Reference signal design and device procedures for downlink-based positioning / ranging using arriving multi-frequency phase differences

Abstract

A method is provided for use in a wireless transmit / receive unit (WTRU) configured to communicate over a zero energy (ZE) interface.SOLUTION: The method includes a WTRU receiving a first positioning reference signal (PRS) resource having parameters characterizing a first PRS and determining the suitability of the first PRS resource for use by the WTRU. The method also includes measuring phase difference of arrival (PDOA) of the available frequency pairs and generating a range estimate based on the PDOA measurements. Further, the method includes the WTRU evaluating the reliability of the PDOA measurement and the accuracy of the distance estimate and reporting the distance estimate on a condition that sufficient accuracy is achieved.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 967,953, filed January 30, 2020, and U.S. Provisional Patent Application No. 63 / 051,709, filed July 14, 2020, which are incorporated by reference as if fully set forth. [Background technology]

[0002] For some mobile device use cases, the unavailability of GNSS coverage in indoor environments, the power consumption requirements, and the electronic complexity of GNSS receivers necessitate alternatives to satellite-based (e.g., GNSS) positioning of mobile devices (e.g., to handhelds, ultra-low power (ULP) devices, wearables, and fitness trackers to IoT / MTC objects). Summary of the Invention

[0003] According to one embodiment disclosed herein, a method is provided for use in a wireless transmit / receive unit (WTRU) configured to communicate over a zero energy (ZE) interface. The method includes receiving, by the WTRU, a first positioning reference signal (PRS) resource having parameters characterizing the first PRS and determining suitability of the first PRS resource for use by the WTRU. The method also includes measuring a phase difference of arrival (PDOA) of at least one of an available frequency pair and generating a distance estimate based on the multi-frequency (MF)-PDOA measurement using the first PRS resource. The method further includes the WTRU evaluating the reliability of the PDOA measurements and the accuracy of the distance estimate, and, conditional on determining that the first PRS resource is not suitable for use by the WTRU, conditional on determining that the MF-PDOA measurements are not sufficiently reliable, or conditional on determining that the distance estimate is not sufficiently accurate, requesting a second PRS resource and its associated parameters, the parameters of the second PRS resource being different from the parameters of the first PRS resource. The method also includes reporting the distance estimate, conditional on sufficient accuracy being achieved.

[0004] According to embodiments disclosed herein, there is provided a wireless transmit / receive unit (WTRU) configured to communicate over a zero energy (ZE) interface. The WTRU includes a transceiver and a ZE receiver. The ZE receiver is capable of receiving a first positioning reference signal (PRS) resource having parameters characterizing the first PRS. The WTRU further includes a processor configured to determine suitability of the first PRS resource for use by the WTRU and measure a phase difference of arrival (PDOA) for at least one of the available frequency pairs. The processor is also configured to generate a distance estimate based on MF-PDOA measurements using the first PRS resource and evaluate the reliability of the PDOA measurements and the accuracy of the distance estimate. The processor is further configured to request a second PRS resource and its associated parameters upon determining that the first PRS resource is not suitable for use by the WTRU, upon determining that the MF-PDOA measurements are not sufficiently reliable, or upon determining that the distance estimate is not sufficiently accurate, the parameters of the second PRS resource being different from the parameters of the first PRS resource. The processor is also configured to report the distance estimate upon achieving sufficient accuracy. [Brief explanation of the drawings]

[0005] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate similar elements and in which: [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an exemplary wireless transmit / receive unit (WTRU) that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 1C] 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 1D]FIG. 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system shown in FIG. 1A, according to one embodiment. [Figure 2] 10 is a graph showing an example of the phase difference between a pair of unmodulated continuous waves of frequencies f0 and f1. [Figure 3] FIG. 1 illustrates an example of a differential MF-PDOA scheme. [Figure 4] FIG. 10 illustrates an example of a ZE receiver performing differential MD-PDOA measurements on CW transmitted from AN A at frequencies f1 and f2 and CW transmitted from AN B at frequencies f'1 and f'2. [Figure 5] 1 is a flowchart illustrating a method according to an example embodiment. [Figure 6] FIG. 1 shows examples of estimated PDOAs for two essential sets. [Figure 7] A diagram showing an example of PRS-related information exchange during an attach procedure. [Figure 8] 1 is a graph showing an example of phase ambiguity. [Figure 9] 10 is a graph showing an example of a TA used to validate results from MF-PDOA. [Figure 10] FIG. 10 illustrates an exemplary timestamp for ULP / ZE transmission. [Figure 11] FIG. 1 illustrates an example of an AN radiating CW and a selected facilitator. [Figure 12] FIG. 1 illustrates an exemplary frequency report shared with an AN. [Figure 13] 1 is a flowchart illustrating an example of a semi-static resource / configuration algorithm for a differential MF-PDOA scheme. [Figure 14] FIG. 1 illustrates an exemplary linear frequency chirp. [Figure 15] 1 is a flowchart of a method for frequency and beam sweeping in accordance with an example embodiment. [Figure 16] 1 is a flowchart illustrating a method according to an example embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] 1A illustrates an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0007] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a mobile phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., remote surgery), an industrial device and application (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain context), a consumer electronic device, an IoT / MTC object, an ultra-low power (ULP) device, a wearable, a fitness tracker, a device operating in a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE, a terminal, a mobile device, or the like.

[0008] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNodeB (eNode B, eNB), a Home NodeB, a Home eNodeB, a gNode B (gNode B, gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, or other next generation NodeB. Although the base stations 114a, 114b are each shown as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0009] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers per sector of the cell, for example, using beamforming to transmit and / or receive signals in desired spatial directions.

[0010] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over the air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0011] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a of the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High-Speed ​​Uplink (UL) Packet Access (HSUPA).

[0012] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-APro).

[0013] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0014] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may jointly implement LTE radio access and NR radio access, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0015] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity, WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), GSM Evolution (Enhanced Data rates for GSM Evolution, EDGE), GSM EDGE (GERAN), or the like.

[0016] 1A may be, for example, a wireless router, a Home Node B, a Home eNode B, or an access point and may utilize any suitable RAT to facilitate wireless connectivity in a local area such as a location such as a business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-APro, NR, etc.). As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 through the CN 106.

[0017] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it will be understood that the RAN 104 and / or CN 106 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0018] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a public switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) of the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs that may use the same RAT as the RAN 104 or a different RAT.

[0019] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links.) For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a that can use cellular-based wireless technology and a base station 114b that can use IEEE 802 wireless technology.

[0020] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136 (or other component(s) that provide positioning and ranging means), and / or other peripherals 138. It will be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0021] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0022] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0023] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may use MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0024] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0025] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Furthermore, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0026] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0027] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0028] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, etc.

[0029] The WTRU 102 may include a full-duplex radio for transmitting and receiving some or all of the signals (e.g., associated with a particular subframe on both the UL (e.g., for transmission) and DL (e.g., for reception)) simultaneously and / or together. The full-duplex radio may include an interference management unit for reducing and or substantially eliminating self-interference through hardware (e.g., chokes) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmitting and receiving some or all of the signals (e.g., associated with a particular subframe on either the UL (e.g., for transmission) or DL ​​(e.g., for reception)).

[0030] 1C is a system diagram illustrating the RAN 104 and the CN 106, according to one embodiment. As noted above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0031] The RAN 104 may include eNode-Bs 160a, 160b, and 160c, although it will be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, and 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the eNode-Bs 160a, 160b, and 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0032] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling, etc. in the UL and / or DL. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0033] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although the foregoing elements are shown as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0034] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0035] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions such as anchoring the user plane during inter-eNode B handovers, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0036] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0037] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional landline communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. Furthermore, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0038] Although the WTRU is depicted in FIGS. 1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may use a wired communication interface (e.g., temporarily or permanently) with the communication network.

[0039] In a representative embodiment, the other network 112 may be a WLAN.

[0040] A WLAN in infrastructure Basic Service Set (BSS) mode may have an access point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access to or interface with a distribution system (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic to a STA originating from outside the BSS may arrive through the AP and be delivered to the STA. Traffic originating from a STA to a destination outside the BSS may be sent to the AP and transmitted to the respective destination. Traffic between STAs within a BSS may be transmitted, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be transmitted between (e.g., directly between) a source STA and a destination STA via a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all of the STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad hoc" communication mode.

[0041] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically configured width. The primary channel may be the operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0042] High Throughput (HT) STAs may, for example, use 40 MHz wide channels for communication via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0043] A Very High Throughput (VHT) STA may support channels of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz width. 40 MHz and / or 80 MHz may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed, and the combined data may be transmitted to the Medium Access Control (MAC).

[0044] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in macro coverage areas. MTC devices may have limited capabilities, including, for example, support for (e.g., only) specific and / or limited bandwidths. An MTC device may include a battery with a battery life above a threshold (eg, to maintain a very long battery life).

[0045] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that can be designated as a primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be configured and / or limited by the STA among all STAs operating in the BSS that support the minimum bandwidth operating mode. In an 802.11ah example, the primary channel can be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration can depend on the conditions of the primary channel. For example, if the primary channel is busy, a STA (that only supports 1 MHz mode of operation) transmitting to the AP may cause all of the available frequency bands to be considered busy, even if most of the available frequency bands are idle.

[0046] In the United States, the available frequency band that can be used by 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz depending on the country code.

[0047] 1D is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As mentioned above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c over the air interface 116 using NR radio technology. The RAN 104 may also communicate with the CN 106.

[0048] The RAN 104 may include gNBs 180a, 180b, and 180c, although it will be understood that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, and 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, and 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit and / or receive signals to the gNBs 180a, 180b, and 180c. Thus, the gNB 180a may, for example, transmit wireless signals to and / or receive wireless signals from the WTRU 102a using multiple antennas. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on the unlicensed spectrum, and the remaining component carriers may be on the licensed spectrum. In one embodiment, the gNBs 180a, 180b, and 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or 180c).

[0049] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., including varying numbers of OFDM symbols and / or varying lengths of absolute time).

[0050] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNode-Bs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. The non-standalone configured WTRUs 102a, 102b, 102c may communicate with and connect to gNBs 180a, 180b, 180c while also communicating with and connecting to another RAN, such as eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0051] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, DC, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0052] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are shown as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0053] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for user authentication of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selection of the SMF 183a, 183b for registration, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMFs 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0054] The SMFs 183a and 183b may be connected to the AMFs 182a and 182b in the CN 106 via an N11 interface. The SMFs 183a and 183b may also be connected to the UPFs 184a and 184b in the CN 106 via an N4 interface. The SMFs 183a and 183b may select and control the UPFs 184a and 184b and configure the routing of traffic through the UPFs 184a and 184b. The SMFs 183a and 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0055] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as packet routing and forwarding, user plane policy enforcement, support for multi-homed PDU sessions, handling user plane QoS, DL packet buffering, mobility anchoring, etc.

[0056] The CN 106 may facilitate communication with other networks. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. Additionally, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0057] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0058] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation devices may be directly coupled to another device for the purpose of testing and / or performing tests using over-the-air wireless communication.

[0059] One or more emulation devices may perform one or more functions, inclusive, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, e.g., one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0060] 1A, 1B, 1C, and 1D, the WTRU may employ technologies that include alternatives to satellite-based positioning. Additionally, there are use cases and technical needs for alternatives to satellite-based positioning in devices such as handheld and IoT / MTC objects, ultra-low power (ULP) devices, wearables, and fitness trackers. For example, devices using LTE / NR may have poor or no GNSS reception in various indoor environments, such as a mall. ULP devices, also known as zero energy (ZE) devices, enable dramatic savings in power consumption compared to legacy devices. However, electronic components such as so-called "passive" components such as Schottky diodes and MEMs may not meet the energy demands for a given use case, nor may they have the capability for satellite-based positioning.

[0061] Generally, the following may serve as abbreviations for terms used in this specification: AN Access Node; BW Bandwidth; CRS Cell-specific reference signal; CRT Chinese Remainder Theorem; C-V2X Cellular Vehicle-to-Everything; CW Unmodulated Continuous Wave; CW-RS CW Reference Signal; D2D Device-to-Device Communication; DL Downlink; ED Energy Detection; FTM Precise Time Measurement; IE Information Element; IoT Internet of Things; IIoT Industrial IoT; LOS Line of Sight; MF-PDOA Multi-Frequency Phase Difference of Arrival; MTC Machine-Type Communication; NR New Radio (5G); NW Network; ProSe Proximity Service; PRS Positioning Reference Signal; RB Resource Block; RF Radio Frequency; RTT Round Trip Time; SCS Subcarrier Spacing; TA Timing Advance; ToF Time of Flight; TRS Tracking Reference Signal; TRX Transceiver; UE User Equipment; UL Uplink; ULP Ultra-Low Power; ZE Zero Energy.

[0062] Multifrequency Phase Difference of Arrival (MF-PDOA) is a radiolocation-based positioning technique / method suitable for distance estimation that utilizes the basic electronic components that make up some devices, such as ULP / ZE devices. In one example, MF-PDOA via backscatter can be used with RFID. Furthermore, as discussed herein, MF-PDOA can be used with LTE / NR handsets in GNSS-less environments. Considering various environments, such as indoors or outdoors, MF-PDOA can be an attractive solution for LTE / NR devices, such as IoT and other electronic objects.

[0063] As described herein, a WTRU may be a device that utilizes MF-PDOA technology and / or legacy technology. This may be possible by utilizing the same hardware for the two technologies or by utilizing separate hardware for each technology, respectively. As described herein, a network device may be a node on a network.

[0064] Phase difference of arrival (PDOA) used in the downlink (DL) may involve a network device transmitting a pair of unmodulated continuous waves (CWs) and a receiving device measuring the phase difference between the two arriving CWs so that the receiving device estimates the separation (i.e., distance) to the network device. MF-PDOA may involve making phase difference measurements of multiple pairs of CWs.

[0065] As described above, MF-PDOA may be used to calculate the distance between a ULP / ZE device and a particular AN. Furthermore, a positioning scheme (e.g., differential MF-PDOA) may be utilized in which MF-PDOA pairs are transmitted from different ANs to calculate the difference in distance between the ULP / ZE device and each AN, allowing the ULP / ZE device to avoid the need for a local oscillator. As discussed herein, a WTRU may be interchangeable with a ULP / ZE device.

[0066] Figure 2 shows the frequencies f0 and f i 2 is a graph 200 illustrating an example of the phase difference between a pair of unmodulated continuous waves 202 and 204 having frequencies f0 and f i (Frequency difference Δf i A pair of CWs is emitted from one end and the phase between the pair is measured at the other end. (In the case of round trip propagation) the two ends may be the same. As described herein, the CWs are emitted from the access node (AN) and the observed phase difference Δφ i 206 can be measured at the WTRU (e.g., a ULP / ZE device). In general, distance d = c t d In the case of a pair of CWs propagating overd are the speed of light and the propagation time, respectively), the total phase difference can be: ΔΦ i =2π Δf i ·t d .

[0067] Δφ i =mod(ΔΦ i , 2π), the total phase difference can be rewritten as:

[0068]

number

[0069] Actual / true distance R T can be shown as follows:

[0070]

number

[0071] However, Δφ wraps around between 0 and 2π. i is all that can be measured, and therefore the apparent / measured distance R A can be measured (value is the maximum distance R max,i is less than).

[0072]

number

[0073] An embodiment of the present invention is max,i When R is less than R, only the apparent distance is correct, so the measurable distance is R max,i Then, the upper limit is set by the pair of CW Δf i It is determined by:

[0074] One way to increase the maximum unambiguous distance is to utilize multiple pairs of frequencies (the "MF" in MF-PDOA), where each pair provides a phase difference, and combine the phase differences using mathematical techniques such as the Chinese Remainder Theorem (CRT).

[0075] CRT is a set of coprime numbers {ξ k} (numbers that are coprime and therefore have a greatest common divisor (gcd) of 1), e.g., 3, 5, and 8. The coefficients of d for the coprime numbers are multiplied by the remainder {a k}, then

[0076]

number

[0077] Then there are solutions of the form d+m·N, ​​where m is an integer.

[0078]

number

[0079] where lcd(·) is the least common multiple function.

[0080] In our case we have the following set of equations:

[0081]

number

[0082] In the formula, R corresponds to d in formula 5, and R A,i is a i corresponds to R max,i is ξ i Corresponding to R, R A,i , and R max,i is expressed as a discrete value that is a multiple of the parameter Δr, which will be described later.

[0083] The range bin resolution (the term "range bin resolution" is used to distinguish it from actual individual bins or "range bins") may be defined to have the following relationship to the coprime number:

[0084]

number

[0085] The parameter Δr corresponds to the identity element of the CRT list in equation (7). In other words, it is the granularity at which the distance is defined. Since Δr is constant over all i, the following equation defines the relationship between frequency and coprime numbers:

[0086]

number

[0087] Then, the highest coprime value is the Δφ that the device can achieve for the given channel conditions. i can be determined with reliable resolution of

[0088] Generally, the effective R max , i.e., the maximum valid unambiguous distance is the maximum unambiguous distance for frequency pair i, R max,i Coefficient N / ξ i

[0089]

number

[0090] Using equations 6 and 9,

[0091]

number

[0092] Since it is known that

[0093]

number

[0094] It means the following:

[0095]

number

[0096] where gcd(·) is the greatest common divisor,

[0097]

number

[0098] 3, in the differential PDOA scheme 300, two pairs of CWs can be transmitted at once, i.e., frequencies f_0 and f_1. i A first pair of CWs 302 having a frequency

[0099]

number

[0100]

number

[0101] One advantage of differential MF-PDOA compared to MF-PDOA is that it can eliminate the need for any local oscillator. Instead, two CWs can be multiplied together within each PDOA pair of each AN. Detailing differential MF-PDOA, the CWs with frequencies f1 and f2 transmitted from the AN A 310 and received at the WTRU (e.g., ZE device) 340 are respectively:

[0102]

number

[0103]

number

[0104]

number

[0105] Similarly, the same frequency difference is transmitted from AN B 320 and received by WTRU 340.

[0106]

number

[0107]

number

[0108]

number

[0109] Therefore, the change in phase difference (between B and A) is (θ in Figure 4) BA =∇Δφ 21,BA is.

[0110]

number

[0111] 4 results in Equation 12, but with a sine function instead of a cosine function. Finally, this can be used to calculate the "measurement" sinθ BA and cosθ BA The argument of cosine / sine can be found by feeding into the arctangent module. Also, Equation 15 ranges between -π and π (rather than between π and 2π).

[0112] By ensuring time synchronization between ANs (for example, t A =t B ), differential distance d BA =d B -d A can be given as follows:

[0113]

number

[0114] d BAcan be either positive or negative (depending on the proximity to A or B, respectively), so the range can be [-π and π].

[0115] This scheme can then be applied using another pair of AN (e.g., A and C) with the same phase difference ∇Δφ 21,BA (or the difference distance d BA Note that a location with ANs A and B traces a hyperbola with foci at ANs A and B. Another hyperbola can then be traced by locations with the same phase difference for signals emanating from ANs A and C. The location of the WTRU (e.g., a ZE device) can then be determined by the intersection of these two hyperbolae. Such a procedure, described in the context of differential MF-PDOA, may be equivalent to a "hyperbolic positioning" (or hyperbolic trilateration) approach similar to LORAN-C and OTDOA, but using MF-PDOA.

[0116] Figure 4 is a schematic diagram illustrating one way to implement a differential MF-PDOA. High-Q MEMS boost transformers 411, 412, 413, and 414, as shown, enable narrowband CW while improving sensitivity; multiplier / mixers multiply the CW'; and low-pass filters 431 and 432 remove the double-frequency components produced by the multiplier. Another possibility is to have a MEMS transformer with sufficient bandwidth to enable a pair of CWs (for the PDOA), thereby halving the number of transformers. However, this may reduce sensitivity (e.g., due to low-voltage boost, thermal noise, and wide bandwidth).

[0117] In some cases, CW may be emitted from the AN and backscattered from the WTRU to measure the PDOA at the AN.

[0118] When measuring the PDOA at the AN via backscattering, each CW may propagate over a distance that is twice the distance d (between the AN and the WTRU). i CW (frequency difference Δf i), if there is no processing delay at the WTRU (e.g., CW is not modulated, so no processing is required), the observed phase difference Δφ i may be measured back to AN, as in Equation 1, ΔΦ i =4π Δf i This can be expressed as d / c and rewritten as follows:

[0119]

number

[0120] Next, the actual / true distance R T can be shown as follows:

[0121]

number

[0122] Recalling Equation 3,

[0123]

number

[0124] Apparent / measured distance R A and maximum distance R max,i are as follows, respectively:

[0125]

number

[0126] Also, the CRT approach discussed herein related to MF-PDOA (i.e., to increase the maximum unambiguous distance of the MF-PDOA in DL) may be applicable to backscatter without delay.

[0127] If there is a delay at the WTRU receiver during backscatter, one approach may be to use differential MF-PDOA and instead measure differential one-way distance in the UL at ANs A and B (e.g., backscattered signals may be processed at ANs A and B). (e.g., for one-way distance in the UL), it may be shown as follows:

[0128]

number

[0129] Extending the role of ZE devices to include positioning-related measurements can further improve battery life, but their modest electronic capabilities require them to advertise these capabilities to the network, as well as preferred / supported values ​​for supported range bin resolution, coprime number, and maximum frequency separation. Furthermore, modest electronic capabilities require the network to coordinate positioning reference signals (PRS), including a set of CWs, to facilitate distance estimation at the UE via MF-PDOA.

[0130] A ZE device may have limited RF capabilities and / or may only support specific values ​​of the parameters that define the MF-PDOA positioning scheme and the RF characteristics of the signals required for the MF-PDOA positioning scheme. The limited RF capabilities of a ZE device may place an undue burden on the network in terms of the amount of radio resources that need to be allocated for ULP distance measurements.

[0131] Therefore, a procedure is needed to inform the network of device capabilities and assist the network in designing an MF-PDOA-based PRS signal tailored to the device specifications / capabilities, which in turn optimally assists the WTRU in determining distance, which may further assist the network in achieving efficient radio resource management.

[0132] As discussed herein, the RAN segment of a network is referred to as an Access Node (AN), which can refer interchangeably to eNBs, gNBs, access points, base stations, microcells, picocells, femtocells, etc. An AN may support LTE, NR, Wi-Fi, or ULP / ZE communications. Additionally, an AN may be mobile (i.e., co-located in a vehicle with mobile backhaul).

[0133] The term may refer not only to WTRUs but also to IoT / MTC objects, vehicles, etc.

[0134] The term Positioning Reference Signal (PRS) discussed herein refers to an ensemble of unmodulated continuous waves (CW ensembles) emitted by an AN for the purpose of distance estimation via MF-PDOA of a UE. The PRS may be defined according to a distance with a bin resolution Δr, and in such case, the term PRS stratum (one PRS stratum per Δr value) is used in this document to distinguish PRS resources for each Δr value.

[0135] As discussed herein, the phase difference of a given pair of CWs is called the PDOA. DL-based distance estimation via MF-PDOA is obtained from the PDOA measured for all CW pairs, their respective coprime factors, and distance bins.

[0136] Furthermore, in the case of differential MF-PDOA, procedures may be necessary for one or more reasons, such as: 1) finding a more suitable frequency to improve facilitators, channel characteristics, and location-related measurements located in the vicinity of the WTRU; 2) synchronizing the facilitators; 3) recruiting and configuring the facilitators to transmit CW pairs at the appropriate frequencies and at the appropriate times so that the WTRU can perform PDOA measurements; 4) customizing signal attributes and system parameters for each device according to their channel conditions and capabilities to make PDOA measurements more robust and improve positioning accuracy; and / or 5) providing a framework to enable additional approaches such as frequency sweeping and beam sweeping in the facilitators and WTRUs.

[0137] In one or more embodiments disclosed herein, the PRS may be emitted constantly (e.g., always emitted) or on-demand (e.g., emitted per request from the WTRU). In addition, the PRS may have a default / baseline configuration for coarse distance estimation, or a customized configuration with additional or alternative CW and specific characteristics to meet more stringent WTRU requirements (e.g., to increase robustness to channel impairments or achieve more accurate distance resolution). PRS resource requests may be device or group specific based on the WTRU's ULP / ZE hardware and MF-PDOA measurement capabilities. For example, each ULP / ZE modem may point to an identifier unique to a particular capability set. The identifier may then be used to request and determine appropriate PRS resources. It should be appreciated that the suitability of a particular set of PRS resources may be determined based on the WTRU's capabilities and ranging accuracy requirements. The capabilities and ranging accuracy requirements may include possible frequency pairs and frequency separations that the WTRU can support, as well as the distance from the serving cell that the WTRU requires. Thus, in one exemplary embodiment, the WTRU may request a minimum supported frequency separation Δf min , N}, and for all i in {1, 2, ..., N}, the frequency separation Δf iA WTRU may be presented with a PRS resource including a set of N frequency pairs with a frequency separation smaller than the minimum supported frequency separation. In this example, the WTRU may discard all frequency pairs with a frequency separation smaller than the minimum supported frequency separation and then evaluate the maximum unambiguous distance supported by the remaining frequency pairs according to Equation 11. In the condition where the determined maximum distance is less than the expected serving cell coverage distance, the PRS resource may be determined to be unsuitable. If the determined maximum unambiguous distance is determined to exceed the expected serving cell coverage distance, the PRS resource may be determined to be suitable. Thus, the suitability of a particular PRS resource may depend on ranging requirements and parameters and the capabilities of the WTRU over which the PRS is transmitted. It should be appreciated that if a PRS resource is determined to be unsuitable for use by the WTRU, another PRS resource may be requested.

[0138] A ULP device or a ZE device may refer to a hybrid device consisting of a primary modem (e.g., supporting another existing technology such as NR, LTE, or Wi-Fi) and a ULP / ZE modem. Phase measurements are performed by the ULP / ZE modem. A ULP or ZE device may be referred to as a type of WTRU, but is generally referred to herein as a device unless otherwise specified.

[0139] As discussed herein, there may be one or more schemes for determining the distance between a device and an AN utilizing only PDOA measurements, such as distance estimation using MD-PDOA with on-demand PRS and hybrid (MF-)PDOA with path delay measurements. For illustrative purposes only, these schemes may be referred to as a first scheme and a second scheme, respectively. In these schemes, PRS resources may be available only on demand.

[0140] In the first scheme, the PRS resource is the total (effective) R max , e.g., the minimum number of coprimes can be the desired

[0141]

number

[0142] In the second scheme, the PRS resource is the desired R max The determined additional pairs may then be used to detect / correct distance estimation errors, subsequently increasing robustness against channel impairments.

[0143] Additionally, there may be variations of either the first or second scheme in which the device communicates the PDOA estimate to the network and the network calculates the distance.

[0144] In a first scheme for MF-PDOA-based distance estimation when a PRS is available upon request, the AN may not be configured by default to emit a PRS that includes unmodulated continuous wave (CW). Instead, the ULP may send a request to the network to communicate the PRS. This PRS request may include the following process: Step 1) The WTRU sends a request for a PRS to the network. Step 2) The network transmits (e.g., communicates) the PRS, and / or, if necessary, Step 3) the WTRU sends another request to the network requesting additional PRS. In the first step of sending the request, the request from the WTRU for a PRS may include a list of parameters that meet the RF capabilities of the WTRU (e.g., a ZERO device) and its resolution requirements. This list may include RF and baseband capabilities, such as the total system bandwidth ΔF (e.g., the frequency difference between the lowest and highest frequency CWs); the minimum CW frequency f0; and the minimum supported frequency separation Δf for a pair of CWs. min ; Number of supported simultaneous PDOA measurements (number of phase differences); Minimum delay required between successive PDOA measurements; Supported / required coprime and maximum coprime values ​​{ξ kand / or phase sensitivity, given as the phase granularity or number of phase values ​​the device can calculate for neighboring cells, intermediate distances, cell edge conditions. This may also be other parameters, e.g., the desired range bin resolution, which may be one value or multiple values; the observed RSSI; the movement state; the required range accuracy.

[0145] Δr may not be required by the WTRU; the network may make this determination on behalf of the WTRU, and the value may be implicit from the coprime and frequency selection (Equation 8).

[0146] In the first step of the first scheme, the WTRU may be able to explicitly transmit fewer parameters, or alternatively, transmit an identifier of a standardized parameter set. The WTRU may also be able to specify which frequencies and co-prime factors to transmit.

[0147] In the third step of the first scheme (e.g., the second request), there may be changes in the values ​​of some of the parameters (e.g., relative to the initial request, e.g., the first step) due to changes in channel conditions or distance estimation requirements.

[0148] Once the network transmits the PRS (e.g., second step), after receiving the request with the above parameters, the AN may adjust the PRS according to the requested parameters and start radiating the PRS layer for each distance bin resolution. Also, the network may simply share the frequency it uses with the WTRU, and the network may radiate additional CWs that it shares with other devices (e.g., WTRUs).

[0149] The frequency pairs can have two configurations: 1) Sequential: The pairs are {f0,f1}, {f1,f2}, ..., {f k-1 ,f k}, in which the frequency increases monotonically (f0 <f1<...<f k-1 <f k ). Therefore, f0 and fk can be the lower and upper edges of the system bandwidth. 2) Co-extension: The pairs are {f0,f1}, {f0,f2}, ..., {f0,f k}, and in this configuration, f0 exists in all pairs. In this case, any frequency f i (i>0) may be the upper edge of the system bandwidth. As discussed herein, a co-extended configuration may be assumed for demonstration purposes.

[0150] Also, the coprime and frequency values ​​may not increase with i (e.g., ξ1=8, ξ2=5, ξ3=7). For the highest achievable range bin resolution, the pair i is (f i -f0) can be set to correspond to the maximum ΔF. Similarly, the maximum effective R max For , the frequency difference (f i -f0) is set to the minimum possible frequency separation.

[0151] For the transmit step (e.g., step 1 of the first scheme), Table 1 and the following paragraphs provide some examples showing coprime and frequency selection and their relationship to range bin resolution and maximum range. Also, receiver phase sensitivity is discussed.

[0152] [Table 1]

[0153] The maximum coprime value may be limited by the phase sensitivity of the ULP / ZE receiver. The higher the phase resolution (phase sensitivity), the larger the maximum coprime value possible. The larger the possible coprime values, the larger the value of N in Equation 6, and therefore the larger R, as in Equation 10. max The ratio of Δr to Δr increases. Furthermore, the wider the frequency separation, the more accurate the distance resolution. In cases f) and g) of Table 1, the receiver can reliably distinguish 16 phase values ​​within the range of 0 to 2π (e.g., a resolution of 2π / 16 = π / 8) due to favorable channel conditions (high RSSI, proximity to the AN), so a coprime value not exceeding 16 may be used. Compared to case f), case g) achieves 14 times more accurate resolution using a wide frequency separation, at the expense of a 1 / 14 reduction in the maximum achievable distance. Cases d) and e) can be applied to somewhat poor channel conditions (e.g., intermediate distance, substantial interference), so the receiver resolution is π / 4, i.e., a coprime value not exceeding 8 may be used. However, even when the device is in favorable channel conditions, it is not necessary to require a high coprime value; the device may trade distance resolution for additional ranging reliability. On the other hand, if the device lacks any knowledge of the channel conditions or approximate distance, it may require a different parameter set (e.g., a different PRS layer). Finally, another point related to step 1 of the first scheme is that, in particular, Δf min For narrow frequency separations close to ZE modems may have poor phase sensitivity.

[0154] Regarding step 2 of the first scheme, when the AN begins emitting a PRS (or PRS layer), it may transmit i) parameters providing the frequency and time characteristics of the PRS, and / or ii) information that assists the ULP device in making PDOA measurements. These parameters and information may be spectral characteristics such as system bandwidth, minimum frequency spacing, coprime factor, or a list of frequencies used; PRS format in the case of an unmodulated continuous wave set, such as waveform, modulation scheme, bandwidth, and transmission period; and temporal characteristics such as timing of PRS opportunities, duration of PRS opportunities, number of consecutive PRS opportunities, delay between PRS opportunities, total duration of all PRS opportunities, and / or range bin resolution.

[0155] The device receives these PRS resources and their characterizing parameters and subsequently obtains a PDOA estimate for each frequency pair to obtain an approximate distance. If the device needs to further refine the distance estimate, such as by narrowing the resolution, or if the device cannot adequately determine a distance estimate using the existing PRS, it may again transmit a message with its capabilities and resolution requirements, according to step 3 of the first scheme. However, to minimize the length of this message, the message may be transmitted in a differential format that describes only the changes relative to the last request, ΔF, Δf min , Δf min Many of the parameters such as do not need to be updated. Furthermore, some coprime numbers do not change. This may not be the case.

[0156] Referring to FIG. 5, a method 500 according to one of the embodiments is shown. In one exemplary scenario, the method 500 according to the first scheme begins at 502 when a device (e.g., a WTRU or STA) equipped with a ZE receiver reports its ZE modem electronic capabilities and MF-PDOA measurement capabilities along with desired PRS parameters. These parameters may be requested by referencing a specific PRS set ID. Thus, at 502, the device may report its capabilities, receive ZE-related configuration via its primary transceiver, and transition to a ZE air interface. At 504, the device receives PRS resources from the network along with parameters characterizing the PRS. The active PRS received by the device may be a PRS activated by default or may be a PRS activated by another device. At 506, receiving the PRS and parameters enables a determination of whether the PRS is suitable for the device's capabilities and positioning requirements. If it is determined at 506 that the PRS and parameters are appropriate (i.e., match the device's capabilities and / or requirements), the device measures the PDOAs of the available frequency pairs at 512 and combines them to generate a distance estimate at 514. After obtaining the distance estimates, the device may determine the reliability of the PDOAs and the distance estimates at 514. If the device determines at 516 that one or more PDOAs are unreliable, the device proceeds to 508, where it makes another request for the same resources via the same PRS Set ID. It should be understood that a request for PRS resources by a device can be made by referencing a PRS Set ID, which points to the PRS resources and associated parameters being requested, or by referencing a Device ID, which indicates PRS resources and parameters that comply with a particular device. In other words, the device can include a PRS Set ID or a Device ID in the request to request a specific set of PRS resources. If the device performs the request process at 508, the device again receives the PRS resources at 510, measures the PDOAs at 512, and estimates the distance at 514.If the device determines at 516 that the reliability of the PDOA and distance estimates is sufficiently accurate, then at 518 the device can report the distance or location to the network. The device may not communicate its capabilities and desired PRS parameters if they have not changed. The device has the option to combine the new PDOA measurements with the measurements from the second step. If the new distance is very similar to the distance calculated in the second step (one distance bin resolution difference), the device may average the two.

[0157] A device equipped with a ZE receiver may report its electronic capabilities and MF-PDOA measurement capabilities at 502 using one or more of the following parameters: the lowest and highest frequencies supported for CW, which may be expressed in the form of a minimum CW frequency f0 and a total system bandwidth ΔF; the minimum frequency separation of any pair of CWs, regardless of whether there is a minimum difference between the frequencies of all CWs present at any time; support for sequential or co-extended frequency pair configurations; the number of CW pairs or CWs that can be processed simultaneously (CWs processed on a PRS opportunity), where if a co-extended configuration is used, N PDOAs are measured over N+1 CWs and if a sequential configuration is used, N PDOAs can be measured over 2·N pairs; the minimum delay supported between consecutive PRS opportunities, and / or the range of co-prime values ​​supported.

[0158] The desired PRS parameters are the phase sensitivity and observed RSSI; the maximum coprime; and / or the range bin resolution, range accuracy, and / or the desired maximum effective range for each channel condition.

[0159] A PRS Set ID, which refers to a standardized set of electronic and measurement capabilities (and may contain common desired PRS parameters), may be obtained during an attach (LTE) or registration (NR) procedure, or during delivery of a SIB message to a ZE device.

[0160] The PRS parameters that the network transmits at 504 or 510 along with the PRS resources may include the frequency pair configuration, such as sequential or co-expansion; the PRS opportunity, the duration of the PRS opportunity, the number of consecutive PRS opportunities, and / or the delay between PRS opportunities, and / or the resolution distance bin per PRS opportunity, the frequencies used, and their respective co-primes.

[0161] At 516, the device may determine the reliability of the PDOA value by calculating a function (e.g., average, maximum, minimum, ..., etc.) of the RSSI values ​​across all pairs. The device may determine that the average corresponds to three distances: a neighboring cell where the PDOA measurement is reliable (strong RSSI); an intermediate range where a PRS resource retransmission is required to verify the PDOA measurement (average RSSI); and / or a neighborhood edge where multiple (e.g., at least three) PRS retransmissions are required (bad RSSI). The PDOA may be averaged over the values ​​obtained from transmissions and retransmissions.

[0162] The reliability of the PDOA values ​​can be inferred by determining the variance of the PDOA within a range bin common to all frequency pairs and the proximity of any PDOA to the lower or upper limits of the range bin.

[0163] In an alternative exemplary situation of the first scheme, a device equipped with a ZERO receiver may report its capabilities at 502, along with desired PRS parameters or via a specific PRS Set ID, as in the previous example. The device may then receive PRS resources and their characterizing parameters at 504 as in the previous embodiment and proceed to measure PDOA at 512; however, alternatively, due to insufficient RSSI, the device requires a different parameter set at 516 for increased robustness against channel impairments. In this situation, the device makes a request at 508 that points to a different PRS Set ID or includes a differential format that provides only the changed parameters. The device then utilizes the updated PRS resources to perform PDOA measurements at 512 and distance estimation at 514.

[0164] In some cases, the distance estimate and location(s) may be determined within the network. With the goal of keeping the ZE / ULP device modem design as simple and power-efficient as possible, an alternative approach is to forward the PDOA measurements to the network, which may process the PDOA values ​​to determine the distance. The measurements may be provided to the network in a quantized format (e.g., integer + fraction).

[0165] In some cases, the ultimate goal may be positioning rather than just ranging, which requires knowing the distance along with the coordinates of each AN emitting a PRS.

[0166] Upon the end of a PRS transmission from one AN, the network may initiate a scheduled PRS transmission from a different AN (e.g., the device now provides a new set of PDOA measurements). The cycle (which may include, e.g., transmitting a PRS, measuring PDOA, reporting to the network, and calculating distance by the network) may be repeated at least three times until the location of the ULP device is determined.

[0167] In some cases, absolute location may not be required, but rather relative location or distance to as few as two ANs located along a track, route, or mall. At a mall, for example, an end user may need to know the walking minutes or calculated number of steps from a department store. At a running track, an athlete may only need to know how far along the running track they have traveled, not their exact coordinates. In response, the network may direct PRS resources to be transmitted from two or more ANs.

[0168] In the second scheme, there can be multiple PDOAs to increase robustness against noise. In this configuration, additional pairs of CWs are provided, and each additional PDOA on a different frequency is measured to protect against noise rather than to increase distance. That is, any clear effective R is not used to increase the reliability of the distance estimate. max For , many more PDOAs can be measured.

[0169] A device may utilize additional PDOAs(es) in one or more approaches. In a first approach utilizing additional PDOAs(es), a given number of PDOAs ("required PDOAs") may be required to unambiguously determine distance. One additional PDOAs (e.g., for a different frequency pair) may be provided as a check. If the value calculated by the additional PDOAs does not match the distance obtained from the required PDOAs, the device may request a retransmission of the same PRS resource or a change in the required PRS parameters. One option is to combine the value calculated in the initial transmission with the value in the retransmission (e.g., to average out phase noise).

[0170] In a second approach utilizing additional PDOAs, a number of additional PDOAs may be provided (in addition to the "required PDOAs"). The device may follow a selection rule whereby a measurement may be determined to be reliable if a certain number of PDOAs (e.g., more than the number of "required PDOAs") match. An alternative rule may be to ignore different PDOAs if they do not significantly affect the distance (e.g., resulting in the overall distance being one distance bin apart).

[0171] In the third approach, which utilizes additional PDOAs, multiple sets of "essential PDOAs" are provided, each capable of determining distance independently. These two sets are then used to calculate Δr and R. max Two calculations can have the same, similar, or different values ​​for If the calculated distances do not match, the number of mismatched PDOAs can be determined. If there is only one mismatched PDOAs, it can be ignored and the distance can be estimated using the remaining PDOAs. If there are two mismatched PDOAs, but the two distances calculated for the two sets are similar, the average can be estimated. Selection rules can also be followed.

[0172] An example of the third approach for the second scheme of Figure 6. Consider the following sets, each of which can determine a correct distance of approximately 105 m: Essential Set #1 {ξ1=8, ξ2=13, Δf1=34.125, Δf2=21 MHz} 620 and Essential Set #2 {ξ3=3, ξ4=5, ξ5=7, Δf3=91 MHz, Δf4=54.6 MHz, Δf5=39 MHz} 640. Δr=100 m / (7·13)=1.099 m, and the R of Set 1 and Set 2 max are 104·Δr and 105·Δr, respectively. Δr was chosen to allow frequency differences that are multiples of 100 KHz (Set 2) and 125 KHz (Set 1).

[0173] FIG. 6 is a diagram 600 showing an example of estimated PDOA for two essential sets 620, 640. As shown, the PDOA can be shown to vary with different periods. This period is R max,i ξ i For example, if ξ1=8, the period is 8.792 m, which covers a phase variation between 0 and 2π. Within this period, there are ξ1=8 distance bins. Each ξ i The phase measured for corresponds to various distance bins (e.g., period R max,i And the same ξ i (Circle 602 is repeated within the circle). The goal is to find all ξ i The solution may be to find the distance bin that contains the circle 602 for

[0174] In the example of Figure 6, the true distance is expected to be 81.6 m. However, due to an error in the PDOAs for ξ3 = 3 (resulting in different bins for the measured phase), the bottom set (ξ3 = 3, ξ4 = 5, ξ5 = 7) selects a distance of 43.13 m (left line). The top set (ξ1 = 8, ξ2 = 13) correctly selects 81.6 m. However, note that the PDOAs for ξ4 and ξ5 have one distance bin that matches the PDOAs for ξ1 and ξ2. This causes ξ3 to be rejected. Since the distance is selected using these four PDOAs, the estimated distance is 81.6 m. Note also that a simpler method for selecting a distance estimate is, for example, to apply a majority rule to find the distance bin with the majority of PDOAs that match.

[0175] Referring again to FIG. 5, in one exemplary situation, at 502, a device equipped with a ZE modem may signal its ZE modem electronic capabilities and MF-PDOA measurement capabilities using PRS parameters including N required pairs ("mandatory" pairs) and PRS parameters including M "redundant" pairs of frequencies (these pairs together may be longer than R maxIt is reported together with what is called redundant (to bring about). At 504, the device receives PRS resources from the network along with parameters that characterize the PRS for both the essential pair and the M redundant pairs. Note that the received PRS parameters may be different from what was requested, based on the device currently being served by the network. Next, at 512, the device measures the PDOA using the essential pair to obtain an "essential" distance and calculates the PDOA of the redundant pairs. At 514, the device checks whether all of the essential and redundant pairs match, and if there is a selected distance bin for each of the redundant pairs that matches the "essential distance", the estimated distance is declared valid at 516 and the estimation is completed at 518. Otherwise, if the essential and redundant pairs do not match and there is no unique distance bin that matches across all pairs, the device considers the majority principle at 514 to determine the validity of the distance estimate. Thereafter, the device checks whether at least J distance bins (J < M + N) match, and at 514, the device selects the matching distance bins across the J distance bins to determine the final distance estimate. The parameter J may be determined by the device or provided by the network. Alternatively, the device may use (M + N - J) different distance bins (multiple possible) to determine the distance estimate, determine whether it is close to the distance estimate determined by the majority J, and then, at 514, calculate the distance estimate using the weighted average of all M + N selected distance bins. Under the condition that less than J distance bins match, the device repeats the procedure, requests the same or different PRS resources again at 508, and may use the resulting measurements and estimates individually or in combination with previous ones.

[0176] In another example situation, at 502, a ZE-equipped device reports its ZE modem electronic capabilities and MF-PDOA measurement capabilities, along with PRS parameters requesting two sets of "essential" pairs, each of which is sufficient by itself to determine distance. At 504, the device receives PRS resources from the network for both essential pairs, along with parameters characterizing the PRS of both essential pairs. Note that the received PRS parameters may differ from those requested based on the device currently being served by the network. The device then calculates PDOAs at 512 and distance estimates at 514 for these two sets of essential pairs. If the distance estimates match, the measurement is declared complete. If the distances mismatch but only one PDOA does not match, a selection rule is applied and the distance is estimated using the remaining PDOAs (e.g., distance bins are selected to match across all pairs except for the pair that differs). If two PDOAs mismatch but the difference in the resulting estimated distance is small or acceptable, the device may declare the distance estimate as the average of the two. If not, the device repeats the procedure, again requesting the same or different PRS resources at 508, and may utilize the resulting measurements and estimates individually or in combination with previous ones.

[0177] In a complementary configuration, PRS-related information may be exchanged during the attach / registration procedure. In the above scheme, updating the network with WTRU capabilities on the one hand and informing the WTRU about PRS characteristics on the other hand may be a burden for the ULP / ZE device in the UL or DL.

[0178] On the UL of a ULP / ZE device, transmission can occur via normal RF transmission or via UL backscatter (of signals from the network). The former requires modest energy consumption available to the ULP / ZE device (e.g., collected by energy harvesting). Backscattering can result in low data rates, making the ULP / ZE device's UL communication completely dependent on the network. Either technique may be preferable to avoid large data transfers.

[0179] On the DL of ULP / ZE devices, modems have narrow bandwidths and may therefore limit the data rate. Furthermore, processing incoming data incurs power consumption.

[0180] In contrast, the primary modem (i.e., LTE and NR) does not have such a data rate limitation and can therefore be used to expedite part of the procedure so that the PDOA can be measured before the device enters ZE mode.

[0181] One alternative is to determine i) the device's capabilities and needs, and ii) the associated PRS characteristics whenever the primary modem is in the early stages of communication (registration after radio on), the device moves into a tracking area outside the registration area, and / or there is a change in WTRU capabilities (end user switches "ULP / ZE mode support"). These procedures can be conveniently used to convey information necessary for MF-PDOA operation.

[0182] The device's capabilities and needs and its associated PRS characteristic information should already be available / stored in the network and therefore do not need to be exchanged during periodic tracking area updates (e.g., periodic registration updates in NR).

[0183] FIG. 7 illustrates the exchange of PRS-related information during an attach procedure 700. In general, for the attach procedure 700, one or more of the following steps may occur. First, there is an Attach Request (LTE) or Registration Request (NR) message 702, which may include an "ULP / ZE bit" indicating that the device supports ULP / ZE mode / modem (and ULP / ZE positioning). Next, there may be a WTRU Capability Message query (e.g., UE Capability Inquiry) 704 for ZE / ULP capabilities, along with queries for EUTRA, EUTRA-NR, and NR. Next, a WTRU Capability Information message 706 may include information elements (IEs) detailing the ZE / ULP positioning support technologies (MF-PDOA) and their respective RF and baseband capabilities (e.g., co-prime, system BW, etc.), along with desired values ​​for positioning parameters (e.g., resolution). Next, there may be an RRC Connection Reconfiguration (LTE) or RRC Reconfiguration (NR) message 708, which includes IEs characterizing the PRS (e.g., actual frequency, co-prime factor, timing data, etc.). The device may then respond with an RRC connection reconfiguration complete / reject message (LTE) or an RRC connection reconfiguration complete / reject (NR) 710. Finally, there may be an attach complete message 712 from the WTRU primary modem to the network.

[0184] In the RRC Connection Reconfiguration Complete message 710, the network may specify whether the PRS resources are i) always on, ii) available on demand, and / or iii) intermittent according to a specific pattern. Furthermore, the network may specify PRS resources for various ANs so that multiple distances can be calculated. The PRS parameters specified in this message may be for default PRS tiers that can be reconfigured in the WTRU periodically or upon registration, tracking, or RAN notification area change. The configuration may also be provided as a mapping between identifiers and parameter sets, one set for each supported PRS tier.

[0185] Furthermore, the RRC Connection Reconfiguration (LTE) or RRC Reconfiguration (NR) message 708 may contain different sets of PRS resources. When a device enters ULP / ZE mode, it may select one of those sets depending on the channel conditions and location (e.g., outdoors, mall). Furthermore, if none of the sets in the reconfiguration message 708 are applicable to the channel conditions and location, the device may request resources as outlined in the first and second schemes described herein.

[0186] As discussed herein, there may be schemes related to hybrid (MF-) PDOA with path delay measurements. Specifically, these schemes may combine PDOA measurements with timing information. Also, the actual distance of the device to the AN may be determined by the R of the distinct pair of CWs used. max,i If it is larger than , aliasing may occur. This aliasing can be modeled by m (see Equation 3). PDOA cannot unambiguously determine true distance.

[0187] By calculating the PDOA for multiple pairs, the effective R max can be increased, but this value may still be limited and the actual distance may exceed the effective R max However, aliasing may still be present when

[0188] In addition, even if the true distance is max Even when the distance is known to be less than 1 / 2, errors in the measurement of the PDOAs can result in an incorrect range bin determination. Even when immediately adjacent range bins are selected for a PDOAs, large errors in the calculated distance can occur. Solutions include extending the length of time the PDOAs are measured and / or repeating the PRS and each measurement, using pairs necessary to unambiguously determine the distance.

[0189] One alternative is to combine round trip time (RTT) data, such as timing advance (TA) and time of flight (ToF), with PDOA measurements. The PDOA measurements provide precision, while the round trip time data removes ambiguity (e.g., effective R max (Expand R to the possible radius of the cell served by the AN.) If only one CW pair is used, R max,i can be larger than the RTT resolution.

[0190] Furthermore, in the case of multiple pairs, the RTT timing data can serve as a form of redundancy that can help detect errors when, due to adverse channel conditions, one incorrect bin decision causes the MF-PDOA distance estimate to contradict the RTT estimate; for example, see Equation 5, ξ1 = 3, ξ2 = 5. Since the true value of d is 14, the (measured) mod values ​​for d are estimated to be a1 = mod(14,3) = 2, a2 ​​= mod(14,5) = 4. However, due to phase error, the above measurements are 1 and 4. Instead, the computed value of d is 4, with mod(4,3) = 1, mod(4,5) = 4.

[0191] As mentioned above, combining PDOA with RTT measurements can improve maximum range and accuracy, increase versatility, and enhance robustness to channel impairments.

[0192] In one example, there may be a hybrid (MF-)PDOA-TA scheme, which may be the technique(s) for how UL and DL synchronization in LTE and NR is achieved.

[0193] Upon power-up, a device may first attempt system acquisition and DL synchronization via the PSS and SSS synchronization reference signals. This synchronization may be at the received frame, subframe, slot, and / or symbol level and may enable reading of broadcast system messages. Then, after determining the RACH parameters from the system messages, the device may attempt RACH procedures, particularly to achieve UL synchronization.

[0194] UL synchronization may be achieved where the device first transmits RACH MSG1 in the UL according to the timing of the received DL signal. However, there may be a time lag between the transmitted frame (e.g., at the AN) and the received frame (e.g., at the device). d A delay (e.g., equal to distance / c) may occur. The UL signal that is initially synchronized with the received frame may be delayed at the AN by an additional t d The network determines that the RTT=2·t when the device transmits the first RACH MSG1. d and the network determines the 16 T in LTE in RACH MSG2. s It can correspond to TA commands expressed as multiples of T s If the value of the sampling period (e.g., the basic unit in LTE) is defined as 1 / (2048·15 kHz) = 1 / 30720 ms and the RTT is taken into account, the TA command may correspond to a distance granularity of 78.125 m. It may be assumed that the accuracy of the TA command is also 78.125 m, i.e., the TA command specifies a location of 78.125·n ± 39.0625 m. In other words, the size of the TA distance bin (Δr TA ) is 78.125m.

[0195] In NR, the subcarrier spacing (SCS) is in the form of 2µ·15KHz. The TA command granularity may be the same as in LTE, but divided by 2µ. Timing TA commands may be multiples of 64·16·tc / 2µ, where Tc = 1 / (4096·480KHz) = 64·Ts. For an SCS of 15KHz, µ = 0, the distance granularity may be the same as in LTE. However, for an SCS of 30KHz, µ = 1, the distance granularity may be 39.0625m. As an LTE / NR device moves around, the network may subsequently send TA updates (e.g., small delta values) to keep the device's UL timing aligned with the network. In either case, the network may know the total timing advance at any given moment.

[0196] As part of a ULP / ZE device, the request for PRS may include a request for TA. Another option is for the network to automatically provide the timing advance. In either case, the device may combine the TA with the PDOA measurement.

[0197] Depending on the channel conditions, distance value, and supported frequencies, the device may have various PDOA+TA combination options, such as one PDOA+TA, MF-PDOA+TA, and / or TA, to detect MF-PDOA errors.

[0198] For one PDOA+TA option, R max,i is Δr TA The PDOA frequency pair may be selected to be slightly greater than . The PDOA measurement may provide better resolution than the TA, while the TA removes the distance ambiguity.

[0199] FIG. 8 is a graph 800 illustrating an example of phase ambiguity. In this graph, a PDOA measurement yields a possible range of 80 + 150 m. The TA data determines the range to be approximately 664 - 772 m, so m = 4 and the distance is calculated to be 680 m. In this graph, circles 802 indicate the possible ranges determined from the PDOA measurement, while the TA data selects the correct circle mark.

[0200] The actual distance accuracy in this situation may depend on the phase sensitivity: if the device can distinguish between phases by π / 8, meaning the accuracy is about 10 m, i.e. 150 / (16 phase values), the distance is about 680 ± 5 m.

[0201] In the case of the MF-PDOA+TA option, multiple PDOA frequency pairs can be combined with TA, resulting in an effective R max is Δr TA ξ1 = 4, ξ2 = 15, f1 - f0 = 50 MHz, f2 - f0 = 13.333 MHz. A higher resolution than the MF-PDOA+TA option can be obtained, but the TA removes redundancy. For example, for a device supporting a phase resolution of π / 8, the following values ​​are required: ξ1 = 4, ξ2 = 15, f1 - f0 = 50 MHz, f2 - f0 = 13.333 MHz. Δr=1.5m.

[0202] Effective R of MF-PDOA max is 90 m. Thus, a device using this parameter combination may provide maximum range as determined by the TA (cell radius), and with good values ​​of RSSI (e.g., close to the AN), the device may provide a distance resolution of 1.5 m.

[0203] Alternatively, the device may require ξ1=3, ξ2=5, ξ3=8, Δr=1m, f1-f0=100 MHz, f2-f0=60 MHz, f3-f0=37.5 MHz.

[0204] Effective R of MF-PDOA maxis 120 m. The range resolution is 1 m. Using a maximum coprime value of 8 ensures that Δr accounts for at least π / 4 in the PDOA estimate. Thus, with these parameters, the device can tolerate lower values ​​of RSSI than in the previous example.

[0205] 5, in one example situation, at 502, a device equipped with a ZERO receiver reports its ZERO modem electronic capabilities and MF-PDOA measurement capabilities and requests timing advance and PRS parameters with a maximum effective range slightly greater than the timing advance resolution. At 504, the device receives PRS resources, parameters characterizing the PRS resources, and the timing advance. The device then calculates PDOA at 512 and combines them to find a distance estimate at 514. While TA determines a coarse distance bucket, PDOA provides finer distance resolution within the TA distance bucket.

[0206] In a variation of the above example scenario, the device receives a TA value from the serving AN and then uses the TA value to determine an initial distance estimate and corresponding expected RSSI. The device then utilizes the determined RSSI value and initial distance estimate to select and request a specific PRS configuration at 508 that improves accuracy while providing robustness. The requested maximum effective range of the PRS may i) be somewhat greater than the timing advance resolution, or ii) be independent of the timing advance. The device then receives PRS resources from the network at 510, along with parameters characterizing the PRS resources. The device then measures the PDOA of available frequency pairs at 512. In case i), the device measures the PDOA and combines them to find a distance estimate at 514. The TA determines a coarse distance bucket, while the PDOA provides finer distance resolution within the TA distance bucket. In case ii), the device calculates the PDOA and determines a distance estimate using only the TA and validates the distance estimate at 514.

[0207] In the option where a TA is used to detect MF-PDOA errors, the role of the TA is to verify and check the results obtained via MD-PDOA. Figure 9 shows two graphs illustrating an example 900 in which a TA is used to verify the results from an MF-PDOA. In the figure, the calculated total distance for the PDOA using ξ = 3 and ξ = 4, Δr = 50 m is approximately 560 m, which coincides with the selected TA range bin 902.

[0208] Finally, similar to the first scheme, the PDOA measurements can be reported to the network, and the network will perform the distance and positioning calculations. In such a case, the network may not need to share the TA value.

[0209] In one example, there may be a hybrid (MF-) PDOA-ToF scheme. Time-of-Flight (ToF) methods calculate the round-trip time (RTT) of a signal transmitted in one direction and receive a response in the opposite direction. These methods may also account for the processing of received signals, i.e., measuring processing delays. FIG. 10 illustrates an example of the use of timestamps in a hybrid PDOA-ToF scheme 1000. In this figure, timestamps T1 and T4 correspond to the instants at which a signal leaves and arrives at the ULP / ZE antenna 1002, respectively. Meanwhile, timestamps T2 and T3 correspond to the instants at which a signal arrives and leaves the AN antenna 1004.

[0210] The RTT of a wireless signal is RTToF = (T4 - T1) - (T3 - T2). Therefore, the distance is

[0211]

number

[0212] The range accuracy obtained via RTToF may be better than that of the TA scheme described herein, which may allow for the use of coprime numbers, frequencies, and range bin values ​​different from those required by the TA scheme (e.g., to improve PDOA-only performance). For example, if ToF alone allows for 5 m accuracy and the device supports π / 8 phase accuracy, a PDOA value of f1-f0=60 MHz would be R max,i = 5m and achieve a resolution of 0.625m.

[0213] The timestamps in Figure 10 may be calculated when the WTRU sends a request for PRS resources and the network responds with the PRS resources and their characteristics. Parameters T2 and T3, or the quantity T3-T2, may be included in the message containing the characteristics of the PRS resources. If the device provides the network with a PDOAs to perform distance estimation, the device may need to send values ​​of T1 and T4, or the quantity T4-T1, along with the PDOAs.

[0214] Alternatively, if the request for PRS resources is made via backscatter, the network may determine the timestamps of the backscattered signal leaving the AN antenna and the backscattered signal received at the AN antenna. The device may determine the moment the signal arrives at the antenna and the moment the transmitted response leaves the antenna and measure the processing delay. If the network performs the distance estimate, the device may provide the PDOA along with the processing delay.

[0215] In some cases, distance estimation may utilize MF-PDOA with conventional CRS and TRS. Specifically, LTE and NR reference signals may be used instead of or in conjunction with MF-PDOA PRS to obtain multiple PDOA for distance estimation.

[0216] For MF-PDOA over CRS in LTE, the Cell-Specific Reference Signal (CRS) is an essential component of LTE and is always on because it is used for radio resource management (e.g., selection, reselection, handover), channel state information measurements, frequency domain equalization, and digital automatic gain control, frequency and time tracking, and data demodulation.

[0217] Meanwhile, due to the scarcity of unused sub-6 GHz spectrum, NR can share spectrum with LTE through a scheme called Dual-Spectrum Sharing (DSS). DSS requires that data intended for NR devices be rate-matched to nearby always-on LTE signals. As a result, NR devices can detect CRS every NR subframe.

[0218] In one approach, the CRS can be a resource for DL-based ranging / positioning via MF-PDOA as follows.

[0219] The CRS includes subcarrier signals present in all resource blocks (RBs) throughout the entire system bandwidth. If an eNB is using one port, there are two CRS subcarriers per RB, each spaced 90 KHz apart. Therefore, the frequency separation of the subcarriers used for CRS for one port can be expressed in the form 90 n KHz, where n is {1...2 N RB −1}, and N RB is the number of resource blocks in the system bandwidth.

[0220] The CRS is simply modulated with a predetermined length -31 pseudorandom Gold sequence c(n) that the device can generate. For n defined above, the in-phase and quadrature sequences are, respectively,

[0221]

number

[0222] The minimum separation between signals that a device supports for MF-PDOA positioning is Δf min , which may limit the frequency combinations that can be used.

[0223] Assuming the device supports minimum separation, Δf min = 2 MHz, and the system bandwidth ΔF is 20 MHz, so NRB = 100. Δf is a multiple of 1.8 MHz (10 RB). i By using max is 166.67 m (see Equation 11): a) ξ1 = 5, ξ2 = 3, f1 - f0 = 5.4 MHz, f2 - f0 = 9 MHz, Δr = 11.11 m; b) ξ1 = 5, ξ2 = 8, f1 - f0 = 14.4 MHz, f2 - f0 = 9 MHz, Δr = 4.167 m.

[0224] Δf is a multiple of 0.54MHz (3RB) i Using the values ​​below, any set of R max = 555m, yielding: c) ξ1 = 7, ξ2 = 8, f1 - f0 = 4.32 MHz, f2 - f0 = 3.78 MHz, Δr = 9.92 m; d) ξ1 = 15, ξ2 = 14, f1 - f0 = 7.56 MHz, f2 - f0 = 8.1 MHz, Δr = 2.65 m.

[0225] Cases c and d can be used when the device supports phase sensitivities of π / 4 and π / 8, respectively. Alternatively, CRS can be used in conjunction with MF-PDOAs requested by the network to increase the number of PDOAs over different frequency pairs. CRS can also be used in conjunction with RTT timing.

[0226] In the case of two ports, which is a common configuration for 2x2 MIMO, there are four subcarriers per RB, and each subcarrier is 45 kHz apart. However, subcarriers belonging to two different ports can be assumed to belong to different antennas. Therefore, only pairs of subcarriers selected from within the same port may be used, and the available frequency difference remains as above.

[0227] MF-PDOA distance estimates derived from CRS may not be as reliable as those derived from on-demand PRS resources. Because CRS frequencies may not match the device's hardware capabilities, measured PDOA may be prone to error. One example is PDOA measurements that may be contaminated by a reference signal that cannot be adequately filtered out by a bandpass filter within the device.

[0228] For MF-PDOA over TRS in NR, TRS is a type of reference signal that uses CSI-RS resources to enable fine time and frequency tracking at devices. TRS is not always on and is only transmitted along with PDSCH data. However, using process reservation, the network can arbitrarily carve out a PDSCH channel and make it "future-ready". Thus, using reservation, dummy / null data can be transmitted along with the TRS.

[0229] The TRS may have three subcarriers per RB per port in two consecutive slots, with each TRS subcarrier located four subcarriers apart corresponding to 60 and 120 kHz for SCSs of 15 and 30 kHz, respectively. However, unlike the CRS, which may be present in every LTE RB, the periodicity of the TRS is at least 10 ms. During resumption, three subcarriers per RB may be available at least every 10 ms for MF-PDOA measurements. The minimum number of RBs for the TRS is 52. If the SCS is assumed to be 15 kHz and the minimum number of RBs is used for the TRS, the frequency difference available for MF-PDOA is 60 n kHz, where n is {1...(3 52 = 156) - 1}.

[0230] Referring again to FIG. 5 , in one exemplary situation, the device first calculates 512 PDOAs for subcarrier pairs in a CRS or TRS present in the serving AN, and the device uses these PDOAs to find an initial distance estimate 514. While this distance estimate may likely be determined to be unreliable 516 because it may not generally correspond to the device's hardware capabilities, the device may use it in combination with RSSI values ​​for a more targeted / accurate request for PRS resources 508. Thus, the device utilizes the initial estimate to request a specific, customized PRS configuration from the network that matches the initial distance estimate 508. The device receives PRS resources from the network 510, along with the PRS characteristics. The device then measures 512 PDOAs to determine a distance 514. If there is a match with the initial distance, the distance estimation may be declared complete and reported to the network 518. Otherwise, if the estimated distance matches the initial estimate at 516, the device proceeds to 508 where it may request PRS resources again with the same or different parameters. The device then compares the new distance estimate with the previous distance estimate.

[0231] In a differential MF-PDOA scheme, there may be configuration and data transfers occurring between i) a WTRU (e.g., a ZE WTRU) and an AN, and ii) a facilitator (e.g., another WTRU) and an AN. Using the CW pairs and frequency differences of multiple ANs, the differential distance between pairs of ANs, and from there the location of the WTRU, may be calculated.

[0232] Because PDOA is predefined as the "phase difference of a given pair of CWs," a differential MF-PDOA scheme may involve obtaining PDOA for multiple ANs (e.g., to obtain the differential distance between two ANs at once) and for multiple frequency differences (e.g., to increase the maximum unambiguous value of this differential distance). However, instead of an AN, in the examples described herein with reference to baseline differential MF-PDOA and sidelink-supported differential MF-PDOA, a facilitator or another WTRU (in the vicinity of the ZE WTRU) may be used to generate the CW. That is, a nearby facilitator may emit the CW from which the WTRU needs to obtain PDOA. In some cases, a facilitator in the vicinity of the WTRU may be preferable to an AN because many WTRUs cannot detect more than one AN or cannot obtain PDOA using CWs from more than one AN. Additionally / alternatively, this may be done by the AN instead of the WTRU and / or the facilitator.

[0233] The steps to achieve differential distance consist of 1) transmitting a single CW for facilitator discovery and resource selection, 2) facilitator synchronization, and 3) transmitting a pair of CWs (e.g., one pair of CWs per facilitator) for differential MF-PDOA measurements. The order of actions 1) and 2) may be reversed, as facilitator synchronization only needs to precede action 3).

[0234] A network 1100 including an AN 1102 and a select set of facilitators radiating CW is shown in Figure 11. During a facilitator discovery and resource selection stage (which may be referred to as relating to facilitator discovery as discussed herein), each facilitator (e.g., a mobile phone icon) 1104 may transmit a CW 1120 on a predetermined frequency, and any ZE WTRU (IoT icon) 1106 may detect the CW with the intent of discovering the facilitator 1104 with good channel conditions (e.g., between the facilitator 1104 and the ZE device 1106) (channel conditions include path loss / proximity to the ZE WTRU 1106, shadowing, fading) and determine the frequency (and possibly other parameters) that results in the best channel conditions.

[0235] One exemplary approach is for the ZE WTRU 1106 to detect facilitators 1104 radiating at unique fixed frequencies (as in FIG. 11 ) and then rank the detected facilitators according to their RSSI. Some facilitators 1104 in the vicinity of the target ZE WTRU 1106 may not be detected by the ZE WTRU 1106 simply because their signals may “fade out” at the frequency selected for their CW. One remedy is for the facilitator 1104 to transmit CW at multiple frequencies. A more complex approach may then require RSSI measurements for each facilitator and frequency if the facilitator 1104 can step or sweep through frequencies.

[0236] Facilitator synchronization may be achieved from 1) at least two reference CWs ("CW-RS") transmitted from the AN 1102, and 2) each facilitator 1104's knowledge of its respective distance to the AN 1102 (and, potentially, the location of the facilitator 1104). For example, the AN 1102 may emit a CW-RS signal at 900 and 903 MHz, which may then be used to generate a CW at the facilitator 1104 via a frequency synthesizer (e.g., utilizing a frequency multiplier and mixer) at a frequency of 903+3m MHz (m ∈ N). Each CW may then be synchronized with the propagation delay between the AN 1102 and the facilitator 1104, e.g., -mod(d A / c,2π).

[0237] Alternatively, facilitator synchronization can be achieved in one of the following ways (A-D) or a combination thereof: A) AN 1102 transmitting a timing advance command including a value with the time accuracy of the LTE / NR sampling period (e.g., for LTE, T s = 1 / 30.48 MHz). However, this timing advance can be one-way distance (e.g., rather than two-way distance as in LTE / NR) to ensure that the facilitator 1104 signals are transmitted simultaneously (e.g., rather than arriving at the AN at the same time as in LTE / NR). B) High-bandwidth PRS signals for 5G WTRUs, C) GPS positioning, D) Time-Sensitive Networks (TSN) as partial NR Release 16 support for Industrial IoT (IIoT) and URLLC.

[0238] Further details regarding the differential MF-PDOA measurement stage are provided herein.

[0239] In general, the examples discussed herein relating to baseline differential MF-PDOA and sidelink-supported differential MF-PDOA correspond to using differential MF-PDOA for positioning where the resources and configuration used to calculate the position are dynamic, being dynamically selected to exploit the best possible channel conditions to optimize the estimation of the position.

[0240] As shown in FIG. 13, the facilitator discovery stage 1320 may follow a cyclical approach for this scheme, where a period T p Every T1, all facilitators in the cell simultaneously transmit one CW for duration T1, with each facilitator using a different frequency of N at their discretion for the CW. Any ZE WTRU in the area whose location needs to be determined (e.g., by the AN or the ZE WTRU itself) then reports 1322 the frequencies it detects during T1, along with the RSSI for each frequency, to the AN 1328. This occurs when the RSSI exceeds a fixed threshold P d 1328. Upon receipt 1332 of these frequency reports 1200 (shown in FIG. 12), the AN may trace the reported frequencies to the actual facilitator, thereby avoiding the need for the ZE WTRU to report the identity of the facilitator. After a pause or time gap, to receive reports from the ZE WTRU and complete processing 1334 of the measurement report at the AN, the facilitator may then simultaneously transmit CWs for a period T1 using the second of the N frequencies. Again, the ZE WTRU in question may report 1328 the frequencies it can detect along with the RSSI value. There are a total of N such repetitions (e.g., cycles) until all N input frequencies have been cycled through. The system may be configured such that each facilitator measures at least two pairs of CWs (two frequency differences Δf) during the differential MF-PDOA measurement stage 1330. i(one frequency can be reused in the second pair), a minimum value of N=3 may be set. Alternatively, a value of N=3 may correspond to low, mid, and high frequencies within a band / sub-band. Ultimately, a larger value allows for better avoidance of frequency points with deep fades, and frequency points with optimal fading characteristics are selected.

[0241] Another alternative is to simply relax the overall procedure to allow N=1 or N=2 and select a facilitator that can be detected regardless of whether it is detected on those N frequencies (the CW is in a deep fade on the transmitted frequency and therefore is not detected despite being close to the ZE WTRU). Such a procedure (e.g., N=1 or N=2) may be feasible when there is a high density of facilitators throughout the cell (or in the vicinity of the ZE WTRU in question).

[0242] A frequency report 1200, which includes a list with frequencies and RSSIs, may be backscattered to the AN after completion of each or all of the N iterations.

[0243] When listing all N iterations, the frequency report may include an iteration field 1202 containing each of the detected frequencies (and their respective RSSIs expressed as margins above a threshold) for each of the N iterations. Each iteration field may be followed by an empty field 1204, except for the Nth field.

[0244] If the total number of frequencies listed in report 1200 is below a certain target, the AN may instruct the facilitator to repeat the N-cycle facilitator transmission procedure and the ZE WTRU to re-measure at a given lower threshold. From frequency report 1200, the AN can determine the vicinity in which the device is located and therefore instruct a subset of facilitators only in the vicinity of the ZE WTRU to participate in the facilitator discovery procedure 1320 iteration (rather than the entire cell). Alternatively, the AN can skip the iteration but include a CW-RS in the differential MF-PDOA measurement stage 1330.

[0245] After processing 1334 the frequency report 1200, the AN may select a facilitator to transmit CW pairs in the differential MF-PDOA measurement stage and notify the facilitator and the ZE WTRU of the selection, along with the frequencies to be used. At this point, the AN may begin transmitting its CW-RS. These CW references may be used by the facilitator (along with knowledge of the distance to the AN) to synthesize a CW that is synchronized to the AN. The AN may also notify each ZE WTRU of the set of frequency pairs to be used (and the identity of the facilitator, if the ZE WTRU ultimately calculates its position 1336 or traces the measurements on a map of the scene and therefore does not report its position to the AN).

[0246] Subsequently, each facilitator selected by the AN to participate in the differential MF-PDOA measurement stage may transmit its first pair of CWs. The ZE WTRU may take measurements 1338 (sinθ in FIG. 4) of the first set (set s=1) using pairs of CWs from two different facilitators (four CWs total). BA and cosθ BA ) The AN may then instruct each facilitator to transmit a second pair of CWs (with another frequency difference), from which the ZE WTRU obtains a second set of measurements 1338 (set s=2).

[0247] The previous procedure may be repeated to obtain a first and second set of measurements 1338 for a new set (jth set) of facilitators.

[0248] The ZE WTRU may also report 1339 first and second sets of measurements for two (j=2) pairs of facilitators to the AN via backscattering. The AN may then determine the differential distance between the first pair of facilitators, and then the differential distance between the second pair of facilitators. The two differential distances may be used to determine the device's 2-D location 1336. These two pairs of facilitators may or may not reuse one facilitator, resulting in a total of three facilitators (facilitators A and B for the first pair, then facilitators A and C for the second pair) or four facilitators (facilitators A and B, then facilitators C and D), respectively. For 3-D location, measurements from three (j=3) sets of facilitators are required.

[0249] Alternatively, the ZE WTRU may search for the measurements, along with the facilitator's identification, on a map of the scene where the device is present, e.g., a mall, a hospital, a high-rise building, a stadium, etc. The map may be pre-downloaded using a primary transceiver associated with the ZE WTRU (e.g., when the ZE WTRU first enters the scene) 1304. The ZE WTRU may obtain coordinates from the map and report them to the AN.

[0250] Instead of using only a facilitator, the WTRU (or a combination of the WTRU and the facilitator) may also be utilized to determine the 2-D or 3-D location. Furthermore, during the facilitator discovery stage 1320, the WTRU may transmit modulation carriers such as LTE or NR resource blocks in the UL. The transmissions may convey control plane data (e.g., tracking area updates) and / or small user plane data (e.g., battery information, current location, and a flag indicating willingness to participate in a differential MF-PDOA scheme).

[0251] Furthermore, instead of a periodic approach, the ZE WTRU itself may request initiation of the differential MF-PDOA procedure on demand via backscatter. Rather than having persistent periodic CW resources, these resources may be provided semi-persistently. As needed (in the NW or ZE WTRU), the CW resources (and their configuration, such as periodicity) of the facilitator discovery stage may be activated and deactivated.

[0252] In one embodiment 1300, a WTRU may comprise a primary transceiver and a companion ZE receiver (which may be referred to herein as a ZE WTRU) that includes a bank of fixed-frequency MEMS transformers, a bank of tunable MEMS transformers, or a bank of tunable fixed-frequency MEMS transformers. During operation, the ZE WTRU may permanently receive CW using the bank of MEMS transformers. The ZE WTRU may also include energy detection (ED) circuitry, a mixer, a low-pass filter, an arctangent module, and other components. Initially, when the ZE WTRU first enters a scene at 1302, it may download a map of the scene, including the location of the facilitator, at 1304. The ZE WTRU may also receive system parameters and share its capabilities. At 1322, whenever a CW is transmitted, the ZE WTRU may detect the CW via the ED circuitry. When a ZE WTRU needs to determine its location, or is prompted by the AN to determine its location, the ZE WTRU may backscatter 1328 the values ​​of the frequencies it can detect (e.g., each frequency belonging to a different facilitator) along with their respective RSSI values. The actions at 1322 and 1328 may be repeated a total of N times, where N is a known pre-configured system parameter. At 1328, the ZE WTRU may backscatter a frequency report including the frequency and RSSI values ​​for all N steps. At 1332, the ZE WTRU may be informed by the AN of the frequencies of the CWs along with the identities of the facilitators (e.g., all pairs or pairs of facilitators) transmitting the CWs. At 1334, the ZE WTRU may receive a signal for a period TM Listen to CW over a set of pairs of CWs (each pair has the same frequency difference Δf s , where s=1 and belong to different facilitators), and calculate the PDOA for the first set (s=1) of measurements 1338 (the “in-phase” values ​​cosθ BA and the "orthogonal" value sinθ BA ) The ZE WTRU may also share 1339 the measurements 1338 with the AN via backscatter. The ZE WTRU may then repeat the actions at 1332 and be notified of the new CW frequency and associated facilitator identifier. Alternatively, frequencies from the first set 1338 may be reused, but in a different order, to obtain the new frequency difference Δf s (s=2). This may be via the first set of first and third frequencies going to the first facilitator, and so on. The ZE WTRU may then repeat the actions at 1334 for the new CW and obtain measurements 1338 for a second set (s=2) of the same paired facilitator. If the AN requests, the ZE WTRU may provide the second set of measurements 1338. The actions at 1332, 1334, and 1339 may be repeated for the new paired facilitator. Alternatively, the ZE WTRU may trace the first and second sets of measurements 1338 for the first and second paired facilitators to locations in the downloaded map and share the associated coordinates with the AN.

[0253] In yet another embodiment, the facilitator may be equipped with a transmitter capable of emitting a CW at any of the N frequencies at any one time. These CWs may be provided 1) permanently and periodically, or 2) semi-permanently (e.g., resource configurations are activated and deactivated as needed). In a first step, the facilitator (e.g., a ZE WTRU or another WTRU relative to the WTRU in question) may receive a command from the AN to transmit a CW at the first of the N frequencies. Alternatively, the facilitator may receive a command from the AN to transmit a CW at the first of the N frequencies. pIn each step, the facilitator may prepare to start transmitting CWs. In a second step, the facilitator may transmit CWs on the assigned frequency for a period T1. The facilitator may also repeat the second step N-1 times. In a third step, the facilitator may be notified of a pair of CWs that the facilitator needs to transmit. In a fourth step, the facilitator may transmit CWs on the assigned frequency for a period T1. M The third and fourth steps may be repeated at least once for different frequencies and different frequency differences.

[0254] In another embodiment, in a first step, an access node (AN) may instruct a facilitator in its cell area to start transmitting a CW (e.g., permanently and periodically, or semi-periodically and as needed) on a first frequency of N frequencies. In a second step, the AN may instruct any ZE WTRU to report the frequencies it can detect. The first and second steps may be repeated N-1 times in total. In a third step, the AN may process the reports of each ZE WTRU. In a fourth step, the AN may process the reports of each ZE WTRU for a period T M The AN may instruct the facilitator to transmit at a given frequency (e.g., with a given frequency difference) over a given range. The AN may prompt any ZE WTRU to report the measurements made. A fourth step may repeat the third step for a new frequency (e.g., with a new frequency difference). The third and fourth steps may be repeated with the new frequency and new frequency difference. From the ZE WTRU's perspective, a different pair of facilitators may be involved. However, from the AN's perspective, the same facilitator transmits, but the AN may ensure that the transmission is now intended for a different ZE WTRU. In a fifth step, using the measurement reports, the AN may calculate the location of any device or instruct the device to report its location coordinates.

[0255] A ZE WTRU may request partial or full resources with attributes that supplement or replace the attributes in the default resources as disclosed herein. Full resources mean that the resources are sufficient to obtain 2-D (or 3-D) location. Partial resources mean that the resources simply supplement the default resources. Attributes / resources that can be modified for the discovery stage include the frequency, total number of frequencies, and / or threshold for measurement reporting, while for the differential MF-PDOA stage, the attributes / resources that can be modified are the number of frequency pairs, the frequencies of the CWs and their frequency difference, and / or the duration of the CWs.

[0256] In one embodiment, a ZE WTRU that has already received default resources to discover a facilitator and / or determine its own location may request additional resources, including: another threshold for measurement reports; additional CW pairs; and a non-default frequency difference Δf i (e.g., large values ​​or fractional multiples of 1 MHz); for each facilitator pair, additional pairs of CW pairs (additional Δf i using different frequencies); possibly non-default frequencies in other bands or guard bands; increased CW duration; multiple pairs of CWs at once (e.g., the device may take measurements for more than two facilitators at once, e.g., provide measurements for more than two differential distances at once).

[0257] Using backscatter to transmit requests, detection / discovery results, and measurement results from a ZE WTRU to an AN may present issues with distance, reliability, data rate, congestion / contention, and latency. Direct communication between a ZE WTRU and a nearby facilitator, on the other hand, is more robust and versatile, likely resulting in less contention and lower latency. Furthermore, direct ZE WTRU-facilitator communication may help reduce the burden on the AN. More importantly, it may be possible to have a more dynamic and customized ZE-WTRU approach to facilitator, frequency, and other parameter selection, ultimately optimizing differential MF-PDOA measurements. Furthermore, a facilitator may be able to discover a ZE WTRU before the facilitator discovery stage.

[0258] In some scenarios, there may be direct communication between the ZE WTRU and the facilitator / WTRU to select the best CW pair, share configurations / parameters, and improve and share differential MF-PDOA measurements. Direct communication may include backscatter in the UL, sidelink (such as D2D / ProSe and C-V2X) in the DL / UL, a ZE air interface in the DL similar to that used in 802.11ba, or any combination thereof. As discussed herein, the CW pairs and frequency difference Δf of multiple ANs may be used. i Using this, the differential distance and the location of the ZE WTRU can finally be calculated.

[0259] On the other hand, in indoor environments, the channel is generally affected by multipath (LOS and / or reflections), and therefore the PDOAs obtained from a CW are affected by multipath. A CW transmitted through a multipath channel may result in a net CW having an effective amplitude or fading amplitude and an effective delay (e.g., a delay that is the sum of 1) the LOS propagation delay (i.e., distance) and 2) the net effect of multipath delay spread). This amplitude and this effective delay may vary depending on how the individual components of the multipath (e.g., LOS and reflections) add up vectorially (e.g., amplitude and phase), e.g., whether they combine coherently / destructively, constructively, or somewhere in between. As a result, if the option is available, the objective should be to select a frequency that minimizes the delay due to multipath (e.g., the best-case scenario occurs when reflections add up constructively, leaving only the LOS).

[0260] Furthermore, the most accurate differential distance measurement (e.g., precise in accurately estimating the effective delay) may be obtained when multipath components (e.g., LOS and / or reflections) sum coherently or nearly coherently, i.e., at frequencies and locations where fading amplitude is high (e.g., the signal "fades in"). The opposite may be true when fading amplitude is low (when the signal "fades out"). Therefore, selecting a variety / multiple frequencies, especially frequency points that are widely spaced (e.g., separated beyond the coherence bandwidth of the channel), may enable obtaining frequencies that improve the differential distance measurement. Therefore, the CW discovery stage in this approach may also have the objective of selecting frequencies that result in the best fading conditions (e.g., highest amplitude level of the system transfer function), minimum multipath, minimum delay, and / or better differential distance calculation.

[0261] In an embodiment, there may be several approaches that may be utilized to mitigate the effects of multipath when used in conjunction with direct communication between a ZE WTRU and a facilitator.

[0262] In one approach, backscatter (e.g., no modulation) can be used to reflect CW back to the facilitator, which can then estimate the two-way channel multipath and fading conditions for the purpose of selecting the best frequency (e.g., the facilitator makes the decision regarding the suitability of CW, rather than the ZE WTRU). Backscatter can also be used to share measurements with the facilitator. Directional backscatter can be utilized to determine the direction from the ZE WTRU with the best fading conditions or minimum path delay.

[0263] In one approach, a directional or multi-beam antenna in the ZE WTRU can reduce multipath and select the beam that results in the smallest path delay.

[0264] In one approach, the sidelink (LTE or NR based) may be used to share information (e.g., selected frequency, configuration / parameters, measurements) between the ZE WTRU and the facilitator and for communication between the facilitators. Alternatively, information may be conveyed from the facilitator to the ZE WTRU over a ZE air interface similar to that used in 802.11ba.

[0265] In some scenarios, the objective may be to leverage direct ZE WTRU-Facilitator communication to further improve the selection of the best resources and channel conditions to be used for measurements involving differential MF-PDOA, thereby further improving positioning accuracy.

[0266] In a scheme in which facilitators transmit on static frequencies during the discovery stage, each facilitator transmits on one or more frequencies specific to the facilitator. The ZE WTRU may then inform the facilitator via backscatter or over the ZE air interface which facilitator and frequency have been selected. Prior to the discovery stage, the facilitator may backscatter to determine which ZE WTRUs are present. A CW may then be transmitted sequentially from each facilitator that detects the ZE WTRU. The first facilitator transmits CWs sequentially and then queries the ZE WTRU (e.g., via backscatter or sidelink) to report measurements or selected frequencies. The second facilitator then transmits CWs sequentially and performs queries. This procedure may be repeated until all facilitators that have detected the ZE WTRU have been exhausted. The facilitators may share the collected information with the AN. The AN may then begin emitting the CW-RS and organize (e.g., select and configure) the facilitators that will participate in the differential MF-PDOA measurement.

[0267] In a scheme in which the facilitator performs the frequency sweep, the facilitator may have the ability to sweep frequencies across one or more bands (e.g., the ISM bands) or a large portion thereof, so that the ZE WTRUs can determine the frequency with the best channel conditions for each facilitator (e.g., the signal "fades in" as multipath components add constructively).

[0268] The facilitators may perform backscattering to discover nearby ZE WTRUs. The backscatter messages may include the ZE WTRU's identification information. Those facilitators that receive a response from a given ZE WTRU may report this information to the AN. The AN may then manage the order in which the facilitators perform frequency sweeps. After each facilitator completes a frequency sweep, it may query the target ZE WTRU via backscatter or sidelink and report its selected frequency. The frequencies may be provided in order of preference. Alternatively, the frequencies and corresponding RSSI values ​​may be provided. Alternatively, the facilitator may backscatter while covering (e.g., sweeping) different frequencies and measuring the strength and delay of the backscattered signal for each frequency.

[0269] In one scheme, a discrete frequency sweep may be performed (e.g., the facilitator radiates at predetermined discrete frequency values ​​covering a distance, these values ​​being known to the ZE WTRU). Alternatively, a continuous frequency sweep may be performed (e.g., the facilitator radiates CW at gradually varying frequencies, i.e., the "linear frequency chirp" of FIG. 14). In this approach, the determination of the best frequency may be made solely via backscatter. A continuous frequency sweep with backscatter may have the advantage, in some circumstances, that the facilitator can determine the best frequency point not only from a fading perspective, but also from an antenna / RFE response perspective from the device.

[0270] This procedure (e.g., CW frequency sweep followed by interrogation via backscatter or simply CW backscatter) can then be repeated for each facilitator that initially failed to detect backscatter from the ZE WTRU in question, and the information can be shared with the AN, which can organize the facilitators to participate in the differential MF-PDOA measurement.

[0271] In a scheme in which the ZE WTRU performs beam sweeping, the ZE WTRU may use a beam-switched antenna to select or assist in the selection of the beam with the best gain or lowest path delay (e.g., to reduce the effects of multipath). Discovery and PDOA measurements may be performed at the ZE WTRU and reported to the facilitator via backscatter, sidelink, or the ZE air interface. The duration of the CW for discovery, T1, and the PDOA measurement, T M may be increased by a factor equal to the number of beams supported by the ZE WTRU. Alternatively, measurements may be performed at the facilitator via backscatter.

[0272] Each facilitator may have a limited number of frequencies, possibly only one, to use for discovery. For each frequency, the facilitator radiates CW.

[0273] The ZE WTRU may need to inform the facilitator of the number of beams that the facilitator can support.

[0274] In a scheme where there is frequency sweeping and beam sweeping, there may be procedures as discussed herein, e.g., an embodiment associated with the facilitator performs frequency sweeping and the ZE WTRU performs beam sweeping, which are combined so that both sweeping at the facilitator and sweeping at the ZE WTRU are performed during the discovery stage and the measurement stage. Figure 15 shows an example flowchart of frequency and beam sweeping.

[0275] In one embodiment 1500, a ZE WTRU equipped with a bank of MEMS transformers (e.g., density / number and transformer bandwidth to adequately cover a given frequency range) and a multi-directional antenna may persistently listen for CW via one or more receive beams / directions. pIn 1502, the CW is received from the facilitator. Alternatively, the CW may be emitted aperiodically at the request of the ZE WTRU or the facilitator. When a ZE WTRU first arrives at the scene, in 1504, it may use its primary transceiver to obtain a map of the scene, share its ZE WTRU capabilities (e.g., number of beams, time spent per beam, bandwidth, and center frequency of each transformer, number of facilitators the ZE WTRU can simultaneously detect, etc.) with the AN, and receive system parameters (e.g., periodicity, duration of CW used for discovery, discrete or continuous frequency sweep, facilitator or ZE WTRU determining best frequency, and other parameters). Furthermore, as the ZE WTRU roams around the scene and arrives in the vicinity of a different facilitator, it may receive the facilitator's individual system parameters (e.g., via the sidelink or ZE air interface) if they differ from the system parameters shared by the AN. The ZE WTRU device may also provide its identification information to a nearby facilitator (eg, the facilitator may associate with ZE WTRU information previously shared by the AN).

[0276] At 1506, the ZE WTRU may determine that CW radiation (e.g., in the discovery stage) has been initiated either from detection of periodic transmissions or from direct information from a facilitator received over the sidelink or ZE air interface. The ZE WTRU may try a first beam / direction. Radiation may occur sequentially, one facilitator at a time, or from more facilitators. The ZE WTRU may then try the remaining beams before changing the CW frequency. The CW frequency may then be changed, and the ZE WTRU may again try all beams / directions that the ZE WTRU can support. The ZE WTRU may then determine the strongest frequency and beam / direction, or the frequency and beam combination that results in the shortest path, and may record the number of beams per frequency and facilitator identity. At 1510, the ZE WTRU may report the frequency and corresponding RSSI, and possibly the beam / direction, to the facilitator via backscatter or sidelink (e.g., at this point the ZE WTRU may obtain the identity of the facilitator). Then, for a different facilitator, the ZE WTRU may repeat the process for all beams / directions and frequencies, repeating the reporting action. At 1512, via the sidelink or ZE air interface, the ZE WTRU may obtain, for each facilitator used for the measurement stage, the frequency, frequency difference, and possibly the duration and identity / location of the facilitator (e.g., from one facilitator). At 1514, the ZE WTRU may perform measurements using the best beam (e.g., by referencing the number of beams per frequency per facilitator determined in the fourth step) or using all beams. In some cases, the facilitator may request measurements. The device may report back via backscatter or sidelink. The actions of 1512 and 1514 may then be repeated for various frequencies and frequency differences, and for different sets of facilitators.The ZE WTRU may request additional frequencies, frequency differences, additional set(s) of facilitators and take further measurements via the sidelink, backscatter, or ZE air interface at 1516. At 1518, the ZE WTRU may trace all measurements to the previously downloaded map.

[0277] Alternatively, beam and frequency selection in the discovery stage may be performed via backscattering as follows: At 1506, CW may be received from the facilitator for each frequency in sequence. For each frequency, the ZE WTRU may try each beam in sequence. At 1510, the ZE WTRU may not need to report RSSI (e.g., when RSSI is measured at the facilitator) or beam (e.g., when the facilitator infers the beam from the timing of the backscattered CW and possibly from detecting changes in the backscattered RSSI). However, at 1512, the ZE WTRU may receive information regarding the beam to use for each frequency.

[0278] Alternatively, beam and frequency selection in the discovery stage can be performed via continuous frequency sweep backscattering and / or directional backscattering with the ZE WTRU applying beam switching. The ZE WTRU can maintain one beam / direction while receiving a CW at gradually changing frequencies from one facilitator. The ZE device can then receive a retransmission of the same CW from the same facilitator again (e.g., using a different beam / direction). The procedure can then be repeated for a different facilitator.

[0279] In another embodiment, at 1504, the facilitator may receive from the AN the capabilities of ZE WTRUs in its cell area (e.g., capabilities such as supported frequencies, number of beams, and CW measurement duration). The facilitator may then periodically begin transmitting CW from one nearby facilitator at a time at fixed initial discrete frequencies (frequencies that are part of the frequency raster) for a given time period that takes into account the number of beams of the target ZE WTRU, and then observe a short pause. The facilitator may then repeat the CW transmission in a second step on the remaining frequencies in the raster. At 1510, the facilitator may receive a frequency report from the ZE WTRU via backscatter or sidelink, including the frequency, beam, and / or RSSI value. After a short pause, covering all frequencies in the frequency raster, this procedure may be repeated for other nearby facilitators. The facilitator then shares all frequency reports with the AN. At 1512, the facilitator may receive information regarding a schedule of CW frequencies, frequency differences to transmit, and backscattering measurement reports from the ZE WTRU. At 1514, the facilitator may transmit a pair of CWs at the requested frequencies and frequency differences. The facilitator may then backscatter the ZE WTRU and receive the measurement reports. The transmit and backscatter actions may be repeated until all items in the schedule received at 1512 are completed.

[0280] Alternatively, at 1504, the facilitator may use backscatter, where CW is a given frequency and the signal backscattered from the ZE WTRU is measured.

[0281] Alternatively, instead of transmitting a CW at a fixed initial discrete frequency, the facilitator may transmit a linear frequency chirp CW while the device tries one beam / direction, and then the action may be repeated for the remaining beams / directions.

[0282] Alternatively, at 1510, the facilitator may have already been informed of some best frequencies via frequency reports and may therefore re-initiate CW initiation or transmission, but using finer frequency spacing (e.g., an approach that may essentially be referred to as fine frequency selection) to focus the frequency range around those best frequencies.

[0283] In another embodiment, first, at 1504, when an AN first enters a scene, it may receive capability information from the ZE WTRU itself or from other ANs covering the scene, and when the capability information is obtained directly from the ZE WTRU, it may share system information from facilitators in the area with the ZE WTRU. The AN may then distribute the capability information to associated facilitators in the area. The AN then manages / adjusts the order in which associated facilitators transmit. The AN reduces the amount of time any ZE WTRU spends idle waiting for the next CW, while also ensuring that facilitators transmit CWs in parallel only if a certain minimum inter-facilitator distance is met (e.g., ensuring there is no co-channel CW interference). At 1510, the AN may assist in processing frequency reports (e.g., facilitator, frequency, beam) from the ZE WTRUs to determine the frequency and frequency difference used in each ZE WTRU's measurement stage.

[0284] 16, in one embodiment 1600, a ZE WTRU may enter the scene at 1602 and share capabilities with the AN and share system and system configuration information (e.g., including the coordinates of the facilitator) at 1604. The ZE WTRU may then request and receive a request over the sidelink, backscatter, or ZE air interface to obtain its location at 1606. Alternatively, the ZE WTRU may periodically report its location. At 1622, the ZE WTRU may receive a CW at a particular frequency from a facilitator. The ZE WTRU may cycle through the beams and record the best beam for each frequency and facilitator. The actions of 1622 may be repeated for other nearby facilitators (e.g., facilitators that discovered the device via backscatter). At 1628, the ZE WTRU may provide a frequency report 1200 including RSSI values ​​for each frequency and facilitator. At 1632, the ZE WTRU may receive the identities of facilitators that can immediately emit CW pairs and the frequencies of the CWs. At 1634, the device performs a PDOA measurement using a first CW pair (e.g., at a given frequency difference) per facilitator set. The ZE WTRU may repeat performing the PDOA measurement action for a second CW pair (e.g., at a different frequency difference). The ZE WTRU may then repeat the operations of 1634 for a different set of facilitators. At 1638, the ZE WTRU may consolidate and process all current measurements to determine the need for any additional measurements. At 1639, the ZE WTRU may request additional CWs at other frequencies and frequency differences and facilitator sets and repeat the actions of 1632, 1634, and 1638. At 1636, the ZE WTRU may calculate its location using all measurements and coordinates of the facilitators and report the location to the network via the sidelink, backscatter, or ZE air interface.

[0285] In addition to PDOA measurements at a ZE WTRU for a set of facilitators at a time, measurements may be made at the facilitators via backscattering, where one facilitator transmits one or more CWs that are backscattered by the ZE WTRUs and the signals may be received at multiple facilitators.

[0286] For one facilitator, for example, three CWs at the appropriate frequency difference may be backscattered from the ZE WTRU and PDOA measured at the facilitator. CRT and Equation 20 may then be applied to obtain distances less than a specified maximum unambiguous distance. The process may be repeated for other facilitators to obtain additional distances, all together to determine a location.

[0287] Another possibility is for the AN to transmit CW-RS at 900 and 903 MHz, and for one facilitator to transmit CW at 906 and 909 MHz (e.g., with a 3 MHz frequency difference). The backscattered signals can be received at the source facilitator and at neighboring facilitators. A differential distance can be obtained at each facilitator by utilizing the received signal along with the CW-RS (e.g., adjusted for delay to the AN) and comparing the results from one facilitator with the results from another facilitator.

[0288] Although features and elements are described above in particular combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with the other features and elements. Furthermore, the methods described herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A method performed by a wireless transceiver unit (WTRU), Receiving continuous waves (CW) transmitted at different frequencies from multiple facilitators, To report the frequency of the received CW signal to the access node (AN), An indication that identifies at least two facilitators selected to participate in the differential MF-PDOA (multi-frequency phase difference of arrival) measurement stage, and their respective operating frequencies, are received from the AN. To receive a first CW pair having a first frequency difference and a second CW pair having a second frequency difference from each of the at least two facilitators, Based on the first and second CW pairs, a set of first and second differential phase measurement values ​​is determined, The position of the WTRU is determined based on the differential range derived from the first and second sets of differential phase measurements, Methods that include...

2. The method according to claim 1, wherein each facilitator transmits one CW signal at a time, and each facilitator uses a different frequency from a set of N frequencies.

3. The method according to claim 1, wherein reporting the frequency of the received CW includes reporting the respective RSSI (received signal strength indication) values ​​associated with the frequency.

4. The method according to claim 3, wherein reporting the frequencies includes reporting only frequencies in which the RSSI exceeds a threshold.

5. The method according to claim 1, further comprising receiving multiple CW signals at different frequencies from at least one of the multiple facilitators over multiple iterations.

6. The method according to claim 1, wherein receiving an indication that identifies the at least two facilitators includes receiving identification information of the at least two facilitators and corresponding frequencies used in the differential MF-PDOA measurement stage.

7. The method according to claim 1, wherein determining the first and second sets of differential phase measurements includes obtaining in-phase and quadrature measurements for each CW pair.

8. The method according to claim 1, wherein the first CW pair and the second CW pair are associated with two different frequency differences.

9. The method according to claim 1, further comprising repeatedly receiving a CW pair and determining differential phase measurements of different pairs of facilitators.

10. The method according to claim 1, wherein determining the position includes determining the two-dimensional position of the WTRU using a differential range obtained from two sets of facilitators.

11. A wireless transceiver unit (WTRU), Processor and Main transceiver and Zero-energy (ZE) transceivers, Equipped with, The processor and ZE transceiver are configured to receive continuous waves (CW) transmitted at different frequencies from multiple facilitators. The processor and main transceiver are configured to report the received CW frequency to the access node (AN). The processor and main transceiver are configured to receive from the AN an indication that identifies at least two facilitators selected to participate in the differential MF-PDOA (multi-frequency phase difference of arrival) measurement stage, and their respective operating frequencies. The processor and ZE transceiver are configured to receive a first CW pair having a first frequency difference and a second CW pair having a second frequency difference from each of the at least two facilitators. The processor is configured to determine a set of first and second differential phase measurements based on the first and second CW pairs. The processor is configured to determine the position of the WTRU based on the differential range derived from the first and second sets of differential phase measurements. WTRU.

12. The WTRU according to claim 11, wherein each facilitator transmits one CW signal at a time, and each facilitator uses a different frequency from a set of N frequencies.

13. The WTRU according to claim 11, wherein the processor and main transceiver are further configured to report the frequency of the received CW by reporting the respective RSSI (received signal strength indication) values ​​associated with the frequency.

14. The WTRU according to claim 13, wherein reporting the aforementioned frequencies includes reporting only frequencies in which the RSSI exceeds a threshold.

15. The WTRU according to claim 11, wherein the processor and ZE transceiver are further configured to receive a plurality of CWs at different frequencies from at least one of the plurality of facilitators over a plurality of iterations.

16. The WTRU according to claim 11, wherein the indication for identifying the at least two facilitators includes identification information for the at least two facilitators and corresponding frequencies used in the differential MF-PDOA measurement step.

17. The WTRU according to claim 11, wherein the processor is further configured to determine the first and second sets of differential phase measurements by acquiring in-phase and quadrature measurements of each CW pair.

18. The WTRU according to claim 11, wherein the first CW pair and the second CW pair are associated with two different frequency differences.

19. The WTRU according to claim 11, wherein the processor and ZE transceiver are further configured to repeatedly receive CW pairs and determine differential phase measurements of different facilitator pairs.

20. The WTRU according to claim 11, wherein the processor is further configured to determine the position of the WTRU by determining the two-dimensional position of the WTRU using a differential range obtained from two sets of facilitators.

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