EP4699230A1

EP4699230A1 - Method for overhead reduction for uplink precoder indication

Info

Publication number: EP4699230A1
Application number: EP23732346.4A
Authority: EP
Inventors: Jia-Hong Liou; Yushu Zhang
Original assignee: Google LLC
Current assignee: Google LLC
Priority date: 2023-05-12
Filing date: 2023-05-12
Publication date: 2026-02-25
Also published as: WO2024234140A1; CN121263968A

Abstract

Methods (400, 500) for devices such as user equipment, UEs, (110) and network entities, NEs, (120) in a wireless network provide mechanisms for overhead reduction for uplink precoder indication when some of the UE antenna port groups have substantially the same channel property. The channel property may be one or more of the quasi-co-location-related properties including delay spread, average delay, Doppler spread, Doppler shift, spatial transmission filter, or average gain. These mechanisms may be employed when operability of one or more antenna ports changes.

Description

METHOD FOR OVERHEAD REDUCTION FOR UPLINK PRECODER INDICATION

FIELD OF THE DISCLOSURE
This document generally describes methods and devices operating in wireless communication systems such as (but not limited to) the ones described in 5G standard documents, known as 3GPP communication systems. More particularly, the document refers to improving codebook-based transmissions by reducing overhead for uplink precoder indication.

BACKGROUND

Multiple input, multiple output (MIMO) technology for wireless communications refers to using multiple antennas both at the source (transmitter) and the destination (receiver) . Transmitter’s and receiver’s antennas are combined to minimize errors, reduce fading (thus, achieving a better signal-to-noise ratio) and improve the capacity of radio transmissions by enabling signals to reach destination via plural paths at the same time.
Beamforming (employed, for example, in 5^th generation mobile networks known as 5G) requires multiple antenna elements. The receiver does not need to know which physical antenna elements the transmitter uses, viewing the signal as emitted by an antenna port. In other words, an antenna port corresponds to one or more physical antenna elements. Transmissions from the same antenna port experience the same radio channel, whereas transmissions using different antenna ports typically experience different radio channels. However, transmissions using different antenna ports may experience similar radio channels (i.e., sharing some common characteristics) , such as, the quasi co-located, QCL, antenna ports. The radio channel characteristics that may be common to QCL antenna ports include Doppler shift, Doppler spread, average delay, delay spread, and spatial parameters.
A user equipment (UE) can transmit simultaneous uplink transmissions using different transmission configurations. Such transmission may be referred to as multi-panel (or multi-layer) uplink transmissions. A UE may have plural (e.g., two, four, eight or even sixteen) antennas in one array/panel, and the UE may have multiple arrays/panels which may be located at various locations of the UE. The different antennas, antenna panels, and/or beams cover different spatial directions. The UE may support coherent transmission from a group of antenna ports. Thus, the antenna ports within each antenna port group are well-calibrated relative to one another (the random phase error between every two antenna ports of an antenna port group being less than a threshold, e.g., 40°) .
The UEs may employ different parameters and techniques to prepare the data for transmission. For example, according to current 3GPP TS 38.212, when preparing data to be transmitted via a physical uplink shared channel (PUSCH) , a UE enables cyclic redundancy check (CRC) and/or a low-density parity check (LDPC) , and forms channel coding, rate matching, block concatenation, multiplexing, scrambling, modulation, layer mapping, precoding, and mapping to physical resource blocks. Typically, the network chooses the precoder for a precoder uplink transmission and signals the selected precoder to UE. The precoder maps one or more layers at the UE to one or more antenna ports.
Anticipating a PUSCH codebook-based transmission, the network (that is a network entity, NE, such a base station directly communicating with the UE) configures the UE to emit a set of sounding reference signal (SRS) for selecting the precoder. Based on the received SRSs, the NE indicates the precoder for uplink transmission, for example, as a combination of a transmission rank indicator (TRI) and a transmission precoder matrix indicator (TPMI) pointing to a pre-defined codebook.
The increasing number of UE antenna ports triggers an increase in the number of precoders (e.g., TRI/TPMI combinations) usable by each antenna port group. Conventionally, a precoder is indicated for each antenna port group actively used for an uplink transmission.
Additionally, currently, the precoder (s) used for generating an uplink codebook-based transmission is not updated when a UE-antenna operability changes.

SUMMARY

UEs and NEs according to various embodiments exchange information for reducing the number of indicated precoders when some of the UE antenna port groups have a same channel property (e.g., same quasi-co-location property including delay spread, average delay, Doppler spread, Doppler shift, spatial transmission filter, or average gain) . Thus, overhead reduction for uplink precoder indication may be achieved.
The UE may transmit UE capability information including the number of the UE antenna port groups and information on the UE antenna port groups having the same channel property. The NE may configure the UE to emit sounding reference signals for selecting precoder (s) in view of the UE capability information. The antenna port groups having the same channel property may meet an antenna arrangement criterion based on their location and orientation. The UE may report information relevant to status of the UE antenna port groups having the same channel property. The report may be configured and/or triggered by the network entity (which, optionally, may also specify a time domain manner of transmitting the report) . Alternatively or additionally, the UE may transmit the report upon detecting an event impacting one of the UE antenna port groups having the same channel property.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments.
Figure 1 illustrates a wireless communication system with a UE and an NE configured to enable reducing overhead for uplink precoder indication according to an embodiment.
Figures 2A, 2B, and 2C illustrate UE antenna port group arrangements.
Figure 3 is a signal diagram for implementing overhead reduction for uplink precoder indication according to an embodiment.
Figure 4 is a flowchart of a wireless communication method performed by a UE according to an embodiment.
Figure 5 is a flowchart of a wireless communication method performed by a network entity according to another embodiment.
Figures 6A, 6B, and 6C are examples of antenna port group information report for different types of UE antenna port group arrangements.
Figures 7A, 7B, 7C, and 7D illustrate an example of permutation-based UE report of supported or recommended antenna port group.

DETAILED DESCRIPTION

Methods and devices described in this section embody techniques related to codebook-based transmissions. Figure 1 illustrates a wireless communication system with an NE 110 and a UE 120 communicating wirelessly 101 and configured to enable reducing overhead for uplink precoder indication according to an embodiment. NE 110 may be a base station, BS, but more generally, the term “network entity” stands for a wireless device with a well-defined network functionality (e.g., BS’s functionality is connecting UEs to the core network including managing communications to and from the UEs) . NE 110 and UE 120 may include additional functions and interfaces omitted from Figure 1 in the interest of brevity. Signaling arrow 101 generally represents both uplink signals (from the UE to the NE) and downlink signals (from the NE to the UE) .
NE 110 as illustrated in Figure 1 may provide the functionality of an gNB (i.e., a 5G or 6G base station) . NE 110’s functionality may be distributed across multiple entities (e.g., a central unit, CU, a distributed unit, DU, and a radio unit, RU) . NE 110 includes antennas, an RF front end 111 and a transceiver 112 for communicating with UE 120 and other UEs and NEs. NE 110’s antennas and RF front end 211 can be tuned to one or more frequency bands (e.g., subcarriers) , for example as defined by 3GPP LTE, 5G NR, and 6G communication standards and implemented by transceiver 112.
NE 110 includes processor (s) 113 and computer-readable storage media (CRM) 114. Processor (s) 113 can include single or multiple-core processors, and CRM 114 includes any suitable memory/storage except propagating signals. For example, memory/storage can include random-access memory (RAM) , static RAM (SRAM) , dynamic RAM (DRAM) , non-volatile RAM (NVRAM) , read-only memory (ROM) , and/or flash memory. CRM 114 stores device data 115, which includes network scheduling data, radio resource management data, applications, and/or an operating system, which are executable by processor (s) 113 to enable wireless communication 101 with UE 120 as well as with other NEs and UEs.
CRM 114 also stores control signaling manager 116 and UE antenna port group precoder selector 117. Control signaling manager 116 causes NE 110 to perform various steps and actions for generating configuration instructions directing UE 120 to emit SRS for codebook selection and to use the same precoder indication for more than one antenna port group. UE antenna port group precoder selector 117 selects one or more precoders to be used by the UE in a manner conducive to reducing number of the uplink precoder indication (s) .
NE 110 also includes inter-base station interface 118 and core-network interface 119. Inter-base station interface 118 can be a standardized interface, such as an Xn and/or X2 interface, for exchanging user-plane and control-plane data with another NE (e.g., in case of a handover) . Core-network interface 119 enables NE’s user-plane data and control-plane information exchange with core network functions and/or entities.
UE 120 includes antennas connected to a radio frequency (RF) front end 121, and a transceiver 122. Transceiver 122 may be an LTE transceiver, a 5G NR transceiver, or another transceiver. The UE may include multiple transceivers. The antennas and RF front end 121 can be tuned to one or more frequency bands (e.g., subcarriers) , for example, as defined by 3GPP LTE, 5G NR, and 6G communication standards and implemented by respective transceivers. UE 120 also includes one or more precoders 123, one or more processor (s) 124, and computer-readable storage media (CRM) 125. Processor (s) 123 may be single or multiple-core processors, and CRM 125 includes any suitable memory/storage other than propagating signals. For example, memory/storage can include random-access memory (RAM) , static RAM (SRAM) , dynamic RAM (DRAM) , non-volatile RAM (NVRAM) , read-only memory (ROM) , and/or flash memory. CRM 125 stores device data 126 necessary for UE’s communications, manager of antenna group info 127 and identifier of UE antenna port group sharing a channel quality 128.
NE’s control signaling manager 116 and UE antenna port group precoder selector 117 as well as UE’s manager of antenna group info 127 and identifier of UE antenna port group sharing a channel quality 128 may be implemented not only as software but also as hardware logic and/or circuitry.
A wireless system such as the one schematically illustrated in Figure 1 may implement various techniques related to overhead reduction for uplink precoder indication.
The precoder for uplink transmission indicates the selected antenna ports of a group and the antenna combining phase for the selected ports. For example, for an 8-port UE, the precoderindicates using antenna ports {0, 2, 4, 6} which have the same phase (i.e., each “1” means that the respective antenna’s combining phase is 0°) .
The 3GPP standard documents define the uplink codebook term and lists predefined codebooks (for example, in 3GPP TS 38.211 subsection 6.3.1.5) , as well as the procedure for uplink codebook-based transmission schemes (for example, in 3GPP TS 38.214 subsection 6.1.1.1) . While antenna port quasi co-location (QCL) has been considered in the context of downlink procedures (for example, in 3GPP TS 38.214 subsection 5.1.5) , no similar considerations have been standardized in the context of uplink procedures.
Some distinct types of the antenna arrangements may be defined as follows. UE 220 in Figure 2A has antenna port groups 221, 222, 223, and 224 that share the same spatial orientation and are placed within a small antenna port group area. Accordingly, UE 220 has a type 1 antenna arrangement. The small antenna port group area may be defined by a horizontal and/or vertical inter-antenna interval of less than kλ, where k< 4 (or other small integer value) and λ is a representative wavelength for the transmission. Alternatively, antennas in groups 221, 222, 223, 224 having a first polarization (e.g., “/” ) may form a first antenna port group and antennas in groups 221, 222, 223, 224 having a second polarization (e.g., “\” , distinct from the first polarization) form a second antenna port group. The antenna ports in different antenna port groups could share the same channel property (e.g., the antenna port groups share the same QCL properties such as delay spread, average delay, Doppler spread, Doppler shift, spatial transmission filter and average gain) .
UE 230 illustrated in Figure 2B has a type 2 antenna arrangement. Antenna ports in different groups 231, 232, 233, and 234 are placed with a larger antenna port group spacing (e.g., the antenna port group spacing in horizontal and vertical could be larger than kλ, that is k>4) . Alternatively, the antenna port group may have different spatial orientations. In this type of arrangement, the channel properties observed by the antenna ports are likely different for the different antenna port groups.
UE 240 illustrated in Figure 2C has a type 3 antenna arrangement with antenna port groups 241 and 242 placed in a small antenna port group area (on a first side of UE 240) , and antenna port groups 243 and 244 placed in another small antenna port group area (on a second side of UE 240, opposite to the first side) . Antenna port groups 241, 242, 243, and 244 may have the same spatial orientation. Antenna port groups 241 and 242 are likely to observe similar channel properties. Antenna ports groups 243 and 244 are also likely to observe similar channel properties, but the channel properties observed by antenna ports groups 243 and 244 are different from the channel properties observed by antenna ports groups 241 and 242.
For a UE with the type 1 antenna arrangement (e.g., UE 220 in Figure 2A) , uplink performance for the uplink transmissions from different antenna port groups with the same antenna combining factor is substantially the same. In this document, the term “substantially” indicates differences too small to affect the sought after feature. For example, the difference between uplink performances for the uplink transmissions from different antenna port groups is too small to consider using different precoders. Note also that “similar” and “substantially the same” are interchangeable.
Thus, for a UE with the type 1 antenna arrangement (e.g., UE 220 illustrated in Figure 2A) , the uplink performance is likely similar for the precoders andbecause the antenna ports {0, 4} are in the antenna port group 221 and the antenna ports {1, 5} are in the antenna port group 222. Therefore, the number of candidate precoders can be reduced for type 1 antenna arrangement, and, thereby, the overhead for the TPMI and TRI indication can be reduced.
Similarly, for a UE with a type 3 antenna arrangement (e.g., UE 240 illustrated in Figure 2C) , no significant uplink performance difference is likely for the uplink transmission from different antenna port groups with the same channel properties, such as 241 and 242, or 243 and 244.
However, for a UE with the type 3 antenna arrangement (e.g., UE 230 illustrated in Figure 2C) , significant uplink performance difference is likely for the uplink transmissions from different antenna port groups (e.g., 241 and 244, or 242 and 243) because the different antenna port groups likely observe significantly different the channel properties. Therefore, each antenna port group has to have indicated distinct candidate precoders.
In order to reduce overhead for uplink precoder indication, the NE has to have information on the number of antenna port groups that observe similar channel properties (e.g., whether the UE has a type 1, type 2, or type 3 antenna arrangement) . Taking advantage of the observed channel similarities, the network can indicate a precoder (TRI/TPMI) based on less than all the candidate precoders thereby reducing the overhead for uplink precoder indication. Moreover, when an antenna’s operability changes (e.g., in case of an antenna port group being blocked) , the observed channel property for at least one antenna port groups changes. Having such a change signaled and addressed (the network indicating use of other antenna group or precoder) improves the overall communication performance.
In order to achieve overhead reduction for uplink precoder indication, aspects of the embodiments described hereinafter include UE reporting on whether antenna port groups share the same channel property and control signaling exchanged between UE and NE for enabling or disabling precoder selection for plural antenna port group sharing channel property. Reducing the overhead for uplink precoder indication, which can apply to UE with any number of antenna port groups, improves the downlink performance.
Figure 3 is a signal diagram 300 for implementing overhead reduction for uplink precoder indication according to an embodiment. In this diagram 300, time flows from top to bottom (i.e., communications represented lower in this figure occur later than ones in above them) and the dash lines indicate optional messages which are present in some embodiments but are not mandatory. UE 120 provides 302 UE capability related to overhead reduction for uplink precoder indication, to NE 110. The UE capability indicates the number of UE antenna port groups and information on UE antenna port groups that have substantially the same channel property. In some other embodiments, the NE receives the UE capability from a core network or from another NE such as a base station, gNB or eNB.
NE 110 transmits 304 a first control message to UE 120. The first control message may be a Radio Resource Control (RRC) message, such as a RRCReconfiguration or a system information block (SIB) . Such an SIB can be an existing SIB (e.g., SIB1) or a new SIB (e.g., SIB J, where J is an integer above 21) .
The first control message configures at least one SRS resource for codebook and may indicate that the uplink transmission scheme is codebook-based transmission. The NE may also enable via the first message the antenna port group selection based precoders (e.g., non-coherent or partial-coherent precoders) indicating uplink transmission from a set of antenna port group (s) . Thus, the NE may configure candidate antenna port group (s) usable to generate the codebook-based transmission (also called “codebook-based PUSCH” ) .
Further, UE 120 may transmit 306, to NE 110, a report indicating the at least two UE antenna port groups that have the same channel property. NE 110 may then transmit 308, to UE 120, an overhead-reduction control message (e.g., a medium access control, MAC, control element, MAC CE or a downlink control information, DCI, message) enabling the at least two antenna groups to select a precoder based on a common precoder indication.
NE 110 transmits 310 a second control message (e.g., a DCI message) to UE 120. The second control message schedules (i.e., it is an uplink grant) the codebook-based PUSCH and includes a precoder indication identifying a precoder among the candidate precoders associated with the at least two of the UE antenna port groups sharing the channel property. The indicated candidate precoder may be selected based on UE’s report regarding status of the channel property for the antenna port groups. For example, antenna port groups 221, 222, 223, and 224 of UE 220 (in Figure 2A) may use the same precoder identified by a single precoder indication, the overhead (i.e., amount of precoder information included in 310) being reduced to 25%relative to the conventional submission of separate precoder indications. In another example, antenna port groups 241, 242, 243, and 244 of UE 240 (in Figure 2C) , the overhead may be reduced to 50%if one precoder indication is for the antenna port groups that observe the same channel quality (e.g., 241 and 242, and/or 243 and 244) .
UE 120 then transmits 312 the codebook-based PUSCH as scheduled via the second control message and generated for at least one of the UE antenna port groups using the precoder.
When a change in operability of an antenna port group occurs, the UE may report an update of the channel property observed by the UE antenna port groups. For example, a change in operability occurs when an antenna port group of a cell phone becomes inactive because of an obstacle (e.g., the user covers it with his hand) , or, vice-versa, the antenna port group becomes active once the obstacle (such as the user’s hand) is removed. The UE may report whether some of UE antenna port groups still observe substantially the same channel property. The UE may report the updated status via an RRC message (e.g., UE assistance information) thereof, a MAC CE, or an uplink control information (UCI) message via a physical uplink control channel, PUCCH, or PUSCH. The NE may further enable or disable the precoder selection of antenna port groups with overhead reduction by indicating an uplink transmission from a set of antenna port group (s) via a MAC CE or DCI.
Figure 4 is a flowchart of a wireless communication method 400 performed by a UE according to an embodiment, and Figure 5 is a flowchart of a wireless communication method 500 performed by an NE according to an embodiment.
Method 400 includes steps 404, 410, and 412. The UE receives 404 a first control message configuring SRS and enabling one or more precoder groups usable by UE antenna port groups to generate a codebook-based uplink transmission. In an embodiment, the first control message is an RRC message configuring SRS for determining a codebook-based PUSCH, and, optionally, enabling one or more precoder groups usable by the UE antenna port groups to generate the codebook-based PUSCH (i.e., signal 304 in Figure 3) .
The UE also receives 410 a second control message including a precoder indication identifying a precoder associated with at least two of the UE antenna port groups. In one embodiment, the second control message is a DCI message scheduling the codebook-based PUSCH as signal 310 in Figure 3.
The UE transmits 412 the codebook-based transmission generated by the at least one of the UE antenna port groups using the precoder identified via the precoder indication. For example, the codebook-based transmission is a codebook-based PUSCH (as signal 312 in Figure 3) .
Optionally (as suggested by the dashed-line boxes in Figure 4) , method 400 may include one or more of steps 402, 406, and 408. The UE may transmit 402, UE capability information including the number of UE antenna port groups and information on at least two among the UE antenna port groups having a substantially same channel property. The UE may transmit 406 a report to indicate at least two UE antenna port groups. The at least two UE antenna port groups may have substantially the same channel property (as in 306 in Figure 3) . The UE may receive 408 an overhead-reduction control message enabling the at least two UE antenna port groups to use the precoder indication to identify the precoder. The overhead-reduction control message may be a MAC CE or DCI message (as signal 308 in Figure 3) .
Method 500 includes steps 504, 510, and 512. The NE transmits 504 a first control message configuring SRS and enabling one or more precoder groups usable by UE antenna port groups to generate a codebook-based uplink transmission. In an embodiment, the first control message is an RRC message configuring SRN for determining a codebook-based PUSCH, and, optionally, enabling one or more precoder groups usable by the UE antenna port groups to generate the codebook-based PUSCH (i.e., signal 304 in Figure 3) .
The NE also transmits 510 a second control message including a precoder indication identifying a precoder associated with at least two of the UE antenna port groups. In one embodiment, the second control signal is a DCI message scheduling a codebook-based PUSCH as signal 310 in Figure 3.
The NE then receives 512 the codebook-based transmission generated by the at least one of the UE antenna port groups using the precoder identified via the precoder indication. In one embodiment, the codebook-based transmission is a codebook-based PUSCH as 312 in Figure 3.
Optionally (as suggested by the dashed-line boxes in Figure 5) , method 500 may include one or more of steps 502, 506, and 508. The NE may receive 502, UE capability information including the number of UE antenna port groups and information on at least two among the UE antenna port groups having a substantially same channel property. The NE may also receive 506 a report to indicate at least two UE antenna port groups. The at least two UE antenna port groups may have substantially the same channel property (as in 306 in Figure 3) . The NE may transmit 508 an overhead-reduction control message enabling the at least two UE antenna port groups to use the precoder indication to identify the precoder. The overhead-reduction control message may be a MAC CE or DCI message (as signal 308 in Figure 3) .
Focusing now on the content of the UE report exchanged via signal 306 (transmitted by the UE at 406 and received by the NE at 506) , the report may provide an antenna port group status in an explicit or implicit manner according to various embodiments described hereinafter. In an embodiment, the UE may report information indicating whether a subset of or all the antenna port groups share substantially the same channel property. In another embodiment, the UE may report the type of antenna port group arrangement (e.g., type 1, type 2, or type 3 in Figures 2A, 2B, or 2C, respectively) . In yet another embodiment, the UE report may indicate the channel property shared by some of the antenna port groups such as the same quasi-co-location properties including at least one of delay spread, average delay, Doppler spread, Doppler shift, spatial transmission filter and average gain. For example, a type 1 UE may report that all its antenna port groups share the same channel property, and a type 3 UE may report that at least two of its antenna port groups share the same property.
In some other embodiments, the UE report information indicating one or more than one set of antenna port group (index) that share the same channel property. For example, Figures 6A, 6B, and 6C illustrate different type UEs having eight antenna ports in four antenna port groups. Type 1 UE 650 (e.g., type 1 antenna arrangement) in Figure 6A may report that all its antenna port groups (i.e., 651, 652, 653, 654) share substantially the same channel property. Antenna port groups 661, 662, 663, 664 of type 2 UE 660 (e.g., type 2 antenna arrangement) all perceive different channel properties. Type 3 UE 670 (e.g., type 3 antenna arrangement) may report two sets of antenna port group indexes (one index corresponding to antenna port groups 671, 672 and the other to antenna port groups 673, 674) for the couples of antenna port groups sharing substantially the same channel property.
In some other embodiments, the UE may report information indicating the supported the number of antenna ports groups M and information on the number of antenna port group cluster/set, which share the same or similar channel property. In such implementations, the UE may also report the number of antenna port group in each cluster/set. For reporting the number of antenna port groups in each cluster/set, in one embodiment, the antenna port groups are nearly equally distributed in each cluster/set. For example, if the number of antenna groups per cluster/set is j=floor (M/N) for the first N-1 antenna clusters/sets, then the last (N^th) antenna port group cluster/set will include M- (N-1) *j antenna port groups. In another example, if the number of antenna port groups in the first antenna port group cluster/set is j then for the remaining N-1 antenna port group clusters/sets have (M-j) / (N-1) antenna port groups.
Turning now to describing an implicit manner of providing an antenna port group status, the UE may report information indicating whether it supports or recommends precoder selection based on the antenna port groups having same channel property. In some embodiments, the UE may report whether it supports or recommends the antenna port group permutation for precoders indicating uplink transmission from a subset of antenna port group (s) .
For example, Figures 7A, 7B, 7C, and 7D illustrate precoders associated with one of antenna port groups of UE 770, respectively. Precoders supported or recommended are specified relative to antenna port group 781 in Figure 7A, relative to antenna port group 782 in Figure 7B, relative to antenna port group 783 in Figure 7C, and relative to antenna port group 784 in Figure 7D. If UE 780 is a type 1 UE (e.g., type 1 antenna arrangement) , it may report that it supports or recommends precoders without going through each antenna port group permutation, thus, the candidate precoders obtained via a permutation from the ones specified for one of the antenna port groups (as in any of Figures 7A-D) . If UE 780 is a type 2 UE (e.g., type 2 antenna arrangement) , it reports precoders that it supports or recommends for each of the antenna port groups (no permutation) . If UE 780 is a type 3 UE (e.g., type 3 antenna arrangement) , it may report that it supports or recommends precoders with partial antenna port group permutation, e.g., the candidate precoders associated with antenna port groups 781 and 783.
In other embodiments, the precoders may be divided into several groups based on the non-zero-power antenna port index. The precoders with non-zero-power antenna ports in the same antenna port group pertain to the same group. The UE may report the supported or recommended precoder groups.
In yet another embodiment, the UE may report the measured layer 1 reference signal received power (L1-RSRP) difference for each UE antenna port group or antenna port. In some implementations, the UE may report separately L1-RSRP difference for each reported channel measurement resource (CMR) . Table 1 illustrates one example for the report content of CMR-specific L1-RSRP difference across UE antenna port group report or antenna port. The differential L1-RSRP for a CMR other than CMR x1 is calculated as the L1-RSRP measured from the CMR minus the L1-RSRP measured from the CMR x1. For example, the differential L1-RSRP for CMR x2 is calculated as the L1-RSRP for CMR x2 minus the L1-RSRP for CMR x1. In some embodiments, the indicator of L1-RSRP difference across UE antenna ports or antenna port groups may indicate the value of the offset between the highest measured L1-RSRP and lowest measured L1-RSRP from each of the UE antenna ports or antenna port groups. In some other implementations, the indicator of L1-RSRP difference across UE antenna ports or antenna port groups may indicate whether the offset between the highest measured L1-RSRP and lowest measured L1-RSRP from each of the UE antenna ports or antenna port groups is above a threshold, where the threshold may be predefined or configured by the NE via RRC message or MAC CE.
Table 1
In some other embodiments, the UE may report a common L1-RSRP difference for a subset of or all the reported CMRs. Table 2 illustrates one example for such a report including common L1-RSRP difference across UE antenna port groups or antenna ports.
Table 2
In some other embodiments, the UE reports the measured L1-RSRP offset for each UE antenna port or antenna port group. In yet other embodiments, the UE reports the measured L1-RSRP offset for a set of UE antenna port groups, where the set of UE antenna port groups may be configured by the NE or reported by the UE, (e.g., the UE antenna port groups reported in the UE capability) , the UE antenna port groups likely sharing the same channel property. In some other embodiments, the UE reports whether the measured L1-RSRP offset between the antenna port or the antenna port group exceeds a threshold, which the threshold may be predefined (e.g., 6dB) or configured by the NE.
In some embodiments, UE’s report is configured by the network. For example, the UE may receive a report configuration from the NE. The report configuration may also specify the time and frequency resource for an uplink channel, (e.g., PUCCH or PUSCH) and a time-domain behavior (e.g., aperiodic, semi-persistent, or periodic) for the UE to generate and transmit the antenna port group status report. The NE may transmit the configuration and/or trigger the UE report via an RRC message, a MAC CE, or a DCI message.
In one embodiment, for the UE to transmit a periodic report, the NE may configure time/frequency domain of the uplink resource for the uplink channel, periodicity, and slot offset via an RRC message. In another embodiment, for the UE to transmit a semi-persistent report, the NE may configure the time/frequency domain of uplink resource for the uplink channel, periodicity, and slot offset via an RRC message, and trigger the report by transmitting a MAC CE. In another embodiment, for the UE to transmit an aperiodic report, the NE may configure the time/frequency domain of uplink resource for the uplink channel, periodicity, and slot offset by RRC message, and trigger the report via a DCI message.
In some embodiments, the UE may report the antenna port group status with the UE capability. In some other embodiments, the UE may report the antenna port group status via an RRC message (e.g., as UE assistance information included in the RRC message) . In some other embodiments, the UE may report the antenna port group status using a MAC CE. In yet other embodiments, the UE may report the antenna port group status as an uplink control information (UCI) transmitted via PUCCH or PUSCH.
In other embodiments, the UE may trigger the antenna port group status report if one or more than one of the following events occurs. A first event is the measured downlink L1-RSRP offset or pathloss offset for a downlink reference signal (e.g., a synchronization signal block, SSB, or a channel state information-reference signal, CSI-RS) between a first antenna port group and a second antenna port group in the same set of antenna port groups is above a threshold. The threshold may be predefined or configured by the NE. The first and second antenna port group may be the antenna port groups corresponding to the set of antenna port groups sharing the same channel property, which was reported in the UE capability.
A second event is a timer for the antenna port group status report expires, where the timer measures a duration configured by the. The UE resets the timer upon reporting the antenna port group status. A third event is activation or de-activation of a secondary cell or second cell group. A fourth event is addition or removal of a primary secondary cell. This list of events is not intended to be limiting or exclusive.
In some embodiments, the NE may configure a scheduling request (SR) for the UE to request uplink resources for transmitting the antenna port group status report. The SR may be different from other SR requesting uplink resources.
The UE may report the antenna port group status via an RRC message (e.g., as UE assistance information) . The UE may alternatively report the antenna port group status using a MAC CE or as UCI transmitted via PUCCH or PUSCH.
Other aspects discussed below relate to control signaling for precoder group subset configuration. In some embodiments, selecting precoder for the antenna port groups may be segmented for subsets precoder groups, each precoder group including the precoders from the same antenna port group.
The precoder group may be defined separately for each number of layers (each rank) . In one example, four rank 1 precoder groups may be defined for an 8-port UE (four antenna port groups) , that is, one precoder group for each of the antenna port groups. For the same 8-port UE, ten rank 2 precoder groups may be defined (taking into consideration all the antenna combinations) .
In some embodiments, the network entity may configure whether each of predefined precoder groups is enabled or disabled. In some other embodiments, the NE may configure whether the antenna port group permutation is enabled or not. If the antenna port group permutation is enabled, all the precoder groups of a certain rank are enabled. Otherwise, only the precoders from a certain precoder group (s) is/are enabled (e.g., the first precoder group) . If antenna port group permutation is disabled for the ten rank 2 precoder groups, only the precoder group from some antenna port groups are enabled the others being disabled. All the antenna port groups may be enabled.
According to a first approach, an RRC message may be used to configure a precoder group subset. The NE transmits an RRC message (e.g., an RRCReconfiguration message) for configuring the precoder group subset for uplink precoder selection. In some embodiments, the precoder group subset configuration may be configured for PUSCH transmissions associated with each SRS resource set. In some other embodiments, the precoder group subset is configured per uplink bandwidth part. In some other embodiments, the precoder group subset configuration is configured per serving cell or serving cell group.
According to a second approach, the NE transmits a MAC CE configuring or indicating the precoder group subset for uplink precoder selection. The MAC CE may include one or more of: (i) a serving cell or serving cell list index, which indicates the target serving cell (s) for the configured precoder group subset; (ii) an uplink bandwidth part index, which indicates the target uplink bandwidth part for the configured precoder group subset; (iii) an SRS resource set index (es) , which indicates the target SRS resource set index (es) for the configured precoder group subset when the SRS resource set is associated with a PUSCH; (iv) an indicator of precoder group (s) subset, which indicates the enabled and/or disabled precoder group (s) (e.g., a bitmap with each bit indicating the enabling/disabling status for each precoder group (s) ) and (v) an action delay, which indicates the action delay for the MAC CE.
The UE may apply the indicated precoder group subset after X slots/milliseconds delay from the UE transmitting the last symbol of the PUCCH or PUSCH with the acknowledgement (ACK) for the PDSCH with the MAC CE. The value of X may be predefined (e.g., X=3) or configured by NE via the RRC message or MAC CE.
According to a third approach, the NE transmits a DCI configuring the precoder group subset for uplink precoder selection. In some embodiments, the PDCCH for the DCI may be associated with or scrambled by cell-radio network temporary identifier (C-RNTI) . In some other embodiments, the PDCCH for the DCI may be associated with or scrambled by a RNTI configured by the NE via the RRC message or the MAC CE. The content for the DCI could be the same as in the second approach.
In some embodiments, the DCI message may further indicate the PUCCH resource for the ACK/negative acknowledgement (NACK) feedback. The UE may apply the indicated precoder group subset after Y symbols/slots/milliseconds delay from the UE transmitting the last symbol of the PUCCH or PUSCH with the ACK for the PDSCH with the DCI. The value of Y may be predefined (e.g., Y=28) or configured by NE via RRC message, the MAC CE or the DCI message.
The embodiment descriptions in this section refer to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The detailed descriptions do preclude other embodiments within the scope of the appended claims. The embodiments are not limited to the described configurations but may be extended to other arrangements.
Reference throughout this section to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
Numerical adjectives “first” , “second” , and “third” do not imply any order (are not ordinals) but are markers to distinguish separate instances of similar elements. References to the singular (e.g., “a” or “an” , “the” ) should include the plural unless clearly indicated otherwise.
Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. The methods or flowcharts may be implemented in a computer program, software or firmware tangibly embodied in a computer-readable storage medium for execution by a specifically programmed computer or processor.

Claims

A wireless communication method (400) performed by a UE (120) , the method comprising:

receiving (304, 404) a first control message configuring sounding reference signals and enabling one or more precoder groups usable by UE antenna port groups to generate a codebook-based uplink transmission;

receiving (310, 410) a second control message including a precoder indication identifying a precoder among the one or more precoder groups, the precoder being associated with at least two of the UE antenna port groups; and

transmitting (312, 412) the codebook-based uplink transmission generated by at least one of the UE antenna port groups using the precoder identified via the precoder indication.
The wireless communication method of claim 1, wherein the at least two of the UE antenna port groups have a substantially same channel property if an antenna-arrangement criterion is met.
The wireless communication method of claim 2, wherein the antenna-arrangement criterion includes:

UE antennas pertaining to the at least two among the UE antenna port groups have substantially same orientation; and/or

the UE antennas pertaining to the at least two among the UE antenna port groups are positioned so that a distance between adjacent UE antennas is less than a predetermined distance.
The wireless communication method of any of claims 1 to 3, wherein the at least two of the UE antenna port groups have a substantially same quasi-co-location property including a Doppler shift, a Doppler spread, an average delay, a delay spread, average gain, or spatial transmission parameters.
The wireless communication method of any of claims 1 to 4, further comprising:

transmitting (302, 402) UE capability information including a number of the UE antenna port groups and information on the at least two of the UE antenna port groups having a substantially same channel property.
The wireless communication method of any of claims 1 to 5, further comprising:

transmitting (306, 406) an antenna port group status report indicating the at least two of the UE antenna port groups.
The wireless communication method of claim 6, wherein the report comprises at least one of:

a type of UE antenna arrangement;

a substantially same channel property;

a number of clusters made of the at least two among the UE antenna port groups;

a rule indication identifying a predetermined rule for selecting precoders for the UE antenna port groups; or

a summary of reference signal measurements including differences across the UE antenna port groups.
The wireless communication method of any of claims 6 or 7, further comprising:

receiving a configuration for generating the antenna port group status report, the report configuration specifying a content and a time domain manner for the transmitting the antenna port group status report.
The wireless communication method of any of claims 6 to 8, further comprising:

initiating the transmitting of the antenna port group status report upon detecting an event impacting the at least two of the UE antenna port groups.
The wireless communication method of any of claims 1 to 9, further comprising:

transmitting a message indicating a change in operability of at least one UE antenna port group;

receiving a third control message including an updated precoder indication; and

transmitting the codebook-based uplink transmission generated using one of the one or more precoder groups identified via the updated precoder indication.
The wireless communication method of any of claims 1 to 10, further comprising:

receiving an overhead-reduction control message (308, 408) enabling the at least two of the UE antenna port groups to use the precoder indication to identify the precoder.
A wireless communication method (500) performed by a network entity (110) , the method comprising:

transmitting (304, 504) a first control message configuring sounding reference signals and enabling one or more precoder groups usable by UE antenna port groups to generate a codebook-based uplink transmission;

transmitting (310, 510) a second control message including a common precoder indication identifying a precoder among the one or more precoder groups, the precoder being associated with at least two of the UE antenna port groups; and

receiving (312, 512) the codebook-based uplink transmission generated by the at least one of the UE antenna port groups using the precoder identified via the common precoder indication.
The wireless communication method of claim 12, wherein the at least two of the UE antenna port groups have a substantially same channel property.
The wireless communication method of any of claims 12 or 13, further comprising:

receiving (302, 502) UE capability information including a number of the UE antenna port groups and information on the at least two among the UE antenna port groups having a substantially same channel property.
The wireless communication method of any of claims 12 to 14, further comprising:

receiving (306, 506) an antenna port group status report that includes at least one of:

a type of UE antenna arrangement,

a substantially same channel property of the at least two of the UE antenna port groups,

a number of clusters made of the at least two among the UE antenna port groups,

a rule indication identifying a predetermined rule for selecting precoders for the UE antenna port groups, or

a summary of reference signal measurements including differences across the UE antenna port groups.
The wireless communication method of any of claims 12 to 15, further comprising:

transmitting a configuration for generating the antenna port group status report, the report configuration specifying a content and a time domain manner of transmitting the antenna port group status report.
The wireless communication method of any of claims 12 to 16, further comprising:

receiving a message indicating a change in operability of at least one UE antenna port groups;

transmitting a third control message including an updated precoder indication; and

receiving the codebook-based uplink transmission generated using the one of

candidate precoders identified via the updated precoder indication.
A wireless communication device (110, 120) comprising a transceiver (112, 122) , a processor (113, 124) and computer-readable storage media (114, 125) storing executable instructions (117, 127, 128) for the processor to perform any of the methods recited in claims 1-17, using the wireless transceiver.