KR20110018640A - Method for cooperative relaying system - Google Patents

Abstract

PURPOSE: A method for cooperative relay system is provided to have short average delay time and have decoding performance. CONSTITUTION: A method for cooperative relay system comprises as follows. A destination device operation method includes a step of receiving a first signal from a source device(S210), a step of determining whether an error detection exists or not by decoding the received first signal(S220), a step of requesting transmission of a second signal in a relay device if an error is detected in the second step, a step of receiving the second signal and estimating information bits by decoding the received first signal and the received second signal. The second signal includes determination information about each code symbols of a second error correction encoding technique which is estimated based on a result of decoding the first signal in a relay device.

Description

Method for cooperative relaying system

The disclosed technique relates to a technique for a cooperative relay system, and more particularly, but not exclusively, an adaptive hybrid automatic HARQ (hybrid automatic) using a contest / referencing hybrid relay protocol in a cooperative relay network. Repeat reQuest) technique.

Diversity is one of the techniques to overcome the performance degradation caused by fading of the wireless channel. Recently, a technique for obtaining spatial diversity gain using a virtual antenna array through cooperation of multiple relays has been proposed, which is called a cooperative diversity technique. This cooperative diversity scheme may provide an effect, such as a virtual MIMO system, to terminals that may not have a plurality of antennas.

On the other hand, in order to maximize the benefits of such a cooperative relay system, it is important to design a protocol used in the cooperative relay system, that is, a relay protocol, and as a design parameter, an average delay time (for example, a packet at a destination device) is important. Is an average of the time required to process the data, which may depend on decoding delay, waiting time, etc., and has excellent performance (eg, bit error rate performance according to decoding at the destination device) in various channel situations such as outage channel conditions. Whether or not may be considered.

The technical problem to be achieved by the disclosed technology is to provide a method for a cooperative relay system.

In order to achieve the above technical problem, an aspect of the disclosed technology is a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. In the operating method of the destination device, the first signal includes a code symbol block generated by applying an error detection coding scheme and a first error correction coding scheme to the information bits, (a) receiving the first signal Making; (b) decoding the received first signal to determine whether an error is detected; (c) if an error is detected in step (b), requesting the repeater to transmit a second signal; And (d) receiving the second signal and estimating the information bits by decoding the received first and second signals, wherein the second signal decodes the first signal received at the repeater. Provided is a method including determination information for each code symbol of a second error correction encoding technique estimated based on a result.

In one embodiment, the second signal includes any one of a hard decision signal and a soft decision signal, the hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme; The soft decision signal includes soft decision information on each of the code symbols of the second error correction coding scheme.

In one embodiment, the hard decision information includes a value of a corresponding sign symbol, and the soft decision information includes probability information on a value that a corresponding sign symbol can have.

In one embodiment, the method further comprises transmitting an accept signal to at least one of the source device and the repeater if no error is detected in step (b).

In one embodiment, the error detection coding scheme is a cyclic redundancy check code based coding scheme, and the step (b) includes (b1) decoding the received first signal corresponding to the first error correction coding scheme. Decoding with the technique; And (b2) determining whether an error is detected by performing a cyclic redundancy check based on the result decoded in (b1).

To achieve the above technical problem, another aspect of the disclosed technology is a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. In the operating method of the destination device, the first signal includes a code symbol block generated by applying an error detection coding scheme and a first error correction coding scheme to the information bits, (a) receiving the first signal Making; (b) receiving a second signal transmitted from the repeater; And (c) decoding the received first and second signals to estimate the information bits, wherein the second signal is one of a hard decision signal and a soft decision signal according to the error detection coding scheme. The hard decision signal is a signal selected based on an error detection result, and the hard decision signal includes hard decision information on each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the first signal received by the repeater. The soft decision signal may include soft decision information on each of the code symbols of the second error correction encoding scheme estimated based on a result of decoding the first signal received by the repeater.

In one embodiment, the second signal includes the hard decision signal when no error is detected in the repeater and the soft decision signal when an error is detected in the repeater.

In one embodiment, the step (c) comprises estimating the information bits by applying an iterative maximum iterative MAP decoding algorithm on the received first and second signals.

In an embodiment, the step (b) may include: (b1) determining whether an error is detected by decoding the received first signal; (b2) if an error is detected in step (b), requesting the repeater to transmit the second signal; And (b3) receiving the second signal.

In order to achieve the above technical problem, another aspect of the disclosed technology is a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. The method of operating the repeater, wherein the first signal includes a code symbol block generated by applying an error detection encoding scheme and a first error correction encoding scheme to information bits, and (a) converting the first signal. Receiving; (b) decoding the received first signal to determine whether an error is detected; (c) if an error is detected in step (b), transmitting a soft decision signal to the destination device; And (d) if an error is not detected in step (b), transmitting a hard decision signal to the destination device, wherein the hard decision signal is based on a result of decoding the received first signal. Hard decision information for each of the code symbols of the second error correction coding scheme estimated, wherein the soft decision signal is estimated based on a result of decoding the received first signal. A method is provided that includes soft decision information for each of the sign symbols.

To achieve the above technical problem, another aspect of the disclosed technology is in a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. In the method of operation of the repeater, the first signal includes a code symbol block generated by applying an error detection coding scheme and a first error correction coding scheme to the information bits, (a) receiving the first signal Making; And (b) transmitting the second signal in response to receiving the second signal from the destination device, wherein the second signal is estimated based on a result of decoding the first signal received by the repeater. It provides a method comprising the determination information for each of the code symbols of the second error correction encoding technique.

Embodiments of the present invention presented above may have an effect including the following advantages. However, all the embodiments of the present invention are not meant to include them all, and thus the scope of the present invention should not be understood as being limited thereto.

It is possible to provide a cooperative relay system having a short average delay time and excellent decoding performance (eg, bit error rate performance).

Since descriptions of embodiments of the present invention are merely illustrated for structural to functional descriptions of the present invention, the scope of the present invention should not be construed as limited by the embodiments described in the present invention. That is, the embodiments of the present invention may be variously modified and may have various forms, and thus, it should be understood to include equivalents that may realize the technical idea of the present invention.

On the other hand, the meaning of the terms described in the present invention will be understood as follows.

Terms such as "first" and "second" are intended to distinguish one component from another component, and the scope of the present invention should not be limited by these terms. For example, the first component may be named a second component, and similarly, the second component may also be named a first component.

The term “and / or” should be understood to include all combinations that can be presented from one or more related items. For example, "first item, second item, and / or third item" means "at least one or more of the first item, second item, and third item", and means first, second, or third item. A combination of all items that can be presented from two or more of the first, second and third items as well as the third item.

Singular expressions described herein are to be understood to include plural expressions unless the context clearly indicates otherwise, and the terms "comprise" or "having" include elements, features, numbers, steps, operations, and elements described. It is to be understood that the present invention is intended to designate that there is a part or a combination thereof, and does not exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, actions, components, parts or combinations thereof. .

Each step described in the present invention may occur out of the stated order unless the context clearly dictates the specific order. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in the commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and shall be interpreted as having ideal or overly formal meanings unless expressly defined in the present application. Can't be.

The protocol used in the cooperative relay system, that is, the repeater protocol, is roughly classified into an Amplify-and-Forward (AF) technique and a Decode-and-Forward (DF) technique according to its delivery method.

The AF technique can obtain full diversity gain through MRC (maximal ratio combining), but it has a disadvantage in that it requires a space for storing an analog waveform and is difficult to implement. On the other hand, the DF technique is simple to implement, but due to the propagation of errors in the repeater, it is difficult to obtain maximum diversity gain and decoding performance without elaborate processing at the destination device.

Hybrid AF / DF has been proposed to improve the above problems of AF and DF. According to the hybrid forwarding technique, if it is determined that the signal received from the source is error free, the relay performs DF-based relay, otherwise, it performs AF-based relay. However, in a bad channel environment, AF-based relay amplifies and transmits not only an error signal but also added noise, so that the decoding performance of the destination device is inevitably degraded. In addition, according to the hybrid forwarding scheme, like the DF scheme, since the repeater performs forwarding after decoding, the destination device receives the corresponding signal (that is, the forwarded signal) due to the decoding delay in the repeater. Until now, there is a disadvantage in that it leads to a considerable period of latency compared to the AF technique.

Meanwhile, in order to improve decoding performance and channel capacity in a cooperative relay system, a distributed turbo codes (DTC) technique has recently been proposed. The DTC technique theoretically has a performance close to the outage error probability bound, but since the repeater assumes perfect DTC, the channel situation between the source device and the repeater is the outage channel situation. It is not an effective technique. Thus, to overcome this drawback, DTC-SIR (soft information relaying) techniques are described in Y. Li et al, "Distributed turbo coding with soft information relaying on multi-hop relaying networks," IEEE JSAC., Vol. 24, pp. 2040-2050, Nov. In the paper specified in 2006. The information described in this paper is incorporated herein within the scope of the present invention.

The DTC-SIR technique combines the DTC technique and the SIR technique and calculates a posteriori probability (APP) of the received signal instead of deterministically determining the signal received from the repeater (ie, hard decision). The determination information obtained by the transfer is delivered to the destination device. Therefore, the DTC-SIR technique does not need to assume perfect decoding at the repeater, and can obtain significant decoding performance gains compared to the conventional DTC technique, especially when the channel condition between the source device and the repeater is not good.

On the contrary, since the channel environment between the source device and the repeater is very good, the delayed transmission information is transmitted to the destination device even when there is almost no error in the signal received by the repeater. There is a disadvantage that the decoding performance in the device may deteriorate.

The cooperative relay system performs data reception processing using a first signal transmitted by a source device by a source device and a second signal (signal generated by receiving / processing a first signal) transmitted by at least one repeater. As a communication system that can obtain diversity gain through cooperative communication (ie, forwarding) of a repeater, channel capacity enhancement and coverage expansion (Long Term Evolution) -Advanced environment can be used for coverage extensions).

1 is a diagram illustrating a cooperative relay system.

Although the cooperative relay system 100 illustrated in FIG. 1 includes a source device 110, one repeater 120, and a destination device 130, the disclosed technology may be applied to a cooperative relay system having a plurality of repeaters. Applicability is well understood by those working in this field. In addition, the cooperative relay system 100 illustrated in FIG. 1 may be configured to provide a mobile station with a source device 110 and a destination device 130 on the assumption of uplink transmission of a cellular communication system (eg, LTE-Advanced). And a base station, the disclosed technique can be applied to downlink transmission of a cellular communication system without being limited thereto, but also applicable to a communication system other than a cellular communication system. I can understand.

In the cooperative relay system 100 according to an embodiment, an error detection encoding technique, a first error correction encoding technique, and a second error correction encoding technique are used.

In one embodiment, a first codeword generated according to the first error correction coding scheme and a second codeword generated according to the second error correction coding scheme may include an iterative MAP (Maximum A posteriori) decoding algorithm. Construct a codeword that can be applied. Examples of codewords to which the iterative MAP decoding algorithm may be applied include codewords according to convolutional turbo codes and codewords according to block turbo codes, but are not limited thereto. For example, when the cooperative relay system 100 uses a convolutional turbo code, the first error correction coding scheme converts the input information bits into an error correction code, for example, a recursive systematic convolutional (RSC) code. Encoding, to generate systematic symbols and parity symbols, wherein the second error correction encoding technique interleaves input information bits, encodes the interleaved information bits into the error correction code, and generates a systematic symbol. And parity symbols are generated.

In one embodiment, the error detection coding scheme is a cyclic redundancy check (CRC) code based coding scheme. On the other hand, it can be fully understood by those skilled in the art that various error detection codes such as BCH codes other than the CRC code may be used in the cooperative relay system according to the present invention.

The source device 110 generates and generates a code symbol block composed of code symbols by applying an error detection encoding scheme and a first error correction encoding scheme to the information bits b ₁ , b ₂ ,..., And b _l . The first signal including the coded symbol block is transmitted.

As an example of a method of applying the error detection encoding scheme and the first error correction encoding scheme to the information bits b ₁ , b ₂ ,..., And b _l , the information bits b ₁ , b ₂ ,. claim to _l) of the CRC code symbol in the _{(a 1, a 2, ...} , a m) inserted in the resulting stream (b _1, b _2, a _{..., b l, a 1,} a 2, ..., a m) 1 is a method of applying an error correction encoding technique, generating error correction code symbols by applying a first error correction encoding technique to information bits (b ₁ , b ₂ ,..., B _l ), but generated error correction code symbols A method of inserting CRC code symbols (a ₁ , a ₂ ,..., A _m ) into a slot may be included, but is not necessarily limited thereto. Hereinafter, in order to explain the error correction decoding scheme for the sake of convenience, the contents of the CRC code symbol insertion will be omitted from the equation development for convenience.

The source device 110 encodes the information bits b ₁ , b ₂ ,..., B _k ..., B _l into an RSC code having a code rate of 1/2 to generate a code symbol block C. Here, when ignoring the number of trellis termination bits, C = ( C ₁ , C ₂ ,…, C _k ,…, C _l ), C _k = (i _k , p _k ), i _k = b _k to be.

Here, when applying a BPSK-based modulation scheme to code symbols (eg, i _k , p _k ), the set of modulated signals is S = ( S ₁ , S ₂ ,..., S _k , ..., S _l ), and each element may be represented by S _k = (s ⁱ _k , s ^p _k ), s ⁱ _k , s ^p _k ∈ {-1, 1}. In this case, the first signal transmitted from the source device 110 is composed of a series of s ⁱ _k , s ^p _k , and the first signal y _SR received from the repeater 120 may be represented by Equation 1, The first signal y _SD received by the destination device 130 may be represented by Equation 2. For reference, Equations 1 and 2 omits symbol indices (eg, k) and indices (i, p) regarding parity.

Here, P _S denotes the power of the signal transmitted from the source device 110, and h _SR and n _SR denote the fading coefficient and addability for the channel link between the source device 110 and the repeater 120, respectively. It represents Gaussian noise and h _SD and n _SD represent attenuation coefficients and additive Gaussian noise for the channel link between the source device 110 and the destination device 130, respectively.

In one embodiment, repeater 120 transmits a second signal to destination device 130. Here, the second signal includes determination information for each of the code symbols of the second error correction encoding scheme estimated based on a result of decoding the first signal received by the repeater. In one embodiment, the second signal is a soft decision signal or a hard decision signal. The soft decision signal and the hard decision signal will be described later.

In another embodiment, the repeater 120 transmits the second signal only when a request for transmission of the second signal is received from the destination device 130.

2 is a flowchart illustrating a method of operating a repeater according to an embodiment.

Referring to FIG. 2, the repeater 120 receives a first signal in S210.

를 획득하는 제1 과정; 및 상기 복호화된 결과 즉,

와 CRC 부호 심벌들을 기초로 순환 잉여 검사를 수행하여 오류가 검출되는지를 판단하는 제2 과정을 수행한다.In S220, the repeater 120 decodes the received first signal (for example, a signal represented by Equation 1) to determine whether an error is detected. In one example, the repeater 120 decodes the received first signal by a decoding technique corresponding to the first error correction encoding technique, which is an estimate of information bits.

A first process of obtaining; And the decoded result, i.e.

And a second process of determining whether an error is detected by performing a cyclic redundancy check based on the CRC code symbols.

을 획득하는 방법, MAP 복호 알고리즘을 사용하여 수학식 3으로 표현되는 정보 비트별 사후 확률(A Posteriori Probability : 이하, APP)을 산출하고, 산출된 정보 비트별 APP을 기초로 경판정(예컨대, 해당 정보 비트가 가질 수 있는 값들 중 APP이 높은 값을 선택)하여

을 획득하는 방법을 들 수 있다.Here, as an example of a method of performing the first process, using a Viterbi decoding algorithm

A posteriori probability (hereinafter, referred to as APP) represented by Equation 3 is calculated using a MAP decoding algorithm, and a hard decision (eg, corresponding to Among the values that the information bit can have, the APP selects a high value)

And a method of obtaining the same.

In Equation 3, h is a constant to make the sum of APP equal to 1, m and m 'are pairs of states that change according to input bits, and M _s represents the number of states in the grid. In addition, γ _k (m, m '), α _k (m'), and β _k (m) each represent a branch metric, forward state metric, and backward state metric. It can be represented by the equations (4) to (6).

In S230, the repeater 120 transmits a soft decision signal to the destination device 130 when an error is detected in S220. Here, the soft decision signal includes soft decision information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the received first signal.

In one embodiment for S230, the repeater 120 comprises a first process of soft decision decoding the received first signal with a MAP decoding algorithm to generate a post-probability for each information bit that can be represented by Equation 3; Based on the relationship between the first error correction encoding technique and the second error correction encoding technique and the calculated post-probability for each information bit, probability information each of the code symbols of the second error correction encoding technique may have a value. Generating a second process; And a third process (ie, a modulation process) of transmitting the soft decision signal including the generated probability information as the soft decision information.

가 양수이면 상기 제2 오류 정정 부호화 기법의 k번째 패리티 심벌

=1일 확률이

=0일 확률보다 큼을 의미하며

의 절대값은

=1일 확률과

=0일 확률 간의 상대적인 크기 값을 나타낸다.In this case, the first encoding scheme is an encoding scheme for generating systematic symbols and parity symbols by encoding input information bits with an error correction code (for example, an RSC code), and the second encoding scheme includes input information bits. In the case of an encoding scheme for interleaving the symbols and encoding the interleaved information bits with the error correction code (for example, an RSC code) to generate systematic symbols and parity symbols, the second process is represented by Equation (7). Probability information (ie, soft decision parity symbols) for values each of the code symbols of the second error correction encoding scheme may have is generated. In one example, according to equation (7)

Is a positive k-th parity symbol of the second error correction coding scheme

Is = 1

Greater than the probability of being 0

The absolute value of

= 1 probability

Represents the relative magnitude value between the probability of being 0.

의 APP는 수학식 8로 산출될 수 있다.In other words, the probability value in Equation 7,

APP can be calculated by Equation 8.

는 패리티 심벌

이

인 가지(branch)를 가지게 하는 k-1번째 상태들의 집합을 의미하고,

는 패리티 심벌

이

을 가질 때

에 대응되는 시스터메틱 심벌을 의미한다. 또한,

은 시간 k에서

의 APP을 나타내며 수학식 3의 산출 결과를 이용하여 얻을 수 있다. 또한,

는 수학식 9를 이용하여 산출될 수 있다.In equation (8)

The parity symbol

this

Means a set of k-1th states that have a branch,

The parity symbol

this

When you have

It means the systematic symbol corresponding to. Also,

Is at time k

Denotes APP and can be obtained by using the calculation result of Equation 3. Also,

May be calculated using Equation 9.

는 각각 b(m,m')의 APP와 시간 k-1에서의 상태가 m'일 확률을 나타낸다.In Equation 9, b (m, m ') means an information bit for moving from state m to state m', Wow

Denotes the probability that m 'is the state at APP and time k-1 of b (m, m'), respectively.

을

에 대응되는 정확한 패리티 심벌이라 할때, 연판정 패리티 심벌은

로 표현될 수 있다. 여기서,

는 수학식 10로 표현되는 평균 값과 수학식 11로 표현되는 분산 값을 가진 등가 잡음이다.On the other hand, in equation (7)

of

When the correct parity symbol corresponds to the soft decision parity symbol

It can be expressed as. here,

Is an equivalent noise having an average value represented by Equation 10 and a variance value represented by Equation 11.

를 그대로 전송하는 대신, 수학식 12의 관계식을 가진 정규화 요소(normalization factor) α를

에 곱하여 전송할 수 있다.In one embodiment, repeater 120 is

Instead of transmitting as is, the normalization factor α having the relation

Multiply by to send.

In Equation 12, PR means power transmitted from the repeater 120.

에 곱하여 전송할 경우, 목적지 기기(130)에서 수신되는 연판정 신호는 수학식 13으로 표현될 수 있다.Α at the repeater 120

In the case of multiplying by, the soft decision signal received by the destination device 130 may be represented by Equation 13.

는 0의 평균 값과

의 분산 값을 갖는 등가 잡음이다.In Equation 13,

Is the average value of 0 and

Equivalent noise with a variance of

In S240, when an error is not detected in S220, the hard decision signal is transmitted to the destination device 130. Here, the hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme estimated based on the result of decoding the received first signal.

을 생성하는 제1 과정, 상기 경판정 비트들에 상기 제2 오류 정정 부호화 기법을 적용하여 상기 제2 오류 정정 부호화 기법의 부호 심벌들 각각에 대한 값

을 생성하는 제2 과정, 및 상기 생성된 값을 경판정 정보로서 포함하는 경판정 신호

를 송신하는 제3 과정(예컨대, 변조 과정)을 수행한다. 이때, 상기 제1 부호화 기법은 입력되는 정보 비트들을 오류 정정 부호(예컨대, RSC 부호)로 부호화하여, 시스터메틱 심벌들과 패러티 심벌들을 생성하는 부호화 기법이고, 상기 제2 부호화 기법은 입력되는 정보 비트들을 인터리빙하고, 상기 인터리빙된 정보 비트들을 상기 오류 정정 부호(예컨대, RSC 부호)로 부호화하여, 시스터메틱 심벌들과 패러티 심벌들을 생성하는 부호화 기법인 경우, 제2 과정은 상기 경판정 비트들

을 인터리빙하는 제1 부과정, 상기 인터리빙된 경판정 비트들

을 상기 오류 정정 부호로 부호화하여

를 생성하는 제2 부과정을 포함할 수 있다.In one embodiment for S240, the repeater 120 hard decision decoding the received first signal to hard decision bits

In a first step of generating a value, a value for each of the code symbols of the second error correction encoding scheme is applied by applying the second error correction encoding scheme to the hard decision bits.

A second process of generating a and a hard decision signal comprising the generated value as hard decision information

Performs a third process (eg, a modulation process) of transmitting. In this case, the first encoding scheme is an encoding scheme for generating systematic symbols and parity symbols by encoding input information bits with an error correction code (for example, an RSC code), and the second encoding scheme includes input information bits. In the case of an encoding scheme of interleaving the symbols and encoding the interleaved information bits with the error correction code (eg, an RSC code) to generate systematic symbols and parity symbols, the second process may include the hard decision bits.

A first sub-process of interleaving the interleaved hard decision bits

Is encoded by the error correction code

It may include a second sub-process for generating a.

According to the transmission of the hard decision signal according to S240, the second signal received by the destination device 130 may be represented by Equation 14.

In Equation 14, the symbol index (k) and the index (i, p) for parity or not are omitted for convenience.

In an embodiment, the operation corresponding to S230 and the operation corresponding to S240 may be performed only when a second signal is requested from a destination device 130, for example, when a Not Acknowledgment (NAK) signal is received. Can be.

In another embodiment, when the operation corresponding to S230 and the operation corresponding to S240 are received an acknowledgment (ACK) signal from the destination device 130, the repeater 120 is a second signal (that is, soft decision) Signal or hard decision signal).

3 is a flowchart illustrating a method of operating a destination device, according to an exemplary embodiment.

Referring to FIG. 3, the destination device 130 receives a first signal in S310.

In S320, the destination device 130 decodes the received first signal (eg, a signal represented by Equation 1) to determine whether an error is detected. The method of determining whether an error is detected according to S320 is the same as the method described in S220 (for example, when Equations 3 and 4 are used, subscripts indicated by SR are replaced with SD).

를 상위 계층으로 올리고 다음 패킷의 수신을 대기한다.If no error is detected (S320), the process proceeds to S350 where the destination device 130 estimates the information bits.

To the upper layer and wait for the next packet to be received.

If an error is detected (S320), the process proceeds to S330 and the destination device 130 requests the relay 120 to transmit the second signal.

를 획득한다. 일실시예에 있어서, S340에서 사용되는 복호화 기법은 반복적인 MAP 복호화 기법이며, 도 4 및 도 5를 참조하여 후술한다.In S340, the destination device 130 receives the second signal, decodes the received first and second signals, and estimates information bits.

Acquire it. In one embodiment, the decoding technique used in S340 is an iterative MAP decoding technique, which will be described later with reference to FIGS. 4 and 5.

4 is a block diagram schematically illustrating a signal processing procedure of a cooperative relay system.

The source device 110 applies an error detection encoding technique and a first error correction encoding technique to the information bits, and generates an encoder 410 for generating a code symbol block and a modulator for generating a first signal including the generated code symbol block. 420.

The repeater 120 decodes the first signal to perform error detection, a decoder 430 for generating hard decision bits, an interleaver 432 for interleaving the generated hard decision bits, and error correction for the interleaved hard decision bits. An encoder 434 for generating a code symbol block by encoding with a code (for example, an RSC code), a modulator 434 for generating a hard decision signal including the generated code symbol block, and calculating an APP from the first signal. And a soft decision parity symbol calculator 442 for generating a soft decision signal including a soft decision parity symbol calculated by calculating a soft decision parity symbol based on the calculated APP. Here, when no error is detected in the decoder 430, the APP calculator 440 and the soft decision parity symbol generator 442 may not operate. When the error is detected in the decoder 430, the interleaver 432, encoder 432, and modulator 434 may not be operated.

The destination device 130 includes an iterative decoder 450 that supports an iterative MAP decoding algorithm.

5 is a block diagram for describing an operation of the iterative decoder 450.

Referring to FIG. 5, the first MAP decoder 510 performs MAP decoding based on extrinsic information generated and deinterleaved by the first signal and the second MAP decoder 520 to perform the external information and the APP ( Or Log Likelihood Ratio) to the interleaver 530 and the determination unit 550, respectively. Also, the second MAP decoder 520 outputs the deinterleaver 540 by performing MAP decoding based on the second signal and the external information generated by the first MAP decoder 510 and interleaved. Since the overall process illustrated in FIG. 5 may be implemented by the BCJR MAP algorithm, a detailed description thereof will be omitted and only the metric will be described later.

The branch metric used in the first MAP decoder 510 may be calculated by using an equation in which subscript SR is replaced with SD in Equation 4, and the branch metric used in the second MAP decoder 520. When the hard decision signal is input can be calculated using Equation 15, when the soft decision signal is input can be calculated using Equation 16.

를 획득한다.On the other hand, if an error is not detected, one MAP decryption is performed. If an error is detected, the MAP decryption is repeatedly performed for a predetermined number of repetitions, and then the determination unit 550 determines the input APP (or Log Likelihood). Hard decision based on the

Acquire it.

6 illustrates a time series procedure performed in a cooperative relay system according to an embodiment.

In the present embodiment, a sub-frame index is indicated on the left side on the premise that the source device 110 and the repeater 120 perform transmission in a time division multiple access (TDMA) scheme.

Referring to FIG. 6, in subframe n, the source device 110 transmits a first signal to the repeater 120 and the destination device 130 (S610). The target device 130 performs decoding in response to receiving the first signal (S620_B). Assuming a decoding delay of 3 ms and one subframe delay time of 1 ms, the destination device 130 can determine whether an error is detected in subframe n + 4. If no error is detected, the destination device 130 terminates early by transmitting an ACK signal to the repeater 120, and if an error is detected, the destination device 130 transmits a NAK signal (S630_B). Similarly, the repeater 120 also determines whether an error is detected (S620_A), determines a format of the second signal (ie, a hard decision signal or a soft decision signal) to be transmitted to the destination, and generates a second signal having the determined format. (S622_A).

When the repeater 120 receives the NAK signal in the subframe n + 5, the generated second signal is transmitted to the destination device 130 (S630_A). The destination device 130 receiving the second signal performs repetitive MAP decoding (S640_B). In subframe n + 9, the destination transmits an ACK signal to the repeater and transmits a signal for one frame (or packet). Terminate (S650_B).

If no error is detected in S620_B, the average delay time may be shortened because early termination may be performed by transmitting an ACK signal.

7 shows a simulation environment for performance comparison with existing techniques. Considering the uplink transmission, because the repeater is fixed near the base station forwards the signal received from the terminal to the base station in the channel state of the line of sight (LOS). On the other hand, since the position of the mobile station is variable, unlike the repeater, the transmission power is always changed. The size of the frame is 130 symbols, and transmitted frames pass through a quasi-static attenuation channel (i.e., a channel that is constant in one frame period and has random characteristics independently between frames). As the error correction code, an RSC code having a code rate of 1/2 and a generator matrix of (1, 5/7) was used.

8 illustrates bit error rate (BER) performance of a repeater protocol (Adaptive HARQ) and other repeater protocols (Hybrid AF / DF, Hard DF, Soft DF) according to an embodiment. Referring to FIG. 8, it can be seen that the proposed scheme, that is, the adaptive HARQ scheme, has better BER performance than the other schemes. In addition, it can be seen that the adaptive HARQ technique has a code gain according to the use of DTC, and thus, has a better performance than the hybrid AF / DF technique using AF. In addition, when compared to the pure hard DF technique (that is, the method of transmitting only hard decision signals), an error in the repeater can be prevented from propagating to the destination device. In addition, unlike the pure soft DF technique (that is, the method of transmitting only the soft decision signal), the adaptive ARQ technique shows that the repeater transmits the hard decision signal at a high SNR with a low probability of error. It can be seen that excellent.

9 illustrates BER performance of a repeater protocol (Hybrid hard / soft DF) and the existing repeater protocols (AF, DF) according to an embodiment. Referring to FIG. 9, it can be seen that the proposed technique, that is, hybrid hard / soft DF technique, has better BER performance than the other techniques. This superior BER performance is attributed to the characteristics of Hybrid hard / soft DF, which does not generate error propagation unlike the DF technique and that the added noise is not amplified unlike the AF technique.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. The computer readable recording medium includes all kinds of recording devices in which packets which can be read by a computer system are stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

The inventors of the present invention have been described with reference to the embodiments shown in the drawings for clarity, but this is merely exemplary, and those skilled in the art may various modifications and other equivalent embodiments therefrom. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

Embodiments of the present invention presented above may have an effect including the following advantages. However, all the embodiments of the present invention are not meant to include them all, and thus the scope of the present invention should not be understood as being limited thereto.

It is possible to provide a cooperative relay system having a short average delay time and excellent decoding performance (eg, bit error rate performance).

1 is a diagram illustrating a cooperative relay system.

2 is a flowchart illustrating a method of operating a repeater according to an embodiment.

3 is a flowchart illustrating a method of operating a destination device, according to an exemplary embodiment.

4 is a block diagram schematically illustrating a signal processing procedure of a cooperative relay system.

5 is a block diagram illustrating the operation of an iterative decoder.

6 illustrates a time series procedure performed in a cooperative relay system according to an embodiment.

7 shows a simulation environment for performance comparison with existing techniques.

8 illustrates bit error rate (BER) performance of a repeater protocol (Adaptive HARQ) and other repeater protocols (Hybrid AF / DF, Hard DF, Soft DF) according to an embodiment.

9 illustrates BER performance of a repeater protocol (Hybrid hard / soft DF) and the existing repeater protocols (AF, DF) according to an embodiment.

Claims (23)

A method of operating a destination device in a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. The first signal includes a code symbol block generated by applying an error detection encoding technique and a first error correction encoding technique to information bits. (a) receiving the first signal; (b) decoding the received first signal to determine whether an error is detected; (c) if an error is detected in step (b), requesting the repeater to transmit a second signal; And (d) receiving the second signal and decoding the received first and second signals to estimate the information bits, And the second signal includes determination information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the first signal received by the repeater. The method of claim 1, The second signal includes any one of a hard decision signal and a soft decision signal, The hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme. Wherein the soft decision signal includes soft decision information for each of the code symbols of the second error correction coding scheme. The method of claim 2, The hard decision information includes a value of a corresponding sign symbol, The soft decision information includes probability information on a value that a corresponding code symbol may have. The method of claim 2, The first error correction encoding technique is an encoding technique for encoding input information bits with an error correction code to generate systematic symbols and parity symbols, The second error correction encoding technique is an encoding technique for interleaving input information bits and encoding the interleaved information bits with the error correction code to generate systematic symbols and parity symbols, The hard decision signal includes hard decision information for each of the systematic symbols and parity symbols of the second error correction coding scheme. And the soft decision signal includes soft decision information for each of the parity symbols of the second error correction coding scheme. The method of claim 4, wherein the error correction code, And a recursive systematic convolutional code. The method of claim 1, A first codeword generated according to the first error correction coding scheme and a second codeword generated according to the second error correction encoding scheme may be codewords to which an iterative MAP decoding algorithm may be applied. How to configure. The method of claim 6, The second signal includes any one of a hard decision signal and a soft decision signal, The hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme. Wherein the soft decision signal includes soft decision information for each of the code symbols of the second error correction coding scheme. The method of claim 6, And (d) comprises applying the iterative maximal MAP decoding algorithm on the received first and second signals to estimate the information bits. The method of claim 1, And if an error is not detected in step (b), transmitting an accept signal to at least one of the source device and the repeater. 10. The method of claim 9, The accept signal sent to the repeater is used to indicate that the transmission of the second signal is not necessary. The method of claim 1, The error detection coding scheme is a cyclic redundancy check code based coding scheme, In step (b), (b1) decoding the received first signal by a decoding technique corresponding to the first error correction encoding technique; And (b2) determining whether an error is detected by performing a cyclic redundancy check based on the result decoded in (b1). A method of operating the destination device in a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal. The first signal includes a code symbol block generated by applying an error detection encoding technique and a first error correction encoding technique to information bits. (a) receiving the first signal; (b) receiving a second signal transmitted from the repeater; And (c) decoding the received first and second signals to estimate the information bits, The second signal is a signal selected from the hard decision signal and the soft decision signal based on an error detection result according to the error detection coding scheme in the repeater, The hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the first signal received by the repeater. The soft decision signal includes soft decision information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the first signal received by the repeater. The method of claim 12, wherein the second signal, And the hard decision signal if no error is detected in the repeater, and the soft decision signal if an error is detected in the repeater. The method of claim 12, The first error correction encoding technique is an encoding technique for encoding input information bits with an error correction code to generate systematic symbols and parity symbols, The second error correction encoding technique is an encoding technique for interleaving input information bits and encoding the interleaved information bits with the error correction code to generate systematic symbols and parity symbols, The hard decision signal includes hard decision information for each of the systematic symbols and parity symbols of the second error correction coding scheme. And the soft decision signal includes soft decision information for each of the parity symbols of the second error correction coding scheme. The method of claim 12, A first codeword generated according to the first error correction coding scheme and a second codeword generated according to the second error correction encoding scheme may be codewords to which an iterative MAP decoding algorithm may be applied. How to configure. The method of claim 15, The step (c) includes estimating the information bits by applying an iterative maximum iterative MAP decoding algorithm on the received first and second signals. The method of claim 12, wherein step (b) comprises: (b1) determining whether an error is detected by decoding the received first signal; (b2) if an error is detected in step (b), requesting the repeater to transmit the second signal; And (b3) receiving the second signal. A method of operating the repeater in a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal, The first signal includes a code symbol block generated by applying an error detection encoding technique and a first error correction encoding technique to information bits. (a) receiving the first signal; (b) decoding the received first signal to determine whether an error is detected; (c) if an error is detected in step (b), transmitting a soft decision signal to the destination device; And (d) if an error is not detected in step (b), transmitting a hard decision signal to the destination device, The hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the received first signal. The soft decision signal includes soft decision information for each of the code symbols of the second error correction encoding technique estimated based on a result of decoding the received first signal. The method of claim 18, wherein step (d) (d1) hard decision decoding the received first signal to generate hard decision bits; (d2) generating a value for each of the code symbols of the second error correction encoding scheme by applying the second error correction encoding scheme to the hard decision bits; And (d3) transmitting a hard decision signal comprising the generated value as hard decision information. The method of claim 19, The first encoding scheme is an encoding scheme for generating systematic symbols and parity symbols by encoding input information bits with an error correction code. The second encoding technique is an encoding technique for interleaving input information bits and encoding the interleaved information bits with the error correction code to generate systematic symbols and parity symbols, Step (d2) is Interleaving the hard decision bits; And Encoding the interleaved hard decision bits with the error correction code to generate a value for each of the code symbols of the second error correction coding scheme. The method of claim 18, wherein step (c) is (c1) soft decision decoding the received first signal to generate post probability information; (c2) based on the relationship between the first error correction encoding technique and the second error correction encoding technique and the generated post probability information, for a value each of the code symbols of the second error correction encoding technique may have; Generating probability information; And (c3) transmitting a soft decision signal comprising the generated probability information as the soft decision information. A method of operating the repeater in a communication system comprising a destination device, a source device for transmitting a first signal to the destination device, and a repeater capable of receiving and processing the first signal, The first signal includes a code symbol block generated by applying an error detection encoding technique and a first error correction encoding technique to information bits. (a) receiving the first signal; And (b) transmitting the second signal in response to receiving the second signal from the destination device; And the second signal includes determination information for each of the code symbols of the second error correction coding scheme estimated based on a result of decoding the first signal received by the repeater. The method of claim 22, Determining whether an error is detected by decoding the received first signal; In step (b), Transmitting a soft decision signal to the destination device when an error is detected in the determining step; And If an error is not detected in the determining, transmitting a hard decision signal to the destination device, The hard decision signal includes hard decision information for each of the code symbols of the second error correction coding scheme. Wherein the soft decision signal includes soft decision information for each of the code symbols of the second error correction coding scheme.

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