WO2022046490A1

WO2022046490A1 - Techniques for periodic reference signal switching in wireless communications

Info

Publication number: WO2022046490A1
Application number: PCT/US2021/046533
Authority: WO
Inventors: Muhammad Sayed Khairy Abdelghaffar; Alexandros MANOLAKOS
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2020-08-24
Filing date: 2021-08-18
Publication date: 2022-03-03
Anticipated expiration: 2023-02-24

Abstract

Aspects described herein relate to receiving multiple downlink reference signals transmitted by a network via multiple transmission/reception points (TRPs) and select, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which an uplink signal is transmitted or modulated. The indication can be used in processing the uplink signal or the downlink reference signal can be used in beam selection.

Description

TECHNIQUES FOR PERIODIC REFERENCE SIGNAL SWITCHING IN WIRELESS COMMUNICATIONS

Claim of Priority

[0001] The present Application for Patent claims priority to Greek Patent Application No. 20200100507, entitled “TECHNIQUES FOR PERIODIC REFERENCE SIGNAL SWITCHING IN WIRELESS COMMUNICATIONS” filed August 24, 2020, which is assigned to the assignee hereof and hereby expressly incorporated by reference herein for all purposes.

BACKGROUND

[0002] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to transmitting and processing reference signals from multiple transmission/reception points (TRP).

[0003] Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems.

[0004] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. For example, a fifth generation (5G) wireless communications technology (which can be referred to as 5G new radio (5G NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, 5G communications technology can include: enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with certain specifications for latency and reliability; and massive machine type communications, which can allow a very large number of connected devices and transmission of a relatively low volume of non-delay-sensitive information.

[0005] Some applications include high-speed train (HST) scenarios where a network can use multiple TRPs to transmit signals to user equipment (UE) aboard a HST in a single frequency network (SFN). As the HST passes among coverage areas provided by multiple TRPs, the UE can receive downlink signals from, and/or transmit uplink signals to, different ones of the multiple TRPs in the SFN for communicating in a wireless network.

SUMMARY

[0006] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0007] According to an aspect, an apparatus for wireless communication is provided that includes a transceiver, a memory configured to store instructions, and one or more processors communicatively coupled with the memory and the transceiver. The one or more processors are configured to execute the instructions to cause the apparatus to receive multiple downlink reference signals transmitted by a network via multiple transmission/reception points (TRPs), select, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which to transmit an uplink signal, and transmit, to the network via at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal.

[0008] In another aspect, an apparatus for wireless communication is provided that includes a transceiver, a memory configured to store instructions, and one or more processors communicatively coupled with the memory and the transceiver. The one or more processors are configured to execute the instructions to cause the apparatus to transmit, to a user equipment (UE), multiple downlink reference signals using multiple TRPs, and receive, from the UE and based on an indication of the downlink reference signal selected from the multiple downlink reference signals, the uplink signal. [0009] In another aspect, a method of wireless communication is provided. The method includes receiving multiple downlink reference signals transmitted by a network via multiple TRPs, selecting, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which to transmit an uplink signal, and transmitting, to the network via at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal.

[0010] According to another aspect, a method of wireless communication is provided. The method includes transmitting, to a UE, multiple downlink reference signals using multiple TRPs, and receiving, from the UE and based on an indication of the downlink reference signal selected from the multiple downlink reference signals, the uplink signal. [0011] In a further example, an apparatus for wireless communication is provided that includes a transceiver, a memory configured to store instructions, and one or more processors communicatively coupled with the transceiver and the memory. The one or more processors are configured to execute the instructions to perform the operations of methods described herein. In another aspect, an apparatus for wireless communication is provided that includes means for performing the operations of methods described herein. In yet another aspect, a computer-readable medium is provided including code executable by one or more processors to perform the operations of methods described herein.

[0012] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The disclosed aspects will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements, and in which:

[0014] FIG. 1 illustrates an example of a wireless communication system, in accordance with various aspects of the present disclosure; [0015] FIG. 2 is a block diagram illustrating an example of a UE, in accordance with various aspects of the present disclosure;

[0016] FIG. 3 is a block diagram illustrating an example of a base station, in accordance with various aspects of the present disclosure;

[0017] FIG. 4 is a flow chart illustrating an example of a method for transmitting an indication of a selected downlink reference signal, in accordance with various aspects of the present disclosure;

[0018] FIG. 5 is a flow chart illustrating an example of a method for receiving an indication of a selected downlink reference signal, in accordance with various aspects of the present disclosure; and

[0019] FIG. 6 is a block diagram illustrating an example of a MIMO communication system including a base station and a UE, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

[0020] Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such aspect(s) may be practiced without these specific details.

[0021] The described features generally relate to determining one of multiple reference signals received from multiple transmission/reception points (TRPs) based on which to transmit an uplink signal to at least one of the TRPs. A user equipment (UE) communicating in a wireless network can receive multiple reference signals from multiple TRPs in a single frequency network (SFN) in a similar time period. For example, the UE may receive the multiple reference signals in the similar time period as the TRPs can be used to transmit the same or similar communications from the wireless network. For example, in a high speed train (HST) scenario, a UE aboard a HST can move in and out of coverage of various TRPs, and can receive signals from the various TRPs, which may include receiving multiple signals from multiple TRPs, where the multiple signals may at least partially overlap in time. The signals may include downlink channels, such as physical downlink control channel (PDCCH), physical downlink shared channel (PDSCH), etc. In an example, multiple quasi -colocation (QCL) assumptions (e.g., transmission configuration indicator (TCI) states) can be configured for demodulation reference signals of PDSCH and PDCCH. For example, the UE can use the indicated QCL reference signal resources (e.g., channel state information reference signal (CSI-RS) or tracking reference signal (TRS), or synchronization signal block (SSB), etc.) to know or estimate the Doppler shift of each TRP and/or to determine a receive (Rx) beam to use in receiving signals from each of the TRPs.

[0022] In addition, for example, the downlink signals from each TRP can be precompensated to reduce Doppler spectrum of the downlink signals to improve downlink performance. For example, the network can perform the pre-compensation based on an uplink signal received from the UE, such as a sounding reference signal (SRS). Where multiple TRPs are transmitting the multiple downlink signals, however, the network can improve this pre-compensation where the network knows based on which downlink signal the UE is transmitting or modulating the uplink signal. As such, aspects described herein relate to provisioning the information of the downlink reference signal based on which the UE is to transmit the uplink signal to the network that controls the TRPs. In one example, the UE can transmit an indicator to the network indicating which downlink reference signal the UE uses to transmit or modulate the uplink signal. In another example, the UE can use a SRS base sequence to indicate the downlink reference signal. In addition, the UE may select which downlink reference signal to use based on various considerations, such as signal quality or strength, a closest TRP, a Doppler shift sign and/or value, etc.

[0023] In additional examples, the UE can switch downlink reference signals used to transmit or modulate the SRS based on a timer. In an example, the network can configure the timer value to facilitate timely switching of the reference signal (e.g., based on speed of the UE, distance between the TRPs, etc.). Moreover, the UE can also determine a Rx beam to use in receiving communications from the TRPs based at least in part on the downlink reference signal selected for transmitting or modulating the uplink signal. In any case, selecting and indicating the downlink reference signal used to transmit or modulate the uplink signal in this regard can allow for more efficient and improved precompensating of signals transmitted by the TRPs where multiple TRPs are transmitting to the UE.

[0024] The described features will be presented in more detail below with reference to FIGS. 1-6. [0025] As used in this application, the terms “component,” “module,” “system” and the like are intended to include a computer-related entity, such as but not limited to hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components can communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets, such as data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal.

[0026] Techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and “network” may often be used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and A are commonly referred to as CDMA2000 IX, IX, etc. IS-856 (TIA- 856) is commonly referred to as CDMA2000 IxEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3 GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E- UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3 GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an LTE/LTE-A system for purposes of example, and LTE terminology is used in much of the description below, although the techniques are applicable beyond LTE/LTE-A applications (e.g., to fifth generation (5G) new radio (NR) networks or other next generation communication systems).

[0027] The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in other examples.

[0028] Various aspects or features will be presented in terms of systems that can include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems can include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. A combination of these approaches can also be used.

[0029] FIG. l is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN)) can include base stations 102, UEs 104, an Evolved Packet Core (EPC) 160, and/or a 5G Core (5GC) 190. The base stations 102 may include macro cells (high power cellular base station) and/or small cells (low power cellular base station). The macro cells can include base stations. The small cells can include femtocells, picocells, and microcells. In an example, the base stations 102 may also include gNBs 180, as described further herein. In one example, some nodes of the wireless communication system may have a modem 240 and communicating component 242 for determining one of multiple downlink reference signals based on which to transmit or modulate an uplink signal, in accordance with aspects described herein. In addition, some nodes may have a modem 340 and configuring component 342 for configuring multiple downlink reference signals for transmitting to a UE 104, in accordance with aspects described herein. Though a UE 104 is shown as having the modem 240 and communicating component 242 and abase station 102/gNB 180 is shown as having the modem 340 and configuring component 342, this is one illustrative example, and substantially any node or type of node may include a modem 240 and communicating component 242 and/or a modem 340 and configuring component 342 for providing corresponding functionalities described herein.

[0030] The base stations 102 configured for 4G LTE (which can collectively be referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC 160 through backhaul links 132 (e.g., using an SI interface). The base stations 102 configured for 5G NR (which can collectively be referred to as Next Generation RAN (NG-RAN)) may interface with 5GC 190 through backhaul links 184. In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160 or 5GC 190) with each other over backhaul links 134 (e.g., using an X2 interface). The backhaul links 134 may be wired or wireless.

[0031] The base stations 102 may wirelessly communicate with one or more UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102' may have a coverage area 110' that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells may be referred to as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group, which can be referred to as a closed subscriber group (CSG). The communication links 120 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 / UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (e.g., for x component carriers) used for transmission in the DL and/or the UL direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell).

[0032] In another example, certain UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. The D2D communication link 158 may use the DL/UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0033] The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 / AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

[0034] The small cell 102' may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102' may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the WiFi AP 150. The small cell 102', employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. [0035] A base station 102, whether a small cell 102' or a large cell (e.g., macro base station), may include an eNB, gNodeB (gNB), or other type of base station. Some base stations, such as gNB 180 may operate in a traditional sub 6 GHz spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies in communication with the UE 104. When the gNB 180 operates in mmW or near mmW frequencies, the gNB 180 may be referred to as an mmW base station. Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in the band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW / near mmW radio frequency band has extremely high path loss and a short range. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for the extremely high path loss and short range. A base station 102 referred to herein can include a gNB 180.

[0036] The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

[0037] The 5GC 190 may include a Access and Mobility Management Function (AMF) 192, other AMFs 193, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 may be in communication with a Unified Data Management (UDM) 196. The AMF 192 can be a control node that processes the signaling between the UEs 104 and the 5GC 190. Generally, the AMF 192 can provide QoS flow and session management. User Internet protocol (IP) packets (e.g., from one or more UEs 104) can be transferred through the UPF 195. The UPF 195 can provide UE IP address allocation for one or more UEs, as well as other functions. The UPF 195 is connected to the IP Services 197. The IP Services 197 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services.

[0038] The base station may also be referred to as a gNB, Node B, evolved Node B (eNB), an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit reception point (TRP), or some other suitable terminology. The base station 102 provides an access point to the EPC 160 or 5GC 190 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor/actuator, a display, or any other similar functioning device. Some of the UEs 104 may be referred to as loT devices (e.g., parking meter, gas pump, toaster, vehicles, heart monitor, etc.). loT UEs may include machine type communication (MTC)/enhanced MTC (eMTC, also referred to as category (CAT)-M, Cat Ml) UEs, NB-IoT (also referred to as CAT NB1) UEs, as well as other types of UEs. In the present disclosure, eMTC and NB-IoT may refer to future technologies that may evolve from or may be based on these technologies. For example, eMTC may include FeMTC (further eMTC), eFeMTC (enhanced further eMTC), mMTC (massive MTC), etc., and NB-IoT may include eNB- loT (enhanced NB-IoT), FeNB-IoT (further enhanced NB-IoT), etc. The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

[0039] In aspects of the wireless communication system 100, a base station 102 may also include one or more remotely located TRPs 140, 142, which may be wired or wirelessly coupled with the base station 102 for transmitting/receiving associated signaling from/to the base station 102 at a different location. The TRPs 140, 142 may operate based on a SFN to transmit signals in the same frequency range. In an example, TRPs 140, 142 may be remote radio heads (RRHs), relays, etc. configured to facilitate communications between one or more UEs, or other devices, and base station 102. In another example, TRPs 140, 142 may include one or more small cells in communication with core network 160/190 to facilitate wireless communications between the core network 160/190 and one or more UEs. In a specific example, the TRPs 140, 142 may be positioned in an HST system to allow UEs 104 aboard a HST 144 to communicate with core network 160/190 using the TRPs 140, 142 (e.g., as RRHs or relays to base station 102 or otherwise).

[0040] In an example, communicating component 242 can receive multiple RSs from multiple TRPs 140, 142 in a SFN. For example, communicating component 242 may receive the multiple RSs at a given point in time or over similar or overlapping time periods, etc., such that the multiple RSs may be concurrently received. Communicating component 242 can select one of the multiple RSs received from the multiple TRPs 140, 142 to use in transmitting an uplink signal to one or more of the TRPs 140, 142. In one example, communicating component 242 can also indicate the selected one of the multiple RSs to at least one of the TRPs 104, 142 for providing to the base station 102 or network component to allow for processing the uplink signal based on the one of the multiple RSs. For example, processing of the uplink signal may include determining a Doppler shift associated with the uplink signal, and/or pre-compensating subsequent downlink signals to compensate for the Doppler shift. In another example, communicating component 242 can determine a receive beam for receiving signals from the TRP(s) 140, 142, and/or a transmit beam for transmitting signals to the TRP(s) 140, 142, based on the selected downlink reference signal.

[0041] Turning now to FIGS. 2-6, aspects are depicted with reference to one or more components and one or more methods that may perform the actions or operations described herein, where aspects in dashed line may be optional. Although the operations described below in FIGS. 4-5 are presented in a particular order and/or as being performed by an example component, it should be understood that the ordering of the actions and the components performing the actions may be varied, depending on the implementation. Moreover, it should be understood that the following actions, functions, and/or described components may be performed by a specially programmed processor, a processor executing specially programmed software or computer-readable media, or by any other combination of a hardware component and/or a software component capable of performing the described actions or functions.

[0042] Referring to FIG. 2, one example of an implementation of UE 104 may include a variety of components, some of which have already been described above and are described further herein, including components such as one or more processors 212 and memory 216 and transceiver 202 in communication via one or more buses 244, which may operate in conjunction with modem 240 and/or communicating component 242 for determining one of multiple downlink reference signals based on which to transmit or modulate an uplink signal, in accordance with aspects described herein. Moreover, the UE 104 can communicate with a base station 102 via communication links 120 (e.g., to access a network, such as a EPC 160, 5GC 190, etc.). Additionally, as described, the base station 102 can be connected to one or more TRPs, such as TRPs 140, 142, which may be a RRH, relay, etc. used to forward signals transmitted by the base station 102 to one or more UEs 104 and/or forward signals transmitted by the one or more UEs 104 to the base station 102. In one example, the base station 102 can provide the one or more TRPs 140, 142 to enable communications in a HST scenario.

[0043] In an aspect, the one or more processors 212 can include a modem 240 and/or can be part of the modem 240 that uses one or more modem processors. Thus, the various functions related to communicating component 242 may be included in modem 240 and/or processors 212 and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors 212 may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver 202. In other aspects, some of the features of the one or more processors 212 and/or modem 240 associated with communicating component 242 may be performed by transceiver 202.

[0044] Also, memory 216 may be configured to store data used herein and/or local versions of applications 275 or communicating component 242 and/or one or more of its subcomponents being executed by at least one processor 212. Memory 216 can include any type of computer-readable medium usable by a computer or at least one processor 212, such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory 216 may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining communicating component 242 and/or one or more of its subcomponents, and/or data associated therewith, when UE 104 is operating at least one processor 212 to execute communicating component 242 and/or one or more of its subcomponents.

[0045] Transceiver 202 may include at least one receiver 206 and at least one transmitter 208. Receiver 206 may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). Receiver 206 may be, for example, a radio frequency (RF) receiver. In an aspect, receiver 206 may receive signals transmitted by at least one base station 102. Additionally, receiver 206 may process such received signals, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, signal- to-noise ratio (SNR), reference signal received power (RSRP), received signal strength indicator (RSSI), etc. Transmitter 208 may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). A suitable example of transmitter 208 may including, but is not limited to, an RF transmitter.

[0046] Moreover, in an aspect, UE 104 may include RF front end 288, which may operate in communication with one or more antennas 265 and transceiver 202 for receiving and transmitting radio transmissions, for example, wireless communications transmitted by at least one base station 102 or wireless transmissions transmitted by UE 104. RF front end 288 may be connected to one or more antennas 265 and can include one or more low- noise amplifiers (LNAs) 290, one or more switches 292, one or more power amplifiers (PAs) 298, and one or more filters 296 for transmitting and receiving RF signals. [0047] In an aspect, LNA 290 can amplify a received signal at a desired output level. In an aspect, each LNA 290 may have a specified minimum and maximum gain values. In an aspect, RF front end 288 may use one or more switches 292 to select a particular LNA 290 and its specified gain value based on a desired gain value for a particular application. [0048] Further, for example, one or more PA(s) 298 may be used by RF front end 288 to amplify a signal for an RF output at a desired output power level. In an aspect, each PA 298 may have specified minimum and maximum gain values. In an aspect, RF front end 288 may use one or more switches 292 to select a particular PA 298 and its specified gain value based on a desired gain value for a particular application.

[0049] Also, for example, one or more filters 296 can be used by RF front end 288 to filter a received signal to obtain an input RF signal. Similarly, in an aspect, for example, a respective filter 296 can be used to filter an output from a respective PA 298 to produce an output signal for transmission. In an aspect, each filter 296 can be connected to a specific LNA 290 and/or PA 298. In an aspect, RF front end 288 can use one or more switches 292 to select a transmit or receive path using a specified filter 296, LNA 290, and/or PA 298, based on a configuration as specified by transceiver 202 and/or processor 212.

[0050] As such, transceiver 202 may be configured to transmit and receive wireless signals through one or more antennas 265 via RF front end 288. In an aspect, transceiver may be tuned to operate at specified frequencies such that UE 104 can communicate with, for example, one or more base stations 102 or one or more cells associated with one or more base stations 102. In an aspect, for example, modem 240 can configure transceiver 202 to operate at a specified frequency and power level based on the UE configuration of the UE 104 and the communication protocol used by modem 240.

[0051] In an aspect, modem 240 can be a multiband-multimode modem, which can process digital data and communicate with transceiver 202 such that the digital data is sent and received using transceiver 202. In an aspect, modem 240 can be multiband and be configured to support multiple frequency bands for a specific communications protocol. In an aspect, modem 240 can be multimode and be configured to support multiple operating networks and communications protocols. In an aspect, modem 240 can control one or more components of UE 104 (e.g., RF front end 288, transceiver 202) to enable transmission and/or reception of signals from the network based on a specified modem configuration. In an aspect, the modem configuration can be based on the mode of the modem and the frequency band in use. In another aspect, the modem configuration can be based on UE configuration information associated with UE 104 as provided by the network during cell selection and/or cell reselection.

[0052] In an aspect, communicating component 242 can optionally include a RS determining component 252 for receiving or otherwise determining multiple RSs received from multiple TRPs 140, 142, and/or an RS indicating component 254 for indicating one of the multiple RSs based on which an uplink signal is transmitted and/or modulated, in accordance with aspects described herein.

[0053] In an aspect, the processor(s) 212 may correspond to one or more of the processors described in connection with the UE in FIG. 6. Similarly, the memory 216 may correspond to the memory described in connection with the UE in FIG. 6.

[0054] Referring to FIG. 3, one example of an implementation of base station 102 (e.g., a base station 102 and/or gNB 180, as described above) may include a variety of components, some of which have already been described above, but including components such as one or more processors 312 and memory 316 and transceiver 302 in communication via one or more buses 344, which may operate in conjunction with modem 340 and configuring component 342 for configuring multiple downlink reference signals for transmitting to a UE 104, in accordance with aspects described herein. Additionally, as described, the base station 102 can be connected to one or more TRPs 140, 142, which may be a RRH, relay, etc. used to forward signals transmitted by the base station 102 to one or more UEs 104 and/or forward signals transmitted by the one or more UEs 104 to the base station 102.

[0055] The transceiver 302, receiver 306, transmitter 308, one or more processors 312, memory 316, applications 375, buses 344, RF front end 388, LNAs 390, switches 392, filters 396, PAs 398, and one or more antennas 365 may be the same as or similar to the corresponding components of UE 104, as described above, but configured or otherwise programmed for base station operations as opposed to UE operations.

[0056] In an aspect, configuring component 342 can optionally include a RS indication receiving component 352 for receiving an indication of one of multiple RSs based on which an uplink signal is transmitted and/or modulation, and/or an uplink signal processing component 354 for processing an uplink signal received from the UE 104 based on which of the multiple RSs the uplink signal is transmitted or modulated, in accordance with aspects described herein. [0057] In an aspect, the processor(s) 312 may correspond to one or more of the processors described in connection with the base station in FIG. 6. Similarly, the memory 316 may correspond to the memory described in connection with the base station in FIG. 6.

[0058] FIG. 4 illustrates a flow chart of an example of a method 400 for selecting one of multiple reference signals based on which to transmit an uplink signal, in accordance with aspects described herein. In an example, a UE 104 can perform the functions described in method 400 using one or more of the components described in FIGS. 1 and 2.

[0059] In method 400, at Block 402, multiple downlink reference signals transmitted by a network via multiple TRPs can be received. In an aspect, RS determining component 252, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can receive the multiple downlink reference signals transmitted by the network via the multiple TRPs. For example, each TRP may configure reference signal transmission to the UE 104, which may be via radio resource control (RRC) configuration, broadcast system information, etc. In an example, each TRP may configure CSI-RS transmission, TRS transmission, SSB transmission, etc. RS determining component 252 can receive the configurations from multiple TRPs and can accordingly determine resources (e.g., time and/or frequency resources) over which to receive the downlink reference signals from the TRPs. In an example, the TRPs may transmit the same or similar or different downlink reference signals. For example, the TRPs may transmit the reference signals in the same or similar or different time and/or frequency resources. The UE 104 can be configured to receive the downlink reference signals (e.g., concurrently or otherwise) from the multiple TRPs. In an aspect, a base station 102 or other network component can control the TRPs (e.g., TRPs 140, 142) to transmit the downlink reference signals and/or to transmit the corresponding downlink reference signal configurations.

[0060] In one example, the multiple TRPs can each configure the UE 104 with SRS resources that are associated with the downlink reference signal (e.g., with the CSI- RS/TRS) for the purpose of uplink center frequency modulation (e.g. QCL-Type A that has Doppler shift/spread), and/or uplink beam determination (e.g., QCL-Type D). Accordingly, for example, RS determining component 252 can receive the configuration and can determine SRS resources for transmitting a SRS corresponding to the downlink reference signal for the purpose(s) of uplink center frequency modulation, and/or uplink beam determination. [0061] In method 400, at Block 404, a downlink reference signal, based on which to transmit an uplink signal, can be selected from the multiple downlink reference signals. In an aspect, RS determining component 252, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can select the downlink reference signal from the multiple downlink reference signals based on which to transmit the uplink signal. For example, selecting one of the multiple downlink reference signals and having the UE 104 and TRP 140, 142 or base station 102 know of the selection may allow for improved signal pre-compensation, beam selection, etc. In one example, RS determining component 252 can select the downlink reference signal from the multiple downlink reference signals based on an indication of the downlink reference signal, where the indication may be received from the network (e.g., prior to selection) or transmitted to the network by the UE 104 (e.g., following selection). For example, RS determining component 252 can select the downlink reference signal based on various considerations, which may include a signal power or quality associated with the multiple downlink reference signals, determining which of the multiple downlink reference signals corresponds to a closest TRP, determining a Doppler shift sign and/or value of the multiple downlink reference signals, receiving an indication of which downlink reference signal to use (which may also be specified in conjunction with ta timer for switching downlink reference signals, as described further herein), etc.

[0062] For example, RS determining component 252 can measure signal power or quality (e.g., a reference signal received power (RSRP), reference signal received quality (RSRQ), received signal strength indicator (RSSI), signal-to-noise ratio (SNR), signal-to- interference-and-noise ratio (SINR), etc.) of the downlink reference signals and can select the downlink reference signal having the highest or most desirable power or quality metric. In another example, RS determining component 252 can determine which of the multiple TRPs, to which the downlink reference signals relate, is closest to the UE 104 (e.g., based on a delay of a line-of-sight (LOS) component, such as a first arrival path (FAP) delay or time of arrival of the first arrival path - e.g., the time at which the first signal from one of the multiple TRPs arrives or is received at the UE 104), and can select the downlink reference signal corresponding to the closest TRP. In yet another example, RS determining component 252 can determine the Doppler shift sign and value of each of the multiple downlink reference signals and can select the downlink reference signal with the Doppler shift sign and value which may benefit most from pre-compensation. [0063] In yet another example, in method 400, optionally at Block 406, a configuration indicating a timer value for determining to switch among multiple downlink reference signals can be received. In an aspect, RS determining component 252, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can receive the configuration indicating the timer value for determining to switch among the multiple downlink reference signals. RS determining component 252, in an example, can accordingly initialize a timer based on the timer value at the time of switching to a certain reference signal, and after expiration of the timer, can select a next downlink reference signal. The pattern of selection may also be indicated in the configuration.

[0064] In an example, the configuration may indicate the multiple downlink reference signals from which to select the downlink reference signal in a given time period and/or based on expiration of the timer. In as specific example, the configuration may indicate the multiple downlink reference signals based on an identifier thereof, time and/or frequency resources over which the multiple downlink reference signals are transmitted by respective TRPs, a beam used by the respective TRPs to transmit the multiple downlink reference signals, etc.

[0065] For example, for a UE 104 traveling in a known direction (e.g., via a HST), the base station 102 or other network component can know which TRPs the UE 104 is within coverage of (or which TRPs are providing the most desirable coverage for the UE 104) at a given point in time (e.g., a current or future time). Thus, for example, the base station 102 or other network component can accordingly set the timer to facilitate the UE 104 selecting an appropriate downlink reference signal from one of the multiple TRPs along the way.

[0066] For example, for the UE moving inside HST, the time instances where it switches the downlink reference signal can be deterministic based on the UE speed and the distance between the TRPs. In this regard, the network can configure N periodic downlink reference signals and a timer. When the timer expires, the UE can switch to the next configured downlink reference signal in the list, such to transmit or modulate uplink signals based on this next configured downlink reference signal.

[0067] In method 400, optionally at Block 408, an indication of a downlink reference signal can be transmitted, to the network via at least one of the multiple TRPs. In an aspect, RS indicating component 254, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can transmit, to the network via at least one of the multiple TRPs, the indication of the downlink reference signal that is selected. This can allow the network to process an uplink signal sent by the UE 104 based on the downlink reference signal, as described above and further herein.

[0068] In an example, in transmitting the indication at Block 408, optionally at Block 410, the indication can be transmitted in a media access control (MAC)-control element (CE). In an aspect, RS indicating component 254, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can transmit the indication in the MAC-CE to the network via the one or more TRPs. For example, RS indicating component 254 can generate the MAC-CE to indicate the CSI-RS resource indicator of the selected downlink reference signal (e.g., where the downlink reference signal is a CSI-RS or TRS), or a SSB index of the selected downlink reference signal (e.g., where the downlink reference signal is a SSB), etc., so the network can identify the selected downlink reference signal. In another example, RS indicating component 254 can generate the MAC-CE to indicate a signal metric value of the downlink reference signal. In one example, the signal metric may include the Doppler shift of the downlink reference signal as experienced at the UE 104. In an example, the network can utilize the signal metric in pre-compensating or otherwise adjusting subsequent downlink signals.

[0069] In another example, in transmitting the indication at Block 408, optionally at Block 412, a base sequence of a SRS can be selected to transmit the indication. In an aspect, RS indicating component 254, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can select the base sequence of the SRS to transmit the indication. For example, different SRS base sequences can correspond to different downlink reference signals, and can be used to indicate the selected downlink reference signal when the SRS is transmitted (e.g., at Block 416). In this example, optionally at Block 414, a configuration indicating associations between the downlink reference signals and the SRS base sequences can be received. In an aspect, RS indicating component 254, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, communicating component 242, etc., can receive (e.g., from the network via the one or more TRPs 140, 142) the configuration indicating associations between the downlink reference signals (e.g., an index of the downlink reference signals or an associated TRP) and a SRS base sequence. RS indicating component 254, in this example, can accordingly select, from the configuration, the SRS base sequence that corresponds to the selected downlink reference signal in generating or transmitting the SRS to indicate the selected downlink reference signal.

[0070] For example, the network can configure the SRS resources, as described above (e.g., for each TRP), with two (or more) different values of (u,v) for the SRS resource. Each value can be associated with one of the downlink reference signals (per each TRP). The UE can select the reference TRP and can implicitly indicate the selected reference TRP (or associated reference signal) to the network by changing the base sequence of the SRS.

[0071] In method 400, optionally at Block 416, the uplink signal can be transmitted to the network via the at least one of the multiple TRPs and based on the downlink reference signal. In an aspect, communicating component 242, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, etc., can transmit, to the network via the at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal. As described, in one example, the uplink signal may include a SRS. In addition, in an example, the uplink signal may include the SRS with a base sequence selected to indicate the selected downlink reference signal. In any case, for example, the network can receive the uplink signal and can accordingly process the uplink signal based on the indicated downlink reference signal, whether the downlink reference signal is indicated by the UE 104 (e.g., in MAC-CE or SRS base sequence) or indicated by the network (e.g., in a configuration that may include a timer for switching), as described. Moreover, transmitting the uplink signal based on the selected downlink reference signal may include modulating the uplink signal based on the selected downlink reference signal (e.g., modulating the uplink signal around a center frequency associated with the selected downlink reference signal). In another example, transmitting the uplink signal based on the selected downlink reference signal may include using a beam corresponding to a beam of the downlink reference signal (e.g., based on the QCL-Type of the selected downlink reference signal), and/or the like.

[0072] In yet another example, in method 400, optionally at Block 418, a receive beam to receive the downlink reference signal or a subsequent downlink signal can be switched. In an aspect, communicating component 242, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, etc., can switch the receive beam to receive the downlink reference signal or the subsequent downlink signal, where the switching may be based on the selected downlink reference signal. In an example, communicating component 242 can autonomously switch the receive beam (e.g., based on detecting expiration of the timer or otherwise) or may receive an indication from the network to switch the receive beam based on the transmitted uplink signal. In one example, communicating component 242 may switch the receive beam for each TRS based on configured QCL-Type D, or utilizing the uplink signal transmission with the same beam of the selected downlink reference signal. Similarly, in method 400, optionally at Block 420, a transmit beam to transmit the uplink signal or a subsequent uplink signal can be switched. In an aspect, communicating component 242, e.g., in conjunction with processor(s) 212, memory 216, transceiver 202, etc., can similarly switch the transmit beam to transmit the uplink signal or the subsequent uplink signal based on the selected downlink reference signal. For example, communicating component 242 can switch the transmit beam to be the same as, or reciprocal to, the beam of the selected downlink reference signal, which may be based on a QCL relationship or TCI state indicated for the selected downlink reference signal. [0073] FIG. 5 illustrates a flow chart of an example of a method 500 for receiving an indication of one of multiple downlink reference signals used in transmitting an uplink signal, in accordance with aspects described herein. In an example, a base station 102 or other network component that can communicate with multiple TRPs (e.g., TRPs 140, 142) can perform the functions described in method 500 using one or more of the components described in FIGS. 1 and 3.

[0074] In method 500, at Block 502, multiple downlink reference signals can be transmitted, to a UE, using multiple TRPs. In an aspect, configuring component 342, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, etc., can transmit, to the UE (e.g., UE 104), the multiple downlink reference signals using multiple TRPs, such as TRPs 140, 142. For example, configuring component 342 can cause the TRPs 140, 142 to transmit downlink reference signals, which may include CSI-RS, TRS, SSB, etc. In one example, configuring component 342 can cause the TRPs 140, 142 to transmit the downlink reference signals over the same or similar or different time and/or frequency resources. In addition, for example, configuring component 342 can configure UEs to receive the downlink reference signal based on one or more parameters transmitted in a configuration via RRC signaling, system information broadcast, etc. For example, configuring component 342 can transmit, e.g., via each TRP 140, 142, a configuration indicating QCL assumptions (e.g., TCI states) for each TRP for DMRS of PDSCH and PDCCH, such that the UE 104 can use the indicated QCL reference signal sources (e.g., CSI-RS, TRS, SSB, etc.) to obtain or otherwise determine and/or estimate the Doppler shift of each TRP and/or a corresponding Rx beam for receiving the reference signals.

[0075] In method 500, optionally at Block 504, an indication of a downlink reference signal from the multiple downlink reference signals based on which an uplink reference signal is transmitted can be received from the UE. In an aspect, RS indication receiving component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can receive, from the UE, the indication of the downlink reference signal from the multiple downlink reference signals (e.g., transmitted by different TRPs) based on which the uplink signal is transmitted. For example, the indication of the downlink reference signal may include a CSI-RS resource indicator of a CSI-RS or TRS, a SSB index of a SSB, etc. to allow the base station 102 to identify the downlink reference signal on which a transmitted uplink signal is based in order to process the uplink signal based on the downlink reference signal.

[0076] In an example, in receiving the indication at Block 504, optionally at Block 506, the indication can be received in a MAC-CE. In an aspect, RS indication receiving component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can receive the indication in the MAC-CE. For example, RS indication receiving component 352 can receive a CSI-RS resource indicator of the selected downlink reference signal (e.g., where the downlink reference signal is a CSI-RS or TRS), or a SSB index of the selected downlink reference signal (e.g., where the downlink reference signal is a SSB), etc. In these examples, the base station 102 or network component can identify the selected downlink reference signal based on the CSI- RS resource indicator or SSB index indicated in the MAC-CE. In another example, RS indication receiving component 352 can receive the MAC-CE as indicating a signal metric value of the downlink reference signal, such as the Doppler shift as experienced at the UE 104. As described, for example, the base station 102 or network component can utilize the signal metric in pre-compensating subsequent downlink signals.

[0077] In another example, in receiving the indication at Block 504, optionally at Block 508, the indication can be determined based on a base sequence of a SRS. In an aspect, RS indication receiving component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can determine the indication based on the base sequence of the SRS. For example, different SRS base sequences can correspond to different downlink reference signals, and can be used to indicate the selected downlink reference signal. In this example, optionally at Block 510, a configuration indicating associations between the downlink reference signals and the SRS base sequences can be transmitted. In an aspect, configuring component 342, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, etc., can transmit (e.g., via the one or more TRPs 140, 142) the configuration indicating associations between the downlink reference signals (e.g., an index of the downlink reference signals or an associated TRP) and a SRS base sequence. The UE 104, in this example, can receive the configuration and can accordingly select the SRS base sequence to indicate the selected downlink reference signal.

[0078] In yet another example, optionally at Block 512, a configuration indicating a timer value for determining to switch among multiple downlink reference signals can be transmitted. In an aspect, configuring component 342, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, etc., can transmit the configuration indicating the timer value for determining to switch among multiple downlink reference signals. In addition, as described, the configuration may indicate the downlink reference signals to use at each expiry of the timer. The UE 104, in an example, can accordingly initialize a timer based on the timer value at the time of switching to a certain reference signal, and after expiration of the timer, can select a next downlink reference signal for use in transmitting the uplink signal. In one example, the UE 104 may still indicate the switching or the selected downlink reference signal to the base station 102 or network component. The pattern of selection may also be indicated in the configuration. For example, for a UE 104 traveling in a known direction (e.g., via a HST), the base station 102 or other network component can know or determine which TRPs the UE 104 is within coverage (or which TRPs are providing the most desirable coverage to the UE 104) and associated time instances or time periods. In this example, configuring component 342 can accordingly set the timer to facilitate the UE 104 selecting an appropriate reference signal from one of the multiple TRPs along the way.

[0079] For example, for the UE moving via HST (e.g., a UE located within a moving HST), the time instances where the UE switches the downlink reference signal can be deterministic based on the UE speed and/or the distance between the TRPs. In this regard, configuring component 342 of the base station 102 or network component can configure N periodic downlink reference signals and a timer. When the timer expires, the UE can switch to the next configured downlink reference signal in the list, such to transmit or modulate uplink signals based on this next configured downlink reference signal.

[0080] In method 500, at Block 514, an uplink signal can be received from the UE and based on the downlink reference signal. In an aspect, configuring component 342, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, etc., can receive, from the UE and based on the downlink reference signal, the uplink signal. As described, in one example, the uplink signal may include a SRS. In addition, in an example, the uplink signal may include the SRS with a base sequence selected to indicate the selected downlink reference signal. In any case, for example, configuring component 342 of the base station 102 or network component can receive the uplink signal for processing based on the indicated downlink reference signal.

[0081] In method 500, optionally at Block 516, the uplink signal can be processed based on the indicated downlink reference signal. In an aspect, uplink signal processing component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can process the uplink signal based on the indicated downlink reference signal. For example, based on the indication described above, uplink signal processing component 352 can determine the downlink reference signal that is used to transmit and/or modulate the uplink signal, and can accordingly determine one or more parameters for subsequent transmissions based on this information (e.g., based on measured signal parameters of the uplink signal and/or based on known parameters of the indicated downlink reference signal).

[0082] In processing the uplink signal at Block 516, optionally at Block 518, a subsequent downlink signal, transmitted to the UE, can be pre-compensated to account for Doppler shift based on the uplink signal. In an aspect, uplink signal processing component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can process the uplink signal such to pre-compensate the subsequent downlink signal, transmitted to the UE, to account for Doppler shift based on the uplink signal. In an example, uplink signal processing component 352 can determine the Doppler shift associated with the uplink signal, or as received in the MAC-CE of the indication at Block 506, etc., and can, based also on the selected downlink reference signal, pre-compensate signals at the appropriate TRP to account for the Doppler shift.

[0083] In another example in processing the uplink signal at Block 516, optionally at Block 520, a beam can be selected based on at least one of the uplink signal or the downlink reference signal. In an aspect, uplink signal processing component 352, e.g., in conjunction with processor(s) 312, memory 316, transceiver 302, configuring component 342, etc., can select the beam based on at least one of the uplink signal or the downlink reference signal. For example uplink signal processing component 352 can process the uplink signal to determine and/or indicate a receive beam or transmit beam corresponding to the selected downlink reference signal, a QCL-Type of the downlink reference signal, etc.

[0084] FIG. 6 is a block diagram of a MIMO communication system 600 including a base station 102 and a UE 104. The MIMO communication system 600 may illustrate aspects of the wireless communication access network 100 described with reference to FIG. 1. The base station 102 may be an example of aspects of the base station 102 described with reference to FIG. 1. The base station 102 may be equipped with antennas 634 and 635, and the UE 104 may be equipped with antennas 652 and 653. In the MIMO communication system 600, the base station 102 may be able to send data over multiple communication links at the same time. Each communication link may be called a “layer” and the “rank” of the communication link may indicate the number of layers used for communication. For example, in a 2x2 MIMO communication system where base station 102 transmits two “layers,” the rank of the communication link between the base station 102 and the UE 104 is two.

[0085] At the base station 102, a transmit (Tx) processor 620 may receive data from a data source. The transmit processor 620 may process the data. The transmit processor 620 may also generate control symbols or reference symbols. A transmit MIMO processor 630 may perform spatial processing (e.g., precoding) on data symbols, control symbols, or reference symbols, if applicable, and may provide output symbol streams to the transmit modulator/demodulators 632 and 633. Each modulator/demodulator 632 through 633 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator/demodulator 632 through 633 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a DL signal. In one example, DL signals from modulator/demodulators 632 and 633 may be transmitted via the antennas 634 and 635, respectively.

[0086] The UE 104 may be an example of aspects of the UEs 104 described with reference to FIGS. 1-2. At the UE 104, the UE antennas 652 and 653 may receive the DL signals from the base station 102 and may provide the received signals to the modulator/demodulators 654 and 655, respectively. Each modulator/demodulator 654 through 655 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each modulator/demodulator 654 through 655 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 656 may obtain received symbols from the modulator/demodulators 654 and 655, perform MIMO detection on the received symbols, if applicable, and provide detected symbols. A receive (Rx) processor 658 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, providing decoded data for the UE 104 to a data output, and provide decoded control information to a processor 680, or memory 682.

[0087] The processor 680 may in some cases execute stored instructions to instantiate a communicating component 242 (see e.g., FIGS. 1 and 2).

[0088] On the uplink (UL), at the UE 104, a transmit processor 664 may receive and process data from a data source. The transmit processor 664 may also generate reference symbols for a reference signal. The symbols from the transmit processor 664 may be precoded by a transmit MIMO processor 666 if applicable, further processed by the modulator/demodulators 654 and 655 (e.g., for SC-FDMA, etc.), and be transmitted to the base station 102 in accordance with the communication parameters received from the base station 102. At the base station 102, the UL signals from the UE 104 may be received by the antennas 634 and 635, processed by the modulator/demodulators 632 and 633, detected by a MIMO detector 636 if applicable, and further processed by a receive processor 638. The receive processor 638 may provide decoded data to a data output and to the processor 640 or memory 642.

[0089] The processor 640 may in some cases execute stored instructions to instantiate a configuring component 342 (see e.g., FIGS. 1 and 3).

[0090] The components of the UE 104 may, individually or collectively, be implemented with one or more ASICs adapted to perform some or all of the applicable functions in hardware. Each of the noted modules may be a means for performing one or more functions related to operation of the MIMO communication system 600. Similarly, the components of the base station 102 may, individually or collectively, be implemented with one or more application specific integrated circuits (ASICs) adapted to perform some or all of the applicable functions in hardware. Each of the noted components may be a means for performing one or more functions related to operation of the MEMO communication system 600.

[0091] The following aspects are illustrative only and aspects thereof may be combined with aspects of other embodiments or teaching described herein, without limitation.

[0092] Aspect 1 is a method for wireless communications including receiving multiple downlink reference signals transmitted by a network via multiple TRPs, selecting, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which to transmit an uplink signal, and transmitting, to the network via at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal.

[0093] In Aspect 2, the method of Aspect 1 includes transmitting, to the network via the at least one of the multiple TRPs, the indication of the downlink reference signal selected from the multiple downlink reference signals.

[0094] In Aspect 3, the method of Aspect 2 includes where selecting the downlink reference signal is based at least in part on measuring strengths of each of the multiple downlink reference signals.

[0095] In Aspect 4, the method of any of Aspects 2 or 3 includes where selecting the downlink reference signal is based at least in part on determining that the downlink reference signal corresponds to a closest one of the multiple TRPs.

[0096] In Aspect 5, the method of any of Aspects 2 to 4 includes where selecting the downlink reference signal is based at least in part on a Doppler shift sign and value estimated from the downlink reference signal.

[0097] In Aspect 6, the method of Aspect 5 includes where the value is one of a RSRP, RSSI, or time of arrival of first path from one of the multiple TRPs.

[0098] In Aspect 7, the method of any of Aspects 2 to 6 includes where transmitting the indication of the downlink reference signal includes transmitting a MAC-CE that includes the indication.

[0099] In Aspect 8, the method of Aspect 7 includes where the downlink reference signal is a CSI-RS or a SSB.

[00100] In Aspect 9, the method of Aspect 8 includes where the MAC-CE further indicates a CSI-RS resource indicator of the CSI-RS.

[00101] In Aspect 10, the method of any of Aspects 8 or 9 includes where the MAC-CE further indicates a SSB index of the SSB. [00102] In Aspect 11, the method of any of Aspects 7 to 10 includes where the MAC-CE further indicates Doppler shift metrics associated with the multiple downlink reference signals.

[00103] In Aspect 12, the method of any of Aspects 2 to 11 includes where the uplink signal is a SRS, and where transmitting the indication of the downlink reference signal includes selecting a base sequence of the SRS signal to indicate the downlink reference signal.

[00104] In Aspect 13, the method of Aspect 12 includes where selecting the base sequence of the SRS is based at least in part on a configuration received from the network that indicates an association between the base sequence and the downlink reference signal.

[00105] In Aspect 14, the method of Aspect 1 includes receiving, from the network, indications of multiple downlink reference signals, including the indication of the downlink reference signal, and a timer value for determining to switch among the multiple downlink reference signals, where selecting the downlink reference signal is based at least in part on the indication of the downlink reference signals and detecting expiration of a timer based on the timer value.

[00106] In Aspect 15, the method of Aspect 14 includes switching a receive beam to receive the downlink reference signal based at least in part on detecting expiration of the timer.

[00107] In Aspect 16, the method of any of Aspects 14 or 15 includes switching a transmit beam to transmit the uplink signal based at least in part on detecting expiration of the timer.

[00108] In Aspect 17, the method of any of Aspects 1 to 16 includes where transmitting the uplink signal comprises modulating the uplink signal around a center frequency determined based on the downlink reference signal.

[00109] Aspect 18 is a method for wireless communications including transmitting, to a UE, multiple downlink reference signals using multiple TRPs, and receiving, from the UE and based on an indication of the downlink reference signal selected from the multiple downlink reference signals, an uplink signal.

[00110] In Aspect 19, the method of Aspect 18 includes pre-compensating a subsequent downlink reference signal, transmitted to the UE, to account for Doppler shift based on the uplink signal. [00111] In Aspect 20, the method of any of Aspects 18 or 19 includes receiving, from the UE, the indication of the downlink reference signal selected from the multiple downlink reference signals based on which the uplink signal is transmitted by the UE.

[00112] In Aspect 21, the method of Aspect 20 includes where receiving the indication of the downlink reference signal includes receiving a MAC-CE that includes the indication. [00113] In Aspect 22, the method of Aspect 21 includes where the downlink reference signal is a CSI-RS or a S SB.

[00114] In Aspect 23, the method of Aspect 22 includes where the MAC-CE further indicates a CSI-RS resource indicator of the CSI-RS.

[00115] In Aspect 24, the method of any of Aspects 22 or 23 includes where the MAC-CE further indicates a SSB index of the SSB.

[00116] In Aspect 25, the method of any of Aspects 21 to 24 includes where the MAC-CE further indicates a Doppler shift metrics associated with the multiple downlink reference signals, and further comprising pre-compensating a subsequent downlink signal, transmitted to the UE, to account for the Doppler shift.

[00117] In Aspect 26, the method of any of Aspects 20 to 25 includes where the uplink signal is a SRS, and where receiving the indication of the downlink reference signal includes determining the downlink reference signal based on a base sequence of the SRS. [00118] In Aspect 27, the method of Aspect 25 includes where determining the downlink reference signal includes determining an association between the downlink reference signal and the base sequence of the SRS as specified in a configuration transmitted to the UE.

[00119] In Aspect 28, the method of any of Aspects 18 to 27 includes transmitting, to the UE, indications of multiple downlink reference signals, including the indication of the downlink reference signal, and a timer value for determining to switch among the multiple downlink reference signals, where receiving the indication of the downlink reference signal is based at least in part on the indication of the downlink reference signals and expiration of a timer based on the timer value.

[00120] Aspect 29 is an apparatus for wireless communication including a transceiver, a memory configured to store instructions, and one or more processors communicatively coupled with the memory and the transceiver, where the one or more processors are configured to perform one or more of the methods of any of Aspects 1 to 28. [00121] Aspect 30 is an apparatus for wireless communication including means for performing one or more of the methods of any of Aspects 1 to 28.

[00122] Aspect 31 is a computer-readable medium including code executable by one or more processors for wireless communications, the code including code for performing one or more of the methods of any of Aspects 1 to 28.

[00123] The above detailed description set forth above in connection with the appended drawings describes examples and does not represent the only examples that may be implemented or that are within the scope of the claims. The term “example,” when used in this description, means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and apparatuses are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[00124] Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, computer-executable code or instructions stored on a computer-readable medium, or any combination thereof.

[00125] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a specially programmed device, such as but not limited to a processor, a digital signal processor (DSP), an ASIC, a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination thereof designed to perform the functions described herein. A specially programmed processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A specially programmed processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[00126] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a non-transitory computer-readable medium. Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a specially programmed processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of’ indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[00127] Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer-readable media can comprise RAM, ROM, EEPROM, CD- ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general- purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[00128] The previous description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the common principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. An apparatus for wireless communication, comprising: a transceiver; a memory configured to store instructions; and one or more processors communicatively coupled with the memory and the transceiver, wherein the one or more processors are configured to execute the instructions to cause the apparatus to: receive multiple downlink reference signals transmitted by a network via multiple transmission/reception points (TRPs); select, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which to transmit an uplink signal; and transmit, to the network via at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal.

2. The apparatus of claim 1, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to transmit, to the network via the at least one of the multiple TRPs, the indication of the downlink reference signal selected from the multiple downlink reference signals.

3. The apparatus of claim 2, wherein the one or more processors are configured to execute the instructions to cause the apparatus to select the downlink reference signal based at least in part on measuring strengths of each of the multiple downlink reference signals.

4. The apparatus of claim 2, wherein the one or more processors are configured to execute the instructions to cause the apparatus to select the downlink reference signal based at least in part on determining that the downlink reference signal corresponds to a closest one of the multiple TRPs.

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5. The apparatus of claim 2, wherein the one or more processors are configured to execute the instructions to cause the apparatus to select the downlink reference signal based at least in part on a Doppler shift sign and a value estimated from the downlink reference signal.

6. The apparatus of claim 5, wherein the value is one of a reference signal received power (RSRP), received signal strength indicator (RS SI), or time of arrival of first path from one of the multiple TRPs.

7. The apparatus of claim 2, wherein the one or more processors are configured to execute the instructions to cause the apparatus to transmit the indication of the downlink reference signal in a media access control (MAC) control element (CE) that includes the indication.

8. The apparatus of claim 7, wherein the downlink reference signal is a channel state information reference signal (CSI-RS) or a synchronization signal block (SSB).

9. The apparatus of claim 8, wherein the MAC-CE further indicates a channel state information reference signal (CSI-RS) resource indicator of the CSI-RS.

10. The apparatus of claim 8, wherein the MAC-CE further indicates a SSB index of the SSB.

11. The apparatus of claim 7, wherein the MAC-CE further indicates Doppler shift metrics associated with the multiple downlink reference signals.

12. The apparatus of claim 2, wherein the uplink signal is a sounding reference signal (SRS), and wherein the one or more processors are configured to execute the instructions to cause the apparatus to transmit the indication of the downlink reference signal at least in part by selecting a base sequence of the SRS signal to indicate the downlink reference signal.

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13. The apparatus of claim 12, wherein the one or more processors are configured to execute the instructions to cause the apparatus to select the base sequence of the SRS based at least in part on a configuration received from the network that indicates an association between the base sequence and the downlink reference signal.

14. The apparatus of claim 1, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to receive, from the network, indications of multiple downlink reference signals, including the indication of the downlink reference signal, and a timer value for determining to switch among the multiple downlink reference signals, wherein the one or more processors are configured to execute the instructions to cause the apparatus to select the downlink reference signal based at least in part on the indication of the downlink reference signals and detecting expiration of a timer based on the timer value.

15. The apparatus of claim 14, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to switch a receive beam to receive the downlink reference signal based at least in part on detecting expiration of the timer.

16. The apparatus of claim 14, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to switch a transmit beam to transmit the uplink signal based at least in part on detecting expiration of the timer.

17. The apparatus of claim 1, wherein the one or more processors are configured to execute the instructions to cause the apparatus to transmit the uplink signal at least in part by modulating the uplink signal around a center frequency determined based on the downlink reference signal.

18. An apparatus for wireless communication, comprising: a transceiver; a memory configured to store instructions; and one or more processors communicatively coupled with the memory and the transceiver, wherein the one or more processors are configured to execute the instructions to cause the apparatus to: transmit, to a user equipment (UE), multiple downlink reference signals using multiple transmission/reception points (TRPs); and receive, from the UE and based on an indication of the downlink reference signal selected from the multiple downlink reference signals, an uplink signal.

19. The apparatus of claim 18, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to pre-compensate a subsequent downlink reference signal, transmitted to the UE, to account for Doppler shift based on the uplink signal.

20. The apparatus of claim 18, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to receive, from the UE, the indication of the downlink reference signal selected from the multiple downlink reference signals based on which the uplink signal is transmitted by the UE.

21. The apparatus of claim 20, wherein the one or more processors are configured to execute the instructions to cause the apparatus to receive the indication of the downlink reference signal in a media access control (MAC) control element (CE) that includes the indication.

22. The apparatus of claim 21, wherein the downlink reference signal is a channel state information reference signal (CSI-RS) or a synchronization signal block (SSB).

23. The apparatus of claim 22, wherein the MAC-CE further indicates at least one of a channel state information reference signal (CSI-RS) resource indicator of the CSI-RS or a SSB index of the SSB.

24. The apparatus of claim 21, wherein the MAC-CE further indicates a Doppler shift metrics associated with the multiple downlink reference signals, and wherein the one or more processors are further configured to execute the instructions to cause the apparatus to pre-compensate a subsequent downlink signal, transmitted to the UE, to account for the Doppler shift.

25. The apparatus of claim 20, wherein the uplink signal is a sounding reference signal (SRS), and wherein the one or more processors are configured to execute the instructions to cause the apparatus to receive the indication of the downlink reference signal at least in part by determining the downlink reference signal based on a base sequence of the SRS.

26. The apparatus of claim 25, wherein the one or more processors are configured to execute the instructions to cause the apparatus to determine the downlink reference signal at least in part by determining an association between the downlink reference signal and the base sequence of the SRS as specified in a configuration transmitted to the UE.

27. The apparatus of claim 18, wherein the one or more processors are further configured to execute the instructions to cause the apparatus to transmit, to the UE, indications of multiple downlink reference signals, including the indication of the downlink reference signal, and a timer value for determining to switch among the multiple downlink reference signals, wherein the one or more processors are configured to execute the instructions to cause the apparatus to receive the indication of the downlink reference signal based at least in part on the indication of the downlink reference signals and expiration of a timer based on the timer value.

28. A method for wireless communications, comprising: receiving multiple downlink reference signals transmitted by a network via multiple transmission/reception points (TRPs); selecting, based on an indication, a downlink reference signal from the multiple downlink reference signals based on which to transmit an uplink signal; and transmitting, to the network via at least one of the multiple TRPs and based on the downlink reference signal, the uplink signal.

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29. The method of claim 28, further comprising transmitting, to the network via the at least one of the multiple TRPs, the indication of the downlink reference signal selected from the multiple downlink reference signals.

30. A method for wireless communications, comprising: transmitting, to a user equipment (UE), multiple downlink reference signals using multiple transmission/reception points (TRPs); and receiving, from the UE and based on an indication of the downlink reference signal selected from the multiple downlink reference signals, an uplink signal.

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