Time slot format for a reference radar signal and at least one target radar signal between base stations

Abstract

In one aspect, a radar controller determines a radar time slot format that configures the transmission of a reference radar signal on a first symbol over a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; and transmits an indication of the radar time slot format to the first base station and the second base station. The first base station transmits the reference radar signal and the at least one target radar signal according to the radar time slot format, and the second base station receives the reference radar signal and the at least one target radar signal according to the radar time slot format.

Description

[0001] Cross - Reference to Related Applications

[0002] This patent application claims the benefit of U.S. Provisional Application No. 63 / 088,096, filed on October 6, 2020, entitled "SLOT FORMAT FOR REFERENCE RADAR SIGNAL AND AT LEAST ONE TARGET RADAR SIGNAL BETWEEN BASE STATIONS", and U.S. Non - Provisional Application No. 17 / 461,397, filed on August 30, 2021, entitled "SLOT FORMAT FOR REFERENCE RADAR SIGNAL AND AT LEAST ONE TARGET RADAR SIGNAL BETWEEN BASE STATIONS", both of which are assigned to the assignee of this application and are hereby incorporated by reference in their entirety.

[0003] BACKGROUND OF THE DISCLOSURE

[0004] 1. Field of the Disclosure

[0005] Aspects of the present disclosure generally relate to wireless communication, and more particularly to slot formats for reference radar signals and at least one target radar signal between base stations.

[0006] 2. Description of the Related Art

[0007] Wireless communication systems have evolved through several generations, including first - generation analog wireless telephone service (1G), second - generation (2G) digital wireless telephone service (including transitional 2.5G and 2.75G networks), third - generation (3G) high - speed data wireless services with Internet capabilities, and fourth - generation (4G) services (e.g., Long - Term Evolution (LTE) or WiMax). There are many different types of wireless communication systems currently in use, including cellular and personal communication service (PCS) systems. Examples of known cellular systems include the cellular analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), etc.

[0008] The fifth generation (5G) wireless standard (referred to as New Radio (NR)) requires higher data transfer speeds, a larger number of connections, better coverage, and other improvements. According to the Next Generation Mobile Networks Alliance, the 5G standard is designed to provide data rates of tens of megabits per second to each of thousands of users and 1 gigabit per second to dozens of employees in an office floor. Hundreds of thousands of simultaneous connections should be supported to enable large-scale sensor deployments. Therefore, the spectral efficiency of 5G mobile communications should be significantly improved compared to the current 4G standard. In addition, signaling efficiency should be improved and latency should be greatly reduced compared to the current standard.

[0009] 5G enables the use of mmW RF signals for wireless communication between network nodes such as base stations, user equipment (UE), vehicles, factory automation machines, etc. However, mmW RF signals can also be used for other purposes. For example, mmW RF signals can be used in weapon systems (e.g., as short-range fire control radars in tanks and aircraft), security screening systems (e.g., in scanners for detecting weapons and other dangerous items carried under clothing), medicine (e.g., treating diseases by altering cell growth), etc.

[0010] Overview

[0011] A simplified overview related to one or more aspects disclosed herein is given below. Accordingly, the following overview should neither be considered an exhaustive survey of all contemplated aspects, nor should the following overview be considered to identify critical or decisive elements related to all contemplated aspects or to delineate the scope associated with any particular aspect. Accordingly, the sole purpose of the following overview is to present in a simplified form certain concepts related to one or more aspects regarding the mechanisms disclosed herein prior to the detailed description given below.

[0012] In one aspect, a method of operating a radar controller includes: determining a radar time slot format that configures the transmission of a reference radar signal on a first symbol over a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; and transmitting an indication of the radar time slot format to the first base station and the second base station.

[0013] In one aspect, a method of operating a first base station includes: receiving a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; transmitting the reference radar signal on the first symbol via the first link from the first base station to the second base station; and transmitting the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0014] In one aspect, a method of operating a second base station includes: receiving a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from a first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; receiving the reference radar signal on the first symbol via the first link from the first base station to the second base station; and receiving the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0015] In one aspect, a radar controller includes: a memory, at least one transceiver, and at least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor configured to: determine a radar time slot format, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; and transmit an indication of the radar time slot format to the first base station and the second base station via the at least one transceiver.

[0016] Based on the figures and the detailed description, other objectives and advantages associated with the aspects disclosed herein will be apparent to those skilled in the art. Brief Description of the Drawings

[0018] The accompanying drawings are provided to assist in describing one or more examples of the disclosed subject matter and are provided only for illustration of the examples and not for limitation thereof:

[0019] Figure 1 An example wireless communication system in accordance with aspects of the present disclosure is illustrated.

[0020] Figure 2A and Figure 2BIllustrates an example wireless network architecture in accordance with various aspects of the present disclosure.

[0021] Figures 3A to 3C Is a simplified block diagram of several exemplary aspects of components that can be employed in a wireless communication node and configured to support communication as taught herein.

[0022] Figure 4A And 4B Is a diagram illustrating examples of frame structures in accordance with aspects of the present disclosure and channels within these frame structures.

[0023] Figure 5A Illustrates an example monostatic radar system.

[0024] Figure 5B Illustrates an example bistatic radar system.

[0025] Figure 5C Is an example graph showing the radio frequency (RF) channel response over time.

[0026] Figure 6 Illustrates an example single-target beam management use case for bistatic RF sensing.

[0027] Figure 7 Illustrates an example multi-target beam management use case for bistatic RF sensing.

[0028] Figure 8A Illustrates an example scanning phase employing bistatic RF sensing.

[0029] Figure 8B Illustrates an example tracking phase employing bistatic RF sensing.

[0030] Figure 9 Is a simplified diagram showing the basic operation of a bistatic radar system.

[0031] Figure 10 Illustrates the implementation of a bistatic radar system in a wireless communication system in accordance with an embodiment of the present disclosure.

[0032] Figure 11 Is a block diagram of a wireless communication system that may include a radar controller in accordance with an embodiment of the present disclosure.

[0033] Figure 12 Shows an example of a list of radar configuration parameters provided by a radar server to a TX base station and an RX base station for a bistatic or multistatic radar measurement session in accordance with an embodiment of the present disclosure.

[0034] Figure 13 Shows an example of a TX / RX timing sub-list in accordance with embodiments of the present disclosure.

[0035] Figure 14 An example of a Doppler sub - list according to embodiments of the present disclosure is shown.

[0036] Figure 15 An exemplary communication process according to aspects of the present disclosure is illustrated.

[0037] Figure 16 An exemplary wireless communication process according to aspects of the present disclosure is illustrated.

[0038] Figure 17 An exemplary wireless communication process according to aspects of the present disclosure is illustrated.

[0039] Figure 18A A radar time - slot format according to a first aspect of the present disclosure is illustrated.

[0040] Figure 18B A radar time - slot format according to a second aspect of the present disclosure is illustrated.

[0041] Detailed description

[0042] Aspects of the present disclosure are provided in the following description of various examples provided for illustrative purposes and the associated drawings. Alternative aspects may be designed without departing from the scope of the present disclosure. Additionally, elements well - known in the art will not be described in detail or will be omitted so as not to obscure the relevant details of the present disclosure.

[0043] The terms "exemplary" and / or "example" are used herein to mean "serving as an example, instance, or illustration". Any aspect described herein as "exemplary" and / or "example" need not be construed as superior to or better than other aspects. Similarly, the term "aspects of the present disclosure" does not require that all aspects of the present disclosure include the discussed features, advantages, or modes of operation.

[0044] Those skilled in the art will appreciate that the information and signals described below may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the following description may be represented, in part, depending on the specific application, in part, depending on the desired design, in part, depending on the corresponding technology, etc., by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0045] In addition, many aspects are described in the form of sequences of actions performed by elements of, for example, a computing device. It will be recognized that the various actions described herein can be performed by special purpose circuitry (e.g., application specific integrated circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, the sequences of actions described herein can be considered to be fully embodied within any form of non-transitory computer-readable storage medium having stored therein a corresponding set of computer instructions that, when executed, cause or direct a relevant processor of the device to perform the functionality described herein. Thus, the various aspects of the present disclosure can be embodied in several different forms, all of which are contemplated as being within the scope of the claimed subject matter. Additionally, for each aspect described herein, any such aspect's corresponding form can be described herein as, for example, "logic configured to perform the described actions."

[0046] As used herein, the terms "user equipment" (UE) and "base station" (BS) are not intended to be dedicated to or otherwise limited to any particular radio access technology (RAT) unless otherwise specified. In general, a UE can be any wireless communication device (e.g., a mobile phone, router, tablet computer, laptop computer, tracking device, wearable device (e.g., smart watch, glasses, augmented reality (AR) / virtual reality (VR) headsets, etc.), vehicle (e.g., car, motorcycle, bicycle, etc.), Internet of Things (IoT) device, etc.) used by a user to communicate over a wireless communication network. A UE can be mobile or can be stationary (e.g., at certain times) and can communicate with a radio access network (RAN). As used herein, the term "UE" can be interchangeably referred to as "access terminal" or "AT", "client device", "wireless device", "subscriber equipment", "subscriber terminal", "subscriber station", "user terminal" or UT, "mobile device", "mobile terminal", "mobile station", or variants thereof. In general, a UE can communicate with a core network via a RAN, and through the core network, a UE can connect to an external network (such as the Internet) and to other UEs. Of course, other mechanisms for connecting to the core network and / or the Internet are possible for a UE, such as via a wired access network, a wireless local area network (WLAN) network (e.g., based on IEEE 802.11, etc.).

[0047] A base station can operate according to one of several RATs depending on the network in which the base station is deployed to communicate with a UE, and can alternatively be referred to as an access point (AP), network node, B node, evolved B node (eNB), next-generation eNB (ng-eNB), New Radio (NR) B node (also referred to as gNB or gNodeB), etc. The base station can be mainly used to support wireless access by the UE, including supporting data, voice, and / or signaling connections for the supported UEs. In some systems, the base station can provide a pure edge node signaling function, while in other systems, the base station can provide additional control and / or network management functions. The communication link by which the UE can send signals to the base station is referred to as the uplink (UL) channel (e.g., reverse traffic channel, reverse control channel, access channel, etc.). The communication link by which the base station can send signals to the UE is referred to as the downlink (DL) or forward link channel (e.g., paging channel, control channel, broadcast channel, forward traffic channel, etc.). As used herein, the term traffic channel (TCH) can refer to the uplink / reverse traffic channel or the downlink / forward traffic channel.

[0048] The term "base station" can refer to a single physical transmit receive point (TRP) or can refer to multiple physical TRPs that may or may not be co-located. For example, in the case where the term "base station" refers to a single physical TRP, the physical TRP can be the base station antenna corresponding to a cell (or several cell sectors) of the base station. In the case where the term "base station" refers to multiple co-located physical TRPs, the physical TRPs can be an antenna array of the base station (e.g., as in a multiple-input multiple-output (MIMO) system or when the base station employs beamforming). In the case where the term "base station" refers to multiple non-co-located physical TRPs, the physical TRPs can be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transmission medium) or a remote radio head (RRH) (a remote base station connected to a serving base station). Alternatively, the non-co-located physical TRPs can be the serving base station that receives measurement reports from the UE and a neighbor base station whose reference RF signal (or simply "reference signal") the UE is measuring. Since the TRP is the point from which the base station transmits and receives wireless signals, as used herein, a reference to a transmission from the base station or a reception at the base station should be understood to refer to the specific TRP of the base station.

[0049] In some implementations that support UE positioning, a base station may not support wireless access by the UE (e.g., may not support data, voice, and / or signaling connections for the UE), but may alternatively transmit reference signals to be measured by the UE and / or may receive and measure signals transmitted by the UE. Such a base station may be referred to as a positioning tower (e.g., in the case of transmitting signals to the UE) and / or as a position measurement unit (e.g., in the case of receiving and measuring signals from the UE).

[0050] An "RF signal" includes an electromagnetic wave of a given frequency that transmits information through the space between a transmitter and a receiver. As used herein, a transmitter may transmit a single "RF signal" or multiple "RF signals" to a receiver. However, due to the propagation characteristics of each RF signal through a multipath channel, a receiver may receive multiple "RF signals" corresponding to each transmitted RF signal. The same RF signal transmitted on different paths between a transmitter and a receiver may be referred to as a "multipath" RF signal. As used herein, an RF signal may also be referred to as a "wireless signal" or simply as a "signal", where it is clear from the context that the term "signal" refers to a wireless signal or an RF signal.

[0051] Referring to Figure 1 , an example wireless communication network 100 is shown. The wireless communication system 100 (which may also be referred to as a wireless wide area network (WWAN)) may include various base stations 102 and various UEs 104. The base stations 102 may include macrocell base stations (high-power cell base stations) and / or small cell base stations (low-power cell base stations). In one aspect, the macrocell base stations may include eNBs and / or ng-eNBs (where the wireless communication system 100 corresponds to an LTE network), or gNBs (where the wireless communication system 100 corresponds to an NR network), or a combination of both, and the small cell base stations may include femtocells, picocells, microcells, etc.

[0052] Each base station 102 may jointly form a RAN and interface with a core network 170 (e.g., an evolved packet core (EPC) or a 5G core (5GC)) via a backhaul link 122, and be connected to one or more location servers 172 (which may be part of the core network 170 or external to the core network 170) through the core network 170. In addition to other functions, the base station 102 may also perform functions related to one or more of transmitting user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, multimedia broadcast multicast service (MBMS), subscriber and device tracking, RAN information management (RIM), paging, positioning, and delivery of alert messages. The base stations 102 may communicate with each other directly or indirectly (e.g., through the EPC / 5GC) via a backhaul link 134 (which may be wired or wireless).

[0053] The base station 102 may communicate wirelessly with the UE 104. Each base station 102 may provide communication coverage for its respective geographic coverage area 110. In one aspect, one or more cells may be supported by the base stations 102 in each geographic coverage area 110. A "cell" is a logical communication entity for communicating with a base station (e.g., on a certain frequency resource, referred to as a carrier frequency, component carrier, carrier, frequency band, etc.), and may be associated with an identifier (e.g., a physical cell identifier (PCI), a virtual cell identifier (VCI), a cell global identifier (CGI)) to distinguish cells operating via the same or different carrier frequencies. In some cases, different cells may be configured according to different protocol types that may provide access for different types of UEs (e.g., machine type communication (MTC), narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB), or others). Since a cell is supported by a specific base station, the term "cell" may, depending on the context, refer to either the logical communication entity or the base station that supports the logical communication entity, or both. Additionally, since the TRP is typically the physical transmission point of a cell, the terms "cell" and "TRP" may be used interchangeably. In some cases, the term "cell" may also refer to the geographic coverage area (e.g., a sector) of a base station in the sense that a carrier frequency can be detected and used for communication within a certain portion of the geographic coverage area 110.

[0054] Although the respective geographical coverage areas 110 of adjacent macro cell base stations 102 may partially overlap (e.g., in a handover area), some geographical coverage areas 110 may be substantially overlapped by larger geographical coverage areas 110. For example, a small cell base station 102' may have a geographical coverage area 110' that substantially overlaps the geographical coverage areas 110 of one or more macro cell base stations 102. A network including both small cells and macro cell base stations may be referred to as a heterogeneous network. The heterogeneous network may further include a home evolved Node B (HeNB) that may serve a restricted group referred to as a closed subscriber group (CSG).

[0055] The communication link 120 between the base station 102 and the UE 104 may include an uplink (also referred to as a reverse link) transmission from the UE 104 to the base station 102 and / or a downlink (also referred to as a forward link) transmission from the base station 102 to the UE 104. The communication link 120 may use MIMO antenna technology, including spatial multiplexing, beamforming, and / or transmit diversity. The communication link 120 may be over one or more carrier frequencies. The allocation of carriers may be asymmetric with respect to the downlink and the uplink (e.g., more or fewer carriers may be allocated to the downlink compared to the uplink).

[0056] The wireless communication system 100 may further include a wireless local area network (WLAN) access point (AP) 150 in communication with a WLAN station (STA) 152 via a communication link 154 in an unlicensed spectrum (e.g., 5 GHz). When communicating in an unlicensed spectrum, the WLAN STA 152 and / or the WLAN AP 150 may perform a clear channel assessment (CCA) or listen-before-talk (LBT) procedure to determine if the channel is available before communicating.

[0057] The small cell base station 102' may operate in a licensed and / or unlicensed spectrum. When operating in an unlicensed spectrum, the small cell base station 102' may employ LTE or NR technology and use the same 5 GHz unlicensed spectrum as that used by the WLAN AP 150. The small cell base station 102' adopting LTE / 5G in an unlicensed spectrum may boost the coverage of the access network and / or increase the capacity of the access network. NR in an unlicensed spectrum may be referred to as NR-U. LTE in an unlicensed spectrum may be referred to as LTE-U, licensed-assisted access (LAA), or MulteFire.

[0058] The wireless communication system 100 may further include a millimeter wave (mmW) base station 180, which may operate at mmW frequencies and / or near mmW frequencies to communicate with a UE 182. Extremely high frequency (EHF) is a part of RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in this frequency band may be referred to as millimeter waves. Near mmW may extend down to 3 GHz frequency with a 100 millimeter wavelength. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, which is also referred to as centimeter waves. Communication using the mmW / near mmW radio frequency band has high path loss and a relatively short range. The mmW base station 180 and the UE 182 may utilize beamforming (transmission and / or reception) on the mmW communication link 184 to compensate for the extremely high path loss and short range. Additionally, it will be appreciated that in an alternative configuration, one or more base stations 102 may also use mmW or near mmW along with beamforming for transmission. Accordingly, it will be appreciated that the foregoing explanation is merely an example and should not be construed as limiting the various aspects disclosed herein.

[0059] Transmit beamforming is a technique for focusing an RF signal in a specific direction. Conventionally, when a network node (e.g., a base station) broadcasts an RF signal, the network node broadcasts the signal in all directions (omnidirectionally). With transmit beamforming, the network node determines where a given target device (e.g., a UE) is located (relative to the transmitting network node) and projects a stronger downlink RF signal in that specific direction, thereby providing a faster (in terms of data rate) and stronger RF signal to the receiving device. To change the directivity of the RF signal during transmission, the network node may control the phase and relative amplitude of the RF signal at each of one or more transmitters that are broadcasting the RF signal. For example, the network node may use an antenna array (referred to as a "phased array" or "antenna array") that generates a beam of RF waves, and the beam of RF waves can be "steered" to point in different directions without actually moving the antennas. Specifically, the RF currents from the transmitters are fed to the individual antennas in the correct phase relationship so that the radio waves from the separate antennas add together in the desired direction to increase radiation, while canceling in the non-desired directions to suppress radiation.

[0060] Transmission beams can be quasi - co - located, meaning that they appear to have the same parameters to the receiving party (e.g., UE), regardless of whether the transmitting antennas of the network nodes are physically co - located themselves. In NR, there are four types of quasi - co - location (QCL) relationships. Specifically, a given type of QCL relationship means that certain parameters of a second reference RF signal on a second beam can be derived from information about a source reference RF signal on a source beam. Thus, if the source reference RF signal is QCL type A, the receiver can use the source reference RF signal to estimate the Doppler shift, Doppler spread, average delay, and delay spread of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL type B, the receiver can use the source reference RF signal to estimate the Doppler shift and Doppler spread of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL type C, the receiver can use the source reference RF signal to estimate the Doppler shift and average delay of the second reference RF signal transmitted on the same channel. If the source reference RF signal is QCL type D, the receiver can use the source reference RF signal to estimate the spatial reception parameters of the second reference RF signal transmitted on the same channel.

[0061] In receive beamforming, the receiver uses a receive beam to amplify the RF signals detected on a given channel. For example, the receiver can increase the gain setting of the antenna array and / or adjust the phase setting of the antenna array in a specific direction to amplify the RF signals received from that direction (e.g., increase its gain level). Thus, when the receiver is said to be beamforming in a certain direction, it means that the beam gain in that direction is higher relative to the beam gains in other directions, or the beam gain in that direction is the highest compared to the beam gains of all other receive beams available to the receiver in that direction. This results in a stronger received signal strength (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), signal - to - interference - plus - noise ratio (SINR), etc.) for the RF signals received from that direction.

[0062] The receiving beam can be spatially related. Spatial relationship means that the parameters of the transmitting beam for the second reference signal can be derived from the information on the receiving beam of the first reference signal. For example, a UE can use a specific receiving beam to receive one or more reference downlink reference signals from a base station (e.g., positioning reference signal (PRS), tracking reference signal (TRS), phase tracking reference signal (PTRS), cell-specific reference signal (CRS), channel state information reference signal (CSI-RS), primary synchronization signal (PSS), secondary synchronization signal (SSS), synchronization signal block (SSB), etc.). The UE can then form a transmitting beam based on the parameters of the receiving beam for transmitting one or more uplink reference signals to the base station (e.g., uplink positioning reference signal (UL-PRS), sounding reference signal (SRS), demodulation reference signal (DMRS), PTRS, etc.).

[0063] Note that depending on the entity forming the "downlink" beam, the beam can be a transmitting beam or a receiving beam. For example, if the base station is forming a downlink beam to transmit a reference signal to the UE, the downlink beam is a transmitting beam. However, if the UE is forming a downlink beam, the downlink beam is a receiving beam for receiving downlink reference signals. Similarly, depending on the entity forming the "uplink" beam, the beam can be a transmitting beam or a receiving beam. For example, if the base station is forming an uplink beam, the uplink beam is an uplink receiving beam, and if the UE is forming an uplink beam, the uplink beam is an uplink transmitting beam.

[0064] In 5G, the spectrum in which wireless nodes (e.g., base stations 102 / 180, UEs 104 / 182) operate is divided into multiple frequency ranges: FR1 (from 450 to 6000 MHz), FR2 (from 24250 to 52600 MHz), FR3 (above 52600 MHz), and FR4 (between FR1 and FR2). In a multi-carrier system such as 5G, one of the carrier frequencies is referred to as the "primary carrier" or "anchor carrier" or "primary serving cell" or "PCell", and the remaining carrier frequencies are referred to as "secondary carriers" or "secondary serving cells" or "SCells". In carrier aggregation, the anchor carrier is the carrier that operates on the primary frequency (e.g., FR1) utilized by the UE 104 / 182 and on the cell in which the UE 104 / 182 performs the initial radio resource control (RRC) connection establishment procedure or initiates the RRC connection reestablishment procedure. The primary carrier carries all common control channels and UE-specific control channels, and can be a carrier in a licensed frequency (however, this is not always the case). The secondary carrier is a carrier that operates on a second frequency (e.g., FR2) and can be configured once an RRC connection is established between the UE 104 and the anchor carrier, and this carrier can be used to provide additional radio resources. In some cases, the secondary carrier can be a carrier in an unlicensed frequency. The secondary carrier may only contain necessary signaling information and signals. For example, UE-specific signaling information and signals may not exist in the secondary carrier because both the primary uplink and downlink carriers are typically UE-specific. This means that different UEs 104 / 182 in a cell can have different downlink primary carriers. The same holds true for the uplink primary carrier. The network is able to change the primary carrier of any UE 104 / 182 at any time. For example, this is done to balance the load on different carriers. Since the "serving cell" (whether it is a PCell or an SCell) corresponds to the carrier frequency / component carrier that a certain base station is using for communication, the terms "cell", "serving cell", "component carrier", "carrier frequency", etc. can be used interchangeably.

[0065] For example, still referring to Figure 1 , one of the frequencies utilized by the macro cell base station 102 can be the anchor carrier (or "PCell"), and the other frequencies utilized by this macro cell base station 102 and / or the mmW base station 180 can be secondary carriers ("Scells"). The simultaneous transmission and / or reception of multiple carriers enables the UE 104 / 182 to significantly increase its data transmission and / or reception rate. For example, two 20 MHz aggregated carriers in a multi-carrier system would theoretically result in a two-fold increase in the data rate (i.e., 40 MHz) compared to the data rate obtained by a single 20 MHz carrier.

[0066] The wireless communication system 100 may further include a UE 164 that may communicate with the macro cell base station 102 over the communication link 120 and / or with the mmW base station 180 over the mmW communication link 184. For example, the macro cell base station 102 may support a PCell and one or more SCell for the UE 164, and the mmW base station 180 may support one or more SCell for the UE 164.

[0067] The wireless communication system 100 may further include one or more UEs (such as UE 190) that are indirectly connected to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links (referred to as "sidelinks"). In Figure 1 the example, the UE 190 has a D2D P2P link 192 with a UE 104 connected to a base station 102 (e.g., the UE 190 may thereby indirectly obtain cellular connectivity), and a D2D P2P link 194 with a WLAN STA 152 connected to a WLAN AP 150 (the UE 190 may thereby indirectly obtain WLAN-based Internet connectivity). In one example, the D2D P2P links 192 and 194 may use any known D2D RAT (such as LTE Direct (LTE-D), WiFi Direct (WiFi-D), etc.) to support.

[0068] Referring to Figure 2A , an example wireless network architecture 200 is shown. For example, the 5GC 210 (also referred to as the Next Generation Core (NGC)) may be functionally regarded as a control plane function 214 (e.g., UE registration, authentication, network access, gateway selection, etc.) and a user plane function 212 (e.g., UE gateway function, access to data networks, IP routing, etc.), which operate cooperatively to form the core network. The user plane interface (NG-U) 213 and the control plane interface (NG-C) 215 connect the gNB 222 to the 5GC 210, particularly to the control plane function 214 and the user plane function 212. In an additional configuration, the ng-eNB 224 may also be connected to the 5GC 210 via the NG-C 215 to the control plane function 214 and the NG-U 213 to the user plane function 212. In addition, the ng-eNB 224 may communicate directly with the gNB 222 via the backhaul connection 223. In some configurations, the new RAN 220 may have only one or more gNB 222s, while other configurations include both one or more ng-eNB 224s and one or more gNB 222s. The gNB 222 or ng-eNB 224 may communicate with the UE 204 (e.g., Figure 1communicate with any UE depicted in []. Another optional aspect may include a location server 230 that may be in communication with the 5GC 210 to provide location assistance for the UE 204. The location server 230 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules scaled across multiple physical servers, etc.), or alternatively may each correspond to a single server. The location server 230 may be configured to support one or more location services for the UE 204, and the UE 204 can be connected to the location server 230 via the core network, the 5GC 210, and / or via the Internet (not illustrated). Additionally, the location server 230 may be integrated into a component of the core network, or alternatively may be external to the core network.

[0069] Referring to Figure 2B , another example wireless network architecture 250 is shown. For example, the 5GC 260 may be functionally regarded as a control plane function (provided by the Access and Mobility Management Function (AMF) 264) and a user plane function (provided by the User Plane Function (UPF) 262), which operate cooperatively to form the core network (i.e., the 5GC 260). The user plane interface 263 and the control plane interface 265 connect the ng-eNB 224 to the 5GC 260, particularly to the UPF 262 and the AMF 264 respectively. In an additional configuration, the gNB 222 may also be connected to the 5GC 260 via the control plane interface 265 to the AMF 264 and the user plane interface 263 to the UPF 262. Additionally, the ng-eNB 224 may communicate directly with the gNB 222 via a backhaul connection 223 with or without direct connectivity of the gNB to the 5GC 260. In some configurations, the new RAN 220 may have only one or more gNB 222s, while other configurations include both one or more ng-eNB 224s and one or more gNB 222s. The gNB 222 or the ng-eNB 224 may communicate with the UE 204 (e.g., Figure 1 any UE depicted in []. The base stations of the new RAN 220 communicate with the AMF 264 via the N2 interface and with the UPF 262 via the N3 interface.

[0070] The functions of the AMF 264 include registration management, connection management, reachability management, mobility management, lawful interception, transmission of session management (SM) messages between the UE 204 and the session management function (SMF) 266, transparent proxy service for routing SM messages, access authentication and access authorization, transmission of short message service (SMS) messages between the UE 204 and the short message service function (SMSF) (not shown), and security anchor functionality (SEAF). The AMF 264 also interacts with the authentication server function (AUSF) (not shown) and the UE 204, and receives the intermediate key established as a result of the UE 204 authentication process. In the case of authentication based on a UMTS (Universal Mobile Telecommunications System) subscriber identity module (USIM), the AMF 264 retrieves the security material from the AUSF. The functions of the AMF 264 also include security context management (SCM). The SCM receives a key from the SEAF, which the SCM uses to derive the access network-dependent key. The functionality of the AMF 264 also includes: location service management for regulatory services, transmission of location service messages between the UE 204 and the location management function (LMF) 270 (which acts as the location server 230), transmission of location service messages between the new RAN 220 and the LMF 270, EPS bearer identifier allocation for interoperability with the evolved packet system (EPS), and UE 204 mobility event notification. In addition, the AMF 264 also supports the functionality of non-3GPP access networks.

[0071] The functions of the UPF 262 include: acting as an anchor point for intra-RAT / inter-RAT mobility (when applicable), acting as an external protocol data unit (PDU) session point for interconnection to a data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, quality of service (QoS) handling for the user plane (e.g., uplink / downlink rate enforcement, reflexive QoS marking in the downlink), uplink traffic verification (service data flow (SDF) to QoS flow mapping), transport-level packet marking in the uplink and downlink, downlink packet buffering and downlink data notification triggering, and sending and forwarding one or more "end markers" to the source RAN node. The UPF 262 may also support the transmission of location service messages on the user plane between the UE 204 and a location server such as the secure user plane location (SUPL) location platform (SLP) 272.

[0072] The functions of the SMF 266 include session management, UE Internet Protocol (IP) address allocation and management, selection and control of the user plane function, traffic steering configuration at the UPF 262 for routing traffic to the correct destination, partial control of policy enforcement and QoS, and downlink data notification. The interface used by the SMF 266 to communicate with the AMF 264 is referred to as the N11 interface.

[0073] Another optional aspect may include an LMF 270, which may communicate with the 5GC 260 to provide location assistance for the UE 204. The LMF 270 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules spanning multiple physical servers, etc.), or alternatively may each correspond to a single server. The LMF 270 may be configured to support one or more location services for the UE 204, and the UE 204 may be able to connect to the LMF 270 via the core network, the 5GC 260, and / or via the Internet (not illustrated). The SLP 272 may support functions similar to those of the LMF 270, but the LMF 270 may communicate with the AMF 264, the new RAN 220, and the UE 204 on the control plane (e.g., using interfaces and protocols designed to convey signaling messages rather than voice or data), and the SLP 272 may communicate with the UE 204 and external clients ( Figure 2B not shown in the figure) on the user plane (e.g., using protocols designed to carry voice and / or data, such as the Transmission Control Protocol (TCP) and / or IP).

[0074] In one aspect, the LMF 270 and / or the SLP 272 may be integrated into a base station (such as the gNB 222 and / or the ng-eNB 224). When integrated into the gNB 222 and / or the ng-eNB 224, the LMF 270 and / or the SLP 272 may be referred to as a "location management component" or "LMC". However, as used herein, references to the LMF 270 and the SLP 272 include both the case where the LMF 270 and the SLP 272 are components of the core network (e.g., the 5GC 260) and the case where the LMF 270 and the SLP 272 are components of a base station.

[0075] Reference is made to Figure 3A 、 3BWith 3C, several example components (represented by the corresponding boxes) that can be incorporated into UE 302 (which can correspond to any UE described herein), base station 304 (which can correspond to any base station described herein), and network entity 306 (which can correspond to or embody any network function described herein, including location server 230 and LMF 270) to support file transfer operations are shown. It will be appreciated that these components can be implemented in different types of devices (e.g., in ASICs, in system-on-chip (SoC), etc.) in different implementations. The illustrated components can also be incorporated into other devices in the communication system. For example, other devices in the system can include components similar to those described to provide similar functionality. Additionally, a given device can include one or more of these components. For example, a device can include multiple transceiver components that enable the device to operate on multiple carriers and / or communicate via different technologies.

[0076] UE 302 and base station 304 each include a wireless wide area network (WWAN) transceiver 310 and 350, respectively, configured to communicate via one or more wireless communication networks (not shown) (such as an NR network, an LTE network, a GSM network, etc.). WWAN transceivers 310 and 350 can be connected to one or more antennas 316 and 356, respectively, for communicating with other network nodes (such as other UEs, access points, base stations (e.g., eNB, gNB), etc.) over an interested wireless communication medium (e.g., a set of time / frequency resources in a specific spectrum) via at least one designated RAT (e.g., NR, LTE, GSM, etc.). WWAN transceivers 310 and 350 can be configured in various ways according to the designated RAT to transmit and encode signals 318 and 358 (e.g., messages, indications, information, etc.), and conversely, to receive and decode signals 318 and 358 (e.g., messages, indications, information, pilots, etc.). Specifically, transceivers 310 and 350 each include one or more transmitters 314 and 354, respectively, for transmitting and encoding signals 318 and 358, and one or more receivers 312 and 352, respectively, for receiving and decoding signals 318 and 358.

[0077] At least in some cases, UE 302 and base station 304 also include wireless local area network (WLAN) transceivers 320 and 360, respectively. WLAN transceivers 320 and 360 can be connected to one or more antennas 326 and 366, respectively, for communicating via at least one designated RAT (e.g., WiFi, LTE-D, communicate with other network nodes (such as other UEs, access points, base stations, etc.) over a wireless communication medium of interest. The WLAN transceivers 320 and 360 can be configured in various ways according to the specified RAT to transmit and encode signals 328 and 368 (e.g., messages, indications, information, etc.) respectively, and vice versa to receive and decode signals 328 and 368 (e.g., messages, indications, information, pilots, etc.). Specifically, the transceivers 320 and 360 each include one or more transmitters 324 and 364 respectively for transmitting and encoding signals 328 and 368, and each include one or more receivers 322 and 362 respectively for receiving and decoding signals 328 and 368.

[0078] The transceiver circuitry including at least one transmitter and at least one receiver can include an integrated device (e.g., a transmitter circuit and a receiver circuit implemented as a single communication device) in some implementations, can include separate transmitter devices and separate receiver devices in some implementations, or can be implemented in other ways in other implementations. In one aspect, the transmitter can include or be coupled to a plurality of antennas such as an antenna array (e.g., antennas 316, 326, 356, 366), which permits the corresponding device to perform transmit "beamforming" as described herein. Similarly, the receiver can include or be coupled to a plurality of antennas such as an antenna array (e.g., antennas 316, 326, 356, 366), which permits the corresponding device to perform receive beamforming as described herein. In one aspect, the transmitter and the receiver can share the same plurality of antennas (e.g., antennas 316, 326, 356, 366) such that the corresponding device can only receive or transmit at a given time, not both simultaneously. The wireless communication devices of the UE 302 and / or the base station 304 (e.g., one or both of the transceivers 310 and 320 and / or one or both of the transceivers 350 and 360) can also include a network listening module (NLM) etc. for performing various measurements.

[0079] In at least some instances, UE 302 and base station 304 also include satellite positioning system (SPS) receivers 330 and 370. SPS receivers 330 and 370 may be respectively connected to one or more antennas 336 and 376 for respectively receiving SPS signals 338 and 378 (such as Global Positioning System (GPS) signals, Global Navigation Satellite System (GLONASS) signals, Galileo signals, Beidou signals, Indian Regional Navigation Satellite System (NAVIC), Quasi-Zenith Satellite System (QZSS), etc.). SPS receivers 330 and 370 may respectively include any suitable hardware and / or software for receiving and processing SPS signals 338 and 378. SPS receivers 330 and 370 request information and operations from other systems when appropriate and perform the necessary calculations to determine the positioning of UE 302 and base station 304 using measurements obtained by any suitable SPS algorithm.

[0080] Base station 304 and network entity 306 each include at least one network interface 380 and 390 for communicating with other network entities. For example, network interfaces 380 and 390 (e.g., one or more network access ports) may be configured to communicate with one or more network entities via a wired-based backhaul connection or a wireless backhaul connection. In some aspects, network interfaces 380 and 390 may be implemented as transceivers configured to support wired-based signal communication or wireless signal communication. This communication may involve, for example, sending and receiving: messages, parameters, and / or other types of information.

[0081] UE 302, base station 304, and network entity 306 also include other components that may be used in conjunction with the operations disclosed herein. UE 302 includes processor circuitry that implements a processing system 332 for providing, for example, functionality related to RF sensing and for providing other processing functionality. Base station 304 includes a processing system 384 for providing, for example, functionality related to RF sensing as disclosed herein and for providing other processing functionality. Network entity 306 includes a processing system 394 for providing, for example, functionality related to RF sensing as disclosed herein and for providing other processing functionality. In one aspect, processing systems 332, 384, and 394 may include, for example, one or more general-purpose processors, multi-core processors, ASICs, digital signal processors (DSPs), field programmable gate arrays (FPGAs), or other programmable logic devices or processing circuitry.

[0082] The UE 302, base station 304, and network entity 306 include memory circuitry that implements memory components 340, 386, and 396 (e.g., each including a memory device) for maintaining information (e.g., information indicating reserved resources, thresholds, parameters, etc.). In some cases, the UE 302, base station 304, and network entity 306 may include radar components 342, 388, and 398, respectively. The radar components 342, 388, and 398 may be hardware circuits that are part of or coupled to processing systems 332, 384, and 394, respectively, which when executed cause the UE 302, base station 304, and network entity 306 to perform the functionality described herein. In other aspects, the radar components 342, 388, and 398 may be external to the processing systems 332, 384, and 394 (e.g., part of a modem processing system, integrated with another processing system, etc.). Alternatively, the radar components 342, 388, and 398 may be memory modules stored in the memory components 340, 386, and 396 (as shown in Figures 3A - 3C ), which when executed by the processing systems 332, 384, and 394 (or a modem processing system, another processing system, etc.) cause the UE 302, base station 304, and network entity 306 to perform the functionality described herein.

[0083] The UE 302 may include one or more sensors 344 coupled to the processing system 332 to provide movement and / or orientation information that is independent of motion data derived from signals received by the WWAN transceiver 310, WLAN transceiver 320, and / or SPS receiver 330. As an example, the sensors 344 may include an accelerometer (e.g., a microelectromechanical systems (MEMS) device), a gyroscope, a geomagnetic sensor (e.g., a compass), an altimeter (e.g., a barometric altimeter), and / or any other type of motion detection sensor. Additionally, the sensors 344 may include multiple different types of devices and combine their outputs to provide motion information. For example, the sensors 344 may use a combination of a multi-axis accelerometer and an orientation sensor to provide the ability to calculate positioning in a 2D and / or 3D coordinate system.

[0084] Furthermore, the UE 302 includes a user interface 346 for providing indications (e.g., audible and / or visual indications) to the user and / or for receiving user input (e.g., upon the user actuating a sensing device such as a keypad, touch screen, microphone, etc.). Although not shown, the base station 304 and network entity 306 may also include a user interface.

[0085] Referring more specifically to processing system 384, in the downlink, IP packets from network entity 306 may be provided to processing system 384. Processing system 384 may implement functionality for the RRC layer, packet data convergence protocol (PDCP) layer, radio link control (RLC) layer, and media access control (MAC) layer. Processing system 384 may provide RRC layer functionality associated with system information (e.g., master information block (MIB), system information block (SIB)) broadcast, RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-RAT mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with transfer of upper layer packet data units (PDUs), error correction via automatic repeat request (ARQ), concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and re-ordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, scheduling information reporting, error correction, priority handling, and logical channel prioritization.

[0086] Transmitter 354 and receiver 352 may implement layer 1 functionality associated with various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) encoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. Transmitter 354 handles the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The decoded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to orthogonal frequency division multiplexing (OFDM) subcarriers, multiplexed with reference signals (e.g., pilots) in the time domain and / or frequency domain, and then combined together using the inverse fast Fourier transform (IFFT) to generate a physical channel carrying a time-domain OFDM symbol stream. The OFDM symbol stream is space precoded to generate multiple spatial streams. Channel estimates from the channel estimator may be used to determine the coding and modulation schemes and for spatial processing. The channel estimates may be derived from reference signals transmitted by UE 302 and / or channel state feedback. Each spatial stream may then be provided to one or more different antennas 356. Transmitter 354 may modulate an RF carrier with the respective spatial streams for transmission.

[0087] At the UE 302, the receiver 312 receives signals via its respective antenna 316. The receiver 312 recovers the information modulated onto the RF carrier and provides this information to the processing system 332. The transmitter 314 and the receiver 312 implement layer 1 functionality associated with various signal processing functions. The receiver 312 may perform spatial processing on the information to recover any spatial streams destined for the UE 302. If there are multiple spatial streams destined for the UE 302, they may be combined by the receiver 312 into a single OFDM symbol stream. The receiver 312 then uses the Fast Fourier Transform (FFT) to transform this OFDM symbol stream from the time domain to the frequency domain. The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols, as well as the reference signals, on each subcarrier are recovered and demodulated by determining the signal constellation points most likely transmitted by the base station 304. These soft decisions may be based on the channel estimates calculated by the channel estimator. These soft decisions are then decoded and deinterleaved to recover the original data and control signals transmitted by the base station 304 on the physical channels. These data and control signals are then provided to the processing system 332 that implements layer 3 and layer 2 functionality.

[0088] In the uplink, the processing system 332 provides demultiplexing between the transport channel and the logical channel, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the core network. The processing system 332 is also responsible for error detection.

[0089] Similar to the functionality described in connection with the downlink transmission by the base station 304, the processing system 332 provides RRC layer functionality associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functionality associated with header compression / decompression and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with the mapping between the logical channel and the transport channel, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via hybrid automatic repeat request (HARQ), priority handling, and logical channel prioritization.

[0090] Channel estimates derived by the channel estimator from the reference signals or feedback transmitted by the base station 304 may be used by the transmitter 314 to select appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the transmitter 314 may be provided to different antennas 316. The transmitter 314 may modulate the RF carrier with the respective spatial streams for transmission.

[0091] Uplink transmissions are processed at base station 304 in a manner similar to that described in connection with the receiver function at UE 302. Receiver 352 receives signals via its respective antenna 356. Receiver 352 recovers the information modulated onto the RF carrier and provides this information to processing system 384.

[0092] In the uplink, processing system 384 provides demultiplexing between transport channels and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from UE 302. The IP packets from processing system 384 may be provided to the core network. Processing system 384 is also responsible for error detection.

[0093] For convenience, UE 302, base station 304, and / or network entity 306 are shown in Figures 3A - 3C as including various components that may be configured according to the various examples described herein. However, it will be appreciated that the illustrated boxes may have different functionality in different designs.

[0094] The various components of UE 302, base station 304, and network entity 306 may communicate with each other respectively over data buses 334, 382, and 392. Figures 3A - 3C The components of may be implemented in various ways. In some implementations, Figures 3A - 3CThe components can be implemented in one or more circuits (e.g., such as one or more processors and / or one or more ASICs (which may include one or more processors)). Here, each circuit may use and / or incorporate at least one memory component for storing information or executable code used by the circuit to provide this functionality. For example, some or all of the functionality represented by blocks 310 to 346 can be implemented by the processor and memory components of UE 302 (e.g., by executing appropriate code and / or by appropriately configuring the processor components). Similarly, some or all of the functionality represented by blocks 350 to 388 can be implemented by the processor and memory components of base station 304 (e.g., by executing appropriate code and / or by appropriately configuring the processor components). Additionally, some or all of the functionality represented by blocks 390 to 398 can be implemented by the processor and memory components of network entity 306 (e.g., by executing appropriate code and / or by appropriately configuring the processor components). For simplicity, various operations, actions, and / or functions are described herein as being "performed by the UE", "performed by the base station", "performed by the positioning entity", etc. However, as will be appreciated, such operations, actions, and / or functions can actually be performed by specific components or combinations of components of the UE, base station, positioning entity, etc., such as processing systems 332, 384, 394, transceivers 310, 320, 350, and 360, memory components 340, 386, and 396, radar components 342, 388, and 398, etc.

[0095] Figure 4A FIG. 400 is an illustration showing an example of a DL frame structure in accordance with aspects of the present disclosure. Figure 4B FIG. 430 is an illustration showing an example of channels within a DL frame structure in accordance with aspects of the present disclosure. Other wireless communication technologies may have different frame structures and / or different channels.

[0096] LTE, and in some cases NR, utilizes OFDM on the downlink and single-carrier frequency-division multiplexing (SC-FDM) on the uplink. However, different from LTE, NR also has the option of using OFDM on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, which are also often referred to as frequency tones, frequency slots, etc. Each subcarrier can be modulated with data. Generally speaking, the modulation symbols are sent in the frequency domain for OFDM and in the time domain for SC-FDM. The interval between adjacent subcarriers can be fixed, and the total number (K) of subcarriers can depend on the system bandwidth. For example, the interval of subcarriers can be 15 kHz, and the minimum resource allocation (resource block) can be 12 subcarriers (or 180 kHz). Therefore, for system bandwidths of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), the nominal FFT sizes can be equal to 128, 256, 512, 1024, or 2048 respectively. The system bandwidth can also be divided into subbands. For example, a subband can cover 1.08 MHz (i.e., 6 resource blocks), and for system bandwidths of 1.25, 2.5, 5, 10, or 20 MHz, there can be 1, 2, 4, 8, or 16 subbands respectively.

[0097] LTE supports a single parameter set (subcarrier interval, symbol length, etc.). In contrast, NR can support multiple parameter designs. For example, subcarrier intervals of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 204 kHz or greater can be available.

[0098] Table 1 provided below lists some various parameters for different NR parameter sets.

[0099]

[0100] Table 1

[0101] In Figure 4A and 4B example, a parameter design of 15 kHz is used. Therefore, in the time domain, a frame (e.g., 10 ms) is divided into 10 equal-sized subframes, each subframe being 1 ms, and each subframe includes one time slot. In Figure 4A and 4B , time is represented horizontally (e.g., on the X-axis), where time increases from left to right, and frequency is represented vertically (e.g., on the Y-axis), where frequency increases (or decreases) from bottom to top.

[0102] A resource grid can be used to represent time slots, each time slot including one or more time-concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs)) in the frequency domain. The resource grid is further divided into a plurality of resource elements (REs). An RE can correspond to one symbol length in the time domain and one subcarrier in the frequency domain. In Figure 4A and 4B parameter design, for a normal cyclic prefix, an RB can include 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols in the time domain (for DL, OFDM symbols; for UL, SC-FDMA symbols), a total of — 84 REs. For an extended cyclic prefix, an RB can include 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

[0103] As Figure 4A explained, some REs carry DL reference (pilot) signals (DL-RSs) for channel estimation at the UE. DL-RSs can include demodulation reference signals (DMRSs) and channel state information reference signals (CSI-RSs), and their exemplary positions are marked as “R” in Figure 4A .

[0104] Figure 4B Examples of various channels within the DL subframe of an illustrative frame are explained. The physical downlink control channel (PDCCH) carries DL control information (DCI) within one or more control channel elements (CCEs), each CCE including 9 RE groups (REGs), each REG including 4 consecutive REs in the OFDM symbol. The DCI carries information about UL resource allocation (persistent and non-persistent) and a description of the DL data transmitted to the UE. Multiple (e.g., up to 8) DCIs can be configured in the PDCCH, and these DCIs can have one of multiple formats. For example, there are different DCI formats for UL scheduling, for non-MIMO DL scheduling, for MIMO DL scheduling, and for UL power control.

[0105] The Primary Synchronization Signal (PSS) is used by the UE to determine subframe / symbol timing and the physical layer identity. The Secondary Synchronization Signal (SSS) is used by the UE to determine the physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine the PCI. Based on the PCI, the UE can determine the location of the aforementioned DL-RS. The Physical Broadcast Channel (PBCH) carrying the MIB can be logically grouped with the PSS and SSS to form an SSB (also referred to as SS / PBCH). The MIB provides the number of RBs in the DL system bandwidth and the System Frame Number (SFN). The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information (such as System Information Blocks (SIBs)) not transmitted through the PBCH, and paging messages. In some cases, the DL RS explained in Figure 4A can be a positioning reference signal (PRS).

[0106] The wireless communication signal transmitted between the UE and the base station (e.g., an RF signal configured to carry OFDM symbols) can be reused for environmental sensing (also referred to as "RF sensing" or "radar"). Using the wireless communication signal for environmental sensing can be regarded as a consumer-grade radar with advanced detection capabilities that can especially enable contactless / device-free interaction with devices / systems. The wireless communication signal can be a cellular communication signal, such as an LTE or NR signal, a WLAN signal, etc. As a specific example, the wireless communication signal can be the OFDM waveform used in LTE and NR. High-frequency communication signals (such as mmW RF signals) are particularly conducive to being used as radar signals because the higher frequency at least provides more accurate range (distance) detection.

[0107] Generally speaking, there are different types of radars, especially monostatic radars and bistatic radars. Figure 5A and 5B illustrate two of these various types of radars. Specifically, Figure 5A is FIG. 500 which illustrates a monostatic radar scenario, and Figure 5B is FIG. 530 which illustrates a bistatic radar scenario. In Figure 5A , the base station 502 can be configured for full-duplex operation, and thus the transmitter (Tx) and the receiver (Rx) are co-located. For example, the transmitted radio signal 506 can be reflected off a target object (such as building 504), and the receiver on the base station 502 is configured to receive and measure the reflected beam 508. This is a typical use case of a traditional or conventional radar. In Figure 5BIn this case, the base station 505 can be configured as a transmitter (Tx), and the UE 532 can be configured as a receiver (Rx). In this example, the transmitter and the receiver are not co-located, i.e., they are separate. The base station 505 can be configured to transmit a beam, such as a full downlink RF signal 506 that can be received by the UE 532. A portion of the RF signal 506 can be reflected or refracted by the building 504, and the UE 532 can receive the reflected signal 534. This is a typical use case for RF sensing based on wireless communication (e.g., based on WiFi, based on LTE, based on NR). Note that although Figure 5B illustrates using the downlink RF signal 506 as the RF sensing signal, the uplink RF signal can also be used as the RF sensing signal. In the downlink scenario, as shown, the transmitter is the base station 505 and the receiver is the UE 532, while in the uplink scenario, the transmitter is the UE and the receiver is the base station.

[0108] Referring more specifically to Figure 5B , the base station 505 transmits an RF sensing signal (e.g., PRS) to the UE 532, but some of the RF sensing signals are reflected off a target object (such as the building 504). The UE 532 can measure the ToA of the RF signal 506 received directly from the base station, and the ToA of the reflected signal 534 reflected from the target object (e.g., the building 504).

[0109] The base station 505 can be configured to transmit a single RF signal 506 or multiple RF signals to a receiver (e.g., the UE 532). However, due to the propagation characteristics of each RF signal through the multipath channel, the UE 532 can receive multiple RF signals corresponding to each transmitted RF signal. Each path can be associated with a cluster of one or more channel taps. Generally, the time when the receiver detects the first cluster of channel taps is considered the ToA of the RF signal on the line-of-sight (LOS) path (i.e., the shortest path between the transmitter and the receiver). Subsequent clusters of channel taps are considered to have been reflected off an object between the transmitter and the receiver and have thus followed a non-line-of-sight (NLOS) path between the transmitter and the receiver. [[ID=**11**]] [[ID=**12**]]

[0110] [[ID=**13**]]Therefore, referring back to [[ID=**14**]] Figure 5B [[ID=**15**]], the RF signal 506 follows the LOS path between the base station 505 and the UE 532, and the reflected signal 534 represents the RF sensing signal that follows the NLOS path between the base station 505 and the UE 532 due to reflection off the building 504 (or another target object). The base station 505 may have transmitted multiple RF sensing signals ([[ID=**16**]] Figure 5B(not shown in the figure), some of the multiple RF sensing signals follow the LOS path, while some of the multiple RF sensing signals follow the NLOS path. Alternatively, the base station 505 may have transmitted a single RF sensing signal in a beam that is wide enough, where a portion of the RF sensing signal follows the LOS path and a portion of the RF sensing signal follows the NLOS path.

[0111] Based on the difference between the ToA of the LOS path, the ToA of the NLOS path, and the speed of light, the UE 532 can determine the distance to the building 504. Additionally, if the UE 532 is capable of receiving beamforming, the UE 532 may be able to determine the general direction to the building 504 as the direction of the reflected signal 534, which is the received RF sensing signal that follows the NLOS path. The UE 532 can then optionally report this information to the transmitting base station 505, an application server associated with the core network, an external client, a third-party application, or some other entity. Alternatively, the UE 532 can report the ToA measurement to the base station 505 or other entity, and the base station 505 can determine the distance to the target object and optionally determine the direction to the target object.

[0112] Note that if the RF sensing signal is an uplink RF signal transmitted by the UE 532 to the base station 505, the base station 505 will perform object detection based on the uplink RF signal, just as the UE 532 does based on the downlink RF signal.

[0113] Refer to Figure 5C , an example graph 550 showing the variation of the RF channel response over time at a receiver (e.g., any one of the UEs or base stations described herein) is shown. In Figure 5C 's example, the receiver receives multiple (four) channel tap clusters. Each channel tap represents a multipath that the RF signal follows between the transmitter (e.g., any one of the UEs or base stations described herein) and the receiver. That is, the channel tap represents the arrival of the RF signal on the multipath. Each channel tap cluster indicates that the corresponding multipath generally follows the same path. Different clusters may exist because the RF signal is transmitted on different transmit beams (and thus at different angles), or because of the propagation characteristics of the RF signal (e.g., due to reflections potentially following very different paths), or both.

[0114] In Figure 5CUnder the described channel, the receiver receives a first cluster of two RF signals on the channel taps at time T1, a second cluster of five RF signals on the channel taps at time T2, a third cluster of five RF signals on the channel taps at time T3, and a fourth cluster of four RF signals on the channel taps at time T4. In Figure 5C the example of Figure 5B , since the first cluster of RF signals arrives first at time T1, it is assumed to be the LOS data stream (i.e., the data stream that arrives on the LOS or shortest path), and may correspond to the Figure 5B LOS path described in Figure 5C (e.g., RF signal 506). The third cluster at time T3 consists of the strongest RF signals and may correspond to the

[0115] NLOS path described in Figure 6 (e.g., reflected signal 534). Note that although

[0116] clusters of two to five channel taps are described, it will be appreciated that these clusters may have more or fewer channel taps than the number of channel taps described. Referring to Figure 6 , an example single-target beam management use case 600 for bistatic radio frequency sensing is shown. Use case 600 includes a base station 602 (such as a 5G NR gNB) configured to transmit multiple beamformed signals along different azimuth angles and / or elevations, and a UE 610 configured to use receive beamforming to increase the signal gain based on the angle of arrival. The base station 602 may be configured to generate N different reference beams and various azimuth angles, elevations, and / or beam widths. In one example, the beams transmitted by the base station 602 may be based on SS blocks, CSI-RS, TRS, or PRS resource sets. Other sensing and tracking reference signals may also be used. The UE 610 may be configured to generate receive beams, such as a first receive beam 612, a second receive beam 614, and a third receive beam 616, using phase shifters and other software and hardware techniques. The UE 610 may also be configured to use beamforming for transmitted beams. The base station 602 may transmit a first reference signal 604 in the direction of a target object (such as building 504), and the first reference signal 604 may be reflected, and the UE 610 may use the first receive beam 612 to receive the reflected signal 606. The reflected signal 606 represents the NLOS path of the first reference signal 604 to the UE 610. The base station 602 also transmits a second reference signal 608 on a second beam. In one example, the second reference signal 608 may be quasi-co-located (QCL) with the first reference signal 604. The UE 610 uses the second receive beam 614 to receive the second reference signal 608. The second reference signal 608 is the LOS path to the UE 610.

[0116] In operation, the UE 610 may be configured to report channel responses for each of the first reference signal and the second reference signals 604, 608 to the base station 602 or another serving cell, and the base station 602 may be configured to manage transmit and receive beam pairs for object sensing. For example, the base station 602 may be configured to provide transmit and receive beam identification information to the UE 610 to track an object (such as the building 504). The beam identification information may be a transmission configuration indicator (TCI) sent in a DCI message that includes configurations (such as the QCL relationship between the transmit beam and the receive beam).

[0117] Referring Figure 7 , and further referring Figure 6 , an example multi-target use case 700 for bistatic radio frequency sensing is shown. The use case 700 extends the single-target use case 600 of Figure 6 by including a second target. By way of example and not limitation, the second target may be a second building 704. The number and nature of the targets may vary based on the environment and the radio sensing application. In the use case 700, the base station 602 transmits a third reference signal 702 that is reflected by the second building 704, and the resulting reflected signal 708 is detected by the second receive beam 614 of the UE 610. The UE 610 may report a channel response for the third reference signal 702 with an indication that the measurement was obtained using the second receive beam 614. The base station 602 is configured to manage the beam pair associated with the second target (i.e., the third reference signal 702 and the second receive beam 614). Additional targets and corresponding beam pairs may also be managed by the base station 602. The base station 602 may be configured to track one or more of the targets and may therefore provide the corresponding beam pair information as QCL / TCI for the respective targets to the UE 610.

[0118] Referring Figure 8A, an example scan phase 800 with bistatic RF sensing is shown. The base station 802 is an example of the base station 304 and is configured to transmit multiple beamformed reference signals at varying azimuth angles, elevations, and / or beam widths. The reference signals can be SS blocks, CSI-RS, TRS, PRS, or sensing scan reference signals (SSRS) configured for RF sensing applications. The UE 810 is an example of the UE 302 and can be configured to perform receive beam scans along different azimuth angles, elevations, and / or beam widths relative to the orientation of the UE 810. In operation, the base station 802 can transmit one or more of the reference signals in sequential order (i.e., beam sweep), and the UE 810 is configured to beam sweep through different receive beams. The scan phase 800 can be used to initially detect potential objects to be tracked via RF sensing. For example, the first reference signal 804 can be reflected by the first object 820a, and the first reflected reference signal 804a can be detected by the UE 810. The UE 810 can cycle through different receive beams, such as the first receive beam 812, the second receive beam 814, and the third receive beam 816. As Figure 8A depicted, the first reflected reference signal 804a can be received using the first receive beam 8l2. The UE 810 can also detect the second reference signal 805 using the LOS path with the second receive beam 814. The beam sweep on the base station 802 can generate a third reference signal 806 that is reflected on the second object 820b, and the third reflected reference signal 806a is received by the UE 810 on the third receive beam 816.

[0119] In one embodiment, the UE 810 can be configured to detect a target based on the RSRP of the received signal. For example, the UE 810 can report that the RSRP values associated with the first reference signal 804 and the third reference signal 806 are higher than a threshold. The threshold can be a fixed value or can be scaled based on the RSRP of the LOS signal (such as the second reference signal 805). The UE 810 is configured to report one or more channel measurements (e.g., RSRP, RSRQ, SINR) associated with the received reference signals to the base station 802 or other network nodes. The measurements obtained during the scan phase 800 can be used for subsequent tracking phases.

[0120] Referring to Figure 8B , and further referring to Figure 8A , an example tracking phase 850 employing bistatic RF sensing is shown. Continuing Figure 8AAs an example, the base station 802 (or another network node in the communication system 100) may determine to track one or more objects detected during the scanning phase 800. For example, the base station 802 may choose to track the first object 820a and will send beam configuration information to the UE 810 to enable the UE 810 to track the first object 820a. This beam configuration information may include reference signal information for the UE 810 and receive beam configuration information. The base station 802 may use a sensing tracking reference signal (STRS) based on the first reference signal 804 to track or refine measurements associated with the first object. In one example, the STRS may be quasi-co-located with the corresponding SSRS (i.e., the first reference signal 804). The SS block, CSI-RS, TRS, and PRS may be used as the STRS. Other reference signals may also be developed and used as the STRS. The beam configuration information sent to the UE 810 may be sent via RRC, media access control control element (MAC-CE), DCI, or other signaling protocols. Upon receiving the beam configuration information, the UE 810 may detect the first object 820a, for example, using the first receive beam 812 with the STRS.

[0121] The base station 802 may be configured to track multiple targets based on the number of reference signals that the base station 802 can generate. In one embodiment, the base station 802 may be configured to track one object for each reference signal. For example, the base station 802 may track the second object 820b by generating a second STRS based on the third reference signal 806. The beam configuration information sent to the UE 810 may include the beam parameters of the second STRS and the corresponding receive beam information (e.g., the third receive beam 816) provided by the UE 810 during the scanning phase 800. Thus, the UE 810 may be configured to track both the first object 820a and the second object 820b. Additional objects may be tracked up to the number of reference signals generated by the base station 802.

[0122] Figure 9 is a simplified diagram showing the basic operation of a bistatic radar system 900. A transmitter 902 and a receiver 904 are used to send and receive radar signals to sense a target 906. Although a bistatic radar example is shown, the same operating principle may be applied to a multistatic radar that utilizes more than two transmitters / receivers. For example, a multistatic radar may utilize one transmitter and two receivers. In another example, a multistatic radar may utilize two transmitters and one receiver. A greater number of transmitters and / or receivers is also possible.

[0123] In a bistatic radar system 900, a transmitter 902 sends a transmit signal 908, which travels through a distance RT to reach a target 906. The transmit signal 908 reflects from the target 906 and becomes an echo signal 910, which travels through a distance RR to reach a receiver 904. The main function served by the bistatic radar system 900 is to sense the range or distance RR from the target 906 to the receiver 904. The system determines the range RR mainly by sensing the amount of time taken for the transmit signal 908 and the echo signal 910 to travel through a total distance R sum which is the sum of RT and RR: sum R

[0124] = R sum + R T (Equation 1) R

[0125] The total distance R sum defines an ellipsoid (also known as an isosrange contour) with foci located at the positions of the transmitter 902 and the receiver 904, respectively. This ellipsoid represents all possible positions of the target 906 for a given total distance R sum The radar system 900 is capable of measuring the distance R sum sum . For example, if perfect timing synchronization between the transmitter 902 and the receiver 904 can be assumed, it would be easy to simply measure the time duration T sum between the time when the transmitter 902 sends the transmit signal 908 and the time when the receiver 904 receives the echo signal 910. Multiplying the time duration T sum by the speed of the signal through free space (e.g., approximately c = 3 * 908 m / s) will yield R sum . Thus, the ellipsoid of all possible positions of the target 906 can be obtained by measuring the "time of flight" T sum of the bistatic radar signal.

[0126] According to some embodiments, the distance R sum can be measured without having tight time synchronization between the transmitter 902 and the receiver 904. In one embodiment, a line-of-sight (LOS) signal 912 can be sent from the transmitter 902 to the receiver 904. That is, while the transmitter 902 sends the transmit signal 908 towards the target 906, the transmitter 902 can also send the LOS signal 912 towards the receiver 904. According to a specific embodiment, the transmit signal 908 can correspond to the main lobe of the transmit antenna beam pattern emitted from the transmitter 902, while the LOS signal 912 corresponds to the side lobe of the same transmit antenna beam pattern emitted from the transmitter 902.

[0127] The receiver 904 receives both the echo signal 910 and the LOS signal 912, and can use the reception timing of these two signals to measure the total distance Rsum using the following expression:

[0128]

[0129] Here, TRx_echo is the reception time of the echo signal 910. TRxLOS is the reception time of the LOS signal 912. As mentioned, c = 3 * 10^8 m / s is the speed of the signal through free space. L is the distance between the transmitter 902 and the receiver 904. Once Rsum is obtained, it can be used to calculate the target range RR (i.e., the distance between the target 906 and the receiver 904) using the following formula:

[0130]

[0131] The bistatic radar system 900 can also be used to determine the angle of arrival (AoA) θ at which the echo signal 910 is received by the receiver 904 R . This can be done in various ways. One way is to estimate θ by using an antenna array at the receiver 904 R . The antenna array (which includes multiple antenna elements) can operate as a programmable directional antenna capable of sensing the angle at which the signal is received. Thus, the receiver 904 can use the antenna array to sense the angle of arrival of the echo signal 910. Another way for estimating θ R involves multilateration. Multilateration refers to determining the intersection of two or more curves or surfaces representing possible positions of a target. For example, Figure 9 the bistatic radar system 900 shown in can define a first ellipsoid representing the possible positions of the target 906, as previously described. A second bistatic radar system with differently located transmitters and / or receivers can define a different second ellipsoid also representing the possible positions of the target 906. The intersection of the first ellipsoid and the second ellipsoid can reduce the possible positions of the target 906. In three-dimensional space, generally four such ellipsoids will be required to reduce the possible positions to a single point, thereby identifying the position of the target 906. In two-dimensional space (e.g., assuming that all transmitters, receivers, and targets are restricted to ground-based objects), generally three such ellipsoids (for two-dimensional space, the ellipsoids degenerate into elliptical curves) will be required to reduce the possible positions to a single point, thereby identifying the position of the target 906. Multistatic radar systems can also be used instead of multiple bistatic radar systems to achieve multilateration in a similar manner.

[0132] In addition, the bistatic radar system 900 can also be used to determine the Doppler frequency associated with the target 906. From the perspective of the receiver 904, this Doppler frequency represents the relative velocity of the target 906 - i.e., the velocity at which the target 906 approaches / leaves the receiver 904. For a stationary transmitter 902 and a stationary receiver 904, the Doppler frequency of the target 906 can be calculated as:

[0133]

[0134] where f D is the Doppler frequency, v is the velocity of the target 906 relative to the fixed reference frame defined by the stationary transmitter 902 and receiver 904. β is the angle formed between the transmitted signal 908 and the echo signal 910 at the target 906. δ is the angle between the velocity vector ν and the central ray (half-angle) defined within the angle β.

[0135] In Figure 9 , the fixed reference frame is defined with respect to the stationary transmitter 902 and the stationary receiver 904. Specifically, a baseline of length L can be drawn between the transmitter 902 and the receiver 904. This baseline can extend out from the transmitter 902 and the receiver 904. One or more normal lines perpendicular to the baseline can be drawn. The transmit angle θ T can be defined relative to the normal line drawn from the position of the transmit angle 902. The receive angle θ R , which was referred to above as the angle of arrival, can be defined relative to the normal line drawn from the position of the receiver 904.

[0136] As previously mentioned, the bistatic radar system 900 can be operated to sense a target in two-dimensional space or three-dimensional space. In the case of three-dimensional space, additional degrees of freedom are introduced. However, the same basic principles apply and similar calculations can be performed.

[0137] Figure 10 Illustrates the implementation of the bistatic radar system 900 in a wireless communication system according to an embodiment of the present disclosure. The wireless communication system can include as Figure 10The wireless communication system 1000 shown in []. The wireless communication system 1000 may include a plurality of transmit-receive points (TRPs), which together with other devices provide signal transmission and / or reception. Examples of TRPs within the wireless communication system 1000 include base stations 1002 and 1004, which are used to provide wireless communication for user equipment (UE) (such as nearby vehicles, wireless phones, wearable devices, personal access points, and a large number of other types of user equipment) that require wireless data communication. For example, base stations 1002 and 1004 may be configured to support data communication with the UE device by transmitting / receiving data symbols to / from the UE device. Resources within the wireless communication system 1000 (such as base stations 1002 and 1004) can thus be used to serve "dual tasks" to not only support wireless communication operations but also support bistatic and / or multistatic radar operations. The wireless communication system 900 may be a cellular communication system.

[0138] For example, base station 1002 and base station 1004 may be used as Figure 9 the transmitter 902 and the receiver 904 of the bistatic radar system 900 shown in []. Base station 1002 may transmit a transmit signal 1008, which is reflected from the target 906 and becomes an echo signal 1010 received by base station 1004. Base station 1004 may also receive a line-of-sight (LOS) signal 1012 from base station 1002.

[0139] By receiving both the LOS signal 1012 and the echo signal 1010, the RX base station 1004 can measure the value of the time difference associated with the time difference between the reception times TRx_echo and TRxLOS associated with the received LOS signal 1012 and echo signal 1010, respectively. For example, the RX base station 1004 may cross-correlate the received LOS signal 1012 with the received echo signal 1010 (such as by mixing the two signals in analog or digital form) to obtain a value representing the time difference (TRx_echo - TRxLOS). This time difference can be used to obtain the total distance Rsum. The total distance Rsum can then be used to define an ellipsoid, which together with other information can be used to obtain the target range RR, the angle of arrival (AoA) θ Figure 9 associated with the target 1006 and / or the Doppler frequency using one or more of the techniques discussed previously with respect to R and / or Doppler frequency.

[0140] Here, the target 906 can be (but is not necessarily) a UE being supported by the wireless communication system 1000. In some instances, the target 906 can be a UE configured to transmit and receive wireless signals carrying voice, text, and / or wireless data using the base stations of the wireless communication system 1000. In other instances, the target 906 may be just a remote object that is within the bistatic radar range of base station 1002 and base station 1004 but is otherwise not related to the wireless communication functions of the system 1000.

[0141] In Figure 10 the bistatic example shown, the transmitter is referred to as TX base station 1002, and the receiver is referred to as RX base station 1004. More generally, TX base station 1002 can be referred to as TX TRP, and RX base station 1004 can be referred to as RX TRP. Here, "TX" and "RX" merely refer to the fact that base station 1002 is used to transmit the radar transmit signal 1008 while base station 1004 is used to receive the radar echo signal 1010. The terms "TX" and "RX" in this context do not restrict the operation of base stations 1002 and 1004 in serving other functions, e.g., serving as a transmitter and / or receiver in other bistatic or multistatic radar operations (beyond Figure 9 the operations illustrated) or serving as base stations that transmit and receive data communications in the normal operation of the wireless communication system 1000. Although Figure 10 illustrates a simple bistatic radar system, a multistatic radar system can also be implemented in a similar manner within the wireless communication system. Moreover, although Figure 10 illustrates a simple example in two-dimensional space, the same operations can be extended to three-dimensional space.

[0142] Implementing a bistatic or multistatic radar system within a wireless communication system according to various embodiments of the present disclosure can provide numerous benefits. One particular benefit is the flexible utilization of the bandwidth allocated for wireless communication. An example of a wireless communication system 1000 is a cellular communication system. For example, according to one embodiment, the wireless communication system 1000 may comply with the "5G" standard introduced in Release 15 of the 3rd Generation Partnership Project (3GPP) specifications. The increasing bandwidth allocated for current and future wireless communication systems, including 5G and beyond 5G, can be utilized to transmit bistatic and multistatic radar signals. Thus, radio frequency (RF) sensing (e.g., radar) can be achieved by leveraging the available wireless RF spectrum resources. For example, one or more of the transmit signal 1008, the echo signal 1010, and / or the LOS signal 1012 may occupy the bandwidth within a portion of the radio frequency (RF) spectrum allocated to the wireless communication system 1000 for data communication. Another example of a wireless communication system 1000 is a Long Term Evolution (LTE) wireless communication system. Other examples of the wireless communication system 1000 include wireless local area network (WLAN), wireless wide area network (WWAN), small cell-based wireless communication systems, millimeter wave (mmWave)-based communication systems, and systems for other types of communication including TRP.

[0143] In addition, the inherent benefits of bistatic and multistatic radar systems can be realized through the existing widespread network of transmitters and receivers in the form of wireless base stations that are appropriately located. Compared to a monostatic radar system, a bistatic or multistatic radar system reduces self-interference by having physically separated transmitter equipment and receiver equipment. Wireless base stations (such as Figure 10 the base stations 1002 and 1004 shown in

[0144] already exist and cover a vast geographical area where users, vehicles, and other objects of interest are likely to be present. Such wireless base stations are sufficiently dispersed and, as a result, provide the opportunity to select appropriately located base stations to be used as transmitters and receivers for bistatic and multistatic radar operations.

[0145] According to certain embodiments, a "radar controller" can be implemented to support the operation of one or more bistatic and / or multistatic radar systems implemented within a wireless communication system. Here, the "radar controller" can be implemented as a combination of hardware and / or software resources residing within the wireless communication network. Thus, the radar controller can be defined as a functional block, facility, or node that is used to, for example, configure and / or control the parameters upon which the TX and RX base stations involved in bistatic and / or multistatic radar operations depend.

[0146] Figure 11 is a block diagram of a wireless communication system 1100 that may include a radar controller according to an embodiment of the present disclosure. The wireless communication system 1100 includes a core network (CN) 1102, a radio access network (RAN) 1104, and one or more user equipments (UE) 1106. In one embodiment, the radar controller 1108 may be implemented within the CN 1102. The CN 1102 provides connectivity to the Internet and application services to the system 1100. The CN 1102 may be implemented with various computing resources, which may include a memory and one or more processors that execute an operating system and execute applications including programmed instructions. In a specific embodiment, the radar controller 1108 may be implemented within the computing resources of the CN 1102.

[0147] In another embodiment, the radar controller 1110 may be implemented within the RAN 1104. For example, the RAN 1104 may include base stations 1002 - 1004. Each of the base stations 1002 - 1004 may include transmitter and receiver hardware, such as antennas, antenna elements, cables, physical tower structures, modems, encoders / decoders, networking equipment, computing resources, and other components. The computing resources associated with each base station may include a memory and one or more processors that execute an operating system and execute applications including programmed instructions. In a specific embodiment, the radar controller 1110 may be implemented within the computing resources of one or more of the base stations 1002 - 1004.

[0148] The radar controller 1108 (or 1110) may be implemented elsewhere in the radio access network (RAN), the core network (CN) 1102, or in a wireless communication system (e.g., a cellular communication system 1100). The radar controller 1108 (or 1110) does not have to be a dedicated server. For example, the radar controller 1108 (or 1110) may be a general - purpose server, a positioning server, an assisted - driving server, a tracker server, or another server that provides different functionality. Additionally, the radar controller 1108 (or 1110) may (but does not have to) be operated or owned by a network operator. The radar controller 1108 (or 1110) may be a network - independent server (e.g., a third - party server).

[0149] Regardless of where it is implemented, the radar controller 1108 (or 1110) may be communicatively coupled to a transmit - receive point (TRP) within the RAN 1104, e.g., base stations 1002 and 1004, via one or more interfaces. The one or more interfaces may include point - to - point interfaces. An example of such a point - to - point interface is an interface that implements the Internet Protocol (IP) communication protocol over a wired network (e.g., a “backhaul” network).

[0150] In some embodiments, the wireless communication system 1100 may comply with the "5G" standard. In such cases, the CN 1102 may be a 5G core node (5G CN), the RAN 1104 may be a 3GPP next-generation radio access network (NG RAN), and each of the base stations 1002 and 1004 may be a "gNodeB" or "gNB".

[0151] Figure 12 An example of a radar configuration parameter list 1200 provided by the radar controller 1108 (or 1110) to the TX base station 1002 and the RX base station 1004 for a bistatic or multistatic radar measurement session in accordance with an embodiment of the present disclosure is shown. Here, the radar measurement session may include one or more radar signal transmissions / receptions associated with obtaining range, Doppler, or angle estimates of a target. Examples of such radar measurement sessions may be a "chirp" sequence of a frequency-modulated continuous-wave (FMCW) radar signal transmitted by the TX base station and a corresponding response "chirp" sequence of the FMCW radar signal received by the RX base station.

[0152] As Figure 12 shown, the radar configuration parameter list 1200 may include several entries, which may include values of parameters such as a radar session ID, a TX base station ID, an RX base station ID, TX / RX timing parameters, Doppler parameters, a radar waveform type, a radar signal center frequency, a radar signal bandwidth (BW), a radar period, a radar repetition factor, and a linear frequency modulation (LFM) frequency slope. These parameters are given for illustrative purposes, and the entries in the configuration parameter list of any given radar system implemented within a wireless communication system may differ from Figure 12 the example shown.

[0153] Referring again to Figure 12 , the radar session ID identifies a specific radar measurement session. The TX base station ID identifies a specific base station in the wireless communication system as the transmitter of the radar transmit signal. The RX base station ID identifies a specific base station in the wireless communication system as the receiver of the radar echo signal reflected from the target. ​ The example shown in

[0154] "0" = FMCW

[0155] "1" = Positioning Reference Signal (PRS)

[0156] "2" = Single-Sideband Modulation (SSB)

[0157] "3" = Tracking Reference Signal (TRS)

[0158] "4" = Demodulation Reference Signal (DMRS)

[0159] "5" = Channel State Information Reference Signal (CSI-RS).

[0160] A variety of waveforms can be selected. Some waveforms (such as FMCW) can be specifically associated with radar system operations. However, other waveforms (such as PRS, SSB, TRS, DMRS, and CSI-RS) can be associated with wireless system operations. Thus, according to various embodiments of the present disclosure, waveforms already present in a wireless communication system can be opportunistically used as radar signal waveforms.

[0161] The radar controller 1108 (or 1110) can specify one or more parameters associated with a selected reference signal. The reference signal can be defined by selecting a waveform type (such as those listed above). Additionally, the reference signal can be defined by specifying one or more other attributes. For example, the radar configuration parameter list 1200 or other configuration parameters can be used to specify such attributes. Referring back to ​ , the radar signal center frequency specifies the center frequency of the radar transmitted signal. By way of example only, ​ a center frequency of 79 GHz is shown in [[. Thus, the center frequency in this example falls within the spectrum allocated for the wireless communication system 1000 (e.g., within the 5G spectrum (which ranges from 300 MHz to 100 GHz)). The center frequency of the radar echo signal may exhibit a Doppler shift away from the radar center frequency. Such Doppler shifts are discussed in more detail in a later section. The radar signal bandwidth (BW) specifies the bandwidth of the transmitted radar signal. By way of example only, ​ a bandwidth of 2 GHz is shown in [[. It is expected that the radar echo signal has the same bandwidth. The radar repetition factor specifies the number of times the radar waveform can repeat within a specified radar session (e.g., in radar session 12345678). In this example, the waveform repeats 10 times. The LFM frequency slope specifies the slope or rate of change of the frequency of a linear frequency modulation (LFM) radar waveform. Here, the slope is 100 MHz / microsecond. One type of LFM waveform is the previously mentioned FMCW waveform.

[0162] In summary, ​The radar session specified in can utilize an FMCW waveform that forms a "chirp", which repeats 10 times with a total duration of 200 microseconds. Each chirp can have a duration of 20 microseconds, during which the center frequency of the continuous wave (CW) signal linearly increases from 79 GHz to 81 GHz at a rate of 100 MHz / microsecond. Even though the CW signal has a very narrow bandwidth, the effective bandwidth of the entire sweep of the FMCW signal will be 2 GHz. These or other characteristics of the reference signal (in this case, the FMCW reference signal) can be specified as one or more parameters provided by the radar controller 1108 (or 1110).

[0163] Embodiments of the present disclosure can utilize the wireless communication system 1000 to estimate certain physical properties in a radar system. For example, the distance L between the TX base station 1002 and the RX base station 1004 is an important figure that may be useful in the calculation of the target range RR and other values. The resources available within the wireless communication system 1000 can provide different ways to determine L. One possibility is to use the known locations of the TX base station 1002 and the RX base station 1004. Such location information can be obtained from the almanac of the collected physical descriptions available for all base stations within the wireless communication system 1000. Another possibility is to use GNSS (e.g., GPS) reports from the base stations (such as the TX base station 1002 and the RX base station 1004). Generally speaking, GNSS reports include the locations of the base stations. Using the accurate longitude and latitude information available for the base station locations, the distance L between the TX base station 1002 and the RX base station 1004 can be calculated. Yet another possibility is to use inter-base-station positioning signals to obtain the position lock of the TX base station 1002 and the RX base station 1004. For example, positioning signals such as positioning reference signals (PRS) can be transmitted and received between the base stations according to positioning techniques suitable for the new radio / 5G standard. Such inter-base-station positioning signals can be used to determine the position lock of the TX base station 1002 and the RX base station 1004, and the distance L between them can be determined therefrom.

[0164] ​ An example of the TX / RX timing sublist 1300 according to embodiments of the present disclosure is shown. In one specific embodiment, the TX / RX timing sublist 1300 can simply be incorporated as an additional entry in the radar configuration parameter list 1200. In another specific embodiment, the TX / RX timing sublist 1300 can be a separate but linked sublist.

[0165] The timing parameters specified in the TX / RX timing sublist 1300 depend on a certain degree of timing synchronization between the TX base station 1002 and the RX base station 1004. For numerous reasons, such TX / RX timing synchronization is important. If the RX base station 1004 happens to start "listening" at the right time (i.e., when the first expected signal (which can be the LOS signal 1012 or the echo signal 1010) arrives (or just shortly before such arrival)), the performance of the radar system can be greatly improved. If the RX base station 1004 starts listening too early, the system will turn on equipment such as intermediate frequency (IF) receiving hardware prematurely, thus wasting power and computing resources and increasing the false alarm probability of the radar system. If the RX base station 1004 starts listening too late, the system may miss receiving the LOS signal 1012 or the echo signal 1010. If a certain degree of timing synchronization can be achieved between the TX base station 1002 and the RX base station 1004, then, knowing when the transmit signal 1008 is sent from the TX base station 1002, calculations can be made to predict the arrival time of the LOS signal 1012 or the echo signal 1010 at the RX base station 1004 (with a certain degree of acceptable uncertainty). In this way, the RX base station 1004 can be controlled to start "listening" at the right time, so as to reduce unnecessary waste of power and computing resources and minimize false alarms, while ensuring that the LOS signal 1012 and the echo signal 1010 are not missed.

[0166] Aspects of the present disclosure advantageously utilize the wireless communication system 1000 to meet such radar TX / RX timing synchronization requirements. For example, the wireless communication system 1000 may include a 5G system (e.g., the system 1100), which ensures that the timing synchronization error between any two base stations does not exceed a certain amount of time. By way of example only, the 5G system may utilize orthogonal frequency division multiplexing (OFDM) signals for data communication and may ensure that the timing synchronization error between any two base stations does not exceed the duration of the cyclic prefix (CP) of the OFDM signal. The CP is a guard band in time that separates consecutive data symbols and provides protection against inter-symbol interference (ISI). For a 60 kHz subcarrier channel, the CP duration can be, for example, 1.69 microseconds. Thus, in this case, the wireless communication system 1000 can ensure that the timing error between any two base stations will not exceed 1.69 microseconds. With such timing synchronization guarantee, the radar controller 1108 (or 1110) can be able to more effectively control the timing regarding when the TX base station 1002 sends the transmit signal 1008 and when the RX base station 204 starts listening for the LOS signal 1012 and the echo signal 1010.

[0167] Referring back to ​TX / RX timing sub-list 1300 may include the radar session ID (discussed previously), TX transmission time, expected reception time, and expected reception time uncertainty. Radar controller 1108 (or 1110) may provide all or relevant portions of TX / RX timing sub-list 1300 to TX base station 1002 and RX base station 1004. For example, radar controller 1108 (or 1110) may provide TX base station 1002 with a TX transmission time, which in this example is specified as 20,000.00 microseconds. In response, TX base station 1002 begins transmitting transmit signal 1008 at time 20,000.00 microseconds. By way of example only, the value "20,000.00 microseconds" may correspond to the time elapsed since the last "tick" of a periodic reference event / signal used to synchronize timing across entities within wireless communication network 1000 (e.g., all base stations and other equipment).

[0168] Radar controller 1108 (or 1110) may also provide RX base station 1002 with an expected reception time, which in this example is specified as 20133.33 microseconds. Radar controller 1108 (or 1110) may be able to calculate the expected reception time in different ways. In one embodiment, the expected reception time may be estimated by assuming that LOS signal 1012 is likely to arrive at the RX base station before return signal 1010 (which is a valid assumption in many cases). Given this assumption, the expected reception time may be estimated as the TX transmission time plus the amount of time it is expected to take for LOS signal 1012 to traverse distance L:

[0169] Expected Receive Time = L / c + TX Transmission Time (Equation 5)

[0170] Radar controller 1108 (or 1110) may also provide an expected reception time uncertainty, which in this example is specified as a pair of values: [upper bound, lower bound]. The lower bound may simply be the negative of the network synchronization error. By way of example only, the network synchronization error may be 1.69 microseconds. The upper bound may include two components. The first component of the upper bound may correspond to the signal propagation time associated with the maximum possible distance at which a detectable target may be located. In one embodiment, such a maximum distance, L_Max, may be specified as part of the link budget. Thus, the first component of the upper bound may be expressed as L_Max / c=L / c. The second component of the upper bound may simply be the positive of the network synchronization error, which in this example is specified as 1.69 microseconds. Accordingly, the expected reception time uncertainty may be expressed as:

[0171] Expected Receive Time Uncertainty

[0172] = [lower bound, upper bound]

[0173] = [-network syn uncertainty, L_max / c - L / c + network syn error] (Equation 6)

[0174] There may also be flexibility in the way these and other configuration parameters are specified and communicated. For example, to specify the upper bound of the expected receive time uncertainty, it may be sufficient for the radar controller 1108 (or 1110) to simply send the value "L_max / c + network syn error" to the RX base station 1004 (especially if the term L / c is locally known at the RX base station 1004).

[0175] In response, the RX base station 1004 may start "listening" (i.e., start sensing the LOS signal 1012 and the echo signal 1010) within the time window specified by the following equation:

[0176] Expected Receive Time + Expected Receive Time Uncertainty

[0177] = Expected Receive Time + [lower bound, upper bound]

[0178] = [Lc + TX Transmission Time - network syn uncertainty,

[0179] L_max / c + TX Transmission Time + network syn error] (Equation 7)

[0180] The TX / RX timing parameters for a bistatic radar session, which involves a TX base station and an RX base station, were explained above. In practice, many such bistatic radar sessions (and multistatic radar sessions) can be specified in a similar manner. For each unique path L (i.e., a unique pair of a TX station and an RX station), the radar controller 1108 (or 1110) can specify a different set of TX / RX timing parameters. In a simple multistatic scenario with one transmitter and multiple receivers, the unique pairs can share a common TX base station but have different RX base stations. In such cases, a TX transmission time and multiple sets of expected reception times and expected reception time uncertainties can be specified.

[0181] ​ An example of a Doppler sublist 1400 according to embodiments of the present disclosure is shown. In one specific embodiment, the Doppler sublist 1400 can simply be incorporated as additional entries in the radar configuration parameter list 1200. In another specific embodiment, the Doppler sublist 1400 can be a separate but linked sublist.

[0182] The Doppler sublist 1400 is mainly used to estimate the Doppler shift and Doppler spread for the benefit of the RX base station 1004. As ​ shown, the Doppler sublist 1400 can include the radar session ID (previously discussed), the expected Doppler shift value, and the expected Doppler spread value. The radar controller 1108 (or 1110) typically provides these frequency-domain parameters to improve the performance of the RX base station 1004. The target 906 may be moving rapidly, which can introduce a large Doppler shift and / or Doppler spread. By providing the Doppler sublist 1400, the radar controller 1108 (or 1110) can dynamically configure the "expected Doppler shift" and "expected Doppler spread" assumed by the RX base station 1004.

[0183] For example, in the acquisition mode, the Doppler sublist 1400 can specify larger values for the expected Doppler shift and the expected Doppler spread. This allows the RX base station 1004 to receive signals over a wider Doppler frequency range, thereby improving the detection rate. By way of example only, ​ shows that the expected Doppler shift value is specified as 80,000 m / s and the expected Doppler spread is specified as 10,000 m / s.

[0184] In contrast, in the tracking mode, the Doppler sublist 1400 can specify finer and narrower values. These values can be based on the measurement history that has been carried out. A finer set of Doppler parameters can focus on a specific target. An instance of the Doppler sublist 1400 can be specified for each target being tracked. Thus, a particular RX base station 1004 can receive multiple Doppler sublists 1400 corresponding to multiple targets.

[0185] ​ 、 13 The specific parameters shown in 13 and 14 are described for illustrative purposes. Depending on the implementation, there may be deletion or addition of certain parameters, and different parameters may be specified simultaneously. Nevertheless, according to embodiments of the present disclosure, the configuration parameters for the (one or more) TX base stations and / or the (one or more) RX base stations in a bistatic or multistatic radar system can be provided by a radar controller within an entity (such as a core network (CN) or a radio access network (RAN)) located in a wireless communication network.

[0186] The time interval between the reception of the LOS signal transmitted by the Tx and the reception of the target echo can be used to measure the distance and R sum . Therefore, small-scale synchronization errors between the Tx / Rx do not introduce estimation errors. In a classical radar system, the same / shared transmitted radar signal propagates through the channel. Subsequently, the Rx estimates the ToA difference between the LOS path and the echo path.

[0187] In some cases, for various reasons, it is not optimal to use the same radar reference signal to estimate the ToA in both the LOS and the target echo paths. First, a single wide-angle beam can be applied to the radar Tx waveform, which reduces the coverage of the system (e.g., a more focused beam can provide more coverage, but may not be able to travel along both the LOS path and the echo path). Second, digital beamforming can implement two concurrent beams, i.e., one for the LOS direction and one for the transmitter-target direction. However, this increases the number of Tx antennas at the gNB for concurrent transmission along the two paths (two beams), doubling the antenna cost. Third, for millimeter-wave systems using analog beamforming, it is also possible to maintain two concurrent beams. However, this requires at least two antenna panels for each sector (i.e., one for the LOS beam and one for the transmitter-target direction), doubling the antenna panel cost.

[0188] Accordingly, one or more aspects of the present disclosure relate to a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station. In some designs, the corresponding radar signals can be time-offset and transmitted in a time-division multiplexing (TDM) manner using the same hardware (e.g., an antenna or an antenna panel). Such aspects can provide various technical advantages, such as cost savings on the transmitter side, increased tracking coverage via the use of narrower (one or more) beams, and so on.

[0189] ​ An exemplary communication process 1500 in accordance with aspects of the present disclosure is illustrated. In one aspect, process 1500 may be performed by a radar controller, which, as mentioned above, may be integrated with a RAN component (such as BS 304), a core network component, or an external server (such as network entity 306). In some designs, the radar controller may be integrated with the first or second base station as described above, in which case any data exchange between the radar controller and the corresponding base station will correspond to an internal data transfer rather than communicating (the) signals across the network.

[0190] At 1510, a radar controller (e.g., processing system 380 or 394, radar component 388 or 389, etc.) determines a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station. For example, in the case of TDM operation, the corresponding radar signals may be offset from each other by a number of symbols in the radar time slot format, the number being based on the amount of time required for the first base station to perform RF switching for the corresponding TDM transmission. In some designs, the first link corresponds to a LOS link from the first base station to the second base station, and the at least one second link corresponds to at least one NLOS link from the first base station to the second base station. In some designs, the reference radar signal is transmitted on the LOS link via a default beam (e.g., an ideal beam may be identified earlier and subsequently set as the default beam), and the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined set of beams (e.g., due to target mobility).

[0191] At 1520, the radar controller (e.g., data bus 382, (the) network interface 380 or 390, etc.) transmits an indication of the radar time slot format to the first base station and the second base station. In some designs, the reference radar signal may have a much longer periodicity than the target radar signal (e.g., because the Tx gNB and the Rx gNB have static positions such that, apart from clock drift, the propagation delay between the Tx gNB and the Rx gNB is substantially constant). In such a case, the radar time slot format described with respect to 1510 - 1520 is used for the occasion where the reference radar signal is used in combination with (the) target radar signals, while other time slots may include only (the) target radar signals and thus do not use the radar time slot format described with respect to 1510 - 1520.

[0192] ​Exemplary communication process 1600 in accordance with aspects of the present disclosure is explained. In one aspect, process 1600 may be performed by a first base station (such as BS 304). For example, the first base station described with respect to ​ may correspond to the first base station described above with respect to ​ In some designs, the radar controller may be integrated with the first base station as described above, in which case any data exchange between the radar controller and the first base station will correspond to an internal data transfer rather than communicating (a) signal(s) across the network.

[0193] ​ At 1610, the first base station (e.g., network interface 380, data bus 382, etc.) receives a radar time slot format from the radar controller that configures the transmission of a reference radar signal on a first symbol via a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station. For example, the radar time slot format may be configured as described in 1510 with respect to ​

[0194] For example, at 1620, the first base station (e.g., transmitter 354 or 364, etc.) transmits the reference radar signal on the first symbol via the first link from the first base station to the second base station. In some designs, the reference radar signal is transmitted on the LOS link via a default beam (e.g., an ideal beam may be identified earlier and subsequently set as the default beam).

[0195] At 1630, the first base station (e.g., transmitter 354 or 364, etc.) transmits the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station. In some designs, the at least one target radar signal is transmitted on at least one NLOS link via a dynamically determined beam set (e.g., due to target mobility). In some designs, the at least one target radar signal may include multiple target radar signals targeting the same or different targets. In the case of different targets, R may be determined for each target relative to the same reference radar signal sum .

[0196] ​ Exemplary communication process 1700 in accordance with aspects of the present disclosure is explained. In one aspect, process 1700 may be performed by a second base station (such as BS 304). For example, the second base station described with respect to ​ may correspond to the second base station described above with respect to ​The described second base station. In some designs, the radar controller may be integrated with the second base station as described above, in which case any data exchange between the radar controller and the second base station will correspond to internal data transfer rather than communicating signals across a network.

[0197] At 1710, the second base station (e.g., network interfaces 380, data bus 382, etc.) receives a radar time slot format from the radar controller that configures the transmission of a reference radar signal on a first symbol over a first link from the first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station. For example, the radar time slot format may be configured as described in 1510 above with respect to ​ .

[0198] At 1720, the second base station (e.g., receivers 352 or 362, etc.) receives the reference radar signal on the first symbol over the first link from the first base station to the second base station. In some designs, the reference radar signal is received on the LOS link via a default beam (e.g., an ideal beam may be identified earlier and subsequently set as the default beam).

[0199] At 1730, the second base station (e.g., receivers 352 or 362, etc.) receives the at least one target radar signal on the at least one second symbol over the at least one second link from the first base station to the second base station. In some designs, the at least one target radar signal is received on at least one NLOS link via a dynamically determined set of beams (e.g., due to target mobility). In some designs, the at least one target radar signal may include multiple target radar signals targeting the same or different targets. In the case of different targets, R may be determined for each target relative to the same reference radar signal. sum .

[0200] Referring to ​ , in some designs, a time slot - level radar time slot format may be defined, where different radar signals have different transmission properties (e.g., beam, duration, etc.), although sharing the same time slot. In other designs, a symbol - level radar time slot format may be defined, where different radar signals have different transmission properties (e.g., beam, duration, etc.), although sharing the same symbol or group of symbols. Thus, the radar time slot format may be associated with scheduling at different granularities with respect to the corresponding radar signals within the corresponding time slot.

[0201] Referring to ​, in some designs, the transmission properties of the reference radar signal can be different from those of the target reference signal(s). For example, the duration of an instance of the reference radar signal can be less than the duration of an instance of each target radar signal (e.g., the path loss along the LOS path is smaller, so fewer or zero repetitions of the reference radar signal may be required along the LOS path).

[0202] Refer to ​ , in some designs, the radar time slot format can explicitly specify the first symbol for the reference radar signal. For example, the radar time slot format can specify which symbol is used for reference radar waveform transmission. In another example, the radar time slot format can configure the reference radar signal before the target radar signal(s), with a corresponding time difference "increment" between the respective radar signals. In such a case, at least one second symbol can be specified via at least one offset relative to the first symbol.

[0203] Refer to ​ , in some designs, the radar time slot format can explicitly designate at least one target radar signal as being associated with the reference radar signal. Alternatively, at least one target radar signal can be implicitly associated with the reference radar signal. For example, any target radar signal can be implicitly associated with the most recent reference radar signal before the corresponding target radar signal (or in other words, before the next indicated reference radar signal that has not yet arrived).

[0204] Refer to ​ , as described above, the radar controller can signal the "expected reception time" and "expected reception time uncertainty" to the second base station to guide its time window for radar waveform reception. For TDM beam operation, in some designs, the radar controller may only need to signal the "expected reception time" and "expected reception time uncertainty" regarding the radar reference signal (i.e., rather than the "expected reception time" and "expected reception time uncertainty" for the target radar signal(s)). In such a case, the Rx time of the target radar waveform can be derived based on the "expected reception time" and "expected reception time uncertainty" regarding the radar reference signal and the radar time slot format. The Rx gNB can be guided to receive the target radar signal(s) within the time window "expected reception time + expected reception time uncertainty", e.g.:

[0205] [L / c + T1 - network syn error (network synchronization error), L_max / c + T1 + delta_max (increment_max) + network syn error]

[0206] Expression 1

[0207] Where T1 is the transmission time of the reference radar signal, L / c is the time of the baseline LOS propagation time, delta_max can be derived based on the link budget, and the network synchronization (synchronization) error bound can be defined by the operator of the carrier network or can be predefined according to relevant standards. In Expression 1, delta_max represents the time difference between the reference radar signal and the last (i.e., most recently transmitted) target radar reference signal associated with that reference radar signal.

[0208] Referring ​ , in some designs, in principle, there is a temporal proximity between the reference radar signal and the set of target radar signals. In some designs, this temporal proximity can be quantified based on the timing drift rate of the first base station (or Tx gNB). The higher the timing drift rate, the closer the temporal proximity between the reference radar signal and the target radar reference signal(s).

[0209] Referring ​ , in some designs, the first base station can send an indication of the temporal drift associated with the first base station to the radar controller. In some designs, the reference radar signal is scheduled in response to the temporal drift indication. For example, the reference radar signal can be scheduled periodically, can be scheduled in response to detecting that the temporal drift exceeds a certain threshold, or some combination (e.g., performed periodically, but reducing the periodicity or performing an aperiodic reference radar signal operation when the time drift exceeds the threshold). Thus, in some designs, the periodicity of the reference radar signal can be configured based on the temporal drift indication. In a specific example, if the temporal drift indication indicates a temporal drift of approximately x ns within y time slots (assuming the x ns drift still meets the sensing accuracy requirements), the radar controller can configure the reference radar signal every y time slots.

[0210] Referring ​ , in some designs, the radar reference waveform can be transmitted periodically to compensate for the timing drift problem at the first base station mentioned above. In one example, the Rx time difference between each target radar signal and the reference radar signal is used to estimate the distance and R sum . The timing drift at the first base station (or Tx gNB) may make the estimated distance and R sum inaccurate.

[0211] Referring ​, in some designs, the first base station and / or the radar controller may further transmit a time-domain drift indication to the second base station. For example, the radar controller may signal the time-domain drift of the first base station to the second base station (or Rx gNB) to enhance detection / estimation performance. For example, to achieve low Doppler estimation, the target radar signal may span a long time duration, and if the drift rate is high (e.g., above a certain threshold), the Tx timing drift effect may not be negligible. As mentioned above, in some designs, the first base station may send a time-domain drift indication to the radar controller such that the first base station or the radar controller may send a time-domain drift indication to the second base station.

[0212] ​ Illustrates a radar time slot format 1800A according to the first aspect of the present disclosure. In ​ , the symbol used for the transmission of the reference radar signal is denoted as "R", and the symbol used for the transmission of the target radar signal is denoted as "T". In ​ , a 1:1 radar time slot format is used, whereby a single symbol (symbol 1) is assigned to the reference radar signal, and a single symbol (symbol 4) is assigned to the target radar signal.

[0213] ​ Illustrates a radar time slot format 1800B according to the second aspect of the present disclosure. In ​ , the symbol used for the transmission of the reference radar signal is denoted as "R", and the symbol used for the transmission of the target radar signal is denoted as "T". In ​ , a 1:N radar time slot format is used, whereby a single symbol (symbol 1) is assigned to the reference radar signal, and multiple symbols (symbols 5, 7, and 9) are assigned to three corresponding target radar signals. In this example, R may be calculated three times (e.g., redundantly associated with the same target or with different targets) for each of these target radar signals relative to the reference radar signal. sum Three times (e.g., redundantly associated with the same target or relative to different targets).

[0214] In the foregoing detailed description, it can be seen that in the various examples different features are grouped together. This manner of disclosure should not be construed as an intention that the example clauses have more features than those expressly recited in each clause. On the contrary, various aspects of the present disclosure may include less than all of the features of the individual example clauses disclosed. Accordingly, the appended clauses are hereby to be considered incorporated into the description, where each clause by itself may be a separate example. Although each dependent clause may, in the clauses, refer to a particular combination with one of the other clauses, the aspects of that dependent clause are not limited to that particular combination. It will be appreciated that other example clauses may also include combinations of aspects of dependent clauses with the subject matter of any other dependent or independent clause or any feature with other dependent and independent clauses. The various aspects disclosed herein expressly include such combinations, unless expressly stated or readily inferable that a particular combination is not intended (e.g., conflicting aspects such as defining an element as both an insulator and a conductor). In addition, it is intended that aspects of the clauses may be included in any other independent clause, even if the clause is not directly subordinate to that independent clause.

[0215] The various implementation examples are described in the following numbered clauses:

[0216] Clause 1. A method of operating a radar controller, comprising: determining a radar time slot format that configures the transmission of a reference radar signal on a first symbol over a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; and transmitting an indication of the radar time slot format to the first base station and the second base station.

[0217] Clause 2. The method of Clause 1, wherein the reference radar signal and the at least one target radar signal are time division multiplexed (TDM).

[0218] Clause 3. The method of any one of Clauses 1 to 2, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0219] Clause 4. The method of Clause 3, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0220] Clause 5. The method of any one of Clauses 1 to 4, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0221] Clause 6. The method as in Clause 5, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0222] Clause 7. The method as in any one of Clauses 1 to 6, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0223] Clause 8. The method as in any one of Clauses 1 to 7, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal before the at least one target radar signal.

[0224] Clause 9. The method as in any one of Clauses 1 to 8, further comprising: transmitting to the second base station an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0225] Clause 10. The method as in any one of Clauses 1 to 9, further comprising: receiving at the radar controller an indication of a time domain drift associated with the first base station from the first base station.

[0226] Clause 11. The method as in Clause 10, wherein the reference radar signal is scheduled in response to the time domain drift indication.

[0227] Clause 12. The method as in Clause 11, wherein the periodicity of the reference radar signal is configured based on the time domain drift indication.

[0228] Clause 13. The method as in any one of Clauses 10 to 12, further comprising: transmitting the time domain drift indication to the second base station.

[0229] Clause 14. A method of operating a first base station, comprising: receiving from a radar controller a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; transmitting the reference radar signal on the first symbol via the first link from the first base station to the second base station; and transmitting the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0230] Clause 15: The method as in Clause 14, wherein the reference radar signal and the at least one target radar signal are time division multiplexed (TDM).

[0231] Clause 16: A method as in any one of Clauses 14 to 15, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0232] Clause 17: A method as in Clause 16, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0233] Clause 18: A method as in any one of Clauses 14 to 17, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0234] Clause 19: A method as in Clause 18, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0235] Clause 20: A method as in any one of Clauses 18 to 19, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0236] Clause 21: A method as in any one of Clauses 14 to 20, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0237] Clause 22: A method as in any one of Clauses 14 to 21, further comprising: determining a time domain drift associated with the first base station.

[0238] Clause 23: A method as in Clause 22, further comprising: transmitting an indication of the time domain drift to the radar controller.

[0239] Clause 24: A method as in Clause 23, wherein the reference radar signal is scheduled in response to the time domain drift indication.

[0240] Clause 25: A method as in Clause 24, wherein the periodicity of the reference radar signal is configured based on the time domain drift indication.

[0241] Clause 26: A method as in any one of Clauses 22 to 25, further comprising: transmitting an indication of the time domain drift to the second base station.

[0242] Clause 27: A method of operating a second base station, comprising: receiving a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from a first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; receiving the reference radar signal on the first symbol via the first link from the first base station to the second base station; and receiving the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0243] Clause 28: The method of clause 27, wherein the reference radar signal and the at least one target radar signal are time division multiplexed (TDM'd).

[0244] Clause 29: The method of any one of clauses 27 to 28, wherein the first link corresponds to a line of sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line of sight (NLOS) link from the first base station to the second base station.

[0245] Clause 30: The method of clause 29, wherein the reference radar signal is received on the LOS link via a default beam, and wherein the at least one target radar signal is received on the at least one NLOS link via a dynamically determined beam set.

[0246] Clause 31: The method of any one of clauses 27 to 30, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0247] Clause 32: The method of clause 31, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0248] Clause 33: The method of any one of clauses 27 to 32, wherein the radar time slot format explicitly designates the at least one target radar signal as associated with the reference radar signal.

[0249] Clause 34: The method of any one of clauses 27 to 33, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0250] Clause 35: The method of any one of clauses 27 to 34, further comprising: receiving from the radar controller an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0251] Clause 36: The method of any one of Clauses 27 to 35 further comprises: receiving an indication of a time-domain drift associated with the first base station from the first base station or the radar controller.

[0252] Clause 37: The method of Clause 36, wherein the time-domain drift indication indicates that the time-domain drift is below a time threshold.

[0253] Clause 38: The method of Clause 37 further comprises: performing a low-Doppler estimation of the at least one target radar signal without considering the time-domain drift indication.

[0254] Clause 39: The method of any one of Clauses 36 to 38, wherein the time-domain drift indication indicates that the time-domain drift is equal to or greater than the time threshold.

[0255] Clause 40: The method of Clause 39 further comprises: performing a low-Doppler estimation of the at least one target radar signal based on the time-domain drift indication.

[0256] Clause 41: A radar controller comprising: a memory; at least one transceiver; and at least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor being configured to: determine a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; and convey an indication of the radar time slot format to the first base station and the second base station via the at least one transceiver.

[0257] Clause 42: The radar controller of Clause 41, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0258] Clause 43: The radar controller of any one of Clauses 41 to 42, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0259] Clause 44: The radar controller of Clause 43, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0260] Clause 45: A radar controller as in any one of Clauses 41 to 44, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0261] Clause 46: A radar controller as in Clause 45, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0262] Clause 47: A radar controller as in any one of Clauses 41 to 46, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0263] Clause 48: A radar controller as in any one of Clauses 41 to 47, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0264] Clause 49: A radar controller as in any one of Clauses 41 to 48, wherein the at least one processor is further configured to: transmit, via the at least one transceiver, the expected reception time associated with the reference radar signal and the expected reception time uncertainty associated with the reference radar signal to the second base station.

[0265] Clause 50: A radar controller as in any one of Clauses 41 to 49, wherein the at least one processor is further configured to: receive, via the at least one transceiver at the radar controller, an indication of the time domain drift associated with the first base station.

[0266] Clause 51: A radar controller as in Clause 50, wherein the reference radar signal is scheduled in response to the time domain drift indication.

[0267] Clause 52: A radar controller as in Clause 51, wherein the periodicity of the reference radar signal is configured based on the time domain drift indication.

[0268] Clause 53: A radar controller as in any one of Clauses 50 to 52, wherein the at least one processor is further configured to: transmit, via the at least one transceiver, the time domain drift indication to the second base station.

[0269] Clause 54: A first base station, comprising: a memory; at least one transceiver; and at least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor configured to: receive a radar time slot format from a radar controller via the at least one transceiver, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; transmit the reference radar signal on the first symbol via the first link from the first base station to the second base station via the at least one transceiver; and transmit the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station via the at least one transceiver.

[0270] Clause 55: The first base station of Clause 54, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0271] Clause 56: The first base station of any one of Clauses 54 to 55, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0272] Clause 57: The first base station of Clause 56, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0273] Clause 58: The first base station of any one of Clauses 54 to 57, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0274] Clause 59: The first base station of Clause 58, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0275] Clause 60: The first base station of any one of Clauses 58 to 59, wherein the radar time slot format explicitly designates the at least one target radar signal as associated with the reference radar signal.

[0276] Clause 61: The first base station of any one of Clauses 54 to 60, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0277] Clause 62: The first base station as in any one of Clauses 54 to 61, wherein the at least one processor is further configured to: determine a time-domain drift associated with the first base station.

[0278] Clause 63: The first base station as in Clause 62, wherein the at least one processor is further configured to: transmit an indication of the time-domain drift to the radar controller via the at least one transceiver.

[0279] Clause 64: The first base station as in Clause 63, wherein the reference radar signal is scheduled in response to the time-domain drift indication.

[0280] Clause 65: The first base station as in Clause 64, wherein the periodicity of the reference radar signal is configured based on the time-domain drift indication.

[0281] Clause 66: The first base station as in any one of Clauses 62 to 65, wherein the at least one processor is further configured to: transmit an indication of the time-domain drift to the second base station via the at least one transceiver.

[0282] Clause 67: A second base station, comprising: a memory; at least one transceiver; and at least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor being configured to: receive, via the at least one transceiver, a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol from a first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol from the first base station to the second base station via at least one second link; receive, via the at least one transceiver, the reference radar signal on the first symbol via the first link from the first base station to the second base station; and receive, via the at least one transceiver, the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0283] Clause 68: The second base station as in Clause 67, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0284] Clause 69: The second base station as in any one of Clauses 67 to 68, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0285] Clause 70: The second base station as in Clause 69, wherein the reference radar signal is received on the LOS link via a default beam, and wherein the at least one target radar signal is received on the at least one NLOS link via a dynamically determined beam set.

[0286] Clause 71: The second base station as in any one of Clauses 67 to 70, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0287] Clause 72: The second base station as in Clause 71, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0288] Clause 73: The second base station as in any one of Clauses 67 to 72, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0289] Clause 74: The second base station as in any one of Clauses 67 to 73, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0290] Clause 75: The second base station as in any one of Clauses 67 to 74, wherein the at least one processor is further configured to: receive, via the at least one transceiver, an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal from the radar controller.

[0291] Clause 76: The second base station as in any one of Clauses 67 to 75, wherein the at least one processor is further configured to: receive, via the at least one transceiver, an indication of a time domain drift associated with the first base station from the first base station or the radar controller.

[0292] Clause 77: The second base station as in Clause 76, wherein the time domain drift indication indicates that the time domain drift is below a time threshold.

[0293] Clause 78: The second base station as in Clause 77, wherein the at least one processor is further configured to: perform a low Doppler estimation of the at least one target radar signal without considering the time domain drift indication.

[0294] Clause 79: The second base station as in any one of Clauses 76 to 78, wherein the time domain drift indication indicates that the time domain drift is equal to or greater than the time threshold.

[0295] Clause 80: A second base station as in Clause 79, wherein the at least one processor is further configured to perform a low Doppler estimation of the at least one target radar signal based on the time domain drift indication.

[0296] Clause 81: A radar controller, comprising: means for determining a radar time slot format that configures the transmission of a reference radar signal on a first symbol over a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; and means for transmitting an indication of the radar time slot format to the first base station and the second base station.

[0297] Clause 82: The radar controller as in Clause 81, wherein the reference radar signal and the at least one target radar signal are time division multiplexed (TDM).

[0298] Clause 83: The radar controller as in any one of Clauses 81 to 82, wherein the first link corresponds to a line of sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line of sight (NLOS) link from the first base station to the second base station.

[0299] Clause 84: The radar controller as in Clause 83, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0300] Clause 85: The radar controller as in any one of Clauses 81 to 84, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0301] Clause 86: The radar controller as in Clause 85, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0302] Clause 87: The radar controller as in any one of Clauses 81 to 86, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0303] Clause 88: The radar controller as in any one of Clauses 81 to 87, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0304] Clause 89: The radar controller as in any one of Clauses 81 to 88 further includes: means for transmitting to the second base station an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0305] Clause 90: The radar controller as in any one of Clauses 81 to 89 further includes: means for receiving at the radar controller an indication of a time-domain drift associated with the first base station from the first base station.

[0306] Clause 91: The radar controller as in Clause 90, wherein the reference radar signal is scheduled in response to the time-domain drift indication.

[0307] Clause 92: The radar controller as in Clause 91, wherein the periodicity of the reference radar signal is configured based on the time-domain drift indication.

[0308] Clause 93: The radar controller as in any one of Clauses 90 to 92 further includes: means for transmitting the time-domain drift indication to the second base station.

[0309] Clause 94: A first base station includes: means for receiving from a radar controller a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; means for transmitting the reference radar signal on the first symbol via the first link from the first base station to the second base station; and means for transmitting the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0310] Clause 95: The first base station as in Clause 94, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0311] Clause 96: The first base station as in any one of Clauses 94 to 95, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0312] Clause 97: The first base station as in Clause 96, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

[0313] Clause 98: The first base station as in any one of Clauses 94 to 97, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0314] Clause 99: The first base station as in Clause 98, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0315] Clause 100: The first base station as in any one of Clauses 98 to 99, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0316] Clause 101: The first base station as in any one of Clauses 94 to 100, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal before the at least one target radar signal.

[0317] Clause 102: The first base station as in any one of Clauses 94 to 101, further comprising: means for determining a time domain drift associated with the first base station.

[0318] Clause 103: The first base station as in Clause 102, further comprising: means for transmitting an indication of the time domain drift to the radar controller.

[0319] Clause 104: The first base station as in Clause 103, wherein the reference radar signal is scheduled in response to the time domain drift indication.

[0320] Clause 105: The first base station as in Clause 104, wherein the periodicity of the reference radar signal is configured based on the time domain drift indication.

[0321] Clause 106: The first base station as in any one of Clauses 102 to 105, further comprising: means for transmitting an indication of the time domain drift to the second base station.

[0322] Clause 107: A second base station, comprising: means for receiving a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol via a first link from a first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; means for receiving the reference radar signal on the first symbol via the first link from the first base station to the second base station; and means for receiving the at least one target radar signal on the at least one second symbol via the at least one second link from the first base station to the second base station.

[0323] Clause 108: A second base station as in clause 107, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM'd).

[0324] Clause 109: A second base station as in any one of clauses 107 to 108, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0325] Clause 110: A second base station as in clause 109, wherein the reference radar signal is received on the LOS link via a default beam, and wherein the at least one target radar signal is received on the at least one NLOS link via a dynamically determined set of beams.

[0326] Clause 111: A second base station as in any one of clauses 107 to 110, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0327] Clause 112: A second base station as in clause 111, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0328] Clause 113: A second base station as in any one of clauses 107 to 112, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0329] Clause 114: A second base station as in any one of clauses 107 to 113, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0330] Clause 115: A second base station as in any one of clauses 107 to 114, further comprising: means for receiving from the radar controller an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0331] Clause 116: A second base station as in any one of clauses 107 to 115, further comprising: means for receiving from the first base station or the radar controller an indication of a time domain drift associated with the first base station.

[0332] Clause 117: A second base station as in clause 116, wherein the time domain drift indication indicates that the time domain drift is below a time threshold.

[0333] Clause 118: The second base station as in Clause 117 further includes: means for performing a low Doppler estimation of the at least one target radar signal without considering the time domain drift indication.

[0334] Clause 119: The second base station as in any one of Clauses 116 to 118, wherein the time domain drift indication indicates that the time domain drift is equal to or greater than a time threshold.

[0335] Clause 120: The second base station as in Clause 119 further includes: means for performing a low Doppler estimation of the at least one target radar signal based on the time domain drift indication.

[0336] Clause 121: A non-transitory computer-readable medium storing computer-executable instructions that, when executed by a radar controller, cause the radar controller to: determine a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from a first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first base station to the second base station; and transmit an indication of the radar time slot format to the first base station and the second base station.

[0337] Clause 122: The non-transitory computer-readable medium as in Clause 121, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0338] Clause 123: The non-transitory computer-readable medium as in any one of Clauses 121 to 122, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0339] Clause 124: The non-transitory computer-readable medium as in Clause 123, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined set of beams.

[0340] Clause 125: The non-transitory computer-readable medium as in any one of Clauses 121 to 124, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0341] Clause 126: The non-transitory computer-readable medium as in Clause 125, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0342] Clause 127: A non-transitory computer-readable medium as in any one of Clauses 121 to 126, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0343] Clause 128: A non-transitory computer-readable medium as in any one of Clauses 121 to 127, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0344] Clause 129: A non-transitory computer-readable medium as in any one of Clauses 121 to 128, further comprising instructions that, when executed by the radar controller, further cause the radar controller to perform the following operations: transmit to the second base station an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0345] Clause 130: A non-transitory computer-readable medium as in any one of Clauses 121 to 129, further comprising instructions that, when executed by the radar controller, further cause the radar controller to perform the following operations: receive at the radar controller an indication of a time domain drift associated with the first base station.

[0346] Clause 131: The non-transitory computer-readable medium as in Clause 130, wherein the reference radar signal is scheduled in response to the time domain drift indication.

[0347] Clause 132: The non-transitory computer-readable medium as in Clause 131, wherein the periodicity of the reference radar signal is configured based on the time domain drift indication.

[0348] Clause 133: A non-transitory computer-readable medium as in any one of Clauses 130 to 132, further comprising instructions that, when executed by the radar controller, further cause the radar controller to perform the following operations: transmit the time domain drift indication to the second base station.

[0349] Clause 134: A non-transitory computer-readable medium storing computer-executable instructions that, when executed by a first base station, cause the first base station to: receive a radar time slot format from a radar controller, the radar time slot format configuring the transmission of a reference radar signal on a first symbol over a first link from the first base station to a second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; transmit the reference radar signal on the first symbol over the first link from the first base station to the second base station; and transmit the at least one target radar signal on the at least one second symbol over the at least one second link from the first base station to the second base station.

[0350] Clause 135: The non-transitory computer-readable medium of Clause 134, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM'd).

[0351] Clause 136: The non-transitory computer-readable medium of any one of Clauses 134 to 135, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0352] Clause 137: The non-transitory computer-readable medium of Clause 136, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined set of beams.

[0353] Clause 138: The non-transitory computer-readable medium of any one of Clauses 134 to 137, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0354] Clause 139: The non-transitory computer-readable medium of Clause 138, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0355] Clause 140: The non-transitory computer-readable medium of any one of Clauses 138 to 139, wherein the radar time slot format explicitly designates the at least one target radar signal as associated with the reference radar signal.

[0356] Clause 141: The non-transitory computer-readable medium of any one of Clauses 134 to 140, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0357] Clause 142: A non-transitory computer-readable medium as in any one of Clauses 134 to 141, further comprising instructions that, when executed by the first base station, further cause the first base station to perform the following operations: determining a time-domain drift associated with the first base station.

[0358] Clause 143: The non-transitory computer-readable medium as in Clause 142, further comprising instructions that, when executed by the first base station, further cause the first base station to perform the following operations: transmitting an indication of the time-domain drift to the radar controller.

[0359] Clause 144: The non-transitory computer-readable medium as in Clause 143, wherein the reference radar signal is scheduled in response to the time-domain drift indication.

[0360] Clause 145: The non-transitory computer-readable medium as in Clause 144, wherein the periodicity of the reference radar signal is configured based on the time-domain drift indication.

[0361] Clause 146: The non-transitory computer-readable medium as in any one of Clauses 142 to 145, further comprising instructions that, when executed by the first base station, further cause the first base station to perform the following operations: transmitting an indication of the time-domain drift to the second base station.

[0362] Clause 147: A non-transitory computer-readable medium storing computer-executable instructions that, when executed by a second base station, cause the second base station to: receive a radar time-slot format from a radar controller, the radar time-slot format configuring the transmission of a reference radar signal on a first symbol over a first link from a first base station to the second base station, followed by the transmission of at least one target radar signal on at least one second symbol over at least one second link from the first base station to the second base station; receive the reference radar signal on the first symbol over the first link from the first base station to the second base station; and receive the at least one target radar signal on the at least one second symbol over the at least one second link from the first base station to the second base station.

[0363] Clause 148: The non-transitory computer-readable medium as in Clause 147, wherein the reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

[0364] Clause 149: The non-transitory computer-readable medium as in any one of Clauses 147 to 148, wherein the first link corresponds to a line-of-sight (LOS) link from the first base station to the second base station, and wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first base station to the second base station.

[0365] Clause 150: A non-transitory computer-readable medium as in Clause 149, wherein the reference radar signal is received on the LOS link via a default beam, and wherein the at least one target radar signal is received on the at least one NLOS link via a dynamically determined set of beams.

[0366] Clause 151: A non-transitory computer-readable medium as in any one of Clauses 147 to 150, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal.

[0367] Clause 152: A non-transitory computer-readable medium as in Clause 151, wherein the at least one second symbol is specified via at least one offset relative to the first symbol.

[0368] Clause 153: A non-transitory computer-readable medium as in any one of Clauses 147 to 152, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal.

[0369] Clause 154: A non-transitory computer-readable medium as in any one of Clauses 147 to 153, wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

[0370] Clause 155: A non-transitory computer-readable medium as in any one of Clauses 147 to 154, further comprising instructions that, when executed by the second base station, further cause the second base station to: receive from the radar controller an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

[0371] Clause 156: A non-transitory computer-readable medium as in any one of Clauses 147 to 155, further comprising instructions that, when executed by the second base station, further cause the second base station to: receive from the first base station or the radar controller an indication of a time domain drift associated with the first base station.

[0372] Clause 157: A non-transitory computer-readable medium as in Clause 156, wherein the time domain drift indication indicates that the time domain drift is below a time threshold.

[0373] Clause 158: A non-transitory computer-readable medium as in Clause 157, further comprising instructions that, when executed by the second base station, further cause the second base station to: perform a low Doppler estimate of the at least one target radar signal without considering the time domain drift indication.

[0374] Clause 159: A non-transitory computer-readable medium as in any one of Clauses 156 to 158, wherein the time-domain drift indication indicates that the time-domain drift is equal to or greater than a time threshold.

[0375] Clause 160: The non-transitory computer-readable medium as in Clause 159, further comprising instructions that, when executed by the second base station, further cause the second base station to perform the following operations: perform a low Doppler estimation of the at least one target radar signal based on the time-domain drift indication.

[0376] Those skilled in the art will appreciate that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0377] In addition, those skilled in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps are described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the particular application and the design constraints imposed on the overall system. The skilled person may implement the described functionality in a different manner for each particular application, but such implementation decisions should not be construed as causing a departure from the scope of the present disclosure.

[0378] The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented or executed using a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but in an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0379] The methods, sequences, and / or algorithms described in connection with various aspects disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module can reside in random access memory (RAM), flash memory, read only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In an alternative, the storage medium can be integrated into the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal (e.g., a UE). In an alternative, the processor and the storage medium can reside in the user terminal as discrete components.

[0380] In one or more exemplary aspects, the described functionality can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored on or transmitted via a computer-readable medium as one or more instructions or code. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium can be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0381] While the foregoing disclosure shows illustrative aspects of the present disclosure, it should be noted that various changes and modifications may be made therein without departing from the scope of the present disclosure as defined by the appended claims. The functions, steps, and / or acts in the method claims according to aspects of the present disclosure described herein need not be performed in any particular order. Further, although elements of the present disclosure may be described or claimed in the singular, the plural is also contemplated unless expressly stated to be limited to the singular.

Claims

1. A method of operating a radar controller, comprising: Determining a radar time slot format configured for transmitting a reference radar signal on a first symbol over a first link from a first wireless network component to a second wireless network component, followed by transmitting at least one target radar signal on at least one second symbol over at least one second link from the first wireless network component to the second wireless network component; And Transmitting an indication of the radar time slot format to the first wireless network component and the second wireless network component, Wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first wireless network component to the second wireless network component, and Wherein the at least one NLOS link is associated with one or more signal reflections of the at least one target radar signal reflected off a target object for tracking.

2. The method according to claim 1, wherein The reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

3. The method according to claim 1, Wherein the first link corresponds to a line-of-sight (LOS) link from the first wireless network component to the second wireless network component.

4. The method according to claim 3, Wherein the reference radar signal is transmitted on the LOS link via a default beam, and Wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

5. The method according to claim 1, wherein, The radar time slot format explicitly specifies the first symbol for the reference radar signal.

6. The method according to claim 5, wherein, The at least one second symbol is specified via at least one offset relative to the first symbol.

7. The method according to claim 1, Wherein the radar time slot format explicitly designates the at least one target radar signal as associated with the reference radar signal, or Wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

8. The method according to claim 1, further comprising: Transmitting an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal to the second wireless network component.

9. The method according to claim 1, further comprising: Receiving, at the radar controller, an indication of a time domain drift associated with the first wireless network component from the first wireless network component.

10. The method according to claim 9, wherein, The reference radar signal is scheduled in response to the time domain drift indication.

11. The method according to claim 10, wherein, The periodicity of the reference radar signal is configured based on the time domain drift indication.

12. The method according to claim 9, further comprising: Transmitting the time domain drift indication to the second wireless network component.

13. A method of operating a first wireless network component, comprising: Receiving a radar time slot format from a radar controller, the radar time slot format configured for the transmission of a reference radar signal on a first symbol via a first link from the first wireless network component to the second wireless network component, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first wireless network component to the second wireless network component; Transmitting the reference radar signal on the first symbol via the first link from the first wireless network component to the second wireless network component; And Transmitting the at least one target radar signal on the at least one second symbol via the at least one second link from the first wireless network component to the second wireless network component, Wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first wireless network component to the second wireless network component, and Wherein the at least one NLOS link is associated with one or more signal reflections of the at least one target radar signal reflecting off a target object for tracking.

14. The method according to claim 13, wherein, The reference radar signal and the at least one target radar signal are time-division multiplexed (TDM'd).

15. The method of claim 13, Wherein the first link corresponds to a line-of-sight (LOS) link from the first wireless network component to the second wireless network component.

16. The method of claim 15, Wherein the reference radar signal is transmitted on the LOS link via a default beam, and Wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined set of beams.

17. The method of claim 13, Wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal, Wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

18. The method of claim 13, further comprising: Determining a time domain drift associated with the first wireless network component.

19. The method of claim 18, further comprising: Transmitting an indication of the time domain drift to the radar controller.

20. The method according to claim 19, wherein, The reference radar signal is scheduled in response to the time domain drift indication.

21. A method of operating a second wireless network component, comprising: Receiving a radar time slot format from a radar controller, the radar time slot format configured for the transmission of a reference radar signal on a first symbol via a first link from a first wireless network component to the second wireless network component, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first wireless network component to the second wireless network component; Receiving the reference radar signal on the first symbol via the first link from the first wireless network component to the second wireless network component; And Receiving the at least one target radar signal on the at least one second symbol via the at least one second link from the first wireless network component to the second wireless network component, wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first wireless network component to the second wireless network component, and wherein the at least one NLOS link is associated with one or more signal reflections of the at least one target radar signal reflecting off a target object for tracking.

22. The method according to claim 21, wherein, The reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

23. The method according to claim 21, wherein the first link corresponds to a line-of-sight (LOS) link from the first wireless network component to the second wireless network component.

24. The method according to claim 23, wherein the reference radar signal is received on the LOS link via a default beam, and wherein the at least one target radar signal is received on the at least one NLOS link via a dynamically determined beam set.

25. The method according to claim 21, wherein the radar time slot format explicitly specifies the first symbol for the reference radar signal, or wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal, or wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

26. The method according to claim 21, further comprising: Receiving from the radar controller an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

27. The method according to claim 21, further comprising: Receiving from the first wireless network component or the radar controller an indication of a time domain drift associated with the first wireless network component.

28. The method according to claim 27, wherein, The time domain drift indication indicates that the time domain drift is below a time threshold.

29. The method according to claim 27, wherein, The time domain drift indication indicates that the time domain drift is equal to or greater than the time threshold.

30. A radar controller, comprising: A memory; At least one transceiver; And At least one processor communicatively coupled to the memory and the at least one transceiver, the at least one processor being configured to: Determine a radar time slot format that configures the transmission of a reference radar signal on a first symbol via a first link from a first wireless network component to a second wireless network component, followed by the transmission of at least one target radar signal on at least one second symbol via at least one second link from the first wireless network component to the second wireless network component; And Transmit an indication of the radar time slot format to the first wireless network component and the second wireless network component via the at least one transceiver, wherein the at least one second link corresponds to at least one non-line-of-sight (NLOS) link from the first wireless network component to the second wireless network component, and wherein the at least one NLOS link is associated with one or more signal reflections of the at least one target radar signal reflected off a target object for tracking.

31. The radar controller according to claim 30, wherein, The reference radar signal and the at least one target radar signal are time-division multiplexed (TDM).

32. The radar controller according to claim 30, wherein the first link corresponds to a line-of-sight (LOS) link from the first wireless network component to the second wireless network component.

33. The radar controller according to claim 32, wherein the reference radar signal is transmitted on the LOS link via a default beam, and wherein the at least one target radar signal is transmitted on the at least one NLOS link via a dynamically determined beam set.

34. The radar controller according to claim 30, wherein The radar time slot format explicitly specifies the first symbol for the reference radar signal.

35. The radar controller according to claim 34, wherein, The at least one second symbol is specified via at least one offset relative to the first symbol.

36. The radar controller according to claim 30, wherein the radar time slot format explicitly designates the at least one target radar signal as being associated with the reference radar signal, or wherein the at least one target radar signal is implicitly associated with the reference radar signal based on the reference radar signal corresponding to the most recent reference radar signal prior to the at least one target radar signal.

37. The radar controller according to claim 30, the at least one processor being further configured to: transmit to the second wireless network component an expected reception time associated with the reference radar signal and an expected reception time uncertainty associated with the reference radar signal.

38. The radar controller according to claim 30, the at least one processor being further configured to: receive, via the at least one transceiver, an indication of a time-domain drift associated with the first wireless network component from the first wireless network component.

39. The radar controller according to claim 38, wherein, The reference radar signal is scheduled in response to the time-domain drift indication.

40. The radar controller according to claim 39, wherein, The periodicity of the reference radar signal is configured based on the time-domain drift indication.

41. The radar controller according to claim 38, the at least one processor being further configured to: transmit, via the at least one transceiver, the time-domain drift indication to the second wireless network component.

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