KR20060043799A - Apparatus and method of space time block code for increasing performance - Google Patents

Abstract

The present invention relates to a space-time block encoding apparatus in a transmitter of a communication system using a plurality of transmission antennas, and to improve performance of a space-time block code in a method of transmitting an input symbol string through a plurality of transmission antennas according to a predetermined rule. The present invention proposes an apparatus using feedback information sent from a receiver.

Space-time block coding, maximum diversity gain, maximum data rate

Description

Apparatus and method for performance-enhanced spatiotemporal block encoding {APPARATUS AND METHOD OF SPACE TIME BLOCK CODE FOR INCREASING PERFORMANCE}

1 is a diagram showing the configuration of a transmitter in a mobile communication system using a space-time block coding scheme according to the prior art.

2 is a diagram illustrating a receiver configuration in a mobile communication system using a space-time block coding scheme according to the prior art.

3 is a diagram illustrating a configuration of a transmitter in a mobile communication system using a space-time block coding scheme proposed by the prior art Giannakis group.

4 is a diagram illustrating the configuration of a transmitter in a mobile communication system using four transmission antennas proposed by the research teams Tae-Jin Chung and Jeon-Hoon Chung, and using a space-time block coding scheme.

5 is a diagram illustrating a configuration of a transmitter in a mobile communication system using a space-time block coding scheme according to the present invention.

6 is a diagram illustrating a configuration of a transmitter in a mobile communication system using a space-time frequency block coding scheme according to the present invention.

7 is a diagram illustrating a configuration of a receiver in a mobile communication system using a space-time block coding scheme according to the present invention.

8 is a flowchart illustrating an operation of a transmitter in a mobile communication system using a space-time block coding scheme according to the present invention.

9 is a flowchart illustrating an operation of a receiver in a mobile communication system using a space-time block coding scheme according to the present invention.

10 is a first example of a performance analysis curve of a mobile communication system using a space-time block coding scheme according to the present invention.

11 is a second example of a performance analysis curve of a mobile communication system using a space-time block coding scheme according to the present invention.

The present invention relates to an apparatus and method for transmitting antenna diversity in a wireless communication system. In particular, in a mobile communication system using a plurality of antennas, a method of transmitting an input symbol string through a plurality of transmitting antennas by a predetermined rule is provided. The present invention relates to a space-time block encoding apparatus and method for improving the performance of space-time block code.

The most fundamental problem in communication is how efficiently and reliably data can be transmitted over a channel. The next generation multimedia mobile communication system, which is being actively studied in recent years, needs a high-speed communication system capable of processing and transmitting a variety of information such as video and wireless data beyond the initial voice-oriented service. It is essential to increase the efficiency of the system.

In general, a wireless channel environment existing in a mobile communication system is different from a wired channel environment such as multipath interference, shadowing, propagation attenuation, time varying noise, and fading. Factors cause unavoidable errors and loss of information.

The loss of information causes severe distortion in the actual transmission signal, thereby acting as a factor that degrades the overall performance of the mobile communication system. In general, in order to reduce the loss of information, various error-control techniques are used to increase the reliability of the system according to the characteristics of the channel. The most basic of these error control techniques is an error-correcting code. correcting code.

In addition, in a wireless communication system, diversity techniques are used to mitigate multipath fading, for example, time diversity, frequency diversity, and antenna diversity.

The antenna diversity scheme uses multiple antennas, the antenna diversity scheme includes a receive antenna diversity scheme using a plurality of receive antennas, a transmit antenna diversity scheme using a plurality of transmit antennas, and It is classified into a multiple input multiple output (MIMO) scheme using a plurality of transmit antennas and a plurality of receive antennas.

Here, the MIMO scheme is a kind of space-time coding (STC) scheme, and the space-time coding scheme is transmitted in a time domain by transmitting a signal encoded by a predetermined coding scheme using a plurality of transmitting antennas. It is a method of achieving a lower error rate by extending the coding scheme to the space domain.

Meanwhile, the Space Time Block Coding (STBC) scheme, which is one of the proposed schemes for efficiently applying the antenna diversity scheme, has been proposed by "Vahid Tarokh" (Vahid Tarokh, "Space time block"). coding from orthogonal design, "IEEE Trans. on Info., Theory, Vol. 45, pp. 1456-1467, July 1999), SMAlamouti," A simple transmitter diversity scheme for wireless communication, "IEEE Journal on Selected Area in Communication, Vol. 16, pp.1451-1458, Oct.1998) The transmit antenna diversity scheme is extended to be applied to two or more transmit antennas.

1 shows a configuration of a transmitter in a mobile communication system using a space-time block coding scheme according to the prior art. This is proposed by Tarokh, as shown, modulator 100, Serial to Parallel Converter (S / P Converter) 102, Space-Time Encoder 104 and four transmit antennas. (106, 108, 110, 112).

Referring to FIG. 1, first, the modulator 100 modulates input information data (or encoded data) by using a preset modulation method and outputs modulation symbols. Herein, the preset modulation scheme is one of modulation schemes such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), pulse amplitude modulation (PAM), phase shift keying (PSK), and the like. It can be either way.

The serial / parallel converter 102 converts the serial modulation symbols from the modulator 100 into parallel modulation symbols and outputs them to the space-time block encoder 104. Here, it is assumed that the serial modulation symbols output from the modulator 100 are s _1, s _2, s _{3, and} s ₄ . The space-time block encoder 104 generates eight combinations by performing space-time block coding (STBC) on four symbols input from the serial-to-parallel converter 102, and sequentially combines the eight combinations through four transmit antennas. Send. A coding matrix for generating the eight combinations is shown in Equation 1 below.

Here, G ₄ represents an encoding matrix of symbols transmitted through four transmission antennas, and s ₁ , s ₂ , s ₃ , and s ₄ represent four input symbols to be transmitted. The number of columns in the coding matrix corresponds to the number of transmit antennas, and the number of rows represents the time required to transmit the four symbols. That is, it can be seen that four symbols are transmitted through four antennas for eight time periods.

이 송신되고, 제2송신안테나(108)를 통해서

가 송신되며, 제3송신안테나(110)를 통해서

가 송신되고, 제4송신안테나(112)를 통해서

이 송신된다. 즉, 상기 시공간 블록 부호화기(104)는 i번째 안테나로 상기 부호화 행렬의 i번째 열(column)의 심볼들을 순서대로 전달한다. That is, in the first time interval, s ₁ is transmitted through the first transmission antenna 106, s ₂ is transmitted through the second transmission antenna 108, and s ₃ is transmitted through the third transmission antenna 110. Then, s ₄ is transmitted through the fourth transmission antenna 112. In this way, in the eighth time interval, the first transmission antenna 106 is used.

Is transmitted, and via the second transmission antenna 108

Is transmitted, through the third transmission antenna (110)

Is transmitted, and via the fourth transmission antenna 112

Is sent. That is, the space-time block encoder 104 sequentially transmits the symbols of the i-th column of the coding matrix to the i-th antenna.

As described above, the space-time block encoder 104 generates eight symbol strings by applying a negative and conjugate to four input symbols, and generates eight symbol strings by eight time intervals. While transmitting over four antennas 106,108,110,112. Here, since the symbol sequences output to each antenna, that is, columns of the encoding matrix, are orthogonal to each other, diversity gains corresponding to diversity orders can be obtained. Alamouti's space-time block coding technique mentioned above, although transmitting complex symbols through two transmit antennas, does not lose data rate, but equals the number of transmit antennas, i. diversity order) has an advantage.

2 illustrates a receiver configuration in a mobile communication system using a space-time block coding scheme according to the prior art. In particular, FIG. 2 shows a receiver structure corresponding to the transmitter structure of FIG.

As shown, the receiver includes a plurality of receive antennas 200 to 202, a channel estimator 204, a signal combiner 206, a detector 208, parallel / serial It consists of a transducer 210 and a demodulator 212.

Referring to FIG. 2, first, signals transmitted through four transmitting antennas in the transmitter of FIG. 1 are received through each of the first receiving antenna 200 to the P receiving antenna 202. Each of the first receiving antenna 200 to the P receiving antenna 202 outputs the received signal to the channel estimator 204 and the signal combiner 206.

The channel estimator 204 inputs a signal received through each of the first receiving antenna 200 to the P receiving antenna 202 to estimate channel coefficients indicating channel gain. Output to detector 208 and signal combiner 206. That is, the channel estimator 204 estimates channel coefficients representing channel gains from the transmit antennas 106, 108, 110, 112 of the transmitter to the receive antennas 200-202.

The signal combiner 206 combines a signal received through each of the first receiving antenna 200 to the P receiving antenna 202 and channel coefficients output from the channel estimator 204 by a predetermined rule to receive a received symbol. Output them.

The detector 208 generates hypotheses symbols by multiplying the received symbols from the signal combiner 206 by the channel coefficients from the channel estimator 204 and generating the hypotheses symbols with the hypotheses symbols. After calculating the decision statistic for all symbols that can be transmitted by the transmitter, the detection of the symbols transmitted by the transmitter is output through the threshold detection.

The parallel / serial converter 210 converts parallel data from the detector 208 into serial data and outputs the serial data. The demodulator 212 demodulates the symbols from the parallel / serial converter 210 in a predetermined demodulation scheme to the original information data bits transmitted.

On the other hand, Tarokh's method that extends Alamouti's space-time block coding technique, as described above with reference to FIGS. 1 and 2, uses the maximum diversity order using matrix-type space-time block codes having orthogonal columns therebetween. Get However, since the Tarokh scheme transmits four complex symbols for eight time intervals, the rate is reduced to 1/2. In addition, since eight time intervals are required to completely transmit one block (four symbols), in case of fast fading, reception performance is deteriorated due to channel change in the block. In other words, in the case of transmitting complex symbols using four or more antennas, since 2N time intervals are required to transmit N symbols, there is a problem in that the latency is long and the transmission rate is lowered.

Meanwhile, in order to design a method having a maximum data rate in a multi-antenna system that transmits a complex signal through three or more transmitting antennas, the Giannakis group uses four constellation rotations in a complex field. A maximum diversity full rate (FDFR) STBC has been proposed in a transmission antenna.

3 is a block diagram of a transmitter in a mobile communication system using a space-time block coding scheme proposed by the conventional Giannakis group. As shown, the transmitter consists of a modulator 300, a precoder 302, a space-time mapper 304, and a plurality of transmit antennas 306, 308, 310, 312.

Referring to FIG. 3, first, the modulator 300 modulates input information data (or encoded data) by using a preset modulation method and outputs modulation symbols. Here, the preset modulation scheme may be any one of modulation schemes such as BPSK, QPSK, QAM, PAM, PSK scheme, and the like.

개의 변조 심볼들(d₁,d₂,d₃,d₄)을 신호 공간상에서 신호의 회전(rotation)이 발생하도록 부호화하여

개의 심볼들을 출력한다. 설명의 편의를 위하여 송신 안테나 개수가 4개인 경우에 대하여 설명하도록 한다. 여기서, 상기 변조기(300)에서 출력되는 4개의 변조 심볼들로 구성되는 심볼열을

라고 가정한다. 상기 선부호화기(302)는 상기 변조 심볼열

를 하기 <수학식 2>와 같은 연산 동작을 통해 복소 벡터(complex vector)

을 생성한다.The precoder 302 is provided from the modulator 300.

Modulation symbols d ₁ , d ₂ , d ₃ , and d ₄ are encoded such that rotation of the signal occurs in signal space.

Output symbols For convenience of description, the case of four transmitting antennas will be described. Here, the symbol string consisting of four modulation symbols output from the modulator 300

Assume that The precoder 302 stores the modulation symbol sequence.

Is a complex vector through the operation as shown in Equation 2

Create

는 선부호화 행렬을 나타내며, Giannakis 그룹에서는 상기 선부호화 행렬로 단일 행렬(unitary matrix)인 Vandermonde 행렬을 사용하고 있다. 또한, 상기 선부호화 행렬에서

는 하기 <수학식 3>과 같이 표현된다.here,

Denotes a precoding matrix, and the Giannakis group uses the Vandermonde matrix, which is a unitary matrix, as the precoding matrix. Also, in the precoding matrix

Is expressed by Equation 3 below.

As mentioned above, the space-time coding scheme proposed by the Giannakis group can be easily extended to not only four transmission antennas but also more than four transmission antennas. The space-time mapper 304 outputs the symbols from the pre-coder 302 by space-time block encoding as shown in Equation 4 below.

In Equation 4, S denotes an encoding matrix of symbols transmitted through four transmission antennas. The number of columns in the coding matrix corresponds to the number of transmit antennas, and the number of rows corresponds to the time it takes to transmit the four symbols, i.e., four symbols are four during four time periods. It can be seen that the transmission through the two antennas.

을 송신하고, 상기 제1송신안테나(306)를 제외한 나머지 송신안테나들(308, 310, 312)에서는 어떤 신호도 송신하지 않는다. 두 번째 시간 구간에서는 제2송신안테나(308)를 통해서

를 송신하고, 상기 제2송신안테나(308)를 제외한 나머지 송신안테나들(306, 310, 312)에서는 어떤 신호도 전송하지 않는다. 세 번째 시간구간에서는 제3송신안테나(310)를 통해서

를 전송하고, 상기 제3안테나(310)를 제외한 나머지 송신안테나들(306, 308, 312)에서는 어떤 신호도 전송하지 않는다. 네 번째 시간구간에서는 제4송신안테나(312)를 통해서

를 전송하고, 상기 제4송신안테나(312)를 제외한 나머지 송신안테나들(306, 308, 310)에서는 어떤 신호도 전송하지 않는다. That is, the signal is transmitted through the first transmitting antenna 306 in the first time interval.

And no signal is transmitted from the transmission antennas 308, 310, and 312 except for the first transmission antenna 306. In the second time interval, through the second transmission antenna 308

Is transmitted, and no signal is transmitted from the transmission antennas 306, 310, and 312 except for the second transmission antenna 308. In the third time interval, through the third transmission antenna 310

The transmission antennas 306, 308, and 312 except for the third antenna 310 do not transmit any signal. In the fourth time interval, through the fourth transmitting antenna 312

The transmission antennas 306, 308, 310 except for the fourth transmission antenna 312 do not transmit any signal.

을 복원하게 된다.As such, when four symbols are received at a receiver (not shown) through a wireless channel for four time periods, the receiver performs the modulation symbol sequence in a maximum likelihood (ML) decoding scheme.

Will be restored.

In addition, Tae-Jin Chung and Jeon-Hoon Jung proposed a pre-coder and concatenated code with better coding gain than the space-time block coding scheme proposed by Giannakis Group in 2003. Tae-Jin Chung and Jeon-Hoon Jung replaced S.M. with the diagonal matrix suggested by Giannakis Group. The coding gain is improved by concatenating the space-time block code proposed by Alamouti. For the convenience of explanation, the space-time block codes proposed by Tae-Jin Chung and Jeon-Hoon Chung will be referred to as Alamouti FDFR STBC (Alamouti Full Diversity Full Rate Space Time Block Codes).

FIG. 4 illustrates a configuration of a transmitter in a mobile communication system using four transmission antennas proposed by Jeong Tae-jin and Jeon, Ji-hoon, a research team according to the prior art, and using a space-time block coding scheme. As shown, the transmitter comprises a precoder 400, a mapper 402, a delayer 404, two Alamouti encoders 406, 408 and four transmit antennas 410, 412, 414, 416).

을 생성한다.Referring to FIG. 4, first, the pre encoder 400 encodes and outputs four input modulation symbols so that a rotation of a signal occurs in a signal space. Here, it is assumed that the four modulation symbols inputted to the precoder 400 are d1, d2, d3, d4, and a symbol string consisting of the four modulation symbols is d. The precoder 400 performs a complex vector on the modulation symbol sequence d through Equation 5 as shown in Equation 5 below.

Create

이다. here,

to be.

을 출력한다. 여기서, 상기 첫 번째 벡터

는 Alamouti 부호화기(406)로 입력되고, 두 번째 벡터

는 지연기(404)로 입력된다.The mapper 402 combines two symbols of four symbols from the precoder 400 into two vectors of two elements.

Outputs Where the first vector

Is input to the Alamouti encoder 406, and the second vector

Is input to the delayer 404.

을 한 시간구간동안 버퍼링한후 Alamouti 부호화기(408)로 출력한다. 즉, 상기 사상기(402)의 첫 번째 벡터

는 첫 번째 시간에 Alamouti 부호화기(406)에 입력되며, 두 번째 벡터

는 두 번째 시간에 Alamouti 부호화기(408)에 입력된다. 여기서, Alamouti 부호화기라 함은 앞에서 언급한 S.M.Alamouti 가 제안한 시공간 블록 부호화 방식을 사용하는 부호화기를 나타낸다.The retarder 404 is the second vector

Is buffered for one time period and then output to the Alamouti encoder 408. That is, the first vector of the mapper 402

Is input to the Alamouti encoder 406 at the first time, and the second vector

Is input to the Alamouti encoder 408 at a second time. Here, Alamouti encoder refers to an encoder using the space-time block coding scheme proposed by SMAlamouti mentioned above.

을 첫 번째 및 두 번째 시간구간에서 제1송신안테나(410)와 제2송신안테나(412)를 통해서 송신되도록 부호화한다. 그리고 상기 Alamouti 부호화기(408)는 상기 지연기(404)로부터의

을 세 번째 및 네 번째 시간구간에서 제3송신안테나(414)와 제4송신안테나(416)를 통해서 송신되도록 부호화한다. 즉, 상기 Alamouti 부호화기들(406, 408)의 출력 신호를 다중 안테나를 통해 송신하기 위한 부호화 행렬은 하기 <수학식 6>과 같이 표현된다.The Alamouti coder 406 is provided from the mapper 402

Is encoded to be transmitted through the first transmission antenna 410 and the second transmission antenna 412 in the first and second time intervals. And the Alamouti encoder 408 is decoded from the delayer 404.

Is encoded to be transmitted through the third transmission antenna 414 and the fourth transmission antenna 416 in the third and fourth time intervals. That is, an encoding matrix for transmitting the output signals of the Alamouti encoders 406 and 408 through multiple antennas is expressed as in Equation 6 below.

The coding matrix of Equation 6 is different from the coding matrix described in Equation 4 in that it is implemented in Alamouti rather than diagonal matrix form. That is, the coding gain is increased by using Alamouti's STBC method. The I-th row of the coding matrix indicates that it is transmitted in the i-th time interval, and the j-th column indicates that it is transmitted through the j-th transmission antenna.

과

을 각각 송신한다. 두 번째 시간구간에서는 제1송신안테나(410)와 제2송신안테나(412)를 통해

과

을 각각 송신한다. 세 번째 시간구간에서는 제3송신안테나(414)와 제4송신안테나(416)를 통해

과

을 각각 송신한다. 네 번째 시간구간에서는 제3송신안테나(414)와 제4송신안테나(416)를 통해

과

을 각각 송신한다.That is, in the first time interval, the first transmission antenna 410 and the second transmission antenna 412 are used.

and

Send each one. In the second time interval, the first transmission antenna 410 and the second transmission antenna 412 are used.

and

Send each one. In the third time interval, the third transmission antenna 414 and the fourth transmission antenna 416 are used.

and

Send each one. In the fourth time interval, the third transmission antenna 414 and the fourth transmission antenna 416 are used.

and

Send each one.

에 대하여 최대 우도 복호(maximum likelihood decoding : ML 복호)를 수행하여야 하므로 상당히 많은 계산량이 요구된다. 이런 높은 복잡도를 낮추기 위하여 삼성전자 채찬병 등이 새로운 시공간 블록 부호 방식을 제안하였다.However, the Alamouti FDFR STBC described above also requires a high level of coding complexity because it requires calculation between all elements of the precoder stage and an input vector in order to precode the transmitter. For example, if there are four transmitting antennas, since the element of the precoder does not include 0, all 16 terms should be performed. Again, the receiver also sends a signal from the transmitter

The maximum likelihood decoding (ML decoding) needs to be performed on the RPC and thus a considerable amount of computation is required. In order to reduce this high complexity, Samsung Electronics, Chae-Byung, et al. Proposed a new space-time block code method.

Equation 7 represents a precoder for an even number of antennas, and the calculation process thereafter is the same as that of Prof. Jeon Hoon-hoon's research group. However, the complexity of the receiver's maximum likelihood decoding (ML decoding) is significantly reduced through a series of computational processes, namely, puncturing and movement.

Despite these attempts, however, the complexity was so high compared to the conventional Alamuti, which can perform linear decoding, and efforts have been made to further reduce the complexity. In the meantime, Sundar Ragan's Professor Group (hereinafter referred to as Sundar Ragan Group) of India proposed a space-time block code with linear decoding and full diversity full rate.

에

를 곱하여(복소평면상에서

만큼 회전함을 의미한다) 새로운 값

를 얻은 후, 이 새로운 값의 실수부 허수부를 재구성하여 얻은 것을 나타내며 아래의 수학식 8의 부호화 행렬을 의미한다. The following describes the STBC of the Sundar Ragan group. The STBC of the Sundar Ragan group is the value of

on

Multiply by (in the complex plane

Rotates by) new value

After obtaining, it represents that obtained by reconstructing the real part imaginary part of this new value and means the coding matrix of Equation 8 below.

를 특정 값으로 고정하여 사용한다. 즉,

를 사용한다.Using Equation 8 allows linear decoding at the receiver, thereby reducing the complexity. Here Sundar Rajan is a phase rotator.

Fixed to a specific value. In other words,

Use

)만큼 곱해진 후, 사상기를 통하여 재구성이 이루어진다. In the mobile communication system using the space-time block coding scheme of the Sundar Ragan group, the information symbols pass through the pre-encoder and exp (j

After multiplying by), reconstruction takes place through the mapper.

에서

로 섞이게 된다. 사상기는 이렇게 재구성한 c' 심볼들을 2개씩 묶어 [c'₂c₁'][c₄'c₃']벡터들을 출력한다. 이들 벡터들은 각각 Alamouti 부호화기를 통하여 전송된다. In other words,

in

It is mixed with. The mapper combines these reconstructed c 'symbols into two [c' ₂ c ₁ '] [c ₄ ' c ₃ '] vectors. These vectors are each transmitted via an Alamouti encoder.

However, the methods mentioned above also need to be further improved. It is designed to achieve full diversity full rate in a system using an even number of transmit antennas, but the receiver is more complicated than the existing Alamouti.

Thus, there is a need for a system that improves performance without complicating the receiver structure. Currently, the IEEE802.16 system uses a space-time code that uses the identity matrix as the pre-encoder in FIG. In this case, only two diversity gains can be obtained in a system using four transmitting antennas, but the Alamouti code receiver can be used as it is. However, for more accurate communication, these systems also need to improve their performance.

Therefore, there is a need for an apparatus and method for improving the BER (bit error rate) / frame error rate (FER) performance in a system using a space-time code using an identity matrix in a communication system using a plurality of antennas.

Accordingly, an object of the present invention is to provide a space-time block encoding apparatus and method for improving performance in a mobile communication system using a plurality of antennas.

According to a first embodiment of the present invention for achieving the above objects, the present invention is a transmitter of a communication system using a plurality of transmitting antennas, the real symbol and the imaginary part by encoding the input symbol sequence according to a predetermined rule A grouping block for forming an antenna grouping pattern by using an encoder (matrix A which is an identity matrix) and channel information fed back from a receiver, and multiplying the encoded symbol vector by generating a shuffling symbol vector. The present invention provides a transmitter including a plurality of Alamouti encoders that perform Alamouti encoding on each of the symbol vectors from the grouping block and transmit the same through an antenna.

According to another embodiment of the present invention, in the receiver of a space-time block encoding or space-time frequency block encoding communication system using a plurality of receiving antennas, a channel for calculating channel coefficients with a signal received through the receiving antenna A receiver comprising an estimator and a feedback transmitter for transmitting a channel coefficient indicating channel information or a calculated antenna grouping pattern from the channel estimator to a grouping block located after an encoder of the transmitter.

In addition, the present invention provides methods for implementing the above embodiments. In addition, other embodiments included in the protection scope of the present invention can be realized in order to achieve the object of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Therefore, in the present invention, a space-time code using an identity matrix is used to reduce the complexity of the receiver. That is, the present invention proposes antenna grouping to improve the performance in a system using the equation matrix A space-time code as an identity matrix, and it can be seen that the performance is improved by using the same. Here, matrix A used as the identity matrix exists at the position as shown in FIG. 6 and is represented by Equation 9 below.

In Equation 9, a column represents a transmission time and a row represents an antenna.

5 is a diagram illustrating a configuration of a transmitter in a mobile communication system using a space-time block coding scheme according to the present invention. Here, an example of a mobile communication system having four transmitting antennas will be described. Before the grouping block, as shown in FIG. 6 below, an area representing the equation matrix A space-time code exists. The grouping block receives a symbol sequence according to the equation A space-time code, and receives a grouping pattern from a receiver. Here, the grouping pattern is the same as the term grouping index and is used interchangeably. Here, the grouping index means information indicating which of the four antennas and which antennas are to be grouped to correspond to the Alamoti encoder.

That is, the grouping block maps the input information symbol x to four antennas with reference to the grouping index received from the terminal which is the receiver. For example, suppose that the terminal feeds back a grouping index that includes information on tying the first antenna and the second antenna into one Alamouti encoder and tying the third and fourth antennas into one Alamouti encoder. In this case, the first two times, i.e., t = t1 and t2, are transmitted through antenna 1 and 2, and the other two times, t = t3 and t4, are transmitted through antennas 3 and 4. In Equation 9, since a column represents time and a row represents an antenna, such transmission is performed.

6 is a diagram illustrating a configuration of a transmitter in a mobile communication system using a space-time frequency block coding scheme according to the present invention. Again, the identity matrix of Equation 9 above is used. The row in Equation 9 represents an antenna, and the column represents time and frequency. The signals of the first two columns are transmitted at frequency 1, and the signals of the other two columns are transmitted at frequency 2. Also, in each of the two column signals, the previous signal is transmitted at t = t1 and the latter signal is transmitted at t2. This matrix can be used in an OFDM system.

The grouping block maps the input information symbol x to four antennas with reference to the grouping index received from the terminal. For example, if the terminal feeds back a grouping index that binds the first antenna and the second antenna to one Alamouti encoder and the third and fourth antennas to one Alamouti encoder, according to Equation 9 above. Is sent. That is, the first two columns are mapped to f1 and transmitted through t1 and t2 through transmit antennas 1 and 2, and the remaining two columns are mapped to f2 and transmitted through antennas 3 and 4 through t1 and t2.

5 shows a diagram of a transmitter applying antenna grouping to a space-time block code. When the grouping index is fed back from the receiver, Equation 9 is multiplied by an AG1, AG2 or AG3 matrix to pass through the Alamouti coder. The final result can be expressed as A1, A2, A3, which will be described later.

6 shows a diagram of a transmitter applying antenna grouping to a space-time frequency block code. Since the process is the same as FIG.

7 is a diagram illustrating a configuration of a receiver in a mobile communication system using a space-time block coding scheme according to the present invention. For the sake of simplicity, the case of assuming one receiving antenna is illustrated. The channel estimator 702 of the receiver estimates the channel of the incoming signal through the receiving antenna, and then receives the signal through a series of decoding processes through devices such as the detector 704, the parallel / serial converter 706, and the demodulator 708. Decode the signal. In addition, after channel estimation, which is channel information, is obtained by channel estimation, the channel information is transmitted to the grouping block of the transmitter through the feedback transmitter 710. Now, the feedback transmitter 710 will be described to understand the operation.

The present invention proposes two methods of estimating channels at the receiver and blowing the values of each channel to the transmitter as it is, or feeding back a grouping index indicating a new antenna grouping pair.

1) When all channel information is informed

When the channel value (coefficient), which is the channel information estimated by the receiver, is blown to the transmitter, Equation 10 below is performed in the transmitter's grouping block.

여기서, i,j,m,n은 1에서 4까지의 임의의 값이다. 즉, 안테나 그룹핑은 수신기로부터 h1~h4의 채널 값을 피드백 받으면 모든 경우를 고려하여 <수학식 10>을 만족하는 (i,j), (m,n) 짝을 찾아 새로이 그룹핑하여 송신기의 그룹핑 블록으로 전송한다. 이러한 그룹핑의 예는 아래의 <수학식 11>의 A1, A2,A3의 형태가 된다.

Where i, j, m, n is any value from 1 to 4. That is, when the antenna grouping receives the channel values of h1 to h4 from the receiver, in consideration of all cases, the antenna grouping finds the (i, j) and (m, n) pairs satisfying Equation 10 and newly groups the grouping blocks of the transmitter. To send. An example of such grouping is in the form of A1, A2, A3 in Equation 11 below.

If there are two or more receiving antennas, the following operation is performed first. For simplicity, it is assumed here that there are two receiving antennas. If there are two receiving antennas, there are eight channels from four transmitting antennas to two receiving antennas. Using this channel in general, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2. Here, h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in transmission antenna i. That is, h_11 and h_21 indicate channel values corresponding to reception antennas 1 and 2 in transmission antenna # 1. At this time, h_1 = (| h_11 | ^ 2 + | h_21 | ^ 2) / 2 is calculated. In this way, the calculation for all channels yields h_1 to h_4. After that, the new antenna grouping is obtained by using Equation 10 above.

2) Feedback transmission of a grouping pattern (grouping index) indicating a new antenna grouping pair

In a real system, transmitting all channels received from a receiver to a transmitter introduces a number of difficulties in the implementation of the system. Therefore, a method of computing a series of processes at Equation (Equation 10) and feeding back the obtained result can be used to newly group the antenna grouping block using this grouping pattern. That is, the feedback transmitter 710 of the receiver feeds back a grouping pattern (grouping index) indicating an antenna grouping pair to the grouping block of the transmitter. The grouping block of the transmitter performs a new antenna grouping using a grouping pattern (grouping index) received from the receiver.

5 and 6 show the grouping patterns (grouping indexes) described above.

8 is a flowchart illustrating an operation of a transmitter in a mobile communication system using a space-time block coding scheme according to the present invention. When the transmission data string is input (802), the antenna grouping is obtained using Equation 10 using the channel coefficient which is the channel information transmitted from the receiver (806), or the antenna grouping is selected using the grouping index transmitted by the receiver. (816). The present invention uses either of these two methods. Thereafter, the selected antenna grouping is multiplied by the data sequence, and two symbols are bundled to generate two vectors (808). Thereafter, the two vectors are encoded using the Alamouti method to perform space-time frequency mapping (810). Thereafter, each signal is transmitted through the corresponding antenna (812).

9 is a flowchart illustrating an operation of a receiver in a mobile communication system using a space-time block coding scheme according to the present invention. When receiving the transmission data sequence, the channel estimate 904 is transmitted and the channel value (coefficient), which is channel information, is transmitted to the transmitter (914). In this case, the transmitter performs a new antenna grouping using Equation 10. Alternatively, if the system promises in advance, the receiver may transmit the antenna grouping index to the transmitter after calculating the antenna grouping by using Equation 10 without transmitting the channel value as it is. It should be noted here that, when the transmitter receives channel information from the receiver and directly obtains antenna grouping, it is necessary to send back the index of the antenna grouping pattern obtained to the receiver in order to increase communication accuracy. That is, when the indicator value of the transmitter does not match the indicator value of the receiver, data communication may be accurate by transmitting the shuffling pattern selected by the transmitter to the receiver through a common channel. A subsequent receiver performs a detection function 906 for detecting a received signal using the channel estimation information, and is input to the demodulator 910 through a parallel / serial conversion function 908, and demodulates data 910 for demodulating data. ).

10 is an example of a performance analysis curve of a mobile communication system using a space-time block coding scheme according to the present invention. This shows the uncoded BER performance. It can be seen that a gain of 3dB or more can be obtained at 10 ⁻³ BER compared to the case of using only Equation 9 matrix A. This simulation shows the performance curves in a Rayleigh flat fading channel, QPSK environment.

11 is another example of a performance analysis curve of a mobile communication system using a space-time block coding scheme according to the present invention. Here, coded bit error rate (BER) / frame error rate (FER) performance is shown. In the case of the present invention, it can be seen that the bit error rate (BER) / frame error rate (FER) performance is better. The simulation is based on the IEEE802.16 system environment. For specific simulation conditions, it is assumed that the terminal moves 3km / h in the Pedestrian A channel. QPSK and channel coding with convolutional Turbo code 1/2 coding rate are used. IEEE802.16 has subchannel structures of band AMC and FUSC. In this simulation, band AMC is used.

In order to explain the specific operation of the present invention, an actual system will be described as an example. The IEEE802.16 system is an OFDMA system. In this case, in order to reduce feedback information, an average channel value is transmitted by grouping N subcarriers. In this case, the transmitter calculates antenna grouping based on the average channel value received for each subchannel. Thereafter, the receiver is notified of the antenna grouping to be used by the transmitter, and bidirectional communication can ensure the accuracy of the communication.

If the UE gives the antenna grouping index feedback, the base station selects and uses a transmission space-time block coder according thereto.

When the terminal transmits ob110010 through the CQICH, the base station transmits A1.

When the terminal transmits ob110011 through the CQICH, the base station transmits A2.

When the terminal transmits ob110100 through the CQICH, the base station transmits A3.

In the above, the case in which the receiver receives the channel information or the antenna grouping index from the receiver has been described. However, the idea of the present invention can be realized even when the receiver is not fed back the information. That is, in the case of an open loop in which information is not received from the receiver, the basic effect of the present invention can be obtained even if the following Equation 11 is permutated in the grouping block.

Where A = [A_1 | A_2 | A_3] can improve the performance of the system by using a matrix permutation over time. In this case, no feedback from the channel is required. And can be configured irrespective of the permutation order of A_1, A_2, A_3.

A method of determining the permutation order for each subcarrier in the OFDMA communication system is shown in Equation 12.

<Equation 12>

: k = mod( floor( (Nc-1)/2) , 3) + 1

k = mod (floor ((Nc-1) / 2), 3) + 1

Here, Nc is a logical data subcarrier number. Nc = {1,2,3, ..., number of total subcarriers}. The logical data subcarrier number represents a subcarrier number of the FFT in OFDM. As shown in Equation 12, the logical data subcarrier numbers 1 and 2 have an antenna grouping pattern of A ₁ , and the logical data subcarrier numbers 3 and 4 have an antenna grouping pattern of A ₂ , and the logical data subcarrier number 5, 6 has an antenna grouping pattern of A ₃ . The antenna grouping pattern for the remaining subcarriers is also determined by Equation 12 above.

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

As described above, the present invention relates to an apparatus for space-time block encoding in a transmitter of a communication system using transmission antennas, and the performance of the space-time block code in a method of transmitting an input symbol string through a plurality of transmission antennas according to a predetermined rule. The performance of the space-time block code is improved by using the feedback information sent from the receiver to improve the performance and providing a shuffling mapper to the transmitter.

Claims (34)

In a transmitter of a communication system using a plurality of transmit antennas, An encoder for encoding a symbol string input according to a predetermined rule to form a symbol vector including a real part and an imaginary part; A grouping block for forming an antenna grouping pattern using channel information fed back from a receiver, multiplying the encoded symbol vector by a coded symbol vector, and generating a grouping symbol vector to perform new antenna grouping; And a plurality of Alamouti encoders for performing Alamouti encoding on each of the symbol vectors from the grouping block through a corresponding antenna. The transmitter of claim 1, wherein the transmitter of the communication system using the plurality of transmit antennas is a transmitter of a space-time block coded communication system or a space-time frequency block coded communication system using a plurality of antennas. The method according to claim 1 or 2, The matrix of symbol vectors passing through the encoder is characterized by the following equation (12).

The method of claim 1, wherein In the case where the transmission antennas are four and the reception antennas of the receiver are one, an equation for forming an antenna grouping pattern using channel information fed back from the receiver in the grouping block is expressed by Equation 13 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. In other words, the best channel and the worst channel form one group, and the second good channel and the third good channel form one group. That is, assuming h1> h2> h3> h4, (1, 2) and (3, 4) are fed back. The method of claim 1, wherein In the case where the transmission antennas are four and the reception antennas of the receiver are two, an equation for forming an antenna grouping pattern using channel information fed back from the receiver in the grouping block is given by Equation 14 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. In a transmitter using a plurality of transmit antennas, An encoder for encoding a symbol string input according to a predetermined rule to form a symbol vector including a real part and an imaginary part; A grouping block multiplying the encoded symbol vector by the antenna grouping pattern fed back from a receiver to generate a grouping symbol vector to perform new antenna grouping; And a plurality of Alamouti encoders for performing Alamouti encoding on each of the symbol vectors from the grouping block through a corresponding antenna. The transmitter of claim 6, wherein the transmitter of the communication system using the plurality of transmit antennas is a transmitter of a space-time block coded communication system or a space-time frequency block coded communication system using a plurality of antennas. The method according to claim 6 or 7, The matrix of symbol vectors passing through the encoder is characterized by the following equation (15).

The method of claim 6, wherein In the case where the transmission antennas are four and the reception antennas of the receiver are one, an equation for forming an antenna grouping pattern using channel information fed back from the receiver in the grouping block is expressed by Equation 16 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. The method of claim 6, wherein In the case of four transmitting antennas and two receiving antennas, an equation for forming an antenna grouping pattern using channel information fed back from the receiver in the grouping block is represented by Equation 17 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. In a transmitter using a plurality of transmit antennas, An encoder for encoding a symbol string input according to a predetermined rule to form a symbol vector including a real part and an imaginary part; A grouping block that multiplies a predetermined antenna grouping pattern by the encoded symbol vector to permutate a grouping symbol vector to generate antenna grouping; And a plurality of Alamouti encoders for performing Alamouti encoding on each of the symbol vectors from the grouping block through a corresponding antenna. The transmitter of claim 11, wherein the transmitter of the communication system using the plurality of transmit antennas is a transmitter of a space-time block coded communication system or a space-time frequency block coded communication system using a plurality of antennas. The method according to claim 11 or 12, wherein The matrix of symbol vectors passing through the encoder is characterized by the following equation (18).

The method of claim 11, wherein The predetermined antenna grouping pattern is a transmitter according to the following equation (19).  A = [A_1 | A_2 | A_3]

The method according to claim 11, wherein Antenna grouping pattern by subcarriers

(A = A ₁ , B = A ₂ , C = A ₃ ), wherein the transmitter is determined as in Equation 20 below. <Equation 20>

k = mod (floor ((logical data subcarrier number-1) / 2), 3) + 1 Logical data subcarrier number = 1, 2, 3, ..., total subcarriers A receiver of a space-time block encoding or space-time frequency block encoding communication system using a plurality of receiving antennas, A channel estimator for calculating channel coefficients with a signal received through a receiving antenna; And a feedback transmitter for transmitting the channel coefficients representing the channel information or the calculated antenna grouping pattern from the channel estimator to a grouping block located after the encoder of the transmitter. The method of claim 16, The equation for calculating the antenna grouping pattern in the feedback transmitter when the transmitter has 4 transmit antennas and the receiver has 1 receiver is as shown in Equation 21 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. The method of claim 16, The equation for calculating the antenna grouping pattern in the feedback transmitter when the transmitter has four transmit antennas and the receiver has two receive antennas is represented by Equation 22 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. A transmission method of a space-time block encoding or space-time frequency block encoding communication system using a plurality of transmitting antennas, An encoding step of encoding an input symbol string according to a predetermined rule to form a symbol vector including a real part and an imaginary part; Forming an antenna grouping pattern using channel information fed back from a receiver, and multiplying the encoded symbol vector by the encoded symbol vector to generate a grouping symbol vector; Transmitting each of the grouping symbol vectors by Alamouti coding through corresponding antennas. The method of claim 19, The matrix formed in the encoding step is the same as <Equation 23>.

The method of claim 19 and 20, In the case where the transmission antennas are four and the reception antennas of the receiver are one, the equation for forming the antenna grouping pattern is expressed by Equation 24 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. The method of claim 19, In the case where the transmission antennas are four and the reception antennas of the receiver are two, the equation for forming the antenna grouping pattern is expressed by Equation 25 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. A transmitter of a space-time block encoding or space-time frequency block encoding communication system using a plurality of transmitting antennas, An encoding step of encoding an input symbol string according to a predetermined rule to form a symbol vector including a real part and an imaginary part; Generating a grouping symbol vector by multiplying the encoded symbol vector by an antenna grouping pattern fed back from a receiver; Transmitting each of the shuffling symbol vectors by Alamouti coding and corresponding antennas. The method of claim 23, wherein The matrix formed in the encoding step is characterized by the following equation (26).

The method of claim 23, wherein The equation for forming an antenna grouping pattern when the transmission antennas are four and the reception antennas of the receiver is one is shown in Equation 27 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. The method of claim 23, wherein The equation for forming the antenna grouping pattern when the transmission antennas are four and the reception antennas of the receiver is two is represented by Equation 28 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. In the transmission method of a space-time block coded communication system or a space-time frequency block coded communication system using a plurality of transmit antennas, An encoding step of encoding an input symbol string according to a predetermined rule to form a symbol vector including a real part and an imaginary part; Generating a grouping symbol vector by multiplying a predetermined antenna grouping pattern by the encoded symbol vector; Transmitting each of the shuffling symbol vectors by Alamouti coding and corresponding antennas. The method of claim 27, The matrix of symbol vectors formed in the encoding step is represented by Equation 29 below.

The method of claim 27 and 28, The predetermined antenna grouping pattern is a transmitter, characterized in that as shown in Equation (30).

A receiving method of a space-time block encoding or space-time frequency block encoding communication system using a plurality of receiving antennas, A channel estimation step of calculating channel coefficients with a signal received through a receiving antenna; And a feedback transmission step of transmitting a channel coefficient indicating the channel information or the calculated antenna grouping pattern from the channel estimator to the transmitter. The method of claim 30, The equation for calculating the antenna grouping pattern in the feedback transmitter when the transmitter has 4 transmission antennas and the reception antenna is 1 is represented by Equation 31 below.

Here, i, j, m, n are arbitrary values, and h values are channel coefficients representing channel information. The method of claim 30, The equation for calculating the antenna grouping pattern in the feedback transmitter when the transmitter has 4 transmission antennas and the reception antennas is 2 is as shown in Equation 32 below.

Here, i, j, m, n are arbitrary values from 1 to 4, and h values are channel coefficients representing channel information. Here, h_i = (| h_1i | ^ 2 + | h_2i | ^ 2) / 2, and h_1i and h_2i represent channel values corresponding to reception antennas 1 and 2 in the transmission antenna i. In the transmission method of a transmitter using a plurality of transmission antennas, Selecting one of the encoding matrices of Equation 33 according to the subcarrier number to be mapped; And encoding the symbols to be transmitted with the selected coding matrix to map the space-time frequency.

Here, the rows of the matrix are respectively mapped to the transmit antenna, the first two columns are mapped to n subcarriers, the remaining two columns are mapped to n + 1 subcarriers, and columns 1 and 3 are the first time interval. Maps to, and columns 2 and 4 map to the second time interval. The method of claim 33, wherein When the subcarrier number is Nc (= 1,2,3, ..., the total number of subcarriers), the subcarrier coding matrix

Is determined as in Equation 34 below. <Equation 34>

k = mod (floor ((Nc-1) / 2), 3) + 1

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