KR20080084092A - Apparatus and method for feedback information in multiple antenna system - Google Patents

Abstract

A feedback information service device in a multi-antenna system and a method thereof are provided to transmit feedback information to a base station on the basis of a DU(Dual User)-MIMO(Multi Input Multi Output), thereby maintaining advantages of SU(Single User) MIMO and MU(Multi User) MIMO as increasing feedback efficiency. A feedback processor(410) receives feedback information from a terminal. A feedback information analyzer(412) decodes the feedback information to determine whether the current mode is a SU mode or MU mode or DU MIMO mode. A parameter determiner(414) calculates a CQI(Channel Quality Information) value by decoding the feedback information according to the determined mode. An MCS(Modulation and Coding Scheme) determiner(416) determines an MCS level according to the calculated CQI value.

Description

Apparatus and method for providing feedback information in a multi-antenna system {APPARATUS AND METHOD FOR FEEDBACK INFORMATION IN MULTIPLE ANTENNA SYSTEM}

1 is an exemplary diagram of CQI levels when extending from MU (Multi User) -MIMO to SU-MIMO;

2a is a relation between rank and layer when extending from MU-MIMO to SU (Single User) -MIMO,

Figure 2b relationship between rank and layer when extending from MU-MIMO to MU-MIMO,

3 is an exemplary view according to RLOI,

4 is a feedback transmission and reception device according to an embodiment of the present invention;

5 is an exemplary diagram for distinguishing between MU-MIMO and DU / SU-MIMO in the present invention;

6 illustrates an optimized feedback information format according to the present invention;

7 is a flowchart illustrating an operation of a base station for feedback according to an embodiment of the present invention;

8 is a flowchart illustrating a terminal operation for feedback according to an exemplary embodiment of the present invention.

The present invention relates to feedback devices and methods in a multi-antenna system, and more particularly to feedback devices and methods for a single user and multiple users using the same feedback information format in a multi-antenna system.

In a multiple antenna system for a single or multiple users, each terminal provides feedback information to a corresponding base station using a feedback channel. As the feedback information, the average channel quality information of each antenna or antennas (hereinafter referred to as "CQI"), antenna index, codebook index, rank information of multiplexing order, and antenna information (eg, Number of transmit / receive antennas). The base station collects the feedback information transmitted from multiple users and transmits data through multiple antennas according to a predetermined scheduling scheme.

In the past, many researches have been conducted on feedback techniques for single users and multiple users. Here, in the case of a single user, the terminal calculates the multiplexing order (Rank information), antenna information, the average CQI information for each antenna or antenna and transmits it to the base station. On the other hand, in the case of a maximum number of users, since the number of reception antennas is one, the terminal generally feeds back one CQI value, an antenna index at that time, and codebook index information, which is a preferred beamforming vector, to the base station. In this case, since the calculated CQI value is generally different for a single user and for a large number of users, a feedback amount is reduced and a method of feeding back the same format has been studied.

A method for determining whether the base station supports a single user or multiple users is to periodically perform a mode change request / indication in signaling at a higher layer (for example, at a MAC layer). Case), a method of alternately using a single user / multiple users with a time difference, and a method of determining and analyzing feedback information received from the terminal by the scheduler of the base station. In the first case, since the terminal needs to transmit feedback information of a single user format or feedback information of a plurality of user formats from a base station in a corresponding feedback format, feedback is unified. However, since it is divided into two usable modes on a time basis, a multi-user diversity gain is reduced by half. Most manufacturers and operators prefer the second to the first because this method degrades performance significantly, especially with fewer users.

In the second method, the scheduler determines whether the user is a single user (hereinafter referred to as "SU") or a multi-user (hereinafter referred to as "MU"), and the content of the feedback information and the constituent data are different. This is because the CQI fed back for a single user does not take into account multi-user interference, so when transitioning to multiple users, a CQI considering multi-user interference (hereinafter referred to as "MUI") should be used. . If the same CQI is used, since the MUI is not considered when scheduling with multiple users, the set throughput will be reduced. In addition, rank information, CQI for each antenna, etc., which are information required for a single user, are basically information that is not required in a maximum multi-user system in which a single user uses only one antenna.

In order to solve the above problems, the method is extended from SU-MIMO to MU-MIMO (Single Code Word: SCW, Multiple Code Words: MCW) and from MU-MIMO to SU-MIMO (Per User Unitary Rate Control (PU2RC).

값"를 SU 환경이라 가정하고 기지국으로 피드백한다. 이때, 각 레이어 별로 원하는 변조 및 코딩 방식(Modulation and Coding Scheme:MCS)을 결정하는 기준이 SINR 값은 하기 <수학식 1>로 산출된다.First, in the first case (SCW, MCW), each UE is an "antenna subset value", a base layer "CQI value" which averages the Signal to Interference plus Noise Ratio (SINR) of the antenna selected by the channel capacity expression. Reflecting a sequential interference cancellation technique (hereinafter referred to as "SIC") between layers

Assuming that the value " is the SU environment, the feedback is fed back to the base station. In this case, a criterion for determining a desired modulation and coding scheme (MCS) for each layer is calculated based on Equation 1 below.

은 채널용량 식에 의해 선택된 안테나의 SINR(Signal to Interference plus Noise Ratio)을 평균화한 베이스 레이어의 CQI 값이고, 상기

는 각 레이어 사이에서 SIC를 반영한 CQI 값이고, 상기 m은 레이어의 총 수이다.remind

Is the CQI value of the base layer obtained by averaging the Signal to Interference plus Noise Ratio (SINR) of the antenna selected by the channel capacity formula.

Is the CQI value reflecting the SIC between each layer, and m is the total number of layers.

는 필요 없기 때문에 "offset[dB]” 값을 기지국으로 알려주어야 한다. 상기 offset[dB] 값은 base layer CQI - 10*log10(MU MIMO에서 지원 하게 될 스트림의 수)에서 MU MIMO를 가정했을 경우 송신 전력이 모든 송신 안테나에 동일하게 분포하며 스트림간 간섭(inter-stream interferences)가 있다고 가정하였을 경우 최대 SINR값을 나타내는 CQI를 빼 준 값이다. 이후, 기지국은 SU-MIMO, MU-MIMO가 다양하게 섞여있는 사용자 중에서 버퍼의 상태, 셀 안에서의 사용자 수 등 관련 정보를 이용해서 적절하게 사용자를 스케줄링하게 된다. 이때 보내진 신호는 SU-MIMO에서 최대 전송속도 혹은 최대 사용자 처리율(throughput)을 지원하도록 최적화되어 있으므로 MU-MIMO를 위해서는 각 사용자의 SINR 값을 산출하는 하기 <수학식 2>이 필요하다.However, in the above feedback, if a specific user uses only one antenna, the terminal may

Since the offset [dB] should be reported to the base station, the offset [dB] is assumed to be MU MIMO in the base layer CQI-10 * log10 (the number of streams to be supported by MU MIMO). The transmission power is equally distributed to all transmission antennas and subtracts the CQI indicating the maximum SINR value if there is inter-stream interferences.Thereafter, the base station has various SU-MIMO and MU-MIMO. Among the mixed users, the user is appropriately scheduled using the relevant information such as the status of the buffer, the number of users in the cell, etc. The signal sent is optimized to support the maximum transmission rate or the maximum user throughput in SU-MIMO. Therefore, for MU-MIMO, Equation 2 below is required to calculate the SINR value of each user.

는 사용자 m의 베이스 레이어의 CQI 값, 상기

는 다수 사용자를

상기 x는 MU-MIMO에서 지원하게 될 스트림의 수이고, 상기 m은 스케줄링된 사용자 수이다.remind

Is the CQI value of the base layer of user m,

Is the number of users

X is the number of streams to be supported in MU-MIMO, and m is the number of scheduled users.

However, in the first case (SCW, MCW), MU full MU-MIMO (full SDMA where each user has only one receiving antenna and receives streams one by one) knows the offset value and works almost exactly. This method can infer a somewhat accurate CQI value due to the offset value in full MU-MIMO, where each user uses one stream, but in MU-MIMO in the general sense that the user may have more than one antenna There is a disadvantage that the performance deterioration is severe.

를 구한 후, 이를 피드백하는 방식이다. 이 방법대로 하면 기지국의 송신안테나가 네 개일 경우 필요한 피드백 정보의 양은 하기 <표 1>과 같다.The second case (PU2RC) is a feedback method extended to SU-MIMO based on full MU-MIMO. Average the largest CQI value called full CQI as shown in Figure 1 below.

After obtaining, feedback is given. According to this method, the amount of feedback information required for four transmission antennas of the base station is shown in Table 1 below.

Rank and Layer order indications  ( RLOI ) Number of CQIs Rank-1

1-Max-CQI Rank-2

1-Max-CQI + Delta-CQI Rank-3

1-Max-CQI + Delta-CQI Rank-4

1-Max-CQI + Delta-CQI Feedback overhead for RLOI = 6bits (4 + 12 + 24 + 24 = 64 combinations) Maximum CQI Feedback overhead per subband = 8bits (5bits Full CQI + 3-bits Delta-CQI)

)와 함께 layer order 정보를 보내게 된다. 도 2 (a)에서 MU-MIMO에서 SU(Single User)-MIMO로 확장시 rank와 layer의 관계도를 설명하고 있다.Here, suppose that it is SU-MIMO for rank 1 transmission. If the rank is greater than 1, the base station determines between the SU and the MU. In the case of the SU, up to two codewords may be sent as shown in FIG. In other words, for SU, two CQIs (Max CQI and

) Will send the layer order information. Figure 2 (a) illustrates the relationship between rank and layer when extending from MU-MIMO to SU (Single User) -MIMO.

는 나머지 세 스트림의 CQI의 평균값이 된다. 도 2 (b)는 MU-MIMO에서 MU-MIMO로 확장시 rank와 layer의 관계도를 도시하고 있다.In the case of MU-MIMO, the base station schedules the best CQI of one user first and then assigns another user to the second layer. As shown in the figure below, users are sequentially assigned. If the CQI value is assumed to be full MU-MIMO, then the CQI value is the CQI of the stream having the maximum SINR.

Is the average of the CQIs of the remaining three streams. Figure 2 (b) shows the relationship between rank and layer when extending from MU-MIMO to MU-MIMO.

가 기본적으로 필요하다. 그리고, 여기에 더해서 각 레이어별로 필요한 프리코딩을 위한 코드북 인덱스까지 포함하면 적어도 20 비트 이상의 정보가 필요하게 된다.In the second method, the total number of bits required is 6 bits of feedback to include each rank and antenna information (see FIG. 3 below, which shows an example of rank information and antenna information in consideration of four transmitting antennas). 5 bit full CQI and 3 bit

Is basically required. In addition, if a codebook index for precoding necessary for each layer is included, at least 20 bits or more of information is required.

에 이용하기 때문에 rank 4일 경우에 성능 열화가 심한 단점이 있다 . 그리고, 이 성능 열화가 심한 layer3, 4를 지원하기 위해 RLOI의 75%를 사용하는 단점 역시 가지고 있고 SU의 경우에는 최대 세 사용자까지의 MUI가 고려되어 있기 때문에 도달할 수 있는 성능에 훨씬 못 미쳐서 MCS level을 설정하는 단점이 있다.Therefore, the method is optimized for full MU-MIMO, but considers the use of all four streams, and has a disadvantage of excessive feedback overhead. That is, the number of rank and layer order indication (RLOI), which includes rank and antenna order, considers all four streams, but takes the average of all three streams except for one.

In case of rank 4, performance deterioration is severe . In addition, there is also a disadvantage of using 75% of RLOI to support this severe performance degradation layer 3 and 4, and in case of SU, MUI is considered to be up to three users, which is much lower than the performance that can be reached. The disadvantage is setting the level.

Accordingly, there is a need for a feedback apparatus and method for solving the performance degradation problem in the case of a multi-user based on a single user and the overhead problem of feedback information in the case of a multi-user based on a single user.

Accordingly, an object of the present invention is to provide a feedback apparatus and method in a multi-antenna system.

Another object of the present invention is to provide an apparatus and method for providing multi-user feedback information on a single user basis in a multi-antenna system.

Another object of the present invention is to provide an apparatus and method for providing single user feedback information on a multi-user basis in a multi-antenna system.

It is still another object of the present invention to provide an apparatus and method for supporting performance degradation in the case of SU-MIMO and full MU-MIMO by using the same feedback information format and DU-MIMO-optimized feedback information in a multi-antenna system. In providing.

According to a first aspect of the present invention for achieving the above object, in a transmission operation method for feedback processing in a multi-antenna system, receiving feedback information from a terminal, and decoding the feedback information to a single user (Single Determining whether the user mode, the multi user (MU) mode, or the dual user (DU-MIMO) mode, and calculating the CQI value by decoding the feedback information according to the determined mode. Characterized in that it comprises a.

According to a second aspect of the present invention for achieving the above object, in a receiving operation method for feedback processing in a multi-antenna system, receiving a pilot signal from a base station and channel estimation, the channel estimation result and DU- The method may include generating feedback information based on a dual user (DUMO) and transmitting the generated feedback information to the terminal.

According to a third aspect of the present invention for achieving the above object, a transmission apparatus for feedback processing in a multi-antenna system, a feedback processing unit for receiving feedback information from a terminal, and decoding the feedback information to a single user (Single A feedback information analyzer for determining whether a user mode, a multi-user (MU) mode, or a dual user (DU-MIMO) mode is decoded, and calculating the CQI value by decoding the feedback information according to the determined mode. Characterized in that it comprises a parameter determiner.

According to a fourth aspect of the present invention for achieving the above objects, a receiving apparatus for feedback processing in a multi-antenna system, comprising: a channel estimator for receiving a pilot signal from a base station and channel estimation; And a padback generation unit generating feedback information based on a dual user (DUMO).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, an apparatus and method for providing feedback information for a single user and multiple users using the same feedback information format in a multi-antenna system will be described.

In a real mobile environment, the base station has four transmission antennas, and each user has two reception antennas, and the radio channel also changes with time due to the mobility of the terminal. Therefore, the number of terminals using all four ranks, which are multiplexing orders, will be small. Accordingly, three scenarios can be assumed. The first scenario is when two streams are assigned to one user (hereinafter referred to as single user (SU) -MIMO), and the second scenario is when each stream is assigned to four users (hereafter full MU (Multi User). The third scenario is the case of assigning two streams to two users (hereinafter referred to as DU (Dual User) -MIMO). The present invention considers three scenarios and uses feedback information optimized for the DU-MIMO scheme without using the feedback information optimized for the SU-MIMO or the full MU-MIMO scheme. That is, the present invention will be described with respect to the apparatus and method for effectively configuring the integrated feedback information to support all of the DU-MIMO, the SU-MIMO and the full MU-MIMO. In addition, a multi-antenna system of four transmitting antennas and two receiving antennas is described as an example for convenience of description, but it is also applicable to an m * n multi-antenna system.

4 illustrates a transmission and reception apparatus for feedback in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the multi-antenna system has a structure of a multi-antenna transceiver having four transmit antennas and two or four receive antennas. Up to four users can be scheduled and on average two users are selected at the transmitter.

The transmitter is composed of a precoding unit 402, a modulator 404, an encoder 406, and a feedback processing unit 410. The scheduler 400 determines a service terminal, encodes data through the precoding unit 402, the modulation unit 404, and the coding unit 406, generates a modulation symbol, and then precodes the corresponding terminal (s). send. The feedback processor 410 is detailed as a feedback information analyzer 412, a parameter calculator 414, and an MCS determiner 416.

The encoder 406 adds a redundant bit to the information bit to allow error correction as well as error detection during decoding at the receiver. For example, the coder 406 inputs user data information bits and control data information bits, encodes them in a preset coding scheme, and outputs the encoded data to the modulator 404. Here, the coding scheme may be a turbo coding scheme or a convolutional coding scheme having a predetermined coding rate.

The modulator 404 modulates the coded bits output from the encoder 406 in a preset modulation scheme to generate a modulation symbol and output the modulated symbols to the precoding unit 402. Here, as an example of modulation, Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM) or Quadrature Amplitude Modulation (64QAM) may be used.

The precoding unit 402 beam-forms modulation symbols from the modulators 404 using information on a codebook index and then outputs the modulated symbols. That is, the precoding unit 402 receives Mt input streams and multiplies Mt * Nt (4 * 2) matrices, and generates output symbols for Nt antennas.

The feedback processor 410 receives feedback information about a channel, generates a matrix value of the precoding unit 402, and provides the matrix value of the precoding unit 402 to the precoding unit 402. Here, various MIMO techniques such as feedback precoding (Singular Value Decomposition (SVD) precoding, beamforming precoding, etc.), antenna coupling precoding, antenna selection precoding, and the like may be applied. Detailed description of these various MIMO advanced technologies will be omitted in the description of the embodiments of the present invention. In addition, the feedback processor 410 receives feedback information from the terminal and determines whether it is in SU-MIMO mode, MU-MIMO mode, or DU-MIMO mode. This is because feedback information optimized based on DU-MIMO from the UE should be decoded according to a mode determined by the base station. Thereafter, the feedback processor 410 decodes the received feedback information according to the determined mode, and then determines a modulation scheme and a transmission rate with reference to the decoded feedback information (eg, CQI) to determine the scheduler 400. Notify by.

값, RLOI(Rank and layer Order), 프리코더 인덱스 등을 포함하고 있다.The feedback information analyzer 412 receives DU-MIMO-based optimized feedback information from each of the terminals to use as SU-MIMO feedback information, MU-MIMO feedback information, or DU-MIMO feedback information. And determine to inform the parameter determiner 414 together with the feedback information. The optimized feedback information based on the DU-MIMO is used to consider a maximum CQI (Successive Interference Canceller) and SIC (Max CQI) in consideration of Multi User Interference (MUI).

Value, rank and layer order (RLOI), precoder index, and so on.

For example, the feedback information analyzer 412 is configured to distinguish between two predetermined bits of RLOI (Most Significant Bit) or LSB (Least) among the received feedback information to distinguish between full MU-MIMO and SU / DU-MIMO. Significant) For example, distinguishing full MU-MIMO and SU / DU-MIMO with reference to FIG. 6, when the RLOI 4-bit information starts with “11” from 2 bits from the left as in (a), the full MU-MIMO mode Decide on Otherwise, if it starts with "10", "01", and "00" as in (b), it is decided as DU / SU-MIMO mode. The feedback information analyzer 412 receives information such as a queue state, the number and distribution of terminals in a cell from the scheduler 410, and distinguishes between the DU-MIMO mode and the SU-MIMO mode.

값을 계산한다.The parameter determiner 414 calculates the parameter Max CQI, DU offset CQI, or SU delta CQI according to the determined mode from the feedback information analyzer 412. For example, when determined as SU-MIMO, the parameter determiner 414 uses Max CQI, SU as Equation 3 below.

Calculate the value.

는 SU(Single User)를 위한 최대 CQI 값, 상기

는 MUI 보상값(

=10*log(m), m은 MU-MIMO에서 전송 스트림 수)이고, 상기

는 SU를 위한

이다remind

Is the maximum CQI value for a single user (SU),

Is the MUI compensation value (

= 10 * log (m), m is the number of transport streams in MU-MIMO)

For SU

to be

에 추가로 할당함으로써 full CQI으로 확장하여 각 스트림 별로 정확한 MCS 레벨을 유추하도록 할 수도 있다.At this time, the bit area allocated to the precoding index

In addition to this, it can be extended to full CQI to infer the correct MCS level for each stream.

When determined as the second DU-MIMO, the parameter determiner 414 uses the feedback information sent by the UE optimized for DU-MIMO.

Max CQI = decoded received CQI (optimized for DU-MIMO)

SU Delta CQI = Received Offset CQI (optimized for DU-MIMO)

At this time, the MUI compensation value can be optimized using different metrics.

Finally, when determined as MU-MIMO, the parameter determiner 414 uses Max CQI for DU-MIMO, but extends the MSB 2 bits of the RLOI to the precoding index length. Therefore, the 4 * 4 sized precoding index can be extended to the 6 * 6 sized precoding index.

등등)를 참조하여 변조방식 및 채널코딩률을 결정한 후, 상기 스케줄러(410)로 통보한다.The MCS determiner 416 calculates a parameter Max CQI, calculated from the parameter determiner 414.

Etc.) and then determine the modulation scheme and channel coding rate, and notify the scheduler 410.

Here, the feedback information is different in the length of the CQI value that supports the three modes (SU-MIMO, MU-MIMO, DU-MIMO). Therefore, in order to match the feedback format, it is necessary to adjust the lengths of the remaining RLOIs and precoding indexes. In MU-MIMO, since only one antenna is selected, RLOI information is filled with 2 bits (four methods of selecting 1, 2, 3, and 4 antennas), and the remaining bits are filled with a precoder index. This method is more efficient because MU-MIMO reduces the MUI by allocating additional 2 bits to the precoding index instead of reducing the RLOI by 2 bits.

The receiver is composed of a detector 420, a decoder 422, a channel estimator 424, and a feedback generator 426.

The channel estimator 420 detects pilot symbols from the received signal and performs channel estimation. The channel estimation result is output to the feedback generator 426.

The feedback generator 150 generates a CQI corresponding to the channel estimation result of the channel estimator 164, adds rank and layer order indications (RLOIs), precoding indexes, and information to add DU-MIMO. The feedback information is configured based on the transmission of the feedback information to the base station 100. The base station receives the DU-MIMO based feedback information and decodes the feedback information differently in some cases (MU-MIMO, SU-MIMO, DU-MIMO).

Referring to FIG. 6 illustrating the feedback information, feedback information corresponding to MU-MIMO, DU-MIMO, and SU-MIMO will be described. First, the CQI value is determined by three methods such as SU CQI, DU CQI, and Full MU CQI. In addition, since the precoding index and the RLOI value reflect a long term correlation characteristic of the channel, the precoding index and the RLOI value are not values that are adaptively changed like CQI.

Table 2 below summarizes feedback information based on DU-MIMO.

CQI

RLOI Precoding Index DU-MIOM CQI of stream with maximum SINR CQI-CQI of the stream with the second SINR. Average SIC gain to remove interference of first CQI Assumed only when Rank is 1 and 2. (3 and 4 are not used because they don't work well because they can't send the correct CQI.) Preferred beam index. This represents the index of the preconfigured unitary codebook shared by the transceiver.

는 SU-MIMO, full MU-MIMO에 따라 다르게 해석될 수 있는 값으로, 각각 아래와 같은 기준을 가진다.here,

Is a value that can be interpreted differently according to SU-MIMO and full MU-MIMO, and has the following criteria.

{3 bits} with the corresponding antenna subset{4 bits}1) For SU-MIMO: Max CQI {5 bits},

{3 bits} with the corresponding antenna subset {4 bits}

는 Max CQI를 지원하는 계층(layer) 사이에서 얻을 수 있는 SIC 이득이다.Max CQI has no Inter Symbol Interference (ISI) and is the maximum CQI value when the total Tx Power is equally distributed among four base station antennas.

Is the SIC gain obtained between the layers supporting Max CQI.

2) For Full MU-MIMO: Max CQI {5 bits} with corresponding antenna subset {2 bits}, precoding index {4 bits}

Max CQI is the largest value among the CQI values obtained assuming MUI.

3) For DU-MIMO: Max CQI {5 bits}, Delta-CQI with the corresponding antenna subset {4 bits}

는 SU Max CQI - MU Max CQI - threshold (MUI를 고려)으로 구해진다.Max CQI is the largest CQI value obtained assuming MUI,

Is obtained as SU Max CQI-MU Max CQI-threshold (considering MUI).

The detector 420 demodulates the received signal vector by using a demodulator such as a matched filter, and then removes the interference by using the mean mean square examination (MMSE) or zero forcing (ZF) method. It estimates and outputs to the decoder 422.

The decoder 422 demodulates the received signal by a corresponding demodulation method and outputs the demodulated signal to the decoder 424. The decoder 424 decodes the signal output from the demodulator 422 in a predetermined decoding scheme and outputs the decoded signal. Here, the demodulation method and the decoding method are demodulation methods and decoding methods corresponding to the modulation method and encoding method applied by the transmitter 100.

7 is a flowchart illustrating an operation of a base station for feedback in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 7, the base station receives feedback information optimized for DU-MIMO from each terminal in step 700.

In step 702, the base station decodes the RLOI 4-bit information of the feedback information optimized for the DU-MIMO, and determines whether it is in the MU-MIMO mode or the SU / DU-MIMO mode. Here, referring to FIG. 5 as an example of determining whether the MU-MIMO mode or the SU / DU-MIMO mode is used.

In step 704, the base station determines whether it is in the SU-MIMO mode or the DU-MIMO mode in consideration of the queue state and the number and distribution of terminals in the cell.

를 산출한다. 예를 들면, 상기 DU-MIMO 모드로 결정될 시, 기지국은 DU-MIMO기반에 최적화된 피드백 정보를 그대로 사용하고, SU-MIMO 모드로 결정될 시, 기지국은 DU-MIMO기반에 최적화된 피드백 정보를 SU-MIMO기반의 피드백 정보로 변환한다. 그리고, MU-MIMO 모드로 결정될 시, 사용되지 않는 RLOI 비트정보를 확장하여 프리코딩 인덱스를 확장시킨다.In step 706, the base station determines Max CQI of the corresponding MIMO mode,

Calculate For example, when the DU-MIMO mode is determined, the base station uses the feedback information optimized for the DU-MIMO base as it is, and when the base station determines the SU-MIMO mode, the base station uses the feedback information optimized for the DU-MIMO base. Convert to feedback information based on MIMO. When the MU-MIMO mode is determined, the precoding index is extended by extending unused RLOI bit information.

등등)를 참조하여 변조방식 및 전송률을 결정한다.Thereafter, the base station calculates the parameter Max CQI,

Etc.) to determine the modulation scheme and transmission rate.

The base station then terminates the algorithm of the present invention.

8 is a flowchart illustrating a terminal operation for feedback in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 8, the terminal receives pilot data from the base station in step 800 to estimate the channel.

Thereafter, the terminal generates feedback information optimized for DU-MIMO based on the channel estimation value in step 802. The DU-MIMO based optimized feedback information will be described with reference to FIG. 6.

In the real multi-cell environment, the distribution of users in a cell is the most in DU-MIMO, assuming SU-MIMO and full MU-MIMO, assuming 4X2 and 4X4. In addition, an error caused by not fully considering the MUI in the full MU-MIMO (that is, an error caused by transmitting only the DUI without considering the full MUI in the terminal) is more deteriorated when the base station decodes the SU-MIMO or DU-MIMO. The error can be attenuated by the codebook extended by four bits. In addition, CQI, which is conventional in MU-MIMO, has the advantage of preventing performance degradation caused by sending a full set while RLOI does not send the correct value.

혹은 Max CQI로 확장시킴으로써 최대한 정확한 CQI 값들을 기지국에 전송하여 처리율을 증가시킬 수 있다.In the case of SU-MIMO, we also consider the MUI to compensate for the reduced CQI value so that it is as close as possible to link performance.

Alternatively, by extending to Max CQI, the most accurate CQI values can be transmitted to the base station to increase the throughput.

In step 804, the terminal transmits the generated feedback information to the base station.

Thereafter, the terminal terminates the algorithm of the present invention.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, by transmitting feedback information to the base station based on the DU-MIMO. It can maintain the advantages of SU-MIMO and MU-MIMO, and improve feedback efficiency by extending MSB (or LSB) to precoding index in MU-MIMO or precoding index information that is not used in SU-MIMO to CQI information. It can increase. In addition, SU-MIMO, full MU-MIMO and feedback formats remain the same and can be adaptively fed back to increase system throughput and reliability.

Claims (32)

In the transmission operation method for feedback processing in a multi-antenna system, Receiving feedback information from a terminal; Determining whether the feedback information is decoded in a single user mode, a multi user (MU) mode, or a dual user (DU-MIMO) mode; And calculating a CQI value by decoding the feedback information according to the determined mode. The method of claim 1, And determining a Modulation & Coding Scheme (MCS) level according to the calculated CQI value. The method of claim 1, The feedback information is optimized based on DU-MIMO and can be converted into feedback information for SU-MIMO or MU-MIMO. The method of claim 3, wherein The feedback information may include a CQI value for considering a rank and layer order indication (RLOI), a precoding index, a maximum CQI value, and a sequential interference canceller (SIC).

And the like). The method of claim 4, wherein Method to be divided into DU / SU-MIMO and MU-MIMO mode by the Most Significant Bit (MSB) or Least Significant (LSB) of the RLOI. The method of claim 5, The DU-MIMO and the SU-MIMO is characterized in that the scheduling is divided according to the queue status, the number of terminals in the cell, and the like. The method of claim 1, When determined in the MU-MIMO mode, using a maximum CQI optimized for DU-MIMO and extending the precoding index size. The method of claim 7, wherein The expansion of the precoding index size is determined according to the LSB or MSB size of the RLOI. The method of claim 1, And determining the DU-MIMO mode, using the feedback information as it is. The method of claim 1, Maximum CQI optimized for DU-MIMO when determined to the SU-MIMO mode,

And adding a multi-user interference (MUI) compensation value to each. The method of claim 10, The maximum CQI,

Is calculated by Equation 4 below.

Where

Is the maximum CQI value for a single user (SU),

Is the MUI compensation value (

= 10 * log (m), m is the number of transport streams in MU-MIMO)

For SU

being. In the receiving operation method for feedback processing in a multi-antenna system, Receiving a pilot signal from a base station and estimating a channel; Generating feedback information based on the channel estimation result and DU-MIMO (Dual User: DU), And transmitting the generated feedback information to the terminal. The method of claim 12, The feedback information includes a CQI value for considering a precoding index, a rank and layer order indication (RLOI), a maximum CQI, and a successive interference canceller (SIC).

And the like). The method of claim 13, The maximum CQI is characterized in that the maximum CQI value considering the multi-user interference (MUI). The method of claim 13,

Is calculated from the maximum CQI values of SU-MIMO and MU-MIMO as shown in Equation 4 below.

Where

For DU-MIMO

And

Is the maximum CQI value of SU-MIMO, and

Is the maximum CQI value of MU-MIMO. The method of claim 13, The RLOI and the precoding index is determined based on DU-MIMO. In the transmitting device for feedback processing in a multi-antenna system, A feedback processor for receiving feedback information from the terminal; A feedback information analyzer for decoding the feedback information to determine whether the mode is a single user mode, a multi-user (MU) mode, or a dual user (DU-MIMO) mode; And a parameter determiner for decoding the feedback information according to the determined mode to calculate a CQI value. The method of claim 17, And an MCS determiner for determining a Modulation & Coding Scheme (MCS) level according to the calculated CQI value. The method of claim 17, The feedback information is optimized on the basis of DU-MIMO and can be converted into feedback information for SU-MIMO or MU-MIMO. The method of claim 19, The feedback information may include a CQI value for considering a rank and layer order indication (RLOI), a precoding index, a maximum CQI value, and a sequential interference canceller (SIC).

), Etc.). The method of claim 20, Device characterized in that divided into DU / SU-MIMO and MU-MIMO mode by the Most Significant Bit (MSB) or Least Significant (LSB) of the RLOI. The method of claim 21, The DU-MIMO and the SU-MIMO is characterized in that the scheduling is divided according to the queue status, the distribution of the number of terminals in the cell. The method of claim 17, And when determined to the MU-MIMO mode, uses a maximum CQI optimized for DU-MIMO and extends a precoding index size. The method of claim 23, wherein The expansion of the precoding index size is determined according to the LSB or MSB size of the RLOI. The method of claim 17, And when the DU-MIMO mode is determined, the feedback information is used as it is. The method of claim 17, Maximum CQI optimized for DU-MIMO when determined to the SU-MIMO mode,

And multi-user interference (MUI) compensation values, respectively. The method of claim 26, The maximum CQI,

Is calculated by Equation 4 below.

Where

Is the maximum CQI value for a single user (SU),

Is the MUI compensation value (

= 10 * log (m), m is the number of transport streams in MU-MIMO)

For SU

being. In the receiving device for feedback processing in a multi-antenna system, A channel estimator for receiving a pilot signal from a base station and estimating a channel; And a padback generator for generating feedback information based on the channel estimation result and the dual user (DU-MIMO). The method of claim 28, The feedback information includes a CQI value for considering a precoding index, a rank and layer order indication (RLOI), a maximum CQI, and a successive interference canceller (SIC).

), Etc.). The method of claim 29, Wherein the maximum CQI is a maximum CQI value considering multi-user interference (MUI). The method of claim 29,

Is calculated from the maximum CQI values of SU-MIMO and MU-MIMO as shown in Equation 4 below.

Where

For DU-MIMO

And

Is the maximum CQI value of SU-MIMO, and

Is the maximum CQI value of MU-MIMO. The method of claim 29, And the RLOI and precoding index are determined based on DU-MIMO.

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