WO2019034121A1

WO2019034121A1 - Method, device and computer readable medium for mimo communication

Info

Publication number: WO2019034121A1
Application number: PCT/CN2018/100886
Authority: WO
Inventors: Hao Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2017-08-16
Filing date: 2018-08-16
Publication date: 2019-02-21

Abstract

Embodiments of the present disclosure provide methods, devices and computer readable media for MIMO communication. The method described herein comprises determining, at the terminal device, a number of nonzero elements in a set of wideband amplitude parameters. The set is associated with a beam set for the MIMO communication. The method further comprises transmitting, to a network device, the number and rank information related to the MIMO communication as a first portion of CSI between the terminal device and the network device. The method further comprises transmitting, to the network device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and the network device as a second portion of the CSI.

Description

METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR MIMO COMMUNICATION

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priorities to Chinese Patent Application No. 201710702390.0 filed on August 16, 2017 and Chinese Patent Application No. 201710786740.6 filed on September 4, 2017, which are incorporated herein by reference in their entirety.

FIELD

Embodiments of the present disclosure relate to the field of communications, and in particular, to methods, devices and computer readable media for performing Channel State Information (CSI) feedback in Multiple-Input Multiple-Ouput (MIMO) communication.

BACKGROUND

The MIMO technique has the capability to significantly improve the performance of a fifth-generation (5G) radio communication system. In the multi-user MIMO, since a transmitter performs linear precoding, full multiplexing gain and significant throughput improvement are achieved. Therefore, the multi-user MIMO becomes a key technique to meet ever-increasing performance requirements for 5G MIMO communication. The accuracy of the CSI has significant influence on MU-MIMO scheduling performance for a MIMO system utilizing Frequency Division Duplexing (FDD) configuration. The adaptability of codebook design and its granularity become the great challenges and bottlenecks for MU-MIMO application in 5G radio communication system.

SUMMARY

Generally, embodiments of the present disclosure provide methods, devices and computer readable media for performing CSI feedback in MIMO communication.

In a first aspect, embodiments of the present disclosure provide a method of MIMO communication implemented at terminal device. The method comprises determining, at the terminal device, a number of nonzero elements in a set of wideband amplitude parameters. The set of wideband amplitude parameters is associated with a beam set for the MIMO communication. The method further comprises transmitting, to a network device, the number and rank information related to the MIMO communication as a first portion of CSI between the terminal device and the network device. The method further comprises transmitting, to the network device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and network device as a second portion of the CSI.

In some embodiments, transmitting the first portion of the CSI comprises transmitting the first portion in a first time slot; and transmitting the second portion of the CSI comprises transmitting the second portion in the first time slot.

In some embodiments, the first portion and second portion are transmitted on a physical uplink shared channel between the terminal device and the network device.

In some embodiments, transmitting the first portion of the CSI comprises transmitting the first portion in a second time slot; and transmitting the second portion of the CSI comprises transmitting the second portion in a third time slot, the second time slot being prior to the third time slot.

In some embodiments, transmitting the first portion in the second time slot comprises transmitting the first portion on a physical uplink control channel between the terminal device and network device or on a physical uplink shared channel between the terminal device and the network device; and transmitting the second portion in the third time slot comprises transmitting the second portion on the physical uplink control channel or on the physical uplink shared channel between the terminal device and the network device.

In some embodiments, the method further comprises: receiving, from the network device and at least via a high-layer signaling, information on resource allocation for the first portion; and determining a resource on the physical uplink control channel for transmitting the second portion, based on mapping between a payload size of the second portion and available resources on the physical uplink control channel.

In some embodiments, transmitting the first portion of the CSI comprises transmitting the first portion in a first period; and transmitting the second portion of the CSI comprises transmitting the second portion in a second period, the second period being equal to or shorter than the first period.

In some embodiments, the set of wideband amplitude parameters includes at least a first subset of wideband amplitude parameters associated with a first transmission layer between the terminal device and network device; and transmitting the number of nonzero elements in the set of wideband amplitude parameters comprises transmitting the first number of nonzero wideband amplitude parameters in the first subset.

In some embodiments, transmitting the information related to the precoding matrix comprises: comparing the first number with the number of beams in the beam set; in response to the first number being smaller than or equal to the number of beams, transmitting separately-quantized indices of the nonzero wideband amplitude parameters in the first subset; and in response to the first number exceeding the number of beams, transmitting separately-quantized indices of zero wideband amplitude parameters in the first subset.

In some embodiments, transmitting the information related to the precoding matrix comprises: obtaining jointly-quantized indices of the wideband amplitude parameters by jointly quantizing indices of the nonzero wideband amplitude parameters in the first subset; and transmitting the jointly-quantized indices of the nonzero wideband amplitude parameters in the first subset.

In some embodiments, transmitting the information related to the precoding matrix comprises: determining, based on the first number, a relative index of a peak of the nonzero wideband amplitude parameters in the first subset; quantizing nonzero amplitude parameters other than the peak in the first subset to obtain quantized nonzero wideband amplitude parameters; and transmitting the relative index of the peak and the quantized nonzero wideband amplitude parameters.

In some embodiments, the set of wideband amplitude parameters further comprises a second subset of wideband amplitude parameters associated with a second transmission layer between the terminal device and network device; and transmitting the number of nonzero elements in the set of wideband amplitude parameters further comprises transmitting a second number of nonzero wideband amplitude parameters in the second subset.

In some embodiments, a payload size of the second portion of the CSI is determined based on the first portion of the CSI.

In a second aspect, embodiments of the present disclosure provide a method of MIMO communication implemented at a network device. The method comprises receiving, from a terminal device, a number of nonzero elements in a set of wideband amplitude parameters and rank information related to the MIMO communication as a first portion of CSI between the terminal device and the network device. The set is associated with a beam set for the MIMO communication. The method further comprises receiving, from the terminal device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and network device as a second portion of the CSI.

In a third aspect, embodiments of the present disclosure further provide a terminal device. The terminal device comprises a controller and a memory coupled to the controller. The memory comprises instructions. The instructions, when executed by the controller, cause the terminal device to execute acts. The acts comprise: determining, at the terminal device, a number of nonzero elements in a set of wideband amplitude parameters. The set of wideband amplitude parameters is associated with a beam set for MIMO communication. The acts further comprise transmitting, to a network device, the number and rank information related to the MIMO communication as a first portion of CSI between the terminal device and the network device. The acts further comprise transmitting, to the network device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and the network device as a second portion of the CSI.

In a fourth aspect, embodiments of the present disclosure further provide a network device. The network device comprises a controller and a memory coupled to the controller. The memory comprises instructions. The instructions, when executed by the controller, cause the network device to execute acts. The acts comprise: receiving from a terminal device, a number of nonzero elements in a set of wideband amplitude parameters and rank information related to MIMO communication as a first portion of CSI between the terminal device and the network device. The set is associated with a beam set for the MIMO communication. The acts further comprise receiving, from the terminal device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and the network device as a second portion of the CSI.

In a fifth aspect, embodiments of the present disclosure provide a computer readable medium, comprising computer executable instructions, the computer executable instructions, when executed on a device, causing the apparatus to perform the method according to the first aspect.

In a sixth aspect, embodiments of the present disclosure provide a computer readable medium, comprising computer executable instructions, the computer executable instructions, when executed on a device, causing the apparatus to perform the method according to the second aspect.

It should be appreciated that the Summary is not intended to indicate essential or important features of embodiments of the present disclosure or to limit the scope of the present disclosure. Other features of the present disclosure will be made apparent through the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed description with reference to the accompanying drawings, the above and other features, advantages and aspects of embodiments of the present disclosure will become more apparent. In the drawings, identical or similar reference numbers represent the same or similar elements, in which:

Fig. 1 illustrates an example communication network in which some embodiments of the present disclosure may be implemented;

Fig. 2 illustrates a flow chart of a method of MIMO communication implemented at a terminal device according to some embodiments of the present disclosure;

Fig. 3 illustrates a flow chart of a method of MIMO communication implemented at a network device according to some embodiments of the present disclosure; and

Fig. 4 illustrates a block diagram of a communication device adapted to implement some embodiments of the present disclosure.

It should be appreciated that the Summary is not intended to indicate essential or important features of embodiments of the present disclosure, and not intended to limit the scope of the present disclosure. Other features of the present disclosure will become apparent through the following descriptions.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail with reference to the drawings. Though some embodiments of the present disclosure are shown in the drawings, it should be appreciated that the present disclosure can be implemented in various manners and should not be interpreted as limited to the embodiments described herein. Rather, these embodiments are provided for thorough and complete understanding of the present disclosure. It is to be understood that the drawings and embodiments are only for the purpose of example, rather than to limit the claim scope of the present disclosure.

The term “network device” used herein refers to other entities or nodes having specific functions in a base station or communication network. The term “base station (BS) ” may represent a node B (NodeB or NB) , an Evolved Node B (eNodeB or eNB) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , a repeater, or a low power node such as a pico node, a femto node and the like. In the context of the present disclosure, the terms “network device” and “base station” may be used interchangeably, and the eNB is generally taken as an example for the network device for the sake of discussion.

The term “terminal device” or “user equipment (UE) ” used herein refers to any terminal device that can perform wireless communications with a base station or with each other. As an example, the terminal device may comprise a mobile terminal (MT) , a subscriber station (SS) , a portable subscriber station (PSS) , a mobile station (MS) or an access terminal (AT) , and the above devices on-board a vehicle. In the context of the present disclosure, the terms “terminal device” and “user equipment” may be used interchangeably for the sake of discussion.

The term “includes” and its variants as used herein are to be read as open-ended terms that mean “includes, but is not limited to. ” The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” is to be read as “at least one embodiment, ” and the term “another embodiment” is to be read as “at least one another embodiment. ” Relevant definition for other terms will be given in the following description.

At present, consensus has already been achieved that the MU-MIMO communication in 5G system employs “advanced CSI” feedback architecture. The “advanced CSI” feedback architecture employs a dual-stage codebook W, which may be represented by the following equation:

W =W ₁W ₂ (1)

where W ₁ represents a first stage of codebook, and W ₂ represents a second stage of codebook.

The first stage of codebook W ₁ comprises a beam set consisting of L orthogonal beams, wherein L orthogonal beams are selected on a wideband and from a predefined beam group for each polarization direction, and L is a natural number larger than 1. The second stage of codebook W ₂ comprises (2L-1) beam combining coefficients for L selected beams in 2 polarization directions for each transmission layer (also called “layer” ) .

Generally, beam combining coefficients comprise a set of amplitude combining coefficients and a set of phase combining coefficients associated with the beam set. A set of phase parameters may be configured to report to the network device with respect to a subband, while a set of amplitude parameters may be configured to report to the network device with respect to the wideband or report to the network device in a differential manner with respect to a subband. A set of amplitude parameters reporting to the network device with respect to the wideband is also called a set ofwideband amplitude parameters.

The two-stage codebook having the above structure has huge feedback overhead due to separate quantization of amplitude combining coefficients and phase combining coefficients for different beams, different polarizations, different layers and different subbands. However, CSI payload size is varied depending on a rank and a number of nonzero elements in the set of amplitude combining coefficients. For example, the CSI payload size when the rank is 1 is nearly half of the CSI payload size when the rank is 2. When a wideband amplitude combining coefficient is quantized to zero for a given layer, its subband phase combining coefficient and subband differential amplitude combining coefficient, if configured, do not need to report for the layer. Thus, feedback payload is significantly reduced, especially when a subband reporting mode is configured.

Conventionally, to support reporting of CSI having a variable payload size, the rank information and the wideband amplitude combining coefficient are jointly encoded and transmitted in a first time slot, and information in CSI other than the rank information and the wideband amplitude combining coefficient is transmitted in a second time slot after the first time slot.

After successfully decoding the rank information and the wideband amplitude combining coefficient in the first time slot, the network device can know the payload size of the information in the second time slot and can perform correct detection of it. However, this will cause an error propagation issue.

To ensure correct decoding of the information in the first time slot, the rank information and the wideband amplitude combining coefficient should be sufficiently encoded and protected. Since the wideband amplitude combining coefficient includes the strongest index out of 2L coefficients per layer and remaining (2L-1) wideband amplitude combining coefficients per layer, the payload size of the wideband amplitude combining coefficient reaches 48 bits when the rank is 2. Therefore, the wideband amplitude combining coefficient in the first time slot should consume too much resources to achieve over protection of large payload size, which in turn reduces uplink control channel coverage in the first time slot. Therefore, an effective manner is needed to reduce the payload size in the first time slot.

To at least partially solve these and other potential problems, embodiments of the present disclosure provide a solution for MIMO communication. According to embodiments described herein, the terminal device transmits, to the network device, rank information and a number of nonzero elements in the set of wideband amplitude parameters as a first portion of CSI, and transmits information related to a precoding matrix and channel quality indication information to the network device as a second portion of the CSI. Since the first portion of the CSI only includes the rank information and the number of nonzero elements in the set of wideband amplitude parameters, the payload of the first portion is small, so that it is possible to use low-rate encoding to acquire satisfactory protection for the first portion without consuming too much resources, which in turn reduces the probability of error propagation from the first portion to the second portion.

Fig. 1 illustrates an example wireless communication system 100 in which some embodiments of the present disclosure may be implemented. The wireless communication system 100 comprises a network device 110 and a terminal device 120. It should be appreciated that the number of network device and the number of terminal device as shown in Fig. 1 are only for illustration purpose and not intended for limitation. The wireless communication system 100 may include any suitable types and number of network devices. Each network device may provide any suitable number of cells, and the wireless communication system 100 may further include any suitable number of terminal devices.

Communication between the network device 110 and terminal device 120 may be implemented according to any suitable communication protocol, including but not limited to the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) , the fifth generation (5G) and other cellular communication protocol, wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and/or any other protocols that are currently known or to be developed later. Furthermore, the communication utilizes any appropriate wireless communication technology, including but not limited to, code division multiple access (CDMA) , frequency division multiple access (FDMA) , time division multiple access (TDMA) , frequency division duplexing (FDD) , time division duplexing (TDD) , multiple input multiple output (MIMO) , orthogonal frequency division multiplexing (OFDM) , and/or any other technology that is currently known or to be developed in future. It should be appreciated that although embodiments of the present disclosure is mainly described using a Long Term Evolution (LTE) system as an example, this is only exemplary, and the technical solution of the present disclosure may completely applied to other suitable existing systems or systems to-be-developed.

In MIMO communication, the terminal device 120 transmits CSI to the network device 110 so that the network device 110, based on the CSI, configures a precoding matrix for precoding downlink data. According to an embodiment of the present disclosure, the terminal device 120 transmits, to the network device 110, rank information and a number of nonzero elements in the set of wideband amplitude parameters as a first portion of the CSI, and transmits, to the network device 110, information related to the precoding matrix and channel quality indication information as a second portion of the CSI.

Reference is made to Figs. 2 and 4 to illustrate the principle and specific embodiments of the present disclosure from the network device 110 and the terminal device 120 respectively. First, reference is made to Fig. 2 which illustrates a flow chart of a method 200 of MIMO communication according to some embodiments of the present disclosure. It may be appreciated that the method 200 may be for example implemented at the terminal device 120 as shown in Fig. 1. For ease of description, the method 200 will be described below with reference to Fig. 1.

As shown in Fig. 1, at block 210, the terminal device 120 determines a number of nonzero elements in the set of wideband amplitude parameters, which is associated with a beam set for the MIMO communication. In the context of the present disclosure, the wideband amplitude parameters are also referred to as amplitude combining coefficients.

At block 220, the terminal device 120 transmits, to the network device 110, the number of nonzero elements in the set of wideband amplitude parameters and rank information related to the MIMO communication as the first portion of the CSI between the terminal device 120 and the network device 110.

In some embodiments, the rank information related to the MIMO communication may indicate a value of a rank for MIMO communication. The value of the rank may be any natural number. Typically, the value of the rank may be 1 or 2. Therefore, the first portion of the CSI may include one bit to bear the rank information. It may be appreciated that the value of the rank, the number of transmission layers and the number of layers between the terminal device 120 and network device 110 are the same.

In some embodiments, the set of wideband amplitude parameters may comprise one or more subsets, each subset being associated with one layer. The number of subsets is the same as the number of layers between the terminal device 120 and network device 110. For example, if the value of the rank is 1, the number of layers between the terminal device 120 and network device 110 is also 1. Then, the set of wideband amplitude parameters only includes a first subset of wideband amplitude parameters associated with a single layer (also called “a first layer” ) . If the value of the rank is 2, the number of layers between the terminal device 120 and network device 110 is also 2. Then, the set of wideband amplitude parameters includes the first subset of wideband amplitude parameters associated with the first layer and a second subset of wideband amplitude parameters associated with a second layer.

The first portion of the CSI may reserve a space according to a maximum allowed number of the layer to receive the number of nonzero elements in the subset of wideband amplitude parameters associated with the corresponding layer. In an embodiment in which the value of the rank is 1, the terminal device 120 includes, in the first portion of the CSI, the number of nonzero elements in the first subset, and includes a predetermined value (i.e., a value known by the network device 110 in advance) in other portions of the reserved space. Upon receiving the first portion of the CSI, the network device 110 may, based on the value (namely, 1) of the rank, determines that the number of nonzero elements associated with the first layer in the reserved space is useful, whereas the content in other portions of the reserved space is useless, thereby neglecting the content. In an embodiment in which the value of the rank is 2, the terminal device 120 includes, in the first portion of the CSI, the respective number of nonzero elements in the first subset and second subset. Upon receiving the first portion of the CSI, the network device 110 may, based the value of the rank (namely, 2) , determine that the number of nonzero elements in the reserved space respectively associated with the two layers is useful.

Reference is made to the following example, in which the beam set for the MIMO communication includes L orthogonal beams, and L is a natural number larger than 1. If the value of the rank is 1, the first subset of wideband amplitude parameters includes 2L elements. If the value of the rank is 2, the first subset and second subset of wideband amplitude parameters respectively include 2L elements. The respective number of nonzero elements in the first subset and second subset may be in a range of 1 to 2L, and the respective nonzero elements of the first subset and second subset may be respectively quantized as

bits, wherein

represents upward rounding. Hence, the terminal device 120 may use

bits in the first portion of the CSI to indicate respective nonzero elements in the first subset and second subset. It should be appreciated that in the case where the value of the rank is 1,

bits in

for indicating the number of nonzero elements in the second subset bits become useless, and thereby may be neglected by the network device 110.

For example, when L=2, the terminal device 120 may employ 4 bits in the first portion of the CSI to indicate the respective nonzero elements in the first subset and second subset. When L=3 or 4, the terminal device 120 may employ 6 bits in the first portion of the CSI to indicate the respective nonzero elements in the first subset and second subset. Hence, a payload size of at most 7-bit is enough for the first portion of the CSI according to the embodiments of the present disclosure.

As mentioned above, the first portion of the CSI in a conventional solution includes a set of wideband amplitude parameters, whose payload size for example is up to 48 bits. However, it can be seen from the above example that the payload size of the first portion of the CSI in the embodiments of the present disclosure is much smaller than the payload size of the first portion of the CSI in the conventional solution. Since the payload size of the first portion of the CSI is smaller, it is possible to use low-rate encoding to acquire satisfactory protection for the first portion without consuming too much resources, which in turn reduces the probability of error propagation from the first portion to the second portion.

At block 230, the terminal device 120 transmits, to the network device 110, the information related to the precoding matrix for the MIMO communication and channel quality indication information between the terminal device 120 and the network device 110 as the second portion of the CSI.

In some embodiments, the information related to the precoding matrix for the MIMO communication may comprise at least one of the following: an indication of the selected wideband orthogonal beams, the set of wideband amplitude parameters, subband differential amplitude parameters (also called “subband differential amplitude combining coefficients) , and subband phase parameters (also called “subband phase combining coefficients” ) . The channel quality indication information may include a channel quality indication (CQI) of the wideband or a CQI of the subband. The payload size of the indication of the selected wideband orthogonal beams and the channel quality indication information are irrelevant to the number of nonzero elements in the set of wideband amplitude parameters and the rank.

In some embodiments, if one wideband amplitude parameter in the subset of wideband amplitude parameters associated with a certain layer is quantized as zero, the terminal device 120 may not need to transmit corresponding suband phase parameters and subband differential amplitude parameters. Hence, the payload size of the subband phase parameters and the subband differential amplitude parameters is related to the number of nonzero elements in the subset of wideband amplitude parameters and the rank.

The payload of the set of wideband amplitude parameters only depends on the rank. According to the embodiments of the present disclosure, the terminal device 120 may transmit the set of wideband amplitude parameters to the network device 110 using the following three approaches. As an example, the three approaches used by the terminal device 120 are described below by taking the first subset of wideband amplitude parameters as an example. It should be appreciated that the three approaches also apply to other subsets of wideband amplitude parameters.

In the first approach, the terminal device 120 determines a peak (namely, maximum) of the wideband amplitude parameters in the first subset of wideband amplitude parameters, and transmits to the network device 110 an index of the peak and quantized wideband amplitude parameters obtained by quantizing the wideband amplitude parameters other than the peak in the first subset.

In the second approach and third approach, the terminal device 120 may transmit to the network device 110 the following three items: (1) separately-quantized or jointly-quantized indices of nonzero wideband amplitude parameters (also called “nonzero elements” ) in the first subset, or separately-quantized indices of zero wideband amplitude parameters (also called “zero elements” ) , (2) a relative index of a peak (i.e., maximum) of nonzero elements in the first subset, and (3) quantized nonzero elements obtained by quantizing nonzero elements other than the peak in the first subset. The second approach and third approach differ in using different quantization manners for the indices of the wideband amplitude parameters in the first subset. It should be appreciated that the above three items are quantized separately.

Specifically, in the second approach, the terminal device 120 separately quantizes indices of the nonzero elements or zero elements in the first subset to obtain separately-quantized indices. For example, the terminal device 120 may perform separate quantization for each nonzero element or zero element using

bits, wherein

represents upward rounding. The terminal device 120 compares the first number with the number of beams in the beam set. If the first number is smaller than or equal to the number of beams, the terminal device 120 transmits to the network device 110 the separately-quantized indices of the nonzero elements in the first subset. On the other hand, if the first number exceeds the number of beams, the terminal device 120 transmits to the network device 120 the separately-quantized indices of the zero elements in the first subset. Therefore, the network device 110 may determines indices of nonzero elements in the first subset based on the received separately-quantized indices of the zero elements in the first subset.

In the third approach, the terminal device 120 jointly quantizes indices of the nonzero elements in the first subset to obtain jointly-quantized indices. For example, the terminal device 120 may use

bits to perform joint quantization for all nonzero elements in the first subset, wherein

represents a number of all combinations of N elements selected from 2L different elements. Furthermore, the terminal device 120 transmits to the network device 110 the jointly-quantized indices of the nonzero elements in the first subset.

Payloads of wideband amplitude parameters of the three approaches are compared below by way of an example, wherein the beam set for the MIMO communication comprises L orthogonal beams with L being a natural number larger than 1, and the first subset of wideband amplitude parameters comprises 2L elements including N nonzero elements with N being a natural number greater than or equal to 1 and less than or equal to 2L. It is assumed that each wideband amplitude parameter is quantized using 3 bits.

In this example, regarding the first approach, the index of the peak (namely, maximum) in the 2L elements of the first subset is quantized as

bits, and (2L-1) elements except for the peak are quantized as 3 × (2L-1) bits. Therefore, the payload of the wideband amplitude parameters for the first approach is

bits.

Regarding the second approach, the index of each nonzero element or zero element in the first subset is separately quantized as

bits; indices of N nonzero elements are totally quantized as

bits when N ≤L, and indices of (2L-1) zero elements are totally quantized as

bits when N＞L. In addition, the relative index of the peak of the nonzero elements in the first subset may be determined by using

bits to quantize the index of the peak based on the number N of nonzero elements in the first subset. For example, it is assumed that the first subset includes 8 elements and the 8 elements have indices of 0 to 7 respectively, and that two elements with the indices of 2 and 5 are nonzero elements, and the value of the nonzero element with the index of 2 is larger, that is, the nonzero element with the index of 2 is the peak of N=2 nonzero elements. Then, one bit may be used to separately quantize the index 2 of the peak, thereby determining the relative index of the peak as 0. Alternatively, one bit may be used to quantize the index 2 of the peak as 1. In addition, (N-1) nonzero elements other than the peak in the first subset may be quantized as 3 × (N-1) bits. Therefore, when N≤L, the payload of the wideband amplitude parameters for the second approach is

bits, whereas when N ＞ L, the payload of the wideband amplitude parameters for the second approach is

bits.

Regarding the third approach,

bits are used to jointly quantize indices of the N nonzero elements in the first subset. The relative index of the peak of the N nonzero elements can be quantized as

bits. In addition, the (N-1) nonzero elements other than the peak in the first subset may be quantized as 3 × (N-1) bits. Therefore, the payload of the wideband amplitude parameters for the third approach is

bits.

Only as an example, the following Table 1 shows comparison of payloads of the wideband amplitude parameters for the abovementioned first approach, second approach and third approach when the rank is 1 and three bits are used to quantize the wideband amplitude parameters.

Table 1

In Table 1, L represents the number of beams in the beam set; N represents the number of nonzero elements in the first subset of wideband amplitude parameters. It can be seen from Table 1 that the payload of the wideband amplitude parameters for the second approach and third approach does not exceed the payload of the wideband amplitude parameters for the first approach. In other words, the second approach and third approach may be employed to reduce feedback overhead of the wideband amplitude parameters.

In some embodiments, the terminal device 120 may transmit the first portion of the CSI and the second portion of the CSI in a single time slot (also called “a first time slot” ) . In such embodiments, the terminal device 120 may transmit the first portion of the CSI and the second portion of the CSI on a physical uplink shared channel (PUSCH) between the terminal device 120 and network device 110.

In some embodiments, the terminal device 120 may transmit the first portion of the CSI and the second portion of the CSI in a plurality of time slots. For example, the terminal device 120 may transmit the first portion in a second time slot and transmit the second portion in a third time slot, and the second time slot is prior to the third time slot. In such embodiments, the terminal device 120 may transmit the first portion of the CSI and the second portion of the CSI on a physical uplink control channel (PUCCH) between the terminal device 120 and network device 110. For example, the terminal device 120 may transmit the first portion of the CSI on PUCCH with a short duration or a long duration, and transmit the second portion of the CSI on PUCCH with a long duration. The terminal device 120 may employ a periodical reporting mode or semi-static reporting mode. Regarding the periodic reporting mode, the first portion and second portion may have the same or different reporting periods. Regarding the semi-static reporting mode, the terminal device 120 may receive, from the network device 110 and via a high-layer signaling or downlink control information (DCI) , information such as activation and deactivation instructions, reporting periods and subframe offsets for the time slot for transmitting the first portion and the time slot for transmitting the second portion.

Since the payload size of the second portion depends on the rank information and the number of nonzero elements in the first portion, the payload size of the second portion is variable. Hence, allocation of the PUCCH resource in the third time slot is determined by an actual size of the payload of the second portion. In some embodiments, the network device 100 explicitly indicates the allocation of the PUCCH resource in the third time slot. In some other embodiments, the network device 110 and terminal device 120 may be pre-configured with mapping between the payload size of the second portion and available resources on the PUCCH. Therefore, the network device 110 may configure the corresponding PUCCH resources in the third time slot based on the actual size of the payload of the second portion and the mapping. The terminal device 120 may, based on the mapping, determine the resources on the PUCCH for transmitting the second portion.

Alternatively, in an embodiment in which the terminal device 120 transmits the first portion and second portion in the plurality of time slots, the terminal device 120 may transmit the first portion of the CSI on the PUCCH, and transmits the second portion of the CSI on the PUSCH. In this case, the terminal device 120 may employ a semi-static reporting mode. The first portion and second portion may have the same or different reporting periods. The terminal device 120 may receive, from the network device 110 and at least via the high-layer signaling (e.g., radio resource control signaling) , information about resource allocation for the first portion. In addition, the terminal device 120 may receive, from the network device 110 and via the DCI, information about resource allocation for the second portion.

It should be appreciated that the feedback content and payload size in the second portion of the CSI should be configured and adjusted based on the rank information and the number of nonzero elements in the latest report.

Fig. 3 illustrates a flow chart of a method 300 of the MIMO communication according to some embodiments of the present disclosure. It may be appreciated that the method 300 may be for example implemented at the network device 110 as shown in Fig. 1. For ease of description, the method 300 is described below with reference to Fig. 1.

As illustrated, at block 310, the network device 110 receives, from the terminal device 120, the number of nonzero elements in the set of wideband amplitude parameters and rank information related to the MIMO communication as a first portion of the CSI between the terminal device 120 and the network device 110. The set of wideband amplitude parameters is associated with the beam set for the MIMO communication.

At block 320, the network device 110 receives, from the terminal device 120, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device 120 and the network device 110 as a second portion of the CSI.

In some embodiments, receiving the first portion of the CSI comprises receiving the first portion in a first time slot, and receiving the second portion of the CSI comprises receiving the second portion in the first time slot.

In some embodiments, the first portion and second portion are received on a physical uplink shared channel between the terminal device 120 and the network device 110.

In some embodiments, receiving the first portion of the CSI comprises receiving the first portion in a second time slot, and receiving the second portion of the CSI comprises receiving the second portion in a third time slot, the second time slot being prior to the third time slot.

In some embodiments, receiving the first portion in the second time slot comprises receiving the first portion on a physical uplink control channel between the terminal device 120 and network device 110 or on a physical uplink shared channel between the terminal device 120 and the network device 110; and receiving the second portion in the third time slot comprises receiving the second portion on the physical uplink control channel or on the physical uplink shared channel between the terminal device 120 and the network device 110.

In some embodiments, the method 300 further comprises: transmitting, to the terminal device 120 and at least via a high-layer signaling, information on resource allocation for the first portion; and determining a resource on the physical uplink control channel for receiving the second portion, based on mapping between a payload size of the second portion and available resources on the physical uplink control channel.

In some embodiments, receiving the first portion of the CSI comprises receiving the first portion in a first period; and receiving the second portion of the CSI comprises receiving the second portion in a second period, the second period being equal to or shorter than the first period.

In some embodiments, the set of wideband amplitude parameters includes at least a first subset of wideband amplitude parameters associated with a first transmission layer between the terminal device 120 and network device 110; and receiving the number of nonzero elements in the set of wideband amplitude parameters comprises receiving a first number of nonzero wideband amplitude parameters in the first subset.

In some embodiments, receiving the information related to the precoding matrix comprises: comparing the first number with the number of beams in the beam set; in response to the first number being smaller than or equal to the number of beams, receiving separately-quantized indices of the nonzero wideband amplitude parameters in the first subset; and in response to the first number exceeding the number of beams, receiving separately-quantized indices of zero wideband amplitude parameters in the first subset.

In some embodiments, receiving the information related to the precoding matrix comprises receiving jointly-quantized indices of the nonzero wideband amplitude parameters in the first subset.

In some embodiments, receiving the information related to the precoding matrix comprises receiving a relative index of a peak of the nonzero wideband amplitude parameters in the first subset and quantized nonzero wideband amplitude parameters in the first subset.

In some embodiments, the set of wideband amplitude parameters further comprises a second subset of wideband amplitude parameters associated with a second transmission layer between the terminal device 120 and network device 110; and receiving the number of nonzero elements in the set of wideband amplitude parameters further comprises receiving a second number of nonzero wideband amplitude parameters in the second subset.

In some embodiments, the payload size of the second portion of the CSI is determined based on the first portion of the CSI.

It should be appreciated that operations performed by the terminal device 120 and relevant features described above with reference to Fig. 2 are also applicable to the method 300 performed by the network device 110, and achieve the same effect. Details are not described any more.

Fig. 4 illustrates a block diagram of a communication device 400 adapted to implement some embodiments of the present disclosure. The device 400 may be used to implement a transmitting device and a receiving device in embodiments of the present disclosure, for example, the network device 110 or terminal device 120 as shown in Fig. 1.

As shown in the example of Fig. 4, the communication device 400 may comprise one or more processors 410, one or more memories 420 coupled to the processor 410, and one or more transmitters and/or receivers (TX/RX) 440 coupled to the processor 410.

The processor 410 may be in any suitable type suitable for local technical environment, and may include but not limited to one or more of a general-purse computer, a dedicated computer, a microcontroller, a digital signal processor (DSP) and a processor based on multi-core processor architecture. The communication device 400 may also include a plurality of processors, such as a dedicated integrated circuit chip temporally driven by a clock synchronized with the master processor.

The memory 420 may be in any suitable type suitable for local technical environment, and may be implemented using any suitable data storage technologies, for example, as non-limiting examples, non-transitory computer readable storage medium, semiconductor-based storage device, magnetic storage device and system, optical storage device and system, fixed memory and removable memory.

The memory 420 stores at least part of program 430. TX/RX 440 is used for bidirectional communication. TX/RX 440 has at least one antenna to facilitate communication, but in practice, the device may have several antennas. A communication interface may represent any interface required for communication with other network elements.

The program 430 may include program instructions that, when executed by an associated processor 410, enables the device 400 to operate according to embodiments of the present disclosure, as shown in Fig. 2 to Fig. 3. That is, embodiments of the present disclosure may be implemented by computer software that may be executed by the processor 410 of the communication device 400, or implemented by hardware, or implemented through combination of software and hardware.

Generally, various exemplary embodiments of the present disclosure may be implemented in hardware or application-specific circuit, software, logic, or in any combination thereof. Some aspects may be implemented in hardware, while the other aspects may be implemented in firmware or software executed by a controller, a microprocessor or other computing device. When various aspects of the present invention are illustrated or described as block diagrams, flowcharts, or other graphical representations, it would be appreciated that the block diagrams, apparatus, system, technique or method described here may be implemented, as non-limiting examples, in hardware, software, firmware, dedicated circuit or logic, general-purpose hardware or controller or other computing device, or some combinations thereof. Examples for implementing hardware devices of embodiments of the present disclosure comprise but not limited to: a field programmable gate array (FPGA) , an application-specific integrated circuit (ASIC) , application specific standard parts (ASSP) , system on chip (SOC) , complex programmable logic device (CPLD) , and so on.

As an example, the embodiments of the present disclosure can be described in a context of machine-executable instructions which are included, for instance, in the program module executed in the device on a target real or virtual processer. Generally, a program module includes routine, program, bank, object, class, component and data structure, etc., which performs a particular task or implements a particular abstract data structure. In the embodiments, the functions of the program modules can be combined or divided among the described program modules. The machine executable instructions for the program module can be executed in a local or distributed device. In the distributed device, the program module can be located both in the local and remote storage mediums.

The computer program code for implementing the method of the present disclosure may be complied with one or more programming languages. These computer program codes may be provided to a general-purpose computer, a dedicated computer or a processor of other programmable data processing apparatus, such that the program codes when are executed by the computer or other programmable data processing apparatus, cause the functions/operations prescribed in the flowchart and/or block diagram to be implemented. The program code may be executed completely on a computer, partially on a computer, as an independent software packet, partially on a computer and partially on a remote computer, or completely on a remote computer or server.

In the context of the present disclosure, the machine-readable medium may be any tangible medium including or storing a program for or about an instruction executing system, apparatus or device. The machine-readable medium may be a machine-readable signal medium or machine-readable storage medium. The machine-readable medium may include, but not limited to, electronic, magnetic, optical, electro-magnetic, infrared, or semiconductor system, apparatus or device, or any appropriate combination thereof. More detailed examples of the machine-readable storage medium includes, an electrical connection having one or more wires, a portable computer magnetic disk, hard drive, random-access memory (RAM) , read-only memory (ROM) , erasable programmable read-only memory (EPROM or flash memory) , optical storage device, magnetic storage device, or any appropriate combination thereof.

Moreover, although the operations are depicted in a particular sequence, it should not be understood that such operations are performed in a particular sequence as shown or in a successive sequence, or all shown operations are executed so as to achieve a desired result. In some cases, multi-task or parallel-processing would be advantageous. Likewise, although the above discussion includes some specific implementation details, it should not be construed as limiting any scope of invention or claims, but should be construed as description for a particular implementation of a particular invention. In the present invention, some features described in the context of separate embodiments may also be integrated into a single embodiment. On the contrary, various features described in the context of a single embodiment may also be separately implemented in a plurality of embodiments or in any suitable sub-group.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter specified 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 of Multiple-Input Multiple-Ouput, MIMO, communication, comprising:

determining, at a terminal device, a number of nonzero elements in a set of wideband amplitude parameters, the set being associated with a beam set for the MIMO communication;

transmitting, to a network device, the number and rank information related to the MIMO communication as a first portion of Channel State Information, CSI, between the terminal device and the network device; and

transmitting, to the network device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and the network device as a second portion of the CSI.
The method according to claim 1, wherein

transmitting the first portion of the CSI comprises transmitting the first portion in a first time slot; and

transmitting the second portion of the CSI comprises transmitting the second portion in the first time slot.
The method according to claim 2, wherein the first and second portions are transmitted on a physical uplink shared channel between the terminal device and the network device.
The method according to claim 1, wherein

transmitting the first portion of the CSI comprises transmitting the first portion in a second time slot; and

transmitting the second portion of the CSI comprises transmitting the second portion in a third time slot, the second time slot being prior to the third time slot.
The method according to claim 4, wherein

transmitting the first portion in the second time slot comprises transmitting the first portion on a physical uplink control channel between the terminal device and network device or on a physical uplink shared channel between the terminal device and the network device; and

transmitting the second portion in the third time slot comprises transmitting the second portion on the physical uplink control channel or on the physical uplink shared channel.
The method according to claim 5, further comprising:

receiving, from the network device and via at least a high-layer signaling, information on resource allocation for the first portion; and

determining, based on mapping between a payload size of the second portion and available resources on the physical uplink control channel, a resource on the physical uplink control channel for transmitting the second portion.
The method according to claim 4, wherein

transmitting the first portion of the CSI comprises transmitting the first portion in a first period; and

transmitting the second portion of the CSI comprises transmitting the second portion in a second period, the second period being equal to or shorter than the first period.
The method according to claim 1, wherein

the set of wideband amplitude parameters includes at least a first subset of wideband amplitude parameters associated with a first transmission layer between the terminal device and network device; and

transmitting the number of nonzero elements in the set of wideband amplitude parameters comprises transmitting a first number of nonzero wideband amplitude parameters in the first subset.
The method according to claim 8, wherein transmitting the information related to the precoding matrix in the second portion comprises:

comparing the first number with a number of beams in the beam set;

in response to the first number being smaller than or equal to the number of beams, transmitting separately-quantized indices of the nonzero wideband amplitude parameters in the first subset; and

in response to the first number exceeding the number of beams, transmitting separately-quantized indices of zero wideband amplitude parameters in the first subset.
The method according to claim 8, wherein transmitting the information related to the precoding matrix in the second portion comprises:

jointly quantizing indices of the nonzero wideband amplitude parameters in the first subset to obtain jointly-quantized indices of wideband amplitude parameters; and

transmitting the jointly-quantized indices of the nonzero wideband amplitude parameters in the first subset.
The method according to claim 9 or 10, wherein transmitting the information related to the precoding matrix in the second portion comprises:

determining, based on the first number, a relative index of a peak of the nonzero wideband amplitude parameters in the first subset;

quantizing nonzero amplitude parameters other than the peak in the first subset to obtain quantized nonzero wideband amplitude parameters; and

transmitting the relative index of the peak and the quantized nonzero wideband amplitude parameters.
The method according to claim 8, wherein

the set of wideband amplitude parameters further comprises a second subset of wideband amplitude parameters associated with a second transmission layer between the terminal device and the network device, the second transmission layer being different from the first transmission layer; and

transmitting the number of nonzero elements in the set of wideband amplitude parameters further comprises transmitting a second number of nonzero wideband amplitude parameters in the second subset.
The method according to claim 1, wherein a payload size of the second portion of the CSI is determined based on the first portion of the CSI.
A method of Multiple-Input Multiple-Ouput, MIMO, communication, comprising:

receiving, from a terminal device, a number of nonzero elements in a set of wideband amplitude parameters and rank information related to the MIMO communication as a first portion of Channel State Information, CSI, between the terminal device and the network device, the set being associated with a beam set for the MIMO communication; and

receiving, from the terminal device, information related to a precoding matrix for the MIMO communication and channel quality indication information between the terminal device and network device as a second portion of the CSI.
The method according to claim 14, wherein

receiving the first portion of the CSI comprises receiving the first portion in a first time slot; and

receiving the second portion of the CSI comprises receiving the second portion in the first time slot.
The method according to claim 15, wherein the first and second portions are received on a physical uplink shared channel between the terminal device and the network device.
The method according to claim 14, wherein

receiving the first portion of the CSI comprises receiving the first portion in a second time slot; and

receiving the second portion of the CSI comprises receiving the second portion in a third time slot, the second time slot being prior to the third time slot.
The method according to claim 17, wherein

receiving the first portion in the second time slot comprises receiving the first portion on a physical uplink control channel between the terminal device and the network device or on a physical uplink shared channel between the terminal device and the network device; and

receiving the second portion in the third time slot comprises receiving the second portion on the physical uplink control channel or on the physical uplink shared channel.
The method according to claim 18, further comprising:

transmitting, to the terminal device and via at least a high-layer signaling, information on resource allocation for the first portion; and

determining, based on mapping between a payload size of the second portion and available resources on the physical uplink control channel, a resource on the physical uplink control channel for receiving the second portion.
The method according to claim 17, wherein

receiving the first portion of the CSI comprises receiving the first portion in a first period; and

receiving the second portion of the CSI comprises receiving the second portion in a second period, the second period being equal to or shorter than the first period.
The method according to claim 14, wherein

the set of wideband amplitude parameters includes at least a first subset of wideband amplitude parameters associated with a first transmission layer between the terminal device and the network device; and

receiving the number of nonzero elements in the set of wideband amplitude parameters comprises receiving a first number of nonzero wideband amplitude parameters in the first subset.
The method according to claim 21, wherein receiving the information related to the precoding matrix in the second portion comprises:

comparing the first number with a number of beams in the beam set;

in response to the first number being smaller than or equal to the number of beams, receiving separately-quantized indices of the nonzero wideband amplitude parameters in the first subset; and

in response to the first number exceeding the number of beams, receiving separately-quantized indices of zero wideband amplitude parameters in the first subset.
The method according to claim 21, wherein receiving the information related to the precoding matrix in the second portion comprises:

receiving jointly-quantized indices of the nonzero wideband amplitude parameters in the first subset.
The method according to claim 22 or 23, wherein receiving the information related to the precoding matrix in the second portion comprises:

receiving a relative index of a peak of the nonzero wideband amplitude parameters in the first subset and quantized nonzero wideband amplitude parameters in the first subset.
The method according to claim 21, wherein

the set of wideband amplitude parameters further comprises a second subset of wideband amplitude parameters associated with a second transmission layer between the terminal device and the network device, the second transmission layer being different from the first transmission layer; and

receiving the number of nonzero elements in the set of wideband amplitude parameters further comprises receiving a second number of nonzero wideband amplitude parameters in the second subset.
The method according to claim 14, wherein a payload size of the second portion of the CSI is determined based on the first portion of the CSI.
A terminal device, comprising:

a controller; and

a memory coupled to the controller, the memory comprising instructions, the instructions, when executed by the controller, causing the terminal device to perform the method according to any of claims 1 -13.
A network device, comprising:

a controller; and

a memory coupled to the controller, the memory comprising instructions, the instructions, when executed by the controller, causing the network device to perform the method according to any of claims 14-26.
A computer readable medium, comprising computer executable instructions, the computer executable instructions, when executed on a device, causing the device to perform the method according to any of claims 1-13.
A computer readable medium, comprising computer executable instructions, the computer executable instructions, when executed on a device, causing the device to perform the method according to any of claims 14-26.