KR20080050921A - Apparatus and method for transmitting/receiving data in a mobile communication system using multiple antennas - Google Patents

Abstract

An apparatus and a method for transmitting/receiving feedback information in a mobile communication system using an array antenna are provided to provide a high data transmission rate with a smaller amount of feedback information. A receiver(130) estimates a fading channel of reception data to determine a weight value set having a maximum data transmission rate in at least one weight value set having a plurality of mutually orthogonal weight vectors as elements, and transmits feedback information having the determined weight value set and state information of each channel to a transmitter(110). The transmitter demultiplexes data to be transmitted into at least one sub-data stream based on the feedback information, multiplies a corresponding weight value to each demultiplexed sub-data stream, and transmits the same. In the state information of each channel, the amount of feedback information is adaptively controlled according to the number of weight vectors.

Description

Apparatus and method for transmitting / receiving data in a mobile communication system using an array antenna {APPARATUS AND METHOD FOR TRANSMITTING / RECEIVING DATA IN A MOBILE COMMUNICATION SYSTEM USING MULTIPLE ANTENNAS}

1 illustrates a system in accordance with an embodiment of the present invention.

2 is a flowchart illustrating a data transmission / reception method performed by a receiver of a system according to an embodiment of the present invention.

3 is a flowchart illustrating a data transmission / reception method performed in a system transmitter according to an embodiment of the present invention.

4 and 5 are flowcharts illustrating a method of determining a weight set in a system of the present invention.

Figure 6 is a graph showing the results of experiments comparing the performance of the prior art and the system of the present invention in an environment with spatial correlation

7 is a graph showing the results of experiments comparing the performance of the prior art and the system of the present invention in an environment without spatial correlation

8 is a flowchart illustrating a process of setting and rearranging sub data column state information according to the number of selected weight vectors.

9 is a flowchart illustrating a process in which a transmitter receives sub data column state information according to the number of selected weight vectors and corresponds to the selected weight vector.

The present invention relates to a data transmission and reception apparatus and method of a mobile communication system, and more particularly, to a data transmission and reception apparatus and method for implementing spatial multiplexing in a mobile communication system using a transmission and reception array antenna.

The mobile communication system has evolved into a high speed, high quality wireless data packet communication system for providing data service and multimedia service, instead of providing an initial voice-oriented service. The standardization of HSDPA (High Speed Downlink Packet Access), which is currently centered on 3GPP, and 1xEV-DV, which is centered on 3GPP2, is designed for high-speed, high-quality wireless data packet transmission services of 2Mbps or higher in 3G mobile communication systems. It can be seen as a representative of the effort to find a solution. On the other hand, the fourth generation mobile communication system is based on the provision of more high-speed, high quality multimedia services.

In order to provide high-speed and high-quality data service in wireless communication, a spatial multiplex transmission scheme using a multiple input multiple output (MIMO) antenna system using multiple antennas at a transmitter and a receiver is proposed. Spatial multiplexing transmits different data streams for each transmitting antenna simultaneously, so that the capacity of serviceable data increases linearly with the number of transmitting / receiving antennas as the number of transmitting / receiving antennas increases theoretically without increasing the additional frequency bandwidth. It is known.

Spatial multiplexing techniques provide high capacity in proportion to the number of transmit / receive antennas when the fading between transmit / receive antennas is independent, but in a highly spatially correlated environment of fading, the capacity is significantly higher than in an independent fading environment. Decreases. This is because, as the correlation between fading between transmit / receive antennas increases, fading experienced by signals transmitted from each transmit antenna becomes similar, making it difficult to distinguish spatially at the receiving end. In addition, the transmittable capacity is influenced by the signal-to-noise ratio (SNR) of the receiver. The lower the received SNR, the lower the transmission capacity. Therefore, the transmission data rate can be maximized only by adjusting the number of data streams transmitted simultaneously and the transmission rate of each data stream according to the radio channel state, that is, the spatial correlation of fading and the received SNR. If the data rate to be transmitted exceeds the transmission capacity that a wireless channel can provide, many errors occur due to interference between data streams transmitted at the same time, and the actual data rate is reduced.

Accordingly, in-depth studies on the precoding scheme have been conducted to increase the transmission data rate of the spatial multiplex transmission scheme. The precoding scheme is a technique of multiplying transmission weights by each data string to be transmitted by a transmitter using downlink channel information from a transmitter to a receiver. Therefore, the transmitter needs to know the downlink channel state from each transmitting antenna of the transmitter to each receiving antenna of the receiver. To this end, the receiver estimates the downlink channel state and then feeds back the downlink channel state information estimated through the feedback channel to the transmitter. However, the receiver must transmit a large amount of feedback data using the uplink feedback channel in order to feed downlink channel state information to the transmitter. If a large amount of feedback data transmission is required, it takes a lot of time for the receiver to feed downlink channel state information to the transmitter by using the bandwidth-limited uplink feedback channel. Becomes impossible. Therefore, there is an urgent need for a technique for maximizing the data rate by precoding while minimizing the amount of feedback data transmitted from the receiver to the transmitter.

개의 프리코더들로 이루어진 프리코더 코드북이 송신기와 수신기간에 미리 설정된다. 페이딩이 시간에 따라 변하기 때문에 상기 프리코더 결정 과정은 매 시간 슬롯마다 반복되어야 하고 이에 따라 결 정된 프리코더 인덱스를 매 시간 슬롯마다 송신기로 피드백해준다.As a conventional technique of reducing the amount of feedback information, a precoder codebook technique has been proposed. The precoder codebooking method, in a precoder codebook consisting of a limited number of precoders known to a transmitter and a receiver, determines that a receiver has a maximum data rate among candidate precoders, and the precoder Feedback of the index to the transmitter. The transmitter transmits data using the precoder corresponding to the index fed back from the precoder codebook. For example, using 4 bit feedback information,

A precoder codebook consisting of three precoders is preset between the transmitter and the receiver. Since fading changes over time, the precoder decision process must be repeated every time slot, thus feeding back the determined precoder index to the transmitter every time slot.

개, 수신 안테나가

개인 다중 입출력 안테나 시스템을 가정할 때, 채널 상태 정보를 피드백할 경우, 총

개의 복소수 채널 계수를 피드백해야 한다. 따라서, 한 복소 채널 계수를 나타내는데 Q bit가 필요하다고 하면, 총

bit가 필요하다. 이에 반해 프리코더 코드북기법은 충분한 데이터 율을 제공하는 프리코더들의 수를 K 라고 하면,

bit가 필요하다, 여기서

는 x 보다 크거나 같은 정수이다. 따라서, 송수신 안테나 수의 곱에 비례하여 피드백 정보량이 증가하는 채널 상태 정보를 이용하는 프리코딩 기법과는 달리, 프리코더 코드북 기법은 송수신 안테나 수에 상관없이 프리코더 코드북에 포함되는 프리코더 수, 즉 프리코더 코드북의 크기에 의해 결정된다. The precoder codebook method requires a smaller amount of feedback information than the precoding method using the feedback channel state information. Transmit antenna

Dog receiving antenna

Assuming a personal multiple input / output antenna system, when feeding back channel state information,

Complex channel coefficients should be fed back. Therefore, if Q bits are required to represent one complex channel coefficient,

bit required On the other hand, if the precoder codebook method uses K as the number of precoders that provide a sufficient data rate,

bit needed, where

Is an integer greater than or equal to x. Therefore, unlike the precoding scheme that uses channel state information in which the amount of feedback information increases in proportion to the product of the number of transmit and receive antennas, the precoder codebook scheme uses the number of precoders included in the precoder codebook regardless of the number of transmit and receive antennas. Determined by the size of the coder codebook.

The precoder codebooking technique should include ready-made precoders in the codebook that quantize the precoders for all possible cases that may occur in spatial multiplexing. The precoder codebook method can reduce the amount of feedback information by using the predetermined precoders, but also reduces the degree of freedom of the precoding matrix. The reduction in the degree of freedom of the precoding matrix increases the size of the precoder codebook by significantly increasing the number of predetermined precoders to consider in many cases. In the following two cases, the codebook size of the precoder codebook technique is significantly increased.

First, in order to apply to a channel environment having various spatial correlations, all the precoders according to the spatial correlations of the channels must be considered, so the number of precoders to consider increases exponentially. The optimal precoder codebook depends on the spatial correlation of the channel. The technology precoder codebook technology proposed to date designs a precoder codebook on the assumption of a spatially irrelevant fading channel. However, the distribution of eigenvectors having a large effective eigenvector, that is, an eigenvalue, varies according to the spatial correlation of the fading channel, and thus, optimal precoders. As a result, in order to achieve high data rates, a large number of precoder codebooks optimized according to the spatial correlation of fading channels must be used.

(송신 안테나 수와 수신 안테나 수 중에서 작은 수)까지 변하게 된다. 동시에 전송되는 데이터 스트림 수에 따라 프리코더 행렬의 열(column)의 수를 변화시켜야 하는데, 이는 프리코더 행렬을 이루는 열 벡터들이 가중치 벡터로서 각 데이터 스트림에 곱해지 기 때문에, 프리코더 행렬의 열 벡터 수와 동시에 전송되는 데이터 스트림 수가 일치해야 하기 때문이다. 예를 들어, 송수신 안테나 수가 모두 4일 경우, 동시에 전송 가능한 데이터 스트림 수는 1에서 4까지 변하게 되므로, 고려되어야 할 프리코더들은 열 벡터의 수가 1 인 미리 정해진 프리코더들, 열 벡터의 수가 2인 프리코더들, 열 벡터 수가 3인 프리코더들, 그리고 열 벡터 수가 4인 프리코더들이 고려되어야 한다. 더구나, 송수신 안테나 수가 증가하여 동시에 전송할 수 있는 최대 데이터 스트림 수가 증가할 경우, 고려해야 할 프리코더의 수 증가에 따른 상당히 많은 피드백 정보량이 요구된다, 따라서, 채널 환경에 따라 동시에 전송되는 데이터 스트림 수와 전송 데이터 율을 가변시켜 해당 채널 환경에서 최대 전송률을 이루려는 공간 다중화 전송 방식에는 이러한 프리코더 코드북 기법의 적용이 어렵다. 상술한 바와 같이 미리 정해진 프리코드들의 집합을 사용하는 프리코더 코드북기법은 송신 안테나 수와 동시에 전송되는 데이터 스트림 수에 따라 프리코더 코드북의 크기가 커져 실제 적용이 어려운 경우가 발생한다.Second, when adjusting the number of data streams transmitted simultaneously according to the channel environment, all precoders according to the number of data streams transmitted at the same time must be considered, so the number of precoders to consider increases exponentially. The number of data streams transmitted simultaneously is from 1 to the maximum depending on the channel environment.

(The smaller of the number of transmitting antennas and the number of receiving antennas). The number of columns of the precoder matrix must be changed according to the number of data streams transmitted at the same time, since the column vectors constituting the precoder matrix are multiplied by each data stream as a weight vector, so that the column vectors of the precoder matrix This is because the number of data streams transmitted simultaneously with the number must match. For example, if the number of transmit / receive antennas is all 4, the number of data streams that can be transmitted simultaneously varies from 1 to 4, so the precoders to be considered are predetermined precoders having 1 column vector and 2 having 2 column vectors. Precoders, precoders with column vector number 3, and precoders with column vector number 4 should be considered. Moreover, when the number of transmit / receive antennas increases and the maximum number of data streams that can be transmitted at the same time increases, a considerable amount of feedback information is required as the number of precoders to be considered increases. It is difficult to apply the precoder codebook technique to the spatial multiplexing transmission scheme that tries to achieve the maximum data rate in the channel environment by varying the data rate. As described above, in the precoder codebook method using a predetermined set of precodes, the size of the precoder codebook increases depending on the number of transmit streams and the number of data streams transmitted at the same time.

In addition, receivers communicating with one transmitter may use different numbers of antennas, for example, when the number of base station antennas is 4 and the mobile stations have 1, 2, 3, or 4 antennas depending on the terminal type. The maximum number of sub data streams that can be transmitted are 1, 2, 3, and 4, respectively. Therefore, when applying the precoder codebook technique, the precoder codebooks according to the number of available receiver antennas must be defined, and respective feedback channels must be defined accordingly. Each receiver should select and use a precoder codebook and corresponding feedback channel according to the number of antennas of the corresponding receiver. This requires a process and feedback information between the transmitter and the receiver to promise the precoder codebook to use and the corresponding feedback channel. Therefore, there is a need for a flexible precoding technique that can be applied to various transmit and receive antenna structures.

In conclusion, in a channel environment with various spatial correlations, it is possible to apply the spatial multiplexing transmission method that adjusts the number of data streams transmitted simultaneously according to the channel environment, and provides an efficient precoding that provides a high data rate with only a small amount of feedback information. Research on methods and feedback methods is required.

Accordingly, an object of the present invention is to provide a data transmission / reception apparatus and method for efficiently providing a data rate according to a channel environment in a mobile communication system using a transmission / reception array antenna.

Another object of the present invention is to provide a data transmission / reception apparatus and method for providing a high data rate with a small amount of feedback information in a mobile communication system using a transmission / reception array antenna.

Another object of the present invention is to provide an apparatus and method for generating efficient feedback information in a mobile communication system using a transmit / receive array antenna.

A system according to an embodiment of the present invention for achieving the above object is to estimate the fading channel of the received data weighted set to maximize the data rate of the at least one set of weights with a plurality of weight vectors orthogonal to each other as an element A receiver for transmitting feedback information including the determined weight set and channel-specific state information to a transmitter, and demultiplexing data to be transmitted based on the feedback information into at least one sub data string, And a transmitter for multiplying a sub-data string by a corresponding weight and transmitting the weight, wherein the state information for each channel is adaptively adjusted according to the number of weight vectors.

The receiver includes a downlink channel estimator for estimating a channel state using a pilot channel of data transmitted from the transmitter, and determines the weight set and the weight vector based on the channel state to determine the weight set and weights in the transmitter. And a weight selector for transmitting information about a vector, and a sub-channel state estimator for estimating a channel state for each sub-data according to the determined weight vector and transmitting only the channel state for each sub-data to the transmitter.

The receiver includes a downlink channel estimator for estimating a channel state by using a pilot channel of data transmitted from the transmitter, and determines the weight set and the weight vector based on the channel state, and determines the weight set by the transmitter. And a weight selector for transmitting to the subchannel and a state estimator for estimating the channel states of all the weight vectors in the determined weight set and transmitting them to the transmitter.

The sub-channel state estimator transmits a 'no transmission' state for a channel not used based on the determined weight vector.

The transmitter receives a demultiplexer for demultiplexing a main data string to be transmitted with a predetermined sub data string, and receives the demultiplexed at least one sub data string and independently performs channel encoding and modulation by a predetermined channel coding rate and a modulation scheme. At least one channel encoder and modulator for performing a multiplication, a beam forming machine for multiplying the at least one channel encoding and modulated subdata string by a predetermined weight, and transmitting the multiplied weight to the receiver, and based on the feedback information transmitted from the receiver. And a controller configured to predetermine the number of sub data strings, the encoding rate of the sub data strings, a modulation scheme, and a weight to be multiplied by each sub data string.

The feedback information may include weight index information indicating the determined weight set, weight vector information indicating a sub data string used in the determined weight set, and channel state information of the sub data string.

The transceiver may be configured to store in advance a weight set and a weight vector determined according to the number of the transmit / receive antenna and the weight set.

In accordance with an aspect of the present invention, a method for transmitting and receiving data according to an embodiment of the present invention includes a first process of estimating a fading channel from a pilot channel of received data at a receiver and a plurality of orthogonal to each other based on the estimated fading channel. A second process of determining a weight set maximizing a data rate among at least one weight set having weight vectors as an element, a third process of estimating state information for each channel according to the determined weight set, and the determined weight And a fourth process of transmitting feedback information including aggregation and state information for each channel to the transmitter, and a fifth process of transmitting data to be transmitted for each array antenna based on the feedback information in the transmitter. do.

The method of designing the weight set includes determining a plurality of weight vectors having a phase difference determined according to the number of the transmitting antennas and the number of weight sets, and a weight vector orthogonal to the orthogonal weight vector among the determined plurality of weight vectors. Characterized in that it comprises a configuration process.

Another method of designing the weight set is characterized in that the first process of determining a plurality of weight vectors orthogonal to each other in a predetermined number of weight sets and repeating the first process by the number of the determined weight sets. .

The first process may include determining a reference phase in which the elements of the determined weight vector are orthogonal to each other, and determining the elements so that the reference phase difference occurs from the first element of the weight vector.

The feedback information may include weight index information indicating the determined weight set, weight vector information indicating a sub data string used in the determined weight set, and channel state information of the sub data string.

The feedback information may include weight set index information indicating the determined weight set, and channel state information of all sub data in the determined weight set.

In a data transmitting / receiving method according to an embodiment of the present invention, the fifth process includes demultiplexing a main data sequence to be transmitted into at least one sub data sequence based on the feedback information, and channel encoding determined based on the feedback information. Performing channel encoding and modulation on the demultiplexed at least one subdata string by a rate and a modulation scheme independently; multiplying the channel encoding and modulated subdata string by a weight determined based on the feedback information; It characterized in that it comprises the process of transmitting to.

In accordance with an embodiment of the present invention for achieving the above object, at least one weight set having elements of a plurality of weight vectors orthogonal to each other by estimating a fading channel of received data is applied at a predetermined time, A receiver for determining a weight vector maximizing a data rate for a set of weights used at a time point, and transmitting feedback information including the determined weight vector and state information for each channel to the transmitter, and receiving the feedback information in advance. And a transmitter for demultiplexing the data to be transmitted into at least one sub data string based on the weight vector of the weight set applied at the determined time, and multiplying each demultiplexed sub data string by a corresponding weight.

The receiver determines a weighted vector information in a set of weights applied to a predetermined time based on the channel state and a downlink channel estimator that estimates a channel state using a pilot channel of data transmitted from the transmitter. And a weight selector for transmitting to the sub-channel state estimator for estimating a channel state of the selected weight vector and transmitting the estimated channel state to the transmitter.

The transmitter receives a demultiplexer for demultiplexing a main data string to be transmitted with a predetermined sub data string, and receives the demultiplexed at least one sub data string to independently encode and modulate the channel by a predetermined channel coding rate and a modulation scheme. At least one channel encoder and modulator for performing multiplication, a beam molding machine for multiplying the at least one channel encoding and modulated subdata string by a predetermined weight, and transmitting the predetermined weight to the receiver, and transmitting the at least one channel encoder from the receiver at a time applied to the set of weights. And a controller configured to predetermine a number of the sub data strings, a coding rate of the sub data strings, a modulation scheme, and a weight to be multiplied by each sub data string based on the received feedback information.

The transceiver may be configured to store in advance a weight set and a weight vector determined according to the number of the transmit / receive antenna and the weight set.

A data transmission and reception method according to a second embodiment of the present invention for achieving the above object is a first process of estimating a fading channel from a pilot channel of received data at a receiver, and a plurality of orthogonal to each other based on the estimated fading channel And a second process of determining a weight vector that maximizes a data rate with respect to the weight set used at a predetermined time point, wherein at least one weight set having elements of the weight vectors is applied to a predetermined time; A third step of estimating the state information for each channel according to the present invention; a fourth process of transmitting the feedback information including the determined weight vector and the state information for each channel to the transmitter; To send weights based on the weight vector of the set of weights applied over time. And the emitter, characterized in that it comprises the step of transmitting for each array antenna.

DETAILED DESCRIPTION Hereinafter, detailed descriptions of preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same components in the drawings represent the same numerals wherever possible. Specific details are set forth in the following description, which is provided to aid a more general understanding of the invention. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention proposes an apparatus and a method thereof in which a transmitter receives and efficiently uses feedback information determined according to spatial correlation from a receiver in a system using multiple transmit / receive antennas.

In a system using a multiple transmit / receive antenna of the present invention, a receiver selects a weight set that maximizes a data rate and weights in the set from among a plurality of predetermined weight sets, and transmits the selected information to a transmitter through a reverse link feedback channel. To pass. The transmitter configures a precoding matrix by using the information transmitted through the feedback channel from the receiver. The information may include an index of the weight set, weight vector information that is information on selected weights in the set, and channel state information for each sub data stream. In the present invention, information including the index of the weight set, weight vector information, and channel state information for each sub data stream is defined as feedback information. As described above, the technique proposed by the present invention will be referred to as Knockdown Precoding technique.

In the following description, a system and a method of generating feedback information according to the present invention will be described.

1) Knockdown Precoding System

개의 안테나가 배열된 송신 배열안테나가 있고 수신기에

개의 안테나가 배열된 수신 배열안테나가 있는 다중 송/수신 안테나 시스템을 가정한다. 상기 송신기와 수신기는 다수의 가중치 집합을 미리 결정하고 약속한다. 상기 가중치 집합은 송신 안테나 수만큼의 가중치 벡터들을 원소로 하는 집합으로, N개의 가중치 집합을 결정하면, 총

개의 가중치 벡터들을 결정하게 된다.In the present invention, the transmitter

Antenna with two antennas arranged on the receiver

Assume a multiple transmit / receive antenna system with a receive array antenna in which two antennas are arranged. The transmitter and receiver predetermine and promise a plurality of weight sets. The weight set is a set of elements having weight vectors equal to the number of transmit antennas.

The weight vectors are determined.

The knockdown precoding technique selects one weight set that maximizes the data rate among the predefined N weight sets and weights in the set, and indexes of the weight set selected through the feedback channel, which is the reverse link, and selected weights in the set. The weight vector information is transmitted to the transmitter, and the transmitter constructs a precoding matrix using the feedback information.

1 is a diagram illustrating a system according to an exemplary embodiment of the present invention. In this embodiment, for convenience of description, the case where the number of antennas of the transmitter and the receiver is two is shown.

 Referring to FIG. 1, in the system 100 of the present invention, the receiver 130 is functionally greatly downlink channel estimator 133, demodulator 131, weight selector 135, sub-channel state estimator 137, It consists of a multiplexer 139. The transmitter 110 includes a controller 111, a demultiplexer 113, a channel encoder and a modulator 115 and 1133, and beam beamers 119 and 121.

The downlink channel estimator 133 estimates a file channel using a pilot channel of a received signal transmitted from the transmitter 110 and transmits estimation information to a weight selector. The weight selector 135 generates a weight set configured according to the number of antennas and a weight vector in each set based on the estimated information, and transmits the weight set index 151 and the weight vector information 153, which are respective information, to the transmitter ( 110). At the same time, the information is transmitted to the sub-channel state estimator 137. The sub-channel state estimator 137 estimates the channel-specific state for the weight set selected according to the received information and transmits the channel-specific state information to the transmitter 110.

The controller 111 of the transmitter 110 receives the feedback information 150 transmitted from the receiver 130. The controller 111 controls the demultiplexer 113, the channel encoders 115 and 117, and the beam formers 119 and 121 using the feedback information 150. In detail, the controller 111 determines the final number of sub data streams using the feedback information 150 and informs the demultiplexer 113 of this. The code rate and modulation scheme of each sub data stream are determined based on the channel state information 155 of the sub data streams of the feedback information 150, and are informed to the channel encoder and the modulators 115 and 117. In addition, the weight to be applied to each sub data stream during beam shaping is calculated using the weight set index 151 of the feedback information 150 or the weight vector information 153 selected from the weight set, and the beam forming machines 119 and 121 are used. ).

The demultiplexer 113 demultiplexes the main data stream according to the number of sub data streams transmitted from the controller 111. Each of the channel encoders and modulators 119 and 117 independently encodes and modulates the demultiplexed sub data stream using the coding rate and the modulation scheme received from the controller 111. The beamformers 119 and 121 multiply each sub data string received from the channel encoder and the modulators 115 and 117 by a predetermined weight. Then, the transmitter 110 transmits the data through the transmission antenna 123 by summing each sub data string.

Next, the data transmission method for each transceiver in the system of the present invention will be described in detail with reference to FIGS. 2 and 3.

2 is a flowchart illustrating a data transmission / reception method performed by the receiver 130 of the system of FIG. 1.

Referring to FIG. 2, first, the downlink channel estimator 133 of the receiver 130 estimates a downlink fading channel using pilot channels or pilot symbols received from a plurality of reception antennas 139 in step 201. do. That is, the fading channel for the downlink from each transmitting antenna to each receiving antenna is estimated. In operation 203, the weight selector 135 selects weight information for maximizing a data rate based on the estimated fading channel information. Here, the weight information means the weight set index 151 and the weight vector information 153.

The step 203 will be described in detail. For each of the N weight sets, weight vectors for maximizing a data rate in each weight set are selected, and a data rate transmittable by the selected weight vectors is calculated. That is, the weight set having the maximum data rate is determined by comparing the transmittable data rates by N selected weight sets (weight sets having weight vectors selected from each weight set as elements). The index of the weight set to which the weight set having the maximum transmission rate belongs is determined, and the weight vectors belonging to the weight set having the maximum transmission rate are determined as the weights to be used for the actual transmission.

 In step 205, the sub-channel state estimator 137 estimates a channel for each sub data stream based on the weight information. That is, the signal-to-interference noise ratio (SINR) of the sub data streams formed by the weights selected by the weight selector 135 is calculated to calculate channel state information for each sub data stream or MCS (Modulation and Coding Selection). Is determined. In step 207, the receiver 130 transmits feedback information 150 including the weight information and channel state information to the transmitter. In this case, the receiver may transmit the channel state information together with the weight information or may use another channel.

3 is a flowchart illustrating a data transmission / reception method performed by the transmitter 110 of the system of FIG. 1.

Referring to FIG. 3, the controller 111 of the transmitter 110 receives the feedback information 150 from the receiver 130 in step 301. Thereafter, the controller 111 determines the final number of sub data streams that can be transmitted using the weight information of the feedback information 150 in step 303. In this case, the number of sub data streams that can be transmitted is equal to the number of selected weights.

In operation 305, the demultiplexer 113 demultiplexes the main data stream to be transmitted into as many sub data streams as the number of sub data streams to be transmitted. Each channel encoder and modulators 115 and 117 encode respective sub data streams independently of each other according to a coding rate and a modulation scheme determined from channel state information for each sub data stream fed back in step 307, and apply a symbol to a symbol according to a modulation scheme. Map it. Thereafter, the beam formers 113 and 121 multiply each sub data stream by the weight transferred from the controller 111 and transmit the multipliers by the transmission antenna 123 in step 309.

비트(bit) 이다. 여기서,

는 x보다 크거나 같은 최소 정수를 의미한다.In the embodiment of the present invention, in order to feed back a precoder composed of weights maximizing the data rate to the transmitter 110 in the process of obtaining the weight set and the weight vector in the set, the selected weight set index 151 and A feedback channel is required that delivers weight vector information 153 for the selected weights in the selected weight set. The N weight sets are designed by Equation 1 to be described later, and the N weight sets are allocated to a feedback channel for feeding back the index 153 of the selected weight set if the transmitters and receivers in the cell are promised. Number of bits

Bit. here,

Is the minimum integer greater than or equal to x.

bit/use 가 된다. 또한 상기 부 채널 별 상태 추정기(137)에서 추정하여 선택된 가중치들에 의해 형성되는 부 데이터 스트림 별 채널 상태 정보를 피드백하기 위한 패드백 채널이 추가적으로 필요하다.In order to represent the selected weights in one set of weights, when using a method indicating whether the weights belonging to the selected set of weights are selected or not selected by weight, 1 bit feedback information for each weight is required. As many feedback bits as the number of transmit antennas are required. Therefore, the amount of feedback information required to feed back the precoder is total.

bit / use. In addition, a padback channel is additionally required for feeding back channel state information for each sub data stream formed by the weights estimated by the sub channel state estimator 137.

Next, a method of designing a weight set according to the present invention will be described.

2) Weight Set Design for Knockdown Precoding Technique

만큼의 가중치 벡터들을 원소로 하는 집합이다. 상기 가중치 벡터는 간단히 가중치라고도 명명한다. 여기서 하나의 가중치 벡터는

개의 복소수 원소들로 구성된다. 따라서 N개의 가중치 집합을 정의하면, 총

개의 가중치 벡터들을 구성하게 된다. N개의 가중치 집합을 설계하는데 있어 공간 상관도를 고려하기 위해 다음의 두 가지 원칙을 갖는다. 첫째, 한 가중치 집합에 속하는

개의 가중치들은 서로 직교하고, 각 가중치의 크기는 1 이다. The transmitter 110 and the receiver 130 predetermine and promise a plurality of weight sets. Weight set is the number of transmit antennas

Is a set of weight vectors. The weight vector is also simply referred to as weight. Where one weight vector

Consists of two complex elements. Therefore, if you define a set of N weights,

Will be composed of weight vectors. In designing the N weight sets, the following two principles are used to consider the spatial correlation. First, belonging to one set of weights

The weights are orthogonal to each other, and the size of each weight is 1.

개의 가중치 벡터들에 의해 형성되는 빔들의 주 빔 방향이 서로 겹치지 않고, 서비스 영역 내에서 균일하게 나누어 져야 한다.Second, the gun determined

The main beam directions of the beams formed by the two weight vectors do not overlap each other and must be divided evenly within the service area.

의 정수배인 총

개의 가중치 벡터들을 만들고, 이 가중치 벡터들 중에 가중치 벡터의 동일 위치 원소들간 위상차가

의 정수 배 만큼 차이가 나는

개의 가중치들을 하나의 가중치 집합으로 그룹핑(Grouping)하면, 동일 가중치 집합에 속하는

개의 가중치들이 서로 직교하는 총 N개의 가중치 집합이 결정된다.In order to determine a total of N weight sets satisfying the first and second principles, the phase difference between neighboring elements of each weight vector

The integer multiple of

Are weighted vectors, and among the weighted vectors, the phase difference

Difference by an integer multiple of

Grouping the weights into one set of weights,

A total set of N weights in which the weights are orthogonal to each other is determined.

4 is a diagram illustrating an example of a process of determining a total of N weight sets.

개의 가중치 벡터를 만드는 과정이다. 우선 가중치 집합의 개수 N과 송신 안테나의 개수

를 입력 받는다.

개의 가중치 벡터를 구하기 위해 k= 0부터 k =

까지 과정 401~405의 순환 과정을 거친다. 402 과정에서 k번째 가중치 벡터를 구하기 위한 가중치 벡터 내의 이웃 원소간 위상차

를 계산한다. 여기서 계산된 위상차를 가지고 403 과정에서 k번째 가중치 벡터를 결정한다. K번째 가중치 벡터의 첫번째 원소는 항상

이고, 두번째 원소는

를 위상으로 갖는

즉

이다, 세번째 원소는 두번째 원소에서

만큼 위상을 증가시킨

즉

이다. 이와 같은 방법으로

개의 원소를 모두 채우면 k번째 가중치 벡터가 완성된다. k번째 가중치 벡터를 결정한 후에는 404 과정에서 k를 하나 증가시키고 402와 403 과정을 반복하여 (k+1)번째 가중치 벡터를 결정한다.

개의 가중치 벡터를 모두 결정(과정 406)하고 난 뒤에는 과정 407에서 이들 중 직교(Orthonormal)한 가중치 벡터만 모아서 가중치 집합으로 분류한다. 분류하는 기준은 가중치 벡터들 중에 가중치 벡터의 동일 위치 원소들간 위상차가

의 정수 배 만큼 차이가 나는

개의 가중치들을 하나의 가중치 집합으로 모으는 것이다. 이 기준을 만족하도록 가중치 집합을 분류하면 가중치 집합 1은

번째 가중치 벡터들로 구성되고 가중치 집합 2는

번째 가중치 벡터들로 구성된다. 일반적으로 표현하면 가중치 집합 n+1은

번째 가중치 벡터들로 구성된다.4, the process 400

This process creates weight vectors. First, the number N of weight sets and the number of transmit antennas

Get input.

To find the weight vectors of k from 0 to k =

Until the cycle of the process 401 ~ 405. Phase difference between neighboring elements in the weight vector to obtain the k th weight vector in step 402.

Calculate The k-th weight vector is determined in step 403 using the calculated phase difference. The first element of the Kth weight vector is always

And the second element is

With phase

In other words

The third element is the second element

Increased phase by

In other words

to be. In this way

When all elements are filled, the k th weight vector is completed. After determining the k th weight vector, k is increased by one in step 404, and steps 402 and 403 are repeated to determine the (k + 1) th weight vector.

After all of the weight vectors have been determined (step 406), only orthonormal weight vectors are collected and classified into weight sets in step 407. The criterion to classify is that the phase difference between the same position elements

Difference by an integer multiple of

It is to collect the weights into a set of weights. If we classify the set of weights to satisfy this criterion, weight set 1

The second weight vectors and weight set 2

Second weight vectors. In general terms, the weight set n + 1

Second weight vectors.

을 설계하면, 각 가중치 집합

은 직교(Orthonormal)한

개의 가중치 벡터

들을 원소로 하는 집합이다. 즉,

이다. 여기서,

는 N번째 가중치 집합,

에 속하는 i번째 가중치 벡터를 나타내며 다음 <수학식 1>과 같이 설계된다.A concrete example of the design based on the above-described weight set design principle is expressed as an equation. N weight set

If you design, each set of weights

Is orthonormal

Weights vector

Is a collection whose elements are elements. In other words,

to be. here,

Is the Nth set of weights,

It represents the i-th weight vector belonging to and is designed as shown in Equation 1 below.

는 다음의 <수학식 2>과 같다.here

Is shown in Equation 2 below.

는 N번째 가중치 집합,

에 속하는 i번째 가중치 벡터의 기준 위상을 나타낸다.here

Is the Nth set of weights,

It represents the reference phase of the i-th weight vector belonging to.

FIG. 5 is a flowchart illustrating another example of determining a weight set according to the present invention, and illustrates a process of determining a total of N weight sets according to Equation 1. FIG. First, the weight set number n is initialized to 1 in step 500. In step 501, the n th weight set is calculated, and immediately after 500, the first weight set is calculated. In step 502, n is increased by one, and the process of 501 is repeated until a total of N weight sets are completed. When all weight sets are completed, the process is completed in step 504.

개의 가중치 벡터를 계산하는 과정으로 구성되어 있다. 510 과정에서는 n번째 가중치 집합에 대해서 가중치 벡터 번호 i를 1로 초기화 한다. 511 과정에서는 n번째 가중치 집합 내의 i번째 가중치 벡터를 결정한다. 즉 510 과정 직후에는 n번째 가중치 집합 내의 첫번째 가중치 벡터를 계산하게 된다. 512 과정에서 i를 하나씩 증가시켜서 n번째 가중치 집합 내 총

개의 가중치 벡터가 완성될 때까지 511의 과정을 반복하게 된다. n번째 가중치 집합 내 모든 가중치 벡터가 결정되면 514 과정에서 n번째 가중치 집합 결정을 완료하고 다음 가중치 집합 결정 과정을 거치게 된다. Step 501 is within the nth set of weights

It is composed of the process of calculating the weight vector. In step 510, the weight vector number i is initialized to 1 for the n th weight set. In operation 511, an i th weight vector in the n th weight set is determined. That is, immediately after step 510, the first weight vector in the n th weight set is calculated. In step 512, increase i by one,

The process of 511 is repeated until two weight vectors are completed. When all weight vectors in the n th weight set are determined, the n th weight set determination is completed in step 514 and the next weight set determination process is performed.

을 결정한다. 기준 위상이 결정되면 이 값을 가지고 n 번째 가중치 집합 내의 i번째 가중치 벡터의 각 원소를 계산한다. 521 과정에서는 우선 원소 번호 m을 1로 초기화한다. 522 과정에서는 n번째 가중치 집합 내의 i번째 가중치 벡터의 m번째 원소를 520 과정에서 구한 기준 위상

를

에 적용하여 결정한다. 즉 521 과정 직후에는 n번째 가중치 집합 내의 i번째 가중치 벡터의 첫번째 원소를 계산하게 된다. 이와 같은 과정을 m=1부터

까지 반복하면 525 과정에서 n번째 가중치 집합 내의 i번째 가중치 벡터를 완성하게 되고 다음 가중치 벡터를 결정하는 과정을 거치게 된다.Step 511 consists of calculating the i th weight vector in the n th weight set. In step 520, the reference phase for calculating the i th weight vector in the n th weight set

Determine. Once the reference phase is determined, each element of the i th weight vector in the n th weight set is calculated using this value. In step 521, the element number m is first initialized to 1. In step 522, the reference phase obtained by obtaining the m th element of the i th weight vector in the n th weight set in step 520

To

Determined by applying. That is, immediately after step 521, the first element of the i th weight vector in the n th weight set is calculated. This process starts from m = 1

Repeating to complete the i th weight vector in the n th weight set in step 525 and go through the process of determining the next weight vector.

In the multiple transmit / receive antenna system using four transmit antennas, two weight sets are designed as shown in Equation 3 below.

에 속한 4개의 가중치들은 서로 직교하며, 크기가 1이다. 또한

에 속한 4개의 가중치들도 서로 직교하며, 크기가 1이다. 그러나, 다른 가중치 집합에 속하는

와

가중치들은 서로 직교하지 않는다. 서로 직교하는 가중치들에 의해 데이터 스트림들이 전송될 때, 동시에 전송되는 데이터 스트림 들간의 간섭이 최소화되어, 동시에 전송되는 데이터 스트림들에 의한 전송률 합이 최대화 될 수 있다. 본 발명에서 제안하는 knockdown precoding 기술은, 한 가중치 집합에 속하는 가중치들이 서로 직교하도록 설계하고, 동시에 전송되는 데이터 스트림들이 한 가중치 집합에서 선택된 가 중치들에 의해 전송되게 함으로써, 동시에 전송되는 데이터 스트림들 간 간섭을 줄여, 동시에 전송되는 데이터 스트림들에 의한 전송률 합이 최대화 되도록 한다. 또한,

과

에 속하는 8개의 가중치들에 의해 형성되는 주 빔(main lobe)들의 방향이 서로 겹치지 않고, 서비스 영역 내에서 균일하게 나누어진다. 이는 송신기의 서비스 영역 내에서 랜덤하게 분포하는 수신기들이 어떠한 방향에 위치하더라도, 8개의 송신 가중치들 중에 하나 혹은 다수개의 가중치들에 의한 빔 성형 이득을 갖도록 한다. Of Equation 2

The four weights belonging to are orthogonal to each other and have a size of 1. Also

The four weights belonging to are also orthogonal to each other and have a size of 1. However, belonging to a different set of weights

Wow

The weights are not orthogonal to each other. When data streams are transmitted by weights orthogonal to each other, interference between data streams transmitted at the same time may be minimized, and the sum of transmission rates by data streams transmitted at the same time may be maximized. The knockdown precoding technique proposed by the present invention is designed such that weights belonging to one set of weights are orthogonal to each other, and data streams transmitted simultaneously are transmitted by weights selected from one set of weights. The interference is reduced so that the sum of the rates by the data streams transmitted simultaneously is maximized. Also,

and

The directions of the main lobes formed by the eight weights belonging to do not overlap each other, and are evenly divided within the service area. This allows a randomly distributed receiver in the transmitter's service area to have a beam shaping gain by one or more of the eight weights, regardless of which direction it is located.

개의 가중치들 중에서, 동시 전송되는 부 데이터 스트림들에 의한 전송률 합이 최대가 되도록 가중치들을 선택하게 되면, 선택된 가중치들이 동일한 가중치 집합에 속할 확률이 높기 때문에, 한 가중치 집합을 선택하고 해당 가중치 집합에서 선택된 가중치들을 나타내는 계층적인 표현 방식을 사용하면, 데이터 전송률을 최대로 하는 선택된 가중치들을 표현하기 위한 피드백 정보량을 최소화 할 수 있다.gun

Among the weights, if the weights are selected such that the sum of the rates by the concurrently transmitted sub data streams is maximized, the weights are more likely to belong to the same weight set. By using a hierarchical representation method representing weights, it is possible to minimize the amount of feedback information for representing selected weights that maximize the data rate.

), 가중치 집합 개수(N)에 대해 상기 <수학식 1>을 만족하는 경우에 대한 일례를 다음의 <표 1> 내지 <표 12>에 나타내었다. 하기 표에서 (x,y)는 실수 성분이 x, 허수 성분이 y인 복소수를 표기한 것이다. 즉 (x,y)= x + yi를 의미한다. Then, in the system of the present invention,

) And an example of a case in which Equation 1 is satisfied with respect to the number N of weight sets is shown in Tables 1 to 12 below. In the following table, (x, y) denotes a complex number whose real component is x and its imaginary component is y. That means (x, y) = x + yi.

3) Structure and Operation Method of Feedback Channel for Knockdown Precoding Technology

In FIG. 1, feedback information 150 for supporting the knockdown precoding technique is defined as a selected weight set index 151, a selected weight vector information 153, and state information 155 for each sub data stream. The amount of state information 155 for each sub data stream that is actually required varies depending on how many weight vectors are selected, that is, how many sub data streams are actually transmitted. For example, if only one weight vector is selected, one sub data string will be transmitted, and the sub data column state information fed back becomes the state information of one sub data string to be transmitted. As another example, if two weight vectors are selected, the state information of two sub data streams should be fed back. In order to effectively reduce the load on the feedback channel, a function for adaptively controlling the amount of resources consumed when feeding back state information for each sub data stream is needed according to the number of weight vectors selected.

Let cqi [k] be the CQI of the secondary data stream transmission channel configured through the k th weight vector in one weight set. If the weight vector is not selected, cqi corresponding to the weight vector is set to NULL. Rearrange the state information cqi [k] for each sub data stream so that the CQI set to NULL goes backward. For example, assume that n _T (number of transmit antennas of the transmitter) is 4, the second and third weight vectors are selected, and the first and fourth weight vectors are not selected. Then cqi [1] and cqi [4] will be set to NULL and cqi [2] and cqi [3] will be set to valid values. When CQI is rearranged as CQI (m), CQI (1) = cqi [2], CQI (2) = cqi [3], and CQI (3) = NULL CQI (4) = NULL.

6 illustrates a process of rearranging CQIs according to the weight vectors selected as described above. Referring to FIG. 6, in step 600, k for ordering the weight vectors and m for ordering the CQIs having been rearranged are initialized to '1'. If it is selected by determining whether the k th weight vector is selected in step 602, the value of cqi [k] is filled as in step 606. Then, in step 608, the cqi [k] value is filled in CQI (m), and in step 608, m is increased by one. On the other hand, if the k th weight vector is not selected, cqi [k] is filled with NULL in step 610. In step 612, k is increased by one, and in step 614, it is determined whether k is not greater than nT (transmission antenna). If not, the flow proceeds to step 602 and repeats steps 602 to 612 again. On the other hand, if it is determined in step 614 that k is not greater than nT (transmission antenna), the process proceeds to step 616 to fill CQI (m) with NULL and increases m by one in step 618. In step 620, it is determined whether m is not greater than nT, and if it is not large, steps 616 to 618 are repeated to fill all remaining CQIs with NULL and ends if large.

The process of FIG. 6 describes an algorithm for filling both cqi [k] and CQI (m), but the process of inputting cqi [k] can be omitted since the actual transmission is only CQI (m). Through this process, valid values are set from CQI (1) to CQI (nS), and NULL is inserted into the other CQI.

Status information for each sub data stream in which CQI is set to NULL are values that do not need to be fed back. The present embodiment provides a method for reducing the load caused by CQI feedback set to NULL when the feedback channel is a code division multiple access (CDMA) system. Suppose that the feedback channel is composed of a weighted feedback channel for transmitting a weighted set index and a channel state feedback channel for transmitting state information for each sub data stream of the weighted vector included in the weighted set index. When the transmitter 110 receives only the weighted feedback channel, the transmitter 110 may determine how many weight vectors are actually used for transmission, and thus may determine the amount of state information for each sub data stream. That is, the CQI information set to NULL by the unused weight vector may already be known by the transmitter 110 only receiving the weighted feedback channel. Therefore, the transmitter 110 does not have to perform a process of receiving the CQI feedback information of this NULL. In a CDMA system, interference determines the capacity of the entire system. In other words, reducing the amount of useless interference can increase the capacity.

To reduce interference, do not use more power than necessary to transmit. Since the CQI feedback information of NULL is not information to be received, the transmission power of the channel state feedback channel including NULL can be reduced. For example, if only the CQI (1) is set to a valid value and the remaining CQIs are set to NULL, the transmitter 110 can show the same feedback information reception performance even when using less transmit power than when all CQIs are set to a valid value. have. This is because the detection threshold can be lowered based on the fact that NULL is already set in the process of receiving the feedback channel. Lower detection criteria mean that it can be received at lower power. Therefore, according to the number of weight vectors selected, the higher the number, the lower the power. When users transmit a feedback signal with less power, interference is less, allowing more users to send a feedback signal on the same radio resource.

FIG. 7 illustrates a process in which the transmitter 110 receives a CQI based on the number of selected weight vectors and corresponds the value to the selected weight vector. Referring to FIG. 7, in step 700, a transmitter receives a selected weight set and vector information transmitted through a weight feedback channel. Based on this information, the number of weight vectors selected is determined. In operation 602, detection criteria are selected according to the number of selected weight vectors. The larger the number of weight vectors, the higher the detection criterion, and the smaller the weight vector, the lower the detection criterion. In step 604, the sub-channel data string state information transmitted through the channel state feedback channel is received. Here, the number of subchannel data string state information, that is, CQI, to be received is equal to the number of selected weight vectors. In the reception process of 604, the detection criteria determined in step 602 is used. Next, the subchannel data string state information obtained in operation 606 is mapped to the actually selected weight vector. In step 606, the CQI rearranged through the process described with reference to FIG. 6 is returned to its original state.

For example, nT is 4, the second and third weight vectors are selected, and the first and fourth weight vectors are not selected. Then, since two weight vectors have been selected, CQI (1) and CQI (2) are received. Since the transmitter 110 knows that the second and third weight vectors are selected, it can be seen that CQI (1) is the state of the channel constituted by the second weight vector and CQI (2) is the state of the channel constituted by the third weight vector. . In order to clarify the order, the order of the received CQI and the order of the selected weight vector must be equally matched.

In a transmission method in which one weight vector does not form a channel for transmitting one sub data string, but the selected weight vector is mixed for each symbol, and one sub data string is divided into virtual beams formed by the selected weight vectors. The information does not correspond to the weight vector but corresponds to the order of demodulation and decoding. For example, suppose two weight vectors are selected. Two sub data streams are transmitted through two virtual beams composed of these two weight vectors. The first demodulated / decoded sub data string can not only experience interference of other sub data strings, but the second demodulated / decoded sub data string can eliminate the interference of the first demodulated / decoded sub data string. Therefore, the two sub data strings experience different CQIs. In this case, the CQI (1) corresponds to the secondary data string first demodulated / decoded, and the CQI (2) corresponds to the secondary data stream demodulated / decoded second.

In the above description, it is described for convenience that the channel state information of the sub data string not actually transmitted is set to NULL, but may be set to any predetermined valid value. This channel state information is because the transmitter does not actually attempt to receive. Whether set to NULL or a useful value, the value set as channel state information of a sub data string that is not transmitted should be set to a value previously promised by the transmitter and the receiver. Otherwise, the detection criterion cannot be lowered in the process of receiving the channel state information of the secondary data string transmitted by the transmitter.

4) Using Knockdown precoder in SCW MIMO

Single Code Word (SCW) MIMO is a technology that transmits MIMO through a single encoding and modulation. Referring to the example of FIG. 1, the respective channel encoders and modulators 115 and 117 are connected to the beam formers 119 and 121. Each encoder and modulator receives state information 155 for each sub data stream and performs individual operations. However, since only one encoder and modulator are used in SCW MIMO, no state information for each data stream is needed, and only one representative state information is needed. SCW MIMO does not perform adaptive modulation and coding for each beam, but performs a function of selecting and transmitting only a preferred beam. Therefore, when column vectors are selected by the knockdown precoding method, one data string is transmitted through a plurality of beams configured by the vectors.

In the conventional SCW MIMO, SCW MIMO is performed by receiving a rank indicating how many layers to activate and a representative channel state information CQI. However, using the knockdown precoder eliminates the need for a feedback channel reserved for rank. Therefore, setting this part to a value previously defined by the transmitter and the receiver can lower the detection criteria and effectively reduce the feedback signal transmission power.

Comparative analysis of the proposed technology and the prior art

The method of controlling the number of data streams simultaneously transmitting the prior art Precoder Codebook technology and the proposed technology Knockdown Precoding technology is compared and analyzed in terms of the amount of feedback information required for this.

, 수신 안테나 수

, 그리고 동시에 전송되는 데이터 스트림 수

에 따라 프리코더 코드북을 따로 정의하여 사용한다. 만약, 송신 안테나 수가 4인 송신기와 수신 안테나 수가 1, 2, 3, 그리고 4인 수신기들이 동일 셀 내에서 통신을 하는 상황에서, 각 송수신기 채널 상황에 따라 동시에 전송되는 데이터 스트림 수를 조절할 경우, 고려되어야 할 프리코더 코드북들은

=(4,1,1), (4,2,1), (4,2,2), (4,3,1), (4,3,2), (4,3,3), (4,4,1), (4,4,2), (4,4,3), 그리고 (4,4,4)로 총 10가지 이다. 송신기와 수신기들은 위의 10가지의 프리코더 코드북들을 미리 약속한다. 수신기는 수신안테나 수

과 전송하는 데이터 스트림 수

을 송신기로 피드백하여, 송신기가 사용할 프리코더 코드북을 선택하도록 한다. 수신기는 추정된 하향 링크 채널 정보를 이용하여, 수신안테나 수

과 전송하는 데이터 스트림 수

에 적합한 프리코더 코드북 중에 최대 용량을 전송하는 프리코더(precoder)를 선택하고, 선택된 프리코더(precoder)의 인덱스를 송신기로 피드백한다. 송신기는 피드백된

과

에 적합한 프리코더 코드북중에서 피드백된 인덱스를 갖는 프리코더를 선택하여 데이터를 전송한다. The prior art coder codebook technique has a number of transmit antennas.

Receiving antennas

, And the number of data streams sent simultaneously

Precoder codebook is defined and used separately. If the transmitters having 4 transmit antennas and the receivers having 1, 2, 3 and 4 antennas communicate in the same cell, consider the case of adjusting the number of simultaneously transmitted data streams according to the conditions of each transceiver channel. The precoder codebooks that should be

= (4,1,1), (4,2,1), (4,2,2), (4,3,1), (4,3,2), (4,3,3), ( 4,4,1), (4,4,2), (4,4,3), and (4,4,4) in total. The transmitter and receiver promise in advance the above 10 precoder codebooks. Receiver can receive antenna

And the number of data streams sent

Is fed back to the transmitter to allow the transmitter to select a precoder codebook to use. The receiver uses the estimated downlink channel information to determine the number of reception antennas.

And the number of data streams sent

The precoder which transmits the maximum capacity is selected from among the precoder codebooks which are suitable for. The feedback of the selected precoder is fed back to the transmitter. The transmitter is fed back

and

The precoder having the index fed back is selected from among the precoder codebook suitable for the data transmission.

에 대한 피드백은 미미하기 때문에 무시할 수 있으나, 채널 상황에 따라 순시적으로 변하는

에 대한 피드백은 선택된 프리코더의 인덱스에 대한 피드백 정보와 같이 송신기로 전송되어야 한다. 따라서, 각 프리코더 코드북들이 8개의 프리코더들로 구성되어 있다고 가정한다면,

를 피드백하기 위한 2bits/use 피드백 정보와 선택된 프리코더의 인덱스를 피드백하기 위한3bits/use의 피드백 정보가 필요하므로, 총 5 bits/use의 피드백 정보가 필요하다.The amount of feedback information required is sufficient for one-time feedback.

Feedback on is negligible and can be ignored, but it changes instantaneously depending on channel conditions.

The feedback on the P-subframe must be transmitted to the transmitter together with the feedback information on the index of the selected precoder. Thus, assuming that each precoder codebook consists of eight precoders,

Since 2bits / use feedback information for feeding back and 3bits / use feedback information for feeding back the index of the selected precoder are needed, a total of 5 bits / use feedback information is required.

와 선택된 피드백의 인덱스를 피드백 하기 위한 피드백 정보뿐 아니라 추가적으로 하향 링크 채널의 공간 상관 행렬을 피드백 하기 위한 피드백 정보량이 요구된다.The optimal precoder codebook depends on the fading spatial correlation of the channel being operated. Until now, the conventional precoder codebook technology has designed the precoder codebook on the assumption that there is no spatial correlation of fading. Therefore, performance degradation occurs in a channel environment in which spatial correlation of fading exists. In order to overcome this problem, the transmitter needs to transform the existing precoder codebook using the spatial correlation matrix of the downlink channel. To this end, since the receiver estimates the spatial correlation matrix of the downlink channel and feeds it back to the transmitter,

In addition to the feedback information for feeding back the index of the selected feedback, an amount of feedback information for feeding back the spatial correlation matrix of the downlink channel is required.

만큼의 직교하는 가중치들로 이루어진 N개의 가중치 집합을 약속한다. 수신기는 사용하고 있는 수신 안테나 수

을 고려하여, 전송 데이터 율을 최대로 하는 최대

개의 가중치들을 선택한다. 수신기는 선택된 가중치 집합 인덱스와 해당 집합에서의 가중치 선택 정보에 대한 피드백을 통해 선택된 가중치들을 송신기로 피드백 한다. 송신기는 피드백 정보를 바탕으로 선택된 가중치 집합에서 선택된 가중치들을 이용하여 다중 데이터 스트림들을 전송한다. 수신기들의 수신 안테나가 다양하고, 동시에 전송되는 데이터 스트림 수가 다양하더라도 총

개의 가중치들로 이루어진 N개의 가중치 집합을 공통적으로 사용하기 때문에 송신기와 수신기들 사이에서 약속되어야 할 가중치 집합에 대한 정보량이, 프리코더 코드북 기법에서 요구되는 정보량에 비하여 상당히 적다. 특히, 송신 안테나 수가 4개를 초과하는 경우, 고려해야 할 프리코더 코드북 수가 상당히 증가하기 때문에, 송수신기가 약속해야 할 프리코더 코드북들에 대한 정보량이 상당히 증가하게 된다. 이에 반해 제안하는 Knockdown Precoding 기법은 송신 안테나 수

가 증가하더라도 오히려 필요한 가중치 집합 수 N은 감소하게 되어 송신기와 수신기들 사이에서 약속되어야 할 가중치 집합에 대한 정보량이 거의 증가하지 않는다. 이는 Knockdown Precoding 기술의 성능이 총 가중치 수

에 의해 결정되기 때문이다.In the knockdown precoding technique proposed by the present invention, the number of transmit antennas

Promises a set of N weights of orthogonal weights. The receiver is using the number of receiving antennas

Taking into account, the maximum that maximizes the transmission data rate

Select weights. The receiver feeds back the selected weights to the transmitter through feedback on the selected weight set index and the weight selection information in the set. The transmitter transmits the multiple data streams using the weights selected from the weight set selected based on the feedback information. Although the receivers of the receivers vary and the number of data streams transmitted simultaneously varies,

Since a common use of N weight sets consisting of two weights is, the amount of information on the weight set to be promised between the transmitter and the receiver is considerably less than the amount of information required by the precoder codebook technique. In particular, if the number of transmit antennas exceeds four, since the number of precoder codebooks to consider considerably increases, the amount of information on the precoder codebooks that the transceiver should promise is significantly increased. On the other hand, the proposed knockdown precoding scheme is based on the number of transmit antennas.

Rather, the number N of weight sets required decreases so that the amount of information on the weight sets to be promised between the transmitter and the receiver hardly increases. This is the total weight of the performance of the Knockdown Precoding technique

Is determined by.

bits/use가 필요하고, 가중치 선택 정보를 피드백 하기 위해서

bits/use가 필요하여, 총

bits/use가 필요하다. 송신 안테나 수가 4이고, N=2인 경우 총 5bits/use가 필요하다. 가중치 선택 정보 피드백을 위한 전용 피드백(Dedicated Feedback) 채널을 사용하는 Open Loop Knockdown Precoding 기술에서 요구되는 피드백 정보량은, 단지 가중치 선택 정보를 피드백 하기 위한

bits/use가 필요하다. 또한 가중치 선택 정보에 필요한 피드백 정보량을 줄이기 위해서, 부 데이터 스트림 별 채널 상태 정보를 전송하는 피드백 채널을 이용하여 가중치 선택 정보를 피드백 하는 방식을 사용할 수 있다.The amount of feedback information required in the closed loop knockdown precoding technique using a dedicated feedback channel for feedback of the weight selection information feeds back the selected weight set index.

bits / use are required to feed back the weight selection information.

needs bits / use, total

bits / use are required. If the number of transmit antennas is 4 and N = 2, a total of 5 bits / use is required. The amount of feedback information required in the Open Loop Knockdown Precoding technique using a dedicated feedback channel for feedback of the weight selection information is merely for feeding back the weight selection information.

bits / use are required. In addition, in order to reduce the amount of feedback information required for the weight selection information, a method of feeding back the weight selection information by using a feedback channel for transmitting channel state information for each sub data stream may be used.

Therefore, the proposed Knockdown Precoding technique can select a feedback method that transmits weight selection information according to the reverse link channel structure of the applied system, and uses the number of weight sets used according to the capacity of the reverse link channel available in the applied system. It can be adjusted and applied. In particular, if the capacity of the reverse link channel that can be used in the system is very small, Open Loop Knockdown Precoding technology can be applied.

인 경우, 공간 상관도가 높은 환경에서 프리코더 코드북 기술과 본 발명의 knockdown precoding 기술을 적용한MMSE-OSIC(Minimum Mean Square Error - Ordered Successive Interference Cancellation) 시스템의 성능을 비교한 결과를 보여준다. Knockdown Precoding 기술은 두 개의 가중치 집합을 사용하는 경우를 고려하면, Closed loop Knockdown Precoding 기술은 가중치 집합 인덱스(index) 피드백을 위한 1bit와 4개의 가중치들의 선택 여부를 피드백 하기 위한 4bit, 총 5bit/use 의 피드백 정보가 요구된다. Open loop Knockdown Precoding 기술은 4개의 가중치들의 선택 여부를 피드백 하기 위한4bit/use 가 필요하다. 프리코더 코드북 기술은 동시에 전송할 데이터 스트림 수를 조절하기 위한 2bits와 선택된 프리코더의 인덱스를 피드백하기 위한 3bits, 총 5bits/use 의 피드백 정보량이 요구된다. 동일한 5bit/use의 피드백 정보량이 요구되는 Closed loop Knockdown Precoding 기술과 변환(Companding)을 하지 않는 프리코더 코더북 기술의 성능을 비교하면, Closed loop Knockdown Precoding 기술이 변환(Companding)을 하지 않는 프리코더 코더북 기술보다 상당히 우수함을 확인할 수 있다. 더구나, 4bit/use가 필요한 Open loop Knockdown Precoding 기술이 오히려 5bit/use가 필요한 변환(Companding)을 하지 않는 프리코더 코드북 기술보다 상당히 우수함을 알 수 있다. 다만, 변환(Companding)을 하는 프리코더 코드북 기술의 경우, Closed loop Knockdown Precoding 기술과 거의 비슷한 성능을 보이지만, 변환(Companding)을 위해 하향 링크 채널의 공간 상관 행렬에 대한 추가적인 피드백이 요구되므로, 요구되는 피드백 정보량이 Closed loop Knockdown Precoding 기술보다 상당히 많다.8 is

In the case of, the result of comparing the performance of the precoder codebook technique and the minimum mean square error-ordered successive interference cancellation (MMSE-OSIC) system to which the knockdown precoding technique of the present invention is applied in a high spatial correlation environment is shown. Considering the Knockdown Precoding technique using two weight sets, the Closed loop Knockdown Precoding technique uses 1 bit for weight set index feedback and 4 bits to feed back whether 4 weights are selected. Feedback information is required. The open loop knockdown precoding technique requires 4 bits / use to feed back the choice of four weights. Precoder codebook technology requires 2 bits for controlling the number of data streams to be transmitted at the same time and 3 bits for feedback of the selected precoder index, and a total of 5 bits / use of feedback information. Comparing the performance of the closed loop Knockdown Precoding technology, which requires the same amount of feedback information of the same 5bit / use, and the precoder coder technology that does not convert, the Precoder coder that does not convert It can be seen that it is significantly superior to book technology. In addition, it can be seen that the open loop knockdown precoding technique, which requires 4 bits / use, is rather superior to the precoder codebook technique that does not perform compiling, which requires 5 bits / use. However, the precoder codebook technique that performs the conversion shows similar performance to the closed loop knockdown precoding technique, but additional feedback on the spatial correlation matrix of the downlink channel is required for the conversion. The amount of feedback information is considerably greater than that of the closed loop knockdown precoding technique.

As shown in the experimental results, it can be seen that the knockdown precoding technique of the present invention can be applied to a channel environment having various spatial correlations and has excellent performance, compared to the conventional precoder codebook technique.

인 경우, 공간 상관도가 없는 환경에서 프리코더 코드북 기술과 제안하는 Knockdown Precoding 기술을 적용한 MMSE - OSIC 시스템의 성능을 비교한 결과를 보여준다.9 is

In the case of, we show the result of comparing the performance of MMSE-OSIC system with pre-coder codebook technology and proposed Knockdown Precoding technology in the environment without spatial correlation.

Referring to FIG. 9, in an uncorrelated environment, a precoder codebook technique that performs a conversion and a precoder codebook technique that does not perform a conversion show the same performance. This is because the transmit correlation matrix becomes an identity matrix in an uncorrelated environment, and the precoder codebook does not change even when the companding is performed. Both precoder codebook techniques perform the same as closed loop knockdown precoding and slightly better than open loop knockdown precoding. As can be seen from the performance results of FIGS. 12 and 13, the precoder codebook technique of the present invention does not show a difference in performance even in an uncorrelated environment compared to the prior art, but also in a channel environment having various spatial correlations. It can be seen that the performance is excellent.

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. That is, in the present invention, a system having two transmitting antennas and a receiving antenna is shown for convenience of description, but more antennas can be applied. 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, the knockdown precoding technique of the present invention can be applied to a channel environment having various spatial correlations compared to the conventional precoder codebook technique, and has excellent performance, thereby increasing throughput. In addition, the Knockdown Precoding technique of the present invention has a much smaller amount of memory than the precoder codebook technique, and can be optimized according to the reverse link channel structure and capacity of a system to which a spatial multiplexing technique is to be applied.

Claims (4)

A mobile communication system implementing multiple transmission using an array antenna, Estimating a fading channel of the received data to determine a weight set that maximizes a data rate among at least one weight set having a plurality of orthogonal weight vectors as elements, and includes the determined weight set and channel-specific state information. A receiver for transmitting information to the transmitter, And a transmitter for demultiplexing data to be transmitted based on the feedback information into at least one sub data string, and multiplying each demultiplexed sub data string by a corresponding weight. Wherein the channel state information is adaptively adjusted according to the number of weight vectors. The method of claim 1, wherein the receiver, A downlink channel estimator for estimating a channel state using a pilot channel of data transmitted from the transmitter; A weight selector for determining the weight set and the weight vector based on the channel state and transmitting information on the weight set and weight vector to the transmitter; And a sub-channel state estimator for estimating a channel state for each subdata according to the determined weight vector and transmitting only the channel state for each subdata to the transmitter. The method of claim 1, wherein the receiver, A downlink channel estimator for estimating a channel state using a pilot channel of data transmitted from the transmitter; A weight selector for determining the weight set and the weight vector based on the channel state and transmitting the determined weight set to the transmitter; And a state estimator for each sub-channel for estimating channel states of all weight vectors in the determined weight set and transmitting them to the transmitter. A method of transmitting / receiving data in a mobile communication system implementing multiple transmission using an array antenna, A first process of estimating a fading channel from a pilot channel of received data at a receiver; A second process of determining a weight set maximizing a data rate among at least one weight set including elements of a plurality of orthogonal weight vectors based on the estimated fading channel; Estimating state information for each channel according to the determined weight set; A fourth process of transmitting feedback information including the determined weight set and state information for each channel to the transmitter; A fifth process of transmitting, by the transmitter, data for each array antenna based on the feedback information; Wherein the channel state information is adaptively adjusted according to the number of weight vectors.

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