16 and the STA 22 are the foci of the ellipse.

[0084] To find the BD location, one may do triangularization with ellipses. Either by using several STAs 22, or several APs 16, all which may be used in multiple combinations to provide several measurements. The illuminating BFTM transmitted from the illuminating devices may be transmitted at different times and / or on different frequency resources. Some examples are disclosed below.

[0085] The more ellipses that are generated and used in the triangularization, the better the position estimate becomes. This is illustrated in FIGS 10-12. Similarly, the more BFTM bursts are used, the more accurate the ranging becomes.

[0086] Some additional embodiments

[0087] • In addition to the timing information, received signal strength indicator (RS SI) information of the messages sent and received may be used to improve positioning. For example, assuming perfect reflection by the BD 25, the RSSI relation between the BFTM and the Reflected BFTM may be used to infer another estimate of b + d, or the relationship between b and d For example, if the ratio between b and d may be inferred from the RSSI of the BFTM and the RSSI of the reflected BFTM, then the number of possible locations of the BD 25 on the ellipse may be reduced;

[0088] • There may be some delay in the BD 25 at the time of reflection. Presumably this delay may be known or estimated;

[0089] • The STA 22 and the AP 16 may have reversed roles, where the AP 16 illuminates the BD 25 and the STA 22 receives the reflected frames. Which device takes which role will most likely depend on which device may act the better energizer for the BD 25;

[0090] • The AP 16 and the STA 22 may be the same device. The problem then reduces to the standard triangularization problem using circles (and equivalently c = 0 and b = d). However, the device should then be full duplex or sub-band full duplex capable;

[0091] • It is reasonable to assume that the BD 25 is located close to the STA 22, rather than close to the AP 16. If this is the case, some points on the ellipse(s) may be ruled out as the position for the BD 25; • In positioning and ranging, a wider BW is preferable. This impacts the performance mostly through the BFTM frame;

[0092] • If only less than or equal to 20 MHz BW is available, new synchronization frames for narrower BWs may be needed. For example, 10 MHz BFTM frames may be used;

[0093] • It may be possible for the AP 16 to detect the reflected BFTM frame in the same channel as the direct BFTM frame (from the STA 22). If this is the case, it may make sense to let the BFTM frame be as wide as possible (i.e., the full BW reserved by the AP 16) and the reflection may be in the same channel;

[0094] • The BD 25 may apply some simple modulation to the BFTM frame, for the AP 16 to distinguish it from a reflection in the environment. Note that when the BFTM frame is reflected on a different channel, this should not be an issue because no natural reflections would be expected to cause this frequency shift;

[0095] • The BD 25 may apply some simple modulation to the BFTM frame, for enabling the AP 16 to distinguish it from a reflection in the environment. Note that when the BFTM frame is reflected on a different channel, this should not be an issue because no natural reflections would be expected to cause this frequency shift;

[0096] • Several BDs 25 may use different frequency shifts for the reflections to perform ranging of multiple BDs simultaneously. This may be beneficial in terms of communication overhead. However, with a fixed amount of total bandwidth, there is a tradeoff between efficiency (from user aggregation) and the achievable ranging accuracy. An example of how such a protocol and ranging is shown in FIGS. 13 and 14. In this example, for simplicity a total BW of 60 MHz and 20 MHz BFTM has been assumed

[0097] The above embodiments may be combined with each other and with the embodiments using several illuminating and / or receiving devices.

[0098] A ranging protocol may be specified in technical standards. If the ranging protocol operates on BDs 25, the methods disclosed herein may be standardized. This may be the case when the IEEE AMP TIG becomes a Task Group (TG).

[0099] Some embodiments may include one or more of the following protocols and methods to perform positioning of BDs 25 in a system where the positions of APs 16 and STAs 22 are assumed known.

[0100] 1. A method for performing ranging of a BD, the method comprises, a) (optional) A first device requesting a second device to act as an illuminator for a BD device b) (optional) The second device acknowledging the request c) The second device energizing the BD d) The second device sending a command to the BD that a ranging session is about to start. e) (optional) The second device re-energizes the BD f) The second device illuminating the BD with a wideband backscattered FTM (BFTM) frame g) The BD reflecting the BFTM frame h) The first device receiving both the BFTM frame and the reflected BFTM frame i) The first device calculating a difference in the arrival time of the illuminating signal and the reflected signal to determine the relative distance between the first device, second device and BD.

[0101] 2. As in any of the above, where steps (e) - (i) are repeated in succession as part of a measurement burst.

[0102] 3. As in any of the above, where step (g) also contains a frequency shift of the reflected signal.

[0103] 4. As in any of the above, where the second device is also acting as the first device (i.e., there is only a first device and a BD).

[0104] 5. As in any of the above, where the calculation of the difference in step i) is based on a difference of time, power, angle of arrival or any other positional indicator.

[0105] 6. As in any of the above, where there are multiple first devices receiving the illuminating signal and the reflected signal, and calculating relative distances equivalently to step i).

[0106] 7. As in any of the above, where multiple BDs 25 are part of the same measurement session and the multiple BDs 25 have been assigned separate frequency resources to frequency shift their reflected BFTM frames.

[0107] 8. As in any of the above, where there is multiple second devices sending illuminating signals.

[0108] As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD- ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0109] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0110] These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0111] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0112] Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0113] Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

[0114] Abbreviations that may be used in the preceding description include: Abbreviation Explanation

[0115] AMP AMbient Powered

[0116] AP Access Point

[0117] BD Backscattering Device

[0118] BW Bandwidth

[0119] FTM Fine Timing Measurement

[0120] RS SI Received Signal Strength Indicator

[0121] STA Station

[0122] ToF Time of Flight

[0123] It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

Claims.:

1. A method in a first device (16) for performing ranging of a backscatter device, BD (25), the method comprising: receiving (S10) a backscattered fine time measurement, BFTM, frame from a second device (22) and a reflected BFTM frame from the BD (25), the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD (25) from the second device (22); determining (S12) a difference in time of arrival at the first device (16) between the BFTM frame received from the second device (22) and the reflected BFTM frame received from the BD (25); determining (S14) a sum of a first distance between the first device (16) and the second device (22) and a second distance between the second device (22) and the BD (25) based at least in part on the difference in time of arrival; and determining (SI 6) a position of the BD (25) based at least in part on triangularization using positions of the first device (16) and the second device (22) as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first distance and the second distance.

2. The method of Claim 1, wherein the second device (22) is collocated with the first device (16).

3. The method of Claim 2, wherein the first device (16) and second device (22) share a duplexing capability.

4. The method of any of Claims 1-3, wherein the difference in time of arrival is based at least in part on one or more of a time measurement, a power measurement and an angle of arrival.

5. The method of any of Claims 1-4, further comprising receiving a plurality of reflected BFTM frames from the BD (25), each reflected BFTM frame arriving at the BD (25) from one of a plurality of second devices.

6. The method of Claim 5, wherein the position of the BD (25) is determined as a point of intersection of a plurality of ellipsoids.

7. The method of any of Claims 1-6, further comprising determining a position for each BD (25) of a plurality of BDs (25) based at least in part on reflected BFTM frames received from each BD (25) of the plurality of BDs (25).

8. The method of Claim 7, wherein the reflected BFTM frame received from the plurality of BDs (25) are shifted in frequency by different amounts to facilitate their separation at the first device (16).

9. The method of any of Claims 1-8, wherein the BFTM frame from the second device (22) and the reflected BFTM frame are received in measurement bursts.

10. A first device (16) configured to perform ranging of a backscatter device, BD (25), the first device (16) configured to: receive a backscattered fine time measurement, BFTM, frame from a second device (22) and a reflected BFTM frame from the BD (25), the reflected BFTM frame being one of a reflection of and a modulated reflection of the BFTM frame arriving at the BD (25) from the second device (22); determine a difference in time of arrival at the first device (16) between the BFTM frame received from the second device (22) and the reflected BFTM frame received from the BD (25); determine a sum of a first distance between the first device (16) and the second device (22) and a second distance between the second device (22) and the BD (25) based at least in part on the difference in time of arrival; and determine a position of the BD (25) based at least in part on triangularization using positions of the first device (16) and the second device (22) as focal points of an ellipsoid, the ellipsoid being defined based at least in part on the determined sum of the first distance and the second distance.

11. The first device (16) of Claim 10, wherein the second device (22) is collocated with the first device (16).

12. The first device (16) of Claim 11, wherein the first device (16) and the second device (22) share a duplexing capability.

13. The first device (16) of any of Claims 10-12, wherein the difference in time of arrival is based at least in part on one or more of a time measurement, a power measurement and an angle of arrival.

14. The first device (16) of any of Claims 10-13, wherein the first device (16) is configured to receive a plurality of reflected BFTM frames from the BD (25), each reflected BFTM frame arriving at the BD (25) from one of a plurality of second devices.

15. The first device (16) of Claim 14, wherein the position of the BD (25) is determined as a point of intersection of a plurality of ellipsoids.

16. The first device (16) of any of Claims 10-15, wherein the first device (16) is configured to determine a position for each BD (25) of a plurality of BDs (25) based at least in part on reflected BFTM frames received from each BD (25) of the plurality of BDs (25).

17. The first device (16) of Claim 16, wherein the reflected BFTM frame received from the plurality of BDs (25) are shifted in frequency by different amounts to facilitate their separation at the first device (16).

18. The first device (16) of any of Claims 10-17, wherein the BFTM frame from the second device (22) and the reflected BFTM frame are received in measurement bursts.

19. A method in a second device (22) to perform ranging of a backscatter device, BD (25), the method comprising: receiving (SI 8) a request from a first device (16) to transmit a backscattered fine time measurement, BFTM, frame to the BD (25); energizing (S20) the BD (25); and transmitting (S22) the BFTM frame to the BD (25) and to the first device (16).

20. The method of Claim 19, further comprising sending a command to the BD (25) indicating that a ranging session is to be performed.

21. The method of Claim 20, wherein the command includes an indication of an amount of frequency shift to be applied by the BD (25) to the BFTM frame.

22. The method of any of Claims 19-21, wherein the request includes an indication of a frequency shift to be applied by the BD (25) to the BFTM frame.

23. The method any of Claims 19-22, wherein the first device (16) and the second device (22) are collocated.

24. The method of any of Claims 19-23, further comprising illuminating a plurality of BDs (25) with the BFTM frame.

25. A second device (22) configured to perform ranging of a backscatter device, BD (25), the second device (22) configured to: receive a request from a first device (16) to transmit a backscattered fine time measurement, BFTM, frame to the BD (25); energize the BD (25); and transmit the BFTM frame to the BD (25) and to the first device (16).

26. The second device (22) of Claim 25, wherein the second device (22) is further configured to send a command to the BD (25) indicating that a ranging session is to be performed.

27. The second device (22) of Claim 26, wherein the command includes an indication of an amount of frequency shift to be applied by the BD (25) to the BFTM frame.

28. The second device (22) of any of Claims 25-27, wherein the request includes indicates a frequency shift to be applied by the BD (25) to the BFTM frame.

29. The second device (22) any of Claims 25-28, wherein the first device (16) and the second device (22) are collocated.

30. The second device (22) of any of Claims 25-29, wherein the second device (22) is further configured to illuminate a plurality of BDs (25) with the BFTM frame.

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