WO2019033383A1

WO2019033383A1 - Wideband amplitude based codebook subset restriction

Info

Publication number: WO2019033383A1
Application number: PCT/CN2017/097986
Authority: WO
Inventors: Hao Liu; Jinping HAO; William J. Hillery
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2017-08-18
Filing date: 2017-08-18
Publication date: 2019-02-21
Also published as: CN110999114B; CN110999114A

Abstract

Implementations of the present disclosure relate to methods and devices for codebook subset restriction. In example implementations, a method implemented by a network device in a communication system is provided. The method includes determining, based on a first wideband (WB) amplitude quantization set including a first number of power levels, a second WB amplitude quantization set including a second number of power levels, the second number being less than the first number. The method also includes transmitting, to a terminal device served by the network device, an indication of the second WB amplitude quantization set. The method further includes receiving channel state information (CSI) from the terminal device, the CSI being determined by the terminal device at least based on the second WB amplitude quantization set.

Description

WIDEBAND AMPLITUDE BASED CODEBOOK SUBSET RESTRICTION

TECHNICAL FIELD

Implementations of the present disclosure generally relate to the field of telecommunication， and in particular， to methods and devices for codebook subset restriction (CSR) .

BACKGROUND

Massive Multiple Input Multiple Output (MIMO) technique has remarkable capabilities to improve the performance of a communication system， such as a 5G new radio (NR) system. In addition， due to full multiplexing gain and significant throughput improvement by linear precoding at a transmitter of the system， multi-user MIMO (MU-MIMO) technique has become a key enabler to meet ever-increasing performance requirements for massive MIMO. The accuracy of channel state information (CSI) has a significant influence on MU-MIMO scheduling performance in Frequency Division Duplex (FDD) configuration. However， relatively high accuracy of CSI usually means relatively high overhead for CSI feedback. Therefore， how to balance the high accuracy of CSI with suitable overhead for CSI feedback has become a great challenge in the 5G NR system.

At present， two types of codebook have been designed for different accuracies of CSI. For example， Linear Combination (LC) codebook is widely accepted as a codebook for high-accuracy CSI. LC codebook is a dual-stage codebook structure， which can be represented as W ＝ W1 × W2. The first stage W1 consists of a set of L orthogonal beams selected from the predefined oversampled two-dimensional (2D) Discrete Fourier Transform (DFT) beams for a single polarization， and the selection of the L beams is realized in wideband (WB) . The second stage W2 consists of 2L-1 beam combining coefficients for the L beams and two polarizations. Generally， the beam combining coefficients can be divided into phase combining coefficients and amplitude scaling coefficients. Due to the separate quantization of the phase combining coefficients and the amplitude scaling coefficients， LC codebook may be associated with huge overhead for CSI feedback. Therefore， there is a need for a solution to reduce the CSI feedback overhead for LC codebook.

SUMMARY

In general， example implementations of the present disclosure provide methods and devices for CSR.

In a first aspect， there is provided a method implemented by a network device in a communication system is provided. The method includes determining， based on a first wideband (WB) amplitude quantization set including a first number of power levels， a second WB amplitude quantization set including a second number of power levels. The second number is less than the first number. The method also includes transmitting， to a terminal device served by the network device， an indication of the second WB amplitude quantization set. The method further includes receiving channel state information (CSI) from the terminal device， the CSI being determined by the terminal device at least based on the second WB amplitude quantization set.

In a second aspect， there is provided a method implemented by a terminal device in a communication system. The method includes receiving， from a network device serving the terminal device， an indication of a second wideband (WB) amplitude quantization set including a second number of power levels. The second WB amplitude quantization set is determined by the network device based on a first WB amplitude quantization set including a first number of power levels. The second number is less than the first number. The method also includes determining channel state information (CSI) at least based on the second WB amplitude quantization set. The method further includes transmitting the CSI to the network device.

In a third aspect， there is provided a network device. The network device includes a processor； and a memory coupled to the processing unit and storing instructions thereon， the instructions， when executed by the processing unit， causing the network device to perform actions. The actions comprise determining， based on a first wideband (WB) amplitude quantization set including a first number of power levels， a second WB amplitude quantization set including a second number of power levels. The second number is less than the first number. The actions also comprise transmitting， to a terminal device served by the network device， an indication of the second WB amplitude quantization set. The actions further comprise receiving channel state information (CSI) from the terminal device， the CSI being determined by the terminal device at least based on the second WB amplitude quantization set.

In a fourth aspect， there is provided a terminal device. The terminal device includes a processor； and a memory coupled to the processing unit and storing instructions thereon， the instructions， when executed by the processing unit， causing the terminal device to perform actions. The actions comprise receiving， from a network device serving the terminal device， an indication of a second wideband (WB) amplitude quantization set including a second number of power levels. The second WB amplitude quantization set is determined by the network device based on a first WB amplitude quantization set including a first number of power levels. The second number is less than the first number. The actions also comprise determining channel state information (CSI) at least based on the second WB amplitude quantization set. The actions further comprise transmitting the CSI to the network device.

In a fifth aspect， there is provided a computer readable medium having instructions stored thereon. The instructions， when executed on at least one processor， cause the at least one processor to carry out the method according to the first aspect.

In a sixth aspect， there is provided a computer readable medium having instructions stored thereon. The instructions， when executed on at least one processor， cause the at least one processor to carry out the method according to the second aspect.

In a seventh aspect， there is provided a computer program product that is tangibly stored on a computer readable storage medium. The computer program product includes instructions which， when executed on at least one processor， cause the at least one processor to carry out the method according to the first aspect or the second aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some implementations of the present disclosure in the accompanying drawings， the above and other objects， features and advantages of the present disclosure will become more apparent， wherein：

Fig. 1 shows a block diagram of a communication environment in which implementations of the present disclosure can be implemented；

Fig. 2 shows a flowchart illustrating a process for CSR according to some implementations of the present disclosure；

Fig. 3 shows a flowchart of an example method in accordance with some implementations of the present disclosure；

Fig. 4 shows a flowchart of an example method in accordance with some other implementations of the present disclosure； and

Fig. 5 is a simplified block diagram of a device that is suitable for implementing implementations of the present disclosure.

Throughout the drawings， the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure， without suggesting any limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims， unless defined otherwise， all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein， the term “network device” or “base station” (BS) refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include， but not limited to， a Node B (NodeB or NB) ， an Evolved NodeB (eNodeB or eNB) ， a next generation NodeB (gNB) a Remote Radio Unit (RRU) ， a radio head (RH) ， a remote radio head (RRH) ， a low power node such as a femto node， a pico node， and the like. For the purpose of discussion， in the following， some embodiments will be described with reference to gNB as examples of the network device.

As used herein， the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include， but not limited to， user equipment (UE) ， personal computers， desktops， mobile phones， cellular phones， smart phones， personal digital assistants (PDAs) ， portable computers， image capture devices such as digital cameras， gaming devices， music storage and playback appliances， or Internet appliances enabling wireless or wired Internet access and browsing and the like. For the purpose of discussion， in the following， some embodiments will be described with reference to UE as examples of the terminal device.

As used herein， the singular forms “a” ， “an” and “the” are intended to include the plural forms as well， unless the context clearly indicates otherwise. The term “includes” and its variants are to be read as open terms that mean “includes， but is not limited to. ” The term “based on” is to be read as “at least in part based on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first， ” “second， ” and the like may refer to different or same objects. Other definitions， explicit and implicit， may be included below.

In some examples， values， procedures， or apparatus are referred to as “best， ” “lowest， ” “highest，” “minimum， ” “maximum， ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made， and such selections need not be better， smaller， higher， or otherwise preferable to other selections.

Communication discussed in the present disclosure may conform to any suitable standards including， but not limited to， New Radio Access (NR) ， Long Term Evolution (LTE) ， LTE-Evolution， LTE-Advanced (LTE-A) ， Wideband Code Division Multiple Access (WCDMA) ， Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM) and the like. Furthermore， the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include， but not limited to， the first generation (1G) ， the second generation (2G) ， 2.5G， 2.75G， the third generation (3G) ， the fourth generation (4G) ， 4.5G， the fifth generation (5G) communication protocols.

Fig. 1 shows an example communication network 100 in which implementations of the present disclosure can be implemented. The network 100 includes a network device 110 and a terminal device 120 served by the network device 110. The serving area of the network device 110 is called as a cell 102. It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of network devices and terminal devices adapted for implementing implementations of the present disclosure. Although not shown， it would be appreciated that one or more terminal devices may be located in the cell 102 and served by the network device 110.

In the communication network 100， the network device 110 can communicate data and control information to the terminal device 120 and the terminal device 120 can also communication data and control information to the network device 110. A link from the network device 110 to the terminal device 120 is referred to as a downlink (DL) ， while a link from the terminal device 120 to the network device 110 is referred to as an uplink (UL) .

The communications in the network 100 may conform to any suitable standards including， but not limited to， Global System for Mobile Communications (GSM) ， Long Term Evolution (LTE) ， LTE-Evolution， LTE-Advanced (LTE-A) ， Wideband Code Division Multiple Access (WCDMA) ， Code Division Multiple Access (CDMA) ， GSM EDGE Radio Access Network (GERAN) ， and the like. Furthermore， the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include， but not limited to， the first generation (1G) ， the second generation (2G) ， 2.5G， 2.75G， the third generation (3G) ， the fourth generation (4G) ， 4.5G， the fifth generation (5G) communication protocols.

In order to obtain CSI of a communication channel between the network device 110 and the terminal device 120， the network device 110 may transmit a channel state information-reference signal (CSI-RS) to the terminal device 120. The terminal device 120 may receive the CSI-RS from the network device 110， and obtain channel information by measuring the CSI-RS. The terminal device 120 may then determine the CSI of the communication channel based on the obtained channel information and a corresponding codebook. For example， the obtained channel information can be quantized into the CSI based on the corresponding codebook. The terminal device 120 may report the CSI to the network device 110. The process for reporting the CSI is also called as “CSI feedback” . The CSI may ensure reliability of the wireless communication between the network device 110 and the terminal device 120.

The accuracy of CSI may have a significant influence on system performance. In this case， two types of codebook (called as “type I codebook” and “type II codebook” ) have been designed for different accuracies of CSI. For example， LC codebook is widely accepted as a category of the type II codebook. In order to obtain high-accuracy CSI， LC codebook can be used for quantizing the obtained channel information.

The quantization based on the LC codebook may be divided into quantization of phase combining coefficients and amplitude scaling coefficients separately. The separate quantization of the phase combining coefficients and amplitude scaling coefficients may result in huge overhead for CSI feedback. For example， the phase combining coefficients and amplitude scaling coefficients of sub-band (SB) level may occupy most of payloads for CSI feedback.

In this event， in order to reducing the CSI feedback overhead for LC codebook and solve one or more of other problems， a solution for codebook subset restriction (CSR) is proposed. With the proposed solution， the CSI feedback overhead for LC codebook can be reduced.

Specifically， although the phase combining coefficients and amplitude scaling coefficients of SB level occupy most of payloads for CSI feedback， their size may depend on the number of non-zero WB amplitude scaling coefficients as well as rank indication (RI) . For example， if a WB amplitude scaling coefficient for a layer is determined to be zero， a respective SB phase combining coefficient and/or even a respective SB differential amplitude scaling coefficient for the layer may be not needed to be reported， and thus the payload thereof can be saved.

Typically， a WB amplitude quantization set may be used by the terminal device 120 to quantize a WB amplitude scaling coefficient into CSI. The number of non-zero power levels included in the WB amplitude quantization set may decide the probability for a WB amplitude scaling coefficient being quantized into zero. With the proposed solution， a subset of a full WB amplitude quantization set including a reduced number of non-zero power levels can be indicated to the terminal device 120 for CSI feedback. In this way， the probability for a WB amplitude scaling coefficient being quantized into zero can be increased， and thus the average payload size for CSI feedback can be reduced.

Principle and implementations of the present disclosure will be described in detail below with reference to Fig. 2， which shows a process 200 for CSR according to an implementation of the present disclosure. For the purpose of discussion， the process 200 will be described with reference to Fig. 1. The process 200 may involve the network device 110 and the terminal device 120 in Fig. 1.

Based on a predefined WB amplitude quantization set (also referred to as “first WB amplitude quantization set” ) ， the network device 110 determines 210 a WB amplitude quantization set (also referred to as “second WB amplitude quantization set” ) to be used for the terminal device 120.

In some embodiments， the first WB amplitude quantization set may be predefined and/or preconfigured for both of the network device 110 and the terminal device 120. The first WB amplitude quantization set may include a first number of power levels corresponding to first quantification accuracy for quantizing a WB amplitude scaling coefficient into CSI. The first number of power levels may be indexed with respective values， and thus the WB amplitude scaling coefficient may be quantized into one of the respective values.

In one embodiment， if the first WB amplitude quantization set has 3-bit quantification accuracy， it may include 8 power levels， such as

The 8 power levels may correspond to 3-bit quantification accuracy. That is， a WB amplitude scaling coefficient can be quantized into a 3-bit value based on the first WB amplitude quantization set. Each of the 8 power levels may be associated with a respective 3-bit index. For example， the 1st power level “1” may be associated with an index of ‘000’ ； the 2nd power level

may be associated with an index of ‘001’ ； ... and the last power level “0” may be associated with an index of “111” . It is to be understood that the above example is only for the purpose of illustration without suggesting any limitations to the scope of the subject matter described herein. In some other embodiments， the 8 power levels may be indexed in a different way. As such， a power level may be indexed with one of the 8 indexes. For example， a power level

may be indexed with ‘100’ .

In some embodiments， the network device 110 may determine the second WB amplitude quantization set by removing at least one non-zero power level from the first WB amplitude quantization set. That is， the second WB amplitude quantization set may be a subset of the first WB amplitude quantization set. Specifically， the network device 110 may determine the second WB amplitude quantization set by removing a relatively low power level from the first WB amplitude quantization set.

Continuing with the above example， the network device 110 may remove

from the first WB amplitude quantization set. Therefore， the determined second WB amplitude quantization set may include 7 power levels， which are

The 7 power levels may correspond to 3-bit quantification accuracy. That is， a WB amplitude scaling coefficient can be quantized into a 3-bit value based on the second WB amplitude quantization set. In some embodiments， the power levels “1” and “0” may be always included in the second WB amplitude quantization set， which correspond to the maximum and minimum power levels respectively.

In some embodiments， the network device 110 may determine the second WB amplitude quantization set， such that the quantification accuracy can be reduced. For example， if four non-zero power levels

are removed from the first WB amplitude quantization set， the second WB amplitude quantization set may be determined to be

The 4 power levels may correspond to 2-bit quantification accuracy. That is， a WB amplitude scaling coefficient can be quantized into a 2-bit value based on the second WB amplitude quantization set.

In some embodiments， a same power level may be included in both the first and second WB amplitude quantization sets， and the same power level may be indexed in the first and second WB amplitude quantization sets with a same value. Suppose that the first WB amplitude quantization set is

and the second WB amplitude quantization set is

For example， a power level

may be indexed with ‘100’ in both of the first and second WB amplitude quantization sets， since the power level

is the 5^th element in first WB amplitude quantization set. That is， the power level

may be indexed in the first and second WB amplitude quantization sets with a same value.

Alternatively， in some other embodiments， the same power level included in both the first and second WB amplitude quantization sets may be indexed in the first and second WB amplitude quantization sets with different values respectively. Continuing with the above example， the power level

may be indexed in the second WB amplitude quantization set with ‘011’ instead of ‘100’ ， since the power level

is the 4^th element in second WB amplitude quantization set. That is， the power level

may be indexed in the first and second WB amplitude quantization sets with different values respectively.

The network device 110 transmits 220 an indication of the second WB amplitude quantization set to the terminal device 120. In some embodiments， the indication of the second WB amplitude quantization set may be transmitted to the terminal device 120 via higher layer signaling. Examples of the high level signaling may include but not limited to signaling on Radio Resource Control (RRC) Layer.

In some embodiments， the network device 110 may transmit a bitmap indicating the second WB amplitude quantization set to the terminal device 120. The bitmap may indicate to the terminal device 120 which power level is removed from the first WB amplitude quantization set.

In one embodiment， the number of bits in the bitmap may equal to the number of power levels included in the first WB amplitude quantization set. A bit of ‘0’ in the bitmap may indicate the corresponding power level is removed， while a bit of ‘1’ in the bitmap may indicate the corresponding power level is retained. For example， if the first WB amplitude quantization set is

and the power level

is removed from the first WB amplitude quantization set， a bitmap ‘11111101’ may be indicated to the terminal device 120.

In another embodiment， the number of bits included in the bitmap may be less than the number of power levels included in the first WB amplitude quantization set. For example， the terminal device 120 may configured with that the power level “1” and “0” may be always included in the second WB amplitude quantization set. In this event， 2 bits corresponding to the power levels “1” and “0” can be saved. For example， if the first WB amplitude quantization set is

and the power level

is removed from the first WB amplitude quantization set， a bitmap ‘111110’ may be indicated to the terminal device 120.

In some embodiment， the first WB amplitude quantization set may be preconfigured for the terminal device 120. In this case， the terminal device 120 may obtain the second WB amplitude quantization set from the first WB amplitude quantization set and the bitmap.

In some embodiments， the second number of power levels may be indexed with respective values， and the network device 110 may also transmit information on the respective values for the second number of power levels via higher layer signaling to the terminal device 120. For example， as described above， a same power level may be included in both the first and second WB amplitude quantization sets. In some embodiments， the information on the respective values for the second number of power levels may indicate that the same power level may be indexed in the first and second WB amplitude quantization sets with a same value. Alternatively， in some other embodiments， the information on the respective values for the second number of power levels may indicate that the power level may be indexed in the first and second WB amplitude quantization sets with different values respectively. As such， the terminal device 120 can be aware of how to report the CSI accordingly.

If the indication of the second WB amplitude quantization set is received， the terminal device 120 determines 230 the CSI at least based on the second WB amplitude quantization set.

For example， the network device 110 may transmit CSI-RS to the terminal device 120. Once the terminal device 120 receives the CSI-RS from the network device 110， it may obtain channel information by measuring the CSI-RS. The terminal device 120 may then determine the CSI of the communication channel based on the obtained channel information and a LC codebook. For example， a WB amplitude scaling coefficient obtained by the terminal device 120 may be quantized into a respective value based on the second WB amplitude quantization set. The respective value may be included in the CSI. Since the number of non-zero power levels in the second WB amplitude quantization set is less than the number of non-zero power levels in the first WB amplitude quantization set， the probability for a WB amplitude scaling coefficient being quantized into zero can be increased.

Then， the terminal device 120 transmits 240 the CSI to the network device 110.

Through the above depiction， it can be seen that with the proposed solution， a subset of a full WB amplitude quantization set including a reduced number of non-zero power levels can be indicated to the terminal device 120 for CSI feedback. In this way， the probability for a WB amplitude scaling coefficient being quantized into zero can be increased， and thus the payload size for CSI feedback can be reduced.

Fig. 3 shows a flowchart of an example method 300 in accordance with some implementations of the present disclosure. The method 300 can be implemented at the network device 110 as shown in Fig. 1. For the purpose of discussion， the method 300 will be described from the perspective of the network device 110 with reference to Fig. 1.

At block 310， the network device 110 determines， based on a first wideband (WB) amplitude quantization set including a first number of power levels， a second WB amplitude quantization set including a second number of power levels. The second number is less than the first number. At block 320， the network device 110 transmits， to the terminal device 120 an indication of the second WB amplitude quantization set. At block 330， the network device 110 receives CSI from the terminal device 120. The CSI is determined by the terminal device 120 at least based on the second WB amplitude quantization set.

In some implementations， the network device 110 may determining the second WB amplitude quantization set by removing at least one non-zero power level from the first WB amplitude quantization set.

In some implementations， the network device 110 may transmit the indication of the second WB amplitude quantization set by transmitting a bitmap indicating the second WB amplitude quantization set via higher layer signaling to the terminal device 120.

In some implementations， the second number of power levels are indexed with respective values and the CSI is determined by the terminal device 120 at least based on the respective values for the second number of power levels. The network device 110 may transmit the indication of the second WB amplitude quantization set by transmitting information on the respective values for the second number of power levels via higher layer signaling to the terminal device.

In some implementations， a first power level is included in both the first and second WB amplitude quantization sets. The first power level is indexed in the first and second WB amplitude quantization sets with a same value.

In some implementations， a second power level is included in both the first and second WB amplitude quantization sets. The second power level is indexed in the first WB amplitude quantization set with a first value and indexed in the second WB amplitude quantization set with a second value. The first value is different from the second value.

Fig. 4 shows a flowchart of an example method 400 in accordance with some implementations of the present disclosure. The method 400 can be implemented at the terminal device 120 as shown in Fig. 1. For the purpose of discussion， the method 400 will be described from the perspective of the terminal device 120 with reference to Fig. 1.

At block 410， the terminal device 120 receives， from the network device 110， an indication of a second wideband (WB) amplitude quantization set including a second number of power levels. The second WB amplitude quantization set is determined by the network device 110 based on a first WB amplitude quantization set including a first number of power levels. The second number is less than the first number. At block 420， the terminal device 120 determines channel state information (CSI) at least based on the second WB amplitude quantization set. At block 430， the terminal device 120 transmits the CSI to the network device 110.

In some implementations， the second WB amplitude quantization set is determined by removing at least one non-zero power level from the first WB amplitude quantization set by the network device 110.

In some implementations， the terminal device 120 may receive the indication of the second WB amplitude quantization set by receiving， from the network device 110， a bitmap indicating the second WB amplitude quantization set via higher layer signaling.

In some implementations， the second number of power levels are indexed with respective values. The terminal device 120 may receive the indication of the second WB amplitude quantization set by receiving， from the network device 110， information on the respective values for the second number of power levels via higher layer signaling. The terminal device 120 may determine the CSI based on the respective values for the second number of power levels.

It is to be understood that all operations and features related to the network device 110 described above with reference to Fig. 2 are likewise applicable to the method 300 and have similar effects. All operations and features related to the terminal device 120 described above with reference to Fig. 2 are likewise applicable to the method 400 and have similar effects. For the purpose of simplification， the details will be omitted.

Fig. 5 is a simplified block diagram of a device 500 that is suitable for implementing embodiments of the present disclosure. The device 500 can be considered as a further example implementation of a network device 110 or a terminal device 120 as shown in Fig. 1. Accordingly， the device 500 can be implemented at or as at least a part of the network device 110 or the terminal device 120.

As shown， the device 500 includes a processor 510， a memory 520 coupled to the processor 510， a suitable transmitter (TX) and receiver (RX) 540 coupled to the processor 510， and a communication interface coupled to the TX/RX 540. The memory 520 stores at least a part of a program 530. The TX/RX 540 is for bidirectional communications. The TX/RX 540 has at least one antenna to facilitate communication， though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements， such as X2 interface for bidirectional communications between eNBs， S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB， Un interface for communication between the eNB and a relay node (RN) ， or Uu interface for communication between the eNB and a terminal device.

The program 530 is assumed to include program instructions that， when executed by the associated processor 510， enable the device 500 to operate in accordance with the implementations of the present disclosure， as discussed herein with reference to Figs. 2 to 4. The implementations herein may be implemented by computer software executable by the processor 510 of the device 500， or by hardware， or by a combination of software and hardware. The processor 510 may be configured to implement various implementations of the present disclosure. Furthermore， a combination of the processor 510 and memory 520 may form processing means 550 adapted to implement various implementations of the present disclosure.

The memory 520 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology， such as a non-transitory computer readable storage medium， semiconductor based memory devices， magnetic memory devices and systems， optical memory devices and systems， fixed memory and removable memory， as non-limiting examples. While only one memory 520 is shown in the device 500， there may be several physically distinct memory modules in the device 500. The processor 510 may be of any type suitable to the local technical network， and may include one or more of general purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) and processors based on multicore processor architecture， as non-limiting examples. The device 500 may have multiple processors， such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The components included in the apparatuses and/or devices of the present disclosure may be implemented in various manners， including software， hardware， firmware， or any combination thereof. In one implementation， one or more units may be implemented using software and/or firmware， for example， machine-executable instructions stored on the storage medium. In addition to or instead of machine-executable instructions， parts or all of the units in the apparatuses and/or devices may be implemented， at least in part， by one or more hardware logic components. For example， and without limitation， illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs) ， Application-specific Integrated Circuits (ASICs) ， Application-specific Standard Products (ASSPs) ， System-on-a-chip systems (SOCs) ， Complex Programmable Logic Devices (CPLDs) ， and the like.

Generally， various implementations of the present disclosure may be implemented in hardware or special purpose circuits， software， logic or any combination thereof. Some aspects may be implemented in hardware， while other aspects may be implemented in firmware or software which may be executed by a controller， microprocessor or other computing device. While various aspects of implementations of the present disclosure are illustrated and described as block diagrams， flowcharts， or using some other pictorial representation， it will be appreciated that the blocks， apparatus， systems， techniques or methods described herein may be implemented in， as non-limiting examples， hardware， software， firmware， special purpose circuits or logic， general purpose hardware or controller or other computing devices， or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions， such as those included in program modules， being executed in a device on a target real or virtual processor， to carry out the process or method as described above with reference to any of Figs. 2， 6， and 7. Generally， program modules include routines， programs， libraries， objects， classes， components， data structures， or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various implementations. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device， program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer， special purpose computer， or other programmable data processing apparatus， such that the program codes， when executed by the processor or controller， cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine， partly on the machine， as a stand-alone software package， partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium， which may be any tangible medium that may contain， or store a program for use by or in connection with an instruction execution system， apparatus， or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic， magnetic， optical， electromagnetic， infrared， or semiconductor system， apparatus， or device， or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires， a portable computer diskette， a hard disk， a random access memory (RAM) ， a read-only memory (ROM) ， an erasable programmable read-only memory (EPROM or Flash memory) ， an optical fiber， a portable compact disc read-only memory (CD-ROM) ， an optical storage device， a magnetic storage device， or any suitable combination of the foregoing.

Further， while operations are depicted in a particular order， this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order， or that all illustrated operations be performed， to achieve desirable results. In certain circumstances， multitasking and parallel processing may be advantageous. Likewise， while several specific implementation details are contained in the above discussions， these should not be construed as limitations on the scope of the present disclosure， but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in the context of separate implementations may also be implemented in combination in a single implementation. Conversely， various features that are described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts， it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather， the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A method implemented in a network device， comprising：

determining， based on a first wideband (WB) amplitude quantization set including a first number of power levels， a second WB amplitude quantization set including a second number of power levels， the second number being less than the first number；

transmitting， to a terminal device served by the network device， an indication of the second WB amplitude quantization set； and

receiving channel state information (CSI) from the terminal device， the CSI being determined by the terminal device at least based on the second WB amplitude quantization set.
The method of Claim 1， wherein determining the second WB amplitude quantization set comprises：

determining the second WB amplitude quantization set by removing at least one non-zero power level from the first WB amplitude quantization set.
The method of Claim 1， wherein transmitting the indication of the second WB amplitude quantization set comprises：

transmitting a bitmap indicating the second WB amplitude quantization set via higher layer signaling to the terminal device.
The method of Claim 1， wherein the second number of power levels are indexed with respective values， the CSI being determined by the terminal device at least based on the respective values for the second number of power levels， and transmitting the indication of the second WB amplitude quantization set comprises：

transmitting information on the respective values for the second number of power levels via higher layer signaling to the terminal device.
The method of Claim 4， wherein a first power level is included in both the first and second WB amplitude quantization sets， the first power level being indexed in the first and second WB amplitude quantization sets with a same value.
The method of Claim 4， wherein a second power level is included in both the first and second WB amplitude quantization sets， the second power level being indexed in the first WB amplitude quantization set with a first value and being indexed in the second WB amplitude quantization set with a second value， and the first value is different from the second value.
A method implemented in a terminal device， comprising：

receiving， from a network device serving the terminal device， an indication of a second wideband (WB) amplitude quantization set including a second number of power levels， the second WB amplitude quantization set being determined by the network device based on a first WB amplitude quantization set including a first number of power levels， the second number being less than the first number；

determining channel state information (CSI) at least based on the second WB amplitude quantization set； and

transmitting the CSI to the network device.
The method of Claim 7， wherein the second WB amplitude quantization set is determined by removing at least one non-zero power level from the first WB amplitude quantization set by the network device.
The method of Claim 7， wherein receiving the indication of the second WB amplitude quantization set comprises：

receiving， from the network device， a bitmap indicating the second WB amplitude quantization set via higher layer signaling.
The method of Claim 7， wherein the second number of power levels are indexed with respective values，

receiving the indication of the second WB amplitude quantization set comprises：

receiving， from the network device， information on the respective values for the second number of power levels via higher layer signaling； and

determining the CSI comprises：

determining the CSI at least based on the respective values for the second number of power levels.
The method of Claim 10， wherein a first power level is included in both the first and second WB amplitude quantization sets， the first power level being indexed in the first and second WB amplitude quantization sets with a same value.
The method of Claim 10， wherein a second power level is included in both the first and second WB amplitude quantization sets， the second power level being indexed in the first WB amplitude quantization set with a first value and being indexed in the second WB amplitude quantization set with a second value， and the first value is different from the second value.
A network device， comprising：

a processor； and

a memory coupled to the processor and storing instructions thereon， the instructions， when executed by the processor， causing the network device to perform actions， the actions comprising：

determining， based on a first wideband (WB) amplitude quantization set including a first number of power levels， a second WB amplitude quantization set including a second number of power levels， the second number being less than the first number；

transmitting， to a terminal device served by the network device， an indication of the second WB amplitude quantization set； and

receiving channel state information (CSI) from the terminal device， the CSI being determined by the terminal device at least based on the second WB amplitude quantization set.
The network device of Claim 13， wherein determining the second WB amplitude quantization set comprises：

determining the second WB amplitude quantization set by removing at least one non-zero power level from the first WB amplitude quantization set.
The network device of Claim 13， wherein transmitting the indication of the second WB amplitude quantization set comprises：

transmitting a bitmap indicating the second WB amplitude quantization set via higher layer signaling to the terminal device.
The network device of Claim 13， wherein the second number of power levels are indexed with respective values， the CSI being determined by the terminal device at least based on the respective values for the second number of power levels， and transmitting the indication of the second WB amplitude quantization set comprises：

transmitting information on the respective values for the second number of power levels via higher layer signaling to the terminal device.
The network device of Claim 16， wherein a first power level is included in both the first and second WB amplitude quantization sets， the first power level being indexed in the first and second WB amplitude quantization sets with a same value.
The network device of Claim 16， wherein a second power level is included in both the first and second WB amplitude quantization sets， the second power level being indexed in the first WB amplitude quantization set with a first value and being indexed in the second WB amplitude quantization set with a second value， and the first value is different from the second value.
A terminal device， comprising：

a processor； and

a memory coupled to the processor and storing instructions thereon， the instructions， when executed by the processor， causing the terminal device to perform actions， the actions comprising：

receiving， from a network device serving the terminal device， an indication of a second wideband (WB) amplitude quantization set including a second number of power levels， the second WB amplitude quantization set being determined by the network device based on a first WB amplitude quantization set including a first number of power levels， the second number being less than the first number；

determining channel state information (CSI) at least based on the second WB amplitude quantization set； and

transmitting the CSI to the network device.
The terminal device of Claim 19， wherein the second WB amplitude quantization set is determined by removing at least one non-zero power level from the first WB amplitude quantization set by the network device.
The terminal device of Claim 19， wherein receiving the indication of the second WB amplitude quantization set comprises：

receiving， from the network device， a bitmap indicating the second WB amplitude quantization set via higher layer signaling.
The terminal device of Claim 19， wherein the second number of power levels are indexed with respective values，

receiving the indication of the second WB amplitude quantization set comprises：

receiving， from the network device， information on the respective values for the second number of power levels via higher layer signaling； and

determining the CSI comprises：

determining the CSI at least based on the respective values for the second number of power levels.
The terminal device of Claim 19， wherein a first power level is included in both the first and second WB amplitude quantization sets， the first power level being indexed in the first and second WB amplitude quantization sets with a same value.
The terminal device of Claim 19， wherein a second power level is included in both the first and second WB amplitude quantization sets， the second power level being indexed in the first WB amplitude quantization set with a first value and being indexed in the second WB amplitude quantization set with a second value， and the first value is different from the second value.
A computer readable medium having instructions stored thereon， the instructions， when executed on at least one processor， causing the at least one processor to carry out the method according to any of claims 1 to 6.
A computer readable medium having instructions stored thereon， the instructions， when executed on at least one processor， causing the at least one processor to carry out the method according to any of claims 7 to 12.