WO2019227403A1

WO2019227403A1 - Channel state information feedback

Info

Publication number: WO2019227403A1
Application number: PCT/CN2018/089287
Authority: WO
Inventors: Hao Liu; Jinping HAO; Rana Ahmed; Keeth Saliya Jayasinghe LADDU; Frederick Vook; William J. Hillery; Xiaomao Mao; Eugene Visotsky
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2018-05-31
Filing date: 2018-05-31
Publication date: 2019-12-05
Also published as: CN112205049A

Abstract

Various communication systems may benefit from channel state information feedback. For example, it may be helpful to improve channel state information feedback using time or frequency compression. According to certain embodiments a method may include determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The method may also include transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

Description

CHANNEL STATE INFORMATION FEEDBACK

BACKGROUND: Field:

Various communication systems may benefit from channel state information feedback. For example, it may be helpful to improve channel state information feedback using time or frequency compression.

Description of the Related Art:

In third generation partnership project (3GPP) technology, such as Long Term Evolution (LTE) , Fifth Generation (5G) , or New Radio (NR) technology, multiple input multiple output (MIMO) may be utilized to help facilitate signal transmission. MIMO is used to increase the overall bitrate through transmission of two or more different data streams on two or more different antennas, using the same resources in both frequency and time, while being separated only through use of different reference signals. In NR technology, the number of antennas and/or data streams will increase, thereby simultaneously increasing the importance of the MIMO.

To allow for use of MIMO in NR technology, channel state information feedback and compression schemes are used. For example, time-domain, frequency-domain, and/or spatial-domain compression are used to compress signal transmission. This may allow multiple signals to be transmitted on multiple antennas using the same frequency and/or time resources.

SUMMARY

According to certain embodiments, an apparatus may include at least one memory including computer program code, and at least one processor. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to determine a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The at least one memory and the computer program code may also be configured, with the at least one processor, to cause the apparatus at least to transmit to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

According to certain embodiments, a method may include determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The method may also include transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

An apparatus, in certain embodiments, may include means for determining a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The apparatus may also include means for transmitting to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

According to certain embodiments, a non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process. The process may include determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The process may also include transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

According to certain other embodiments, a computer program product may encode instructions for performing a process. The process may include determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The process may also include transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

An apparatus, according to certain embodiments, may include circuitry for determining a set of supported channels based on at least one of a first condition and a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The apparatus may also include circuitry for transmitting to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.

According to certain embodiments, an apparatus may include at least one memory including computer program code, and at least one processor. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to receive from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may include a selected number of channel support being greater than and equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The at least one memory and the computer program code may also be configured, with the at least one processor, to cause the apparatus at least to construct a channel state matrix based on the channel support index set comprised in the channel state information report.

According to certain embodiments, a method may include receiving at a network entity from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may comprise a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may comprise a variance of a residual matrix being smaller than or equal to a threshold variance. The method may also include constructing a channel state matrix based on the channel support index set comprised in the channel state information report.

An apparatus, in certain embodiments, may include means for receiving from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may comprise a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may comprise a variance of a residual matrix being smaller than or equal to a threshold variance. The apparatus may also include means for constructing a channel state matrix based on the channel support index set comprised in the channel state information report.

According to certain embodiments, a non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform a process. The process may include receiving at a network entity from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may comprise a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may comprise a variance of a residual matrix being smaller than or equal to a threshold variance. The process may also include constructing a channel state matrix based on the channel support index set comprised in the channel state information report.

According to certain other embodiments, a computer program product may encode instructions for performing a process. The process may include receiving at a network entity from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition and a second condition are met. The first condition may comprise a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may comprise a variance of a residual matrix being smaller than or equal to a threshold variance. The process may also include constructing a channel state matrix based on the channel support index set comprised in the channel state information report.

An apparatus, according to certain embodiments, may include circuitry for receiving from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may comprise a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may comprise a variance of a residual matrix being smaller than or equal to a threshold variance. The apparatus may also include circuitry for constructing a channel state matrix based on the channel support index set comprised in the channel state information report.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of the example embodiments of the invention, reference should be made to the accompanying drawings, wherein:

FIG. 1 illustrates an example of a table according to certain embodiments.

FIG. 2 illustrates an example of a diagram according to certain embodiments.

FIG. 3 illustrates an example of a method according to certain embodiments.

FIG. 4 illustrates an example of a method according to certain embodiments.

FIG. 5 illustrates an example of a system according to certain embodiments.

DETAILED DESCRIPTION

Certain embodiments allow for reducing overhead by enhancing channel state information feedback. In particular, certain embodiments provide for use of finer feedback granularity and feedback. The feedback granularity and accuracy, for example, may allow for improving channel state information feedback on a sub-band level. In addition, certain embodiments may help to improve overall system or network performance, thereby reducing the overhead associated with channel state information feedback.

Channel state information feedback may be transmitted from a user equipment to a network entity. The network entity, for example, may be a 5G or NR NodeB (gNB) . Channel state information feedback may be based on an orthogonal matching pursuit (OMP) algorithm of compressive sensing (CS) , which may utilize time domain channel compression techniques. OMP algorithm, for example, may be a sparse approximation that involves finding a best matching projection of multidimensional data onto the span of a dictionary. The dictionary may be a collection of unit-norm elementary building blocks for a signal space. The unit-norm vectors may be called atoms. If the atoms of the dictionary span the entire signal space, the dictionary may be complete. When using OMP, the coefficients extracted may be updated by computing an orthogonal projection of a signal onto the set of atoms.

Common channel support, in some embodiments, may speed up the convergence of the OMP. The channel support may be the location of the time domain channel taps in a channel impulse response (CIR) , and may be related to a power-delay profile. In 5G or NR technology, co-located transmit or receive antennas and/or transmit or receive beams formed from co-located transmit or receive antennas may share the same dominant taps. The dominant taps may be referred to as supported channels, in some embodiments.

In certain embodiments, a frequency domain channel matrix H _FD may be acquired across channel state information reference signal measurements. H _FD may have dimensions of N _f x N _p, where N _f is a number of active subcarriers, and N _p is a number of transmit antenna ports multiplied by the number of receive antenna ports. Frequency domain channel matrix H _FD may be compressed into a new matrix H _TD, called compressed time domain channel matrix, according to the following equation:

H _TD may have a lower dimension of N _t x N _p, where N _t may be less than the number of active subcarriers N _f.

may be a linear transformation matrix that includes Discrete Fourier Transformation (DFT) vector columns of N _t dominant taps.

The dominant taps may be selected according to time domain compression, such as OMP. In certain embodiments, an initial residual matrix R ₀ = H _FD, may have a tap index set

iteration counter l = 0, DFT matrix

including chosen taps, and candidate set C ₀ = {1, 2, ..., N _f} . The measurement matrix Φ may be defined with dimension of, for example, N _f × N _f designed for using the available channel frequency response, built as a submatrix of the N _fft × N _fft DFT matrix, where N _fft is the number of the whole subcarriers. The rows of Φ may correspond to the locations of the active subcarriers, and the columns of Φ may correspond to the channel support range. l may then be incremented and tap index λ _l may be found, where

being the i-th column of R _l-1 and

being DFT vector of tap j (one column in the measurement matrix Φ) , according to the following equation:

The tap index set and DFT matrix of chosen taps may then be augmented according to the above equation: Λ _l = Λ _l-1 ∪ {λ _l} , and

A new signal estimate X _l = Φ _l ^HH _FD may be obtained, and the new residual matrix R _l = H _FD-Φ _lX _l may be calculated. Candidate set C _l = C _l-1/ {λ _l} may be updated, in which the operation “/” means that the element λ _l is removed from the set C _l-1. l may be incremented, and tap index λ _l may be found when some criteria is satisfied, such as l ＜ N _t or a projection mean-square error (MSE) rule.

Channel state information feedback signaling may be based on a time domain compression, such as OMP. For example, channel state information may include a selected tap index set Λ, where the tap index set may be the channel support for a given transmission. Alternatively, or in addition to, channel state information may include coefficients of compressed time domain channel matrix H _TD. In some embodiments, one or more higher layer parameters may be configured using radio resource control (RRC) .

In certain embodiments, a selection of tap index set may be performed after at least one of two different conditions are satisfied or met. A tap may also be referred to as a channel support. The first condition, for example, may be that a selected number of supported taps is greater than or equal to a configured number of supported taps. The configured number of supported taps, for example, may be a maximum. For example, the number of selected taps N _tap may not be less than the configured tap number N _t. The configured tap number N _t may be received at the user equipment from the network entity. In some other embodiments, the configured tap number N _t may be pre-configured based on a user equipment category. The second condition may be that a variance of a residual matrix is smaller than or equal to a threshold variance. For example, the variance of residual matrix R _l may be no larger than a threshold variance, such as the variance of channel matrix H _FD multiplied by a threshold factor α, where α ∈ [0, 1] . Threshold factor α may be received by the user equipment from the network entity. In other words, ||R _l|| ² ≤ α ||H _FD|| ². Using the above at least one of two conditions as selection criteria may help to reduce feedback overhead, while also ensuring selection of the dominant taps for each user equipment.

In some embodiments, the number of selected channel support, also referred to as N _tap, may be less than the configured tap number N _t for some user equipment. Tap index set

may be common for an N _p number of pairs of transmit and receive antenna ports. The tap index set may be encoded jointly with

bits, in which N _tap dominant taps are selected from N _f candidate taps. A channel state information report including a channel support index set may therefore be transmitted in a long feedback periodicity. In some embodiments, the channel support index set may have a longer feedback period than coefficients of the compressed time domain channel. The channel support index set may be based on the selected channel support.

The tap index set, in certain embodiments, may be encoded separately with

bits. Joint encoding may be used, in some embodiments, instead of separate encoding, in order to reduce feedback overhead. For example, joint encoding may reduce channel state information payload by 26 percent as compared to separate encoding, assuming an N _f = 600 and an N _tap= 8.

The feedback, in certain embodiments, may include one or more coefficients of a time compressed matrix H _TD. Compressed matrix

has N _tap × N _p coefficients, where

The strongest coefficient may be selected from N _tap × N _p coefficients, and its index may be quantized as

In other words, a strongest coefficient of the compressed time domain channel matrix may be determined. An index of the strongest coefficient may then be quantized, and the quantized index may be included in the transmitted channel state information report.

In some embodiments, an amplitude and/or phase of the strongest coefficient may be quantized. The amplitude and phase of all the other coefficients, other than the strongest coefficient, may also be quantized, in certain embodiments. The quantized amplitude and phase may also be reported as part of the channel state information report from the user equipment to the network entity, for example a gNB. The network entity may use the quantized amplitude and phase to reconstruct the whole channel information. For example, the amplitude and phase may be used to reconstruct channel matrix H _FD composed of slow and fast fading channel information. The channel matrix may also be reconstructed using at least one of H _TD and/or

In certain embodiments, the amplitude value of the strongest coefficient may be quantized based on a reference signal received power (RSRP) of the user equipment. The amplitude value, for example, may be a ratio of 10 × log 10 (Amp ²/RSRP) , where Amp may be the amplitude of the strongest coefficient, and RSRP may be the user equipment reported RSRP value during a long duration for a feedback or a long feedback periodicity. The ratio, in some embodiments, may be reported similarly to channel quality indication (CQI) levels with a quantization level of 4 bits, or a quantization level of any other value. The amplitude of the strongest coefficient for different user equipment may have a very wide, dynamic range. Direct quantization of the amplitude, therefore, may lead to large feedback overhead. Amplitude quantization using the above ratio, however, may be an effective way of providing feedback for the strongest coefficient that minimizes feedback overhead.

The other (N _tap × N _p -1) coefficients of the compressed matrix H _TD, other than the strongest coefficient, may be divided by the strongest coefficient, and then quantized separately in terms of amplitude and phase. In certain embodiments, the strongest coefficient and the other (N _tap × N _p -1) coefficients in time compressed matrix H _TD may be reported separately. The user equipment, for example, may report the strongest coefficient or the other coefficients over a physical uplink shared channel (PUSCH) to a network entity.

In certain embodiments, the user equipment may receive a signal including one or more higher layer parameters from the network entity. The one or more higher layer parameters may be configured statically or semi-statically in advance or before the channel state information report is transmitted. The one or more higher layer parameters may include at least one of a number of dominant taps N _t, threshold factor α, and/or a DFT matrix configuration with or without oversampling or subsampling. The DFT matrix may be composed of multiple DFT column vectors each having N _f elements. Oversampling may mean that the number of DFT vectors is larger than the value N _f, while subsampling may mean that the number of DFT vectors is less than the value N _f, otherwise the number may be equal to N _f. The quantization set and/or the quantization bits of amplitude and phase may be configured for the strongest coefficient and the other coefficients, respectively. Some of the embodiments described above may help to improve system performance, while also providing for finer frequency granularity and higher feedback accuracy.

The network entity, such as gNB, may receive channel state information report from a user equipment. The channel state information may be received using a selected number of channel support. The network entity may reconstruct or construct a channel state matrix based on the channel state information included in the channel state information report. In certain embodiments, the channel state matrix, for example, may be restored using the following equation:

FIG. 1 illustrates an example of a table according to certain embodiments. In particular, FIG. 1 illustrates an example of a payload statistic for channel state information feedback according to certain embodiments. The number of transmit antenna ports may be 16 with (N ₁, N ₂) = (4, 2) . The number of receive antenna ports, for example, may be 2, the number of active subcarriers may be N _f = 600, the threshold factor may be α = 0.1, and the DFT matrix may have the dimension of 600 x 600. The strongest coefficient of compressed matrix H _TD may have 4-bit phase quantization and 4-bit amplitude quantization, and other coefficients of the compressed matrix H _TD may have 4-bit phase quantization and 3-bit amplitude quantization.

As seen in FIG. 1, the number of dominant taps N _t 110 may be set to 2, 5, and 10. According to the statistics shown in FIG. 1, the selected tap number N _tap may generally be less than N _t, with a mean or average number of the selected tap being 1.9, 4.3, and 7.1 for different configured tap numbers of 2, 5, and 10, respectively. FIG. 1 also illustrates tap feedback 120, including tap indication and tap selection, as well as strongest coefficient 130, including an index, an amplitude, and a phase. In addition, FIG. 1 illustrates the amplitude or phase of other coefficients 140. The total payload for configured

tap numbers

2, 5, and 10, respectively, may be equal to a total payload of 451, 1014, and 1662. The total payload in certain embodiments, therefore, may increase as the configured tap number increases. In other words, the channels state information feedback overhead increases as the number of channel support increases.

FIG. 2 illustrates an example of a diagram according to certain embodiments. In particular, FIG. 2 illustrates that the channel state information payload of XYZ type 210 may be 425 bits. On the other hand, the explicit channel state information 220 may have a configured tap of 2 and a total payload of 451 bits, while explicit channel state information 230 may have a configured tap of 5 and a total payload of 1014 bits. Explicit channel state information 240 may have a configured tap of 10 and a total payload of 1662 bits.

Certain embodiments that utilize explicit channel state information feedback and/or frequency compression may cause significant improvements to system performance when increasing the configured tap number. In other words, using a finer frequency granularity and higher feedback accuracy may help to improve system performance.

Specifically, as shown in FIGS. 1 and 2 certain embodiments may have explicit channel state information having a configured tap of 2, 5, and 10. The cell average spectrum efficiency (SE) bits per second (bps) /hertz (Hz) may be 3.86, 4.38, and 4.50, corresponding to configured

tap numbers

2, 5, and 10. The 5%cell edge SE may be 0.066 bps/Hz, 0.071 bps/Hz, and 0.072 bps/Hz, respectively for a configured tap of 2, 5, and 10. The average cell SE percentage increase caused by some of the above embodiments may therefore be 12%, 27%, and 31%, for a configured tap of 2, 5, and 10, respectively, over an XYZ type channel state information. The cell edge SE gain percentage increase caused by some of the above embodiments, on the other hand, may be 5%, 13%, and 14%, for a configured 2, 5, and 10, respectively, over an XYZ type channel state information.

FIG. 3 illustrates an example of a method according to certain embodiments. In particular, FIG. 3 illustrates a method performed by a user equipment. In step 310, the user equipment may receive a signal including one or more higher layer parameters from the network entity. The one or more higher layer parameters may be the configured number of channel support, the threshold factor, Discrete Fourier Transform matrix configuration with or without oversampling or subsampling, the quantized index set, and/or a quantization bit of the amplitude and phase of the strongest coefficient or the other coefficients. The supported channels or channel support may be referred to as taps. In some embodiments, the signal may be an RRC signal. The one or more layer parameters may be configured statically or semi-statically.

In step 320, the user equipment may determine a set of supported channels based on at least one of a first condition or a second condition. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. The configured number of supported channels, for example, may be received at the user equipment in step 310. The threshold variance, for example, may depend on a variance of a channel matrix and a threshold factor, which may be received by the user equipment in step 310. In some embodiments, the selected number of channel support may be greater than or equal to the configured number of channel support and the variance of the residual matrix may be smaller than or equal to the threshold variance simultaneously.

In step 330, the user equipment may determine a strongest coefficient of a compressed time domain channel matrix. The user equipment may quantize an index of the strongest coefficient of the compressed time domain channel matrix. The quantized index may be included in the transmitted channel state information report. Alternatively or additionally, the user equipment may quantize an amplitude and phase of at least one of the strongest coefficient or other coefficients of the compressed time domain channel matrix, as shown in step 340. The quantized amplitude and phase may be included in the transmitted channel state information report. The amplitude of the strongest coefficient, for example, may be quantized based on a ratio of the amplitude and a reference signal received power of the user equipment.

In step 350, the user equipment may transmit a channel state information report to a network entity including a channel support index set, based on the set of supported channels, after determining that at least one of the first condition and the second condition have been met. The channel support index set may be common for one or more pairs of transmit and receive antenna ports. In certain other embodiments, the channel state information report may also include a quantized index of the strongest coefficient of the compressed time domain channel matrix and/or a quantized amplitude and phase of at least one of the strongest coefficient or other coefficients.

FIG. 4 illustrates an example of a method according to certain embodiments. In particular, FIG. 4 illustrates a method performed by a network entity, for example a gNB. The network entity illustrated in FIG. 4 may communicate with the user equipment illustrated in FIG. 3. In step 410, the network entity may transmit a signal comprising one or more higher layer parameters to the user equipment. The one or more higher layer parameters may include at least one of the configured number of channel support, a threshold factor, or a Discrete Fourier Transform matrix configuration, the quantized index set, and/or a quantization bit of the amplitude and phase of the strongest coefficient of the other coefficients. The signal, for example, may be an RRC signal. The one or more higher layer parameters may be configured statically or semi-statically.

In step 420, the network entity receive from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met. The first condition may include a selected number of channel support being greater than or equal to a configured number of channel support. The second condition may include a variance of a residual matrix being smaller than or equal to a threshold variance. In certain embodiments, the channel support index set may be common for one or more pairs of transmit and receive antenna ports.

In step 430, the network entity may receive from the user equipment a quantized index of a strongest coefficient of a compressed time domain channel matrix in the channel state information report. In step 440, the network entity may receive from the user equipment a quantized amplitude and phase of at least one of the strongest coefficient or other coefficients of the compressed time domain channel matrix in the channel state information report. In step 450, the network entity may reconstruct or construct a channel state matrix based on the channel support index set included in the channel state information report. In some other embodiments, the channel state matrix may be reconstructed or constructed based on at least one of the quantized index of the strongest coefficient, and/or the quantized amplitude and phase of at least one of a strongest coefficient or other coefficients of the compressed time domain channel matrix.

FIG. 5 illustrates a system according to certain embodiments. It should be understood that each signal or block in FIGS. 1-4 may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. In one embodiment, a system may include several devices, such as, for example, network entity 520 or user equipment (UE) 510. The system may include more than one UE 510 and more than one network entity 520. Network entity 520 may be a network node, a base station, an access point, an access node, a gNB, an eNodeB (eNB) , a server, a host, or any other network entity that may communicate with the UE.

Each of these devices may include at least one processor or control unit or module, respectively indicated as 511 and 521. At least one memory may be provided in each device, and indicated as 512 and 522, respectively. The memory may include computer program instructions or computer code contained therein. One or

more transceiver

513 and 523 may be provided, and each device may also include an antenna, respectively illustrated as 514 and 524. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, network entity 520 and UE 510 may be additionally configured for wired communication, in addition to wireless communication, and in such a

case antennas

514 and 524 may illustrate any form of communication hardware, without being limited to merely an antenna.

Transceivers

513 and 523 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself, but in a mast, for example. The operations and functionalities may be performed in different entities, such as nodes, hosts or servers, in a flexible manner. In other words, division of labor may vary case by case. One possible use is to make a network entity deliver local content. One or more functionalities may also be implemented as virtual application (s) in software that can run on a server.

A user device or UE 510 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device, an IoT cellular device, a computer, such as a tablet, provided with wireless communication capabilities, personal data or digital assistant (PDA) provided with wireless communication capabilities, portable media player, digital camera, pocket video camera, navigation unit provided with wireless communication capabilities or any combinations thereof. In other embodiments, the user equipment may be replaced with a machine communication device that does not require any human interaction, such as a sensor, meter, or robot.

In some embodiments, an apparatus, such as a user equipment or a network entity, may include means for carrying out embodiments described above in relation to FIGS. 1-4. In certain embodiments, at least one memory including computer program code can be configured to, with the at least one processor, cause the apparatus at least to perform any of the processes described herein.

Processors

511 and 521 may be embodied by any computational or data processing device, such as a central processing unit (CPU) , digital signal processor (DSP) , application specific integrated circuit (ASIC) , programmable logic devices (PLDs) , field programmable gate arrays (FPGAs) , digitally enhanced circuits, or comparable device or a combination thereof. The processors may be implemented as a single controller, or a plurality of controllers or processors.

For firmware or software, the implementation may include modules or unit of at least one chip set (for example, procedures, functions, and so on) .

Memories

512 and 522 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD) , random access memory (RAM) , flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof, such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as network entity 520 or UE 510, to perform any of the processes described above (see, for example, FIGS. 1-4) . Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine, applet or macro) that, when executed in hardware, may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language, which may be a high-level programming language, such as objective-C, C, C++, C#, Java, etc., or a low-level programming language, such as a machine language, or assembler. Alternatively, certain embodiments may be performed entirely in hardware.

In certain embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 1-4. Circuitry, in one example, may be hardware-only circuit implementations, such as analog and/or digital circuitry. Circuitry, in another example, may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuit (s) with software or firmware, and/or any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and at least one memory that work together to cause an apparatus to perform various processes or functions. In yet another example, circuitry may be hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that include software, such as firmware for operation. Software in circuitry may not be present when it is not needed for the operation of the hardware.

The above embodiments may be directed to computer-related technology that provides significant improvements to the functioning of a network and/or to the functioning of the network entities within the network, or the user equipment communicating with the network. For example, the above embodiments may help to improve system or network performance, while allowing for finer frequency granularity and higher accuracy for channel state information feedback. Improving the system or network performance, may help to reduce channel state information feedback overhead, thereby reducing network resource usage and/or resource usage at the user equipment.

The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “certain embodiments, ” “some embodiments, ” “other embodiments, ” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one example embodiment of the present invention. Thus, appearance of the phrases “in certain embodiments, ” “in some embodiments, ” “in other embodiments, ” or other similar language, throughout this specification does not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

One having ordinary skill in the art will readily understand that the example embodiments of the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the examples of the invention have been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. Although the above embodiments refer to 5G NR, the above embodiments may also apply to any other present or future 3GPP technology, such as LTE, LTE-advanced, IoT technology, fourth generation (4G) technology, or any non-3GPP technology.

Partial Glossary

3GPP 3rd Generation Partnership Project

CIR Channel Impulse Response

CQI Channel Quality Indication

CS Compressive Sensing

CSI Channel State Information

DFT Discrete Fourier Transform

LTE Long-Term Evolution

MIMO Multiple-Input Multiple-Output

MU-MIMO Multi-user MIMO

NR New Radio

OMP Orthogonal Matching Pursuit

PUSCH Physical Uplink Shared Channel

RRC Radio Resource Control

SB Subband

SE Spectrum Efficiency

ULA Uniform Linear Array

WB Wideband

Claims

An apparatus comprising:

at least one processor; and

at least one memory and computer program code, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

determine a set of supported channels based on at least one of a first condition or a second condition, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

transmit to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.
The apparatus according to claim 1, wherein the channel support index set is common for one or more pairs of transmit and receive antenna ports.
The apparatus according to claim 1 or 2, wherein the selected number of channel support is greater than or equal to the configured number of channel support and the variance of the residual matrix is smaller than or equal to the threshold variance simultaneously.
The apparatus according to any of claims 1-3, wherein the threshold variance depends on a variance of a time domain channel matrix and a threshold factor.
The apparatus according to any of claims 1-4, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

determine a strongest coefficient of a compressed time domain channel matrix.
The apparatus according to claim 5, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

quantize an index of the strongest coefficient of the compressed time domain channel matrix, wherein the quantized index is included in the transmitted channel state information report.
The apparatus according to claim 5 or 6, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

quantize an amplitude and phase of at least one of the strongest coefficient or other coefficients of the compressed time domain channel matrix, wherein the quantized amplitude and phase are included in the transmitted channel state information.
The apparatus according to claim 7, wherein the amplitude of the strongest coefficient is quantized based on a ratio of the amplitude and a reference signal received power of the apparatus.
The apparatus according to any of claims 1-8, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

receive a signal comprising one or more higher layer parameters from the network entity, wherein the one or more higher layer parameters comprise at least one of the configured number of channel support, the threshold factor, a Discrete Fourier Transform matrix configuration, the quantized index set, or a quantization bit of the amplitude and phase of the strongest coefficient or other coefficients.
The apparatus according to claim 9, wherein the signal is a radio resource control signal.
The apparatus according to claim 9 or 10, wherein the one or more higher layer parameters are configured statically or semi-statically.
An apparatus comprising:

at least one processor; and

at least one memory and computer program code, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

receive from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

construct a channel state matrix based on the channel support index set comprised in the channel state information report.
The apparatus according to claim 12, wherein the channel support index set is common for one or more pairs of transmit and receive antenna ports.
The apparatus according to claim 12 or 13, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

receive a quantized index of a strongest coefficient of a compressed time domain channel matrix in the channel state information report, wherein the quantized index is used to construct the channel state matrix.
The apparatus according to any of claims 12-14, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

receive a quantized amplitude and phase of at least one of a strongest coefficient or other coefficients of a compressed time domain channel matrix in the channel state information report, wherein the quantized amplitude and phase are used to construct the channel state matrix.
The apparatus according to any of claims 12-15, wherein the at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to:

transmit a signal comprising one or more higher layer parameters to the user equipment, wherein the one or more higher layer parameters comprise at least one of the configured number of channel support, a threshold factor, a Discrete Fourier Transform matrix configuration, the quantized index set, or a quantization bit of the amplitude and phase of the strongest coefficient or other coefficients.
The apparatus according to claim 16, wherein the signal is a radio resource control signal.
The apparatus according to claims 16 or 17, wherein the one or more higher layer parameters are configured statically or semi-statically.
An apparatus comprising:

means for determining a set of supported channels based on at least one of a first condition or a second condition, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance;

means for transmitting to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or second condition have been met.
An apparatus comprising:

means for receiving from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

means for constructing a channel state matrix based on the channel support index set comprised in the channel state information report.
A method comprising:

determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.
The method according to claim 21, wherein the channel support index set is common for one or more pairs of transmit and receive antenna ports.
The method according to claims 21 or 22, wherein the selected number of channel support is greater than or equal to the configured number of channel support and the variance of the residual matrix is smaller than or equal to the threshold variance simultaneously.
The method according to any of claims 21-23, wherein the threshold variance depends on a variance of a time domain channel matrix and a threshold factor.
The method according to any of claims 21-24, further comprising:

determining a strongest coefficient of a compressed time domain channel matrix.
The method according to claim 25, further comprising:

quantizing an index of the strongest coefficient of the compressed time domain channel matrix, wherein the quantized index is included in the transmitted channel state information report.
The method according to claim 25 or 26, further comprising:

quantizing an amplitude and phase of at least one of the strongest coefficient or other coefficients of the compressed time domain channel matrix, wherein the quantized amplitude and phase are included in the transmitted channel state information.
The method according to claim 27, wherein the amplitude of the strongest coefficient is quantized based on a ratio of the amplitude and a reference signal received power of the user equipment.
The method according to any of claims 21-28, further comprising:

receiving a signal at a user equipment comprising one or more higher layer parameters from the network entity, wherein the one or more higher layer parameters comprise at least one of the configured number of channel support, the threshold factor, a Discrete Fourier Transform matrix configuration, the quantized index set, or a quantization bit of the amplitude and phase of the strongest coefficient or other coefficients.
The method according to claim 29, wherein the signal is a radio resource control signal.
The method according to claim 29 or 30, wherein the one or more higher layer parameters are configured statically or semi-statically.
A method comprising:

receiving at a network entity from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

constructing a channel state matrix based on the channel support index set comprised in the channel state information report.
The method according to claim 32, wherein the channel support index set is common for one or more pairs of transmit and receive antenna ports.
The method according to claim 32 or 33, further comprising:

receiving a quantized index of a strongest coefficient of a compressed time domain channel matrix in the channel state information report, wherein the quantized index is used to construct the channel state matrix.
The method according to any of claims 32-34, further comprising:

receiving a quantized amplitude and phase of at least one of a strongest coefficient or other coefficients of a compressed time domain channel matrix in the channel state information report, wherein the quantized amplitude and phase are used to construct the channel state matrix.
The method according to any of claims 32-35, further comprising:

transmitting a signal comprising one or more higher layer parameters to the user equipment, wherein the one or more higher layer parameters comprise at least one of the configured number of channel support, a threshold factor, a Discrete Fourier Transform matrix configuration, the quantized index set, or a quantization bit of the amplitude and phase of the strongest coefficient or other coefficients.
The method according to claim 36, wherein the signal is a radio resource control signal.
The method according to claims 36 or 37, wherein the one or more higher layer parameters are configured statically or semi-statically.
A computer program product encoding instructions for performing a process, the process comprising:

determining at a user equipment a set of supported channels based on at least one of a first condition or a second condition, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

transmitting from the user equipment to a network entity a channel state information report comprising a channel support index set, based on the set of supported channels, after determining that at least one of the first condition or the second condition have been met.
A computer program product encoding instructions for performing a process, the process comprising:

receiving at a network entity from a user equipment a channel state information report comprising a channel support index set, based on a set of supported channels, after at least one of a first condition or a second condition are met, wherein the first condition comprises a selected number of channel support being greater than or equal to a configured number of channel support, and wherein the second condition comprises a variance of a residual matrix being smaller than or equal to a threshold variance; and

constructing a channel state matrix based on the channel support index set comprised in the channel state information report.