KR101513749B1 - Enhanced index search scheme for codebook based multiple antennas system using grouping - Google Patents

Abstract

The present invention relates to a codebook based on a quantized dynamic gain transmission system in which precoding matrix vector values corresponding to a specific antenna among a plurality of indexes constituting a codebook in a closed circuit based pre- And a new codebook index search method in which a mathematical calculation amount for optimal index selection for feedback execution is reduced among a plurality of indexes. The present invention provides a pre-coding transmission method for a multi-antenna system supporting a closed circuit scheme, in which a transmitting apparatus having a plurality of transmitting antennas and a receiving apparatus having a plurality of receiving antennas communicate based on a predetermined codebook, Selecting an optimal group by evenly dividing the index into a specific number of groups; And determining an optimal feedback index by performing the same optimal index search as the existing index among the selected indexes in the group.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an index search method using grouping in a multi-antenna system using a codebook,

The present invention relates to an improved index search method using grouping in a multi-antenna system using a codebook. In particular, in a closed-loop pre-coding system using a codebook, the codebook index is divided equally into a certain number of groups, And an improved index search method using grouping in a multi-antenna system using a codebook for performing an optimal index search using only selected intra-group indexes.

LTE (Long Term Evolution), which is being promoted as a wireless access standard for the 3G mobile communication system to secure a strong competitiveness in the 3GPP (3rd generation partnerdhip project), is based on the 3GPP high speed packet access (HSPA) and wideband code division This is a completely redesigned system with completely different modulation and multiplexing techniques compared to multiple access, starting with a workshop held in Toronto, Canada in November 2004 and lastly to the 61st workshop in Dresden, Germany, Discussions on technologies are continuing.

LTE-Advanced, which meets the IMT-Advanced requirements of ITU-R (international telecommunication union-radiocommunications), the international standardization organization for wireless communications under the United Nations, as the fourth generation mobile communication technology that recently advanced "LTE" There are active discussions for

The LTE system is widely recognized as an advantage of orthogonal frequency division multiplexing multiple-input multiple-output (OFDM-MIMO) technology. Therefore, unlike previous mobile communication standards, a closed- ) Type of MIMO technology. In this case, the MIMO technique for increasing the frequency efficiency by using a plurality of antennas at the transmitting and receiving ends is a technique of maximizing the transmission rate by using a spatial multiplexing (SM) technique and a transmission diversity transmit diversity. In the closed loop scheme, UEs (User Equipments) feedback channel rank information and a precoding matrix index (PMI) of a codebook in a Node B . Among the various codebooks optimized for generation efficiency and storage memory, quantized equal gain transmission (QEGT) technique proposed by David J. Love is more efficient than maximum ratio transmission (MRT) The QEGT codebook has a low complexity and is always in a nonlinear amplifier. In the non-linear amplifier of the transmitter, the amplitude of the transmitted signal is varied by using the MRT technique. This is because pre-coding with a constant amplitude is performed.

That is, there is an advantage that a diversity gain can be provided by using a relatively low-cost nonlinear amplifier. If the number of transmit antennas increases, the codebook with a larger number of indexes than the codebook with a smaller number of indexes is used. However, since the number of indexes is increased during the implementation process, As shown in FIG.

If the index can be searched without performance deterioration, then there is a need for a method of selecting the optimal index irrespective of the increase in index due to the increase of the transmission antenna in the implementation process.

The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a pre-coding scheme using a codebook, in which precoding matrix vector values corresponding to a specific antenna among a plurality of indexes are QEGT Based on the characteristics of a codebook, a codebook is divided into evenly divided groups into groups, and an optimal group is selected, and a grouping is applied to a multi-antenna system using a codebook for performing an optimal index search using only selected intra- And an object of the present invention is to provide an improved index search method.

According to an aspect of the present invention,

 A method for transmitting a code in a multi-antenna system supporting a closed loop method and in which a transmitting apparatus having a plurality of transmitting antennas and a receiving apparatus having a plurality of receiving antennas perform feedback based on a predetermined codebook, Is divided into a specific number group, and an optimum index search is performed to select an optimal group from among the selected groups and to feed back to the transmitting end using only selected intra-group indices.

Preferably, the feedback information for pre-coding in a transmission system using a multiple antenna with a plurality of channel state information and take up less link bandwidth optionally quantizer for performing a feedback process to a transmitting end at a receiving end quantized into N index codebook And the like.

Also, the codebook limits the pre-encoding matrix vector values corresponding to a specific antenna among a plurality of indexes constituting a codebook to a codebook based on a quantized dynamic gain transmission having a unit circle shape in a rectangular coordinate system.

In the pre-coding method using a codebook, an optimal index search is performed for dividing a codebook into a specific number of groups evenly, selecting an optimum group from among the divided groups, and feeding back to the transmitting end using only selected intra- The number of indexes increases in proportion to the increase in the number of transmission antennas. Therefore, unlike the conventional search method in which a problem of increase in calculation amount for optimal index selection occurs, the same error measurement performance is shown while at the same time, Is reduced.

FIG. 1 is a diagram illustrating a closed loop multi-antenna system using a codebook supporting multiple users according to an embodiment of the present invention. Referring to FIG.
FIG. 2 is an explanatory view showing characteristics of a QEGT codebook applied to a closed-loop multi-antenna system using a codebook supporting multi-users according to an embodiment of the present invention.
3 is a block diagram of a general QEGT codebook index searcher in a closed loop multi-antenna system using a codebook supporting multi-users according to an embodiment of the present invention and an improved index search method according to an embodiment of the present invention Fig.
4 is an explanatory diagram showing an arbitrary representative index and neighbor indexes in a closed-loop multi-antenna system using a codebook supporting multi-users according to an embodiment of the present invention.
Figure 5 is a clock-cycle in the present In an embodiment the closed-loop method multi-antenna system using a codebook that supports multiple users according to the invention the number of transmission antennas is 3, the number of feedback bits 4, and M = 8 be when, DSP Board And the number of index searches.
Figure 6 is a clock-cycle from when seen from the embodiment a closed-loop method multi-antenna system using a codebook that supports multiple users according to the invention the number of transmission antennas is 4, the feedback bit number 6, and M = 8 il, DSP Board And the number of index searches.
FIG. 7 is a block diagram of a closed-loop multi-antenna system using a codebook supporting multiple users according to an embodiment of the present invention. In FIG. 7, when the number of transmit antennas is 3 or 4 and the number of receive antennas is 1, 3, 4) or C (4, 6).
FIG. 8 is a block diagram of a closed-loop multi-antenna system using a codebook supporting multiple users according to an embodiment of the present invention. In FIG. 8, when the number of transmit antennas is 3 or 4 and the number of receive antennas is 2, 3, 4) or C (4, 6).

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings, with reference to the parts necessary for understanding the operation and operation according to the present invention.

According to a preferred embodiment of the present invention, a method of mapping a codebook index in a transmitter according to feedback information in a multi-antenna system supporting a closed loop scheme and a method of mapping a codebook index In the calculation for optimum codebook index selection, a process of dividing the codebook into a specific number of groups equally and then selecting an optimal group from among them, and a process of feeding back to the transmitting end using only selected in- And performing an optimal index search.

First, a process of mapping a codebook index in a transmitter according to feedback information in a multi-antenna system supporting a closed loop scheme will be described.

FIG. 1 is a diagram illustrating an example of a closed loop multi-antenna system using a codebook supporting multiple users according to an embodiment of the present invention. Referring to FIG.

In FIG. 1, one transmitting apparatus 110 and a plurality of receiving apparatuses 120-1 and 120-M are configured. The transmitting apparatus 110 may be assumed to be a base station, and a plurality of receiving apparatuses 120-1 and 120-M may be assumed to be mobile terminals. In the following description, it is assumed that one receiving apparatus 120-1 is used as a reference but the same applies to the remaining receiving apparatus.

The receiving apparatus 120-1 generates feedback information based on channel state information corresponding to each data stream. The feedback information is generated in consideration of the signal detection technique and whether or not the codebook 116 is used at the transmitting end. The receiving apparatus 120-1 transmits the generated feedback information. In this case, the feedback information may be transmitted using a channel quality indicator (CQI) indicating a channel state information, a channel matrix, and a spatial stream multiplexing scheme, And a precoding matrix indicator (PMI) that helps to precondition the pre-coding matrix W in the feedback information processing unit 114 of the MIMO transmitter.

The transmitting apparatus 110 receives feedback information from all of the receiving apparatuses 120-1 and 120-M. The transmitting apparatus 110 selects at least one user (i.e., receiving apparatus) by the feedback information. The number of users selected here can be determined by the operation mode. The operation mode is composed of a single-user mode and a multi-user mode. One user is selected in the single user mode, and a plurality of users are selected in the multi-user mode. The operation mode is determined based on the feedback information.

The transmission apparatus 110 determines a modulation and coding selection level (MCS level) based on the feedback information. When determining the MCS level, the signal detection technique of the receiving side, the operation mode, and the number of data streams supporting the selected user may be further considered.

The transmitting apparatus 110 designates the coding and modulation scheme according to the determined MCS level, and transmits the data stream corresponding to at least one user selected using the designated coding and modulation scheme.

As described above, according to the present invention, the transmission apparatus 110 determines the operation mode based on the feedback information provided from each of the reception apparatuses 120-1 and 120-M. That is, the transmitting apparatus 110 may selectively use a single user mode and a multi-user mode.

The reception apparatus 120-1 includes at least one reception antenna (Ant_rx # 1, Ant_rx # 2, ..., Ant_rx #M _R ), a channel estimation unit 122-1 and a feedback information generation unit 124-1. . The transmission apparatus 110 includes a plurality of transmission antennas (Ant_tx # 1, Ant_tx # 2, ..., Ant_tx # _{M T} ), a feedback information processing unit 114 and a signal transmission unit 112.

A signal received from at least one reception antenna (Ant_rx # 1, Ant_rx # 2, ..., Ant_rx #M _R ) is input to the channel estimation unit 122-1. The channel estimator 122-1 estimates the channel characteristics corresponding to each of the data streams from the received signal by a preset signal detection technique. At this time, the channel characteristic has quasi-static flat fading with a distribution of CN (0,1), and it is assumed that channel characteristics are constant in symbol transmission. That is, it is assumed that the fading phenomenon in the radio channel model occurs independently for each symbol. Linear detection and nonlinear detection techniques exist as signal detection techniques. LMMSE is a typical example of linear detection, and SIC is a typical example of nonlinear detection. The signal detection technique in the channel estimation unit 122-1 is specified in advance. However, if the dual mode is supported, the channel estimation unit 122-1 can selectively use an optimal signal detection technique in consideration of channel conditions and the like.

The channel characteristic matrix of the reception signal estimated by the channel estimation unit 122-1 is provided to the feedback information generation unit 124-1.

The feedback information generating unit 124-1 generates feedback information based on the channel characteristic matrix provided from the channel estimating unit 122-1. The feedback information generation unit 124-1 considers the signal detection technique used in the channel estimation unit 122-1 when generating the feedback information.

Meanwhile, the feedback information generating unit 124-1 may generate the feedback information by further considering the number of data streams provided to the user in the transmitting apparatus 110, the use of the codebook 116, 126-1, and the like . If the transmitting apparatus 110 uses the codebook 116, the pre-coding matrix indicator is included in the feedback information.

크기를 갖는데,

는 송신 안테나 포트 수,

는 공간 영역에서 독립적인 데이터를 전송하는 가상의 층을 의미하는 layer 수이다. 본 논문에서는 layer 수가 1임을 가정하여 선부호화 행렬은

인

의 벡터이다. 그리고

번째 코드북 인덱스에서 첫 번째 송신 안테나부터 M _T 번째 송신 안테나까지 지정된 임의의 선부호화 행렬 벡터는 <수학식 2>와 같다. 이 때,

는 정수이다.In this case, an arbitrary codebook W _CB is expressed by Equation (1), where N represents the total number of indexes in the codebook. Each pre-encoding matrix < RTI ID = 0.0 >

Size,

Is the number of transmit antenna ports,

Is a layer number representing a virtual layer for transmitting independent data in the spatial domain. In this paper, assuming that the number of layers is 1,

sign

. And

From the first transmission antenna from the second codebook index _T M th transmission antenna any pre-encoding matrix specified by vector is equal to the <Equation 2>. At this time,

Is an integer.

The receiving apparatus 120-1 transmits the feedback information generated by the feedback information generating unit 124-1 to the transmitting apparatus 110. [ The transmission of the feedback information by the receiving apparatus 120-1 is preferably periodically transmitted. However, it is possible to transmit the feedback information aperiodically if the elements determining the transmission time are pre-agreed between the transmitting apparatus 110 and the receiving apparatus 120-1.

Referring to the transmission apparatus 110, feedback information received from all of the reception apparatuses 120-1 and 120-M is provided to the feedback information processing unit 114. [ The feedback information processing unit 114 selects at least one user based on the feedback information received from each receiving apparatus. And determines an encoding scheme and an MCS level for transmitting the data stream of the selected at least one user.

The feedback information processing unit 114 considers the operation mode of the transmitting apparatus to select at least one user. Therefore, the feedback information processing unit 110 determines the operation mode before selecting the user. As described above, the operation mode is divided into a single user mode and a multi-user mode.

When the index vector k _opt that can obtain the optimum performance in the entire system based on the feedback information is k (1? K ? N ) th index vector in an arbitrary codebook W _CB , the feedback information processing unit 114 calculates Equation (3) is used to feed back the coding matrix indicator.

Typically, at the transmitting / receiving end, feedback is made by selecting a codebook 116, 126-1 of an appropriate size optimized for generation efficiency and storage memory.

2 is a diagram illustrating characteristics of a quantized equal gain transmission (QEGT) codebook applicable to a multi-antenna system supporting a closed loop scheme according to an embodiment of the present invention.

와 송신단의 송신 안테나 수인 M _T 가 주어질 때, 코드북 인덱스는 L = B ×(M _T - 1) 비트의 크기를 가진다. 생성되는 QEGT 코드북은 다른 송신 안테나와는 달리 첫 번째 송신 안테나에 해당되는 모든 코드워드의 위상 각도는 0이 되어 복소수가 아닌 실수 벡터값을 취하는 특징을 갖는다. 기술상의 편의를 위해 QEGT 코드북에 대한 표기법 C(M _T , L) 을 정의한다. 예를 들어 C(4, 6) 코드북에서 전체 인덱스 수는 N = 64 이다. <표 1>은 다양한 QEGT 코드북의 크기를 나타낸다. QEGT 코드북의 각 인덱스에서는 L 비트에 관계없이 첫 번째 송신 안테나에 해당하는 모든 선부호화 행렬 벡터의 위상 각도는 0으로 복소수가 아닌 동일한 실수 벡터 값을 갖는다. 그리고 두 번째 송신 안테나부터 실수가 아닌 복소수로 구성된 값을 갖는데, 동일 이득을 갖는 QEGT 코드북 특성상 두 번째 송신 안테나부터 각 송신 안테나에 해당하는 모든 선부호화 행렬들은 크기는 모두 동일하며 위상만 서로 다른 값을 갖는다.The QEGT codebook is generated by David J. Love et al. In six steps as a codebook that explains the advantages and disadvantages in detail. The coefficient used in the codebook generation is a bit used to encode each phase angle

And M _{T, which} is the number of transmit antennas of the transmitting end, the codebook index is L = B x ( M _T - 1) bits. Unlike other transmission antennas, the generated QEGT codebook is characterized in that the phase angle of all codewords corresponding to the first transmission antenna is 0, and takes a real vector value that is not a complex number. For convenience of description, the notation C ( M _T , L ) for the QEGT codebook is defined. For example, in the C (4, 6) codebook, the total number of indices is N = 64. Table 1 shows the size of various QEGT codebooks. In each index of the QEGT codebook, the phase angles of all pre-coding matrix vectors corresponding to the first transmission antenna are 0 and have the same real vector value, not a complex number, irrespective of L bits. Since the QEGT codebook has the same gain, all pre-coding matrices corresponding to the respective transmit antennas from the second transmit antenna have the same size and different values only from the second transmit antenna. .

Referring to FIG. 2, a scalar value w _{2, k} in a pre-coding matrix vector corresponding to a second transmission antenna with respect to the entire index in an arbitrary QEGT codebook is shown on a coordinate plane. The pre-encoding matrix vectors assigned to antennas all have a unit circle shape.

The improved index search method according to the present invention uses the characteristics of a QEGT codebook having a unit circle shape as shown in FIG.

3 is a block diagram of a general QEGT codebook index searcher in a closed loop multi-antenna system using a codebook supporting multi-users according to an embodiment of the present invention and an improved index search method according to an embodiment of the present invention Fig.

의

인덱스 순서가 반시계 방향으로 순차적으로 나열되도록 인덱스 순서를 재배치하는 제 1 단계(S301); 재배치된 코드북 내 인덱스를 균등하게 분할, 특정 수 의 인덱스 그룹을 생성하는 제 2 단계(S303); 최적의 인덱스 그룹을 선택하는 제 3 단계(S305); 그리고 선택된 그룹 내 인덱스만을 대상으로 최적의 인덱스를 탐색하는 제 4 단계(S307)를 포함한다.3, in the closed-loop multi-antenna system using a codebook supporting multi-users according to an embodiment of the present invention, the improved index search scheme according to the present invention is a method of searching for a second index of a QEGT codebook in a rectangular coordinate system The pre-coding coefficient corresponding to the antenna

of

A first step (S301) of rearranging the index order such that index orders are sequentially arranged in a counterclockwise direction; A second step (S303) of dividing the indexes in the rearranged codebook equally and generating a specific number of index groups; A third step (S305) of selecting an optimal index group; And a fourth step S307 of searching for an optimal index only on the selected intra-group index.

의

인덱스 순서가 반시계 방향으로 순차적으로 나열되도록 그 인덱스 순서를 재배치하는 것이다. The first step of the improved index search method according to the present invention is to use a pre-coding coefficient corresponding to the second antenna of the QEGT codebook

of

And rearranges the index order so that the index order is sequentially listed counterclockwise.

의

인덱스 순서를 재배치한다.Referring to FIG. 2, the pre-coding matrix vectors assigned to the remaining transmission antennas except for the first transmission antenna in any QEGT codebook all have a unit circular shape, but the order of each pre-coding coefficient is not sequentially listed. In order to simplify the technique for creating index groups, it is necessary to rearrange the index sequences so that the index sequences are sequentially listed. For this purpose, a pre-coding coefficient corresponding to the second antenna

of

Relocate the index order.

개의 그룹으로 인덱스들을 그룹핑하는 규칙은 다음을 따른다. 이 때, 각 그룹을 구성하는 인덱스 수는

이다.The second step is to equally divide the indexes in the rearranged codebook and generate a specific number of index groups,

The rules for grouping indexes into groups of &lt; RTI ID = 0.0 &gt; At this time, the number of indexes constituting each group is

to be.

은 2 ^L 이다. 그룹 구성을 위해 결정 가능한

및

는

의 약수 (divisor) 이어야 한다. 이를 통해

관계가 성립한다. 이 때,

인 정수일 때, 가장 빠른 인덱스 탐색을 할 수 있다.The grouping rule is a total number of indexes in a QEGT codebook composed of L bits of index

Is ^2L . Determinable for group composition

And

The

It should be a divisor of. because of this

The relationship is established. At this time,

, The fastest index search can be performed.

,

이 주어질 때, 전체 대표자 인덱스 벡터

는 식 <수학식 4>와 같다. 이 때,

은 정수이다.Named as the representatives index in each group

,

, The full representative index vector

Is expressed by Equation (4). At this time,

Is an integer.

을 포함한

번째 그룹을 구성하는 인덱스를 나타낸다.&Quot; (5) &quot; represents the representative index

Including

Lt; th &gt; group.

개의 그룹으로 인덱스가 균등하게 분할된 QEGT 코드북에서 최적의 그룹을 선택하는 것이며, <수학식 6>에서

번째 그룹이 최적의 그룹으로 선택된다.Assuming that the optimal index group to be selected is m _opt group and H is a channel matrix, the third step is to select

The optimal group is selected in the QEGT codebook in which the indexes are equally divided into the group of

Th group is selected as the optimum group.

번째 그룹 내 인덱스만을 <수학식 3>에 적용하여 피드백을 위한 최적의 인덱스를 선택하는 것이다. 이 때,

는 <수학식 6>을 통해 이미 계산되었기 때문에 이 단계에서는 계산을 생략한다. 즉, 이 두 번째 단계에서 계산되는 그룹 내 인덱스 수는

이 된다.The fourth step is to select

Th group is applied to Equation (3) to select an optimal index for feedback. At this time,

Is already calculated through Equation (6), so calculation is omitted at this step. That is, the number of in-group indexes calculated in this second step is

.

는

개가 필요하다. 이는 기존 탐색기법에 의한 전체 인덱스 수

보다 그 수가 매우 작다

.From the above, the total index calculated to determine the optimal feedback index

The

I need a dog. This is because the total index number

The number is much smaller than

.

과

값, 그리고 각 구성에 대해 본 발명에 따른 검색기법에 의해 실제로 계산되는 전체 인덱스 수를 나타낸다. Table 1 shows that if the number of transmit antennas is 3 and 4, grouping can be configured in each QEGT codebook with an appropriate index size

and

Value, and the total number of indices actually calculated by the search technique according to the present invention for each configuration.

Comparison of the calculation amount and the reduced amount of the index k required in the conventional method and the method according to the present invention for the optimal codebook index selection when the number of transmission antennas is 3 or 4 M _T L N M Q Proposed
( M + Q- 1) RCR (%)
3

4

16
2 8 9 56.3 4 4 7 43.7 8 2 9 56.3

4



6



64

2 32 33 51.6 4 16 19 29.7 8 8 15 23.4 16 4 19 29.7 32 2 33 51.6

의해 계산되는 감소된 복잡도율(reduced complexity rate, RCR)은 송신 안테나 수에 따라 기준(100%) 대비 24%까지 감소함을 보인다. 이 때, 기존 탐색기법에 의한 전체 인덱스 수 N = 2 ^L 은 QEGT 코드북 생성 방법에 따라 여러 L 비트의 인덱스로 구성이 가능하다. 그러나 일반적으로 코드북을 구성하는 선부호화 계수들이 다양한 채널에서 오류 발생 없이 성공적으로 동작하기 위해서는 양자화 오차율이 감소될 수 있도록 충분한 수의 선부호화 계수들이 구성되어야 하지만, 코드북 크기가 증가해도 이상적이 오류 발생 확률을 갖는 한계 구간이 존재하기 때문에 적절한 크기를 가지는 코드북을 선택해야 한다. 따라서 <표 1>에서는 적절한 크기의 피드백 비트를 갖는 전체 인덱스 수

을 선택하였다.As shown in Table 1, in order to numerically represent the amount of the reduced index

The reduced complexity rate (RCR) calculated by the number of transmit antennas is reduced by 24% from the reference (100%). In this case, the total number of indexes N = 2 ^L by the conventional search technique can be composed of several L- bit indexes according to the QEGT codebook generation method. However, in order for the pre-coding coefficients constituting the codebook to operate successfully without errors in various channels, a sufficient number of pre-coding coefficients should be configured to reduce the quantization error rate. However, even if the codebook size increases, The codebook having an appropriate size must be selected. Therefore, in Table 1, the total number of indexes with appropriate size feedback bits

Were selected.

,

인 경우 본 발명에 따른 인덱스 탐색기법을 적용하였을 경우 임의의 그룹을 구성하는 대표자 인덱스와 그룹 내 다른 인덱스들을 보인 설명도이다.FIG. 4 is a block diagram illustrating a structure of a 6-bit QEGT codebook in a multi-antenna system supporting a closed loop according to an embodiment of the present invention.

,

A representative index constituting an arbitrary group and other indexes in the group when the index search technique according to the present invention is applied.

을 좌표평면에 사각형(□)으로 나타내었다. 만약 w _2,9 즉, QEGT 코드북 내의 대표자 인덱스 9 가 포함된 그룹이 최적의 그룹으로 선택된다면, 이 때 생성되는 그룹은 [w _2,6 w _2,7 w _2,8 w _2,9 w _2,10 w _2,11 w _2,12 w _2,13 ] 이 되며, 이를 좌표평면에 삼각형(△)으로 표시한다. 이 후, 상기 8 개의 인덱스 중에서 최적의 인덱스가 <수학식 3>에 의해 결정, 송신단으로 피드백이 수행된다. 이 때, 선택된 그룹 내 인덱스만을 <수학식 3>에서 계산할 경우 앞서 계산된 w _2,9 를 제외한 7 개의 인덱스만이 적용된다. 즉, 전체 과정에서 계산된 k는 모두 15번으로 기존 탐색 방법에서의 64번보다 그 인덱스 계산량이 감소한다.Referring to Figure 4, the number of representative indices, i.e., eight representative indices calculated for group creation

(□) in the coordinate plane. If w _2,9, ie, the group containing the representative index 9 in the QEGT codebook is selected as the optimal group, then the generated group is [ w _2,6 w _2,7 w _2,8 w _2,9 w _{2 , 10} w _2,11 w _2,12 w _2,13 ], which is indicated by a triangle (?) On the coordinate plane. Thereafter, an optimal index among the eight indexes is determined by Equation (3), and feedback is performed to the transmitting end. In this case, when only the in-group indexes are calculated in Equation (3), only the seven indices excluding w _2,9 calculated above are applied. That is, the number of k computed in the entire process is 15, and the index calculation amount is reduced from 64 in the conventional search method.

In order to accurately measure the performance of the new index search method according to the present invention, a Monte Carlo simulation using a TMS320C6713 DSP board of Texas Instruments (TI) was performed to analyze the number of clock cycles and performance with the conventional index search method. The PDP (power delay profile) for the multipath channel is the Pedestrian B of the ITU-R model. The wireless channel model has quasi-static flat fading with CN (0, 1) distribution, and assumes that channel characteristics are constant in symbol transmission. That is, the fading phenomenon in the radio channel model occurs independently for each symbol. Also, the noise is additive white gaussian noise (AWGN) having a distribution of CN (0, N ₀ ) . In this case, CN (·) denotes a complex normal distribution. It is assumed that channel estimation and synchronization and correlation between antennas are both ideal.

FIG. 5 is a block diagram of a closed-loop multi-antenna system using a codebook for supporting multiple users according to an embodiment of the present invention. Referring to FIG. 5, when the number of transmit antennas is 3, the number of feedback bits is 4, (A) and the number of index searches (b).

FIG. 6 is a block diagram of a closed-loop multi-antenna system using a codebook supporting multiple users according to an embodiment of the present invention. In FIG. 6, when the number of transmission antennas is 4, the number of feedback bits is 6, (A) and the number of index searches (b).

5 and 6, (a) shows the number of clock-cycles by the TI DSP board, and (b) shows the number of index decrement. In FIG. 5, the number of clock cycles is reduced by about 45%. In FIG. 6, the number of clock cycles is reduced by about 75%. At this time, since the state is not optimized for the DSP implementation, the numerical value can fluctuate within the error range. In this case, since the state is not optimized for the DSP implementation, the number of clock-cycles for the conventional index search technique is normalized to 1, and then the number of clock-cycles for the index search technique according to the present invention is also normalized .

7 is a case where the number of transmit antennas in a multiple antenna system of the closed-loop system using a codebook that supports multiple users according to an embodiment of the present invention is 3 or 4, the number of receiving antenna 1 by applying an improved index search technique codebook C ( 3, 4) or C (4, 6).

8 is a case where the number of transmit antennas in a multiple antenna system of the closed-loop system using a codebook that supports multiple users according to an embodiment of the present invention is 3 or 4, the number of receive antenna 2 by applying an improved index search technique codebook C ( 3, 4) or C (4, 6).

As shown in FIGS. 7 and 8, the performance of the improved index search method according to the present invention is the same as that of the existing index search method.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

Further, in the above description, specific details of the improved index search method employing grouping in a multi-antenna system using the codebook of the present invention are shown in order to provide a more thorough understanding of the present invention. Without these specific details, It will be apparent to those skilled in the art that the present invention can be readily practiced by those skilled in the art.

Claims (6)

A pre-coding transmission method of a multi-antenna system communicating based on a QEGT codebook,
A first step of rearranging the index order so that all the index orders of the pre-coding coefficients corresponding to the second antenna of the QEGT codebook are sequentially arranged in a counterclockwise direction in a rectangular coordinate system;
A second step of dividing the indexes in the codebooks rearranged in the first step equally to generate a specific number of index groups;
A third step of selecting one of the plurality of index groups in the second step; And
And a fourth step of searching for one index suitable for feedback to the transmitting end only on the indexes in the index group selected in the third step,
The representative index u _m in each index group generated in the second step is defined as Equation (1)

,

Equation 1
Full representative index vector

Is determined by Equation (2). &Lt; RTI ID = 0.0 &gt; [10] &lt; / RTI &gt;

Equation 2
In the above equations (1) and (2), m is an integer,

Is the number of index groups,

Is the number of indexes that make up the group. 2. The method of claim 1, wherein the step of generating the index group of the second step

Groups of indexes, and the number of indexes constituting the group

, Which can be determined for group composition

And

Is the total number of indexes

Lt; / RTI &gt;

Wherein the grouping is performed in a multi-antenna system using a codebook. delete 2. The method according to claim 1, wherein, in the second step,

Including

Th group is determined by Equation (3). &Lt; RTI ID = 0.0 &gt; A &lt; / RTI &gt;

Equation 3 2. The method of claim 1, wherein when the index group selected in the third step is m _opt group and H is a channel matrix,

Th group is determined by Equation (4): &quot; (4) &quot;

Equation 4 2. The method of claim 1, wherein in the fourth step, the representative index calculation in the index group selected in the third step is already performed and is omitted.

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