Patent Description:
The following relates generally to wireless communications and more specifically to tracking reference signal techniques in wireless communications.

A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

Some wireless communications systems may support beamforming operations for directional communications. Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, may be a signal processing technique that may be used at a transmitting device or a receiving device to select, shape, or steer an antenna beam (for example, a transmit directional beam, a receive directional beam) along a spatial path between the transmitting device and the receiving device. Some wireless communications systems may support beamforming operations to mitigate pathloss and blockages with respect to the spatial path. As demand for communication efficiency increases, it may be desirable for a wireless communications system to target low latencies and improve reliability using beamforming operations.

<CIT> discloses a CoMP scenario wherein at least two base stations send phase tracking reference signals to a single UE in different resources.

The described techniques relate to improved methods, apparatuses and computer program that support tracking reference signal techniques in wireless communications. In some aspects, techniques are provided for nodes in a wireless communications system to establish joint communications in which a set of two or more transmission-reception points (TRPs) communicate with a user equipment (UE). The UE measures one or more reference signals, such as tracking reference signals (TRSs), from a subset of the set of TRPs for use in management of joint communications parameters at the UE, wherein the subset of TRPs include TRPs having a relatively large contribution to signals received at the UE, and may transmit periodic or semi-persistent TRSs to be measured at the UE. In some cases, one of the TRPs may provide an indication to the UE of which TRPs are included in the subset of TRPs. In some cases, the UE may determine which TRPs are included in the subset of TRPs based on a signal quality of transmissions associated with each TRP (e.g., TRPs with a reference signal received power (RSRP) that meets or exceeds a threshold value). In some cases, one or more TRPs that are not included in the subset of TRPs may transmit aperiodic or periodic references signals to the UE.

Some wireless communication systems may include communication devices, such as user equipments (UEs) and base stations (e.g., next-generation NodeBs or giga-NodeBs (which may be referred to as gNBs)), that may support multiple radio access technologies. Examples of radio access technologies include <NUM> systems such as Long Term Evolution (LTE) systems and fifth generation (<NUM>) systems which may be referred to as New Radio (NR) systems. Some wireless communications systems, such as multiple-input multiple output (MIMO) systems, may configure the communication devices to support millimeter wave (mmW) communications (also referred to as directional communications). In some examples, the communication devices may experience one or more of a pathloss or a blockage with respect to a spatial path for the mmW communications. As a result, the communication devices may support beamforming operations to counter one or more of the pathloss or the blockage, among other examples. Further, in some cases, joint transmissions from two or more communication devices may be used to counter pathloss or blockage, in which multiple devices transmit or receive a signal from a UE. However, such beamformed communications may be relatively power intensive, and thus power-saving techniques that may be used in such communications are desirable in order to reduce power consumption.

According to various aspects of the present disclosure, techniques are provided for transmitting one or more reference signals, such as a tracking reference signal (TRS), in joint transmission operations from a subset of a set of transmission reception points (TRPs) that are used for joint communications. A UE may monitor for reference signal transmissions from the subset of TRPs and use measurements to determine one or more joint communications parameters, such as beamforming parameters, trimming error, frequency error, or any combinations thereof. For example, RSRP or signal-to-noise ratio (SNR) measurement parameters associated with the received TRSs may be used to determine a preferred transmit-receive beam pair or beam refinement for a transmit-receive beam pair (e.g., based on receive beamforming parameters that provide a highest or acceptable RSRP/SNR). Further, the UE may determine a timing error based on TRS measurements (e.g., based on a timing difference between an expected and measured starting time associated with a predetermined TRS sequence). In cases where frequency error is measured, the UE may determine the frequency error based on a measured difference between an expected and a measured reference signal frequency.

In some cases, a UE or other wireless node may establish joint communications in which a set of two or more TRPs communicate with the UE. The UE may measure one or more reference signals, such as TRSs, from a subset of the set of TRPs for use in management of joint communications parameters at the UE. The subset of TRPs include TRPs having a relatively large contribution to signals received at the UE, and may transmit periodic or semi-persistent TRSs to be measured at the UE. In some cases, one of the TRPs may provide an indication to the UE of which TRPs are included in the subset of TRPs. In some cases, the UE may determine which TRPs are included in the subset of TRPs based on a signal quality of transmissions associated with each TRP (e.g., TRPs with a reference signal received power (RSRP) that meets or exceeds a threshold value). In some cases, one or more TRPs that are not included in the subset of TRPs may transmit aperiodic or periodic references signals to the UE.

Particular aspects of the subject matter described in this disclosure may be implemented to realize one or more of the following potential advantages. The techniques employed by the described communication devices may provide benefits and enhancements to the operation of the communication devices. For example, operations performed by the described communication devices may provide improvements to power consumption when performing beam operations. In some examples, configuring a subset of TRPs from a set of TRPs used for joint communications as described may support improvements to power consumption through monitoring of fewer reference signals at a UE, and, in some examples, may promote higher reliability for beamforming operations through measurements of TRPs having the largest contributions to jointly transmitted signals, among other benefits.

Aspects of the disclosure are initially described in the context of wireless communications systems. Examples of systems using joint transmissions are then discussed for various aspects. Aspects of the disclosure are further illustrated by and described with reference to process flows, apparatus diagrams, system diagrams, and flowcharts that relate to tracking reference signal techniques in wireless communications.

<FIG> illustrates an example of a wireless communications system <NUM> that supports tracking reference signal techniques in wireless communications in accordance with aspects of the present disclosure. The wireless communications system <NUM> may include one or more base stations <NUM>, one or more UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

The base stations <NUM> may communicate with the core network <NUM>, or with one another, or both. For example, the base stations <NUM> may interface with the core network <NUM> through one or more backhaul links <NUM> (e.g., via an S1, N2, N3, or other interface). The base stations <NUM> may communicate with one another over the backhaul links <NUM> (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations <NUM>), or indirectly (e.g., via core network <NUM>), or both. In some examples, the backhaul links <NUM> may be or include one or more wireless links.

For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> megahertz (MHz)). Devices of the wireless communications system <NUM> (e.g., the base stations <NUM>, the UEs <NUM>, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system <NUM> may include base stations <NUM> or UEs <NUM> that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE <NUM> may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth.

The time intervals for the base stations <NUM> or the UEs <NUM> may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of Ts = <NUM>/(Δfmax · Nf) seconds, where Δfmax may represent the maximum supported subcarrier spacing, and Nf may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., <NUM> milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from <NUM> to <NUM>).

A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system <NUM> and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system <NUM> may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

Each base station <NUM> may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term "cell" may refer to a logical communication entity used for communication with a base station <NUM> (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or others). In some examples, a cell may also refer to a geographic coverage area <NUM> or a portion of a geographic coverage area <NUM> (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station <NUM>. For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas <NUM>, among other examples.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by the UEs <NUM> with service subscriptions with the network provider supporting the macro cell. A small cell may be associated with a lower-powered base station <NUM>, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to the UEs <NUM> with service subscriptions with the network provider or may provide restricted access to the UEs <NUM> having an association with the small cell (e.g., the UEs <NUM> in a closed subscriber group (CSG), the UEs <NUM> associated with users in a home or office). A base station <NUM> may support one or multiple cells and may also support communications over the one or more cells using one or multiple component carriers.

In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that may provide access for different types of devices.

The wireless communications system <NUM> may support synchronous or asynchronous operation. For synchronous operation, the base stations <NUM> may have similar frame timings, and transmissions from different base stations <NUM> may be approximately aligned in time. For asynchronous operation, the base stations <NUM> may have different frame timings, and transmissions from different base stations <NUM> may, in some examples, not be aligned in time.

Some UEs <NUM>, such as MTC or IoT devices, may be low cost or low complexity devices and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication). In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans interacting with the application program. Some UEs <NUM> may be designed to collect information or enable automated behavior of machines or other devices.

The core network <NUM> may be an evolved packet core (EPC) or <NUM> core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs <NUM> served by the base stations <NUM> associated with the core network <NUM>. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services <NUM>. The operators IP services <NUM> may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched Streaming Service.

The wireless communications system <NUM> may operate using one or more frequency bands, typically in the range of <NUM> megahertz (MHz) to <NUM> gigahertz (GHz). Generally, the region from <NUM> to <NUM> is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs <NUM> located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than <NUM> kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below <NUM>.

The wireless communications system <NUM> may also operate in a super high frequency (SHF) region using frequency bands from <NUM> to <NUM>, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum (e.g., from <NUM> to <NUM>), also known as the millimeter band. In some examples, the wireless communications system <NUM> may support millimeter wave (mmW) communications between the UEs <NUM> and the base stations <NUM>, and EHF antennas of the respective devices may be smaller and more closely spaced than UHF antennas. In some examples, this may facilitate use of antenna arrays within a device. The propagation of EHF transmissions, however, may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

A base station <NUM> or a UE <NUM> may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station <NUM> or a UE <NUM> may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. In some examples, antennas or antenna arrays associated with a base station <NUM> may be located in diverse geographic locations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

The base stations <NUM> or the UEs <NUM> may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). MIMO techniques include single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

A base station <NUM> or a UE <NUM> may use beam sweeping techniques as part of beam forming operations. For example, a base station <NUM> may use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE <NUM>. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station <NUM> multiple times in different directions. For example, the base station <NUM> may transmit a signal according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by a transmitting device, such as a base station <NUM>, or by a receiving device, such as a UE <NUM>) a beam direction for later transmission or reception by the base station <NUM>.

Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station <NUM> in a single beam direction (e.g., a direction associated with the receiving device, such as a UE <NUM>). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE <NUM> may receive one or more of the signals transmitted by the base station <NUM> in different directions and may report to the base station <NUM> an indication of the signal that the UE <NUM> received with a highest signal quality or an otherwise acceptable signal quality.

In some examples, transmissions by a device (e.g., by a base station <NUM> or a UE <NUM>) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station <NUM> to a UE <NUM>). The UE <NUM> may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station <NUM> may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)), which may be precoded or unprecoded. The UE <NUM> may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by a base station <NUM>, a UE <NUM> may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE <NUM>) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

A receiving device (e.g., a UE <NUM>) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station <NUM>, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as "listening" according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening according to multiple beam directions).

The wireless communications system <NUM> may be a packet-based network that operates according to a layered protocol stack. A Medium Access Control (MAC) layer, or Layer <NUM>, may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE <NUM> and a base station <NUM> or a core network <NUM> supporting radio bearers for user plane data. At the physical layer, or Layer <NUM>, transport channels may be mapped to physical channels.

In some cases, a node in a wireless communications system, such as a UE <NUM>, may use joint communications in which a set of two or more transmission-reception points (TRPs) communicate with the UE (e.g., two or more TRPs at a same or different base station <NUM>). The UE <NUM> may identify a subset of the TRPs that perform joint communications and may measure one or more reference signals, such as TRSs, from the subset of TRPs. The reference signal measurements may be used, for example, in management of joint communications parameters at the UE <NUM> (e.g., beam management, time error tracking, frequency error tracking, or any combinations thereof). The subset of TRPs include TRPs having a relatively large contribution to signals received at the UE <NUM>, and may transmit periodic or semi-persistent TRSs to be measured at the UE <NUM>. In some cases, a base station <NUM> may provide an indication to the UE <NUM> of which TRPs are included in the subset of TRPs. In some cases, the UE <NUM> may determine which TRPs are included in the subset of TRPs based on a signal quality of transmissions associated with each TRP (e.g., TRPs with a RSRP that meets or exceeds a threshold value). In some cases, one or more TRPs that are not included in the subset of TRPs may transmit aperiodic or periodic references signals to the UE <NUM>.

<FIG> illustrates an example of a wireless communications system <NUM> that supports tracking reference signal techniques in wireless communications in accordance with aspects of the present disclosure. In some examples, wireless communications system <NUM> may implement aspects of wireless communications system <NUM>. In some examples, the wireless communications system <NUM> may include a UE <NUM>-a and a number of base stations <NUM>, including a first base station <NUM>-a, a second base station <NUM>-b, and a third base station <NUM>-c, which may be examples of UEs <NUM> and base stations <NUM> described with reference to <FIG>. Base stations <NUM> in this example may be examples of TRPs as discussed herein.

In this example, the UE <NUM>-a and the base stations <NUM> perform joint communications in which downlink transmissions <NUM> may be transmitted concurrently by each base station <NUM> and received at the UE <NUM>-a. In some cases, the base stations <NUM> may act as a single frequency network (SFN) for downlink shared channel transmissions (e.g., physical downlink shared channel (PDSCH) transmissions), for downlink control channel transmissions (e.g., physical downlink control channel (PDCCH) transmissions), and/or other channels, for example, and the UE <NUM>-a may decode one or more channels included in the downlink transmissions <NUM> in a same decoding operation. In this example, the base stations <NUM> and UE <NUM>-a may communicate using beamformed communications, in which the UE <NUM>-a uses a receive beam for receiving downlink transmissions <NUM> and each base station <NUM> uses a transmission beam that is quasi co-located (QCL) with the receive beam. In the example of <FIG>, the first base station <NUM>-a transmits a downlink transmission <NUM>-a using first transmit beam <NUM>, the second base station <NUM>-b transmits a downlink transmission <NUM>-b using second transmit beam <NUM>, and the third base station <NUM>-c transmits downlink transmission <NUM>-c using third transmission beam <NUM>.

The UE <NUM>-a may monitor for various reference signals transmitted by each base station <NUM>. Such reference signals may include, for example, a TRS, which may be used for multiple purposes such as timing and/or frequency error tracking, as a QCL reference signal for other channels or signals, or any combinations thereof. In some cases, each base station <NUM> (or TRP) may have a different cell ID, and jointly serve the UE <NUM>-a, and the base stations <NUM> may transmit joint or separate TRSs for the UE <NUM>-a. In some cases, such as a single-frequency network (SFN) case, the multiple base stations <NUM> may transmit the same TRS to the UE <NUM>-a simultaneously, and thus the UE <NUM>-a sees a combined TRS. In other cases, such as illustrated in the example of <FIG>, different base stations <NUM> may each transmit a separate TRS to the UE <NUM>-a (e.g., in a TDM manner), and the UE may measure TRS from each base station <NUM> separately. In this example, the first base station <NUM>-a may transmit a first TRS <NUM>, the second base station <NUM>-b may transmit a second TRS <NUM>, and the third base station <NUM>-c may transmit a third TRS <NUM>. According to aspects as discussed herein, the UE <NUM>-a may monitor a subset of the base stations <NUM> for various beam tracking or beam management procedures. For example, the UE <NUM>-a may monitor only the first base station <NUM>-a for the first TRS <NUM> and perform timing and/or frequency error measurements based on the first TRS <NUM>, or may monitor two or more but less than all of the base stations <NUM> for TRS measurements. Such scenarios may provide for enhanced measurements (e.g., timing/frequency error measurements or QCL reference signal measurements) for one or more channels or signals that are transmitted by only the monitored base stations <NUM>, for example.

In some aspects, the UE <NUM>-a may monitor a subset of base stations <NUM> for periodic or semi-persistent TRS (P/SP-TRS) transmissions. In some cases, the UE <NUM>-a may be configured with a subset of one or more designated base stations <NUM> or TRPs among the base stations <NUM> or TRPs that are serving the UE <NUM>-a. The designated base stations <NUM> are determined based on which have relatively contributions among all of the serving base stations <NUM> to the received signals at the UE <NUM>-a. In some cases, the subset of base stations <NUM> can be explicitly configured for the UE <NUM>-a (e.g., by higher layer signaling such as a medium access control (MAC) control element (CE), in downlink control information (DCI), or in radio resource control (RRC) signaling). In some cases, the subset of base stations <NUM> may be implicitly determined based on a measurement report of the UE <NUM>-a. For example, the N serving base stations <NUM> with the best cell-level RSRP may be selected as the subset of base stations <NUM>. In some cases, the value of N may be configured at the UE <NUM>-a, or may be a pre-specified value. In other cases, the value of N may be based on a number of base stations <NUM> that have a reference signal received power (RSRP) that exceeds a threshold value, where the threshold value may be configured at the UE <NUM>-a or may be a pre-specified value. Based on the determined subset of base stations <NUM> to be monitored, the UE <NUM>-a may use the associated P/SP TRS resources to measure associated TRSs and track transmit/receive beam beams and estimate time and frequency error. In some cases, base stations <NUM> that are not included in the determined subset of base stations <NUM> may transmit aperiodic TRS (A-TRS), or may also transmit P/SP-TRS. An example of different subsets of base stations <NUM> or TRPs that transmit P/SP-TRS and A-TRS is illustrated in <FIG>.

<FIG> illustrates an example of a wireless communications system <NUM> that supports tracking reference signal techniques in wireless communications in accordance with aspects of the present disclosure. In some examples, wireless communications system <NUM> may implement aspects of wireless communications system <NUM> or <NUM>. In some examples, the wireless communications system <NUM> may include a UE <NUM>-b and a number of base stations <NUM>, including a first base station <NUM>-d, a second base station <NUM>-e, a third base station <NUM>-f, a fourth base station <NUM>-g and a fifth base station <NUM>-h, which may be examples of UEs <NUM> and base stations <NUM> described with reference to <FIG>. Base stations <NUM> in this example may be examples of TRPs or include one or more TRPs as discussed herein.

In this example, the UE <NUM>-b and the base stations <NUM> perform joint communications in which downlink transmissions <NUM> may be transmitted concurrently by each base station <NUM> and received at the UE <NUM>-b. In this example, similarly as in the example of <FIG>, the base stations <NUM> and UE <NUM>-b may communicate using beamformed communications, in which the UE <NUM>-b uses a receive beam for receiving downlink transmissions <NUM> and each base station <NUM> uses a transmission beam that is QCL with the receive beam. In the example of <FIG>, the first base station <NUM>-d transmits a downlink transmission <NUM>-a using first transmit beam <NUM>, the second base station <NUM>-e transmits a downlink transmission <NUM>-b using second transmit beam <NUM>, the third base station <NUM>-f transmits downlink transmission <NUM>-c using third transmission beam <NUM>, the fourth base station <NUM>-g transmits downlink transmission <NUM>-d using fourth transmission beam <NUM>, and the fifth base station <NUM>-h transmits downlink transmission <NUM>-e using fifth transmission beam <NUM>. In this example, the fourth base station <NUM>-g may include two TRPs (e.g., two RRHs) that include a first TRP <NUM>-g-<NUM> and a second TRP <NUM>-g-<NUM> that are used for communications with the UE <NUM>-b.

The UE <NUM>-b may monitor for various reference signals transmitted by each base station <NUM>, such as TRS transmissions. In this example, each base station <NUM> may have a different cell ID, and jointly serve the UE <NUM>-b, and different base stations <NUM> may each transmit a separate TRS to the UE <NUM>-b (e.g., in a TDM manner), and the UE may measure TRS from each base station <NUM> separately. In this example, the first base station <NUM>-d may transmit a first TRS <NUM>, the second base station <NUM>-e may transmit a second TRS <NUM>, the third base station <NUM>-f may transmit a third TRS <NUM>, and the fifth base station <NUM>-h may transmit a fifth TRS <NUM>. In this example, the first TRP <NUM>-g-<NUM> and second TRP <NUM>-g-<NUM> of the fourth base station <NUM>-g may jointly transmit a fourth TRS <NUM> via joint fourth transmission beam <NUM>, and be assigned a single cell ID. In other cases, different TRPs of a base station <NUM> may have different cell IDs.

According to aspects as discussed herein, the UE <NUM>-b may monitor a first subset of the base stations <NUM> for P/SP-TRS transmission for various beam tracking or beam management procedures. In this example, the UE <NUM>-b may monitor the first base station <NUM>-d for the first TRS <NUM>, the second base station <NUM>-e for the second TRS, and the third base station <NUM>-f for the third TRS <NUM>, and perform timing and/or frequency error measurements based on the monitored reference signals of the first subset of base stations <NUM>. Further, in this example, a second subset of base stations may include the fourth base station <NUM>-g and fifth base station <NUM>-h, which may transmit A-TRSs as the fourth TRS <NUM> and fifth TRS <NUM>, respectively.

As discussed with reference to <FIG>, in some cases the UE <NUM>-b may be configured with the first subset of one or more designated base stations <NUM>. The designated base stations <NUM> may be determined based on which have relatively large contributions among all of the serving base stations <NUM> to the received signals at the UE <NUM>-b. In some cases, the first subset of base stations <NUM> can be explicitly configured for the UE <NUM>-b (e.g., by higher layer signaling such as a MAC-CE, in DCI, or in RRC signaling). In some cases, the first subset of base stations <NUM> may be implicitly determined based on a measurement report of the UE <NUM>-b (e.g., the N serving base stations <NUM> with the best cell-level RSRP may be selected as the first subset as discussed herein).

In this example, each of the base stations <NUM> in the second subset of base stations may transmit a A-TRS. The UE <NUM>-b may monitor for the A-TRS based on a trigger that is received at the UE <NUM>-b. In some cases, a Layer-<NUM> signal-based trigger for A-TRS may be used for TRPs with different cell IDs. For example, for serving TRPs outside the first subset, only A-TRS can be used instead of P/SP-TRS. In some cases, the UE <NUM>-b may be signaled to indicate a shared TRS among a group of (one or more) TRPs, where those TRPs may share the same RF/oscillator, such as first TRP <NUM>-g-<NUM> and second TRP <NUM>-g-<NUM> in the example of <FIG>.

In some cases, the Layer-<NUM> signal that triggers aperiodic TRS can be transmitted from a single or a subset of TRPs or base stations <NUM>, which may be different from the TRPs or base stations <NUM> that actually transmit the TRS. In such cases, the Layer-<NUM> signal may dynamically indicate A-TRS from TRPs with different cell IDs. For example, multiple resource sets for A-TRS can be configured for a UE, and the Layer-<NUM> triggering signal may indicate a resource set index associated with the A-TRS. In some cases, each TRS resource in a resource set can be associated with a group of one or more TRPs (e.g., TRPs sharing the same RF components), and each group of TRP(s) are associated with different cell IDs. The Layer-<NUM> signal in such cases may indicate an index among the configured resources.

In some cases, the UE <NUM>-b may request TRS periodicity for a specific TRP or a subset of TRPs such as the first subset of base stations in the example of <FIG>. Such a request may be transmitted through an uplink control channel (e.g., UCI in PUCCH), through a MAC-CE, or a combination of Layer-<NUM> signaling and MAC-CE, for example. In some cases, RRC or UE assistance information feedback from UE <NUM>-b may be used to provide the request from the UE <NUM>-b.

<FIG> illustrates an example of a process flow <NUM> that supports tracking reference signal techniques in wireless communications in accordance with aspects of the present disclosure. In some examples, process flow <NUM> may implement aspects of wireless communications system <NUM>, <NUM>, or <NUM>. For example, the process flow <NUM> may be based on a configuration by a base station <NUM> or a UE <NUM>, and implemented for enhanced measurements at a UE which may provide reduced power consumption (through reduced retransmissions and decoding iterations), enhanced spectral efficiency, higher data rates and, may promote higher reliability for beamforming operations, among other benefits.

The process flow <NUM> may include a first base station <NUM>-i and a second base station <NUM>-j, which may examples of TRPs as discussed herein, and a UE <NUM>-c, which may be an example of a UE or communication node as discussed herein. The base stations <NUM> and UE <NUM>-c also may be examples of base stations <NUM> and UEs <NUM> as described with reference to <FIG>. In the following description of the process flow <NUM>, the communications between the base stations <NUM> and the UE <NUM>-c may be transmitted in a different order than the example order shown, or the operations performed by the base stations <NUM> and the UE <NUM>-c may be performed in different orders or at different times. Some operations may also be omitted from the process flow <NUM>, and other operations may be added to the process flow <NUM>. Further, while this example illustrates the base stations <NUM> transmitting and the UE <NUM>-c receiving TRSs, techniques such as discussed herein may be used in cases where other devices may transmit or receive TRSs in accordance with techniques as discussed herein.

At <NUM>, the UE <NUM>-c and base stations <NUM> identify a set of TRPs for joint communications with the UE <NUM>-c. In some cases, the UE <NUM>-c and base stations <NUM> may perform a beam training procedure in order to establish one or more beams for use in beamformed communications. In some cases, each of the first base station <NUM>-i and second base station <NUM>-j may perform joint communications with the UE <NUM>-c. Further, each of the first base station <NUM>-i and the second base station <NUM>-j may have different cell IDs.

Optionally, at <NUM>, the first base station <NUM>-i may transmit configuration information to the UE <NUM>-c. The configuration information may include, for example, information related to a subset of base stations or TRPs that are to be monitored for periodic TRS transmissions. In other cases, the configuration information may include an indication of a number of TRPs that are to be monitored for P/SP-TRS transmissions.

At <NUM>, the UE <NUM>-c may determine a subset of base stations <NUM> or TRPs for P/SP-TRS transmissions. In some cases, the subset of base stations <NUM> or TRPs may be determined based on configuration information received from the first base station <NUM>-i. In other cases, the determination of the subset of TRPs may be based on one or more reference signal measurements performed at the UE <NUM>-c. In some cases, the UE <NUM>-c may be configured with a number (N) of TRPs that are to be monitored in the subset of TRPs. Additionally or alternatively, the UE <NUM>-c may be configured with a threshold value of an RSRP, where TRPs having an RSRP at or above the threshold are included in the subset of TRPs and TRPs having an RSRP below the threshold are not included in the subset of TRPs. In some cases, the UE <NUM>-c may identify one or more TRPs having an RSRP that meets or exceeds The RSRP threshold, and the UE <NUM>-c may request periodic or semi-periodic TRS from the one or more identified TRPs. Optionally, at <NUM>, the UE can transmit a TRS request to the first base station <NUM>-i, that indicates the one or more identified TRPs.

At <NUM>, the first base station <NUM>-i may determine a subset of TRPs for periodic or semi-periodic TRS transmissions. At <NUM>, the first base station <NUM>-i may transmit a periodic or semi-periodic TRS to the UE <NUM>-c. In some cases, the first base station <NUM>-i may determine the subset of TRPs based on the TRS request received from the UE <NUM>-c. In other cases, the first base station <NUM>-i may determine the subset of TRPs based on one or more measurements received from the UE <NUM>-c, and the subset of TRPs may be based on TRPs having the best channel conditions at the UE.

At <NUM>, the first base station <NUM>-i and the second base station <NUM>-j may determine to transmit an aperiodic TRS. In some cases, the determination to transmit the aperiodic TRS may be based on one or more trigger conditions such as an amount of time since a prior aperiodic TRS, a change in one or more measured values at the UE, and the like. In this example, the first base station <NUM>-i may optionally, at <NUM>, transmit an aperiodic TRS trigger signal to the UE <NUM>-c. Following such an aperiodic TRS trigger, the second base station <NUM>-j, at <NUM>, may transmit the aperiodic TRS to the UE <NUM>-c. The UE may receive the aperiodic TRS trigger and monitor for the aperiodic TRS transmission in resources that are associated with the aperiodic TRS trigger.

At <NUM>, the UE may measure one or more received TRS is that are transmitted by the one or more TRPs. In some cases, the UE may measure the periodic or semi-periodic TRSs transmitted from TRPs of the identified subset of TRPs (e.g., from the first base station <NUM>-i). Further, the UE may measure one or more aperiodic TRS transmissions from one or more TRPs outside of the identified subset of TRPs (e.g., from the second base station <NUM>-j). The UE <NUM>-c, at <NUM>, may transmit a measurement report to the first base station <NUM>-i. Optionally at <NUM>, the UE <NUM>-c may transmit a measurement report associated with the aperiodic TRS to the second base station <NUM>-j, or to the first base station <NUM>-i along with a measurement report of the periodic TRSs.

At <NUM>, the UE <NUM>-c may perform beam management procedures based on the measured TRSs (e.g., time and/or frequency error tracking). Likewise at <NUM>, the first base station <NUM>-i may perform beam management based on the measurement report received from the UE <NUM>-c (e.g., beam refinement or power control based on the measurement report). Optionally at <NUM>, the second base station <NUM>-j may perform beam management based on a measurement report received from the UE <NUM>-c or the first base station <NUM>-i that is associated with the aperiodic TRS.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a UE <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver <NUM> may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to TRS techniques in wireless communications, etc.). Information may be passed on to other components of the device <NUM>. The receiver <NUM> may be an example of aspects of the transceiver <NUM> described with reference to <FIG>. The receiver <NUM> may utilize a single antenna or a set of antennas.

The communications manager <NUM> may identify a set of TRPs that transmit joint communications to the UE, where each TRP of the set of TRPs has a separate cell identification, determine a subset of the set of TRPs that are to transmit periodic TRSs, monitor, based on the determining, for one or more TRSs from the subset of TRPs, and update one or more joint communications parameters for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

The actions performed by the communications manager <NUM> as described herein may be implemented to realize one or more potential advantages. For example, operations performed by communications manager <NUM> may provide improvements to power consumption when performing beam operations. In some examples, configuring a subset of TRPs from a set of TRPs used for joint communications as described may support improvements to power consumption through monitoring of fewer reference signals at a UE, and, in some examples, may promote higher reliability for beamforming operations through measurements of TRPs having the largest contributions to jointly transmitted signals, among other benefits.

In some examples, the transmitter <NUM> may be collocated with a receiver <NUM> in a transceiver.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a device <NUM>, or a UE <NUM> as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may be an example of aspects of the communications manager <NUM> as described herein. The communications manager <NUM> may include a configuration manager <NUM>, a TRP selection manager <NUM>, a TRS manager <NUM>, and a beam manager <NUM>. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

The configuration manager <NUM> may identify a set of TRPs that transmit j oint communications to the UE, where each TRP of the set of TRPs has a separate cell identification.

The TRP selection manager <NUM> may determine a subset of the set of TRPs that are to transmit periodic TRSs.

The TRS manager <NUM> may monitor, based on the determining, for one or more TRSs from the subset of TRPs.

The beam manager <NUM> may update one or more joint communications parameters for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs. In some cases, the joint communications parameters may include one or more of a transmit-receive beam pair, a timing error, a frequency error, or combinations thereof.

<FIG> shows a block diagram <NUM> of a communications manager <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The communications manager <NUM> may be an example of aspects of a communications manager <NUM>, a communications manager <NUM>, or a communications manager <NUM> described herein. The communications manager <NUM> may include a configuration manager <NUM>, a TRP selection manager <NUM>, a TRS manager <NUM>, a beam manager <NUM>, a measurement component <NUM>, and an aperiodic monitoring manager <NUM>. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The configuration manager <NUM> may identify a set of TRPs that transmit joint communications to the UE, where each TRP of the set of TRPs has a separate cell identification. In some examples, the configuration manager <NUM> may receive configuration information from at least a first TRP of the set of TRPs that indicates the subset of TRPs that are to transmit the periodic TRSs, and where the determining is based on the configuration information.

In some examples, the configuration manager <NUM> may receive configuration information from at least a first TRP that indicates one or more of the predetermined number of TRPs that are to be selected as the subset of TRPs, or a RSRP threshold value for selecting one or more TRPs whose RSRP is higher than or equal to the RSRP threshold value as the subset of TRPs. In some cases, the configuration information is received in one or more of RRC signaling, a MAC-CE, or DCI from at least the first TRP.

The TRP selection manager <NUM> may determine a subset of the set of TRPs that are to transmit periodic TRSs. In some examples, the TRP selection manager <NUM> may select a predetermined number of TRPs from the set of TRPs as the subset of TRPs based on an ordering of the RSRP from each TRP.

The TRS manager <NUM> may monitor, based on the determining, for one or more TRSs from the subset of TRPs. In some examples, the TRS manager <NUM> may transmit a request to at least a first TRP to receive the periodic TRSs from the subset of TRPs. In some examples, two or more joint TRSs are transmitted by different groups of TRPs, and where each different group of TRPs is associated with a different cell identification. In some cases, the request is transmitted to at least the first TRP in a UCI transmission, a MAC-CE, in a RRC signaling transmission, in a UE assistance information feedback transmission, or any combinations thereof.

In some cases, the subset of TRPs is a first subset of TRPs, and where a second subset of the set of TRPs transmits one or more aperiodic TRSs or periodic TRSs, and where the second subset of TRPs is non-overlapping with the first subset of TRPs. In some cases, at least one of the one or more aperiodic TRSs is a joint TRS that is transmitted by two or more TRPs. In some cases, the two or more TRPs that transmit the joint TRS have one or more common radio frequency components or a common oscillator.

The beam manager <NUM> may update one or more of a transmit-receive beam pair, a timing error, or a frequency error for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs. The measurement component <NUM> may measure a RSRP from each TRP of the set of TRPs.

The aperiodic monitoring manager <NUM> may monitor for one or more aperiodic TRSs from one or more TRPs of the second subset of TRPs. In some examples, the aperiodic monitoring manager <NUM> may receive a trigger that indicates to monitor for the one or more aperiodic TRSs, where the trigger is received from the first TRP having a different cell identification than at least a second TRP that transmits the one or more aperiodic TRSs.

In some cases, the trigger is received in a layer-one signal from the first TRP that dynamically indicates that the second TRP is to transmit the one or more aperiodic TRSs. In some cases, a set of resource sets are configured for a set of different aperiodic TRS configurations from a set of different TRPs, and where the trigger indicates an index value that is mapped to one of the set of resource sets. In some cases, at least one TRS resource set of the set of resource sets is associated with a group of two or more TRPs.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of or include the components of device <NUM>, device <NUM>, or a UE <NUM> as described herein. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager <NUM>, an I/O controller <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, and a processor <NUM>. These components may be in electronic communication via one or more buses (e.g., bus <NUM>).

The communications manager <NUM> may identify a set of TRPs that transmit joint communications to the UE, where each TRP of the set of TRPs has a separate cell identification, determine a subset of the set of TRPs that are to transmit periodic TRSs, monitor, based on the determining, for one or more TRSs from the subset of TRPs, and update one or more joint communications parameters for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs.

The memory <NUM> may include RAM and ROM.

The processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., the memory <NUM>) to cause the device <NUM> to perform various functions (e.g., functions or tasks supporting TRS techniques in wireless communications).

<FIG> shows a block diagram <NUM> of a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a base station <NUM> or TRP as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may identify a set of TRPs that transmit joint communications to at least a first UE, where each TRP of the set of TRPs has a separate cell identification, determine a subset of the set of TRPs that are to transmit periodic TRSs, and transmit, based on the determining, configuration information to at least the first UE that indicates the subset of TRPs that are to transmit the periodic TRSs. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

<FIG> shows a block diagram <NUM> of a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of aspects of a device <NUM>, or a base station <NUM> or TRP as described herein. The device <NUM> may include a receiver <NUM>, a communications manager <NUM>, and a transmitter <NUM>. The device <NUM> may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager <NUM> may be an example of aspects of the communications manager <NUM> as described herein. The communications manager <NUM> may include a joint communications manager <NUM>, a TRP selection manager <NUM>, and a configuration manager <NUM>. The communications manager <NUM> may be an example of aspects of the communications manager <NUM> described herein.

The joint communications manager <NUM> may identify a set of TRPs that transmit joint communications to at least a first UE, where each TRP of the set of TRPs has a separate cell identification.

The configuration manager <NUM> may transmit, based on the determining, configuration information to at least the first UE that indicates the subset of TRPs that are to transmit the periodic TRSs.

<FIG> shows a block diagram <NUM> of a communications manager <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The communications manager <NUM> may be an example of aspects of a communications manager <NUM>, a communications manager <NUM>, or a communications manager <NUM> described herein. The communications manager <NUM> may include a joint communications manager <NUM>, a TRP selection manager <NUM>, a configuration manager <NUM>, and an aperiodic monitoring manager <NUM>. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses).

In some examples, two or more joint TRSs are transmitted by different groups of TRPs, and where each different group of TRPs is associated with a different cell ID. In some cases, at least one of the one or more aperiodic TRSs is a joint TRS that is transmitted by two or more TRPs. In some cases, the two or more TRPs that transmit the joint TRS have one or more common radio frequency components or a common oscillator.

The TRP selection manager <NUM> may determine a subset of the set of TRPs that are to transmit periodic TRSs. In some cases, the first TRP is not included in the subset of TRPs.

The configuration manager <NUM> may transmit, based on the determining, configuration information to at least the first UE that indicates the subset of TRPs that are to transmit the periodic TRSs. In some cases, the configuration information is transmitted in one or more of RRC signaling, a MAC-CE, or DCI to at least the first UE. In some cases, the configuration information indicates that a predetermined number of the set of TRPs are to be selected as the subset of TRPs based on an ordering of a RSRP from each TRP of the set of TRPs.

The aperiodic monitoring manager <NUM> may receive, from the first UE, a request to receive the periodic TRSs from the subset of TRPs. In some examples, the aperiodic monitoring manager <NUM> may transmit a trigger to the first UE that indicates to monitor for the one or more aperiodic TRSs, where the trigger indicates the first UE is to monitor for at least one aperiodic TRS from a second TRP having a different cell identification than the first TRP. In some cases, the request is transmitted to at least the first TRP in a UCI transmission, a MAC-CE, in a RRC signaling transmission, in a UE assistance information feedback transmission, or any combinations thereof.

In some cases, the subset of TRPs is a first subset of TRPs, and where a second subset of the set of TRPs transmits one or more aperiodic TRSs or periodic TRSs, and where the second subset of TRPs is non-overlapping with the first subset of TRPs.

In some cases, the trigger is transmitted in a layer-one signal that dynamically indicates that the second TRP is to transmit the one or more aperiodic TRSs. In some cases, a set of resource sets are configured at the first UE for a set of different aperiodic TRS configurations from a set of different TRPs, and where the trigger indicates an index value that is mapped to one of the set of resource sets. In some cases, at least one TRS resource set of the set of resource sets is associated with a group of two or more TRPs.

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The device <NUM> may be an example of or include the components of device <NUM>, device <NUM>, or a base station <NUM> or TRP as described herein. The device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager <NUM>, a network communications manager <NUM>, a transceiver <NUM>, an antenna <NUM>, memory <NUM>, a processor <NUM>, and an inter-station communications manager <NUM>. These components may be in electronic communication via one or more buses (e.g., bus <NUM>).

The communications manager <NUM> may identify a set of TRPs that transmit joint communications to at least a first UE, where each TRP of the set of TRPs has a separate cell identification, determine a subset of the set of TRPs that are to transmit periodic TRSs, and transmit, based on the determining, configuration information to at least the first UE that indicates the subset of TRPs that are to transmit the periodic TRSs.

The processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor <NUM> may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., the memory <NUM>) to cause the device <NUM> to perform various functions (e.g., functions or tasks supporting TRS techniques in wireless communications).

<FIG> shows a flowchart illustrating a method <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a communications manager as described with reference to <FIG>. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special-purpose hardware.

At <NUM>, the UE may identify a set of TRPs that transmit joint communications to the UE, where each TRP of the set of TRPs has a separate cell identification. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a configuration manager as described with reference to <FIG>.

At <NUM>, the UE may determine a subset of the set of TRPs that are to transmit periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRP selection manager as described with reference to <FIG>.

At <NUM>, the UE may monitor, based on the determining, for one or more TRSs from the subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRS manager as described with reference to <FIG>.

At <NUM>, the UE may update one or more joint communications parameters for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a beam manager as described with reference to <FIG>. In some cases, the joint communications parameters may include one or more of a transmit-receive beam pair, a timing error, or a frequency error.

At <NUM>, the UE may receive configuration information from at least a first TRP of the set of TRPs that indicates the subset of TRPs that are to transmit the periodic TRSs, and where the determining is based on the configuration information. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a configuration manager as described with reference to <FIG>. In some cases, the configuration information is received in one or more of RRC signaling, a MAC-CE, or DCI from at least the first TRP.

At <NUM>, the UE may update one or more joint communications parameters for joint communications with the set of TRPs based on the one or more TRSs from the subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a beam manager as described with reference to <FIG>.

At <NUM>, the UE may receive configuration information from at least a first TRP that indicates one or more of the predetermined number of TRPs that are to be selected as the subset of TRPs, or a RSRP threshold value for selecting one or more TRPs whose RSRP is higher than or equal to the RSRP threshold value as the subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a configuration manager as described with reference to <FIG>.

At <NUM>, the UE may measure a reference signal received power (RSRP) from each TRP of the set of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a measurement component as described with reference to <FIG>.

At <NUM>, the UE may select a predetermined number of TRPs from the set of TRPs as the subset of TRPs based on an ordering of the RSRP from each TRP. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRP selection manager as described with reference to <FIG>.

At <NUM>, the UE may monitor, based on the selecting, for one or more TRSs from the subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRS manager as described with reference to <FIG>.

At <NUM>, the UE may determine a first subset of the set of TRPs that are to transmit periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRP selection manager as described with reference to <FIG>.

At <NUM>, the UE may monitor, based on the determining, for one or more periodic TRSs from the first subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRS manager as described with reference to <FIG>.

At <NUM>, the UE may update one or more of a transmit-receive beam pair, a timing error, or a frequency error for joint communications with the set of TRPs based on the one or more TRSs from the first subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a beam manager as described with reference to <FIG>.

At <NUM>, the UE may identify a second subset of the set of TRPs transmits one or more aperiodic TRSs or periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRS manager as described with reference to <FIG>. In some cases, the second subset of TRPs is non-overlapping with the first subset of TRPs.

At <NUM>, the UE may receive a trigger that indicates to monitor for the one or more aperiodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by an aperiodic monitoring manager as described with reference to <FIG>. In some cases, the trigger is received from the first TRP having a different cell identification than at least a second TRP that transmits the one or more aperiodic TRSs. In some cases, the trigger is received in a layer-one signal from the first TRP that dynamically indicates that the second TRP is to transmit the one or more aperiodic TRSs.

At <NUM>, the UE may monitor for one or more aperiodic TRSs from one or more TRPs of the second subset of TRPs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by an aperiodic monitoring manager as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> that supports TRS techniques in wireless communications in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or TRP or its components as described herein. For example, the operations of method <NUM> may be performed by a communications manager as described with reference to <FIG>. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

At <NUM>, the base station may identify a set of TRPs that transmit joint communications to at least a first UE, where each TRP of the set of TRPs has a separate cell identification. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a joint communications manager as described with reference to <FIG>.

At <NUM>, the base station may determine a subset of the set of TRPs that are to transmit periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRP selection manager as described with reference to <FIG>.

At <NUM>, the base station may transmit, based on the determining, configuration information to at least the first UE that indicates the subset of TRPs that are to transmit the periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a configuration manager as described with reference to <FIG>.

At <NUM>, the base station may determine a first subset of the set of TRPs that are to transmit periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a TRP selection manager as described with reference to <FIG>.

At <NUM>, the base station may transmit, based on the determining, configuration information to at least the first UE that indicates the first subset of TRPs that are to transmit the periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a configuration manager as described with reference to <FIG>.

At <NUM>, the base station may identify a second subset of the set of TRPs transmits one or more aperiodic TRSs or periodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by an aperiodic monitoring manager as described with reference to <FIG>. In some cases, the second subset of TRPs is non-overlapping with the first subset of TRPs.

At <NUM>, the base station may transmit a trigger to the first UE that indicates to monitor for the one or more aperiodic TRSs. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by an aperiodic monitoring manager as described with reference to <FIG>. In some cases, the trigger indicates the first UE is to monitor for at least one aperiodic TRS from a second TRP having a different cell identification than the first TRP.

For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these.

A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

For example, an example step that is described as "based on condition A" may be based on both a condition A and a condition B without departing from the scope of the present disclosure.

The term "example" used herein means "serving as an example, instance, or illustration," and not "preferred" or "advantageous over other examples. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

Claim 1:
A method for wireless communication at a user equipment, UE, comprising:
identifying (<NUM>) a set of transmission-reception points that transmit joint communications to the UE, wherein each transmission-reception point of the set of transmission-reception points has a separate cell identification;
determining (<NUM>) a subset of the set of transmission-reception points that are to transmit periodic tracking reference signals, wherein the subset of transmission-reception points have a relatively large contribution to the signals received at the UE;
monitoring (<NUM>), based at least in part on the determining, for one or more tracking reference signals from the subset of transmission-reception points; and
updating (<NUM>) one or more joint communications parameters for joint communications with the set of transmission-reception points based at least in part on the one or more tracking reference signals from the subset of transmission-reception points.