QCL indication by UE-beam based tagging

A UE my receiving an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam. The UE may tag the BPL based on the UE receive beam. The UE may take one or more actions associated with the tagged BPL.

INTRODUCTION

Aspects of the present disclosure relate to wireless communications, and more particularly, quasi co-location (QCL) indication based on UE beam tagging.

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. An example of an emerging telecommunication standard is new radio (NR), for example, 5G radio access. NR is a set of enhancements to the LTE mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

As described herein, certain wireless systems may employ directional beams for transmission and reception.

Certain aspects of the present disclosure provide a method for wireless communication that may be performed, for example, by a UE. The method includes receiving an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam, tagging the BPL based on the UE receive beam, and taking one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide a method for wireless communication that may be performed, for example, by a BS. The method includes transmitting an indication of a beam pair link (BPL), wherein the BPL comprises a BS transmit beam and a corresponding user equipment (UE) receive beam, receiving an indication of a tag assigned to the BPL based on the UE receive beam, and taking one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide an apparatus for wireless communication that may be performed, for example, by a UE. The apparatus includes means for receiving an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam, means for tagging the BPL based on the UE receive beam, and means for taking one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide an apparatus for wireless communication that may be performed, for example, by a BS. The apparatus includes means for transmitting an indication of a beam pair link (BPL), wherein the BPL comprises a BS transmit beam and a corresponding user equipment (UE) receive beam, means for receiving an indication of a tag assigned to the BPL based on the UE receive beam, and means for taking one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide an apparatus for wireless communication that may be performed, for example, by a UE. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to receive an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam, tag the BPL based on the UE receive beam, and take one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide an apparatus for wireless communication that may be performed, for example, by a BS. The apparatus includes at least one processor and a memory coupled to the at least one processor. The at least one processor is configured to transmit an indication of a beam pair link (BPL), wherein the BPL comprises a BS transmit beam and a corresponding user equipment (UE) receive beam, receive an indication of a tag assigned to the BPL based on the UE receive beam, and take one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide a computer readable medium storing computer executable instructions thereon for causing a UE to receive an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam, tag the BPL based on the UE receive beam, and take one or more actions associated with the tagged BPL.

Certain aspects of the present disclosure provide a computer readable medium storing computer executable instructress thereon for causing a BS transmit an indication of a beam pair link (BPL), wherein the BPL comprises a BS transmit beam and a corresponding user equipment (UE) receive beam, receive an indication of a tag assigned to the BPL based on the UE receive beam, and take one or more actions associated with the tagged BPL.

Aspects generally include methods, apparatus, systems, computer readable mediums, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for new radio (NR) (new radio access technology or 5G technology).

mmW communications bring gigabit speeds to cellular networks, due to availability of large amounts of bandwidth. The unique challenges of heavy path-loss faced by millimeter-wave systems necessitate new techniques such as hybrid beamforming (analog and digital), which are not present in 3G and 4G systems. Hybrid beamforming may enhance link budget/signal to noise ratio (SNR) that may be exploited during the RACH.

Spectrum bands in high frequencies (e.g., 28 GHz, may be referred to as mmW (or mmWave)) provide large bandwidths capable of delivering multi-Gbps data rates, as well as extremely dense spatial reuse which may increase capacity. Traditionally, these higher frequencies were not robust enough for indoor/outdoor mobile broadband applications due to high propagation loss and susceptibility to blockage (e.g., from buildings, humans, and the like).

Despite these challenges, at the higher frequencies in which mmW operate, small wavelengths enable a large number of antenna elements in a relatively small form factor. Unlike microwave links, which may cast very wide footprints, reducing the achievable amount of reuse of the same spectrum within a geographical area, mmW links cast very narrow beams (for example, beams may have a narrow angle). This characteristic of mmW may be leveraged to form directional beams that may send and receive more energy to overcome propagation and path loss challenges.

These narrow directional beams can also be utilized for spatial reuse. This is one of the key enablers for utilizing mmW for mobile broadband services. In addition, the non-line-of-site (NLOS) paths (e.g., reflections from nearby building) can have very large energies, providing alternative paths when line-of-site (LOS) paths are blocked.

With more antenna elements and narrow beams, it becomes increasingly vital to transmit signals in the appropriate direction, in an effort to maximize the received signal energy at the UE.

EXAMPLE WIRELESS COMMUNICATIONS SYSTEM

FIG.1illustrates an example wireless network100in which aspects of the present disclosure may be performed. According to an example, the wireless network may be a NR or 5G network which may support mmW communication. mmW communication depends on beamforming to meet link margin. mmW communication may use directional beamforming, so transmission of signaling is directional. Accordingly, a transmitter may focus transmission energy in a certain narrow direction (e.g., beams may have a narrow angle), as illustrated inFIG.7. A receiving entity may use receiver beamforming to receive the transmitted signaling.

UEs120may be configured to perform the operations1100and methods described herein for UE beam-based tagging. BS110may comprise a transmission reception point (TRP), Node B (NB), 5G NB, access point (AP), new radio (NR) BS, Master BS, primary BS, etc.). The NR network100may include the central unit. The BS may be configured to perform the operations1200and methods described herein for UE beam-based tagging.

As illustrated inFIG.1, the wireless network100may include a number of base stations (BSs)110and other network entities. A BS may be a station that communicates with user equipments (UEs). Each BS110may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and next generation NodeB (gNB), new radio base station (NR BS), 5G NB, access point (AP), or transmission reception point (TRP) may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in wireless communication network100through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

Wireless network100may be a heterogeneous network that includes BSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network100. For example, macro BS may have a high transmit power level (e.g.,20Watts) whereas pico BS, femto BS, and relays may have a lower transmit power level (e.g., 1 Watt).

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR. NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

InFIG.1, a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A finely dashed line with double arrows indicates interfering transmissions between a UE and a BS.

FIG.2illustrates an example logical architecture of a distributed Radio Access Network (RAN)200, which may be implemented in the wireless communication network100illustrated inFIG.1. A 5G access node206may include an access node controller (ANC)202. ANC202may be a central unit (CU) of the distributed RAN200. The backhaul interface to the Next Generation Core Network (NG-CN)204may terminate at ANC202. The backhaul interface to neighboring next generation access Nodes (NG-ANs)210may terminate at ANC202. ANC202may include one or more transmission reception points (TRPs)208(e.g., cells, BSs, gNBs, etc.).

The TRPs208may be a distributed unit (DU). TRPs208may be connected to a single ANC (e.g., ANC202) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, TRPs208may be connected to more than one ANC. TRPs208may each include one or more antenna ports. TRPs208may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The logical architecture of distributed RAN200may support fronthauling solutions across different deployment types. For example, the logical architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The logical architecture of distributed RAN200may share features and/or components with LTE. For example, next generation access node (NG-AN)210may support dual connectivity with NR and may share a common fronthaul for LTE and NR.

The logical architecture of distributed RAN200may enable cooperation between and among TRPs208, for example, within a TRP and/or across TRPs via ANC202. An inter-TRP interface may not be used.

Logical functions may be dynamically distributed in the logical architecture of distributed RAN200. As will be described in more detail with reference toFIG.5, the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU (e.g., TRP208) or CU (e.g., ANC202).

FIG.3illustrates an example physical architecture of a distributed Radio Access Network (RAN)300, according to aspects of the present disclosure. A centralized core network unit (C-CU)302may host core network functions. C-CU302may be centrally deployed. C-CU302functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU)304may host one or more ANC functions. Optionally, the C-RU304may host core network functions locally. The C-RU304may have distributed deployment. The C-RU304may be close to the network edge.

FIG.4illustrates example components of the BS110and UE120illustrated inFIG.1, which may be used to implement aspects of the present disclosure. The BS may include a TRP or gNB.

According to an example, antennas452, DEMOD/MOD454, processors466,458,464, and/or controller/processor480of the UE120may be used to perform the operations described herein and illustrated with reference toFIGS.7-12. According to an example, antennas434, DEMOD/MOD432, processors430,420,438and/or controller/processor440of the BS110may be used to perform the operations described herein and illustrated with reference toFIGS.11-12.

As an example, one or more of the antennas452, DEMOD/MOD454, processors466,458,464, and/or controller/processor480of the UE120may be configured to perform the operations described herein for UE beam-based tagging. Similarly, one or more of the434, DEMOD/MOD432, processors430,420,438and/or controller/processor440of the BS110may be configured to perform the operations described herein.

The controllers/processors440and480may direct the operation at the base station110and the UE120, respectively. The processor440and/or other processors and modules at the BS110may perform or direct the execution of processes for the techniques described herein. The memories442and482may store data and program codes for BS110and UE120, respectively. A scheduler444may schedule UEs for data transmission on the downlink and/or uplink.

FIG.5illustrates a diagram500showing examples for implementing a communications protocol stack, according to aspects of the present disclosure. The illustrated communications protocol stacks may be implemented by devices operating in a wireless communication system, such as a 5G system (e.g., a system that supports uplink-based mobility). Diagram500illustrates a communications protocol stack including a Radio Resource Control (RRC) layer510, a Packet Data Convergence Protocol (PDCP) layer515, a Radio Link Control (RLC) layer520, a Medium Access Control (MAC) layer525, and a Physical (PHY) layer530. In various examples, the layers of a protocol stack may be implemented as separate modules of software, portions of a processor or ASIC, portions of non-collocated devices connected by a communications link, or various combinations thereof. Collocated and non-collocated implementations may be used, for example, in a protocol stack for a network access device (e.g., ANs, CUs, and/or DUs) or a UE.

A second option505-bshows a unified implementation of a protocol stack, in which the protocol stack is implemented in a single network access device. In the second option, RRC layer510, PDCP layer515, RLC layer520, MAC layer525, and PHY layer530may each be implemented by the AN. The second option505-bmay be useful in, for example, a femto cell deployment.

Regardless of whether a network access device implements part or all of a protocol stack, a UE may implement an entire protocol stack as shown in505-c(e.g., the RRC layer510, the PDCP layer515, the RLC layer520, the MAC layer525, and the PHY layer530).

In LTE, the basic transmission time interval (TTI) or packet duration is the1ms subframe. In NR, a subframe is still1ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (e.g., 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing.

FIG.6is a diagram showing an example of a frame format600for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots depending on the subcarrier spacing. Each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols) depending on the subcarrier spacing. The symbol periods in each slot may be assigned indices. A mini-slot is a subslot structure (e.g., 2, 3, or 4 symbols). A mini-slot, which may be referred to as a sub-slot structure, refers to a transmit time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols).

In NR, a synchronization signal (SS) block is transmitted. The SS block includes a PSS, a SSS, and a two symbol PBCH. The SS block can be transmitted in a fixed slot location, such as the symbols0-3as shown inFIG.6. The PSS and SSS may be used by UEs for cell search and acquisition. The PSS may provide half-frame timing, the SS may provide the CP length and frame timing. The PSS and SSS may provide the cell identity. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SS blocks may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), other system information (OSI) can be transmitted on a physical downlink shared channel (PDSCH) in certain subframes.

EXAMPLE BEAM PROCEDURE

As noted above, in millimeter wave (mmW) cellular systems, beam forming may be needed to overcome high path-losses. As described herein, beamforming may refer to establishing a link between a BS and UE, wherein both of the devices form a beam corresponding to each other. Both the BS and the UE find at least one adequate beam to form a communication link. A BS-beam and UE-beam form what is known as a beam pair link (BPL). As an example, on the DL, a BS may use a transmit beam and a UE may use a receive beam corresponding to the BS transmit beam to receive the transmission. The combination of a transmit beam and corresponding receive beam may be a BPL.

As a part of beam management, beams which are used by BS and UE have to be refined from time to time because of changing channel conditions, for example, due to movement of the UE or other objects. Additionally, the performance of a BPL may be subject to fading due to Doppler spread. Because of changing channel conditions over time, the BPL may be periodically updated or refined. Accordingly, it may be beneficial if the BS and the UE monitor beams and new BPLs.

At least one BPL has to be established for network access. As described above, new BPLs may need to be discovered later on for different purposes. The network may decide to use different BPLs for different channels, for communicating with different BSs (TRPS), or as fall-back in case an existing BPL fails.

The UE typically monitors the quality of a BPL and the network may refine a BPL from time to time.

FIG.7illustrates example700for BPL discovery and refinement. In 5G-NR, the P1, P2, and P3procedures are used for BPL discovery and refinement. The network uses a P1procedure to enable the discovery of new BPLs. In the P1procedure, as illustrated inFIG.7the TRP transmits different symbols of a reference signal, each beam formed in a different spatial direction such that several (most, all) relevant places of the cell are reached. Stated otherwise, the TRP transmits beams using different transmit beams over time in different directions.

For successful reception of at least a symbol of this “P1-signal”, the UE has to find an appropriate receive beam. It searches using its available receive beams and applying a different UE-beam during each occurrence of the periodic P1-signal.

Once the UE has succeeded in receiving a symbol of the P1-signal it has discovered a BPL. The UE may not want to wait until it has found the best UE receive beam, since this may delay further actions. The UE may measure the reference signal receive power (RSRP) and report the symbol index together with the RSRP to the BS. Such a report will typically contain the findings of one or more BPLs.

In an example, the UE may determine a received signal having a high RSRP. The UE may not know which beam the BS used to transmit; however, the UE may report to the TRP the time at which it observed the signal having a high RSRP. The TRP may receive this report and may determine which TRP beam it used at the given time.

The TRP may then offer P2and P3procedures to refine an individual BPL. The P2procedure refines the TRP-beam of a BPL. The TRP may transmit a few symbols of a reference signal with different TRP-beams that are spatially close to the TRP-beam of the BPL (the TRP performs a sweep using neighboring beams around the selected beam). In P2, the UE keeps its receive beam constant. Thus, while the UE uses the same beam as in the BPL (as illustrated in P2procedure inFIG.7). The TRP-beams used for P2may be different from those used in P1in that they may be spaced closer together or they may be more focused. The UE may measure the RSRP for the various TRP-beams and indicate the best one to the TRP.

The P3procedure refines the UE-beam of a BPL (see P3procedure inFIG.7). While the TRP-beam stays constant, the UE scans using different receive beams (the UE performs a sweep using neighboring beams). The UE may measure the RSRP of each beam and identify the best UE-beam. Afterwards, the UE may use the best UE-beam for the BPL and report the RSRP to the TRP.

Overtime, the TRP and UE establish several BPLs. When the TRP transmits a certain channel or signal, it lets the UE know which BPL will be involved, such that the UE may tune in the direction of the correct UE receive beam before the signal starts. In this manner, every sample of that signal or channel may be received by the UE using the correct receive beam. In an example, the TRP may indicate for a scheduled signal (SRS, CSI-RS) or channel (PDSCH, PDCCH, PUSCH, PUCCH) which BPL is involved. In NR this information is called QCL indication.

Two antenna ports are QCL if properties of the channel over which a symbol on one antenna port is conveyed may be inferred from the channel over which a symbol on the other antenna port is conveyed. QCL supports, at least, beam management functionality, frequency/timing offset estimation functionality, and RRM management functionality.

The TRP may use a BPL which the UE has used to receive a signal in the past. The transmit beam for the signal to be transmitted and the previously-received signal both point in a same direction or are QCL. The QCL indication may be needed by the UE (in advance of signal to be received) such that the UE may use a correct corresponding receive beam for each signal or channel. Some QCL indications may be needed from time to time when the BPL for a signal or channel changes and some QCL indications are needed for each scheduled instance. The QCL indication may be transmitted in the downlink control information (DCI) which may be part of the PDCCH channel. Because DCI is needed to control the information, it may be desirable that the number of bits needed to indicate the QCL is not too big. The QCL may be transmitted in a medium access control-control element (MAC-CE) or radio resource control (RRC) message.

According to one example, whenever the UE reports a BS beam that it has received with sufficient RSRP, and the BS decides to use this BPL in the future, the BS assigns it a BPL tag. Accordingly, two BPLs having different BS beams may be associated with different BPL tags. BPLs that are based on the same BS beams may be associated with the same BPL tag. Thus, according to this example, the tag is a function of the BS beam of the BPL.

EXAMPLE UE-BEAM BASED TAGGING

In accordance with aspects of the present disclosure, a QCL indication or tag which is a function of the UE-beam of the BPL is used. Thus, two BPLs which have different BS-beams but the same UE-beam may be labeled by the same tag. The BS may keep a table that contains the set of all BS-beams that are mapped to the same BPL tag (e.g., mapped to the same UE-beam). Advantageously, these BS-beams offer flexibility to the BS. For example, for downlink transmission, the BS may switch between BS-beams associated with a same tag without having to signal a message to the UE. This allows for very fast switching by the BS, which may be advantageous, for example, in the scenario of sudden beam failure. Further, for downlink communication, the BS may use BS-beams associated with a same tag for MIMO transmission with transmit diversity. According to an example, the BS may simultaneously transmit signals on multiple beams mapped to a same tag to achieve transmit diversity gain.

FIGS.8-10, which illustrate Tables1-3, describe an example of using UE-beam based tagging. The UE is configured to transmit reports about BS-beam measurements for reference signals used for a P1procedure. The UE reports only BS-beams it receives with a satisfactory RSRP (for example, RSRP >threshold value, or a configurable number of beams associated with a highest RSRP). Each reported item constitutes a BPL.

While in principle all reported BS-beams and the corresponding UE-beams may be candidates for BPLs, the BS may decide which beams to pursue further. The BS signals to the UE, if and which reported items are new BPLs (e.g., 1 bit per new BPL). The BS may also signal the tags of BPLs it no longer wants to use. The UE may receive this report and determine if each BPL has a same of different UE-beam and a BPL identified in the active pool. If BPLs have a same UE-beam, the UE may use a same tag with the BPLs. BPLs having a different UE-beam may use a different tag.

Thereafter, and as will be described in more detail with reference toFIGS.8-10, the UE signals to the BS the tags for the newly identified BPLs. If two or more BPLs are best received by the same UE-beam, they may be labeled by the same tag. In this manner, if a new BPL and an established BPL are associated with the same UE-beams, the new BPL is assigned the same tag of the established BPL.

FIG.8illustrates an example800of BPL tags after discovery and deletion, according to aspects of the present disclosure. As shown in line1, after discovery, the UE knows it used UE-beam2to receive a signal. The UE may not know that BS used BS-beam1. The UE may report receiving a signal using UE-beam2at a specific time. Assuming the BS would like to consider this BPL, the UE may assign the BPL as tag0. Next, as shown in line2, in discovery, the UE knows it used beam4to receive a signal at a certain time. The UE may not know that the BS used beam3. If the BS would like to consider this BPL, the UE may assign it tag1. Because the UE beams are different in line2as compared to line1, the tags are different.

Next, as shown in line3, the UE may receive a signal using beam2. The UE may transmit this information to the BS. Because UE beam2was also used to receive BS-beam1in line1, the BS will tag BPL (5,2) of line3with tag0, similar to line1, which also used UE-beam2. In this manner, two BPLs having the same UE-beam are assigned a same tag.

At a later point, the BS may decide that it may no longer want to pursue the BPL (3,4) as shown in line4. The BS may transmit a message to the UE to delete this tag. Accordingly BPL (3,4) may not be associated with a tag1. Assuming tag1is not associated with another BPL, the tag is available for reuse with another BPL based on the UE-beam. Accordingly, tag1is available for the BPL (8,3) as shown in line5.

According to aspects, it is possible to reduce the amount of signaling, by instructing the UE to send a message only if a new BPL and either another new BPL or an established BPL share the same UE-beam. This may be possible, since in all other cases, each new BPL will be assigned a new tag. Both, the BS and the UE know which tags are in use for labeling BPLs. There is a pool of unused tags and the airlink specification may outline in which order tags from the pool of unused tags are assigned to new BPLs. The BS may predict which tags the UE may assign to the new BPLs and hence there is no need for the UE to signal that information.

FIG.9illustrates an example900of BPL tags after the P2procedure, according to aspects of the present disclosure. The DCI for the P2procedure may contain the tag of the BPL for which the BS-beam is going to be refined. After the P2sweep, the UE indicates the best BS-beam and the associated RSRP. The procedure updates the BS-beam of the BPL while the UE-beam remains the same. The tag associated with the (updated) BPL remains the same. Table2illustrates an example. As shown in line4, after P2on BPL (3,4), the UE may determine that a symbol transmitted via BS-beam6is a better beam as compared to BS-beam3. The new, improved BPL will be (6,4). Notably, the same UE beam is used for this BPL, so the tag (tag1) remains the same despite the change in the BS beam.

As shown in line5, after P2on BPL (1,2), the BS-beam may be updated from1to7. The BS may receive an indication that a symbol transmitted via BS-beam7is a better than BS beam1. The BS may update the BS-beam associated with tag0to be BS-beam7.

FIG.10illustrates an example1000of BPL tags after the P3procedure. The DCI for the P3procedure will contain the tag of the BPL for which the UE-beam is going to be refined. During the P3sweep, the UE evaluates the performance of different UE-beams while the BS-beam remains constant. If the current UE-beam is still the best, nothing changes. The UE does not need to signal anything to the BS.

However, if another UE-beam turns out to better than the current UE-beam, then two cases may be differentiated. In the first case, the UE associates the tag with only one BS-beam. In this case, the tag of the updated BPL can stay the same. The updated BPL consists of the new UE-beam and the current BS-beam. The UE may not need to signal anything to the BS, except perhaps the RSRP for the updated BPL.

In the second case, the UE associates the tag with more than one BS-beam. In this case, the updated BPL consists of the new UE-beam and the BS-beam used for the P3procedure. This BPL needs to be labeled with a new tag since it is now different from the other BPLs consisting of the old UE-beam and one of the remaining BS-beams. The UE will report the new tag to the BS.

It is clear that the UE has no way of knowing whether the BS associates more than one BS-beam with the same BPL tag. Therefore, a “new tag request bit” may be included in the DCI for a P3procedure. It conveys to the UE whether a new tag needs to be issued in case the UE-beam needs to be updated. Table3illustrates an example.

As shown on line4, the BS may enable a P3procedure on BPL (3,4). The BS keeps beam3constant and the UE uses different beams around UE-beam4. The UE determines that beam5is better than beam4. The tag for the new BPL (3,5) may still be the same because the tag1was previously associated with a single BS-beam3. Accordingly, the new tag request may be set to 0.

As shown on line5, the BS may enable a P3procedure on BPL (1,2). The UE may determine UE-beam3is better than UE-beam2. Accordingly BPL (1,2) may be replaced with BPL (1,3). In response to the updated UE-beam, the new tag request may be set to 1. This is because BPL (1,2) and (BPL (5,2) were previously associated with tag0. Stated otherwise, the new tag request is set to1because the tag0was associated with two different BS-beams. BPL (1,2) is updated, because of P3, to BPL (1,3). A new tag is needed to so that each BPL tag is associated with a same UE-beam. Accordingly, the updated BPL (1,3) may be associated with tag2.

FIG.11illustrates example operations1100which may be performed by a UE in accordance with aspects of the present disclosure. At1102, the UE may receive an indication of a beam pair link (BPL), wherein the BPL comprises a base station (BS) transmit beam and a corresponding UE receive beam. At1104, the UE may tag the BPL based on the UE receive beam. At1106, the UE may take one or more actions associated with the tagged BPL.

According to aspects, taking the one or more actions includes transmitting, to the BS, an indication of the tagged BPL. Additionally or alternatively, according to aspects, taking the one or more actions includes receiving signaling in accordance with the BPL.

Additionally or alternatively, taking the one or more actions includes receiving a downlink transmission indicating beam refinement of the BS transmit beam of the tagged BPL, for example, during the P2procedure. During the refinement, the UE may receive signaling, transmitted from one or more neighboring beams of the BS transmit beam, using a single UE receive beam, the UE may determine a signal quality associated with transmissions from one or more of the neighboring beams of the BS transmit beam, and indicate to the BS a recommended BS transmit beam corresponding to the UE receive beam of the tagged BPL based, at least in part, on the determined signal quality.

Additionally or alternatively taking the one or more actions includes receiving a downlink transmission indicating beam refinement of the UE receive beam of the tagged BPL, such as during a P3procedure. During the refinement, the UE may receive signaling from the BS transmit beam via one or more receive beams neighboring the corresponding UE receive beam of the BPL, may determine a signal quality associated with one or more of the neighboring beams of the UE receive beam, and update the UE receive beam corresponding to the BS transmit beam of the tagged BPL based at least in part, on the determined signal quality. According to aspects, the UE may determine whether a different tag is needed in response to the updated UE receive beam. If a different tag is needed, the UE may compute the different tag, indicate the different tag to the BS, and assign the different tag to the updated UE receive beam and BS transmit beam. According to aspects, the different tag includes one of: a new tag or a currently-used tag.

According to aspects, taking the one or more actions associated with the tagged BPL includes transmitting, to the BS, an indication of the tagged BPL in response to at least one of: a new BPL or an established BPL sharing a same UE receive beam with the new BPL. Additionally or alternatively, taking one or more actions associated with the tagged BPL includes receiving, from the BS, a message to remove a tag and its current association to one or more BPLs and in response to the message, making the removed tag available for assignment to one or more new BPLs.

FIG.12illustrates example operations1200which may be performed by a BS in accordance with aspects of the present disclosure. At1202, the BS may transmit an indication of a beam pair link (BPL), wherein the BPL comprises a BS transmit beam and a corresponding user equipment (UE) receive beam. At1204, the BS receives an indication of a tag assigned to the BPL based on the UE receive beam. At1206, the BS takes one or more actions associated with the tagged BPL.

According to aspects, the BS receives, from the UE, an indication of the tagged BPL. According to aspects, taking the one or more actions includes transmitting signaling in accordance with the BPL. According to aspects, the tag includes a beam indication.

According to aspects, taking the one or more actions includes transmitting a downlink assignment indicating beam refinement of the BS transmit beam of the tagged BPL such as a P2procedure. During the refinement, the BS may transmit signaling, using one or more neighboring beams of the BS transmit beam and the BS may receive a recommendation for an updated BS transmit beam corresponding to the UE receive beam of the tagged BPL, wherein the updated BS transmit beam and the corresponding UE receive beam are assigned the tag.

According to aspects, taking the one or more actions includes transmitting a downlink assignment indicating beam refinement of the UE receive beam of the tagged BPL, such as a P3procedure. During the refinement, the BS may transmit signaling using the BS transmit beam and may receive an updated tag, which maybe a new or the old tag corresponding to the BS transmit beam of the tagged BPL. The updated UE receive beam and the corresponding BS transmit beam are assigned one of the tag or an updated tag. According to aspects, the BS may transmit an indication for the updated tag in response to the updated UE receive beam and may receive the updated tag assigned to the updated UE receive beam and BS transmit beam.

According to aspects, taking the one or more actions associated with the tagged BPL includes receiving an indication of the tagged BPL in response to at least one of: a new BPL or an established BPL sharing a same UE receive beam with the new BPL. According to aspects, taking the one or more actions associated with the tagged BPL comprises signaling to the UE removal of a tag and its current association to one or more BPLs wherein the removed tag is available for future assignment to one or more new BPLs.

FIG.13depicts a communications device1300that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated inFIG.11. The communications device1300includes a processing system1302coupled to a transceiver1310. The transceiver1310is configured to transmit and receive signals for the communications device1300via an antenna1312, such as the various signals described herein. The processing system1302may be configured to perform processing functions for the communications device1300, including processing signals received and/or to be transmitted by the communications device1300.

The processing system1302includes a processor1304coupled to a computer-readable medium/memory1306via a bus1308. In certain aspects, the computer-readable medium/memory1306is configured to store computer-executable instructions that when executed by processor1304, cause the processor1304to perform the operations illustrated inFIG.11or other operations for performing the various techniques discussed herein.

In certain aspects, the processing system1302further includes a tagging component1314and a taking action component1316for performing the operations illustrated inFIG.11. In certain aspects, the processing system1302includes one or more of a determining component, indicating component, updating component, making a removed tag unavailable component, and/or other components configured to perform the operations described herein. The components1314and1316(and other non-illustrated components) may be coupled to the processor1304via bus1308. In certain aspects, the components1314and1316(and other non-illustrated components) may be hardware circuits. In certain aspects, the components1314and1316(and other non-illustrated components) may be software components that are executed and run on processor1304.

FIG.14depicts a communications device1400that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated inFIG.12. The communications device1400includes a processing system1402coupled to a transceiver1410. The transceiver1410is configured to transmit and receive signals for the communications device1400via an antenna1412, such as the various signals described herein. The processing system1402may be configured to perform processing functions for the communications device1400, including processing signals received and/or to be transmitted by the communications device1400.

The processing system1402includes a processor1404coupled to a computer-readable medium/memory1406via a bus1408. In certain aspects, the computer-readable medium/memory1406is configured to store computer-executable instructions that when executed by processor1404, cause the processor1404to perform the operations illustrated inFIG.12or other operations for performing the various techniques discussed herein.

In certain aspects, the processing system1402further includes a taking action component1414for performing the operations illustrated inFIG.12. In certain aspects, the processing system1402includes one or more of other (non-illustrated components) configured to perform the operations described herein. The component1414(and other non-illustrated components) may be coupled to the processor1404via bus1408. In certain aspects, the component1414(and other non-illustrated components) may be hardware circuits. In certain aspects, the component1414(and other non-illustrated components) may be a software component that is executed and run on processor1404.