Method, system and apparatus for low power mode cooperative synchronization

Abstract

Some embodiments of the present disclosure relate to the use of chirp signals in synchronization procedures in wireless communication systems. The synchronization chirp signal is received and processed by a user equipment (UE) in a low power mode for synchronization purposes. The use of the synchronization chirp signal allows for low-complexity processing in the radio frequency (RF) analog domain. Processing in the RF analog domain is known to reduce power consumption relative to processing in the baseband digital domain. Reducing beam sweeping at the UE can also be shown to reduce power consumption and processing complexity at the UE. After the UE interacts with a device transmitting a synchronization signal, the device transmitting the synchronization signal can report measurements to the network. As a result of receiving the measurement report, the network can estimate the timing advance of the UE.

Description

[Technical Field]

[0001] The present disclosure relates generally to wireless communications, and in particular embodiments to synchronization between devices in a wireless communications network, and even more particularly to cooperative synchronization for devices operating in low power modes. [Background technology]

[0002] The known fifth generation (5G) New Radio (NR) mobile radio communications standard includes definitions of operational "states" or "modes" in which a user equipment (UE) may operate. When the UE is operating in one of these two states, one of which is referred to as "IDLE" and the other of which is referred to as "INACTIVE," the UE may be understood to be operating in a low power mode. In each of these two states, the UE turns off circuitry that is deemed unnecessary. Turning off such circuitry may be indicated to gracefully allow the UE to reduce power consumption. In contrast, the UE may also operate in a "connected" state, where power consumption is less of a concern.

[0003] The sixth generation (6G) mobile radio communication standard is currently under development. Given the success of low power modes for UEs compliant with the 5G NR standard, it is expected that similar low power modes will become part of the 6G standard. Furthermore, it is likely that new low power modes will be defined in the 6G standard. It may be expected that at least some of the new low power modes will have even stricter power consumption constraints than the low power modes defined in the 5G standard. In particular, it should be understood that the terms "state" and "mode" may be used interchangeably without changing the meaning of the underlying operation of the device.

[0004] Generally, when a device is configured to operate in a low-power mode, device operation in the so-called radio frequency (RF) analog domain is preferred. Digital processing circuits are known to consume relatively high power, especially when the digital processing circuits operate at relatively high frequencies. Among known digital processing circuits enabling digital processing, analog-to-digital converters (ADCs) are known to be particularly contributors to power consumption. Summary of the Invention

[0005] Some embodiments of the present disclosure relate to the use of chirp signals in synchronization procedures. Chirp signals can be received and processed by a UE in a low-power mode for synchronization purposes. The use of chirp signals allows for low-complexity processing in the RF analog domain. Processing in the RF analog domain is known to reduce power consumption over processing in the baseband digital domain. Benefits can be realized by transmitting chirp signals from devices in close proximity to the UE. Proximate devices have minimal time-of-flight, allowing for relatively accurate estimation of synchronization offsets. Using proximate devices to transmit chirp signals also allows for reuse of time-frequency resources for synchronization within a given network. Reducing beam sweeping at the UE can also be demonstrated to reduce power consumption and processing complexity at the UE. After the UE interacts with a device transmitting a synchronization signal, the device transmitting the synchronization signal can report measurements to the network. As a result, the network may be able to estimate the UE's timing advance.

[0006] Conventional synchronization techniques are known to involve beam sweeping and baseband digital processing, both of which are known to be power consuming.

[0007] Aspects of the present application are characterized by relatively low power consumption. The relatively low power consumption is achieved by performing most of the processing in the RF analog domain and by using proximity to mitigate the need for beam sweeping. Advantageously, aspects of the present application can be shown to achieve relatively low complexity and relatively high accuracy for synchronization offset estimation. Further advantageously, aspects of the present application can be shown to provide the potential for UE multiplexing with relatively low time-frequency resource overhead.

[0008] According to one aspect of the present disclosure, there is provided a method performed on a first device, the method including receiving a chirp signal configuration, the chirp signal configuration including configuration information for a first chirp signal, receiving the chirp signal configuration while the first device is in a low power operating mode, the chirp signal configuration including the configuration information for the first chirp signal from a second device, performing measurements on the first chirp signal to obtain an estimated synchronization offset between a first clock on the first device and a second clock on the second device, and correcting the first clock based on the estimated synchronization offset.

[0009] According to one aspect of the present disclosure, a first device is provided, the first device including a receiver adapted to receive a first clock and a chirp signal configuration including configuration information for the first chirp signal, and to receive the first chirp signal from a second device. The first device further includes a memory storing instructions and a processor configured to execute the instructions while the first device is in a low power operating mode to perform measurements on the first chirp signal to obtain an estimated synchronization offset between the first clock and a second clock at the second device, and to modify the first clock based on the estimated synchronization offset.

[0010] According to one aspect of the present disclosure, there is provided a method, executed in a first device, comprising receiving a chirp signal configuration, the chirp signal configuration including configuration information for a first chirp signal, receiving the chirp signal configuration while a second device is in a low power operating mode, the chirp signal configuration including the configuration information for the first chirp signal, transmitting the first chirp signal to the second device according to the configuration information for the first chirp signal, receiving a second chirp signal from the second device, obtaining measurements on the second chirp signal to determine that the second chirp signal is intended for the first device, and transmitting a measurement report based on the measurements on the second chirp signal to a third device.

[0011] According to one aspect of the present disclosure, a first device is provided, including a receiver adapted to receive a chirp signal configuration including configuration information for a first chirp signal and to receive a second chirp signal from a second device. The first device further includes a transmitter adapted to transmit the first chirp signal to the second device in accordance with the configuration information for the first chirp signal while the second device is in a low-power operating mode, a memory storing instructions, and a processor configured to execute the instructions while the second device is in the low-power operating mode to obtain measurements on the second chirp signal and determine that the second chirp signal is intended for the first device, and to transmit a measurement report using the transmitter to a third device based on the measurements on the second chirp signal.

[0012] According to one aspect of the present disclosure, there is provided a method, the method including transmitting, at a first device, configuration details of a first chirp signal to a second device before the second device enters a low power mode, transmitting configuration details of the second chirp signal to a third device, receiving a report from the third device including measurements made at the third device on the first chirp signal, and processing the measurements.

[0013] According to one aspect of the present disclosure, there is provided a first device including a transmitter adapted to transmit configuration details of a first chirp signal to a second device and to transmit configuration details of a second chirp signal to a third device before the second device enters a low power mode, the first device further including a receiver adapted to receive a report from the third device including measurements made at the third device on the first chirp signal, a memory storing instructions, and a processor adapted to process the measurements by executing the instructions.

[0014] According to one aspect of the present disclosure, there is provided a system comprising a first device and a second device. The first device is configured to transmit a first chirp signal. The second device is configured to receive the first chirp signal and obtain an estimated synchronization offset between a first clock at the first device and a second clock at the second device. The second device is further configured to transmit a second chirp signal to the first device to indicate an association between the first device and the second device. [Brief explanation of the drawings]

[0015] For a more complete understanding of the present embodiments and their advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:

[0016] [Figure 1] 1 illustrates, in a schematic diagram, a communication system in which embodiments of the present disclosure may be implemented, including a number of exemplary electronic devices and a number of exemplary transmission and reception points along with various networks.

[0017] [Figure 2] 2 illustrates in block diagram form the communication system of FIG. 1 including a number of exemplary electronic devices, exemplary terrestrial transmitting and receiving points, and exemplary non-terrestrial transmitting and receiving points along with various networks.

[0018] [Figure 3] 3 illustrates, as block diagrams, elements of the exemplary electronic device of FIG. 2, elements of the exemplary terrestrial transmitting / receiving point of FIG. 2, and elements of the exemplary non-terrestrial transmitting / receiving point of FIG. 2, according to aspects of the present application.

[0019] [Figure 4] 1 illustrates, as block diagrams, various modules that may be included in an exemplary electronic device, an exemplary terrestrial transmission / reception point, and an exemplary non-terrestrial transmission / reception point, in accordance with aspects of the present application.

[0020] [Figure 5] 1 illustrates a block diagram of a detection management function according to an aspect of the present application.

[0021] [Figure 6] 1 illustrates a known structure of a synchronization signal (SS) block having four orthogonal frequency division multiplexing (OFDM) symbols.

[0022] [Figure 7] 1 illustrates a known scheme for facilitating synchronization by transmitting SS blocks in different directions using different beams at different times.

[0023] [Figure 8] 1 illustrates the known structure of a sidelink SS block for regular cyclic prefix OFDM.

[0024] [Figure 9] 1 illustrates an example network including a plurality of user equipments (UEs), including a leader UE and a target UE, associated with a transmission / reception point (TRP), according to an aspect of the present application.

[0025] [Figure 10] 10 illustrates an access chirp signal transmission by a target UE in the exemplary network illustrated in FIG. 9 according to an embodiment of the present application.

[0026] [Figure 11] 1 illustrates exemplary steps of a method performed by a target UE according to an aspect of the present application.

[0027] [Figure 12] 1 illustrates exemplary steps of a method performed by a leader UE according to an aspect of the present application.

[0028] [Figure 13] 1 illustrates exemplary steps of a method performed by a TRP according to an embodiment of the present application.

[0029] [Figure 14] The frequency versus time plot shows how the four synchronous chirp signal configuration parameters affect the synchronous chirp signal.

[0030] [Figure 15] Additionally, frequency versus time plots are provided to illustrate how two synchronous chirp signal configuration parameters affect multiple synchronous chirp signals.

[0031] [Figure 16] 1 illustrates a first case in which a starting frequency is used to distinguish between a first synchronization chirp signal transmitted by a first reader UE and a second synchronization chirp signal transmitted by a second reader UE, according to an embodiment of the present application.

[0032] [Figure 17] 1 illustrates a second case in accordance with an aspect of the present application where both a start frequency and a start time are used, and the start time is used to distinguish between a first synchronization chirp signal transmitted by a first reader UE and a second synchronization chirp signal transmitted by a second reader UE.

[0033] [Figure 18]10 illustrates a third case in which both the start frequency and start time are used to distinguish between a first synchronization chirp signal transmitted by a first reader UE and a second synchronization chirp signal transmitted by a second reader UE, according to an aspect of the present application.

[0034] [Figure 19] An example is shown where there are two leader UEs close to a target UE in low power mode.

[0035] [Figure 20] 1 illustrates the basic structure of two leader UEs and a target UE (the basic structure of the target UE includes a matched filter and a peak detector) and a representation of a synchronization chirp signal according to an embodiment of the present application.

[0036] [Figure 21] 21 illustrates an exemplary envelope of the output of the matched filter in FIG. 20 according to an embodiment of the present application.

[0037] [Figure 22] 1 illustrates steps in an exemplary method for processing a received synchronous chirp signal, according to an aspect of the present application.

[0038] [Figure 23] 1 illustrates exemplary steps in a method of operation of a given leader UE with respect to access chirp signals, according to an aspect of the present application.

[0039] [Figure 24] 1 illustrates transmission of an access chirp signal at a specific chirp rate, a specific start frequency, and a specific start time, in accordance with an aspect of the present application.

[0040] [Figure 25] 1 illustrates a TRP, a target UE, and a leader UE with which the target UE is associated, according to an aspect of the present application.

[0041] [Figure 26]1 illustrates a signal flow diagram of interactions between a leader UE, a TRP, and a target UE according to an aspect of the present application.

[0042] [Figure 27] A linear model of the synchronization offset is shown with two model parameters. DETAILED DESCRIPTION OF THE INVENTION

[0043] For purposes of illustration, certain exemplary embodiments will now be described in more detail in conjunction with the drawings.

[0044] The embodiments described herein represent sufficient information to practice the claimed subject matter and show how to practice such subject matter. Upon reading the following description in light of the accompanying drawings, one skilled in the art will understand the concepts of the claimed subject matter and will recognize applications of these concepts not specifically addressed herein. It is understood that these concepts and applications are included within the scope of this disclosure and the appended claims.

[0045] Additionally, it will be understood that any module, component, or device disclosed herein that executes instructions may include or otherwise have access to one or more non-transitory computer / processor-readable storage media for storage of information such as computer / processor-readable instructions, data structures, program modules, and / or other data. A non-exhaustive list of examples of non-transitory computer / processor-readable storage media includes magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, compact disk read-only memory (CD-ROM), digital video disk or digital versatile disk (i.e., DVD), optical disk such as Blu-ray® disk or other optical storage, volatile and non-volatile removable and non-removable media implemented in any manner or technology, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, or other memory technology. Any such non-transitory computer / processor storage media may be part of the device or may be accessible or connectable to it. Computer / processor readable / executable instructions for implementing the applications or modules described herein may be stored or otherwise carried by such non-transitory computer / processor readable storage media.

[0046] Referring to Figure 1, a simplified schematic diagram of a communication system is provided by way of illustrative example and not limitation. Communication system 100 includes a radio access network 120. Radio access network 120 may be a next-generation (e.g., sixth-generation "6G" or later) radio access network or a legacy (e.g., 5G, 4G, 3G, or 2G) radio access network. One or more communication electrical devices (EDs) 110a, 110b, 110c, 110d, 110e, 110f, 110g, 110h, 110i, and 110j (collectively referred to as 110) may be interconnected to each other within radio access network 120 or to one or more network nodes (collectively referred to as 170a, 170b, and 170). A core network 130 may be part of the communication system and may be dependent on or independent of the radio access technology used within communication system 100. The communication system 100 also includes a public switched telephone network (PSTN) 140 , the Internet 150 , and other networks 160 .

[0047] FIG. 2 illustrates an exemplary communication system 100. Generally, the communication system 100 enables multiple wireless or wired elements to communicate data and other content. The purpose of the communication system 100 may be to provide content such as voice, data, video, and / or text via broadcast, multicast, unicast, and the like. The communication system 100 may operate by sharing resources, such as carrier spectrum bandwidth, among its components. The communication system 100 may include terrestrial and / or non-terrestrial communication systems. The communication system 100 may provide a wide range of communication services and applications (e.g., Earth monitoring, remote sensing, passive detection and positioning, navigation and tracking, autonomous delivery and mobility, and the like). The communication system 100 may provide high availability and robustness through the interoperation of terrestrial and non-terrestrial communication systems. For example, the integration of non-terrestrial communication systems (or components thereof) into terrestrial communication systems can result in what may be considered a heterogeneous network with multiple layers. Compared to traditional communication networks, heterogeneous networks may achieve better overall performance through efficient multi-link cooperative operation, more flexible function sharing, and faster physical layer link switching between terrestrial and non-terrestrial networks.

[0048] The terrestrial and non-terrestrial communication systems may be considered subsystems of a communication system. In the example shown in Figure 2, the communication system 100 includes electronic devices (EDs) 110a, 110b, 110c, and 110d (collectively referred to as EDs 110), radio access networks (RANs) 120a and 120b, a non-terrestrial communication network 120c, a core network 130, a public switched telephone network (PSTN) 140, the Internet 150, and other networks 160. The RANs 120a and 120b include respective base stations (BSs) 170a and 170b, which may be collectively referred to as terrestrial transmission / reception points (T-TRPs) 170a and 170b. The non-terrestrial communication network 120c includes an access node 172, which may be collectively referred to as a non-terrestrial transmission / reception point (NT-TRP) 172.

[0049] Any of the EDs 110 may alternatively or additionally be configured to interface with, access, or communicate with any of the T-TRPs 170a, 170b, and NT-TRPs 172, the Internet 150, the core network 130, the PSTN 140, other networks 160, or any combination of the foregoing. In some examples, the ED 110a may communicate uplink and / or downlink transmissions with the T-TRP 170a via a terrestrial air interface 190a. In some examples, the EDs 110a, 110b, 110c, and 110d may also communicate directly with each other via one or more sidelink air interfaces 190b. In some examples, the ED 110d may communicate uplink and / or downlink transmissions with the NT-TRP 172 via a non-terrestrial air interface 190c.

[0050] Air interfaces 190a and 190b may use similar communication technologies, such as any suitable radio access technology. For example, communication system 100 may implement one or more channel access methods in air interfaces 190a and 190b, such as code division multiple access (CDMA), spatial division multiple access (SDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), or direct frontier transform spread OFDMA (DFT-OFDMA). Air interfaces 190a and 190b may utilize other higher-dimensional signal spaces, which may involve combinations of orthogonal and / or non-orthogonal dimensions.

[0051] The non-terrestrial air interface 190c may enable communication between the EDs 110d and one or more NT-TRPs 172 via a wireless link or simply a link. In some examples, the link is a dedicated connection for unicast transmission, a connection for broadcast transmission, or a connection for multicast transmission between a group of EDs 110d and one or more NT-TRPs 175.

[0052] The RANs 120a and 120b communicate with the core network 130 to provide various services, such as voice, data, and other services, to the EDs 110a, 110b, and 110c. The RANs 120a and 120b and / or the core network 130 may communicate directly or indirectly with one or more other RANs (not shown), which may or may not be served directly by the core network 130 and which may or may not use the same radio access technology as the RAN 120a, RAN 120b, or both. The core network 130 may also serve as a gateway access between (i) the RANs 120a and 120b or the EDs 110a, 110b, and 110c, or both, and (ii) other networks (such as the PSTN 140, the Internet 150, and other networks 160). Additionally, some or all of the EDs 110a, 110b, and 110c may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies and / or protocols. Instead of (or in addition to) wireless communication, the EDs 110a, 110b, and 110c may communicate via wired communication channels to a service provider or switch (not shown) and the Internet 150. The PSTN 140 may include a circuit-switched telephone network for providing plain old telephone service (POTS). The Internet 150 may include a network of computers and / or subnets (intranets) and may incorporate protocols such as Internet Protocol (IP), Transmission Control Protocol (TCP), and User Datagram Protocol (UDP). The EDs 110a, 110b, and 110c may be multimode devices capable of operation with multiple wireless access technologies and may incorporate multiple transceivers necessary to support such.

[0053] 3 shows another example of the ED 110 and the base stations 170a, 170b, and / or 170c. The ED 110 is used to connect people, objects, machines, etc. The ED 110 can be widely used in various scenarios, such as cellular communication, device-to-device (D2D), vehicle-to-everything (V2X), peer-to-peer (P2P), machine-to-machine (M2M), machine-type communication (MTC), Internet of Things (IoT), virtual reality (VR), augmented reality (AR), mixed reality (MR), metaverse, digital twin, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearable, smart transportation, smart city, drone, robot, remote sensing, passive sensing, positioning, navigation and tracking, autonomous delivery and mobility, etc.

[0054] Each ED 110 represents any suitable end-user device for wireless operation and may include (or be referred to as) a device such as a user equipment / device (UE), a wireless transmit / receive unit (WTRU), a mobile station, a fixed or mobile subscriber unit, a cell phone, a station (STA), a machine-type communication (MTC) device, a personal digital assistant (PDA), a smartphone, a laptop, a computer, a tablet, a wireless sensor, a home electronic device, a watch, a head-mounted device, a wearable device such as glasses, a smartbook, a vehicle, a car, a truck, a bus, a train, or an IoT device, an industrial device, or an apparatus (e.g., a communication module, a modem, or a chip) within the aforementioned devices, among other possibilities. Future generations of EDs 110 may be referred to using other terms. Base stations 170a and 170b, each a T-TRP, are hereinafter referred to as T-TRP 170. As also shown in FIG. 3, an NT-TRP is hereinafter referred to as NT-TRP 172. Each ED110 connected to the T-TRP170 and / or NT-TRP172 may be dynamically or semi-statically turned on (i.e., established, activated, or enabled), turned off (i.e., released, deactivated, or disabled), and / or configured in response to one or both of connection availability and connection need.

[0055] The ED 110 includes a transmitter 201 and a receiver 203 coupled to one or more antennas 204. Only one antenna 204 is shown. One, some, or all of the antennas 204 may alternatively be panels. The transmitter 201 and receiver 203 may be integrated, for example, as a transceiver. The transceiver is configured to modulate data or other content for transmission by at least one antenna 204 or a network interface controller (NIC). The transceiver may also be configured to demodulate data or other content received by at least one antenna 204. Each transceiver includes any suitable structure for generating signals for wireless or wired transmission and / or for processing signals received wirelessly or wired. Each antenna 204 includes any suitable structure for transmitting and / or receiving wireless or wired signals.

[0056] The ED 110 includes at least one memory 208. The memory 208 stores instructions and data used, generated, or collected by the ED 110. For example, the memory 208 may store software instructions or modules configured to implement some or all of the functions and / or embodiments described herein and executed by one or more processing units (e.g., processor 210). Each memory 208 includes any suitable volatile and / or non-volatile storage and retrieval device. Any suitable type of memory may be used, such as, for example, random access memory (RAM), read-only memory (ROM), hard disk, optical disk, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and on-processor cache.

[0057] ED 110 may further include one or more input / output devices (not shown) or interfaces (such as a wired interface to Internet 150 in FIG. 1 ). The input / output devices enable interaction with a user or other devices in a network. Each input / output device includes any suitable structure, including network interface communication, for providing information to or receiving information from a user, for example, through operation as a speaker, microphone, keypad, keyboard, display, or touchscreen.

[0058] The ED 110 includes a processor 210 for performing operations, including operations related to preparing a transmission for uplink transmission to the NT-TRP 172 and / or the T-TRP 170, operations related to processing a downlink transmission received from the NT-TRP 172 and / or the T-TRP 170, and operations related to processing a sidelink transmission to or from another ED 110. Processing operations related to preparing a transmission for uplink transmission may include operations such as encoding, modulation, transmit beamforming, and generating symbols for transmission. Processing operations related to processing a downlink transmission may include operations such as receive beamforming, demodulation, and decoding received symbols. Depending on the embodiment, the downlink transmission may be received by the receiver 203, possibly using receive beamforming, and the processor 210 may extract signaling from the downlink transmission (e.g., by detecting and / or decoding the signaling). One example of signaling may be a reference signal transmitted by the NT-TRP 172 and / or the T-TRP 170. In some embodiments, processor 210 implements transmit beamforming and / or receive beamforming based on beam direction indications, e.g., beam angle information (BAI), received from T-TRP 170. In some embodiments, processor 210 may perform operations related to network access (e.g., initial access) and / or downlink synchronization, e.g., detecting synchronization sequences, decoding and obtaining system information, etc. In some embodiments, processor 210 may perform channel estimation, e.g., using reference signals received from NT-TRP 172 and / or T-TRP 170.

[0059] Although not shown, the processor 210 may form part of the transmitter 201 and / or part of the receiver 203. Although not shown, the memory 208 may form part of the processor 210.

[0060] The processor 210, the processing components of the transmitter 201, and the processing components of the receiver 203 may each be implemented by one or more of the same or different processors configured to execute instructions stored in a memory (e.g., memory 208). Alternatively, some or all of the processor 210, the processing components of the transmitter 201, and the processing components of the receiver 203 may each be implemented using special purpose circuitry, such as a programmed field programmable gate array (FPGA), a central processing unit (CPU), a graphics processing unit (GPU), or an application specific integrated circuit (ASIC).

[0061] In some implementations, the T-TRP 170 may be known by other names, such as a base station, base transceiver station (BTS), radio base station, network node, network device, network-side device, transmitting / receiving node, Node B, evolved Node B (eNodeB or eNB), Home eNodeB, next-generation Node B (gNB), transmission point (TP), site controller, access point (AP), wireless router, relay station, remote radio head, terrestrial node, terrestrial network device, terrestrial base station, baseband unit (BBU), remote radio unit (RRU), active antenna unit (AAU), remote radio head (RRH), central unit (CU), distributed unit (DU), positioning node, among other possibilities. The T-TRP 170 may be a macro BS, pico BS, relay node, or donor node, or a combination thereof. The T-TRP 170 may refer to any of the above devices or to a unit within any of the above devices (e.g., a communication module, a modem, or a chip).

[0062] In some embodiments, parts of the T-TRP 170 may be distributed. For example, some of the modules of the T-TRP 170 may be located far away from the equipment housing the antenna 256 for the T-TRP 170 and may be coupled to the equipment housing the antenna 256 via a communications link (not shown), such as a Common Public Radio Interface (CPRI), sometimes known as fronthaul. Thus, in some embodiments, the term T-TRP 170 may also refer to network-side modules that perform processing operations such as determining the location of the ED 110, resource allocation (scheduling), message generation, and encoding / decoding, but that are not necessarily part of the equipment housing the antenna 256 of the T-TRP 170. Modules may also be coupled to other T-TRPs. In some embodiments, the T-TRP 170 may actually be multiple T-TRPs operating together to provide service to the ED 110, for example, through the use of coordinated multipoint transmission.

[0063] As shown in FIG. 3 , the T-TRP 170 includes at least one transmitter 252 and at least one receiver 254 coupled to one or more antennas 256. Only one antenna 256 is shown. One, some, or all of the antennas 256 may alternatively be panels. The transmitter 252 and receiver 254 may be integrated as a transceiver. The T-TRP 170 further includes a processor 260 for performing operations, including operations related to preparing a transmission for downlink transmission to the ED 110; processing an uplink transmission received from the ED 110; preparing a transmission for backhaul transmission to the NT-TRP 172; and processing a transmission received from the NT-TRP 172 using the backhaul. Processing operations related to preparing a transmission for downlink or backhaul transmission may include operations such as encoding, modulation, precoding (e.g., multiple-input multiple-output “MIMO” precoding), transmit beamforming, and generating symbols for transmission. Processing operations related to processing transmissions received on the uplink or using the backhaul may include operations such as receive beamforming, demodulation of received symbols, and decoding of received symbols. The processor 260 may also perform operations related to network access (e.g., initial access) and / or downlink synchronization, such as generating synchronization signal block (SSB) content, generating system information, etc. In some embodiments, the processor 260 also generates a beam direction indication (e.g., BAI) that may be scheduled for transmission by the scheduler 253. The processor 260 performs other network-side processing operations described herein, such as determining the location of the ED 110 and determining where to deploy the NT-TRP 172. In some embodiments, the processor 260 may generate signaling, for example, to configure one or more parameters of the ED 110 and / or one or more parameters of the NT-TRP 172. Any signaling generated by the processor 260 is transmitted by the transmitter 252.It should be noted that "signaling," as used herein, may alternatively be referred to as control signaling. Dynamic signaling may be transmitted on a control channel, e.g., the Physical Downlink Control Channel (PDCCH), and static or semi-static higher layer signaling may be included in packets transmitted on a data channel, e.g., the Physical Downlink Shared Channel (PDSCH).

[0064] The scheduler 253 may be coupled to the processor 260. The scheduler 253 may be included within the T-TRP 170 or may operate separately from the T-TRP 170. The scheduler 253 may schedule uplink, downlink, and / or backhaul transmissions, which may include issuing scheduling grants and / or configuring scheduling-free ("configured grants") resources. The T-TRP 170 further includes a memory 258 for storing information and data. The memory 258 stores instructions and data used, generated, or collected by the T-TRP 170. For example, the memory 258 may store software instructions or modules configured to implement some or all of the functions and / or embodiments described herein and executed by the processor 260.

[0065] Although not shown, the processor 260 may form part of the transmitter 252 and / or part of the receiver 254. Also, although not shown, the processor 260 may implement the scheduler 253. Although not shown, the memory 258 may form part of the processor 260.

[0066] The processor 260, the scheduler 253, the processing components of the transmitter 252, and the processing components of the receiver 254 may each be implemented by the same one or more processors, or by different ones, configured to execute instructions stored in a memory (e.g., memory 258). Alternatively, some or all of the processor 260, the scheduler 253, the processing components of the transmitter 252, and the processing components of the receiver 254 may be implemented using dedicated circuitry, such as an FPGA, a CPU, a GPU, or an ASIC.

[0067] Notably, the NT-TRP 172 is shown as a drone by way of example only; the NT-TRP 172 may be implemented in any suitable non-terrestrial form, such as a high-altitude platform, a satellite, a high-altitude platform, an international mobile base station, and an unmanned aerial vehicle, as described below. The NT-TRP 172 may also be known by other names in some implementations, such as a non-terrestrial node, a non-terrestrial network device, or a non-terrestrial base station. The NT-TRP 172 includes a transmitter 272 and a receiver 274 coupled to one or more antennas 280. Only one antenna 280 is shown. One, some, or all of the antennas may alternatively be panels. The transmitter 272 and receiver 274 may be integrated as a transceiver. The NT-TRP 172 further includes a processor 276 for performing operations, including operations related to preparing a transmission for downlink transmission to the ED 110; processing an uplink transmission received from the ED 110; preparing a transmission for backhaul transmission to the T-TRP 170; and processing a transmission received from the T-TRP 170 using the backhaul. Processing operations related to preparing a transmission for downlink or backhaul transmission may include operations such as encoding, modulation, precoding (e.g., MIMO precoding), transmit beamforming, and generating symbols for transmission. Processing operations related to processing a transmission received on the uplink or using the backhaul may include operations such as receive beamforming, demodulating received signals, and decoding received symbols. In some embodiments, the processor 276 implements transmit beamforming and / or receive beamforming based on beam direction information (e.g., BAI) received from the T-TRP 170. In some embodiments, the processor 276 may generate signaling, for example, to configure one or more parameters of the ED 110. In some embodiments, the NT-TRP 172 implements physical layer processing but does not implement higher layer functions, such as functions at the Medium Access Control (MAC) or Radio Link Control (RLC) layers.This is just one example, more generally the NT-TRP 172 may implement higher layer functions in addition to physical layer processing.

[0068] The NT-TRP 172 further includes a memory 278 for storing information and data. Although not shown, the processor 276 may form part of the transmitter 272 and / or part of the receiver 274. Although not shown, the memory 278 may form part of the processor 276.

[0069] The processor 276, the processing components of the transmitter 272, and the processing components of the receiver 274 may each be implemented by one or more of the same or different processors configured to execute instructions stored in a memory (e.g., memory 278). Alternatively, some or all of the processor 276, the processing components of the transmitter 272, and the processing components of the receiver 274 may be implemented using dedicated circuitry, such as a programmed FPGA, CPU, GPU, or ASIC. In some embodiments, the NT-TRP 172 may actually be multiple NT-TRPs operating together to provide service to the ED 110, for example, through coordinated multipoint transmission.

[0070] T-TRP170, NT-TRP172 and / or ED110 may contain other components, which are omitted for clarity.

[0071] One or more steps of the method of the embodiments provided herein may be performed by a corresponding unit or module according to FIG. 4. FIG. 4 illustrates units or modules within a device, such as within the ED 110, the T-TRP 170, or the NT-TRP 172. For example, a signal may be transmitted by a transmitting unit or a transmitting module. A signal may be received by a receiving unit or a receiving module. A signal may be processed by a processing unit or a processing module. Other steps may be performed by an artificial intelligence (AI) or machine learning (ML) module. Each unit or module may be implemented using hardware, one or more components or devices that execute software, or a combination thereof. For example, one or more of these units or modules may be integrated circuits, such as a programmed FPGA, CPU, GPU, or ASIC. When these modules are implemented using software for execution by a processor, it will be understood that, for example, these modules may be retrieved by the processor, in whole or in part, as needed, individually or together for processing, in single or multiple instances, and that these modules themselves may include instructions for further deployment and instantiation.

[0072] Additional details regarding ED110, T-TRP170, and NT-TRP172 are known to those skilled in the art, and therefore these details are omitted here.

[0073] UE location information is often used within cellular communication networks to improve various performance metrics of the network. Such performance metrics may include, for example, capacity, agility, and efficiency. This improvement can be achieved when elements of the network leverage the UE's location, behavior, mobility patterns, etc. in the context of a priori information that describes the radio environment in which the UE is operating.

[0074] A sensing system may be used to help collect UE pose information, including the location of the UE in a global coordinate system, the speed and direction of movement of the UE in the global coordinate system, orientation information, and information about the radio environment. "Location" is also known as "position," and the two terms may be used interchangeably herein. Examples of well-known sensing systems include RADAR (Radio Detection and Ranging) and LIDAR (Light Detection and Ranging). While sensing systems are typically separate from communication systems, it may be advantageous to collect information using an integrated system, thereby reducing the hardware (and cost) and time, frequency, or space resources required within the system to perform both functions. However, performing UE pose and environmental information sensing using communication system hardware is very challenging and remains an unsolved problem. The difficulty of this problem is related to factors such as the limited resolution of communication systems, the dynamic nature of the environment, and the vast number of objects whose electromagnetic properties and positions are to be estimated.

[0075] Therefore, integrated sensing and communication (also known as integrated communication and sensing) is a desirable feature in existing and future communication systems.

[0076] Any or all of the EDs 110 and BSs 170 may be sensing nodes within the system 100. A sensing node is a network entity that performs sensing by transmitting and receiving sensing signals. Some sensing nodes are communication devices that perform both communication and sensing. However, some sensing nodes may not perform communication and instead be dedicated to sensing. The sensing agent 174 is an example of a sensing node dedicated to sensing. Unlike the EDs 110 and BSs 170, the sensing agent 174 does not transmit or receive communication signals. However, the sensing agent 174 may communicate configuration information, sensing information, signaling information, or other information within the communication system 100. The sensing agent 174 may communicate with the core network 130 to communicate information with the rest of the communication system 100. As an example, the sensing agent 174 may determine the location of the ED 110a and transmit this information to the base station 170a via the core network 130. Although only one sensing agent 174 is shown in FIG. 2, any number of sensing agents may be implemented within the communication system 100. In some embodiments, one or more sensing agents may be implemented in one or more of the RANs 120.

[0077] A sensing node may combine sensing-based techniques with reference signal-based techniques to improve UE pause determination. This type of sensing node may also be known as a sensing management function (SMF). In some networks, the SMF may also be known as a location management function (LMF). The SMF may be implemented as a physically separate entity located in the core network 130 with connections to multiple BSs 170. In other aspects of the present application, the SMF may be implemented as a logical entity co-located within the BS 170 through logic executed by the processor 260.

[0078] As shown in FIG. 5 , when implemented as a physically separate entity, the SMF 176 includes at least one processor 290, at least one transmitter 282, at least one receiver 284, one or more antennas 286, and at least one memory 288. A transceiver, not shown, may be used in place of the transmitter 282 and receiver 284. A scheduler 283 may be coupled to the processor 290. The scheduler 283 may be included within the SMF 176 or operated separately from the SMF 176. The processor 290 implements various processing operations of the SMF 176, such as signal coding, data processing, power control, input / output processing, or any other function. The processor 290 may also be configured to implement some or all of the functions and / or embodiments described in more detail above. Each processor 290 includes any suitable processing or computing device configured to perform one or more operations. Each processor 290 may include, for example, a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, or an application specific integrated circuit.

[0079] Reference signal-based pose determination techniques belong to the "active" pose estimation paradigm. In the active pose estimation paradigm, an interrogator of pose information (e.g., UE 110) participates in the process of determining the pose of the interrogator. The interrogator may transmit or receive (or both) signals specific to the pose determination process. Global Navigation Satellite System (GNSS)-based positioning techniques, such as the well-known Global Positioning System (GPS), are other examples of active pose estimation paradigms.

[0080] In contrast, detection techniques based on, for example, RADAR, can be considered to belong to a "passive" pose determination paradigm, in which the target is unaware of the pose determination process.

[0081] By integrating sensing and communication into one system, the system does not have to operate according to only a single paradigm, and thus a combination of sensing-based and reference signal-based techniques can result in improved pause determination.

[0082] Improved pause determination may include, for example, obtaining UE channel subspace information useful for UE channel reconstruction at the sensing node, particularly for beam-based operation and communication. The UE channel subspace is a subset of the entire algebraic space defined over a spatial domain in which the entire TP-to-UE channel resides. Therefore, the UE channel subspace defines the TP-UE channel with very high accuracy. Signals transmitted through other subspaces contribute negligibly to the UE channel. Knowledge of the UE channel subspace helps reduce the effort required for channel measurements at the UE and channel reconstruction on the network side. Therefore, a combination of sensing-based and reference signal-based techniques may enable UE channel reconstruction with much less overhead compared to conventional methods. Furthermore, the subspace information facilitates subspace-based sensing, thereby reducing sensing complexity and improving sensing accuracy.

[0083] In some embodiments of integrated sensing and communication, the same radio access technology (RAT) is used for sensing and communication, thereby avoiding the need to multiplex two different RATs under one carrier spectrum or requiring two different carrier spectrums for the two different RATs.

[0084] In embodiments that integrate sensing and communication under one RAT, a first set of channels may be used to transmit sensing signals and a second set of channels may be used to transmit communication signals. In some embodiments, each channel in the first set of channels and each channel in the second set of channels is a logical channel, a transport channel, or a physical channel.

[0085] At the physical layer, communication and sensing may be performed over separate physical channels. For example, a first physical downlink shared channel PDSCH-C may be defined for data communication, while a second physical downlink shared channel PDSCH-S may be defined for sensing. Similarly, separate physical uplink shared channels (PUSCHs), PUSCH-C and PUSCH-S, may be defined for uplink communication and sensing.

[0086] In another example, the same PDSCH and PUSCH may be used for both communication and sensing, with separate logical and / or transport layer channels defined for communication and sensing. It should also be noted that the control and data channels for sensing may have the same or different channel structures (formats) and occupy the same or different frequency bands or bandwidth portions.

[0087] In a further example, a common physical downlink control channel (PDCCH) and a common physical uplink control channel (PUCCH) may be used to carry control information for both sensing and communication. Alternatively, separate physical layer control channels may be used to carry separate control information for communication and sensing. For example, PUCCH-S and PUCCH-C may be used for uplink control for sensing and communication, respectively, and PDCCH-S and PDCCH-C may be used for downlink control for sensing and communication, respectively.

[0088] At each of the physical, transport and logical layers, different combinations of shared and dedicated channels for sensing and communication are possible.

[0089] The term RADAR originates from the phrase radio wave detection and ranging; however, expressions including different forms of capitalization (e.g., Radar and radar) are equally valid and are now more common. RADAR is typically used to detect the presence and location of objects. RADAR systems emit radio frequency energy and receive echoes of the energy reflected from one or more targets. The system determines the pose of a given target based on the echoes returned from the given target. The emitted energy can be in the form of energy pulses or continuous waves, which can be represented or defined by a particular waveform. Examples of waveforms used in RADAR include frequency modulated continuous wave (FMCW) and ultra-wideband (UWB) waveforms.

[0090] RADAR systems can be monostatic, bistatic, or multistatic. In a monostatic RADAR system, the RADAR signal transmitter and receiver are co-located, e.g., integrated within a transceiver. In a bistatic RADAR system, the transmitter and receiver are spatially separated, with the separation being equal to or greater than the expected target distance (often referred to as range). In a multistatic RADAR system, two or more RADAR components are spatially diverse but have a shared coverage area. Multistatic RADAR is also referred to as multi-site or netted RADAR.

[0091] Terrestrial RADAR applications face challenges such as multipath propagation and shadowing obstructions. Another challenge is the issue of distinguishability, as ground targets have similar physical attributes. Integrating sensing into communications systems is likely to suffer from these same challenges and more.

[0092] Communication nodes can be either half-duplex or full-duplex. A half-duplex node cannot both transmit and receive using the same physical resources (time, frequency, etc.); conversely, a full-duplex node can transmit and receive using the same physical resources. All existing commercial wireless communication networks are half-duplex. Even in the future, when full-duplex communication networks become practical, it is expected that at least some of the nodes in the network will still be half-duplex nodes because half-duplex devices are less complex, lower cost, and consume less power. In particular, full-duplex implementation is more challenging at higher frequencies (e.g., in the millimeter wave band) and is very difficult in smaller, low-cost devices such as femtocell base stations and UEs.

[0093] The limitations of half-duplex nodes within a communication network present additional challenges for integrating sensing and communications into communication network devices and systems. For example, both half-duplex and full-duplex nodes can perform bistatic or multistatic sensing, but monostatic sensing typically requires that the sensing node have full-duplex capabilities. Half-duplex nodes may perform monostatic sensing with certain limitations, for example, in pulsed RADAR with certain duty cycles and ranging capabilities.

[0094] Characteristics of a sensing signal, or a signal used for both sensing and communication, include the signal's waveform and its frame structure. The frame structure defines the time-domain boundaries of the signal. The waveform describes the shape of the signal as a function of time and frequency. Examples of waveforms that may be used for sensing signals include ultra-wideband (UWB) pulse, frequency-modulated continuous wave (FMCW) or "chirp," orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) OFDM, and discrete Fourier transform spread (DFT-s) OFDM.

[0095] In one embodiment, the detection signal is a linear chirp signal having a bandwidth B and a duration T. Such linear chirp signals are generally known from their use in FMCW RADAR systems. The linear chirp signal begins at an initial (start) time t chirp0 Initial (starting) frequency f chirp0 to the final time t chirp1 The final frequency at f chirp1 where the relationship between frequency (f) and time (t) is ff chirp0 =α(tt chirp0 ) where:

number

number

[0096] As used herein, precoding may refer to any coding operation or modulation that transforms an input signal into an output signal. Precoding may be performed in different domains and typically transforms an input signal in a first domain into an output signal in a second domain. Precoding may include linear operations.

[0097] MIMO technology enables an antenna array of multiple antennas to perform signal transmission and reception that meets high transmission rate requirements. The ED 110 and the T-TRP 170 and / or NT-TRP may use MIMO to communicate using radio resource blocks. MIMO transmits radio resource blocks via parallel radio signals by utilizing multiple antennas at the transmitter. This means that multiple antennas can be used at the receiver. MIMO may beamform parallel radio signals for reliable multipath transmission of the radio resource blocks. MIMO may combine parallel radio signals carrying different data to increase the data rate of the radio resource blocks.

[0098] In recent years, MIMO (massive MIMO) wireless communication systems with T-TRP 170 and / or NT-TRP 172 configured with multiple antennas have attracted widespread attention from academia and industry. In a massive MIMO system, T-TRP 170 and / or NT-TRP 172 are typically configured with more than 10 antenna units (see antenna 256 and antenna 280 in FIG. 3). T-TRP 170 and / or NT-TRP 172 are typically operable to serve dozens (e.g., 40) of EDs 110. The multiple antenna units of T-TRP 170 and NT-TRP 172 can significantly increase the spatial freedom of wireless communication, significantly improve transmission rates, spectral efficiency, and power efficiency, and greatly reduce inter-cell interference. Increasing the number of antennas allows each antenna unit to be made smaller and at lower cost. By using the spatial freedom provided by the large-scale antenna units, the T-TRP 170 and NT-TRP 172 of each cell can simultaneously communicate with more EDs 110 in the cell using the same time-frequency resources, thereby significantly improving spectral efficiency. The large number of antenna units in the T-TRP 170 and / or NT-TRP 172 also allows each user to have better spatial directivity for uplink and downlink transmission, resulting in reduced transmission power for the T-TRP 170 and / or NT-TRP 172 and ED 110, and correspondingly improved power efficiency. When the number of antennas in the T-TRP 170 and / or NT-TRP 172 is sufficiently large, the random channels between each ED 110 and the T-TRP 170 and / or NT-TRP 172 can approach orthogonality, so that interference between cells and users and the effects of noise can be reduced. The above-described advantages enable massive MIMO to have great potential for application.

[0099] A MIMO system may include a receiver connected to a receive (Rx) antenna, a transmitter connected to a transmit (Tx) antenna, and a signal processor connected to the transmitter and receiver. Each of the Rx antenna and the Tx antenna may include multiple antennas. For example, the Rx antenna may have a uniform linear array (ULA) antenna, in which multiple antennas are arranged in a line at equal intervals. When a radio frequency (RF) signal is transmitted through the Tx antenna, the Rx antenna may receive a signal reflected back from a target in front of the Tx antenna.

[0100] A non-exhaustive list of possible units or configurable parameters, or in some embodiments, of a MIMO system, includes: panels; and beams.

[0101] A panel is a unit of antenna group or antenna array or antenna sub-array, which can control Tx beam or Rx beam separately.

[0102] A beam may be formed by performing amplitude and / or phase weighting on data transmitted or received by at least one antenna port. A beam may be formed using other methods, for example, by adjusting related parameters of an antenna unit. The beam may include a Tx beam and / or an Rx beam. A transmit beam indicates a distribution of signal strength formed in different directions in space after a signal is transmitted through an antenna. A receive beam indicates a distribution of signal strength of a wireless signal received from an antenna in different directions in space. The beam information may include a beam identifier, an antenna port identifier, a channel state information reference signal (CSI-RS) resource identifier, an SSB resource identifier, a sounding reference signal (SRS) resource identifier, or other reference signal resource identifier.

[0103] In future wireless systems (6G and beyond), various low power mode procedures are expected to rely on what may be called "RF-dominant" processing. It has been explained above that digital processing should be avoided for low power mode procedures to the extent that such avoidance is possible. It can therefore be understood that RF-dominant processing can be expected to occur largely in the analog domain. However, it should also be clear that this processing may not be expected to occur entirely in the analog domain. In practice, some level of digital baseband processing may be deemed necessary. Such digital baseband processing may be used to a limited extent. Consequently, the results of the digital processing may be understood to have limited accuracy. For example, an ADC may be used at a low (e.g., sub-Nyquist) sampling rate to reduce power consumption relative to an ADC used at a typical (e.g., Nyquist) or higher sampling rate.

[0104] Examples of low power mode procedures may include low power sensing; low power positioning; low power paging; and the use of backscatter for communication.

[0105] It can be shown that synchronization between the UE 110 and the network entities with which the UE communicates (e.g., the TRP 170) allows the UE 110 to operate efficiently when the UE 110 implements so-called RF dominant procedures.

[0106] Synchronization may be indicated to enable UE 110 to avoid performance losses that may otherwise be indicated due to interference caused by synchronization offset. Additionally, synchronization may be indicated to facilitate resource management. Furthermore, synchronization may be indicated to reduce operational complexity. In practice, complex operations are known to be used to overcome lack of synchronization in instances where synchronization is not available.

[0107] When UE 110 or another node is operating in a low power mode, a synchronization offset may increase due to a lack of communication activity. Therefore, it is important to devise an approach to compensate for such an offset. Synchronization is particularly important when UE 110 is in a connected state in which UE 110 communicates data with one or more network entities. It follows that maintaining synchronization in a low power mode can be useful for UE 110 when UE 110 transitions to a connected state. Advantageously, some parameters that may be calculated as part of a synchronization procedure performed in one of the low power modes do not need to be recalculated when UE 110 transitions to a connected state.

[0108] Aspects of synchronization are addressed in the 5G NR wireless standard. In one aspect, synchronization of the access link between the UE 110 and the TRP 170 is addressed. In another aspect, synchronization of the sidelink connection between the first UE 110 and the second UE 110 is addressed. It can be shown that similar synchronization approaches are employed in both of these two aspects (see A. Omri, M. Shaqfeh, A. Ali and H. Alnuweiri, "Synchronization Procedure in 5G NR Systems," in IEEE Access, vol. 7, March 2019, pp. 41286-41295).

[0109] In the first scenario, where the UE 110 is synchronized with the TRP 170, a known synchronization signal (SS) block is defined in the time-frequency domain.

[0110] FIG. 6 shows the structure of an SS block 600 having four OFDM symbols 602-0, 602-1, 602-2, and 602-3.

[0111] The SS block 600 includes a primary synchronization signal (PSS) portion 604, a secondary synchronization signal (SSS) portion 606, and multiple physical broadcast channel (PBCH) portions 608.

[0112] From time to time, TRP 170 may be expected to broadcast SS block 600. UE 110 receiving SS block 600 may be indicated to be able to estimate the synchronization offset between the clock at UE 110 and the clock at TRP 170.

[0113] In response, UE 110 may take steps to synchronize the clock at UE 110 with the clock at TRP 170.

[0114] In known 5G NR standards, so-called M sequences have been employed in the PSS portion 604 of the SS block 600. In known 5G NR standards, so-called Gold sequences have been employed in the SSS portion 606 of the SS block 600.

[0115] UE 110 may extract information such as cell ID, frame number, and resource allocation indication by measuring the received SS block 600 and decoding the information within the received SS block 600. Note that UE 110 extracting this information involves processing the received SS block 600 in the digital baseband domain.

[0116] At high frequencies, it is known that the TRP170 may use directional transmission with narrow beams. The use of narrow beams is a strategy used to combat the relatively high propagation path loss associated with the use of high frequencies. Thus, in the context of high frequencies, the use of directional narrow beam transmission may be shown to be important for the task of providing reasonable service coverage within a given network.

[0117] To facilitate synchronization, SS blocks may be transmitted by the TRP 170 at different times using different beams in different directions, as shown in Figure 7. Typically, SS blocks are organized into SS bursts. Figure 7 shows a first SS burst 702-0 and a second SS burst 702-1. The start of the second SS burst 702-1 occurs a duration T after the start of the first SS burst 702-0. SS occurs for a duration of T SS may be referred to as an SS burst period. Figure 7 shows that the first SS burst 702-0 includes L number of SS blocks (SSBs) 704-0, 704-1, 704-2, ..., 704-L-1 (collectively or individually referred to as 704). Each of the SSBs 704 is shown as being transmitted in a different direction than all of the rest of the SSBs 704. The process of transmitting SSBs in different directions is often referred to as "beam sweeping."

[0118] In response, the UE 110 searches in different directions to attempt to receive and measure the SSB 704. The process of attempting to receive an SSB in different directions is often referred to as "beam sweeping." It is worth noting that the beam sweeping procedure performed in the UE 110 can be shown to involve increased resource overhead, increased complexity, and increased power consumption relative to attempting to receive and measure an SSB in a known direction.

[0119] A similar approach has been adopted for sidelink synchronization. A "sidelink" is a link between two UEs and can be used for several reasons, such as extending the coverage of a service provided by a particular TRP 170 to UEs not directly covered by that TRP 170. In such a scenario, a first UE (a "master" UE) within the coverage of a particular TRP 170 can act as a relay node to enable a second UE (a "slave" UE) not within the coverage of that TRP 170 to connect to the particular TRP 170. In sidelink synchronization, the master UE transmits a sidelink synchronization signal (S-SS) block, and the slave UE receives the S-SS block and measures the synchronization offset. Figure 8 shows the structure of a sidelink SS block 800 for regular cyclic prefix OFDM. The structure shown in Figure 8 has been adopted by the known Third Generation Partnership Project (3GPP) for the 5G NR standard. The sidelink SS block 800 includes 14 OFDM symbols and includes an S-PSS portion 804, an S-SSS portion 806, multiple PSBCH portions 808, and a guard portion 810.

[0120] In known 5G NR standards, M sequences have been adopted for the S-PSS portion 804 of the S-SS block 800. In known 5G NR standards, Gold sequences have been adopted for the S-SSS portion 806 of the S-SS block 800.

[0121] The slave UE may be expected to extract the timing and information embedded in the S-SS block by processing the received S-SS block in the digital baseband domain.

[0122] One major drawback of existing synchronization solutions is that they involve relatively high power consumption. This relatively high power consumption may be due to intensive digital processing in the baseband domain. This relatively high power consumption may also be due to beam sweeping to combat high path loss at high frequencies. Among other things, the main reason that existing synchronization solutions require digital baseband processing is that discrete sequences (e.g., M-sequences and Gold sequences) are used as synchronization signals and such sequences are embedded in OFDM symbols.

[0123] Generally, aspects of the present application relate to distributed round-trip short-range chirp signal transmission and measurement. In aspects of the present application, a UE in a low power mode can be synchronized with a network entity with the help of one or more nearby UEs (or other nodes) that are in a connected state and are already synchronized with the network entity as a result of being in a connected state. A nearby UE / node can be referred to as a "leader" UE / node. Notably, instead of "leader," the name of the nearby UE / node can be a "master" UE / node, a "prime" UE / node, or a "primary" UE / node, for just three alternative examples.

[0124] In aspects of the present application, a number of connected devices, which may be UEs or other network nodes, may be selected as a leader UE / node. This selection may be performed, for example, in the TRP 170 after receiving capability reports from multiple potential leader UEs / nodes.

[0125] The configuration of the "synchronization" chirp signal (transmitted by the leader UE / node) and the configuration of the "access" chirp signal (transmitted by a so-called "target" UE in low power mode) may be transmitted to the leader UE / node and the target UE using control signaling before the target UE enters low power mode. The leader UE then transmits the synchronization chirp signal based on the associated configuration. A UE in low power mode receives the synchronization chirp signal and extracts the timing of the received synchronization chirp signal by performing measurements on the synchronization chirp signal. Extracting the timing of the received synchronization chirp signal may be indicated to enable the target UE to obtain an estimate of the synchronization offset. Once the target UE obtains the estimate of the synchronization offset, it may take action to reduce the synchronization offset.

[0126] FIG. 9 illustrates a network including multiple UEs 110 associated with a TRP 170. The multiple UEs 110 include a first leader UE 110L1, a second leader UE 110L2, and six target UEs 110T. The leader UEs 110L1 and 110L2 are in connected mode. The target UEs 110T are in low power mode. The first leader UE 110L1 is associated with a first starting frequency f1 and a first coverage area 901. The second leader UE 110L2 is associated with a second starting frequency f2 and a second coverage area 902. FIG. 9 illustrates lines emanating from the first leader UE 110L1 and the second leader UE 110L2. These lines represent exemplary transmissions of synchronous chirp signals by the leader UEs 110L1 and 110L2. Each of these lines is associated with a chirp rate α0.

[0127] In Figure 9, α, f, and f are part of the synchronization signal configuration. In the example shown in Figure 9, a single chirp rate α is assigned to the synchronization signals transmitted by both reader UEs 110L1 and 110L2. Furthermore, the synchronization chirp signals have the same initial (start) time t chirp0, but transmitted at different initial (starting) frequencies. The duration T of each synchronous chirp signal is assumed to be the same.

[0128] FIG. 10 illustrates an access chirp signal transmission by a target UE 110T in the exemplary network shown in FIG.

[0129] The target UE 110T transmits an access chirp signal based on a previously defined configuration received when the target UE 110T was in a connected state. The leader UEs 110L1 and 110L2 receive the access chirp signal and estimate different parameters by performing measurements on the access chirp signal. In FIG. 10, the access chirp signals transmitted by different target UEs 110T are separated within the chirp rate domain. Furthermore, the start frequency of the access chirp signal transmitted by each target UE 110T can be obtained from measurements made by each target UE 110T on the received synchronization signal. As shown in FIG. 10, four of the target UEs 110T transmit access chirp signals to the first leader UE 110L1 with a first start frequency f1 and a unique one of four chirp rates α1, α2, α3, and α4. 10, two of the target UEs 110T transmit access chirp signals with a second start frequency f2 and a unique one of the two chirp rates α5, α6 to a second reader UE 110L2. Finally, the results of the measurements of the access chirp signals are transmitted by the reader UEs 110L1, 110L2 to the TRP 170 for further processing.

[0130] Advantageously, aspects of the present application relating to a chirp signal exchange approach to achieving synchronization may be shown to reduce power consumption relative to known baseband digital processing approaches to achieving synchronization described above by enabling RF-dominant processing. As noted above, aspects of the present application may involve some limited baseband processing after RF domain processing. Advantageously, the complexity of such baseband processing may be considered much lower than that of pure baseband operation. Additionally, the chirp signal exchange approach to achieving synchronization may be shown to enable a low-complexity version of synchronization offset estimation. For example, synchronization offset estimation may be achieved using pulse compression or matched filtering while the target UE 110T is in a low-power mode. Furthermore, each access chirp signal is configured using a parameter called a chirp rate, which may be used to multiplex more UEs as described below.

[0131] Advantageously, the chirp transmissions envisioned herein are short-range and local. This is true for the synchronization chirp signals envisioned herein, and it is true for the access chirp signals envisioned herein. The short-range and local characteristics can be shown to provide several benefits.

[0132] One benefit of the short-range feature is that a parameter called "time of flight" (ToF) is relatively small. Typically, the ToF term appears as an additive noise term when a device (e.g., the TRP 170 or the UE 110) is configured to estimate synchronization offset based on a single measurement. Consequently, the value of the estimated synchronization offset can be expressed as the sum of the actual synchronization offset and the ToF. However, because the ToF is small, especially for the scenario envisioned herein, the dominant term in the sum of the estimated synchronization offsets is the actual synchronization offset. Thus, the sum of the estimated synchronization offsets is approximately equal to the actual synchronization offset. By processing measurements of the received synchronization signals, it follows that the device can obtain a sum of estimated synchronization offsets that provides an approximation of the actual synchronization offset with a reasonable level of accuracy. Advantageously, the approximation of the actual synchronization offset is obtained without expending the time and effort of calculating the ToF.

[0133] As an example, if the short distance over which the chirp signal is transmitted is 30 meters, the ToF may be calculated to be 0.1 microseconds. Therefore, the sum of any estimated synchronization offsets on the order of a few microseconds may be understood to be within 0.1 microseconds of the actual synchronization offset.

[0134] Another benefit of the short-range feature is that, since the path loss is not significant, omnidirectional or wide-beam transmission can be expected to be sufficient for the transmission of chirp signals. As a result, there is no need for beam sweeping. By avoiding the beam sweeping associated with known synchronization schemes, the overhead, complexity, and power consumption associated with beam sweeping are also avoided.

[0135] An additional benefit of the short-range feature is that time / frequency resources can be spatially reused, and therefore the resource overhead associated with aspects of the present application is relatively small.

[0136] Aspects of the present application relate to interactions between three types of devices.

[0137] One type of device is the target UE 110T (see FIGS. 9 and 10). The target UE 110T, which may also be referred to as a terminal device, is understood to be in a low power mode. The target UE 110T enters the low power mode to save energy. One objective of the present embodiment is to synchronize the target UE 110T with the TRP 170 while the target UE 110T is in the low power mode. In the present embodiment, the target UE 110T is configured to perform a method whose exemplary steps are shown in FIG. 11. First, before entering the low power mode, the target UE 110T may receive a synchronization chirp signal configuration and an access chirp signal configuration from the TRP 170 (step 1102). After entering the low power mode (step 1104), the target UE 110T may receive a synchronization chirp signal from the leader UE 110L (step 1106). The target UE 110T may also obtain measurement results by performing measurements on the received synchronization chirp signal (step 1106). The target UE 110T may process the measurement results to obtain an estimated synchronization offset (step 1108). The target UE 110T may then correct the clock at the target UE 110T based on the estimated synchronization offset (step 1110). The target UE 110T may optionally infer parameters to use when transmitting an access chirp signal from the measurements of the received synchronization signal (step 1112). The target UE 110T may then transmit an access signal based on the configuration defined by the TRP 170 (step 1114). The access chirp signal transmitted in step 1114 may also be based on the parameters estimated in step 1112.

[0138] Another type of device is the leader UE 110L (see FIGS. 9 and 10). The leader UE 110L may be understood as a UE in a connected state. The leader UE 110L may additionally or alternatively be understood as another network-controlled node defined with several purposes, including facilitating synchronization for the target UE 110T. In an aspect of the present application, the leader UE 110L is configured to perform a method whose exemplary steps are shown in FIG. 12. First, the leader UE 110L receives a synchronization chirp signal configuration and an access chirp signal configuration from the TRP 170 (step 1202). The particular leader UE 110L may transmit a synchronization chirp signal based on the received configuration (step 1204). Next, the particular leader UE 110L may receive an access chirp signal from the target UE 110T (step 1206). Upon receiving the access chirp signals (step 1206), the specific reader UE 110L may perform measurements of the timing and spatial direction of the received access chirp signals. Based on the obtained measurements, the specific reader UE 110L may determine which of the access chirp signals (if any) are intended for the specific reader UE 110L (step 1208). For the specific access chirp signals determined to be intended for the specific reader UE 110L (step 1208), the specific reader UE 110L may transmit a measurement report to the TRP 170 including an indication of the measurement values ​​associated with the specific access chirp signals (step 1210).

[0139] Another type of device is the TRP 170 (see FIGS. 1 to 4, 7, 9, and 10). In an embodiment of the present application, the TRP 170 is configured to perform a method whose exemplary steps are shown in FIG. 13. First, the TRP 170 may manage the configuration details of the access chirp signal and the synchronization chirp signal (step 1302). Next, the TRP 170 may transmit the configuration details of the access chirp signal and the synchronization chirp signal to the target UE 110T while the target UE 110T is in a connected state (step 1304). The TRP 170 may also transmit the configuration details of the access chirp signal and the synchronization chirp signal to the leader UE 110L (step 1306). Notably, there need not be a specific time order for steps 1304 and 1306. Upon receiving the measurement report from leader UE 110L (step 1308), TRP 170 may process the measurements included in the measurement report (step 1310) to obtain the desired quantity.

[0140] Aspects of the present application relate to the configuration of the synchronization chirp signal. Recall that a synchronization chirp signal is transmitted by each reader UE 110L (step 1204 in FIG. 12). The specific configuration of the synchronization chirp signal can be managed (by the TRP 170 (see step 1302 in FIG. 13)) for the i-th reader UE 110L. The specific configuration of the synchronization chirp signal is determined by the chirp rate α i ;start time t i ;Duration T i ;starting frequency f i ;Transmission power P i and an expression for the period in time and frequency of the synchronization signal. The period in time of the synchronization signal is the period

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[0141] Figure 14 shows four of the synchronous chirp signal configuration parameters (α i , t i , T i and f i ) affects the synchronization chirp signal in a frequency versus time plot. The configuration parameters referenced in FIG. 14 correspond to the configuration parameters used when the i-th reader UE 110L-i transmits the synchronization chirp signal (step 1306). In particular, the transmission range of the synchronization chirp signal transmitted by the i-th reader UE 110L-i (step 1306) is determined by the transmit power P i It can be regulated by TRP170, which regulates

[0142] Figure 15 shows two of the synchronous chirp signal configuration parameters (

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[0143] The general steps in a synchronization procedure performed in a network with a TRP 170, multiple leader UEs 110L and multiple target UEs 110T are as follows.

[0144] The TRP 170 transmits the configuration details of the access chirp signal and the respective synchronization chirp signal to the leader UE 110L (step 1306 of FIG. 13). The TRP 170 also transmits the configuration details of the respective access chirp signal and the respective synchronization chirp signal to the target UE 110T before the target UE 110T enters the low power mode (step 1304 of FIG. 13). The transmission of the configuration details (steps 1304 and 1306 of FIG. 13) may be performed by the TRP 170 using control signaling, such as RRC configuration signaling.

[0145] Each leader UE 110L transmits a synchronization chirp signal to the target UE 110T (step 1204 in FIG. 12) based on the configuration details received (step 1202 in FIG. 12).

[0146] At the exemplary target UE 110T, a synchronization chirp signal is received from a nearby leader UE 110L (step 1106 of FIG. 11 ). The exemplary target UE 110T performs measurements (step 1106 of FIG. 11 ) along with RF-dominant processing to obtain the timing of the received synchronization signal, and therefore, the synchronization offset (step 1108 of FIG. 11 ). The exemplary target UE 110T selects one of the leader UEs 110L based on the measurements and estimates the synchronization offset for the selected leader UE 110L (step 1108 of FIG. 11 ). The exemplary target UE 110T may correct the clock at the exemplary target UE 110T based on the estimated synchronization offset (step 1110 of FIG. 11 ). From the measurements of the received synchronization signal, the exemplary target UE 110T may infer parameters to use when transmitting an access chirp signal (step 1112 of FIG. 11 ).

[0147] The multiple reader UEs 110L may not be synchronized with each other. The TRP 170 may have the ability to compensate for any synchronization offset between the various reader UEs 110L through management of the synchronization chirp signal configuration (step 1302 of FIG. 13). To this end, the start time of the synchronization chirp signal may be set for each reader UE 110L in a manner that compensates for the timing offset between the multiple reader UEs 110L. In this way, the TRP 170 may attempt to establish that multiple synchronization chirp signals are transmitted simultaneously with respect to the network clock from the multiple reader UEs 110L (step 1304 of FIG. 12). Notably, such synchronization provides several benefits (described below) that need not be considered mandatory. Two general scenarios are envisioned:

[0148] In the first scenario, it may be assumed that the leader UE 110L is not synchronized, and therefore may be understood to transmit a synchronization chirp signal with some time offset with respect to the network clock.

[0149] In the second scenario, the leader UE 110L may be assumed to be synchronized, and therefore may be understood to transmit synchronization chirp signals simultaneously with respect to the network clock.

[0150] In a first scenario, the synchronization task is best performed when the target UE 110T is associated with a particular leader UE 110L for both receiving synchronization chirp signals (step 1106 in FIG. 11 ) and transmitting access chirp signals (step 1114 in FIG. 11 ). Consider that a given target UE 110T-X receives and measures (step 1106 in FIG. 11 ) the synchronization chirp signal transmitted by a given leader UE 110L-Y. Based on the measurements, the given target UE 110T-X may estimate a synchronization offset with respect to the given leader UE 110L-Y (step 1108 in FIG. 11 ). It follows that the synchronization task is best performed considering that the access chirp signal transmitted by a given target UE 110T-X (step 1114 in FIG. 11 ) is received (step 1206) and measured by the given leader UE 110L-Y.

[0151] One strategy for enabling the target UE 110T to associate with a particular leader UE 110L for both receiving synchronization chirp signals (step 1106 of FIG. 11 ) and transmitting access chirp signals (step 1114 of FIG. 11 ) involves establishing that the configuration of each synchronization chirp signal is unique to the leader UE 110L transmitting the synchronization chirp signal. In this way, each synchronization chirp signal among multiple synchronization chirp signals received at the target UE 110T can be distinguished and associated with a particular leader UE 110L at the target UE 110T.

[0152] To distinguish between the synchronization chirp signals transmitted by each reader UE 110L among multiple reader UEs 110L, the TRP 170 may configure each of the reader UEs 110L to use a different start time, a different start frequency, a different chirp rate, or any combination of these parameters.

[0153] In particular, from a practical perspective, enabling differentiation between synchronization chirp signals transmitted by different leader UEs 110L using different chirp rates may be unattractive. As explained above, the target UE 110T is expected to perform measurements on received synchronization chirp signals (step 1106 of FIG. 11 ). When each leader UE 110L is configured to use different chirp rates when transmitting a synchronization chirp signal (step 1204 of FIG. 12 ), it follows that the target UE 110T is expected to perform measurements on received synchronization chirp signals having a variety of different chirp rates (step 1106 of FIG. 11 ). In anticipation of enabling the target UE 110T to perform measurements on received synchronization chirp signals having a variety of different chirp rates (step 1106 of FIG. 11 ), the target UE 110T's hardware may be configured to perform measurements on received synchronization chirp signals having a variety of different chirp rates (step 1106 of FIG. 11 ). It should be readily appreciated that hardware configured to perform measurements on a received synchronous chirp signal having only one chirp rate (step 1106 of FIG. 11) is less complex than hardware configured to perform measurements on received synchronous chirp signals having a variety of different chirp rates (step 1106 of FIG. 11). It should additionally be appreciated that hardware configured to perform measurements on received synchronous chirp signals having only one chirp rate (step 1106 of FIG. 11) is likely to consume less power than hardware configured to perform measurements on received synchronous chirp signals having a variety of different chirp rates (step 1106 of FIG. 11).

[0154] Consequently, although it may be the case that different chirp rates are possible to enable differentiation of synchronization chirp signals transmitted by different reader UEs 110L, the following focuses on a scenario in which the chirp rate is the same for all synchronization chirp signals for practical reasons. In such a scenario, to enable differentiation of synchronization chirp signals transmitted by different reader UEs 110L, the TRP 170 may configure the different reader UEs 110L to expect chirp synchronization signals with different start times and / or different start frequencies.

[0155] In the first case shown in Figure 16, a start frequency is used to distinguish between a first synchronization chirp signal 1601 transmitted by a first reader UE and a second synchronization chirp signal 1602 transmitted by a second reader UE. That is, the first synchronization chirp signal 1601 has a first start frequency f1, and the second synchronization chirp signal 1602 has a second start frequency f2. Specifically, the first synchronization chirp signal 1601 has a start time t, and the second synchronization chirp signal 1602 has the same start time t. Furthermore, specifically, the first synchronization chirp signal 1601 has a chirp rate α0, and the second synchronization chirp signal 1602 has the same chirp rate α0.

[0156] In the second case shown in Figure 17, start times are used to distinguish between a first synchronization chirp signal 1701 transmitted by a first reader UE and a second synchronization chirp signal 1702 transmitted by a second reader UE. That is, the first synchronization chirp signal 1701 has a first start time t1, and the second synchronization chirp signal 1702 has a second start time t2. Specifically, the first synchronization chirp signal 1701 has a start frequency f, and the second synchronization chirp signal 1702 has the same start frequency f. Furthermore, specifically, the first synchronization chirp signal 1701 has a chirp rate α, and the second synchronization chirp signal 1702 has the same chirp rate α.

[0157] In the third case shown in Figure 18, both the start frequency and start time are used to distinguish between a first synchronization chirp signal 1801 transmitted by a first reader UE and a second synchronization chirp signal 1802 transmitted by a second reader UE. That is, the first synchronization chirp signal 1801 has a first start time t1 and a first start frequency f1. The second synchronization chirp signal 1802 has a second start time t2 and a second start frequency f2. In particular, the first synchronization chirp signal 1801 has a chirp rate α0, and the second synchronization chirp signal 1802 has the same chirp rate α0.

[0158] Enabling a target UE 110T to associate with a particular leader UE 110L for both receiving synchronization chirp signals (step 1106 of FIG. 11 ) and transmitting access chirp signals (step 1114 of FIG. 11 ) may involve implementing a strategy that includes establishing a connection between the configuration of the synchronization chirp signals and the configuration of the access chirp signals. Such a connection may be indicated to help the particular leader UE 110L identify which received access chirp signals among multiple received access chirp signals are intended for the particular leader UE 110L.

[0159] The first option for this strategy is to set the start frequency of the access chirp signal, f access to the start frequency of the synchronization chirp signal. Using this first option, one result of the target UE 110T performing measurements on the received synchronization chirp signal (step 1106 of FIG. 11 ) may be that the target UE 110T obtains the synchronization chirp signal start frequency. The synchronization chirp signal start frequency may be used by the target UE 110T to determine the access chirp signal start frequency. For example, the target UE 110T may select the access chirp signal start frequency f to use when transmitting the access chirp signal (step 1114 of FIG. 11 ). access The access chirp signal start frequency f access is the chirp synchronization signal start frequency f synch and a constant frequency offset fconst That is, the access chirp signal start frequency f access is the relation f access =f synch +f const The constant frequency offset f const The value of may be provided to the target UE 110T by the TRP 170 through control signaling at a time preceding the target UE 110T entering the low power mode. const The value of may also be provided to the reader UE 110L by the TRP 170. Additionally, the chirp synchronization signal start frequency f synch and a constant frequency offset f const Based on the available values ​​of , the reader UE 110L determines the access chirp signal start frequency f access The reader UE 110L may be able to determine the access chirp signal start frequency f access Upon determining {overscore (R)}, measurements may be performed on the access chirp signal received from the target UE 110T.

[0160] A second option for this strategy is to associate the start time of the access chirp signal with the start time of the synchronization chirp signal. Using this second option, one result of the target UE 110T performing measurements on the received synchronization chirp signal (step 1106 of FIG. 11) may be that the target UE 110T obtains the synchronization chirp signal start time. The access chirp signal start time t access is the chirp synchronization signal start time t synch and a fixed time offset t const That is, the access chirp signal start frequency f access is the relation t access =t synch +t const can be determined from a fixed time offset t constThe value of t may be provided to the target UE 110T by the TRP 170 through control signaling at a time preceding the target UE 110T entering the low power mode. const The value of t may also be provided to the leader UE 110L by the TRP 170. Additionally, the synchronization chirp signal start time t synch and a fixed time offset t const Based on the available values ​​of , the reader UE 110L determines the access chirp signal start time t access The reader UE 110L may be able to determine the access chirp signal start frequency t access Upon determining {overscore (R)}, measurements may be performed on the access chirp signal received from the target UE 110T.

[0161] A third option for this strategy is to associate the access chirp start time with the synchronization chirp start time and the access chirp start frequency with the synchronization chirp start frequency. Using this third option, one result of the target UE 110T performing measurements on the received synchronization chirp signal (step 1106 of FIG. 11) may be that the target UE 110T obtains the synchronization chirp start time and synchronization chirp start frequency. The access chirp start time t access and the access chirp signal start frequency t access can be determined from the relationships explained above. More generally, the access chirp signal start time t access is the synchronous chirp signal start time t synch and the synchronous chirp signal start frequency f synch Similarly, the access chirp signal start frequency f access is the synchronous chirp signal start time t synch and the synchronous chirp signal start frequency f synch It may be a function of both.

[0162] Notably, in all three options described above, part of the configuration of the access chirp signal may be inferred at the target UE 110T from measurements taken on the received synchronization chirp signal. In such cases, it should be clear that the inferred part of the access chirp signal configuration does not need to be signaled to the target UE 110T before the target UE 110T enters the low power mode.

[0163] An aspect of the present application relates to a low-complexity receiver 2000 (see FIG. 20) that can enable a target UE 110T to extract timing from a received synchronization chirp signal while the target UE 110T is operating in a low power mode. The processing of the received synchronization chirp signal in the receiver 2000 can be understood to be based on matched filtering of the received synchronization chirp signal. The matched filtering process is sometimes referred to as “pulse compression.” It is known that the matched filtering process, implemented in the RF domain, leads to reduced complexity and power consumption relative to processing performed in the baseband domain. To operate properly, a matched filter 2004 arranged to implement the matched filtering process is matched to the synchronization chirp signal transmitted by the leader UE 110L. Therefore, the target UE 110T is expected to receive at least a portion of the synchronization chirp signal configuration (e.g., an indication of the chirp rate) before the target UE 110T enters the low power mode. In response to receiving at least a portion of the synchronization chirp signal configuration, the target UE 110T may adjust the matched filter 2004 for use in the low power mode. It can generally be shown that when a pre-matched signal is fed to the matched filter, the output envelope will be shaped similarly to a sinc function in the time domain. Timing information of the transmitted chirp signal may be extracted by detecting the timing of peaks in the output envelope. Alternatively, timing information may be extracted from multiplying the received synchronization chirp signal by the conjugate of the transmitted synchronization chirp signal and detecting the beat frequency of the synchronization chirp signal after applying a low-pass filter. In some embodiments, detecting the beat frequency of the synchronization chirp signal may involve performing an FFT operation on the sampled RF-processed signal.

[0164] Consider the example shown in Figure 19, where there are two reader UEs 110L1 and 110L2 near a target UE 110T that is in a low power mode. The first reader UE 110L1 is associated with a synchronization chirp signal having a first start frequency f1 and a first coverage area 1901. The second reader UE 110L2 is associated with a synchronization chirp signal having a second start frequency f2 and a second coverage area 1902. For the purposes of this example, it may be assumed that both synchronization chirp signals start at time zero, i.e., t1 = t2 = 0. For the purposes of this example, it may also be assumed that the start frequencies of the synchronization chirp signals transmitted by the two reader UEs 110L1 and 110L2, i.e., f1 and f2, are well separated.

[0165] FIG. 20 shows the basic structure and representation of the synchronization chirp signals of two reader UEs 110L1 and 110L2 and a target UE 110T. The first reader UE 110L1 has a first chirp generator 2002-1 for generating a synchronization chirp signal based on a defined configuration. The second reader UE 110L2 has a second chirp generator 2002-2 for generating a synchronization chirp signal based on a defined configuration. Both synchronization chirp signals are shown as having a common chirp rate α. In the target UE 110T, a matched filter 2004 is matched to the signals having the common chirp rate α, a zero start time, and a specific start frequency. The output from the matched filter 2004 is passed to a peak detection unit 2006. The peak detection unit 2006 may be configured to detect peaks in the envelope of the output from the matched filter 2004.

[0166] FIG. 21 shows an example envelope of the output of the matched filter 2004 in FIG.

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[0167] 22 shows steps of an exemplary method for processing a received synchronization chirp signal. First, receiver 2000 of target UE 110 receives the signal (step 2202). Target UE 110 may process the received signal using matched filter 2004 (step 2204) to generate a matched filter output including the envelope (see FIG. 21). Next, target UE 110 may use peak detection unit 2006 to obtain the so-called measured timing of the peak (step 2206). The measured timing may be

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[0168] Once the target UE 110T has selected a peak (step 2208), it may be considered to have provided itself with some configuration information for the access chirp signal. In the first example, it may be assumed that the first peak is selected and the first case is used. Recall that in the first case shown in Figure 16, a starting frequency is used to distinguish between the first synchronization chirp signal 1601 transmitted by the first reader UE and the second synchronization chirp signal 1602 transmitted by the second reader UE.

[0169] Upon selecting the peak (step 2208), the target UE 110T adds a constant frequency f to the start frequency f obtained by selecting the peak. const, and may transmit (step 2210) an access chirp signal having a start frequency determined based on adding f access =f1+f const is.

[0170] Upon obtaining measurements of the access chirp signal, the first reader UE 110L1 may determine that there is a nearby target UE 110T in a low power mode that has decided to associate with the first reader UE 110L1.

[0171] Among other things, an estimate of the synchronization offset between itself and the selected leader UE 110Li

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[0172] Aspects of the present application relate to access chirp signal configuration, access chirp signal transmission, and access chirp signal measurement. An access chirp signal is transmitted by a target UE 110T (e.g., step 2210 of FIG. 22) and measured by a leader UE 110L. Configuration parameters of the access chirp signal may include chirp rate; start time; duration; start frequency; and transmit power.

[0173] In operation, the TRP 170 may transmit configuration parameters of the access chirp signal to the leader UE 110L and the target UE 110T before entering the low power mode. In one example, the TRP 170 may transmit the configuration parameters using control signaling, such as RRC configuration signaling. One or more configuration parameters of the access chirp signal may be inferred at the target UE 110T based on measurements made on the received synchronization chirp signal.

[0174] In operating in the low power mode, the target UE 110T transmits an access chirp signal based on the configuration (eg, step 2210 of FIG. 22).

[0175] FIG. 23 shows exemplary steps in a method of operation of a given reader UE 110L with respect to an access chirp signal.

[0176] First, the given leader UE 110L receives configuration parameters of the access chirp signals of multiple nearby target UEs 110T from the TRP 170 (step 2302). The given leader UE 110L may also receive configuration parameters of the synchronization chirp signals from the TRP 170 (step 2302).

[0177] A given leader UE 110L may then receive an access chirp signal transmitted by a nearby target UE 110T (step 2304).

[0178] The given leader UE 110L may then perform measurements on the received access chirp signal (step 2306).

[0179] From the measurements, the given leader UE 110L may determine an access chirp signal corresponding to each of the target UEs 110T that have selected to associate with the given leader UE 110L (stage 2308).

[0180] The given leader UE 110L may then transmit the measurement results corresponding to the target UEs 110T that have chosen to be associated with the given leader UE 110L to the TRP 170 for further processing (stage 2310).

[0181] It may be advantageous to arrange for the transmission of access chirp signals by different target UEs 110T (step 2210 of FIG. 22) to occur in different regions, which may be shown to enable the leader UE 110L to determine a correspondence between the access chirp signals and the target UEs 110T based on performing measurements on the received access chirp signals (step 2306 of FIG. 23).

[0182] Such preparation may involve assigning different access chirp signal configuration parameters, such as start time, start frequency, and / or chirp rate, to different target UEs 110T. It follows that multiple mappings may be defined. Each mapping may be understood to associate a specific set of access chirp signal configuration parameters with a specific target UE 110T. A mapping may be indexed using a UE ID already associated with a specific target UE 110T. In some cases described above, the start time and / or start frequency of the access chirp signal may be estimated at the target UE 110T based on processing measurements of the received synchronization chirp signal. It is worth noting that the estimated start time and / or start frequency are poor candidates for use when multiplexing signals from multiple target UEs 110T. However, the chirp rate domain is always available for use when multiplexing signals from multiple target UEs 110T.

[0183] For a first example, recall that in the first case shown in FIG. 16, a starting frequency can be used to distinguish between the first synchronization chirp signal transmitted by the first reader UE 110L in FIG. 19 and the second synchronization chirp signal transmitted by the second reader UE 110L2 in FIG. 19. Consider a case in which the starting frequency of the access chirp signal is determined based on measurements of the synchronization chirp signal at the target UE 110T. In such a case, it can be shown that the starting frequency of the access chirp signal need not be used to multiplex the access chirp signal transmissions among multiple target UEs 110T. However, the starting time and chirp rate can be used to multiplex the access chirp signal transmissions among multiple target UEs 110T. Furthermore, it is important to note that although various time-frequency resources can be used for access chirp signal transmissions by different target UEs 110T, such resources can be reused throughout the network due to the short distances of the transmissions.

[0184] After the target UE 110T transmits the access chirp signal (step 2210 of FIG. 22), the nearby leader UE 110L receives the access chirp signal (step 2304 of FIG. 23) and performs measurements (step 2306 of FIG. 23) to obtain configuration parameters of the received access chirp signal. The nearby leader UE 110L may also obtain various other parameters, which will be mentioned below. From the obtained configuration parameters for the received access chirp signal, the leader UE 110L may determine whether the received access chirp signal was intended for the leader UE 110L. For example, in the example described above, the target UE 110T may select the first leader UE 110L1 and consequently use an access chirp signal starting frequency based on the first starting frequency f1. Upon receiving the access chirp signal at the second leader UE 110L2, the second leader UE 110L2 may determine that the access chirp signal starting frequency is based on the first starting frequency f1. Based on the determination that the access chirp signal start frequency is based on the first start frequency f1, the second reader UE 110L2 may ignore the access chirp signal. Upon detecting the access chirp signal, the first reader UE 110L1 may determine that a target UE 110T in the surrounding area has selected to associate with the first reader UE 110L1. Power consumption is not expected to be an issue for the reader UE 110L. Therefore, measurements performed at the reader UE 110L (step 2306 of FIG. 23) may be performed in the analog RF domain or in the digital baseband domain. Measurements may also be performed for multiple chirp rates (step 2306 of FIG. 23).

[0185] Results of measurements performed at a given reader UE 110L may enable the given reader UE 110L to determine timing estimates for each target UE 110T associated with the given reader UE 110L. It may be shown that the ToF of the link between the given reader UE 110L and the target UE 110T may be obtained from the timing estimates. In particular, obtaining the ToF of the link may be considered accurate only in the case where the target UE 110T corrects its timing (step 2214 of FIG. 22) after processing measurements on the synchronization chirp signal received at the target UE 110T from the given reader UE 110L (step 2202 of FIG. 22).

[0186] The results of measurements performed at a given leader UE 110L may also enable the given leader UE 110L to determine the angle of arrival (AoA) of the access chirp signal transmitted by each target UE 110T associated with that leader UE 110L.

[0187] After determining the access chirp signals corresponding to each of the target UEs 110T that have selected to be associated with the given leader UE 110L (step 2308 of FIG. 23), the given leader UE 110L transmits the measurement results corresponding to the target UEs 110T that have selected to be associated with the given leader UE 110L to the TRP 170 for further processing (step 2310 of FIG. 23).

[0188] For the second example, it may be assumed that the target UE 110T of Figure 19 selects the first reader UE 110L1 after measuring the synchronization chirp signal. Again, it may be assumed that the first case shown in Figure 16 is used. Recall that in the first case, a starting frequency may be used to distinguish between the first synchronization chirp signal transmitted by the first reader UE 110L of Figure 19 and the second synchronization chirp signal transmitted by the second reader UE 110L2 of Figure 19.

[0189] Target UE110T is f1+f constThe start frequency f of the transmitted access chirp signal access It is expected to be used as f const The value of f may have been received by the target UE 110T in the access chirp signal configuration before entering the low power mode. The value of f may be obtained by the target UE 110T based on measurements of the synchronization chirp signal received from the first leader UE 110L1. The value α may be used to represent the chirp rate assigned to the target UE 110T for the access chirp signal in this example. Also, the value t may be used to represent the start time of the access chirp signal assigned to the target UE 110T. The target UE 110T may configure the chirp rate α, the start frequency f, and the synchronization frequency f as shown in FIG. 24. access =f1+f const and an access chirp signal having a start time t1.

[0190] Both reader UEs 110L1, 110L2 are expected to receive the transmitted access chirp signal and perform measurements. The results of the measurements at both reader UEs 110L1, 110L2 determine the start frequency f of the received access chirp signal. access =f1+f const As a result, the second reader UE 110L2 may recognize that the target UE 110T that transmitted the access chirp signal did not choose to associate with the second reader UE 110L2. Recall that the first start frequency f1 is used as the start frequency of the synchronization chirp signal transmitted by the first reader UE 110L1. The target UE 110T may recognize that the first start frequency f1 is used as the start frequency of the synchronization chirp signal transmitted by the first reader UE 110L1. accessBased on the first starting frequency f1, the measurement indirectly indicates that the target UE 110 intends to associate with the first reader UE 110L1. After the measurement, the first reader UE 110L1 may determine that a target UE 110T that wishes to associate with the first reader UE 110L1 is nearby. Using the measurement result, the first reader UE 110L1 may also obtain the ToF of the link between the first reader UE 110L1 and the target UE 110T. Using the measurement result, the first reader UE 110L1 may further obtain the AoA of the access chirp signal received from the target UE 110T. The first reader UE 110L1 may then transmit an indication of the configured ToF and AoA measurements at α1, f1, and t1 to the TRP 170. Because TRP170 maintains the configuration parameters of the access chirp signals of different target UE110T, TRP170 can infer from the configuration reported along with the measurements (e.g., α1, f1, and t1) that the measured values ​​correspond to target UE110T.

[0191] Aspects of the present application relate to determining a timing advance (TA) of a target UE 110T with respect to a TRP 170 while the target UE 110T is operating in a low power mode. The determination of the TA may be based on measurements of an access chirp signal performed by a reader UE 110L associated with the target UE 110T.

[0192] In Figure 25, there is a TRP 170, a target UE 110T, and a reader UE 110L1 with which the target UE 110T is associated. As explained above, it can be assumed that the synchronization chirp signal and the access chirp signal are transmitted and measured. The TRP 170 receives from the reader UE 110L1 the results of measurements made on the access chirp signal transmitted by the target UE 110T. In Figure 25, the TRP 170, the target UE 110T, and the reader 110L1 can be seen as the vertices of a triangle.

[0193] The first link (sidelink) between the target UE 110T and the leader UE 110L1 may be associated with a value labeled "a" of the ToF of the first link. The value of ToF may be understood to be obtained by the leader UE 110L1 based on measurements made on the access chirp signal. It is also expected that the leader UE 110L1 has reported the ToF to the TRP 170. It follows that the TRP 170 will maintain the value of a after receiving the report.

[0194] Furthermore, the second link between the TRP 170 and the leader UE 110L1 may be associated with a value labeled "b" of the ToF of the second link. Because the leader UE 110L1 is already connected to the TRP 170, it may be assumed that the TRP 170 has already determined the value of b (e.g., the value of b may have been measured during an initial access procedure performed at the leader UE 110L1). Recall that the AoA of the access chirp signal transmitted by the target UE 110T may be measured at the leader UE 110L1. In FIG. 25, the angle θ is shown as being formed between the first link and the second link. The value of the angle θ may be determined based on the value of the AoA reported by the leader UE 110L1 to the TRP 170.

[0195] The third link between the TRP 170 and the target 110T may be associated with a value labeled "x" of the ToF of the third link. The TA of the target UE 110T with respect to the TRP 170 may be equal to the x of the ToF of the third link. It follows that by determining the value of x given the values ​​of a, b, and θ, the value of the TA of the target UE 110T with respect to the TRP 170 may be understood to be determined.

[0196] This embodiment can be used to find the value of x given the values ​​of a, b, and θ using the well-known law of cosines.

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[0197] Aspects of the present application relate to signaling exchanges. FIG. 26 shows an example signal flow diagram for signal flow between the UE 110L, the TRP 170, and the target UE 110T. First, the UE 110L transmits a capability report to the TRP 170 (step 2601). Then, the TRP 170 receives the capability report from the UE 110L (step 2602). Notably, at this point, the UE 110L is not yet a leader UE. Based on the capability report, the TRP 170 may select the UE 110L to be the leader UE (step 2604). As mentioned above, the leader need not be a UE. Instead, the leader may be a network node with appropriate capabilities for the leader. For simplicity, the leader will be referred to as the leader UE throughout this application.

[0198] Generally, the TRP 170 may select a leader UE 110L based on status, characteristics, and capabilities, such as location, synchronization status, and transmit power capabilities (step 2604). It may be the case that there is a preference to have one or more leader UEs 110L in different geographical parts of the network. In such a case, the location of the leader UE 110L may be a factor in the selection of the leader UE (step 2604). To this end, all potential leader UEs 110L may be expected to provide capability reports to the TRP 170.

[0199] In response to the selection (step 2604), the TRP 170 may transmit a selection indication to the leader UE 110L indicating that the leader UE 110L has been selected (step 2606). The selection indication may be transmitted to the leader UE 110L via control signaling (e.g., RRC signaling or MAC-CE) (step 2606). The TRP 170 then transmits information about the configuration of the synchronization chirp signal and the access chirp signal to the leader UE 110L (step 2608). The TRP 170 may also transmit information about the configuration of the synchronization chirp signal and the access chirp signal to the target UE 110T before the target UE 110T enters the low power mode (step 2608). The transmission of the configuration information (step 2608) may be achieved, in one example, using RRC configuration signaling. As described with reference to FIG. 23, the leader UE 110L receives the chirp signal configuration (step 2302).

[0200] Next, leader UE 110L may transmit a synchronization chirp signal based on the defined configuration (step 2610). As described with reference to Figure 22, target UE 110T receives the synchronization chirp signal (step 2202). As described with reference to Figure 11, target UE 110T performs measurements on the received synchronization chirp signal (step 1106).

[0201] As a result of processing the measurements of the synchronization chirp signal (see steps 2204, 2206, and 2208 in FIG. 22), the target UE 110T obtains an estimate of the synchronization offset (step 2212) and may correct the clock at the target UE 110T (step 2214). Furthermore, a portion of the access chirp signal configuration may be inferred from processing the measurements (steps 2204, 2206, and 2208 in FIG. 22). The target UE 110T transmits the access chirp signal based on the configuration (step 2210 in FIG. 22). The leader UE 110L receives the access chirp signal (step 2304 in FIG. 23), performs measurements (step 2306 in FIG. 23; step 1206 in FIG. 12), and prepares a measurement report. The leader UE 110L then transmits the measurement report to the TRP 170 (step 2310 in FIG. 23). The TRP 170 receives the measurement report (step 2612) and performs further processing.

[0202] Aspects of the present application relate to the manner in which details of the UE clock parameters may be estimated before the estimated clock parameters are used to modify the clock at the target UE 110T (step 2214 of FIG. 22).

[0203] In particular, the linear model t TRP =βt UE +γ is considered, where this linear model is UE (generally referred to as the "UE clock") and the time t TRP(generally referred to as the "network clock"). This linear model includes model parameters β and γ. FIG. 27 illustrates this linear model. In this linear model, the model parameter β is used to represent the rate of change of the difference between the frequency of the clock at the TRP 170 and the frequency of the clock at the target UE 110T. In this linear model, the model parameter γ is used to represent constant clock drift. Ideally, it would be preferable to have β = 1 and γ = 0. However, this is not the case in practice. This deviation from the ideal provides an incentive to estimate the synchronization offset and then perform synchronization to compensate for it. Aspects of the present application relate to estimating the model parameters β and γ based on multiple measurements. Aspects of the present application relate to the target UE 110T, in low power mode, obtaining an estimate of the synchronization offset (step 2212 of FIG. 22) whenever a synchronization chirp signal is received from the leader UE 110L (step 2202 of FIG. 22). The target UE 110T may be configured to stack multiple measurements and perform linear regression to determine the model parameters β and γ. A larger deviation |β| between the estimated rate of change of the TRP / UE frequency difference and the ideal rate of change of the TRP / UE frequency difference may indicate that the synchronization offset increases more quickly over time. In such cases, synchronization should occur more frequently. Consequently, the frequency at which the target UE 110T synchronizes may be adjusted in a manner proportional to the estimated value |β|.

[0204] It should be understood that one or more steps of the method of the embodiments provided herein may be performed by a corresponding unit or module. For example, data may be transmitted by a transmitting unit or a transmitting module. Data may be received by a receiving unit or a receiving module. Data may be processed by a processing unit or a processing module. Each unit / module may be hardware, software, or a combination thereof. For example, one or more of the units / modules may be an integrated circuit, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). When such modules are software, it should be understood that the modules may be retrieved by a processor for processing, individually or together, in whole or in part, as needed, in a single instance or multiple instances, as needed, and the modules themselves may include instructions for further deployment and instantiation.

[0205] Although combinations of features are shown in the illustrated embodiments, not all of them need to be combined to realize the benefits of various embodiments of the present disclosure. In other words, a system or method designed in accordance with an embodiment of the present disclosure does not necessarily include all of the features shown in any one of the figures or all of the portions shown schematically in the figures. Furthermore, selected features of one exemplary embodiment may be combined with selected features of other exemplary embodiments.

[0206] While the present disclosure has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to this description. Accordingly, the appended claims are intended to cover any and all such modifications or embodiments.

Claims

1. 1. A method executing on a first device, comprising: receiving a chirp signal configuration, the chirp signal configuration including configuration information for a first chirp signal; While the first device is in a low power mode of operation, receiving the first chirp signal from a second device; performing measurements on the first chirp signal to obtain an estimated synchronization offset between a first clock at the first device and a second clock at the second device; and correcting the first clock based on the estimated synchronization offset. A method comprising:

2. 2. The method of claim 1, wherein the chirp signal configuration includes configuration information of a second chirp signal, the method further comprising transmitting the second chirp signal according to the configuration information of the second chirp signal.

3. 3. The method of claim 2, further comprising inferring second chirp signal configuration parameters from the measurements on the first chirp signal, and wherein transmitting the second chirp signal comprises transmitting the second chirp signal in accordance with the second chirp signal configuration parameters.

4. 4. The method of claim 1, wherein the step of performing measurements on the first chirp signal comprises the step of matched filtering the received first chirp signal.

5. 5. The method of claim 1, wherein the step of performing measurements on the first chirp signal comprises obtaining a beat frequency of the first chirp signal.

6. a first device, a first clock; receiving a chirp signal configuration, the chirp signal configuration including configuration information of a first chirp signal; and receiving the first chirp signal from a second device; a receiver adapted to perform the steps; a memory storing instructions; and Executing the instructions while the first device is in a low power mode of operation; performing measurements on the first chirp signal to obtain an estimated synchronization offset between the first clock and a second clock at the second device; and correcting the first clock based on the estimated synchronization offset; A processor that is made to perform a first device comprising:

7. 1. A method executing on a first device, comprising: receiving a chirp signal configuration, the chirp signal configuration including configuration information for a first chirp signal; While the second device is in a low power operating mode, transmitting the first chirp signal to the second device according to the configuration information of the first chirp signal; receiving a second chirp signal from the second device; obtaining measurements on the second chirp signal to determine that the second chirp signal is intended for the first device; and transmitting a measurement report based on the measurements on the second chirp signal to a third device. A method comprising:

8. The method of claim 7 , further comprising transmitting a capability report to the third device.

9. The method of claim 8 , wherein the capability report includes an indication of a location of the first device.

10. The method of claim 8 or claim 9, wherein the capability report includes an indication of a synchronization status of the first device.

11. The method of claim 8 , wherein the capability report includes an indication of a transmit power capability of the first device.

12. 12. The method of claim 7, further comprising transmitting the configuration information of the first chirp signal to the second device before the second device enters a low power mode and before transmitting the first chirp signal.

13. 13. The method of claim 7, further comprising transmitting configuration information of a second chirp signal to the second device before the second device enters a low power mode.

14. a first device, receiving a chirp signal configuration, the chirp signal configuration including configuration information of a first chirp signal; and receiving a second chirp signal from a second device; a receiver adapted to perform the steps; a transmitter adapted to transmit the first chirp signal to the second device in accordance with the configuration information of the first chirp signal while the second device is in a low power mode of operation; a memory storing instructions; and Executing the instructions while the second device is in a low power mode of operation; obtaining measurements on the second chirp signal to determine that the second chirp signal is intended for the first device; and transmitting a measurement report based on the measurements on the second chirp signal to a third device using the transmitter. A processor that is made to perform a first device comprising:

15. transmitting, at the first device, configuration details of a first chirp signal to the second device before the second device enters a low power mode; transmitting configuration details of the second chirp signal to a third device; receiving a report from the third device including measurements made at the third device on the first chirp signal; and processing the measurements A method for providing the above.

16. receiving a capability report from the third device; selecting the third device for transmitting the second chirp signal to the second device based on the contents of the capability report; and transmitting an indication to the third device that the third device has been selected. The method of claim 15 further comprising:

17. 17. The method of claim 15 or claim 16, further comprising transmitting the configuration details of the second chirp signal to the second device.

18. 18. The method of any one of claims 15 to 17, further comprising transmitting the configuration details of the first chirp signal to the third device.

19. transmitting configuration details of a first chirp signal to a second device before the second device enters a low power mode; and transmitting configuration details of the second chirp signal to a third device; a transmitter adapted to perform the steps; a receiver adapted to receive a report from the third device including measurements made at the third device on the first chirp signal; a memory storing instructions; and a processor caused to process said measurements by executing said instructions. a first device comprising:

20. 20. A non-transitory computer readable medium having stored thereon programming for execution by a processor, the programming including instructions for performing the method of any one of claims 1 to 5, 7 to 13, and 15 to 18.

21. 19. A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the method of any one of claims 1 to 5, 7 to 13 and 15 to 18.

22. 19. An apparatus comprising a processor, the processor configured to cause the apparatus to perform a method according to any one of claims 1 to 5, 7 to 13 and 15 to 18.

23. A processor of an apparatus, the processor being configured to cause the apparatus to perform a method according to any one of claims 1 to 5, 7 to 13 and 15 to 18.

24. a first device configured to transmit a first chirp signal; and a second device configured to receive the first chirp signal, obtain an estimated synchronization offset between a first clock at the first device and a second clock at the second device, and transmit a second chirp signal to the first device to indicate an association between the first device and the second device. A system comprising:

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