WO2025065706A1

WO2025065706A1 - User equipment assisted transmit receive point synchronization

Info

Publication number: WO2025065706A1
Application number: PCT/CN2023/123029
Authority: WO
Inventors: Shaozhen GUO; Mostafa KHOSHNEVISAN; Jing Dai
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2023-09-29
Filing date: 2023-09-29
Publication date: 2025-04-03
Anticipated expiration: 2026-03-29

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a first sounding reference signal (SRS) to a first transmit receive point (TRP) and a second SRS to a second TRP. The UE may receive a first channel state information reference signal (CSI-RS) associated with the first SRS and a second CSI-RS associated with the second SRS. The UE may estimate a first relative time offset and/or a first relative phase offset using the first CSI-RS and the second CSI-RS. The UE may transmit a report of the first relative time offset and/or the first relative phase offset to the first TRP and/or the second TRP. Numerous other aspects are described.

Description

USER EQUIPMENT ASSISTED TRANSMIT RECEIVE POINT SYNCHRONIZATION

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for assisting with transmit receive point synchronization.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless network may include one or more network nodes that support communication for wireless communication devices, such as a user equipment (UE) or multiple UEs. A UE may communicate with a network node via downlink communications and uplink communications. “Downlink” (or “DL” ) refers to a communication link from the network node to the UE, and “uplink” (or “UL” ) refers to a communication link from the UE to the network node. Some wireless networks may support device-to-device communication, such as via a local link (e.g., a sidelink (SL) , a wireless local area network (WLAN) link, and/or a wireless personal area network (WPAN) link, among other examples) .

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different UEs to communicate on a municipal, national, regional, and/or global level. New Radio (NR) , which may be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the 3GPP. NR is designed to better support mobile broadband internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink, using CP-OFDM and/or single-carrier frequency division multiplexing (SC-FDM) (also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink, as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. As the demand for mobile broadband access continues to increase, further improvements in LTE, NR, and other radio access technologies remain useful.

SUMMARY

Some aspects described herein relate to a method of wireless communication performed by a user equipment (UE) . The method may include transmitting a first sounding reference signal (SRS) to a first transmit receive point (TRP) and a second SRS to a second TRP. The method may include receiving a first channel state information reference signal (CSI-RS) associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The method may include estimating one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS. The method may include transmitting a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.

Some aspects described herein relate to a method of wireless communication performed by a first TRP. The method may include receiving a first SRS. The method may include transmitting a first CSI-RS associated with the first SRS, where the first CSI-RS is precoded based on the first received SRS. The method may include receiving a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP. The method may include synchronizing one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.

Some aspects described herein relate to an apparatus for wireless communication at a UE. The apparatus may include one or more memories and one or more processors coupled to the one or more memories. The one or more processors may be configured to cause the UE to transmit a first SRS to a first TRP and a second SRS to a second TRP. The one or more processors may be configured to cause the UE to receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The one or more processors may be configured to cause the UE to estimate one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS. The one or more processors may be configured to cause the UE to transmit a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.

Some aspects described herein relate to an apparatus for wireless communication at a first TRP. The apparatus may include one or more memories and one or more processors coupled to the one or more memories. The one or more processors may be configured to receive a first SRS. The one or more processors may be configured to cause the first TRP to transmit a first CSI-RS associated with the first SRS, where the first CSI-RS is precoded based on the first received SRS. The one or more processors may be configured to cause the first TRP to receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP. The one or more processors may be configured to cause the first TRP to synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a UE. The set of instructions, when executed by one or more processors of the UE, may cause the UE to transmit a first SRS to a first TRP and a second SRS to a second TRP. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The set of instructions, when executed by one or more processors of the UE, may cause the UE to estimate one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS. The set of instructions, when executed by one or more processors of the UE, may cause the UE to transmit a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a first TRP. The set of instructions, when executed by one or more processors of the first TRP, may cause the first TRP to receive a first SRS. The set of instructions, when executed by one or more processors of the first TRP, may cause the first TRP to transmit a first CSI-RS associated with the first SRS, where the first CSI-RS is precoded based on the first received SRS. The set of instructions, when executed by one or more processors of the first TRP, may cause the first TRP to receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP. The set of instructions, when executed by one or more processors of the first TRP, may cause the first TRP to synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for transmitting a first SRS to a first TRP and a second SRS to a second TRP. The apparatus may include means for receiving a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The apparatus may include means for estimating one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS. The apparatus may include means for transmitting a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for receiving a first SRS. The apparatus may include means for transmitting a first CSI-RS associated with the first SRS, where the first CSI-RS is precoded based on the first received SRS. The apparatus may include means for receiving a report of one or more of a relative time offset or a relative phase offset between the apparatus and another apparatus. The apparatus may include means for synchronizing one or more of a time or a phase with the other apparatus using the one or more of the relative time offset or the relative phase offset.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, network entity, network node, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages, will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.

While aspects are described in the present disclosure by illustration to some examples, those skilled in the art will understand that such aspects may be implemented in many different arrangements and scenarios. Techniques described herein may be implemented using different platform types, devices, systems, shapes, sizes, and/or packaging arrangements. For example, some aspects may be implemented via integrated chip embodiments or other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, and/or artificial intelligence devices) . Aspects may be implemented in chip-level components, modular components, non-modular components, non-chip-level components, device-level components, and/or system-level components. Devices incorporating described aspects and features may include additional components and features for implementation and practice of claimed and described aspects. For example, transmission and reception of wireless signals may include one or more components for analog and digital purposes (e.g., hardware components including antennas, radio frequency (RF) chains, power amplifiers, modulators, buffers, processors, interleavers, adders, and/or summers) . It is intended that aspects described herein may be practiced in a wide variety of devices, components, systems, distributed arrangements, and/or end-user devices of varying size, shape, and constitution.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a diagram illustrating an example of a wireless network, in accordance with the present disclosure.

Fig. 2 is a diagram illustrating an example of a network node in communication with a user equipment (UE) in a wireless network, in accordance with the present disclosure.

Fig. 3 is a diagram illustrating an example disaggregated base station architecture, in accordance with the present disclosure.

Fig. 4 illustrates an example logical architecture of a distributed random access network, in accordance with the present disclosure.

Fig. 5 is a diagram illustrating an example of multiple transmit receive point (TRP) communication, in accordance with the present disclosure.

Fig. 6 is a diagram illustrating an example of antenna ports, in accordance with the present disclosure.

Fig. 7 is a diagram illustrating an example associated with UE assistance with TRP synchronization, in accordance with the present disclosure.

Fig. 8 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 9 is a diagram illustrating an example of synchronization of multiple TRPs, in accordance with the present disclosure.

Fig. 10 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 11 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 12 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 13 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 14 is a diagram illustrating example of resource associations, in accordance with the present disclosure.

Fig. 15 is a diagram illustrating an example process performed, for example, at a UE or an apparatus of a UE, in accordance with the present disclosure.

Fig. 16 is a diagram illustrating an example process performed, for example, at a first TRP or an apparatus of a first TRP, in accordance with the present disclosure.

Fig. 17 is a diagram of an example apparatus for wireless communication, in accordance with the present disclosure.

Fig. 18 is a diagram of an example apparatus for wireless communication, in accordance with the present disclosure.

DETAILED DESCRIPTION

A channel state information (CSI) reference signal (CSI-RS) may carry information used for downlink channel estimation (e.g., downlink CSI acquisition) , which may be used for scheduling, link adaptation, or beam management, among other examples. A network entity (e.g., gNB) may configure a set of CSI-RSs for a user equipment (UE) , and the UE may measure the configured set of CSI-RSs. Based at least in part on the measurements, the UE may perform channel estimation and may report channel estimation parameters to the network entity (e.g., in a CSI report) . The network entity may use the CSI report to select transmission parameters for downlink communications to the UE. The UE may report CSI for CSI-RSs from multiple transmit receive points (TRPs) associated with the network entity.

However, channel estimates may become inaccurate as the phases at different TRPs drift over time. The drift may be due to a relative timing drift among TRPs due to a clock drift if the TRPs are not connected to a global positioning system (GPS) . Even if TRPs are GPS-connected, there is a random phase drift at each TRP due to phase lock loop (PLL) dynamics. Time and phase synchronization can be performed by over-the-air signaling among the TRPs, but one challenge with UE-assisted synchronization is that UEs are typically not transmit (Tx) /receive (Rx) calibrated (e.g., have not accounted for transmission and reception gain and phase imbalances at the UE) . If the UE is not Tx/Rx calibrated, the UE may not be able to effectively assist with TRP synchronization. The lack of accurate TRP synchronization may degrade communications, which wastes signaling resources and increases latency.

According to various aspects described herein, a UE may assist with TRP synchronization while ensuring that any Tx/Rx mismatch at the UE does not impact the synchronization procedure. The UE may transmit a first sounding reference signal (SRS) to a first TRP and a second SRS to a second TRP. The UE may receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The UE may estimate a relative time and phase offset using the first received CSI-RS (y₁) and the second received CSI-RS (y₂) . Each CSI-RS may be precoded based on the corresponding SRS. CSI-RS precoding may ensure that the phase of the channel does not impact the received CSI-RS.

For example, the UE may calculate a product of y₁ and a conjugate of y₂ (y₂*) on each subcarrier of the received CSI-RSs. This ensures that the phase of the UE’s Tx/Rx mismatch is cancelled out, and the only remaining phase is the relative timing/phase offset between the two TRPsThe relative timing/phase offset between the two TRPsmay be estimated by observation ofacross multiple subcarriers. The UE may transmit the estimated ρ₁₂, to one of the TRPs and then that TRP can use the received ρ₁₂, to synchronize to the other TRP.

By calculating and observingacross the TRPs for multiple subcarriers, the UE may provide a true offset that is not affected by any Tx/Rx mismatch at the UE. In this way, the TRPs may synchronize and not suffer degraded communications. As a result, the TRPs and served UEs may conserve signaling resources and not experience increased latency. Timing/phase offsets may be determined for, and provided to, more than two TRPs.

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. One skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, or the like (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

While aspects may be described herein using terminology commonly associated with a 5G or New Radio (NR) radio access technology (RAT) , aspects of the present disclosure can be applied to other RATs, such as a 3G RAT, a 4G RAT, and/or a RAT subsequent to 5G (e.g., 6G) .

Fig. 1 is a diagram illustrating an example of a wireless network 100, in accordance with the present disclosure. The wireless network 100 may be or may include elements of a 5G (e.g., NR) network and/or a 4G (e.g., Long Term Evolution (LTE) ) network, among other examples. The wireless network 100 may include one or more network nodes 110 (shown as a network node 110a, a network node 110b, a network node 110c, and a network node 110d) , a UE 120 or multiple UEs 120 (shown as a UE 120a, a UE 120b, a UE 120c, a UE 120d, and a UE 120e) , and/or other entities. A network node 110 is a network node that communicates with UEs 120. As shown, a network node 110 may include one or more network nodes. For example, a network node 110 may be an aggregated network node, meaning that the aggregated network node is configured to utilize a radio protocol stack that is physically or logically integrated within a single radio access network (RAN) node (e.g., within a single device or unit) . As another example, a network node 110 may be a disaggregated network node (sometimes referred to as a disaggregated base station) , meaning that the network node 110 is configured to utilize a protocol stack that is physically or logically distributed among two or more nodes (such as one or more central units (CUs) , one or more distributed units (DUs) , or one or more radio units (RUs) ) .

In some examples, a network node 110 is or includes a network node that communicates with UEs 120 via a radio access link, such as an RU. In some examples, a network node 110 is or includes a network node that communicates with other network nodes 110 via a fronthaul link or a midhaul link, such as a DU. In some examples, a network node 110 is or includes a network node that communicates with other network nodes 110 via a midhaul link or a core network via a backhaul link, such as a CU. In some examples, a network node 110 (such as an aggregated network node 110 or a disaggregated network node 110) may include multiple network nodes, such as one or more RUs, one or more CUs, and/or one or more DUs. A network node 110 may include, for example, an NR base station, an LTE base station, a Node B, an eNB (e.g., in 4G) , a gNB (e.g., in 5G) , an access point, a TRP, a DU, an RU, a CU, a mobility element of a network, a core network node, a network element, a network equipment, a RAN node, or a combination thereof. In some examples, the network nodes 110 may be interconnected to one another or to one or more other network nodes 110 in the wireless network 100 through various types of fronthaul, midhaul, and/or backhaul interfaces, such as a direct physical connection, an air interface, or a virtual network, using any suitable transport network.

In some examples, a network node 110 may provide communication coverage for a particular geographic area. In the Third Generation Partnership Project (3GPP) , the term “cell” can refer to a coverage area of a network node 110 and/or a network node subsystem serving this coverage area, depending on the context in which the term is used. A network node 110 may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs 120 with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs 120 with service subscriptions. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs 120 having association with the femto cell (e.g., UEs 120 in a closed subscriber group (CSG) ) . A network node 110 for a macro cell may be referred to as a macro network node. A network node 110 for a pico cell may be referred to as a pico network node. A network node 110 for a femto cell may be referred to as a femto network node or an in-home network node. In the example shown in Fig. 1, the network node 110a may be a macro network node for a macro cell 102a, the network node 110b may be a pico network node for a pico cell 102b, and the network node 110c may be a femto network node for a femto cell 102c. A network node may support one or multiple (e.g., three) cells. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a network node 110 that is mobile (e.g., a mobile network node) .

In some aspects, the terms “base station” or “network node” may refer to an aggregated base station, a disaggregated base station, an integrated access and backhaul (IAB) node, a relay node, or one or more components thereof. For example, in some aspects, “base station” or “network node” may refer to a CU, a DU, an RU, a Near-Real Time (Near-RT) RAN Intelligent Controller (RIC) , or a Non-Real Time (Non-RT) RIC, or a combination thereof. In some aspects, the terms “base station” or “network node” may refer to one device configured to perform one or more functions, such as those described herein in connection with the network node 110. In some aspects, the terms “base station” or “network node” may refer to a plurality of devices configured to perform the one or more functions. For example, in some distributed systems, each of a quantity of different devices (which may be located in the same geographic location or in different geographic locations) may be configured to perform at least a portion of a function, or to duplicate performance of at least a portion of the function, and the terms “base station” or “network node” may refer to any one or more of those different devices. In some aspects, the terms “base station” or “network node” may refer to one or more virtual base stations or one or more virtual base station functions. For example, in some aspects, two or more base station functions may be instantiated on a single device. In some aspects, the terms “base station” or “network node” may refer to one of the base station functions and not another. In this way, a single device may include more than one base station.

The wireless network 100 may include one or more relay stations. A relay station is a network node that can receive a transmission of data from an upstream node (e.g., a network node 110 or a UE 120) and send a transmission of the data to a downstream node (e.g., a UE 120 or a network node 110) . A relay station may be a UE 120 that can relay transmissions for other UEs 120. In the example shown in Fig. 1, the network node 110d (e.g., a relay network node) may communicate with the network node 110a (e.g., a macro network node) and the UE 120d in order to facilitate communication between the network node 110a and the UE 120d. A network node 110 that relays communications may be referred to as a relay station, a relay base station, a relay network node, a relay node, a relay, or the like.

The wireless network 100 may be a heterogeneous network that includes network nodes 110 of different types, such as macro network nodes, pico network nodes, femto network nodes, relay network nodes, or the like. These different types of network nodes 110 may have different transmit power levels, different coverage areas, and/or different impacts on interference in the wireless network 100. For example, macro network nodes may have a high transmit power level (e.g., 5 to 40 watts) whereas pico network nodes, femto network nodes, and relay network nodes may have lower transmit power levels (e.g., 0.1 to 2 watts) .

A network controller 130 may couple to or communicate with a set of network nodes 110 and may provide coordination and control for these network nodes 110. The network controller 130 may communicate with the network nodes 110 via a backhaul communication link or a midhaul communication link. The network nodes 110 may communicate with one another directly or indirectly via a wireless or wireline backhaul communication link. In some aspects, the network controller 130 may be a CU or a core network device, or may include a CU or a core network device.

The UEs 120 may be dispersed throughout the wireless network 100, and each UE 120 may be stationary or mobile. A UE 120 may include, for example, an access terminal, a terminal, a mobile station, and/or a subscriber unit. A UE 120 may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device, a biometric device, a wearable device (e.g., a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (e.g., a smart ring or a smart bracelet) ) , an entertainment device (e.g., a music device, a video device, and/or a satellite radio) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, a UE function of a network node, and/or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs 120 may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. An MTC UE and/or an eMTC UE may include, for example, a robot, an unmanned aerial vehicle, a remote device, a sensor, a meter, a monitor, and/or a location tag, that may communicate with a network node, another device (e.g., a remote device) , or some other entity. Some UEs 120 may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband IoT) devices. Some UEs 120 may be considered a Customer Premises Equipment. A UE 120 may be included inside a housing that houses components of the UE 120, such as processor components and/or memory components. In some examples, the processor components and the memory components may be coupled together. For example, the processor components (e.g., one or more processors) and the memory components (e.g., a memory) may be operatively coupled, communicatively coupled, electronically coupled, and/or electrically coupled.

In general, any number of wireless networks 100 may be deployed in a given geographic area. Each wireless network 100 may support a particular RAT and may operate on one or more frequencies. A RAT may be referred to as a radio technology, an air interface, or the like. A frequency may be referred to as a carrier, a frequency channel, or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some examples, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (e.g., without using a network node 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, or a vehicle-to-pedestrian (V2P) protocol) , and/or a mesh network. In such examples, a UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the network node 110.

Devices of the wireless network 100 may communicate using the electromagnetic spectrum, which may be subdivided by frequency or wavelength into various classes, bands, channels, or the like. For example, devices of the wireless network 100 may communicate using one or more operating bands. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz –7.125 GHz) and FR2 (24.25 GHz –52.6 GHz) . It should be understood that although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “Sub-6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz –300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Recent 5G NR studies have identified an operating band for these mid-band frequencies as frequency range designation FR3 (7.125 GHz –24.25 GHz) . Frequency bands falling within FR3 may inherit FR1 characteristics and/or FR2 characteristics, and thus may effectively extend features of FR1 and/or FR2 into mid-band frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operation beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR4a or FR4-1 (52.6 GHz –71 GHz) , FR4 (52.6 GHz –114.25 GHz) , and FR5 (114.25 GHz –300 GHz) . Each of these higher frequency bands falls within the EHF band.

With the above examples in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like, if used herein, may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like, if used herein, may broadly represent frequencies that may include mid-band frequencies, may be within FR2, FR4, FR4-a or FR4-1, and/or FR5, or may be within the EHF band. It is contemplated that the frequencies included in these operating bands (e.g., FR1, FR2, FR3, FR4, FR4-a, FR4-1, and/or FR5) may be modified, and techniques described herein are applicable to those modified frequency ranges.

In some aspects, a UE (e.g., a UE 120) may include a communication manager 140. As described in more detail elsewhere herein, the communication manager 140 may transmit a first SRS to a first TRP and a second SRS to a second TRP. The communication manager 140 may receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The communication manager 140 may estimate one or more of a first relative time offset or a first relative phase offset using the first CSI-RS and the second CSI-RS. The communication manager 140 may transmit a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP. Additionally, or alternatively, the communication manager 140 may perform one or more other operations described herein.

In some aspects, a first TRP (e.g., network node 110) may include a communication manager 150. As described in more detail elsewhere herein, the communication manager 150 may receive a first SRS. The communication manager 150 may transmit a first CSI-RS associated with the first SRS. The communication manager 150 may receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP. The communication manager 150 may synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset. Additionally, or alternatively, the communication manager 150 may perform one or more other operations described herein.

As indicated above, Fig. 1 is provided as an example. Other examples may differ from what is described with regard to Fig. 1.

Fig. 2 is a diagram illustrating an example 200 of a network node 110 in communication with a UE 120 in a wireless network 100, in accordance with the present disclosure. The network node 110 may be equipped with a set of antennas 234a through 234t, such as T antennas (T ≥ 1) . The UE 120 may be equipped with a set of antennas 252a through 252r, such as R antennas (R ≥ 1) . The network node 110 of example 200 includes one or more radio frequency components, such as antennas 234 and a modem 232. In some examples, a network node 110 may include an interface, a communication component, or another component that facilitates communication with the UE 120 or another network node. Some network nodes 110 may not include radio frequency components that facilitate direct communication with the UE 120, such as one or more CUs, or one or more DUs.

At the network node 110, a transmit processor 220 may receive data, from a data source 212, intended for the UE 120 (or a set of UEs 120) . The transmit processor 220 may select one or more modulation and coding schemes (MCSs) for the UE 120 based at least in part on one or more channel quality indicators (CQIs) received from that UE 120. The network node 110 may process (e.g., encode and modulate) the data for the UE 120 based at least in part on the MCS (s) selected for the UE 120 and may provide data symbols for the UE 120. The transmit processor 220 may process system information (e.g., for semi-static resource partitioning information (SRPI) ) and control information (e.g., CQI requests, grants, and/or upper layer signaling) and provide overhead symbols and control symbols. The transmit processor 220 may generate reference symbols for reference signals (e.g., a cell-specific reference signal (CRS) or a demodulation reference signal (DMRS) ) and synchronization signals (e.g., a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide a set of output symbol streams (e.g., T output symbol streams) to a corresponding set of modems 232 (e.g., T modems) , shown as modems 232a through 232t. For example, each output symbol stream may be provided to a modulator component (shown as MOD) of a modem 232. Each modem 232 may use a respective modulator component to process a respective output symbol stream (e.g., for OFDM) to obtain an output sample stream. Each modem 232 may further use a respective modulator component to process (e.g., convert to analog, amplify, filter, and/or upconvert) the output sample stream to obtain a downlink signal. The modems 232a through 232t may transmit a set of downlink signals (e.g., T downlink signals) via a corresponding set of antennas 234 (e.g., T antennas) , shown as antennas 234a through 234t.

At the UE 120, a set of antennas 252 (shown as antennas 252a through 252r) may receive the downlink signals from the network node 110 and/or other network nodes 110 and may provide a set of received signals (e.g., R received signals) to a set of modems 254 (e.g., R modems) , shown as modems 254a through 254r. For example, each received signal may be provided to a demodulator component (shown as DEMOD) of a modem 254. Each modem 254 may use a respective demodulator component to condition (e.g., filter, amplify, downconvert, and/or digitize) a received signal to obtain input samples. Each modem 254 may use a demodulator component to further process the input samples (e.g., for OFDM) to obtain received symbols. A MIMO detector 256 may obtain received symbols from the modems 254, may perform MIMO detection on the received symbols if applicable, and may provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, may provide decoded data for the UE 120 to a data sink 260, and may provide decoded control information and system information to a controller/processor 280. The term “controller/processor” may refer to one or more controllers, one or more processors, or a combination thereof. A channel processor may determine a reference signal received power (RSRP) parameter, a received signal strength indicator (RSSI) parameter, a reference signal received quality (RSRQ) parameter, and/or a CQI parameter, among other examples. In some examples, one or more components of the UE 120 may be included in a housing 284.

The network controller 130 may include a communication unit 294, a controller/processor 290, and a memory 292. The network controller 130 may include, for example, one or more devices in a core network. The network controller 130 may communicate with the network node 110 via the communication unit 294.

One or more antennas (e.g., antennas 234a through 234t and/or antennas 252a through 252r) may include, or may be included within, one or more antenna panels, one or more antenna groups, one or more sets of antenna elements, and/or one or more antenna arrays, among other examples. An antenna panel, an antenna group, a set of antenna elements, and/or an antenna array may include one or more antenna elements (within a single housing or multiple housings) , a set of coplanar antenna elements, a set of non-coplanar antenna elements, and/or one or more antenna elements coupled to one or more transmission and/or reception components, such as one or more components of Fig. 2.

On the uplink, at the UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports that include RSRP, RSSI, RSRQ, and/or CQI) from the controller/processor 280. The transmit processor 264 may generate reference symbols for one or more reference signals. The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the modems 254 (e.g., for DFT-s- OFDM or CP-OFDM) , and transmitted to the network node 110. In some examples, the modem 254 of the UE 120 may include a modulator and a demodulator. In some examples, the UE 120 includes a transceiver. The transceiver may include any combination of the antenna (s) 252, the modem (s) 254, the MIMO detector 256, the receive processor 258, the transmit processor 264, and/or the TX MIMO processor 266. The transceiver may be used by a processor (e.g., the controller/processor 280) and the memory 282 to perform aspects of any of the methods described herein (e.g., with reference to Figs. 4-18) .

At the network node 110, the uplink signals from UE 120 and/or other UEs may be received by the antennas 234, processed by the modem 232 (e.g., a demodulator component, shown as DEMOD, of the modem 232) , detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120. The receive processor 238 may provide the decoded data to a data sink 239 and provide the decoded control information to the controller/processor 240. The network node 110 may include a communication unit 244 and may communicate with the network controller 130 via the communication unit 244. The network node 110 may include a scheduler 246 to schedule one or more UEs 120 for downlink and/or uplink communications. In some examples, the modem 232 of the network node 110 may include a modulator and a demodulator. In some examples, the network node 110 includes a transceiver. The transceiver may include any combination of the antenna (s) 234, the modem (s) 232, the MIMO detector 236, the receive processor 238, the transmit processor 220, and/or the TX MIMO processor 230. The transceiver may be used by a processor (e.g., the controller/processor 240) and the memory 242 to perform aspects of any of the methods described herein (e.g., with reference to Figs. 4-18) .

The controller/processor of a network entity (e.g., the controller/processor 240 of the network node 110) , the controller/processor 280 of the UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with UE-assisted TRP synchronization, as described in more detail elsewhere herein. In some aspects, the first TRP described herein is the network node 110, is included in the network node 110, or includes one or more components of the network node 110 shown in Fig. 2. For example, the controller/processor 240 of the network node 110, the controller/processor 280 of the UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 1500 of Fig. 15, process 1600 of Fig. 16, and/or other processes as described herein. The memory 242 and the memory 282 may store data and program codes for the network node 110 and the UE 120, respectively. In some examples, the memory 242 and/or the memory 282 may include a non-transitory computer-readable medium storing one or more instructions (e.g., code and/or program code) for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, and/or interpreting) by one or more processors of the network node 110 and/or the UE 120, may cause the one or more processors, the UE 120, and/or the network node 110 to perform or direct operations of, for example, process 1500 of Fig. 15, process 1600 of Fig. 16, and/or other processes as described herein. In some examples, executing instructions may include running the instructions, converting the instructions, compiling the instructions, and/or interpreting the instructions, among other examples.

In some aspects, a UE (e.g., a UE 120) includes means for transmitting a first SRS to a first TRP and a second SRS to a second TRP; means for receiving a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS; means for estimating one or more of a first relative time offset or a first relative phase offset using the first CSI-RS and the second CSI-RS; and/or means for transmitting a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP. The means for the UE to perform operations described herein may include, for example, one or more of communication manager 140, antenna 252, modem 254, MIMO detector 256, receive processor 258, transmit processor 264, TX MIMO processor 266, controller/processor 280, or memory 282.

In some aspects, a first TRP (e.g., a network node 110) includes means for receiving a first SRS; means for transmitting a first CSI-RS associated with the first SRS; and/or means for receiving a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP; and/or means for synchronizing one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset. In some aspects, the means for the first TRP to perform operations described herein may include, for example, one or more of communication manager 150, transmit processor 220, TX MIMO processor 230, modem 232, antenna 234, MIMO detector 236, receive processor 238, controller/processor 240, memory 242, or scheduler 246.

In some aspects, an individual processor may perform all of the functions described as being performed by the one or more processors. In some aspects, one or more processors may collectively perform a set of functions. For example, a first set of (one or more) processors of the one or more processors may perform a first function described as being performed by the one or more processors, and a second set of (one or more) processors of the one or more processors may perform a second function described as being performed by the one or more processors. The first set of processors and the second set of processors may be the same set of processors or may be different sets of processors. Reference to “one or more processors” should be understood to refer to any one or more of the processors described in connection with Fig. 2. Reference to “one or more memories” should be understood to refer to any one or more memories of a corresponding device, such as the memory described in connection with Fig. 2. For example, functions described as being performed by one or more memories can be performed by the same subset of the one or more memories or different subsets of the one or more memories.

While blocks in Fig. 2 are illustrated as distinct components, the functions described above with respect to the blocks may be implemented in a single hardware, software, or combination component or in various combinations of components. For example, the functions described with respect to the transmit processor 264, the receive processor 258, and/or the TX MIMO processor 266 may be performed by or under the control of the controller/processor 280.

As indicated above, Fig. 2 is provided as an example. Other examples may differ from what is described with regard to Fig. 2.

Deployment of communication systems, such as 5G NR systems, may be arranged in multiple manners with various components or constituent parts. In a 5G NR system, or network, a network node, a network entity, a mobility element of a network, a RAN node, a core network node, a network element, a base station, or a network equipment may be implemented in an aggregated or disaggregated architecture. For example, a base station (such as a Node B (NB) , an evolved NB (eNB) , an NR base station, a 5G NB, an access point (AP) , a TRP, or a cell, among other examples) , or one or more units (or one or more components) performing base station functionality, may be implemented as an aggregated base station (also known as a standalone base station or a monolithic base station) or a disaggregated base station. “Network entity” or “network node” may refer to a disaggregated base station, or to one or more units of a disaggregated base station (such as one or more CUs, one or more DUs, one or more RUs, or a combination thereof) .

An aggregated base station (e.g., an aggregated network node) may be configured to utilize a radio protocol stack that is physically or logically integrated within a single RAN node (e.g., within a single device or unit) . A disaggregated base station (e.g., a disaggregated network node) may be configured to utilize a protocol stack that is physically or logically distributed among two or more units (such as one or more CUs, one or more DUs, or one or more RUs) . In some examples, a CU may be implemented within a network node, and one or more DUs may be co-located with the CU, or alternatively, may be geographically or virtually distributed throughout one or multiple other network nodes. The DUs may be implemented to communicate with one or more RUs. Each of the CU, DU, and RU also can be implemented as virtual units, such as a virtual central unit (VCU) , a virtual distributed unit (VDU) , or a virtual radio unit (VRU) , among other examples.

Base station-type operation or network design may consider aggregation characteristics of base station functionality. For example, disaggregated base stations may be utilized in an IAB network, an open radio access network (O-RAN (such as the network configuration sponsored by the O-RAN Alliance) ) , or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN) ) to facilitate scaling of communication systems by separating base station functionality into one or more units that can be individually deployed. A disaggregated base station may include functionality implemented across two or more units at various physical locations, as well as functionality implemented for at least one unit virtually, which can enable flexibility in network design. The various units of the disaggregated base station can be configured for wired or wireless communication with at least one other unit of the disaggregated base station.

Fig. 3 is a diagram illustrating an example disaggregated base station architecture 300, in accordance with the present disclosure. The disaggregated base station architecture 300 may include a CU 310 that can communicate directly with a core network 320 via a backhaul link, or indirectly with the core network 320 through one or more disaggregated control units (such as a Near-RT RIC 325 via an E2 link, or a Non-RT RIC 315 associated with a Service Management and Orchestration (SMO) Framework 305, or both) . A CU 310 may communicate with one or more DUs 330 via respective midhaul links, such as through F1 interfaces. Each of the DUs 330 may communicate with one or more RUs 340 via respective fronthaul links. Each of the RUs 340 may communicate with one or more UEs 120 via respective radio frequency (RF) access links. In some implementations, a UE 120 may be simultaneously served by multiple RUs 340.

Each of the units, including the CUs 310, the DUs 330, the RUs 340, as well as the Near-RT RICs 325, the Non-RT RICs 315, and the SMO Framework 305, may include one or more interfaces or be coupled with one or more interfaces configured to receive or transmit signals, data, or information (collectively, signals) via a wired or wireless transmission medium. Each of the units, or an associated processor or controller providing instructions to one or multiple communication interfaces of the respective unit, can be configured to communicate with one or more of the other units via the transmission medium. In some examples, each of the units can include a wired interface, configured to receive or transmit signals over a wired transmission medium to one or more of the other units, and a wireless interface, which may include a receiver, a transmitter or transceiver (such as an RF transceiver) , configured to receive or transmit signals, or both, over a wireless transmission medium to one or more of the other units.

In some aspects, the CU 310 may host one or more higher layer control functions. Such control functions can include radio resource control (RRC) functions, packet data convergence protocol (PDCP) functions, or service data adaptation protocol (SDAP) functions, among other examples. Each control function can be implemented with an interface configured to communicate signals with other control functions hosted by the CU 310. The CU 310 may be configured to handle user plane functionality (for example, Central Unit –User Plane (CU-UP) functionality) , control plane functionality (for example, Central Unit –Control Plane (CU-CP) functionality) , or a combination thereof. In some implementations, the CU 310 can be logically split into one or more CU-UP units and one or more CU-CP units. A CU-UP unit can communicate bidirectionally with a CU-CP unit via an interface, such as the E1 interface when implemented in an O-RAN configuration. The CU 310 can be implemented to communicate with a DU 330, as necessary, for network control and signaling.

Each DU 330 may correspond to a logical unit that includes one or more base station functions to control the operation of one or more RUs 340. In some aspects, the DU 330 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers depending, at least in part, on a functional split, such as a functional split defined by the 3GPP. In some aspects, the one or more high PHY layers may be implemented by one or more modules for forward error correction (FEC) encoding and decoding, scrambling, and modulation and demodulation, among other examples. In some aspects, the DU 330 may further host one or more low PHY layers, such as implemented by one or more modules for a fast Fourier transform (FFT) , an inverse FFT (iFFT) , digital beamforming, or physical random access channel (PRACH) extraction and filtering, among other examples. Each layer (which also may be referred to as a module) can be implemented with an interface configured to communicate signals with other layers (and modules) hosted by the DU 330, or with the control functions hosted by the CU 310.

Each RU 340 may implement lower-layer functionality. In some deployments, an RU 340, controlled by a DU 330, may correspond to a logical node that hosts RF processing functions or low-PHY layer functions, such as performing an FFT, performing an iFFT, digital beamforming, or PRACH extraction and filtering, among other examples, based on a functional split (for example, a functional split defined by the 3GPP) , such as a lower layer functional split. In such an architecture, each RU 340 can be operated to handle over the air (OTA) communication with one or more UEs 120. In some implementations, real-time and non-real-time aspects of control and user plane communication with the RU (s) 340 can be controlled by the corresponding DU 330. In some scenarios, this configuration can enable each DU 330 and the CU 310 to be implemented in a cloud-based RAN architecture, such as a vRAN architecture.

The SMO Framework 305 may be configured to support RAN deployment and provisioning of non-virtualized and virtualized network elements. For non-virtualized network elements, the SMO Framework 305 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements, which may be managed via an operations and maintenance interface (such as an O1 interface) . For virtualized network elements, the SMO Framework 305 may be configured to interact with a cloud computing platform (such as an open cloud (O-Cloud) platform 390) to perform network element life cycle management (such as to instantiate virtualized network elements) via a cloud computing platform interface (such as an O2 interface) . Such virtualized network elements can include, but are not limited to, CUs 310, DUs 330, RUs 340, non-RT RICs 315, and Near-RT RICs 325. In some implementations, the SMO Framework 305 can communicate with a hardware aspect of a 4G RAN, such as an open eNB (O-eNB) 311, via an O1 interface. Additionally, in some implementations, the SMO Framework 305 can communicate directly with each of one or more RUs 340 via a respective O1 interface. The SMO Framework 305 also may include a Non-RT RIC 315 configured to support functionality of the SMO Framework 305.

The Non-RT RIC 315 may be configured to include a logical function that enables non-real-time control and optimization of RAN elements and resources, Artificial Intelligence/Machine Learning (AI/ML) workflows including model training and updates, or policy-based guidance of applications/features in the Near-RT RIC 325. The Non-RT RIC 315 may be coupled to or communicate with (such as via an A1 interface) the Near-RT RIC 325. The Near-RT RIC 325 may be configured to include a logical function that enables near-real-time control and optimization of RAN elements and resources via data collection and actions over an interface (such as via an E2 interface) connecting one or more CUs 310, one or more DUs 330, or both, as well as an O-eNB, with the Near-RT RIC 325.

In some implementations, to generate AI/ML models to be deployed in the Near-RT RIC 325, the Non-RT RIC 315 may receive parameters or external enrichment information from external servers. Such information may be utilized by the Near-RT RIC 325 and may be received at the SMO Framework 305 or the Non-RT RIC 315 from non-network data sources or from network functions. In some examples, the Non-RT RIC 315 or the Near-RT RIC 325 may be configured to tune RAN behavior or performance. For example, the Non-RT RIC 315 may monitor long-term trends and patterns for performance and employ AI/ML models to perform corrective actions through the SMO Framework 305 (such as reconfiguration via an O1 interface) or via creation of RAN management policies (such as A1 interface policies) .

As indicated above, Fig. 3 is provided as an example. Other examples may differ from what is described with regard to Fig. 3.

Fig. 4 illustrates an example logical architecture of a distributed RAN 400, in accordance with the present disclosure.

A 5G access node 405 may include an access node controller 410. The access node controller 410 may be a CU of the distributed RAN 400. In some aspects, a backhaul interface to a 5G core network 415 may terminate at the access node controller 410. The 5G core network 415 may include a 5G control plane component 420 and a 5G user plane component 425 (e.g., a 5G gateway) , and the backhaul interface for one or both of the 5G control plane and the 5G user plane may terminate at the access node controller 410. Additionally, or alternatively, a backhaul interface to one or more neighbor access nodes 430 (e.g., another 5G access node 405 and/or an LTE access node) may terminate at the access node controller 410.

The access node controller 410 may include and/or may communicate with one or more TRPs 435 (e.g., via an F1 Control (F1-C) interface and/or an F1 User (F1-U) interface) . A TRP 435 may include a DU and/or an RU of the distributed RAN 400. In some aspects, a TRP 435 may correspond to a network node 110 described above in connection with Fig. 1. For example, different TRPs 435 may be included in different network nodes 110. Additionally, or alternatively, multiple TRPs 435 may be included in a single network node 110. In some aspects, a network node 110 may include a CU (e.g., access node controller 410) and/or one or more DUs (e.g., one or more TRPs 435) . In some cases, a TRP 435 may be referred to as a cell, a panel, an antenna array, or an array.

A TRP 435 may be connected to a single access node controller 410 or to multiple access node controllers 410. In some aspects, a dynamic configuration of split logical functions may be present within the architecture of distributed RAN 400, referred to elsewhere herein as a functional split. For example, a PDCP layer, an RLC layer, and/or a MAC layer may be configured to terminate at the access node controller 410 or at a TRP 435.

In some aspects, multiple TRPs 435 may transmit communications (e.g., the same communication or different communications) in the same transmission time interval (TTI) (e.g., a slot, a mini-slot, a subframe, or a symbol) or different TTIs using different quasi co-location (QCL) relationships (e.g., different spatial parameters, different transmission configuration indicator (TCI) states, different precoding parameters, and/or different beamforming parameters) . In some aspects, a TCI state may be used to indicate one or more QCL relationships. A TRP 435 may be configured to individually (e.g., using dynamic selection) or jointly (e.g., using joint transmission with one or more other TRPs 435) serve traffic to a UE 120.

As indicated above, Fig. 4 is provided as an example. Other examples may differ from what was described with regard to Fig. 4.

Fig. 5 is a diagram illustrating an example 500 of multi-TRP communication (sometimes referred to as multi-panel communication) , in accordance with the present disclosure. As shown in Fig. 5, multiple TRPs 505 may communicate with the same UE 120. A TRP 505 may correspond to a TRP 435 described above in connection with Fig. 4.

The multiple TRPs 505 (shown as TRP A and TRP B) may communicate with the same UE 120 in a coordinated manner (e.g., using coordinated multipoint transmissions) to improve reliability and/or increase throughput. The TRPs 505 may coordinate such communications via an interface between the TRPs 505 (e.g., a backhaul interface and/or an access node controller 410) . The interface may have a smaller delay and/or higher capacity when the TRPs 505 are co-located at the same network node 110 (e.g., when the TRPs 505 are different antenna arrays or panels of the same network node 110) , and may have a larger delay and/or lower capacity (as compared to co-location) when the TRPs 505 are located at different network nodes 110. The different TRPs 505 may communicate with the UE 120 using different QCL relationships (e.g., different TCI states) , different DMRS ports, and/or different layers (e.g., of a multi-layer communication) .

In a first multi-TRP transmission mode (e.g., Mode 1) , a single physical downlink control channel (PDCCH) may be used to schedule downlink data communications for a single physical downlink shared channel (PDSCH) . In this case, multiple TRPs 505 (e.g., TRP A and TRP B) may transmit communications to the UE 120 on the same PDSCH. For example, a communication may be transmitted using a single codeword with different spatial layers for different TRPs 505 (e.g., where one codeword maps to a first set of layers transmitted by a first TRP 505 and maps to a second set of layers transmitted by a second TRP 505) . As another example, a communication may be transmitted using multiple codewords, where different codewords are transmitted by different TRPs 505 (e.g., using different sets of layers) . In either case, different TRPs 505 may use different QCL relationships (e.g., different TCI states) for different DMRS ports corresponding to different layers. For example, a first TRP 505 may use a first QCL relationship or a first TCI state for a first set of DMRS ports corresponding to a first set of layers, and a second TRP 505 may use a second (different) QCL relationship or a second (different) TCI state for a second (different) set of DMRS ports corresponding to a second (different) set of layers. In some aspects, a TCI state in downlink control information (DCI) (e.g., transmitted on the PDCCH, such as DCI format 1_0 or DCI format 1_1) may indicate the first QCL relationship (e.g., by indicating a first TCI state) and the second QCL relationship (e.g., by indicating a second TCI state) . The first and the second TCI states may be indicated using a TCI field in the DCI. In general, the TCI field can indicate a single TCI state (for single-TRP transmission) or multiple TCI states (for multi-TRP transmission as discussed here) in this multi-TRP transmission mode (e.g., Mode 1) .

In a second multi-TRP transmission mode (e.g., Mode 2) , multiple PDCCHs may be used to schedule downlink data communications for multiple corresponding PDSCHs (e.g., one PDCCH for each PDSCH) . In this case, a first PDCCH may schedule a first codeword to be transmitted by a first TRP 505, and a second PDCCH may schedule a second codeword to be transmitted by a second TRP 505. Furthermore, first DCI (e.g., transmitted by the first TRP 505) may schedule a first PDSCH communication associated with a first set of DMRS ports with a first QCL relationship (e.g., indicated by a first TCI state) for the first TRP 505, and second DCI (e.g., transmitted by the second TRP 505) may schedule a second PDSCH communication associated with a second set of DMRS ports with a second QCL relationship (e.g., indicated by a second TCI state) for the second TRP 505. In this case, DCI (e.g., having DCI format 1_0 or DCI format 1_1) may indicate a corresponding TCI state for a TRP 505 corresponding to the DCI. The TCI field of a DCI indicates the corresponding TCI state (e.g., the TCI field of the first DCI indicates the first TCI state and the TCI field of the second DCI indicates the second TCI state) .

As indicated above, Fig. 5 is provided as an example. Other examples may differ from what is described with respect to Fig. 5.

Fig. 6 is a diagram illustrating an example 600 of antenna ports, in accordance with the present disclosure.

As shown in Fig. 6, a first physical antenna 605-1 may transmit information via a first channel h1, a second physical antenna 605-2 may transmit information via a second channel h2, a third physical antenna 605-3 may transmit information via a third channel h3, and a fourth physical antenna 605-4 may transmit information via a fourth channel h4. Such information may be conveyed via a logical antenna port, which may represent some combination of the physical antennas and/or channels. In some cases, a UE 120 may not have knowledge of the channels associated with the physical antennas, and may only operate based on knowledge of the channels associated with antenna ports, as defined below.

An antenna port may be defined such that a channel, over which a symbol on the antenna port is conveyed, can be inferred from a channel over which another symbol on the same antenna port is conveyed. In example 600, a channel associated with antenna port 1 (AP1) is represented as h1 -h2 + h3 + j*h4, where channel coefficients (e.g., 1, -1, 1, and j, in this case) represent weighting factors (e.g., indicating phase and/or gain) applied to each channel. Such weighting factors may be applied to the channels to improve signal power and/or signal quality at one or more receivers. Applying such weighting factors to channel transmissions may be referred to as precoding, and a precoder may refer to a specific set of weighting factors applied to a set of channels.

Similarly, a channel associated with antenna port 2 (AP2) is represented as h1 + j*h3, and a channel associated with antenna port 3 (AP3) is represented as 2*h1 -h2 + (1+j) *h3 + j*h4. In this case, antenna port 3 can be represented as the sum of antenna port 1 and antenna port 2 (e.g., AP3 = AP1 + AP2) because the sum of the expression representing antenna port 1 (h1 -h2 + h3 + j*h4) and the expression representing antenna port 2 (h1 + j*h3) equals the expression representing antenna port 3 (2*h1 -h2 + (1+j) *h3 + j*h4) . It can also be said that antenna port 3 is related to antenna ports 1 and 2 [AP1, AP2] via the precoder [1, 1] because 1 times the expression representing antenna port 1 plus 1 times the expression representing antenna port 2 equals the expression representing antenna port 3.

The antenna ports may be used to transmit and receive reference signals on an uplink channel and a downlink channel. The downlink channel may include a PDCCH that carries DCI, a PDSCH that carries downlink data, or a physical broadcast channel (PBCH) that carries system information. A downlink reference signal may include a synchronization signal block (SSB) or a CSI-RS, among other examples. An SSB may carry information used for initial network acquisition and synchronization, such as a primary synchronization signal (PSS) , a secondary synchronization signal (SSS) , a PBCH, and a PBCH DMRS. An SSB is sometimes referred to as a synchronization signal/PBCH (SS/PBCH) block. A CSI-RS may carry information used for downlink channel estimation (e.g., downlink CSI acquisition) , which may be used for scheduling, link adaptation, or beam management, among other examples. A network entity (e.g., network node 110) may configure a set of CSI-RSs for a UE (e.g., UE 120) , and the UE may measure the configured set of CSI-RSs. Based at least in part on the measurements, the UE may perform channel estimation and may report channel estimation parameters to the network entity (e.g., in a CSI report) , such as a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a CSI-RS resource indicator (CRI) , a layer indicator (LI) , a rank indicator (RI) , or an RSRP, among other examples. The network entity may use the CSI report to select transmission parameters for downlink communications to the UE, such as a number of transmission layers (e.g., a rank) , a precoding matrix (e.g., a precoder) , an MCS, or a refined downlink beam (e.g., using a beam refinement procedure or a beam management procedure) , among other examples.

The uplink channel may include a physical uplink control channel (PUCCH) that carries uplink control information (UCI) or a physical uplink shared channel (PUSCH) that carries uplink data. An uplink reference signal may include an SRS, among other examples. An SRS may carry information used for uplink channel estimation, which may be used for scheduling, link adaptation, precoder selection, or beam management, among other examples. The network entity may configure one or more SRS resource sets for the UE, and the UE may transmit SRSs on the configured SRS resource sets. An SRS resource set may include one or more resources (e.g., shown as SRS resources) , which may include time resources and/or frequency resources (e.g., a slot, a symbol, a resource block, and/or a periodicity for the time resources) . An SRS resource may include one or more antenna ports on which an SRS is to be transmitted (e.g., in a time-frequency resource) . Thus, a configuration for an SRS resource set may indicate one or more time-frequency resources in which an SRS is to be transmitted and may indicate one or more antenna ports on which the SRS is to be transmitted in those time-frequency resources. The network entity may measure the SRSs, may perform channel estimation based at least in part on the measurements, and may use the SRS measurements to configure communications with the UE.

For downlink transmission, a network entity may obtain CSI by requesting an SRS. For time-division duplexing (TDD) , where channel reciprocity can be assumed, if the quantity of transmit (Tx) antennas x is equal to the quantity of receive (Rx) antennas y, a UE (e.g., a UE 120) may represent these quantities as xTyR, where x = y. In this case, one SRS resource with x = y SRS ports can be used for channel sounding.

If the quantity of transmit antennas is smaller than the quantity of receive antennas (x < y) , the UE may switch SRS antennas, as all y antennas are to be sounded for downlink CSI acquisition, but the UE can transmit an SRS resource with up to only x ports at a time (sounding only x out of y antennas) .

A UE may use a precoded SRS for downlink CSI acquisition for SRS coverage enhancement and for SRS overhead reduction. The coverage enhancement may be due to the fact that SRS is beamformed or precoded. The SRS overhead reduction (SRS capacity enhancement) may be due to the total quantity of SRS ports that are sounded being reduced to a quantity of PDSCH layers (from the quantity of receive antennas) . In current specifications, the total quantity of ports for SRS for downlink CSI acquisition is the same as the quantity of UE receive antennas. For beamformed SRS, through proper SRS precoding, the total quantity of SRS ports can be reduced to the quantity of PDSCH layers, while the channel information required for downlink precoding can be obtained. For example, if the UE has 4 receive antennas and assuming 4T4R, one SRS resource with 4 ports may be needed to sound each of the 4 receive antennas, in legacy. But with precoded SRS, assuming that the precoding matrix is 4 × 2, only 2 SRS ports are needed, where 2 here corresponds to the maximum quantity of PDSCH layers.

One possible precoder for beamformed SRS is the U matrix (left-singular vector) corresponding to the singular value decomposition (SVD) of the downlink channel. In order to obtain the channel at the UE side (to calculate precoding for SRS) , CSI-RS measurements are used. Coherent joint transmission (CJT) may be used for PDSCH, where multiple TRPs transmit PDSCH communications coherently across different antennas of TRPs. Therefore, multiple CSI-RS resources (each transmitted from a TRP) may be needed for the UE to obtain the downlink channel. The precoding for SRS may be determined based on an aggregated downlink channel from multiple TRPs.

However, channel estimates may become inaccurate as the phases at different TRPs drift over time. The drift may be due to a relative timing drift among TRPs due to a clock drift if the TRPs are not connected to a GPS. Even if TRPs are GPS-connected, there is a random phase drift at each TRP due to PLL dynamics. The performance of CJT in distributed MIMO systems is very sensitive to phase mismatch. Especially in the case of MU-MIMO (multiple UEs being served by multiple TRPs on the same resources) , beam nulling (inserting nulls in the beam pattern) and zero forcing (applying an inverse signal) toward unintended UEs impose stringent requirements on phase synchronization across TRPs.

Time and phase synchronization can be performed by over-the-air signaling among the TRPs. However, this synchronization may not work in cases where the channel between TRPs is weak (e.g., due to down tilt in deployment or a channel with no line of sight (NLOS) ) . In some aspects, a UE that is located between TRPs (e.g., with a line of sight (LOS) channel to both TRPs) may assist the TRPs to achieve synchronization. The assistance may include UE-assisted synchronization for CJT. One challenge with UE-assisted synchronization is that UEs are typically not Tx/Rx calibrated. If the UE is not Tx/Rx calibrated, the UE may not be able to effectively assist with TRP synchronization. The lack of accurate TRP synchronization may degrade communications, which wastes signaling resources and increases latency.

As indicated above, Fig. 6 is provided as an example. Other examples may differ from what is described with regard to Fig. 6.

Fig. 7 is a diagram illustrating an example 700 associated with UE assistance with TRP synchronization, in accordance with the present disclosure. As shown in Fig. 7, a UE 710 (e.g., UE 120) may communicate with a TRP 715 (e.g., network node 110) and a TRP 720 (e.g., network node 110) via a wireless network (e.g., wireless communication network 100) .

According to various aspects described herein, a UE may assist with TRP synchronization while ensuring that any Tx/Rx mismatch at the UE does not impact the synchronization procedure. The UE may transmit a first SRS to a first TRP and a second SRS to a second TRP. The UE may receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS. The first CSI-RS may be precoded based on the first SRS and the second CSI-RS may be precoded based on the second SRS. The UE may estimate a relative time and phase offset using the first received CSI-RS (y₁) and the second received CSI-RS (y₂) . Each CSI-RS may be precoded based on the corresponding SRS. CSI-RS precoding may ensure that the phase of the channel does not impact the received CSI-RS.

By calculating and observingacross the TRPs for multiple subcarriers, the UE may provide a true offset that is not affected by any Tx/Rx mismatch at the UE. In this way, the TRPs may synchronize and not suffer degraded communications. As a result, the TRPs and served UEs may conserve signaling resources and not experience increased latency. Timing/phase offsets may be determined for and provided to more than two TRPs.

The UE may account for timing offsets and phase uncertainties of the TRPs. A Tx timing offset (Tx phase ramp over adjacent subcarriers separated by Δf) introduced by the clock jitter of TRP i may be represented byPhase uncertainty introduced by the Tx side clock jitter of TRP i may be represented byRx timing offset (Rx phase ramp over adjacent subcarriers separated by Δf) introduced by the clock jitter of TRP i may be represented byPhase uncertainty introduced by the Rx side clock jitter of TRP i may be represented byThe UE may estimate the relative timing offset (ρ₁₂) and the relative phase uncertaintybetween a pair of TRPs (TRP1 and TRP2) . These may be represented as andWith the focus on TDD, the relative timing offset and relative phase uncertainty is with respect to the combined Tx + Rx. It may be expected that the timing offset and phase uncertainty for both Tx and Rx of a given TRP are not the same (due to the clock/PLL of the Tx and Rx of a given TRP being different) .

Example 700 shows UE-assisted synchronization with calculation ofAs shown by reference number 725, the UE 710 may transmit a first SRS (signal received as z₁) to TRP 715. As shown by reference number 730, TRP 715 may transmit a first CSI-RS to the UE 710. The first CSI-RS may correspond to the first SRS (e.g., precoded based on the first SRS) . As shown by reference number 735, the UE 710 may transmit a second SRS (signal received as z₂) to TRP 720. As shown by reference number 740, TRP 720 may transmit a second CSI-RS to the UE 710. The second CSI-RS may correspond to the second SRS (e.g., precoded based on the second SRS) . The first SRS and the second SRS may be the same SRS or different SRSs.

In some aspects, a first transmit antenna 742 of the UE 710 corresponding to an antenna of the first SRS may be the same antenna as a first receive antenna of the UE 710 corresponding to the first received CSI-RS. A second transmit antenna 744 of the UE 710 corresponding to an antenna of the second SRS may be the same antenna as a second receive antenna of the UE 710 corresponding to the second received CSI-RS.

The UE 710 may receive the first CSI-RS (signal received as y₁) and the second CSI-RS (signal received as y₂) . As shown by reference number 745, the UE 710 may calculateAs shown by reference number 750, the UE 710 may estimate the relative timing offset ρ₁₂ and/or the relative phase offsetbetween TRP 715 and TRP 720. The offsets may be estimated across multiple subcarriers (e.g., all the subcarriers of the CSI-RSs) .

The UE 710 may transmit a report of the relative offsets to one or both of the TRPs. As shown by reference number 755, the UE 710 may transmit the report to TRP 720. As shown by reference number 760, TRP 720 may synchronize with TRP 715 using the relative timing offset and/or the relative phase offset.

The estimation of the relative timing offset and the relative phase offset will be described in more detail. The channel for the first SRS z₁ from the UE 710 on the transmit antenna t to TRP 715 (TRP1) on the receive antenna r at subcarrier k may be formulated as: The termrepresents the UE Tx side gain and phase imbalance introduced by the transmit antenna t of the UE 710. The termmay represent the phase uncertainty of antenna r at TRP 715 (TRP1) . The termmay represent the timing offset at the Rx side of TRP 715 (TRP1) . The termmay represent the uplink channel between UE transmit antenna t and TRP 715 receive antenna r. TRP 715 may precode the first CSI-RS by, for example, modulating the first CSI-RS withof normalized z₁. The received first CSI-RS signal may be The termmay represent the UE Rx side gain and phase imbalance at the receive antenna t. The termmay represent the Tx side phase uncertainty at TRP 715 (TRP1) . The term may represent the Tx side timing offset at TRP 715 (TRP1) . The termmay represent the downlink channel from transmit antenna r at TRP 715 to receive antenna t at the UE 710. The UE 710 may multiply the conjugate oftimesThe phase impact for the channels between the UE 710 and TRP 715 may be canceled out by precoding the first CSI-RS.

The channel for the second SRS z₂ from the UE 710 on Tx antenna t to TRP 720 (TRP2) on Rx antenna r' at subcarrier k may be formulated as: The termmay represent the phase uncertainty of the Rx antenna r' at TRP 720 (TRP2) . The term may represent the timing offset at the Rx side of TRP 720 (TRP2) . TRP 720 may precode the second CSI-RS by, for example, modulating the second CSI-RS withof normalized z₂. The received second CSI-RS signal may be The termmay represent the UE Rx side gain and phase imbalance at the receive antenna t. The termmay represent Tx side phase uncertainty at TRP 720 (TRP2) . The term may represent the Tx side timing offset at TRP 720 (TRP2) . The termmay represent the downlink channel from transmit antenna r' at TRP 720 to receive antenna t at the UE 710. The UE 710 may multiply the conjugate oftimesThe phase impact for the channels between the UE 710 and TRP 720 may be canceled out by precoding the second CSI-RS.

The calculation ofmay be represented as Note that the phase imbalances andof the UE and the phase of the channel are canceled out. The two parametersand may be estimated using theobservation across multiple subcarriers.

As indicated above, Fig. 7 is provided as an example. Other examples may differ from what is described with respect to Fig. 7.

Fig. 8 is a diagram illustrating example 800 of resource associations, in accordance with the present disclosure.

There may be some expectations for the CSI-RSs and the SRSs. In some aspects, the Tx antenna corresponding to the Tx port of the SRS and the Rx antenna corresponding to the corresponding CSI-RS may be the same. For example, the Tx antenna corresponding to the port/antenna of the first SRS and the Rx antenna corresponding to the first CSI-RS may be the same. The Tx antenna corresponding to the port/antenna of the second SRS and the Rx antenna corresponding to the second CSI-RS may be the same. This may ensure that the phase of the channel is cancelled out.

In some aspects, a CSI-RS resource may be associated with an SRS resource. Such association helps the UE to determine which Rx antenna to use to receive the precoded CSI-RS. For example, if an SRS is transmitted on Tx antenna t, then the UE max expect to receive the precoded CSI-RS on the same antenna so that the phase of the channel can be cancelled out.

In some aspects, the Tx port of SRS (s) for a given pairs of CSI-RSs may be the same. In one example, the first SRS and the second SRS are transmitted on different SRS resources, and the Tx port of the first SRS and the Tx port of the second SRS may be the same. In another example, the first SRS and the second SRS are transmitted on the same single-port SRS resource, which may automatically ensure that the Tx ports of the SRSs for a given pair of CSI-RSs will be the same. This may ensure that the UE’s Tx mismatch is cancelled out. In some aspects, a pairs of CSI-RS resources (CSI-RS resource 802 and CSI-RS resource 804) may be associated with an SRS resource 806. In some aspects, each CSI-RS resource of the pair of CSI-RS resources may be associated with an SRS resource (SRS resource 806 and SRS resource 808) . The SRS resources may be associated with each other.

In some aspects, the Rx port/antenna at the UE 710 for a given pair of CSI-RSs may be the same. For example, the Rx port for the first CSI-RS and the Rx port for the second CSI-RS may be the same. This may ensure that the UE’s Rx mismatch is cancelled out. In some aspects, the CSI-RS resources may be associated with each other.

As indicated above, Fig. 8 is provided as an example. Other examples may differ from what is described with regard to Fig. 8.

Fig. 9 is a diagram illustrating an example 900 of synchronization of multiple TRPs, in accordance with the present disclosure.

In some aspects, as shown by example 900, for more than two TRPs, such as N TRPs, time/phase synchronization among the N TRPs may be jointly synchronized as long as the relative time/phase offset between a pair of TRPs is known for at least N-1 pairs. Two TRPs may be directly connected if a UE participates in synchronization between the two TRPs (e.g., SRS/CSI-RS from/to the UE) .

In some aspects, an assisting UE may be selected such that there is a path from one TRP to another TRP. At most, N-1 UEs may be used. In some aspects, a UE may be an assisting UE for multiple pairs of TRPs. For example, UE2 may be an assisting UE for TRP1 and TRP3 and also an assisting UE for TRP1 and TRP4.

As indicated above, Fig. 9 is provided as an example. Other examples may differ from what is described with regard to Fig. 9.

Fig. 10 is a diagram illustrating example 1000 of resource associations, in accordance with the present disclosure.

In some aspects, when a UE is an assisting UE for multiple pairs of TRPs, the expectations described in connection with Fig. 8 may be applied to any two pairs of TRPs, if a single SRS is transmitted to each TRP. For example, the Tx antenna corresponding to the antenna of an SRS and the Rx antenna corresponding to the corresponding CSI-RS may be the same. In another example, the Tx antennas corresponding to the antenna of the SRS for multiple pairs of CSI-RSs may be the same. In an example, the Rx antennas for multiple pairs of CSI-RSs may be the same. In consideration of these expectations, a CSI-RS resource may be associated with an SRS resource. Multiple pairs of CSI-RSs may be associated with the same antenna of an SRS resource. Example 1000 shows that CSI-RS resource 1002, CSI-RS resource 1004, and CSI-RS resource 1006 may be associated with SRS resource 1008. Two CSI-RS resources among multiple CSI-RS resources may be paired with each other. Example 1000 shows a pair of CSI-RS resources (CSI-RS resource 1002 and CSI-RS resource 1004) associated with each other. Another pair of CSI-RS resources (SI-RS resource 1002 and CSI-RS resource 1006) may be associated with each other. SRS resource 1008 may be associated with SRS resource 1010. SRS resource 1008 may be associated with SRS resource 1012.

In some aspects, for a CSI-RS configuration, a network entity may configure a dedicated CSI-RS resource set (of a set of CSI-RS resources) for time/phase synchronization. The network entity may specify that the dedicated CSI-RSs resources of the CSI-RS resource set are to be used for TRP synchronization. The network entity may also configure a linkage between pairs of CSI-RS resources.

In some aspects, the network entity may configure one of the CSI-RS resources to be an anchor CSI-RS resource. An anchor resource may be a resource that is included in each of multiple pairs of resources. For example, each pair of CSI-RS resources may include the anchor CSI-RS resource and one of the remaining CSI-RS resources other than the anchor CSI-RS resource.

In some aspects, the network entity may configure multiple pairs of CSI-RSs within a CSI-RS resource set. A pair of CSI-RS resources may include a first CSI-RS resource and a second CSI-RS resource in the CSI-RS resource set.

In some aspects, the network entity may configure, in an SRS configuration, a normal SRS or a dedicated SRS resource set for time/phase synchronization. The network entity may specify that the SRS resources of the dedicated SRS resource set are to be used for time/phase synchronization. The network entity may configure an SRS resource in the dedicated SRS resource set as a single-port SRS. The network entity may configure a linkage between pairs of SRS resources. The network entity may configure an SRS resource to be associated with one or more other SRS resources.

For a pair of SRS resources associated with each other, the network entity may configure the first SRS resource of the pair of SRS resources and the second SRS resource of the pair of SRS resources in different SRS resource sets. The network entity may configure the CSI-RS resources that are associated with the SRS resources (that are associated with each other) to be paired together. In this case, the linkage between a pair of CSI-RS resources may not need to be configured.

As indicated above, Fig. 10 is provided as an example. Other examples may differ from what is described with regard to Fig. 10.

Fig. 11 is a diagram illustrating example 1100 of resource associations, in accordance with the present disclosure.

In some aspects, a network entity may configure a CSI-RS resource set to be associated with an SRS resource. As shown by example 1100, each of the CSI-RS resources in the CSI-RS resource set may be associated with the SRS resource. In option 1102, the network entity has configured a CSI-RS resource in the CSI-RS resource set to be an anchor CSI-RS resource (e.g., CSI-RS resource 1) . In option 1104, the network entity has configured which CSI-RS resources are to be paired (e.g., CSI-RS resource 1 and CSI-RS resource 2, CSI-RS resource 1 and CSI-RS resource 3) .

As indicated above, Fig. 11 is provided as an example. Other examples may differ from what is described with regard to Fig. 11.

Fig. 12 is a diagram illustrating example 1200 of resource associations, in accordance with the present disclosure.

In some aspects, a network entity may configure each of the CSI-RS resources to be associated with an SRS resource. Example 1200 shows that the CSI-RS resource of CSI-RS resource set 1202 are each associated with an SRS resource. For example, CSI-RS resource 1 may be associated with SRS resource X1, CSI-RS resource 2 may be associated with SRS resource X2, and CSI-RS resource 3 may be associated with SRS resource X3. In some aspects, different CSI-RS resources may be associated with the same SRS resource.

As shown by example 1200, different CSI-RS resources may be associated with different SRS resources. In some aspects, if different CSI-RS resources are associated with different SRS resources, the SRS resources that are associated with a pair of CSI-RSs may use the same antenna. The network entity may configure SRS resources that are associated with different CSI-RS resources to be configured in different SRS resource sets.

As indicated above, Fig. 12 is provided as an example. Other examples may differ from what is described with regard to Fig. 12.

Fig. 13 is a diagram illustrating example 1300 of resource associations, in accordance with the present disclosure.

In some aspects, a network entity may configure each SRS resource to be associated with one or more CSI-RS resources. Example 1300 shows SRS resources that are each associated with a CSI-RS resource. For example, SRS resource X1 of SRS resource set 1 is associated with CSI-RS resource 1, SRS resource X2 of SRS resource set 2 is associated with CSI-RS resource 2, and SRS resource X3 of SRS resource set 3 is associated with CSI-RS resource 3. If each SRS resource is associated with one CSI-RS resource, if a first SRS resource is associated with a first CSI-RS resource and a second SRS resource is associated with a second CSI-RS resource, and if the first CSI-RS resource is associated with the second CSI-RS resource, then the first SRS resource and the second SRS resource may use the same antenna.

In some aspects, the network entity may configure the SRS resources to be associated with different CSI-RS resources in different SRS resource sets. Example 1300 also shows an SRS resource associated with multiple CSI-RS resources. For example, SRS resource X1 is associated with CSI-RS resources 1-3.

As indicated above, Fig. 13 is provided as an example. Other examples may differ from what is described with regard to Fig. 13.

Fig. 14 is a diagram illustrating example 1400 of resource associations, in accordance with the present disclosure.

Example 1400 shows a CSI-RS resource set 1402 of CSI-RS resources. In some aspects, linkage between the CSI-RS resource may not be configured by a network entity. Example 1400 shows that resource association may still be formed between SRS resources, CSI-RS resources, and other SRS resources. For example, SRS resource X1 (of SRS resource set 1) may be associated with CSI-RS resource 1 and SRS resources X2 and X3, SRS resource X2 (of SRS resource set 2) may be associated with CSI-RS resource 2 and SRS resource X1, and SRS resource X3 (of SRS resource set 3) may be associated with CSI-RS resource 3 and SRS resources X1. Example 1400 shows that SRS resource X1 may be an anchor SRS resource that is a part of each pair or group of associated SRS resources.

As indicated above, Fig. 14 is provided as an example. Other examples may differ from what is described with regard to Fig. 14.

In some aspects, a UE may be triggered to provide a report using CSI-RS and SRS. The report may be a periodic report on the PUCCH, a semi-periodic report on the PUCCH (activated by a MAC control element (MAC CE) or a PUSCH communication) , or an aperiodic report on the PUSCH.

In some aspects, for a periodic report on the PUCCH or semi-periodic report on the PUCCH activated by a MAC CE, the report may be based at least in part on periodic or semi-periodic downlink reference signals (e.g., CSI-RSs) , where the downlink reference signals are linked to one or more periodic or semi-periodic SRSs.

For a semi-periodic report on the PUSCH or an aperiodic report on the PUSCH, the report may be based at least in part on periodic or semi-periodic downlink reference signals that are linked to periodic or semi-periodic downlink reference signals, which that are linked to periodic or semi-periodic SRSs. The report may be based at least in part on aperiodic downlink reference signals that are linked to aperiodic SRSs. For example, the UE may transmit the report based at least in part on one or the following: receiving one or more periodic or semi-persistent downlink reference signals associated with one or more periodic or semi-persistent SRSs, receiving one or more aperiodic downlink reference signals that are associated with one or more aperiodic SRSs, or receiving one or more aperiodic downlink reference signals that are associated with one or more periodic SRSs.

In some aspects, an aperiodic SRS may appear earlier than all aperiodic downlink reference signals, and an aperiodic report may be based at least in part on aperiodic downlink reference signals that are linked to periodic SRSs. In some aspects, the aperiodic report triggering state (e.g., CSI-AperiodicTriggerState) may be configured with an associated SRS based at least in part on a configured linkage to downlink reference signals (or a set of downlink reference signals) , or based at least in part on being linked to a report. An aperiodic SRS may not be triggered by a downlink control information (DCI) field for an SRS request, but by a field for a CSI request. In this case, the CSI request may not only trigger the aperiodic CSI-RS but also trigger the aperiodic SRS associated with the aperiodic CSI-RS. In some aspects, the UE may transmit the report in response to receiving a CSI request in a PDCCH that triggers one or more aperiodic CSI-RSs and one or more associated SRSs.

Fig. 15 is a diagram illustrating an example process 1500 performed, for example, at a UE or an apparatus of a UE, in accordance with the present disclosure. Example process 1500 is an example where the apparatus or the UE (e.g., UE 120, UE 710) performs operations associated with UE-assisted transmit receive.

As shown in Fig. 15, in some aspects, process 1500 may include transmitting a first SRS to a first TRP and a second SRS to a second TRP (block 1510) . For example, the UE (e.g., using transmission component 1704 and/or communication manager 1706, depicted in Fig. 17) may transmit a first SRS to a first TRP and a second SRS to a second TRP, as described above.

As further shown in Fig. 15, in some aspects, process 1500 may include receiving a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS (block 1520) . For example, the UE (e.g., using reception component 1702 and/or communication manager 1706, depicted in Fig. 17) may receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS, as described above. In some aspects, the first CSI-RS is precoded based on the first SRS and the second CSI-RS is precoded based on the second SRS.

As further shown in Fig. 15, in some aspects, process 1500 may include estimating one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS (block 1530) . For example, the UE (e.g., using communication manager 1706, depicted in Fig. 17) may estimate one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS, as described above.

As further shown in Fig. 15, in some aspects, process 1500 may include transmitting a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP (block 1540) . For example, the UE (e.g., using transmission component 1704 and/or communication manager 1706, depicted in Fig. 17) may transmit a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP, as described above.

Process 1500 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, estimating the one or more of the first relative time offset or the first relative phase offset includes calculating a product of the first received CSI-RS and a conjugate of the second received CSI-RS.

In a second aspect, alone or in combination with the first aspect, estimating the one or more of the first relative time offset or the first relative phase offset includes estimating the one or more of the first relative time offset or the first relative phase offset across multiple subcarriers used by the first received CSI-RS and the second received CSI-RS.

In a third aspect, alone or in combination with one or more of the first and second aspects, a first transmit antenna of the UE corresponding to an antenna of the first SRS is a same antenna as a first receive antenna of the UE corresponding to the first CSI-RS, and a second transmit antenna of the UE corresponding to an antenna of the second SRS is a same antenna as a second receive antenna of the UE corresponding to the second CSI-RS.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, transmitting the first SRS and the second SRS includes transmitting the first SRS on a first SRS resource and the second SRS on a second SRS resource, where the first SRS resource and the second SRS resource are different, and a transmit port of the first SRS is the same antenna as a transmit antenna of the second SRS.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, transmitting the first SRS and the second SRS includes transmitting the first SRS and the second SRS on a same single-port SRS resource.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, receiving the first CSI-RS and the second CSI-RS includes receiving the first CSI-RS and the second CSI-RS at a same receive antenna.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the first SRS and the second SRS are a same single-port SRS resource, and a first CSI-RS resource of the first CSI-RS and a second CSI-RS resource of the second CSI-RS are associated with the same single-port SRS resource.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, a first CSI-RS resource of the first CSI-RS and a second CSI-RS resource of the second CSI-RS are associated with an SRS resource of the first SRS and the second SRS.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, a CSI-RS resource for the first CSI-RS is associated with a second CSI-RS resource for the second CSI-RS.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, the first CSI-RS resource is associated with the second CSI-RS resource, and the first SRS resource is associated with the second SRS resource.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, a first CSI-RS resource of the first CSI-RS is associated with a first SRS resource of the first SRS, and a second CSI-RS resource of the second CSI-RS is associated with a second SRS resource of the second SRS.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, a CSI-RS resource for the first CSI-RS is an anchor CSI-RS resource that is included in each of multiple CSI-RS pairs of CSI-RS resources.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, process 1500 includes transmitting a third SRS to a third TRP, receiving a third CSI-RS associated with the third SRS, where the third CSI-RS is precoded based at least in part on the third SRS, estimating one or more of a second relative time offset or a second relative phase offset using the first received CSI-RS and the third received CSI-RS or the second received CSI-RS and the third received CSI-RS, and transmitting a report of the one or more of the second relative time offset or the second relative phase offset to one or more of the first TRP, the second TRP, or the third TRP.

In a fourteenth aspect, alone or in combination with one or more of the first through thirteenth aspects, one or more of a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for the second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.

In a fifteenth aspect, alone or in combination with one or more of the first through fourteenth aspects, one or more of a first SRS resource for the first SRS and a second SRS resource for the second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.

In a sixteenth aspect, alone or in combination with one or more of the first through fifteenth aspects, the report is configured to be a periodic report or a semi-periodic report.

In a seventeenth aspect, alone or in combination with one or more of the first through sixteenth aspects, transmitting the report includes transmitting the report based at least in part on receiving an activation message.

In an eighteenth aspect, alone or in combination with one or more of the first through seventeenth aspects, transmitting the report includes transmitting the report based at least in part on receiving one or more periodic or semi-persistent downlink reference signals that are associated with one or more periodic or semi-persistent SRSs.

In a nineteenth aspect, alone or in combination with one or more of the first through eighteenth aspects, the report is configured to be a semi-persistent report or an aperiodic report, and transmitting the report includes transmitting the report based at least in part on one or the following: receiving one or more periodic or semi-persistent downlink reference signals associated with one or more periodic or semi-persistent SRSs, receiving one or more aperiodic downlink reference signals that are associated with one or more aperiodic SRSs, or receiving one or more aperiodic downlink reference signals that are associated with one or more periodic SRSs.

In a twentieth aspect, alone or in combination with one or more of the first through nineteenth aspects, the report is aperiodic, and transmitting the report includes transmitting the report in response to receiving a CSI request in a PDCCH that triggers one or more aperiodic CSI-RSs and one or more associated SRSs.

Although Fig. 15 shows example blocks of process 1500, in some aspects, process 1500 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 15. Additionally, or alternatively, two or more of the blocks of process 1500 may be performed in parallel.

Fig. 16 is a diagram illustrating an example process 1600 performed, for example, at a first TRP or an apparatus of a first TRP, in accordance with the present disclosure. Example process 1600 is an example where the apparatus or the first TRP (e.g., network node 110, TRP 715, TRP 720) performs operations associated with UE-assisted TRP synchronization.

As shown in Fig. 16, in some aspects, process 1600 may include receiving a first SRS (block 1610) . For example, the first TRP (e.g., using reception component 1802 and/or communication manager 1806, depicted in Fig. 18) may receive a first SRS, as described above.

As further shown in Fig. 16, in some aspects, process 1600 may include transmitting a first CSI-RS associated with the first received SRS (block 1620) . For example, the first TRP (e.g., using transmission component 1804 and/or communication manager 1806, depicted in Fig. 18) may transmit a first CSI-RS associated with the first received SRS, as described above. The first CSI-RS may be precoded based at least in part on the first received SRS.

As further shown in Fig. 16, in some aspects, process 1600 may include receiving a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP (block 1630) . For example, the first TRP (e.g., using reception component 1802 and/or communication manager 1806, depicted in Fig. 18) may receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP, as described above.

As further shown in Fig. 16, in some aspects, process 1600 may include synchronizing one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset (block 1640) . For example, the first TRP (e.g., using communication manager 1806, depicted in Fig. 18) may synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset, as described above.

Process 1600 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, a CSI-RS resource of the first CSI-RS is associated with an SRS resource of the first SRS.

In a second aspect, alone or in combination with the first aspect, process 1600 includes transmitting a configuration that indicates that a CSI-RS resource for the first CSI-RS is an anchor CSI-RS resource that is included in each of multiple CSI-RS pairs of CSI-RS resources.

In a third aspect, alone or in combination with one or more of the first and second aspects, process 1600 includes transmitting a configuration that indicates that a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for a second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process 1600 includes transmitting a configuration that indicates that one or more of a first SRS resource for the first SRS and a second SRS resource for a second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, process 1600 includes transmitting a configuration that indicates that each SRS resource is to be associated with multiple CSI-RS resources.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process 1600 includes transmitting a configuration that indicates that a first SRS resource and a second SRS resource are to use a same antenna, where the first SRS resource is associated with a first CSI-RS resource and the second SRS resource is associated with a second CSI-RS resource, and where the first CSI-RS resource and the second CSI-RS resource are associated with each other.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, process 1600 includes transmitting a configuration that indicates that the report is be a periodic report or a semi-periodic report.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, process 1600 includes transmitting an activation message that activates generation and transmission of the report.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process 1600 includes transmitting a configuration that indicates that a pair of CSI-RS resources includes a first CSI-RS resource and a second CSI-RS resource.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, process 1600 includes transmitting a configuration that indicates that each SRS resource is to be associated with one or more other SRS resources.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, process 1600 includes transmitting a configuration that indicates that a CSI-RS resource set for TRP synchronization is to be associated with an SRS resource.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, process 1600 includes transmitting a configuration that indicates that each CSI-RS resource in a CSI-RS resource set of TRP synchronization is to be associated with an SRS resource.

Although Fig. 16 shows example blocks of process 1600, in some aspects, process 1600 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 16. Additionally, or alternatively, two or more of the blocks of process 1600 may be performed in parallel.

Fig. 17 is a diagram of an example apparatus 1700 for wireless communication, in accordance with the present disclosure. The apparatus 1700 may be a UE, or a UE may include the apparatus 1700. In some aspects, the apparatus 1700 includes a reception component 1702, a transmission component 1704, and/or a communication manager 1706, which may be in communication with one another (for example, via one or more buses and/or one or more other components) . In some aspects, the communication manager 1706 is the communication manager 140 described in connection with Fig. 1. As shown, the apparatus 1700 may communicate with another apparatus 1708, such as a UE or a network node (such as a CU, a DU, an RU, or a base station) , using the reception component 1702 and the transmission component 1704.

In some aspects, the apparatus 1700 may be configured to perform one or more operations described herein in connection with Figs. 1-14. Additionally, or alternatively, the apparatus 1700 may be configured to perform one or more processes described herein, such as process 1500 of Fig. 15. In some aspects, the apparatus 1700 and/or one or more components shown in Fig. 17 may include one or more components of the UE described in connection with Fig. 2. Additionally, or alternatively, one or more components shown in Fig. 17 may be implemented within one or more components described in connection with Fig. 2. Additionally, or alternatively, one or more components of the set of components may be implemented at least in part as software stored in one or more memories. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by one or more controllers or one or more processors to perform the functions or operations of the component.

The reception component 1702 may receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 1708. The reception component 1702 may provide received communications to one or more other components of the apparatus 1700. In some aspects, the reception component 1702 may perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples) , and may provide the processed signals to the one or more other components of the apparatus 1700. In some aspects, the reception component 1702 may include one or more antennas, one or more modems, one or more demodulators, one or more MIMO detectors, one or more receive processors, one or more controllers/processors, one or more memories, or a combination thereof, of the UE described in connection with Fig. 2.

The transmission component 1704 may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 1708. In some aspects, one or more other components of the apparatus 1700 may generate communications and may provide the generated communications to the transmission component 1704 for transmission to the apparatus 1708. In some aspects, the transmission component 1704 may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples) , and may transmit the processed signals to the apparatus 1708. In some aspects, the transmission component 1704 may include one or more antennas, one or more modems, one or more modulators, one or more transmit MIMO processors, one or more transmit processors, one or more controllers/processors, one or more memories, or a combination thereof, of the UE described in connection with Fig. 2. In some aspects, the transmission component 1704 may be co-located with the reception component 1702 in one or more transceivers.

The communication manager 1706 may support operations of the reception component 1702 and/or the transmission component 1704. For example, the communication manager 1706 may receive information associated with configuring reception of communications by the reception component 1702 and/or transmission of communications by the transmission component 1704. Additionally, or alternatively, the communication manager 1706 may generate and/or provide control information to the reception component 1702 and/or the transmission component 1704 to control reception and/or transmission of communications.

The transmission component 1704 may transmit a first SRS to a first TRP and a second SRS to a second TRP. The reception component 1702 may receive a first CSI-RS associated with the first SRS and a second CSI-RS associated with the second SRS, where the first CSI-RS is precoded based on the first SRS and the second CSI-RS is precoded based on the second SRS. The communication manager 1706 may estimate one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS. The transmission component 1704 may transmit a report of the one or more of the first relative time offset or the first relative phase offset to the first TRP and the second TRP.

The transmission component 1704 may transmit a third SRS to a third TRP. The reception component 1702 may receive a third CSI-RS associated with the third SRS.

The communication manager 1706 may estimate one or more of a second relative time offset or a second relative phase offset using the first CSI-RS and the third CSI-RS or the second CSI-RS and the third CSI-RS. The transmission component 1704 may transmit a report of the one or more of the second relative time offset or the second relative phase offset to one or more of the first TRP, the second TRP, or the third TRP.

The number and arrangement of components shown in Fig. 17 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 17. Furthermore, two or more components shown in Fig. 17 may be implemented within a single component, or a single component shown in Fig. 17 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown in Fig. 17 may perform one or more functions described as being performed by another set of components shown in Fig. 17.

Fig. 18 is a diagram of an example apparatus 1800 for wireless communication, in accordance with the present disclosure. The apparatus 1800 may be a first TRP, or a first TRP may include the apparatus 1800. In some aspects, the apparatus 1800 includes a reception component 1802, a transmission component 1804, and/or a communication manager 1806, which may be in communication with one another (for example, via one or more buses and/or one or more other components) . In some aspects, the communication manager 1806 is the communication manager 150 described in connection with Fig. 1. As shown, the apparatus 1800 may communicate with another apparatus 1808, such as a UE or a network node (such as a CU, a DU, an RU, or a base station) , using the reception component 1802 and the transmission component 1804.

In some aspects, the apparatus 1800 may be configured to perform one or more operations described herein in connection with Figs. 1-14. Additionally, or alternatively, the apparatus 1800 may be configured to perform one or more processes described herein, such as process 1600 of Fig. 16. In some aspects, the apparatus 1800 and/or one or more components shown in Fig. 18 may include one or more components of the first TRP described in connection with Fig. 2. Additionally, or alternatively, one or more components shown in Fig. 18 may be implemented within one or more components described in connection with Fig. 2. Additionally, or alternatively, one or more components of the set of components may be implemented at least in part as software stored in one or more memories. For example, a component (or a portion of a component) may be implemented as instructions or code stored in a non-transitory computer-readable medium and executable by one or more controllers or one or more processors to perform the functions or operations of the component.

The reception component 1802 may receive communications, such as reference signals, control information, data communications, or a combination thereof, from the apparatus 1808. The reception component 1802 may provide received communications to one or more other components of the apparatus 1800. In some aspects, the reception component 1802 may perform signal processing on the received communications (such as filtering, amplification, demodulation, analog-to-digital conversion, demultiplexing, deinterleaving, de-mapping, equalization, interference cancellation, or decoding, among other examples) , and may provide the processed signals to the one or more other components of the apparatus 1800. In some aspects, the reception component 1802 may include one or more antennas, one or more modems, one or more demodulators, one or more MIMO detectors, one or more receive processors, one or more controllers/processors, one or more memories, or a combination thereof, of the first TRP described in connection with Fig. 2. In some aspects, the reception component 1802 and/or the transmission component 1804 may include or may be included in a network interface. The network interface may be configured to obtain and/or output signals for the apparatus 1800 via one or more communications links, such as a backhaul link, a midhaul link, and/or a fronthaul link.

The transmission component 1804 may transmit communications, such as reference signals, control information, data communications, or a combination thereof, to the apparatus 1808. In some aspects, one or more other components of the apparatus 1800 may generate communications and may provide the generated communications to the transmission component 1804 for transmission to the apparatus 1808. In some aspects, the transmission component 1804 may perform signal processing on the generated communications (such as filtering, amplification, modulation, digital-to-analog conversion, multiplexing, interleaving, mapping, or encoding, among other examples) , and may transmit the processed signals to the apparatus 1808. In some aspects, the transmission component 1804 may include one or more antennas, one or more modems, one or more modulators, one or more transmit MIMO processors, one or more transmit processors, one or more controllers/processors, one or more memories, or a combination thereof, of the first TRP described in connection with Fig. 2. In some aspects, the transmission component 1804 may be co-located with the reception component 1802 in one or more transceivers.

The communication manager 1806 may support operations of the reception component 1802 and/or the transmission component 1804. For example, the communication manager 1806 may receive information associated with configuring reception of communications by the reception component 1802 and/or transmission of communications by the transmission component 1804. Additionally, or alternatively, the communication manager 1806 may generate and/or provide control information to the reception component 1802 and/or the transmission component 1804 to control reception and/or transmission of communications.

The reception component 1802 may receive a first SRS. The transmission component 1804 may transmit a first CSI-RS associated with the first SRS. The first CSI-RS may be precoded based on the first received SRS. The reception component 1802 may receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP. The transmission component 1804 and the reception component 1802 may synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.

In some aspects, the transmission component 1804 may configure resource associations and port assignments for UE-assisted synchronization.

The number and arrangement of components shown in Fig. 18 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 18. Furthermore, two or more components shown in Fig. 18 may be implemented within a single component, or a single component shown in Fig. 18 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of (one or more) components shown in Fig. 18 may perform one or more functions described as being performed by another set of components shown in Fig. 18.

The following provides an overview of some Aspects of the present disclosure:

Aspect 1: A method of wireless communication performed by a user equipment (UE) , comprising: transmitting a first sounding reference signal (SRS) to a first transmit receive point (TRP) and a second SRS to a second TRP; receiving a first channel state information reference signal (CSI-RS) associated with the first SRS and a second CSI-RS associated with the second SRS, wherein the first CSI-RS is precoded based at least in part on the first SRS and the second CSI-RS is precoded based at least in part on the second SRS; estimating one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS; and transmitting a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.

Aspect 2: The method of Aspect 1, wherein estimating the one or more of the first relative time offset or the first relative phase offset includes calculating a product of the first received CSI-RS and a conjugate of the second received CSI-RS.

Aspect 3: The method of any of Aspects 1-2, wherein estimating the one or more of the first relative time offset or the first relative phase offset includes estimating the one or more of the first relative time offset or the first relative phase offset across multiple subcarriers used by the first received CSI-RS and the second received CSI-RS.

Aspect 4: The method of any of Aspects 1-3, wherein a first transmit antenna of the UE corresponding to an antenna of the first SRS is a same antenna as a first receive antenna of the UE corresponding to the first CSI-RS, and wherein a second transmit antenna of the UE corresponding to an antenna of the second SRS is a same antenna as a second receive antenna of the UE corresponding to the second CSI-RS.

Aspect 5: The method of any of Aspects 1-4, wherein transmitting the first SRS and the second SRS includes transmitting the first SRS on a first SRS resource and the second SRS on a second SRS resource, wherein the first SRS resource and the second SRS resource are different, and wherein a transmit port of the first SRS is a same antenna as a transmit antenna of the second SRS.

Aspect 6: The method of any of Aspects 1-4, wherein transmitting the first SRS and the second SRS includes transmitting the first SRS and the second SRS on a same single-port SRS resource.

Aspect 7: The method of any of Aspects 1-6, wherein receiving the first CSI-RS and the second CSI-RS includes receiving the first CSI-RS and the second CSI-RS at a same receive antenna.

Aspect 8: The method of any of Aspects 1-7, wherein the first SRS and the second SRS are a same single-port SRS resource, and a first CSI-RS resource of the first CSI-RS and a second CSI-RS resource of the second CSI-RS are associated with the same single-port SRS resource.

Aspect 9: The method of any of Aspects 1-7, wherein a first CSI-RS resource of the first CSI-RS and a second CSI-RS resource of the second CSI-RS are associated with an SRS resource of the first SRS and the second SRS.

Aspect 10: The method of any of Aspects 1-9, wherein a first CSI-RS resource of the first CSI-RS is associated with a second CSI-RS resource of the second CSI-RS.

Aspect 11: The method of any of Aspects 1-10, wherein a first SRS resource for the first SRS is associated with a second SRS resource for the second SRS.

Aspect 12: The method of any of Aspects 1-11, wherein a first CSI-RS resource of the first CSI-RS is associated with a first SRS resource of the first SRS, and wherein a second CSI-RS resource of the second CSI-RS is associated with a second SRS resource of the second SRS.

Aspect 13: The method of Aspect 12, wherein a CSI-RS resource for the first CSI-RS is an anchor CSI-RS resource that is included in each of multiple CSI-RS pairs of CSI-RS resources.

Aspect 14: The method of any of Aspects 1-13, further comprising: transmitting a third SRS to a third TRP; receiving a third CSI-RS associated with the third SRS, wherein the third CSI-RS is precoded based at least in part on the third SRS; estimating one or more of a second relative time offset or a second relative phase offset using the first received CSI-RS and the third received CSI-RS or the second received CSI-RS and the third received CSI-RS; and transmitting a report of the one or more of the second relative time offset or the second relative phase offset to one or more of the first TRP, the second TRP, or the third TRP.

Aspect 15: The method of any of Aspects 1-14, wherein one or more of a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for the second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.

Aspect 16: The method of any of Aspects 1-15, wherein one or more of a first SRS resource for the first SRS and a second SRS resource for the second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.

Aspect 17: The method of any of Aspects 1-16, wherein the report is configured to be a periodic report or a semi-periodic report.

Aspect 18: The method of any of Aspects 1-17, wherein transmitting the report includes transmitting the report based at least in part on receiving an activation message.

Aspect 19: The method of any of Aspects 1-18, wherein transmitting the report includes transmitting the report based at least in part on receiving one or more periodic or semi-persistent downlink reference signals that are associated with one or more periodic or semi-persistent SRSs.

Aspect 20: The method of any of Aspects 1-19, wherein the report is configured to be a semi-persistent report or an aperiodic report, and wherein transmitting the report includes transmitting based at least in part on one or the following: receiving one or more periodic or semi-persistent downlink reference signals associated with one or more periodic or semi-persistent SRSs, receiving one or more aperiodic downlink reference signals that are associated with one or more aperiodic SRSs, or receiving one or more aperiodic downlink reference signals that are associated with one or more periodic SRSs.

Aspect 21: The method of any of Aspects 1-20, wherein the report is aperiodic, and wherein transmitting the report includes transmitting the report in response to receiving a CSI request in a physical downlink control channel that triggers one or more aperiodic CSI-RSs and one or more associated SRSs.

Aspect 22: A method of wireless communication performed by a first transmit receive point (TRP) , comprising: receiving a first sounding reference signal (SRS) ; transmitting a first channel state information reference signal (CSI-RS) associated with the first SRS, wherein the first CSI-RS is precoded based at least in part on the first received SRS; and receiving a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP; and synchronizing one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.

Aspect 23: The method of Aspect 22, wherein a CSI-RS resource of the first CSI-RS is associated with an SRS resource of the first SRS.

Aspect 24: The method of any of Aspects 22-23, further comprising transmitting a configuration that indicates that a CSI-RS resource for the first CSI-RS is an anchor CSI-RS resource that is included in each of multiple CSI-RS pairs of CSI-RS resources.

Aspect 25: The method of any of Aspects 22-24, further comprising transmitting a configuration that indicates that a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for a second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.

Aspect 26: The method of any of Aspects 22-25, further comprising transmitting a configuration that indicates that one or more of a first SRS resource for the first SRS and a second SRS resource for a second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.

Aspect 27: The method of any of Aspects 22-26, further comprising transmitting a configuration that indicates that each SRS resource is to be associated with multiple CSI-RS resources.

Aspect 28: The method of any of Aspects 22-27, further comprising transmitting a configuration that indicates that a first SRS resource and a second SRS resource are to use a same antenna.

Aspect 29: The method of any of Aspects 22-28, further comprising transmitting a configuration that indicates that the report is be a periodic report or a semi-periodic report.

Aspect 30: The method of any of Aspects 22-29, further comprising transmitting an activation message that activates generation and transmission of the report.

Aspect 31: The method of any of Aspects 22-30, further comprising transmitting a configuration that indicates that a pair of CSI-RS resources includes a first CSI-RS resource and a second CSI-RS resource.

Aspect 32: The method of any of Aspects 22-31, further comprising transmitting a configuration that indicates that each SRS resource is to be associated with one or more other SRS resources.

Aspect 33: The method of any of Aspects 22-32, further comprising transmitting a configuration that indicates that a CSI-RS resource set for TRP synchronization is to be associated with an SRS resource.

Aspect 34: The method of any of Aspects 22-33, further comprising transmitting a configuration that indicates that each CSI-RS resource in a CSI-RS resource set of TRP synchronization is to be associated with an SRS resource.

Aspect 35: An apparatus for wireless communication at a device, the apparatus comprising one or more processors; one or more memories coupled with the one or more processors; and instructions stored in the one or more memories and executable by the one or more processors to cause the apparatus to perform the method of one or more of Aspects 1-34.

Aspect 36: An apparatus for wireless communication at a device, the apparatus comprising one or more memories and one or more processors coupled to the one or more memories, the one or more processors configured to cause the device to perform the method of one or more of Aspects 1-34.

Aspect 37: An apparatus for wireless communication, the apparatus comprising at least one means for performing the method of one or more of Aspects 1-34.

Aspect 38: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by one or more processors to perform the method of one or more of Aspects 1-34.

Aspect 39: A non-transitory computer-readable medium storing a set of instructions for wireless communication, the set of instructions comprising one or more instructions that, when executed by one or more processors of a device, cause the device to perform the method of one or more of Aspects 1-34.

Aspect 40: A device for wireless communication, the device comprising a processing system that includes one or more processors and one or more memories coupled with the one or more processors, the processing system configured to cause the device to perform the method of one or more of Aspects 1-34.

Aspect 41: An apparatus for wireless communication at a device, the apparatus comprising one or more memories and one or more processors coupled to the one or more memories, the one or more processors individually or collectively configured to cause the device to perform the method of one or more of Aspects 1-34.

The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the aspects to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term “component” is intended to be broadly construed as hardware and/or a combination of hardware and software. “Software” shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, and/or functions, among other examples, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. As used herein, a “processor” is implemented in hardware and/or a combination of hardware and software. It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods are described herein without reference to specific software code, since those skilled in the art will understand that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single-or multi-chip processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some aspects, particular processes and methods may be performed by circuitry that is specific to a given function.

As used herein, “satisfying a threshold” may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, or the like.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. Many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. The disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a + b, a + c, b + c, and a + b + c, as well as any combination with multiples of the same element (e.g., a + a, a + a + a, a + a + b, a + a + c, a + b + b, a + c + c, b + b, b + b + b, b + b + c, c + c, and c + c + c, or any other ordering of a, b, and c) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more. ” Further, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items and may be used interchangeably with “one or more. ” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” or the like are intended to be open-ended terms that do not limit an element that they modify (e.g., an element “having” A may also have B) . Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Also, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and/or, ” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of” ) .

Claims

An apparatus for wireless communication at a user equipment (UE) , comprising:

one or more memories; and

one or more processors, coupled to the one or more memories, individually or collectively configured to cause the UE to:

transmit a first sounding reference signal (SRS) to a first transmit receive point (TRP) and a second SRS to a second TRP;

receive a first channel state information reference signal (CSI-RS) associated with the first SRS and a second CSI-RS associated with the second SRS;

estimate one or more of a first relative time offset or a first relative phase offset using the first received CSI-RS and the second received CSI-RS; and

transmit a report of the one or more of the first relative time offset or the first relative phase offset to one or more of the first TRP or the second TRP.
The apparatus of claim 1, wherein the first CSI-RS is precoded based at least in part on the first SRS and the second CSI-RS is precoded based at least in part on the second SRS.
The apparatus of claim 1, wherein to estimate the one or more of the first relative time offset or the first relative phase offset, the one or more processors are individually or collectively configured to cause the UE to calculate a product of the first received CSI-RS and a conjugate of the second received CSI-RS.
The apparatus of claim 1, wherein to estimate the one or more of the first relative time offset or the first relative phase offset, the one or more processors are individually or collectively configured to cause the UE to estimate the one or more of the first relative time offset or the first relative phase offset across multiple subcarriers used by the first received CSI-RS and the second received CSI-RS.
The apparatus of claim 1, wherein a first transmit antenna of the UE corresponding to an antenna of the first SRS is a same antenna as a first receive antenna of the UE corresponding to the first received CSI-RS, and wherein a second transmit antenna of the UE corresponding to an antenna of the second SRS is a same antenna as a second receive antenna of the UE corresponding to the second received CSI-RS.
The apparatus of claim 1, wherein to transmit the first SRS and the second SRS, the one or more processors are individually or collectively configured to cause the UE to transmit the first SRS on a first SRS resource and the second SRS on a second SRS resource, wherein the first SRS resource and the second SRS resource are different, and wherein a transmit port of the first SRS is a same antenna as a transmit antenna of the second SRS.
The apparatus of claim 1, wherein to transmit the first SRS and the second SRS, the one or more processors are individually or collectively configured to cause the UE to transmit the first SRS and the second SRS on a same single-port SRS resource.
The apparatus of claim 1, wherein to receive the first CSI-RS and the second CSI-RS, the one or more processors are individually or collectively configured to cause the UE to receive the first CSI-RS and the second CSI-RS at a same receive antenna.
The apparatus of claim 1, wherein the first SRS and the second SRS are a same single-port SRS resource, and a first CSI-RS resource of the first CSI-RS and a second CSI-RS resource of the second CSI-RS are associated with the same single-port SRS resource.
The apparatus of claim 1, wherein one or more of:

a CSI-RS resource for the first CSI-RS is associated with a second CSI-RS resource for the second CSI-RS, or

a first SRS resource for the first SRS is associated with a second SRS resource for the second SRS.
The apparatus of claim 1, wherein a first CSI-RS resource of the first CSI-RS is associated with a first SRS resource of the first SRS, and wherein a second CSI-RS resource of the second CSI-RS is associated with a second SRS resource of the second SRS.
The apparatus of claim 1, wherein the one or more processors are individually or collectively configured to cause the UE to:

transmit a third SRS to a third TRP;

receive a third CSI-RS associated with the third SRS, wherein the third CSI-RS is precoded based at least in part on the third SRS;

estimate one or more of a second relative time offset or a second relative phase offset using the first received CSI-RS and the third received CSI-RS or the second received CSI-RS and the third received CSI-RS; and

transmit a report of the one or more of the second relative time offset or the second relative phase offset to one or more of the first TRP, the second TRP, or the third TRP.
The apparatus of claim 1, wherein one or more of a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for the second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.
The apparatus of claim 1, wherein one or more of a first SRS resource for the first SRS and a second SRS resource for the second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.
The apparatus of claim 1, wherein to transmit the report, the one or more processors are individually or collectively configured to cause the UE to transmit the report based at least in part on receiving an activation message.
The apparatus of claim 1, wherein to transmit the report, the one or more processors are individually or collectively configured to cause the UE to transmit the report based at least in part on receiving one or more periodic or semi-persistent downlink reference signals that are associated with one or more periodic or semi-persistent SRSs.
The apparatus of claim 1, wherein the report is configured to be a semi-persistent report or an aperiodic report, and wherein to transmit the report, the one or more processors are individually or collectively configured to cause the UE to transmit the report based at least in part on one or the following:

receiving one or more periodic or semi-persistent downlink reference signals associated with one or more periodic or semi-persistent SRSs,

receiving one or more aperiodic downlink reference signals that are associated with one or more aperiodic SRSs, or

receiving one or more aperiodic downlink reference signals that are associated with one or more periodic SRSs.
The apparatus of claim 1, wherein the report is aperiodic, and wherein to transmit the report, the one or more processors are individually or collectively configured to cause the UE to transmit the report in response to receiving a CSI request in a physical downlink control channel that triggers one or more aperiodic CSI-RSs and one or more associated SRSs.
An apparatus for wireless communication at a first transmit receive point (TRP) , comprising:

one or more memories; and

one or more processors, coupled to the one or more memories, individually or collectively configured to cause the first TRP to:

receive a first sounding reference signal (SRS) ;

transmit a first channel state information reference signal (CSI-RS) associated with the first SRS, wherein the first CSI-RS is precoded based at least in part on the first received SRS; and

receive a report of one or more of a relative time offset or a relative phase offset between the first TRP and a second TRP; and

synchronize one or more of a time or a phase with the second TRP using the one or more of the relative time offset or the relative phase offset.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that a CSI-RS resource for the first CSI-RS is an anchor CSI-RS resource that is included in each of multiple CSI-RS pairs of CSI-RS resources.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that a first CSI-RS resource for the first CSI-RS and a second CSI-RS resource for a second CSI-RS are part of a CSI-RS resource set that is configured to be used for TRP synchronization.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that a pair of CSI-RS resources includes a first CSI-RS resource and a second CSI-RS resource.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that one or more of a first SRS resource for the first SRS and a second SRS resource for a second SRS are part of an SRS resource set that is configured to be used for TRP synchronization.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that each SRS resource is to be associated with one or more other SRS resources.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that a CSI-RS resource set for TRP synchronization is to be associated with an SRS resource.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that each CSI-RS resource in a CSI-RS resource set of TRP synchronization is to be associated with an SRS resource.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that each SRS resource is to be associated with multiple CSI-RS resources.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that a first SRS resource and a second SRS resource are to use a same antenna, wherein the first SRS resource is associated with a first CSI-RS resource and the second SRS resource is associated with a second CSI-RS resource, and wherein the first CSI-RS resource and the second CSI-RS resource are associated with each other.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit a configuration that indicates that the report is be a periodic report or a semi-periodic report.
The apparatus of claim 19, wherein the one or more processors are individually or collectively configured to cause the first TRP to transmit an activation message that activates generation and transmission of the report.