Partial-bandwidth feedback for beam combination codebook

Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may perform channel state information (CSI) measurements on one or more reference signal transmissions received from a base station. Based on the CSI measurements, the UE may generate a CSI report, and the UE may transmit the CSI report to the base station. In some cases, the generated CSI report may include a first portion and a second portion. The first portion may indicate whether the second portion of the CSI report includes full-band CSI feedback or partial-band CSI feedback. The second portion may provide the CSI feedback for one or more identified sub-bands. In some cases, the second portion may include a sub-band index indicating the identified sub-bands. Additionally or alternatively, the second portion may include a bitmap indicating a correspondence between multiple CSI feedback values and multiple corresponding sub-band indexes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a 371 national phase filing of International Patent Application No. PCT/CN2020/075444 by Chen et al., “PARTIAL-BANDWIDTH FEEDBACK FOR BEAM COMBINATION CODEBOOK,” filed Feb. 15, 2020; and to International Patent Application No. PCT/CN2019/075247 by Chen et al., entitled “PARTIAL-BANDWIDTH FEEDBACK FOR BEAM COMBINATION CODEBOOK,” filed Feb. 15, 2019, each of which is assigned to the assignee hereof, and each of which is expressly incorporated by reference in its entirety herein.

BACKGROUND

The following relates generally to wireless communications, and more specifically to partial-bandwidth feedback for beam combination codebooks.

In some wireless communications systems, wireless devices may perform beamforming to shape or steer an antenna beam along a spatial path from a transmitting wireless device to a receiving wireless device. In some cases, performing beamforming may involve the transmitting wireless device constructing a precoding matrix based on feedback received from the receiving wireless device and precoding transmissions based on the precoding matrix. This precoding procedure may define how the beams are constructed using the different antenna elements of an antenna array at the transmitting wireless device. The amount of feedback generated by and received from the receiving wireless device may increase with the number of beams, layers, and sub-bands over which a beamformed transmission is transmitted. As the amount of feedback increases, the overhead of providing the feedback may result in reduced efficiency or excess latency in the communications for the wireless device.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support partial-bandwidth feedback for beam combination codebooks. Generally, the described techniques provide for reducing feedback overhead of channel state information (CSI) reporting. For example, a user equipment (UE) may implement partial-band CSI reporting to reduce an amount of overhead for reporting CSI feedback while maintaining a relatively high level of performance.

To support partial-band CSI reporting, the UE may perform CSI measurements on one or more reference signal transmissions received from a base station via one or more beams. Based on the CSI measurements, the UE may generate a CSI report for a beam combination codebook for the one or more beams, and the UE may transmit the CSI report to the base station. In some cases, the generated CSI report may include a first portion and a second portion. The first portion of the CSI report may indicate whether partial-band feedback is enabled for the second portion of the CSI report—that is, indicating whether the second portion of the CSI report includes full-band CSI feedback or partial-band CSI feedback. The second portion of the CSI report may provide CSI feedback for one or more identified sub-bands or for a wideband. In some cases, the second portion of the CSI report may include a sub-band index indicating the identified sub-band, or the wideband, for which the UE is to provide CSI feedback. Additionally or alternatively, the second portion of the CSI report may include a bitmap indicating a correspondence between multiple CSI feedback values and multiple corresponding wideband and/or sub-band indexes.

A method of wireless communication at a UE is described. The method may include performing CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generating a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmitting the CSI report to the base station.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generate a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmit the CSI report to the base station.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for performing CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generating a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmitting the CSI report to the base station.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generate a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmit the CSI report to the base station.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE may be to report the partial CSI feedback, where the second portion includes an indicator that a value of a parameter in the partial CSI feedback may be a wideband value for the active bandwidth. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the parameter includes an amplitude indicator, a phase indicator, a co-phase indicator, or a combination thereof.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE may be to report the partial CSI feedback, where the second portion includes a sub-band index indicating that a value of a parameter in the partial CSI feedback may be for a sub-band corresponding to the sub-band index. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the parameter includes an amplitude indicator, a phase indicator, a co-phase indicator, or a combination thereof.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE may be to report the partial CSI feedback, where the second portion includes a bitmap indicating one or more sub-bands associated with corresponding values of one or more parameters of the partial CSI feedback.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing CSI measurements on the one or more reference signal transmissions includes determining information indicating a RI, a channel quality indicator (CQI), a number of non-zero wideband amplitude coefficients per layer, or a combination thereof, and the first portion of the CSI report indicates the RI, CQI, and the number of non-zero wideband amplitude coefficients per layer, or the combination thereof.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing CSI measurements on the one or more reference signal transmissions includes determining information indicating a precoding matrix indicator (PMI) for each of the number of non-zero wideband amplitude coefficients per layer, where the second portion of the CSI report includes the information indicating the PMI.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a trigger for transmitting the CSI report to the base station, and determining whether to generate the CSI report including the full CSI feedback or the partial CSI feedback based on a type of the trigger for transmitting the CSI report to the base station.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a CSI feedback configuration from the base station indicating whether the partial CSI feedback may be enabled for the beam combination codebook, where the generating may be based on the CSI feedback configuration. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the CSI feedback configuration further indicates a maximum number of sub-bands for the partial CSI feedback in the CSI report.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether the UE may be to report the full CSI feedback or the partial CSI feedback based on a variation between a wideband CQI measurement and one or more sub-band CQI measurements.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether the UE may be to report the full CSI feedback or the partial CSI feedback based on a variation between a wideband value for the beam combination codebook and one or more sub-band values for the beam combination codebook.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether the UE is to report the full CSI feedback or the partial CSI feedback based on a code rate for the second portion of the CSI report for the full CSI feedback. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE is to report the full CSI feedback based on the code rate not satisfying a threshold. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE is to report the partial CSI feedback based on the code rate satisfying a threshold. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the threshold is based on a target code rate corresponding to a modulation and coding scheme, an offset value corresponding to the modulation and coding scheme, or a combination thereof.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first portion of the CSI report indicates a number of information bits present in the second portion of the CSI report.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for encoding the first portion using a first encoding process to obtain a first codeword, encoding the second portion using a second encoding process to obtain a second codeword, and transmitting the CSI report includes transmitting the first and second codewords.

DETAILED DESCRIPTION

In some wireless communications systems, a user equipment (UE) may report channel state information (CSI) feedback to a base station for multiple discrete Fourier transform (DFT) beams. The frequency domain of the DFT beams may span a bandwidth part (BWP), which may include one or more sub-bands according to a granularity configured at the UE or the base station. Based on the CSI feedback, the base station may construct a precoding matrix and may precode transmissions over the multiple DFT beams. In some cases, the CSI feedback may include bit representations for a number of precoding coefficients (e.g., a wide-band amplitude scaling factor, a sub-band amplitude scaling factor, a beam combination coefficient corresponding to a phase value, etc.) with respect to a particular beam, polarity, and layer number. Additionally, for a subset of the precoding coefficients (e.g., sub-band amplitude scaling factor and beam combination coefficient), the CSI feedback may include a bit representation for each reporting sub-band of the BWP.

A UE may choose a set of beams for which the UE is to generate beam parameters, and the UE may provide feedback based on a beam combination codebook. Some beam combination codebooks (including, e.g., a New Radio (NR) Type II codebook), may be designed to facilitate relatively high performance (e.g., high throughput) for use with some communications systems. To implement the codebook design, however, a UE may report a relatively large amount of CSI feedback, thus resulting in a relatively large payload size used to transmit the CSI feedback.

Some types of UEs (e.g., low-tier UEs), however, may have a limited amount of available resources for communications (e.g., for CSI reporting). As such, low-tier UEs may have a restricted amount of overhead available to report CSI feedback. In some cases, low-tier UEs may be designed for low mobility and/or for low bandwidth communications. As such, a large payload of CSI feedback may include information that may be implicitly known or that may change relatively infrequently and thus may be reported less frequently as compared to other UEs. Accordingly, techniques are provided herein to enable a UE to reduce an amount of overhead for CSI reporting while maintaining a relatively high level of performance. For example, the UE may provide to the base station CSI feedback for a partial bandwidth including beam parameters for one or more sub-bands in a corresponding CSI report, where the CSI feedback may include full-band CSI feedback or partial-band CSI feedback.

In some cases, a CSI report may include a first portion and a second portion, where the first portion of the CSI report may indicate whether partial-band feedback is enabled for the second portion of the CSI report—that is, indicating whether the second portion of the CSI report includes full-band CSI feedback or partial-band CSI feedback. The second portion of the CSI report may provide CSI feedback for one or more identified sub-bands or for the wideband. In cases in which the CSI feedback includes partial-bandwidth CSI feedback, the UE may indicate CSI feedback for one or more particular sub-bands (e.g., sub-bands that the UE and/or the base station may have identified as more relevant and/or that may more rapidly vary) and not indicate CSI feedback for one or more other sub-bands. In this way, the UE may provide the base station relatively more important CSI feedback information while conserving an amount of signaling overhead by signaling fewer bits as compared to signaling CSI feedback for each sub-band of the full radio frequency bandwidth.

Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are additionally described in the context of an additional wireless communications system, communications schemes, a payload size table, and a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to partial-bandwidth feedback for beam combination codebooks.

FIG.1illustrates an example of a wireless communications system100that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. The wireless communications system100includes base stations105, UEs115, and a core network130. In some examples, the wireless communications system100may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a NR network. In some cases, wireless communications system100may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

In some wireless communications systems100, a base station105may precode one or more transmissions to a UE115according to a precoding matrix indicator (PMI) codebook used for spatial channel information feedback. The base station105may use a specific PMI codebook format based on the rank of the one or more transmissions. For example, if the transmissions have a rank of 1, the precoding matrix W may be a 2×1 matrix equal to a spatial domain compression matrix W1multiplied by a coefficient matrix W2, where W may be normalized to 1. If the transmissions have a rank of 2, the precoding matrix may be a 2×2 matrix equal to a spatial domain compression matrix W1multiplied by a coefficient matrix W2, where columns of W may be normalized to 1/√{square root over (2)}.

In general, the precoding matrix W may be a l×r matrix, where l corresponds to a number of layers and r corresponds to rank, that has entries {tilde over (w)}r,l. The base station105may determine the precoding matrix (i.e., the precoder) according to

w~r,l=∑i=0L-1⁢bk1(i)⁢k2(i)·pr,l,i(WB)·pr,l,i(SB)·cr,l,i,
where L may correspond to a total number of transmission beams, bk1,k2may correspond to an oversampled two-dimensional (2D) DFT beam, pr,l,i(WB)may correspond to a wideband amplitude scaling factor, pr,l,i(SB)may correspond to a sub-band amplitude scaling factor, and cr,l,imay correspond to a beam combining coefficient. In some cases, L may be configurable (e.g., L∈{2,3,4}). Additionally or alternatively, an amplitude scaling mode may be configured (e.g., by the base station105) as either a wideband and sub-band mode (e.g., with unequal bit allocation) or a wideband-only mode.

The methods disclosed herein may enable a UE115and a base station105to reduce an amount of overhead for CSI reporting while maintaining a relatively high level of performance. For example, the UE115may provide to the base station105CSI feedback for a partial bandwidth including beam parameters for one or more sub-bands in a corresponding CSI report, where the CSI feedback may include full-band CSI feedback or partial-band CSI feedback. The CSI report may include a first portion and a second portion, where the first portion of the CSI report may indicate whether partial-band feedback is enabled for the second portion of the CSI report—that is, indicating whether the second portion of the CSI report includes full-band CSI feedback or partial-band CSI feedback. The second portion of the CSI report may provide CSI feedback for one or more identified sub-bands or for the wideband. In cases in which the CSI feedback includes partial-bandwidth CSI feedback, the UE115may indicate CSI feedback for one or more particular sub-bands (e.g., that the UE115and/or the base station may have identified as more relevant and/or that may more rapidly vary) and not indicate CSI feedback for one or more other sub-bands. In this way, the UE115may provide the base station105the relatively most pertinent CSI feedback information while conserving an amount of signaling overhead by signaling fewer bits than full-band CSI reporting.

FIG.2illustrates an example of a wireless communications system200that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. In the example ofFIG.2, wireless communications system200may include a base station105-aand a UE115-a, which may be examples of the corresponding devices as described with reference toFIG.1. The base station105-amay provide network coverage for a geographic coverage area110-a. To support communications between the base station105-aand the UE115-a, the UE115-amay transmit CSI feedback210to the base station105-aon an uplink channel205. For example, the UE115-amay transmit spatial channel information (e.g., a PMI) feedback in the CSI feedback210.

The UE115-amay measure one or more CSI reference signals from the base station105-aat one or more antenna ports. The CSI reference signals may be transmitted via one or more beams. The UE115-amay utilize CSI measurements from the one or more antenna ports to determine one or more coefficients (e.g., a wideband beam amplitude scaling factor, a sub-band beam amplitude scaling factor, a beam combining coefficient, etc.) corresponding to a precoding matrix W and to generate a bit representation of each coefficient. Each coefficient may be associated with a set of possible coefficient values for different beam, polarity, and layer combinations. In general, the UE115-amay choose the set of beams for which the UE115-agenerates the coefficients and provide feedback based on a beam combination codebook. Additionally, some of these coefficients (e.g., the sub-band beam amplitude scaling factor, the beam combining coefficient, etc.) and their corresponding bit representations may vary according to a number of reporting sub-bands within a BWP. As such, the set of possible values for the coefficients may further include coefficient values for each reporting sub-band. The UE115-amay include bit representations of these sets of coefficient values for each coefficient in the CSI feedback210transmitted to the base station105-a.

In one example, the UE115-amay determine a wideband amplitude scaling factor pr,l,i(WB)for each beam i, polarity r, and layer l. The wideband amplitude scaling factor pr,l,i(WB)may represent an average amplitude of a beam over all reporting sub-bands and may be represented in the CSI feedback210by three (3) bits (e.g., pr,l,i(WB)∈{1, √{square root over (0.5)}, √{square root over (0.25)}, √{square root over (0.125)}, √{square root over (0.0625)}, √{square root over (0.0313)}, √{square root over (0.0156)}, 0}). Additionally or alternatively, the UE115-amay determine, for each sub-band, a sub-band amplitude scaling factor pr,l,i(SB)for each beam i, polarity r, and layer l. A sub-band amplitude scaling factor (SB) may represent an amplitude of a beam over a particular reporting sub-band and may be represented in the CSI feedback210by one (1) bit (e.g., pr,l,i(SB)ε{1, √{square root over (0.5)}}). Additionally or alternatively, the UE115-amay determine, for each sub-band, a beam combining coefficient cr,l,ifor each beam i, polarity r, and layer l. A beam combining coefficient cr,l,imay represent a phase of a beam over a particular reporting sub-band and may be represented in the CSI feedback210by two (2) bits (e.g., to indicate 1 of four (4) phase values if using quadrature phase shift keying (QPSK)) or three (3) bits (e.g., to indicate one of eight (8) phase values if using eight phase shift keying (8PSK)). If represented by, for example, 2 bits, the beam combining coefficient cr,l,imay equal

The base station105-amay use the bit representation of the coefficients in conjunction with layer, polarity, and/or beam information (e.g., beam information as determined from a beam combination codebook) to calculate a precoding matrix W (e.g., as described with reference toFIG.1). In some cases, the base station105-amay determine to communicate with the UE115-aover L base station beams215(e.g., a base station beam215-band a base station beam215-d) and may forgo communicating with the UE115-aover other potential base station beams215(e.g., a base station beam215-aand a base station beam215-c). As such, the base station105-bmay identify coefficient values corresponding to the L beams from the CSI feedback210and may use those values when calculating the precoding matrix W. The base station105-amay select the L base station beams215from a set of oversampled DFT beams such that each of the L base station beams215are orthogonal to each other. In one example, the base station beam215-band the base station beam215-dmay be orthogonal to one another but may not be orthogonal to the base station beam215-aand/or the base station beam215-c. Upon calculating the precoding matrix W, the base station105-amay select a precoder from a codebook to use for precoding transmissions to the UE115-a, where the precoder is associated with the calculated precoding matrix. The base station105-amay accordingly communicate with the UE115-ausing the base station beam215-band the base station beam215-dand one or more UE beams220.

For a given bandwidth of an active BWP (e.g., the BWP over which the base station105-ais to communicate with the UE115-a), the UE115-amay be configured (e.g., by a base station105, such as the base station105-a) with a sub-band size via higher layer signaling (e.g., RRC or MAC signaling). Table 1 shows one example mapping of sub-band sizes, and a corresponding maximum number of reporting sub-bands, according to a number of physical resource blocks (PRBs), of the active carrier BWP:

TABLE 1Sub-Band Size and Maximum Number of ReportingSub-bands according to Carrier BWPCarrier BWPSub-band SizeMaximum Number of(PRBs)(PRBs)Reporting Sub-bands<24N/AN/A24-724, 86-1873-1448, 1610-18145-27516, 329-18
For example, according to Table 1, if the UE115-areceives transmissions from the base station105-aover a carrier BWP of thirty-two (32) PRBs, the UE115-amay be configured with a sub-band size within that BWP of either 4 PRBs or 8 PRBs. If the UE115-ais configured with the former sub-band size of 4 PRBs, the UE115-amay determine that the BWP contains 8 reporting sub-bands, and if the UE115-ais configured with the latter sub-band size of 8 PRBs, the UE115-amay determine that the BWP contains 4 reporting sub-bands. In general, the UE115-amay be configured such that the maximum number of reporting sub-bands is less than a threshold number (e.g., eighteen (18)) based on a maximum granularity (e.g., a minimum sub-band size or maximum number of reporting sub-bands) and a variance of the minimum sub-band size with BWP size. For example, according to Table 1, the maximum granularity (e.g., the minimum sub-band size) of a BWP from twenty-four (24) to seventy-two (72) PRBs may be 4 PRBs. As such, a BWP of 72 PRBs, where the UE115-ais configured with a sub-band size of 4 PRBs, may be associated with 18 reporting sub-bands

(e.g.,(7⁢24)=18).
If the BWP increases beyond 72, the maximum granularity may be reduced (e.g., to 8 PRBs) such that there are no more than 18 sub-bands in the BWP.

Some beam combination codebooks (including, e.g., an NR Type II codebook), may be designed to facilitate relatively high performance (e.g., high throughput) for use with some communications systems (e.g., in a communications system operating according to eMBB). To implement the codebook design, however, a UE115may report a relatively large amount of CSI feedback210, thus resulting in a relatively large payload size used to transmit the CSI feedback210. Table 2 shows an example payload size mapping according to a total number of transmission beams L:

TABLE 2CSI Feedback Payload SizeTotalL-beamStrongestWidebandWidebandSub-bandSub-bandTotalLRotationSelectionCoefficientAmplitudePayloadAmplitudePhasePayloadRank 1 Payload (Bits)247292239142341031532313192441132139519279Rank 2 Payload (Bits)247418336182733410630506263704411642631038543
Table 2 indicates calculated payload sizes, given the parameters: (N1, N2)=(4,4), Z=3 (8-PSK phase), and K Leading Coefficients. Table 2 includes columns including example values for a number of bits used to indicate: a total number of transmission beams L; a rotation, which may be given by ┌log2O1O2┐; a selection parameter of the beam L; a strongest coefficient (e.g., beam parameter) for 1 out of 2L beams given by ┌log22 L┐ bits per layer, a wideband amplitude given by 3×(2L−1) bits per layer, a total number of wideband payload bits; a sub-band amplitude (for each sub-band) given by 1×(K−1) bits per layer; a sub-band phase (for each sub-band) given by Z×(K−1)+2×(2L−K) bits per layer; and the resulting total number of bits in the payload based on an example of the number of wideband bits plus the number of bits for ten (10) sub-bands. For example, according to Table 2, for L=2 transmission beams and rank 1 transmissions, a total payload size for wideband and sub-band CSI feedback210may be 142 bits; for L=3 transmission beams and rank 1 transmissions, a total payload size for wideband and sub-band CSI feedback210may be 192 bits; and so on.

Some types of UEs115(e.g., low-tier UEs115, UEs operating according to NB-IoT, and/or low-tier UEs115at or near a cell edge) may have a limited amount of available resources for communications. As such, low-tier and/or cell-edge UEs115may not have a relatively large amount of overhead available to report a relatively large amount of CSI feedback210according to some codebook designs. In some cases, low-tier UEs115may be designed for low mobility (e.g., being fixed in one location) and/or for low bandwidth communications. As such, a large payload of CSI feedback210may include information that may be implicitly known or that may change relatively infrequently, and thus may be reported less frequently as compared to other UEs115. Accordingly, techniques are provided herein to reduce an amount of overhead for CSI reporting while maintaining a relatively high level of performance. For example, the UE115-amay provide to the base station105-aCSI feedback for a partial bandwidth including beam parameters for one or more sub-bands in a corresponding CSI report, where the CSI feedback for the partial bandwidth may use a reduced number of bits. For example, whereas full-band CSI feedback may include CSI feedback for a full radio-frequency spectrum bandwidth (or BWP), partial CSI feedback (e.g., CSI feedback for the partial bandwidth) may include CSI feedback for a subset of sub bands of the full radio-frequency spectrum bandwidth or BWP (e.g., CSI feedback particularly for one or more identified sub-bands).

FIG.3Aillustrates an example of a communications scheme300-athat supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. In some examples, the communications scheme300-amay implement aspects of the wireless communications system100and the wireless communications system200, as described with reference toFIGS.1and2, respectively. According to the communications scheme300-ashown inFIG.3A, a UE may provide to a base station CSI feedback for a partial bandwidth including beam parameters (e.g., amplitude, phase) for one sub-band per corresponding CSI report305(e.g., a CSI report305-a). In some examples, the phase may be given as a differential phase between polarizations or layers (e.g., co-phase).

As shown in the example communications scheme300-aofFIG.3A, the CSI report305-amay include a first portion310-aand a second portion315-b. The first portion310-aof the CSI report305-amay include a rank indicator (RI), a channel quality indicator (CQI), and an indication of a number of beams per layer having non-zero wideband amplitude coefficients. The second portion315-aof the CSI report305-amay include PMI value(s) corresponding to beams having a non-zero wideband amplitude coefficient, as indicated in the first portion310-aof the CSI report305-a.

As described herein, the UE may determine a wideband amplitude scaling factor representing an average amplitude of a beam over all reporting sub-bands. Similarly, the UE may determine, for each sub-band, a sub-band amplitude scaling factor representing an amplitude of a beam over a particular reporting sub-band. Further, the UE may determine, for each sub-band, a beam combining coefficient representing a phase or co-phase of a beam over a particular reporting sub-band.

In some cases, the first portion310-aof the CSI report305-amay further include an indication of whether partial-band feedback is enabled for the second portion315-aof the CSI report305-a—that is, whether the second portion315-aof the CSI report305-aincludes full-band CSI feedback of an active bandwidth (e.g., CSI feedback for the full radio-frequency spectrum bandwidth or BWP) or partial-band CSI feedback of the active bandwidth (e.g., CSI feedback for a subset of sub-bands of the full radio-frequency spectrum bandwidth or BWP). The active bandwidth may be a full bandwidth (e.g., a full bandwidth of a carrier configured for communication) or a BWP (e.g., a subset of the full carrier bandwidth) over which a UE is configured to communicate with a respective base station. For example, the UE may be configured to communication over a carrier including multiple BWPs, where a single BWP is active for the UE for the carrier at a given time. In some cases, the first portion310-aof the CSI report305-amay have a fixed payload size, where each field of the payload (e.g., fields for the RI, CQI, and each of the indications) may be encoded separately, for example, using independent codewords that may be decoded independently.

The indication of whether partial-band feedback is enabled for the second portion315-aof the CSI report305-amay be included in one or more fields of the first portion310-aof the CSI report305-a. For example, the first portion310-aof the CSI report305-amay include a field with a first bit value (e.g., a bit value of zero), indicating that the CSI feedback in the second portion315-aof the CSI report305-aincludes full-band feedback. The first portion310-aof the CSI report305-amay further indicate a number of bits (e.g., a payload size and/or a number of the non-zero wideband amplitude coefficients per layer) of the second portion315-bof the CSI report305-b. According to the first portion310-aof the CSI report305-aindicating full-band CSI feedback, the second portion315-aof the CSI report305-amay use the indicated number of bits to indicate the determined wideband amplitude scaling factor, sub-band amplitude scaling factor for each sub-band, and/or the beam combining coefficients for each sub-band (e.g., phase or co-phase feedback).

Alternatively, the indication field of first portion310-aof the CSI report305-amay be set to a second bit value (e.g., a bit value of one) indicating that the CSI feedback includes partial-band feedback. That is, the second portion315-aof the CSI report305-amay provide CSI feedback for one identified sub-band or for the wideband. In some cases, the second portion315-aof the CSI report305-amay include a sub-band index320, which may include a number of bits that indicate the identified sub-band, or the wideband, for which the UE is to provide CSI feedback. The number of bits may be given by ┌log2Nmax,sub┐, where Nmax,subis the maximum number of sub-bands for the system bandwidth or BWP. In one example, Nmax,submay be 18, and thus the number of bits may be five (5). The number of bits may be a binary indication of an index corresponding to the identified sub-band or wideband. For example, the UE may set the five bits to values of: “00000” to indicate that the CSI feedback is for the wideband, “00001” to indicate that the CSI feedback is for a first sub-band, “00010” to indicate that the CSI feedback is for a second sub-band, “10010” to indicate that the CSI feedback is for an eighteenth sub-band, and so on. In some cases, values for the bits that do not correspond to existing sub-bands may be reserved to indicate other information. The second portion315-amay also include a set of beam parameters P330, which may include N fields or coefficient values, where N may be determined by the number of coefficients C (e.g., amplitude, phase, co-phase), the number of layers L, and the number of non-zero wideband amplitude coefficients per layer Z (e.g., N=C·L·Z). In some cases, the UE may provide CSI feedback for the wideband in one instance and not in subsequent instances (e.g., this feedback may not substantially change in subsequent instances for a low-tier UE). Similarly, the UE may provide CSI feedback for one sub-band in one instance and not in subsequent instances (e.g., may send CSI feedback for different sub-bands in subsequent instances).

In some cases, the UE may be configured for semi-persistent and/or aperiodic CSI reporting. In the cases of semi-persistent and aperiodic CSI reporting, the UE may transmit the first portion310-aof the CSI report305-ausing a control channel (e.g., a PUCCH, such as a long PUCCH) and transmit the second portion315-aof the CSI report305-ausing a shared channel (e.g., a physical uplink shared channel (PUSCH)). Alternatively, in such cases, the UE may transmit the first portion310-aand the second portion315-aof the CSI report305-aon the shared channel. In the case of aperiodic CSI reporting, the UE may transmit the CSI report305-awithout a defined periodicity, for example, based on the occurrence of a trigger (e.g., a request for aperiodic CSI from the base station and/or a condition that the UE or the base station detects, such as a high CQI variation).

In the case of semi-persistent CSI reporting, the UE may transmit the CSI report305-ato the base station periodically at a certain periodicity (e.g., a number of slots). For example, the UE may be configured with a periodicity selected from the set of {5, 10, 20, 30, 80, 160, 320} slots. The UE may, for example, be configured with a relatively longer periodicity if the value for the CSI report305-ais unlikely to substantially vary at less than the periodicity, or the UE may be configured with a relatively shorter periodicity if the value for the CSI report305-ais likely to vary more rapidly.

In some cases of semi-persistent CSI reporting, the UE may autonomously determine whether full-band CSI feedback or partial-band CSI feedback is enabled (e.g., according to a previous configuration), which the UE may indicate in the first portion310-aof the CSI report305-a, as described herein. Additionally or alternatively, the base station may transmit to the UE a CSI feedback configuration (e.g., via higher layer signaling, such as RRC signaling or MAC control element (CE) signaling) indicating whether full-band CSI feedback or partial-band CSI feedback is enabled, which may trigger the UE to enable the indicated CSI reporting scheme accordingly. In some cases, if partial-band CSI feedback is enabled, the UE may determine (e.g., autonomously) whether to transmit wideband-only CQI feedback or CQI feedback for a specific sub-band based on a variation between a wideband CQI measurement and a CQI measurements for one sub-band (e.g., determining to report CSI feedback for a particular sub-band with a relatively high variation). Additionally or alternatively, the UE may determine (e.g., autonomously) whether to transmit wideband-only CQI feedback or CQI feedback for a specific sub-band based on a variation between a wideband value and a sub-band value for the beam combination codebook (e.g., codebook coefficients). For example, the UE may compare a wideband beam amplitude scaling factor to a sub-band beam amplitude scaling factor for one sub-band to determine whether to transmit wideband-only CQI feedback or CQI feedback for a specific sub-band (e.g., the UE may select one specific sub-band for CQI reporting if the variation between the beam amplitude scaling factors is relatively large, indicating, e.g., a relatively large change in channel conditions).

Additionally or alternatively, if partial-band CSI feedback is enabled, the UE may determine (e.g., autonomously) whether to transmit wideband-only CQI feedback or CQI feedback for a specific sub-band based on a code rate for the second portion315-aof the CSI report305-a. For example, the UE may be configured with a particular modulation and coding scheme (MCS) for the CSI feedback, and the configured MCS may indicate a code rate to be used. According to the code for the configured MCS, the UE may determine to report full-band CSI feedback based on a code rate for the second portion315-aof the CSI report305-anot satisfying (e.g., being below or below or equal to) an associated threshold (e.g., a code rate threshold that may be predefined or configured by the base station). If, for example, the code rate for the configured MCS exceeds the associated threshold, the UE may use partial-band CSI feedback until the UE uses a subsequent configuration with a code rate that is below the threshold. In some cases, the code rate threshold may be configured according to a target code rate for data transmissions (e.g., PUSCH transmissions) given the configured MCS. Additionally or alternatively, the code rate threshold may be configured according to an offset value (e.g., a beta offset) associated with the second portion315-aof the CSI report305-a, where the beta offset may define an offset value associated with the currently configured MCS. For example, the beta offset may indicate an offset value for the threshold associated with a correspondingly greater (or lower) MCS.

FIG.3Billustrates an example of a communications scheme300-bthat supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. In some examples, the communications scheme300-bmay implement aspects of the wireless communications system100and the wireless communications system200, as described with reference toFIGS.1and2, respectively. According to the communications scheme300-bshown inFIG.3A, a UE may provide to a base station CSI feedback for a partial bandwidth with multiple sub-band coefficients per corresponding CSI report305(e.g., a CSI report305-b).

As shown in the example communications scheme300-bofFIG.3B, the CSI report305-bmay include a first portion310-band a second portion315-b. The first portion310-bof the CSI report305-bmay include RI, CQI, and an indication of a number of beams per layer having non-zero wideband amplitude coefficients. The second portion315-bof the CSI report305-bmay include PMI values corresponding to the beams having non-zero wideband amplitude coefficients, as indicated in the first portion310-bof the CSI report305-b.

As described herein, the UE may determine a wideband amplitude scaling factor representing an average amplitude of a beam over all reporting sub-bands. Similarly, the UE may determine, for each sub-band, a sub-band amplitude scaling factor representing an amplitude of a beam over a particular reporting sub-band. Further, the UE may determine, for each sub-band, a beam combining coefficient representing a phase or co-phase of a beam over a particular reporting sub-band.

As similarly described with reference toFIG.3A, the first portion310-bof the CSI report305-bmay include an indication of whether partial-band feedback is enabled for the second portion315-bof the CSI report305-b—that is, whether the second portion315-bof the CSI report305-bincludes full-band CSI feedback (i.e., CSI feedback for the full radio-frequency spectrum bandwidth) or partial-band CSI feedback (i.e., CSI feedback for one or more sub-bands of the full radio-frequency spectrum bandwidth). In some cases, the first portion310-bof the CSI report305-bmay have a fixed payload size, where each field of the payload (e.g., fields for the RI, CQI, and each of the indications) may be encoded separately, for example, using independent codewords that may be decoded independently.

For example, the first portion310-bof the CSI report305-bmay include a field with a first bit value (e.g., a bit value of zero), indicating that the CSI feedback in the second portion315-bof the CSI report305-bincludes full-band feedback. The first portion310-bof the CSI report305-bmay further indicate a number of bits (e.g., a payload size, a number of the non-zero wideband amplitude coefficients per layer) of the second portion315-bof the CSI report305-b. According to the first portion310-bof the CSI report305-b, the second portion315-bof the CSI report305-bmay use the indicated number of bits to indicate the determined wideband amplitude scaling factor, sub-band amplitude scaling factor for each sub-band, and the beam combining coefficient for each sub-band (e.g., phase or co-phase feedback).

Alternatively, the indication field of first portion310-bof the CSI report305-bmay be set to a second bit value (e.g., a bit value of one) indicating that the CSI feedback includes partial-band feedback. That is, the second portion315-bof the CSI report305-bmay provide CSI feedback for identified sub-band(s), or for the wideband. In some cases, the second portion315-bof the CSI report305-bmay include a bitmap340indicating a correspondence between the reported CSI feedback values and a corresponding wideband and/or sub-band index. For example, the bitmap340may include M bits (a1a2. . . aM−1aM) indicating such a correspondence, where M is equal to a number of reporting sub-bands that may be derived from a size of the BWP and a size of the sub-band. For example, for each value ai, where i represents an index of an ith sub-band: if ai=1, the CSI report305-bmay include feedback for the ith sub-band, and if ai=0, the CSI report305-bmay not include feedback for the ith sub-band. If, for example, each value of the bitmap is equal to zero, the CSI report305-bmay include feedback for only the wideband. Similarly, if, for example, each value of the bitmap340is equal to one, the CSI report305-bmay include feedback for each sub-band. The second portion315-bmay thus include a set of beam parameters P350, which may include N fields or coefficient values, where N may be determined by the number of coefficients C (e.g., amplitude, phase, co-phase), the number of layers L, the number of non-zero wideband amplitude coefficients per layer Z, and the number of sub-bands M indicated in the bitmap340(e.g., N=C·L·Z·M). In some cases, the UE may provide CSI feedback for the wideband in one instance and not in subsequent instances (e.g., this feedback may not substantially change in subsequent instances for a low-tier UE). Similarly, the UE may provide CSI feedback for the one or more sub-bands in one instance and not in subsequent instances.

In some cases, the UE may be configured for semi-persistent and/or aperiodic CSI reporting. In the cases of semi-persistent and aperiodic CSI reporting, the UE may transmit the first portion310-bof the CSI report305-busing a control channel (e.g., a PUCCH, such as a long PUCCH) and transmit the second portion315-bof the CSI report305-busing a shared channel (e.g., a PUSCH). Alternatively, in such cases, the UE may transmit the first portion310-band the second portion315-bof the CSI report305-bon the shared channel. In the case of aperiodic CSI reporting, the UE may transmit the CSI report305-bwithout a defined periodicity, for example, based on the occurrence of a trigger (e.g., a request for aperiodic CSI from the base station, a condition that the UE or the base station detects, such as a high CQI variation).

In the case of semi-persistent CSI reporting, the UE may transmit the CSI report305-bto the base station periodically at a certain periodicity (e.g., a number of slots). For example, the UE may be configured with a periodicity selected from the set of {5, 10, 20, 30, 80, 160, 320} slots. The UE may, for example, be configured with a relatively longer periodicity if the value for the CSI report305-bis unlikely to substantially vary at less than the periodicity, or the UE may be configured with a relatively shorter periodicity if the value for the CSI report305-bis likely to vary more rapidly.

In some cases of semi-persistent CSI reporting, the UE may autonomously determine whether full-band CSI feedback or partial-band CSI feedback is enabled (e.g., according to a previous configuration), which the UE may indicate in the first portion310-bof the CSI report305-b, as described herein. Additionally or alternatively, base station may transmit to the UE a CSI feedback configuration (e.g., via higher layer signaling, such as RRC signaling or MAC CE signaling) indicating whether full-band CSI feedback or partial-band CSI feedback is enabled, which may trigger the UE to enable the indicated CSI reporting scheme accordingly. In some cases, if partial-band CSI feedback is enabled, the UE may determine (e.g., autonomously) whether to transmit wideband-only CQI feedback or CQI feedback for multiple sub-bands based on a variation between wideband CQI measurement and one or more sub-band CQI measurements (e.g., determining to report CSI feedback for one or more particular sub-bands with a relatively high variation). Additionally or alternatively, the UE may determine (e.g., autonomously) whether to transmit wideband-only CQI feedback or CQI feedback for multiple sub-bands based on a variation between a wideband value and one or more sub-band values for the beam combination codebook (e.g., codebook coefficients). For example, the UE may compare a wideband beam amplitude scaling factor to one or more sub-band beam amplitude scaling factors to determine whether to transmit wideband-only CQI feedback or CQI feedback for one or more particular sub-bands (e.g., the UE may select one or more specific sub-bands for CQI reporting if the variation between the beam amplitude scaling factors is relatively large, indicating, e.g., a relatively large change in channel conditions).

In some examples, the bitmap340may alternatively be represented by a subset selection field, requiring

⌈log2⁡(MK)⌉
bits where

(MK)
represents a number of combinations for selecting K elements from a vector of size M. For example, the first portion310-bof the CSI report305-bmay indicate the number K (e.g., or maximum number) of sub-bands to be selected. The bitmap340may be replaced by a combination index that indicates the K elements. For example, for a set of sub-bands given by Mk[M0M1. . . MK−1], the device may determine a set of values {Xk} based on the equation Xk=Σi=0k−1Mi−1 and the set of Mkvalues, where 0≤Xk≤Z−1 and Z=Σk=0K−1Mk. Using these {Xk} values, the device may calculate the combination index according to ic=Σk=1K−1CXkk, where

Cxy={(xy)x≥y0x<y.
The base station may receive the combination index and determine the indices of the K sub-bands by iteratively determining a sub-band associated with the greatest Cxyvalue less than the combination index for each of the K sub-bands.

Accordingly, the partial-bandwidth CSI reporting techniques described herein may reduce an amount of overhead that a UE may use for CSI reporting versus, for example, full-bandwidth CSI reporting. Moreover, the partial-bandwidth CSI reporting techniques described herein may maintain a level of performance that is substantially equivalent to full-bandwidth CSI reporting and/or provides substantially the same benefits as full-bandwidth CSI reporting. For example, in particular, low-tier and/or cell-edge UEs that may not have a large amount of available resources (e.g., time, frequency, and/or spatial resources) for CSI reporting may report the most significant portions of a full-bandwidth CSI report while conserving limited resources. Moreover, each of these advantages may be further significantly improved in cases of relatively low time-frequency variance in channel conditions (e.g., resulting in a low variance between CSI measurements).

FIG.4shows a payload size table400according to techniques supporting partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. The table shows the payload sizes, given the parameters: (N1, N2)=(4,4), Z=3 (8-PSK phase), and K Leading Coefficients. The payload size table400includes a column405showing the payload size according to full-band CSI reporting (as similarly shown inFIG.3), a column410showing the payload size according the techniques described herein using CSI reports including coefficients for one sub-band per CSI report (as described, e.g., with reference toFIG.3A), and a column415showing the payload size according the techniques described herein using CSI reports including coefficients for five sub-bands (as described, e.g., with reference toFIG.3B). As shown in column410and column415, the techniques described herein provide substantially smaller payloads for CSI reporting as compared to the payload sizes for full-band CSI reporting in column405. For example, according to the payload size table400, for L=2 transmission beams and rank 1 transmissions, a total payload size CSI feedback according to full-band CSI reporting in column405may be 142, while total payload sizes for CSI feedback according to CSI reporting including coefficients for one sub-band coefficient per CSI report and five sub-band coefficients per CSI report may be 34 and 88, respectively, as shown in column410and415. Thus, in either case, the techniques described herein provide a reduction in the total payload sizes for CSI feedback relative to full-band CSI reporting.

FIG.5illustrates an example of a process flow500that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. In some examples, the process flow500may implement aspects of the wireless communications system100or the wireless communications system200, as described with reference toFIGS.1and2, respectively. For example, a base station105and UE115, such as a base station105-band a UE115-b, may perform one or more of the processes described with reference to the process flow500. These processes may be performed according to the communications schemes300-aand300-b, as described with reference toFIGS.3A and3B, respectively. Alternative examples of the following may be implemented, where some steps are performed in a different order than described or are not performed at all. In some cases, steps may include additional features not mentioned below, or further steps may be added.

At505, the base station105-bmay transmit to the UE115-b, and the UE115-bmay receive from the base station105-b, one or more reference signals via one or more respective transmit-receive beam pairs.

At510, the UE115-bmay perform CSI measurements on the one or more reference signal transmissions received from the base station105-bat505via the one or more beams. In some cases, performing CSI measurements on the one or more reference signal transmissions may include determining information indicating a RI, a CQI, and/or a number of non-zero wideband amplitude coefficients per layer. In some cases, performing CSI measurements on the one or more reference signal transmissions may further include determining information indicating a PMI for each of the number of non-zero wideband amplitude coefficients per layer.

At515, the base station105-bmay transmit to the UE115-b, and the UE115-bmay receive from the base station105-b, a CSI feedback configuration. In some cases, the CSI feedback configuration may indicate whether partial CSI feedback is enabled for the beam combination codebook. In some cases, the CSI feedback configuration may further indicate a maximum number of sub-bands for partial CSI feedback in a CSI report.

At520, the UE115-bmay determine whether to generate the CSI report including full CSI feedback for each one or more sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth. In some cases, the CSI report may include indicators of one or more beam parameters (e.g., amplitude, phase, co-phase, etc.) for respective sub-bands. For example, full CSI feedback (or full-band CSI feedback) may include CSI feedback for the full radio-frequency spectrum bandwidth or BWP (e.g., for each of multiple sub-bands of the full bandwidth or of each sub-band of a particular BWP). The CSI feedback may, in some cases, have a configured granularity corresponding to a minimum sub-band size or maximum number of reporting sub-bands. In contrast, partial CSI feedback (or partial-band CSI feedback) may include CSI feedback for a subset of sub-bands of the full radio-frequency spectrum bandwidth or BWP. For example, for a bandwidth configured with 5 sub-bands (e.g., according to a configured granularity), full-band CSI feedback may include CSI feedback for each of the 5 sub-bands, whereas partial-band CSI feedback may include CSI feedback for a subset of the 5 sub-bands (e.g., one or more indicated sub-bands from the 5 sub-bands). In some cases, the UE115-bmay determine whether to generate the CSI report including full CSI feedback or partial CSI feedback based on a variation between a wideband CQI measurement and one or more sub-band CQI measurements and/or a variation between a wideband value for the beam combination codebook one or more sub-band values for the beam combination codebook.

In some cases, the UE115-bmay determine whether to generate the CSI report including full CSI feedback or partial CSI feedback based on a code rate for the second portion of the CSI report, for example, the UE115-bmay determine that the UE115-bis to report the full CSI feedback based on the code rate not satisfying a threshold, and/or the UE115-bmay determine that the UE115-bis to report the partial CSI feedback based on the code rate satisfying (e.g., greater than, greater than or equal to) a threshold. In some cases, the threshold may be based on a target code rate corresponding to an associated MCS and/or an offset value (e.g., a beta offset) corresponding to the associated MCS.

In some cases, the UE115-bmay identify a trigger for transmitting the CSI report to the base station105-b(e.g., a request for aperiodic CSI from the base station105-band/or a condition that the UE115-bor the base station105-bdetects, such as a high CQI variation). The UE115-bmay determine whether to generate the CSI report including full CSI feedback or partial CSI feedback according to the trigger.

At525, the UE115-bmay generate the CSI report for a beam combination codebook (e.g., a Type II codebook, such as an NR Type II codebook) for the one or more beams. In some cases, the CSI report may include a first portion and a second portion. The first portion may include an indication of whether the second portion includes full CSI feedback for each one or more sub-bands of the active bandwidth or partial CSI feedback for the active bandwidth. In some cases, the first portion may further indicate a number of information bits present in the second portion of the CSI report. In some cases, the first portion may further indicate the RI, CQI, and/r the number of non-zero wideband amplitude coefficients per layer, as the UE115-bmay have determined in the CSI measurements at510. The second portion may include the information indicating the PMI, as the UE115-bmay have determined in the CSI measurements at510.

In some cases, the UE115-bmay generate the CSI report according to the determination performed at520. For example, if the UE115-bdetermines at520that the UE115-bis to report partial CSI feedback, the UE115-bmay include in the second portion of the CSI report an indicator that a value of a parameter (e.g., an amplitude, phase, and/or co-phase) in the partial CSI feedback is a wideband value for the active bandwidth. Additionally or alternatively, if the UE115-bdetermines520that the UE115-bis to report the partial CSI feedback, may include in the second portion of the CSI report a sub-band index indicating that a value of a parameter (e.g., an amplitude, phase, and/or co-phase) in the partial CSI feedback is for a sub-band corresponding to the sub-band index. Further additionally or alternatively, if the UE115-bdetermines at520that the UE115-bis to report partial CSI feedback, may include in the second portion of the CSI report a bitmap indicating one or more sub-bands (e.g., multiple sub-bands) associated with corresponding values of one or more parameters of the partial CSI feedback.

Additionally or alternatively, the UE115-bmay generate the CSI report according to the CSI feedback configuration, as the UE115-bmay have received at515(e.g., indicating whether partial CSI feedback is enabled for the beam combination codebook and/or a maximum number of sub-bands for partial CSI feedback in the CSI report).

At530, the UE115-bmay transmit to the base station105-b, and the base station105-bmay receive from the UE115-b, the CSI report, as the UE115-bmay have generated at520. In some cases, the UE115-bmay encode the CSI report, for example, the UE115-bmay separately encode first portion and the second portion of the CSI report. That is, the UE115-bmay encode the first portion using a first encoding process to obtain a first codeword and encode the second portion using a second encoding process to obtain a second codeword. The UE115-bmay transmit each of the encoded codewords.

At535, the base station105-bmay perform a precoding procedure for the set of beams using the CSI report, as the base station105-bmay have received at525. For example, the base station105-bmay perform the precoding procedure using the information indicating the PMI and/or the other parameters included in the CSI feedback.

At540, the base station105-band the UE115-bmay communicate according to the precoding procedure the base station105-bmay have performed at530.

FIG.6shows a block diagram600of a device605that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. The device605may be an example of aspects of a UE115as described herein. The device605may include a receiver610, a communications manager615, and a transmitter620. The device605may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager615may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generate a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmit the CSI report to the base station. The communications manager615may be an example of aspects of the communications manager910described herein.

The communications manager715may be an example of aspects of the communications manager615as described herein. The communications manager715may include a CSI measurement manager720, a CSI report generator725, and a CSI report transmission manager730. The communications manager715may be an example of aspects of the communications manager910described herein.

The CSI measurement manager720may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams.

The CSI report generator725may generate a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth.

The CSI report transmission manager730may transmit the CSI report to the base station.

The transmitter735may transmit signals generated by other components of the device705. In some examples, the transmitter735may be collocated with a receiver710in a transceiver module. For example, the transmitter735may be an example of aspects of the transceiver920described with reference toFIG.9. The transmitter735may utilize a single antenna or a set of antennas.

FIG.8shows a block diagram800of a communications manager805that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. The communications manager805may be an example of aspects of a communications manager615, a communications manager715, or a communications manager910described herein. The communications manager805may include a CSI measurement manager810, a CSI report generator815, a CSI report transmission manager820, a partial CSI feedback manager825, a trigger manager830, and an encoding module835. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The CSI measurement manager810may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams. For example, the CSI measurement manager810may receive (e.g., from a base station) one or more signals840via a transceiver, such as is described with reference toFIG.9) including information indicating the one or more reference signal transmissions, and the CSI measurement manager810may perform the CSI measurements on the one or more received reference signal transmissions. In some examples, performing CSI measurements on the one or more reference signal transmissions includes determining information indicating a RI, a CQI, a number of non-zero wideband amplitude coefficients per layer, or a combination thereof. In some examples, performing CSI measurements on the one or more reference signal transmissions includes determining information indicating a PMI for each of the number of non-zero wideband amplitude coefficients per layer, where the second portion of the CSI report includes the information indicating the PMI. In some examples, the first portion of the CSI report indicates the RI, CQI, and the number of non-zero wideband amplitude coefficients per layer, or the combination thereof.

In some examples, the CSI measurement manager810may pass information845to the CSI report generator815(e.g., directly or indirectly via another component, such as by passing the information845to the partial CSI feedback manager825), where the information845may indicate the measurements performed by the CSI measurement manager810on the one or more reference signal transmissions.

The CSI report generator815may generate a CSI report for a beam combination codebook for the one or more beams (e.g., according to the information845received from the CSI measurement manager810and/or information850received from the partial CSI feedback manager825), where the CSI report includes a first portion and a second portion. The first portion may include an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth. In some examples, the CSI feedback configuration may indicate a maximum number of sub-bands for the partial CSI feedback in the CSI report. In some examples, the first portion of the CSI report may indicate a number of information bits present in the second portion of the CSI report.

In some examples, the CSI report generator815may receive a signal855, for example, from the base station (e.g., via a transceiver, such as is described with reference toFIG.9), including information indicating a CSI feedback configuration indicating whether the partial CSI feedback is enabled for the beam combination codebook. The CSI report generator815may generate the CSI report based on the CSI feedback configuration.

In some examples, the CSI report generator815may determine whether the UE is to report the full CSI feedback or the partial CSI feedback based on a variation between a wideband CQI measurement and one or more sub-band CQI measurements. In some examples, the CSI report generator815may determine whether the UE is to report the full CSI feedback or the partial CSI feedback based on a variation between a wideband value for the beam combination codebook and one or more sub-band values for the beam combination codebook. In some examples, the CSI report generator815may determine whether the UE is to report the full CSI feedback or the partial CSI feedback based on a code rate for the second portion of the CSI report. In some examples, the CSI report generator815may determine that the UE is to report the full CSI feedback based on the code rate not satisfying a threshold. In some examples, the CSI report generator815may determine that the UE is to report the partial CSI feedback based on the code rate satisfying a threshold. In some examples, the threshold may be based on a target code rate corresponding to an MCS and/or an offset value (e.g., a beta offset) corresponding to the associated MCS.

In some examples, the CSI report generator815may pass information860to the CSI report transmission manager820(e.g., directly or indirectly via another component, such as by passing the information860to the encoding module835), where the information860may indicate the generated CSI report.

The CSI report transmission manager820may transmit the CSI report to the base station (e.g., via a transceiver, such as is described with reference toFIG.9), for example, according to the information860received from the CSI report generator815and/or information865received from the encoding module835. For example, the CSI report transmission manager820may transmit one or more signals870including information corresponding to the CSI report using a set of resources (e.g., configured time, frequency, and/or spatial resources). In some examples, transmitting the CSI report includes transmitting the first and second codewords.

The partial CSI feedback manager825may determine that the UE is to report the partial CSI feedback (e.g., according to the information845received from the CSI measurement manager810), where the second portion includes an indicator that a value of a parameter in the partial CSI feedback is a wideband value for the active bandwidth. In some examples, the partial CSI feedback manager825may determine that the UE is to report the partial CSI feedback, where the second portion includes a sub-band index indicating that a value of a parameter in the partial CSI feedback is for a sub-band corresponding to the sub-band index. In some examples, the parameter includes an amplitude indicator (e.g., indicator of an amplitude coefficient for the sub-band index), a phase indicator (e.g., indicator of a phase coefficient for the sub-band index0, a co-phase indicator (e.g., indicator of a differential phase between polarizations or layers for the sub-band index), or a combination thereof.

Additionally or alternatively, the partial CSI feedback manager825may determine that the UE is to report the partial CSI feedback, where the second portion includes a bitmap indicating one or more sub-bands associated with corresponding values of one or more parameters of the partial CSI feedback. In some examples, the parameter may similarly include an amplitude indicator, a phase indicator, a co-phase indicator, or a combination thereof. In some examples, the partial CSI feedback manager825may pass the information850to the CSI report generator815, for example, indicating the determination to report partial CSI feedback.

In some examples, the trigger manager830may identify a trigger for transmitting the CSI report to the base station. In some examples, the trigger manager830may determine whether to generate the CSI report including the full CSI feedback or the partial CSI feedback based on a type of the trigger for transmitting the CSI report to the base station. In some examples, the trigger manager830may pass information875to the CSI report generator815indicating, for example, that the CSI report generator815is to generate the CSI report including the full CSI feedback or the partial CSI feedback based on the trigger, and the CSI report generator815may generate the CSI report according to the information875.

In some examples, the encoding module835may receive information860from the CSI report generator815, for example, indicating the generated CSI report including the first portion and the second portion. In some examples, the encoding module835may encode the first portion using a first encoding process to obtain a first codeword. In some examples, the encoding module835may encode the second portion using a second encoding process to obtain a second codeword.

In some examples, the encoding module835may pass the encoded information865to the CSI report transmission manager820, for example, including encoded CSI report. In some examples, the CSI report transmission manager820may transmit the CSI report including the first and second codewords, for example, according to the encoded information865received from the encoding module835.

FIG.9shows a diagram of a system900including a device905that supports partial-bandwidth feedback for beam combination codebooks in accordance with aspects of the present disclosure. The device905may be an example of or include the components of device605, device705, or a UE115as described herein. The device905may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager910, an I/O controller915, a transceiver920, an antenna925, memory930, and a processor940. These components may be in electronic communication via one or more buses (e.g., bus945).

The communications manager910may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams, generate a CSI report for a beam combination codebook for the one or more beams, the CSI report including a first portion and a second portion, the first portion including an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth, and transmit the CSI report to the base station.

At1005, the UE may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams. For example, the UE may identify time-frequency resources over which the reference signals may be communicated (e.g., from the base station to the UE), and the UE may receive the reference signals over the identified time-frequency resources. The UE may demodulate the information of the received transmission and decode the demodulated information to obtain a set of information bits for each of the respective one or more reference signals. To perform the CSI measurements, the UE may then measure CQI associated with each of the reference signals for their respective beams. The operations of1005may be performed according to the methods described herein. In some examples, aspects of the operations of1005may be performed by a CSI measurement manager as described with reference toFIGS.6through9.

At1010, the UE may generate a CSI report for a beam combination codebook for the one or more beams. The CSI report may include a first portion and a second portion, where the first portion incudes an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth. For example, according to a determination as to whether the UE is to generate full CSI feedback or partial CSI feedback, the UE may generate CSI feedback, for example, including the information obtained via the CSI measurements. The UE may include the CSI feedback in the generated CSI report. The operations of1010may be performed according to the methods described herein. In some examples, aspects of the operations of1010may be performed by a CSI report generator as described with reference toFIGS.6through9.

At1015, the UE may transmit the CSI report to the base station. For example, the UE may identify time-frequency resources over which the CSI report may be transmitted, and the UE may encode and modulate the bits that indicate the CSI report to transmit the encoded and modulated bits over the identified time-frequency resources. The operations of1015may be performed according to the methods described herein. In some examples, aspects of the operations of1015may be performed by a CSI report transmission manager as described with reference toFIGS.6through9.

At1105, the UE may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams. For example, the UE may identify time-frequency resources over which the reference signals may be communicated (e.g., from the base station to the UE), and the UE may receive the reference signals over the identified time-frequency resources. The UE may demodulate the information of the received transmission and decode the demodulated information to obtain a set of information bits for each of the respective one or more reference signals. To perform the CSI measurements, the UE may then measure CQI associated with each of the reference signals for their respective beams. The operations of1105may be performed according to the methods described herein. In some examples, aspects of the operations of1105may be performed by a CSI measurement manager as described with reference toFIGS.6through9.

At1110, the UE may determine that the UE is to report the partial CSI feedback, where the second portion includes an indicator that a value of a parameter in the partial CSI feedback is a wideband value for the active bandwidth. For example, the UE may determine to report partial CSI feedback based on a variation between a wideband CQI measurement and one or more sub-band CQI measurements, based on a variation between a wideband value for the beam combination codebook and one or more sub-band values for the beam combination codebook, and/or based on a code rate for the second portion. The operations of1110may be performed according to the methods described herein. In some examples, aspects of the operations of1110may be performed by a partial CSI feedback manager as described with reference toFIGS.6through9.

At1115, the UE may generate a CSI report for a beam combination codebook for the one or more beams. The CSI report may include a first portion and a second portion, where the first portion incudes an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth. For example, according to the determination that the UE is to generate partial CSI feedback, the UE may generate CSI feedback, for example, including the information obtained via the CSI measurements. The UE may include the CSI feedback in the generated CSI report. The operations of1115may be performed according to the methods described herein. In some examples, aspects of the operations of1115may be performed by a CSI report generator as described with reference toFIGS.6through9.

At1120, the UE may transmit the CSI report to the base station. For example, the UE may identify time-frequency resources over which the CSI report may be transmitted, and the UE may encode and modulate the bits that indicate the CSI report to transmit the encoded and modulated bits over the identified time-frequency resources. The operations of1120may be performed according to the methods described herein. In some examples, aspects of the operations of1120may be performed by a CSI report transmission manager as described with reference toFIGS.6through9.

At1205, the UE may perform CSI measurements on one or more reference signal transmissions from a base station via one or more beams. For example, the UE may identify time-frequency resources over which the reference signals may be communicated (e.g., from the base station to the UE), and the UE may receive the reference signals over the identified time-frequency resources. The UE may demodulate the information of the received transmission and decode the demodulated information to obtain a set of information bits for each of the respective one or more reference signals. To perform the CSI measurements, the UE may then measure CQI associated with each of the reference signals for their respective beams. The operations of1205may be performed according to the methods described herein. In some examples, aspects of the operations of1205may be performed by a CSI measurement manager as described with reference toFIGS.6through9.

At1210, the UE may determine that the UE is to report the partial CSI feedback, where the second portion includes a sub-band index indicating that a value of a parameter in the partial CSI feedback is for a sub-band corresponding to the sub-band index. For example, the UE may determine to report partial CSI feedback based on a variation between a wideband CQI measurement and one or more sub-band CQI measurements, based on a variation between a wideband value for the beam combination codebook and one or more sub-band values for the beam combination codebook, and/or based on a code rate for the second portion. The operations of1210may be performed according to the methods described herein. In some examples, aspects of the operations of1210may be performed by a partial CSI feedback manager as described with reference toFIGS.6through9.

At1215, the UE may generate a CSI report for a beam combination codebook for the one or more beams. The CSI report may include a first portion and a second portion, where the first portion incudes an indication of whether the second portion includes full CSI feedback for each of a set of sub-bands of an active bandwidth or partial CSI feedback for the active bandwidth. For example, according to the determination that the UE is to generate partial CSI feedback, the UE may generate CSI feedback, for example, including the information obtained via the CSI measurements. The UE may include the CSI feedback in the generated CSI report. The operations of1215may be performed according to the methods described herein. In some examples, aspects of the operations of1215may be performed by a CSI report generator as described with reference toFIGS.6through9.

At1220, the UE may transmit the CSI report to the base station. For example, the UE may identify time-frequency resources over which the CSI report may be transmitted, and the UE may encode and modulate the bits that indicate the CSI report to transmit the encoded and modulated bits over the identified time-frequency resources. The operations of1220may be performed according to the methods described herein. In some examples, aspects of the operations of1220may be performed by a CSI report transmission manager as described with reference toFIGS.6through9.