KR20180061455A - Apparatus and method for Multi Strata Space Time Block Code ARQ(Automatic Repeat Request) based on MIMO(Multi Input Multi Output) - Google Patents

Abstract

An apparatus for multi strata space time block code automatic repeat request (ARQ) based on multi input multi output (MIMO) and a method thereof are disclosed. The present invention is to provide an apparatus for multi strata space time block code ARQ based on MIMO and a method thereof which can mitigate an interference between a plurality of multi strata space time block codes (MSSTCs) by allocating power and phase at each retransmission in a transmitting stage with a low complexity and high error rate performance at a receiving stage of a retransmission communication system and transmit each of the plurality of MSSTCs through a plurality of transmission antennas. The apparatus according to the present invention comprises: a cyclic redundancy check (CRC) encoder for CRC-encoding transmission data; a demux that separates the CRC encoded transmission data into eight symbols; a first multi strata space time block coding unit for grouping first to fourth symbols among the eight symbols into a first layer and a second layer and after coding symbols of the grouped first layer and the second layer, allocating power and phase for each of the first layer and the second layer to output a first multi strata space time block code; a second multi strata space time block coding unit for grouping fifth to eighth symbols among the eight symbols into a third layer and a fourth layer and after coding symbols of the grouped third layer and the fourth layer, allocating power and phase for each of the third layer and the fourth layer to output a second multi strata space time block code; and a scheduler for receiving a feedback signal transmitted from the receiving stage and controlling the first multi strata space time block coding unit and the second multi strata space time block coding unit so that the transmission data is retransmitted according to the received feedback signal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer space-time block code retransmission apparatus and a multi-

The present invention relates to a multi-antenna based multi-layer space-time block code retransmission apparatus and method.

A multi-layer space time block code (MSSTC) combines and transmits a plurality of independent orthogonal space time block codes (OSTBC) to obtain a high data reception rate.

On the other hand, the ARQ (Automatic Repeat Request) technique is a technique for improving the reliability of a communication system by retransmitting data to a receiver when an error occurs in the transmission data in the communication system.

The MDC-QOSTBC scheme transmits QOSTBC (Quasi Orthogonal Space Time Block Code) using a structure when the number of transmit antennas is 4. In the MIMO (Multi Input Multi Output) environment, There is an MSSTC MIMO-ARQ scheme to achieve high reception ratio and block error rate performance.

In the case of the MDC-QOSTBC technique, since different types of detection techniques must be used at each receiving end in each retransmission, the detection complexity of the receiving end is very complicated and a device for continuously storing the previously detected results is also required. Which is inconvenient in data communication.

In the conventional MSSTC MIMO-ARQ scheme, since it is a technique limited to a 2xN _r MIMO environment, it is difficult to apply to a communication system environment having a plurality of transmission antennas, and there is no resource allocation rule have. That is, an MSSTC automatic retransmission scheme having a high data reception rate and a low error rate in a MIMO-ARQ environment having a plurality of transmission antennas has not been studied yet.

The present invention has a high complexity and a high error rate performance in a receiver of a retransmission communication system and allocates a power and a phase at each retransmission in a transmitter to thereby obtain a plurality of multi-layer space time block codes (MSSTC) Space-time block code retransmission apparatus and method for mitigating interference and transmitting a plurality of multi-layer space-time block codes through a plurality of transmission antennas.

According to an aspect of the present invention, a multi-antenna based multi-layer space time block code (MSSTC) automatic repeat request (ARQ) apparatus having four transmit antennas is disclosed.

A multi-antenna STBC scheme retransmitting apparatus according to an embodiment of the present invention includes a CRC encoder for CRC-encoding transmission data, a demultiplexer for separating the CRC-encoded transmission data into 8 symbols, 1 to 4 symbols into a first layer and a second layer, encodes the symbols of the first layer and the second layer that are grouped, and then assigns power and phase to each of the first layer and the second layer A first multi-layer space-time block coder for outputting a first multi-layer space-time block code, a fifth multi-layer space-time block coder for grouping fifth through eighth symbols of the 8 symbols into a third layer and a fourth layer, A second multi-layer space-time block coder for encoding symbols of four layers, and outputting a second multi-layer space-time block code by allocating power and phase to the third layer and the fourth layer, And a scheduler for controlling the first multi-layer space-time block coder and the second multi-layer space-time block coder so that the transmission data is retransmitted according to the received feedback signal, A first codeword composed of one multi-layer space-time block code and a second codeword composed of the second multi-layer space-time block code are transmitted through a pair of corresponding transmission antennas.

A total of four orthogonal space time block codes (OSTBC) (C ₁ , C ₂ , C ₃ , C ₄ ) are generated by combining the eight symbols.

)은 다음의 수학식으로 나타난다.The four orthogonal space-time block codes are overlapped by two to form two multi-layer space-time block codes, and a transmission codeword matrix

) Is expressed by the following equation.

,

,

,

는 송신 코드워드 행렬의 각 계층을 나타내고, 상기 4개의 송신 안테나 각각을 통해 전송됨Where p _{l, i} and θ _{l, i} represent the power and phase assigned to each layer during the i th transmission,

,

,

,

Represents each layer of the transmitted codeword matrix and is transmitted via each of the four transmit antennas

The power and phase are allocated at each transmission.

The power is allocated according to an optimum power allocation ratio that maximizes a coding gain distance (CGD) at the time of initial transmission, and an optimal power allocation ratio is calculated using the following equation.

Here, the minimum coding gain distance

In the case of the _{i = 1 p 1,1: p 2,1} : p 3,1: p 4,1 = p 1,1 opt: p 2,1 opt: p 3,1 opt: p 4,1 opt If, in the _{i = 2 p 1,2: p 2,2} : p 3,2: p 4,2 = p 2,1: p 1,1: p 4,1: p 3,1, the i > 2, the power is allocated at a ratio of p _{1, i} : p _{2, i} : p _{3, i} : p _{4, i} = 1: 1: 1:

The optimal power allocation ratio is p _{1, 1} ^opt : p _{2 , 1} ^opt : p _{3 , 1} ^opt : p _{4 , 1} ^opt = 4: 1: 4: 1.

The phase is allocated as θ ₂ = θ ₄ = π / 2 in the initial transmission. In order to minimize the interference influence of the overlapped layer in the transmission, the phase is determined as interference according to the sign of the previous transmission interference signal received from the receiving end If the signal is negative, it is assigned π / 2, and if the interference signal is positive, it is assigned -π / 2.

The receiver performs real-valued representation and MIMO maximal ratio combining (MRC) on the received signal, and then performs MMSE-OSIC (Minimum Mean Squared Error-Ordered Successive Interference Cancellation) according to the SNR size of the received signal for each layer. And detects signals of the respective layers.

When the receiver detects an error through CRC check after detecting all symbols, it transmits a NACK as the feedback signal, thereby requesting retransmission.

According to another aspect of the present invention, there is provided a multi-antenna based multi-layer space-time (MIMO) system, which is performed by a multi-antenna based multi-layer space time block code (MSSTC) A block code retransmission method is disclosed.

The multi-antenna space-time block code retransmission method according to an embodiment of the present invention includes CRC encoding transmission data, separating the CRC-encoded transmission data into 8 symbols, separating the 8 symbols into a first layer A second layer, a third layer, and a fourth layer, encoding symbols of the first through fourth layers, grouping the power and phase of each of the first through fourth layers, Generating a multi-layer space-time block code, receiving a feedback signal transmitted from a receiving end, and controlling the transmission data to be retransmitted according to the received feedback signal, wherein the multi- Is transmitted through a corresponding pair of transmit antennas.

An apparatus and method for retransmitting a multi-antenna space-time block code according to an embodiment of the present invention has a low complexity and high error rate performance in a receiver of a retransmission communication system and allocates power and a phase every retransmission in a transmitter It is possible to mitigate the interference between multiple multi-layer space time block codes (MSSTC).

1 schematically illustrates a configuration of a multiple antenna based multi-layer space-time block code retransmission apparatus according to an embodiment of the present invention.
2 illustrates a receiving end according to an embodiment of the present invention.
3 illustrates block error rate performance of various retransmission schemes in a 4 × 2 multiple antenna retransmission environment.
FIG. 4 illustrates block error rate performance of various retransmission schemes in a 4 × 4 multiple antenna retransmission environment. FIG.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising ", or" comprising "and the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps. Also, the terms "part," " module, "and the like described in the specification mean units for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software .

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram illustrating a configuration of a multi-antenna STBC block retransmission apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a receiver according to an embodiment of the present invention.

1, a multiple antenna based multi-layer space-time block code retransmission apparatus according to an embodiment of the present invention includes a cyclic redundancy check (CRC) encoder 110, a demultiplexer 120, a first multi- 130, a second multi-layer space-time block coding unit 140, a scheduler 150, and a plurality of transmission antennas 160.

The CRC encoder 110 CRC-encodes the transmission data.

The demux 120 separates the CRC-encoded transmission data into a plurality of symbols.

The first multi-layer space-time block coding unit 130 groups a plurality of symbols input from the demux 120 into a first layer and a second layer, encodes symbols of the first layer and the second layer, And outputs a first multi-layer space-time block code by assigning power and phase to each of the first layer and the second layer.

The second multi-layer space-time block coding unit 140 groups a plurality of symbols input from the demux 120 into a third layer and a fourth layer, encodes the grouped third layer and fourth layer symbols, And outputs the second multi-layer space-time block code by allocating power and phase to the third layer and the fourth layer, respectively.

The first multi-layer space-time block coder 130 and the second multi-layer space-time block coder 140 according to an embodiment of the present invention include a first layer and a second layer of symbols, a third layer and a fourth layer OSTBC encoders 131, 132, 141 and 142 for encoding symbols into an orthogonal space time block code (OSTBC), buffers 133, 134, 143 and 144, and encoded first through fourth layers And a controller (Phase & Power Controller, 135, 145) for allocating the power and phase of the signal.

The scheduler 150 receives the feedback signal transmitted from the receiving end and controls the controllers 135 and 145 so that the transmission data is retransmitted according to the received feedback signal.

A first codeword composed of a first multi-layer space-time block code and a second codeword composed of a second multi-layer space-time block code are transmitted through a pair of corresponding transmission antennas 160.

The multiple antenna based multi-layer space time block code retransmission apparatus according to an embodiment of the present invention is assumed to be a transmitting station of an MSSTC 4xN _r MIMO-ARQ scheme having a total of 4 transmit antennas for a plurality of antenna configurations, where N _r Is the number of receiving antennas of the receiving end.

)가 생성된다. 생성된 4개의 직교 시공간 블록부호는 다음의 수학식으로 나타낼 수 있다.After the transmission data is CRC-encoded, it is divided into a total of 8 symbols, and 8 separated symbols are grouped into two to form a total of 4 orthogonal space-time block codes

) Is generated. The generated four orthogonal space-time block codes can be expressed by the following equation.

)은 다음의 수학식으로 나타낼 수 있다.The four orthogonal space-time block codes thus generated are superposed on each other to form two multi-layer space-time block codes. The two multi-layer space-time block codes formed are transmitted through a pair of transmission antennas . And the transmitted codeword matrix (i < th >

) Can be expressed by the following equation.

의 각 행은 해당 송신 데이터를 전송하는 송신 안테나(1행은 제1 안테나와 제2 안테나, 2행은 제3 안테나와 제4 안테나)를 의미하고, 각 열은 시간 슬롯을 의미한다. 즉, 두 개의 시간 슬롯 동안 총 4개의 직교 시공간 블록부호(두 개의 다중계층 시공간 블록부호)가 전송되게 된다.here,

Each row means a transmitting antenna for transmitting corresponding transmission data (one row is a first antenna and a second antenna, and a second row is a third antenna and a fourth antenna), and each column means a time slot. That is, a total of four orthogonal space-time block codes (two multi-layer space-time block codes) are transmitted during two time slots.

,

,

,

는 송신 코드워드 행렬의 각 계층을 의미하며, p_{l, i}와 θ_{l, i}는 i번째 전송 시 각 계층에 할당된 전력과 위상을 나타낸다. 여기서, 각 계층의 전력과 위상 할당을 통해서 다중계층 시공간 블록부호 각각의 내부에 존재하는 간섭이 제어됨으로써, 수신단에서 데이터 검출 성능이 향상될 수 있다.

,

,

,

Denotes the layer of the transmit codeword matrix, and p _{l, i} and θ _{l, i} denote the power and phase assigned to each layer in the i th transmission. In this case, interference in each of the multi-layer space-time block codes is controlled through the power and phase allocation of each layer, thereby improving the data detection performance at the receiving end.

In the case of the phase allocation according to the embodiment of the present invention, θ ₂ = θ ₄ = π / 2 is allocated for the initial transmission, and then, in order to effectively minimize the interference influence of the overlapped layer, / 2 or -π / 2 adaptively according to the sign of the transmission interference signal. That is, when the interference signal is negative, it is assigned to? / 2, and when the interference signal is positive, it is assigned to -π / 2. This can be expressed by the following equation.

Here,? ^(I) represents the interference at the i-th transmission and can be expressed by the following equation.

In the case of the power allocation according to the embodiment of the present invention, the optimal power allocation ratio maximizing the minimum coding gain distance (CGD) at the time of initial transmission is calculated using the following equation, Optimization is performed.

Here, the minimum coding gain distance CGD _min (p _1,1 : p _2,1 : p _3,1 : p _4,1 ) is expressed by the following equation.

Thus, after the optimal power allocation ratio that maximizes the minimum coding gain distance is obtained at the initial transmission, p ₁ , ₁ : p _2,1 : p _3,1 : p _4,1 = p _1,1 ^opt : p _2,1 ^opt : p _3,1 ^opt : p _4,1 ^opt . In the second transmission, as opposed to the power allocation ratio at the initial transmission, p _1,2 : p _2,2 : p _3,2 : p _4,2 = p _2,1 : p _1,1 : p _{4 , 1} : _p3,1 . &_Lt; / RTI > In the third and fourth transmissions, power can be allocated at a ratio of p _{1, i} : p _{2, i} : p _{3, i} : p _{4, i} = 1: 1: 1: 1.

That is, the power allocation according to an embodiment of the present invention, p _1,1 in the case of _{i = 1: p 2,1: p} 3,1: p 4,1 = 4: 1: 4: 1, i = 2 _I : p _{2, i} : p _3, p _2, p _{3, and} p _{4 are satisfied} when p _1,2 : p _2,2 : p _3,2 : p _4,2 = 1: 4: The power allocation rule of _i : p _{4, i} = 1: 1: 1: 1 applies.

It is assumed that the channel state information is receivable only at the receiving end, and the i-th received signal Y _{i at the} receiving end can be expressed by the following equation.

Here, H _i represents the channel gain matrix at the i th transmission, and it is assumed that the channel gain changes at every transmission. N _i represents a complex Gaussian noise matrix with an average of 0 and an variance of σ ² at the i th transmission.

Referring to FIG. 2, the received signal is subjected to a real-valued representation and MIMO maximal ratio combining (MRC). The received signal after the MIMO MRC can be expressed by the following equation.

와

는 다음의 수학식으로 나타낼 수 있다.here,

Wow

Can be expressed by the following equation.

Then, MMSE-OSIC (Minimum Mean Squared Error-Ordered Successive Interference Cancellation) is sequentially performed according to the SNR magnitude of the received signal for each layer, thereby detecting a signal of each layer. When all the symbols are detected and an error is confirmed through the CRC check, a retransmission is requested to the transmitting end by transmitting NACK as a feedback signal of the transmitting end.

FIG. 3 illustrates block error rate performance of various retransmission schemes in a 4 × 2 multiple antenna retransmission environment, and FIG. 4 illustrates a block error rate performance of various retransmission schemes in a 4 × 4 multiple antenna retransmission environment.

를 갖는 ANSI CRC가 사용되었다.Figs. 3 and 4 with respect to the multiple antennas based on a multi-layer space-time block code retransmission methods and other retransmission scheme according to an embodiment of the present invention, 4ⅹN _r in a multi-antenna retransmission environment, N _r = 2, 4, and the maximum number of retransmissions Represents the block error rate at the first, second and fourth times. In the experiments, the modulation order is assumed to be QPSK and the quasi-static Rayleigh faded MIMO channel environment. Then, as the generation polynomial,

Lt; RTI ID = 0.0 > CRC < / RTI >

In the case of MDC-QOSTBC with various reception detection techniques at each transmission, the MMSE detection scheme is used for the initial transmission, the DSTTD (double space time transmit diversity) detection scheme is used for the second transmission, and the QOSTBC detection scheme is used for the fourth transmission.

3 and 4, in order to verify the power allocation and phase allocation of the multi-antenna space-time block code retransmission method according to an embodiment of the present invention, The case where the power allocation and phase allocation of the space time block code retransmission method are not performed is also shown.

As shown in FIGS. 3 and 4, the multi-antenna based multi-layer space time space block code retransmission method according to the embodiment of the present invention, compared to other techniques in almost all SNR regions, regardless of the number of transmission times and the number of reception antennas You can see that the performance is better.

On the other hand, the components of the above-described embodiment can be easily grasped from a process viewpoint. That is, each component can be identified as a respective process. Further, the process of the above-described embodiment can be easily grasped from the viewpoint of the components of the apparatus.

In addition, the above-described technical features may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

It will be apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. Should be regarded as belonging to the following claims.

110: Cyclic Redundancy Check (CRC) encoder
120: Dip Mills
130: first multi-layer space-time block coding unit
140: second multi-layer space-time block coding unit
150: Scheduler
160: Multiple transmit antennas

Claims (11)

A multi-antenna multi-layer space time block code (MSSTC) automatic repeat request (ARQ) apparatus having four transmit antennas,
A CRC encoder for CRC-encoding transmission data;
A demultiplexer for separating the CRC-encoded transmission data into 8 symbols;
The first through fourth symbols of the eight symbols are grouped into a first layer and a second layer, and symbols of the first layer and the second layer are coded. Then, A first multi-layer space-time block coder for outputting a first multi-layer space-time block code by allocating power and phase;
Grouping the fifth through eighth symbols of the eight symbols into a third layer and a fourth layer, coding the grouped third layer and fourth layer symbols, and encoding the symbols of the third layer and the fourth layer, A second multi-layer space-time block coder for outputting a second multi-layer space-time block code by allocating power and phase; And
And a scheduler for receiving the feedback signal transmitted from the receiver and controlling the first multi-layer space-time block encoder and the second multi-layer space-time block encoder so that the transmission data is retransmitted according to the received feedback signal,
Wherein a first codeword composed of the first multi-layer space-time block code and a second codeword composed of the second multi-layer space-time block code are transmitted through a pair of corresponding transmission antennas. Multilayer Spatio - Temporal Block Code Retransmitter.
The method according to claim 1,
Wherein a total of four orthogonal space time block codes (OSTBC) (C ₁ , C ₂ , C ₃ , C ₄ ) are generated as follows, Multilayer Spatio - Temporal Block Code Retransmitter.

3. The method of claim 2,
The four orthogonal space-time block codes are overlapped by two to form two multi-layer space-time block codes, and a transmission codeword matrix

) Is expressed by the following equation: < EMI ID = 17.0 >

Where p _{l, i} and θ _{l, i} represent the power and phase assigned to each layer during the i th transmission,

,

,

,

Represents each layer of the transmitted codeword matrix and is transmitted via each of the four transmit antennas
The method of claim 3,
Wherein the power and the phase are allocated at each transmission.
5. The method of claim 4,
Wherein the power is allocated according to an optimal power allocation ratio that maximizes a coding gain distance (CGD) at the time of initial transmission, and an optimum power allocation ratio is calculated using the following equation Multilayer Spatio - Temporal Block Code Retransmitter.

Here, the minimum coding gain distance

6. The method of claim 5,
In the case of the _{i = 1 p 1,1: p 2,1} : p 3,1: p 4,1 = p 1,1 opt: p 2,1 opt: p 3,1 opt: p 4,1 opt If, in the _{i = 2 p 1,2: p 2,2} : p 3,2: p 4,2 = p 2,1: p 1,1: p 4,1: p 3,1, the i The power is allocated in a ratio of p _{1, i} : p _{2, i} : p _{3, i} : p _{4, i} = 1: 1: 1: Block code retransmission device.
6. The method of claim 5,
_Wherein the optimal power allocation ratio is p _{1, 1} ^opt : p _{2, 1} ^opt : p _3,1 ^opt : p _4,1 ^opt = 4: 1: 4: Retransmission device.
5. The method of claim 4,
The phase is allocated as θ ₂ = θ ₄ = π / 2 in the initial transmission. In order to minimize the interference influence of the overlapped layer in the transmission, the phase is determined as interference according to the sign of the previous transmission interference signal received from the receiving end / 2 when the signal is a negative number, and is -π / 2 when the interference signal is a positive number.
The method according to claim 1,
The receiver performs real-valued representation and MIMO maximal ratio combining (MRC) on the received signal, and then performs MMSE-OSIC (Minimum Mean Squared Error-Ordered Successive Interference Cancellation) according to the SNR size of the received signal for each layer. And detects a signal of each layer based on the received signal.
10. The method of claim 9,
Wherein the receiving end detects retransmission by transmitting a NACK as the feedback signal when an error is confirmed through a CRC check after detecting all the symbols, thereby requesting retransmission.
A multi-antenna space-time block code retransmission method performed by a multi-antenna based multi-layer space time block code (MSSTC) automatic repeat request (ARQ) apparatus having four transmit antennas,
CRC encoding the transmitted data;
Separating the CRC encoded transmission data into 8 symbols;
Grouping the eight symbols into a first layer, a second layer, a third layer, and a fourth layer;
Encoding symbols of the first through fourth layers;
Generating a multi-layer space-time block code by assigning power and phase to each of the first through fourth layers;
Receiving a feedback signal transmitted from a receiving end; And
And controlling the transmission data to be retransmitted according to the received feedback signal,
Wherein the codeword comprised of the multi-layer space-time block code is transmitted through a corresponding pair of transmit antennas.

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