KR20090026965A - System for cooperative relaying without reducing spectral efficiency - Google Patents

Abstract

A cooperative relaying system without reducing spectral efficiency is provided to prevent spectral efficiency from being lowered in comparison to a direct transmission method. A source(S) transmits the N-1 information to a relay(R) and a destination(D) during the N-1 frame time. N is an even number larger than 1. The source transmits the N information to the destination during the N frame time after the N-1 frame time. The relay transmits demodulated N-1 information about the N-1 information transmitted from the source during the N-1 frame time to the destination during the N frame time. An operation in which the N information is transmitted from the source to the destination and an operation in which the demodulated N-1 information is transmitted from the relay to the destination are simultaneously performed during the N frame time.

Description

System for cooperative relaying without reducing spectral efficiency

The present invention relates to a cooperative relay system in which the spectral efficiency is not deteriorated. More specifically, the present invention relates to a cooperative relay system in which the source and the relay can be operated simultaneously. An improved cooperative relay system is provided in which efficiency is not deteriorated.

In general, according to the configuration in which multiple antennas are arranged in the transmitter and the receiver, the spatial diversity characteristics of the wireless communication can be improved and the fading can be effectively reduced on the wireless communication path. There is this.

However, wireless mobile terminal communication cannot support multi-type multiple antennas due to its physical size, power capacity limitations, and other constraints. It is not being developed.

In order to overcome this limitation, a new technique called cooperative communication has been proposed, and according to the cooperative communication, a gain and an effect of the above-mentioned transmission diversity are created by using a selective relay method using a relay between a transmitter and a receiver. And allow mobile communication with a single antenna.

This cooperative communication will be described in more detail with reference to FIG. 1 as follows.

Prior to the description, λ _ij shown in FIG. 1 is defined by [λ _ij = (d _SD / d _ij ) ^η ], where d _ij is the distance between the transmitting side i and the receiving side j, i∈ {S, R}, j∈ {R, D}, and η corresponds to the path loss index, and may be generally selected within the range of 1 to 7.

For example, λ _SR may be defined as λ _SR = (d _SD / d _SR ) ^η as a degree of dispersion between the source S: 10 on the transmitting side and the relay R: 20 on the receiving side, and the value η selected. The value can be changed accordingly.

FIG. 1 is a diagram illustrating a general double-hop network cooperative communication in which a source S 10 transmits information to a destination D 30 by cooperation of a relay R 20.

The source (S; 10), the destination (D; 30), and the relay (R; 20) are each a transmitter on a wireless network, a receiver receiving information from a transmitter, and relaying the transmitter and the receiver to transmit information of the transmitter to the receiver. Corresponds to the repeater retransmitting to the side.

Here, the cooperative relay (CR) is a first step of transmitting the information of the source (S; 10) to the relay (R; 20) and the relay (R; 20) receiving the information received from the source (S; 10). Relaying and retransmitting to the destination.

More specifically, first, during the first frame time (the first step) as shown in FIG. 1B, the source S 10 transmits a signal a to be transmitted to the relay R; 20) and the destination (D; 30) at the same time, the relay (R) 20 and the destination (D; 30) receives the signal (a) transmitted from the source (S; 10).

During the second frame time (the second step) after the first frame time, the relay R 20 demodulates and demodulates the received signal a as shown in FIG. The signal (a ') is transmitted to the destination (D; 30), and the destination (D; 30) receives the signal (a) received from the source (S; 10) and the relay (R; 20). After the signals a 'are respectively combined by MRC (Maximum Ratio Combining) or the like, the signal a' is restored to the original signal.

Here, during the second frame time, the relay (R) 20 determines whether to transmit the signal (a) to the destination (D) 30, that is, whether to retransmit by a predetermined criterion to meet the predetermined criterion. Can only selectively retransmit the demodulated signal (a ') to the destination (D) 30 side, which is commonly referred to as selective transmission (relay) or selective relay (SR) of the relay. Doing.

The selective relay SR is one of the simple cooperative communication protocols, and the relay R 20 independently performs the determination as to whether to decode and transmit the information transmitted from the source S 10 as described above. Done.

Accordingly, the selective relay method using the relay R is one of relatively simple cooperative communication protocols that can realize the effects of physical multiple antennas.

That is, in the case of using the cooperative communication as shown in FIG. 1, a spatial diversity effect such as using a virtual multiple antenna for the transmitter and the receiver is obtained by using a single antenna without physically disposing the antennas on the transmitter and the receiver in a wireless communication environment. Can be.

However, according to the conventional cooperative relay (CR), only the source (S; 10) is operated during the first frame time, which is the first step, to the relay (R) 20 (for example, the first information (x). ₁ )), and during the second frame time, which is the second step, only the relay R 20 operates to demodulate the received information (the first signal x ₁ ) and retransmit it to the destination D 30. .

Of course, the second signal x ₂ corresponding to the next information to be transmitted is transmitted and processed for the third frame time and the fourth frame time according to the same principle as described above.

On the other hand, in the case of the direct transmission (DT) before the cooperative relay, only the source (S; 10) and the destination (D: 30) are configured without the relay, and the source (S; 10) is the first frame. The first information x ₁ may be transmitted to the destination D 30 during the time period, and the second information x ₂ may be transmitted to the destination D 30 during the next second frame time.

That is, the direct transmission method DT can transmit two signals (for example, two bits) for two frame times.

On the other hand, in the cooperative relay (CR) system as shown in FIG. 1, the spatial diversity characteristic can be improved compared to the direct transmission method (DT) by using the configuration of the relay (R) 20. Only one signal (for example, 1 bit) can be transmitted during one frame time and the second frame time.

Accordingly, in the conventional cooperative relay system as shown in FIG. 1, since only one source (S; 10) or one relay (R; 20) operates in one frame time, the existing direct transmission method (DT) is based on the same time. ), The spectrum efficiency is lowered, and the information transmission time is increased.

The present invention has been made to solve the above-mentioned problems, and while the source transmits information to the destination side, the relay simultaneously operates as the source and relay transmit a demodulated signal related to the signal received from the source in the previous step to the destination side. The purpose of the present invention is to provide a cooperative relay system that can increase information transmission efficiency without deteriorating spectral efficiency in comparison with a direct transmission (DT) based on the same time.

In the cooperative relay system in which the spectral efficiency of the present invention for achieving the above object is not deteriorated, a relay (R) for relaying between the source (S), the destination (D) and the source (S) and the destination (D). In the cooperative relay system consisting of the above, the source (S), the N-1 information to the relay (R) and the destination (D) side for the N-th frame time (N is an even number including 2) And N-th information to the destination (D) side for the N-th frame time after the N-th frame time, and the relay (R) is the previous frame time during the N-th frame time. When the demodulated N-th information about the N-th information received from the source S is transmitted to the destination D at the N-1 frame time, the destination D is transmitted from the source S. ) The N-th information is transmitted to the () side, and from the relay (R) to the destination (D) side The operation of transmitting the demodulated N-th information is performed simultaneously for the N-th frame time.

Further, during the Nth frame time, the destination D may distinguish the Nth information received from the source S and the demodulated N-1 information received from the relay R as an original signal. Can be recovered.

Here, during the Nth frame time, when the destination D recovers the Nth information received from the source S, the destination D interferes with the demodulated N-1 information received from the relay R. In case of recovering the demodulated N-th signal received from the relay R and recovering the demodulated N-1 signal received from the relay R, it is determined that the signal is an interference signal. It is desirable to recover individually in the state excluding the interference signal by judging to be.

According to the cooperative relay system in which the spectral efficiency does not decrease according to the present invention, while the source transmits the information to the destination side, the relay transmits the demodulated signal about the signal received from the source in the previous step to the destination side at the same time. In comparison with the conventional direct transmission (DT), the spectrum efficiency does not decrease, information transmission and processing time can be reduced, and information transmission efficiency in cooperative communication can be greatly improved.

In addition, the destination may independently and smoothly recover each signal by distinguishing the information received from the source and the information received from the relay to recover the original signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

2 is a schematic diagram of a cooperative relay system in which spectral efficiency is not deteriorated according to an embodiment of the present invention, FIG. 3 is a conceptual diagram of FIG. 2, and FIGS. 4 to 5 are performances of a cooperative relay system according to the configuration of FIG. 2. A graph representing.

The present invention is a cooperative communication method consisting of a source (S; 110), a destination (D; 130) and a relay (R; 120) relaying between the source (S; 110) and the destination (D; 130). On the cooperative relay of FIG. 2, the operation of the source S 10 and the relay R 20 can be simultaneously performed, and the spectral efficiency is lowered compared to the conventional direct transmission method based on the same time. To an improved cooperative relay system.

That is, referring to FIG. 2 or FIG. 3, the source S 110 may include the relay R 120 and the destination D 130 during an N-1th frame time (N is an even number including 2). N-th information is transmitted to the N-th side, and N-th information is transmitted to the destination (D) 130 during the N-th frame time after the N-th frame time.

In addition, the relay (R) 120 performs demodulation on the N-th information received from the source (S; 110) at the N-th frame time, which is the previous frame time, during the N-th frame time. The N-1 information is transmitted to the destination D 130.

For example, when N = 2, the source S 110 simultaneously transmits the first information x ₁ to the relay R 120 and the destination D 130 for the first frame time. During the second frame time, the second information x ₂ is transmitted only to the destination D 130.

In addition, the relay R 120 demodulates the first information x ₁ received from the source S 110 at a previous first frame time during the second frame time, and demodulates the first information ( x ₁ ′) to the destination D 130.

Of course, the case of N = 4 may be performed through the same operation as described above with reference to the third frame section and the fourth frame section shown in FIG.

According to the above configuration, the operation of transmitting the N-th information (when N = 2, the second information (x ₂ )) from the source (S; 110) to the destination (D; 130) side, and the relay The demodulated N-th information (if N = 2, the demodulated first information (x ₁ ′)) is transmitted from () to the destination (D) 130 side, the N-th frame time (N). If = 2, it may be performed simultaneously during the second frame time.

In the case of the conventional direct communication method (DT), since there is no relay configuration, as the direct communication between the source and the destination is performed, the first information and the second information, that is, the two information are sequentially performed during the first frame time and the second frame time. Can be sent to.

In addition, in the case of the selective relay method of FIG. 1 proposed to have a configuration including a relay to improve the spatial diversity characteristic of the direct communication method DT, as described above in the background art, The first information, that is, only one information can be transmitted during the frame time and the second frame time.

However, in the present invention, since the first signal and the second information can be transmitted during the first frame time and the second frame time like the direct communication method DT, two signals, that is, can be transmitted based on the same frame time. Compared with the direct communication method (DT), there is an advantage that the spectrum efficiency is not degraded at all.

For reference, b / s / hz (bit per second per hertz) is used as a unit of the spectral efficiency.

That is, in the related art, as shown in FIG. 1, the first step of transmitting the information a to the relay R 120 and the destination D 130 and the relay R 120 to the destination R as shown in FIG. A second step of sequentially transmitting the demodulated signal a 'relating to the information to the D; 130 side, and the first and second steps as described above are also performed at the next information transmission after the information transmission. The same operation is repeated. In the case of FIG. 1, there is a problem in that the frequency efficiency is significantly lower than that of the direct communication method (DT).

However, according to the present invention, as the source (S; 110) and the relay (R; 120) can be operated simultaneously as shown in Fig. 2 or 3, compared to the direct communication method (DT) on the basis of the same time. Of course, the spectral efficiency does not decrease, as well as the information transmission and processing time can be shortened, and consequently, the information transmission efficiency in cooperative communication can be greatly improved.

On the other hand, in the system 100 of the present invention, the destination D during the N-th frame time, the N-th information received from the source (S) and the demodulated N-th received from the relay (R) -1 It is desirable to recover the original signal by dividing the information.

This prevents the interference between the 'N-th information' and the 'demodulated N-1 information' received during the N-th frame time, which is the corresponding frame time, so that the N-th and N-1 information signals This is to facilitate each recovery independently.

More specifically, the destination (D), when recovering the N-th information received from the source (S), the demodulated N-th information received from the relay (R) as an interference signal It can be determined and recovered individually in the state excluding the interference signal.

In addition, when restoring the demodulated N-1 signal transmitted from the relay R, the N-th information received from the source S is determined to be an interference signal, so that the N-th information received from the relay R may be individually recovered in the state excluding the interference signal. do.

Hereinafter, the system 100 of the present invention as described above will be described in more detail with reference to FIG. 2 or FIG. 3 and equations.

Prior to the description, λ _ij is defined by [λ _ij = (d _SD / d _ij ) ^η ]. Here, d _ij is the distance between the transmitting side i and the receiving side j, i ∈ {S, R}, j ∈ {R, D}, and η corresponds to the path loss index, usually 1 to 7 It can be selected within the range of.

For example, λ _SR may be defined as λ _SR = (d _SD / d _SR ) ^η as a degree of dispersion between the source S on the transmitting side and the relay R on the receiving side, and according to the value η selected. This can be changed.

On the other hand, i and j described in the following equations are i ∈ {S, R}, j ∈ {R, D}, respectively, i and j are the transmitting side (source or relay) and the receiving side (relay or destination). ) Respectively.

In the present invention, all temporal representations use discrete-time complex equivalent base-band models, and a signal modulated by the source S 110 may have a value of 1 or -1. It will be described in consideration of having a BPSK modulated signal. Such a model and a modulation method are employed for convenience of description and are not necessarily limited to the above description, and various methods may be applied within the technical scope of the present invention.

The present invention as described above will be described in more detail with reference to FIG. 2 or FIG. 3 with respect to the first frame time and the second frame time.

First, during the first frame time, the source S 110 transmits the first information x ₁ to the destination D 130 and the relay R 120, and the destination D 130 and the relay R. 120 receives the first information x ₁ .

In this case, the signal related to the first information (x ₁ ) received at the relay (R) 120 and the destination (D) 130 may be expressed as Equation 1 and Equation 2 below.

[Equation 1]

[Equation 2]

인 노이즈를 나타낸다. In Equations 1 and 2, y _ijN is a signal transmitted from the transmitting side i for the Nth frame time and received at the receiving side j, and α _ijN is a path gain between the transmitting side i and the receiving side j during the Nth frame time. , E _S is the variance as the noise source that is the average transmission power, n _jN of the signal transmitted from the (S) is added to a reception-side j during a time frame N

Indicates noise.

Here, the noise may mean an added white Gaussian Niose (AWGN).

On the other hand, α _ijN (path gain) disclosed in Equation 2 is a part related to the fading, and the path gain may be larger as the fading between the two paths occurs less.

Second, during the second frame time after the first frame time, the source S 110 transmits the second information x ₂ to the destination D 130 and at the same time, the relay R 120 The demodulated first information (x ₁ ') signal regarding the first information (x ₁ ) received in the first frame time, which is the previous frame time, is transmitted to the destination (D) 130.

On the other hand, the relay (R) 120, after determining whether to transmit a demodulated signal for the first information (x ₁ ) to the destination (D; 130) side (selective relay operation) after the predetermined criterion, When a predetermined criterion is satisfied, the received first information x ₁ may be demodulated to transmit a demodulated signal x ₁ ′ to the destination D 130.

)이 기준값(

) 이하인 경우, 상기 제1정보(x₁)를 아래의 수학식 4와 같이 복조하여 복조된 신호(x₁')를 목적지(D;130) 측으로 전송할 수 있다. For example, the predetermined criterion may be a BER (Bit Error Rate). As shown in Equation 3 below, the BER value ( ₁ ) related to the first information (x ₁ ) received by the relay (R) 120 may be determined.

) Is the reference value (

) Or less, the first information x ₁ may be demodulated as shown in Equation 4 below to transmit a demodulated signal x ₁ ′ to the destination D 130.

)을 초과하는 경우에는 상술한 동작을 수행하지 않는다. 여기서, 상기 기준값(

)은 물론 충분히 작은 값을 의미한다.In contrast, the reference value (

), The above operation is not performed. Here, the reference value (

) Means, of course, a small enough value.

[Equation 3]

,

,

[Equation 4]

In Equation (4), sign (·) is a sign function, and if (·) is a positive value greater than 0, it is a function that determines 1, and a negative value less than 0 is -1, and Re (·) Means take only the real part of the values in parentheses.

That is, after taking only the real part about the product between the conjugation value of the path gain α _SR1 between the source S 110 and the relay R 120 and the y _SR1 value disclosed in Equation 1 above, Depending on whether the real part value is negative or positive, the received x ₁ signal is detected as an x ₁ 'signal consisting of 1 or -1 values.

에 따르면, 상기

값(LLR;Log Likelihood Rate)은 수학식 4에 개시된 α_SR1 ^*값과 y_SR1(수학식 1)값 간의 곱'에 의해 연산되는 소스(S;110)와 릴레이(R;120) 간의 경로이득의 제곱(|α_SR1|²)값 뿐만 아니라, α_SR ^*과 노이즈 성분(n_SR) 간의 곱이 모두 고려되게 된다. 참고로 수학식 3의

는 릴레이(R;120) 측의 노이즈 분산값을 의미할 수 있다.Meanwhile, of Equation 3

According to the above

The value LLR (Log Likelihood Rate) is a path gain between the source S 110 and the relay R 120 calculated by the product of the value of α _SR1 ^* and y _SR1 (Equation 1) disclosed in Equation 4. In addition to the square (| α _SR1 | ² ) value of, the product between α _SR ^* and the noise component n _SR is all considered. For reference, Equation 3

May mean a noise variance value of the relay (R) 120 side.

Therefore, according to the selective relay operation as shown in Equation 3 based on the LLR, the noise component as well as the fading element directly related to the path gain on the current system are all considered, thereby increasing the performance, efficiency, and reliability of retransmission. Can be.

Of course, the above-described selective relay operation may be performed by more various principles not introduced in the present invention in addition to the method using the LLR.

Meanwhile, when the signal y _SD2 received at the destination D 130 during the second frame time is mathematically represented, Equation 5 below.

[Equation 5]

과, 상기 소스(S;110)로부터 전송받은 제2정보(x₂)인

를 함께 수신한다.2, 3, and 5, the destination D 130 during the second frame time is the demodulated first information x ₁ ′ received from the relay R 120.

And second information (x ₂ ) received from the source (S; 110).

Receive together.

이며, 만일 릴레이(R;120)에서 상기 수학식 3의 조건이 만족되지 않는 경우에는, 복조된 제1정보(x₁')를 전송하지 않으므로

이 된다.here,

If the condition of Equation 3 is not satisfied in the relay R 120, the demodulated first information x ₁ ′ is not transmitted.

Becomes

인 경우를 제외하고는, 상기 목적지(D;130)는 수신받은 신호를 수학식 6과 같은 행렬로 재배열하여 표현할 수 있다.(수학식 2 및 수학식 5 참고)Above

Except, the destination D 130 may rearrange the received signal into a matrix such as Equation 6 (see Equation 2 and Equation 5).

[Equation 6]

The destination (D) 130 distinguishes the second information (x ₂ ) received from the source (S) and the demodulated first information (x ₁ ′) received from the relay (R) as an original signal. It is desirable to recover. This is for a first information (x ₁₎ is the second information (x ₂₎ acts as interference signal (interference signal) for, and second information (x ₂₎ has a first information (x ₁₎ as shown in Equation 6 This is why it can act as a jammer.

That is, the destination D 130 may interfere with the second information x ₂ to recover the first information x ₁ using the demodulated first information x ₁ ′, that is, the interference signal. It can be judged to be and recover separately from such interference signal.

In this case, the signal to interference plus noise ratio may be used for x ₁ recovery of Equation 7 as follows.

[Equation 7]

,

,

는 목적지(D;130)에 의한, 제1정보(x₁)의 복구된 신호를 의미하고, c1, c2는 수학식 6의 아랫부분에 표현되어 있다. 또한, I_K는 k×k의 단위행렬이고, (ㆍ)는 헤르미트 전치(Hermitian tramspose)를 의미한다.here,

Denotes a recovered signal of the first information (x ₁ ) by the destination (D) 130, and c1 and c2 are represented at the bottom of Equation (6). In addition, I _K is a unit matrix of k × k, and (·) means Hermitian tramspose.

부분은 제거한 후에 제2정보(x₂)를 복구한다. On the other hand, the destination (D; 130) is the second in order to recover information (x _2), when determining the first information (x ₁ ') the demodulated to be the interference signal, the first information (x ₁ ) Is first performed, and then, as shown in Equation 8,

After the part is removed, the second information (x ₂ ) is recovered.

[Equation 8]

는 목적지(D;130)에 의한, 제2정보(x₂)의 복구된 신호를 의미한다.here,

Denotes a recovered signal of the second information (x ₂ ) by the destination (D) 130.

sign (·) is the signum function as described above. If (·) is a positive number greater than 0, it is determined as 1, and if it is a negative number less than 0, Re (·) is the real part of the values in parentheses. It means taking the bay.

신호로 복구한다.That is, a product of a conjugation value of a path gain α _SD2 between a source S 110 and a destination D 130 regarding a second frame time and a y _SR2 value disclosed in Equation 9 below. After taking only the real part, the received x ₂ signal has a value of 1 or -1 depending on whether the value of the real part is negative or positive.

Restore to the signal.

[Equation 9]

부분을 제거한 값이다.That is, Equation 9 is expressed by Equation 5

The value is removed.

On the other hand, as shown in Fig. 2 or 3, during the third frame time after the second frame time, the source (S; 110), of course, the next third information (x ₃ ) to the destination (D; 130) To the relay (R) 120. In addition, during the fourth frame time, the source S 110 transmits the fourth information x ₄ to the destination D 130, and the relay R 120 transmits at the third frame time, which is the previous frame time. The demodulated third information (x ₃ ') of the received third information (x ₃ ) is transmitted to the destination (D) 130.

The algorithm of the present invention as described above is applicable to the case where the spatial diversity is improved by installing multiple (M) antennas at the destination (D) 130, where each antenna is an independent path. In this case, Equation 6 may be modified to the form of Equation 10 below.

[Equation 10]

That is, in Y _SDN , m, N denotes the N-th frame time unit as described above, and m denotes the M-th antenna among 1,2,3, ..., M.

In this case, x ₁ and x ₂ signals received at the destination D 130 may be defined by Equation 11 as follows.

[Equation 11]

이다.here,

to be.

Hereinafter, the performance of the cooperative relay system 100 in which the spectral efficiency of the present invention is not reduced as described above will be described with reference to FIGS. 4 to 5.

To this end, in the present experiment, the source (S; 110), the relay (R; 120) and the destination (D; 130) are located in line with each other and between the source (S; 110) and the destination (D; 130) Assume that the distance d _SD is '1' and the path loss index η is 4.

In some cases, the destination D 130 may have M multiple antennas.

In addition, in the cooperative relay system 100 according to the present invention, a performance comparison was performed with a direct transmission (DT) which performs only direct communication between a source and a destination without a relay.

For a more fair comparison, it is preferable that the total energy consumption of the cooperative relay system 100 of the present invention does not exceed the energy consumption of the DT method.

Therefore, the equation for the equivalent energy between the cooperative relay system 100 and the DT method of the present invention is expressed by Equation 12 below.

[Equation 12]

For example, in the case of the present invention, the first frame section and the second frame section of FIG. 2 are used as a total of two sources S for transmitting the first information (x ₁ ) and the second information (x ₂ ) as shown in FIG. 2. 110) and one relay (R; 120) operation for transmitting the demodulated first information (x ₁ ′) is performed to consume 2 E _S + E _R of the total energy, in the case of DT, only 2; Only one source operation is performed to consume a total of 2E _DT by consuming energy of E _DT per frame period.

Here, it is preferable that E _S + E _R be allocated to each energy appropriately from the energy of 2E _DT which is the total energy.

If, in the second frame section, the power of the signal transmitted from the source S 110 and the relay R 120 and received at the destination D 130 is the same, Equation 13 or Equation 14 Can be defined as:

[Equation 13]

[Equation 14]

Since λ _ij has been previously defined as [λ _ij = (d _SD / d _ij ) ^η ], a detailed description thereof will be omitted.

Here, using Equation 12 and Equation 14, energy allocation as shown in Equation 15 below may be performed.

[Equation 15]

This energy allocation scheme is only a preferred embodiment and can be changed in various forms.

인 조건에서, 상기 기준값(

)=10^-4, 소스(S;110)와 릴레이(R;120) 간의 거리(=d_SR)인 d∈{0.3,0.6,0.9}, 안테나의 갯수 M∈{1.2.3}인 경우, E_DT/N₀ 대 BER 특성을 나타낸다.Meanwhile, FIG. 2 shows that noise variance values at the relay R and the destination D are 130.

Under conditions of the reference value (

) = 10 ^-4 , d∈ {0.3,0.6,0.9}, which is the distance (= d _SR ) between the source S; 110 and the relay R; 120, and the number of antennas M∈ {1.2.3}, E _DT / N ₀ versus BER characteristic.

Referring to the result of FIG. 2, the relay system 100 of the present invention is always found to have a gain of about 1 dB more than the case of the direct transmission ( _DT ) for the entire E _DT / N ₀ range. As shown, the result is independent of the number of antennas.

In the case of the conventional relay system, in the low E _DT / N ₀ range, the BER characteristic is often lower than that of the DT. However, according to the present invention, as described above, it is always superior to DT during the entire E _DT / N ₀ period. It can be seen that the characteristics are exhibited, which clearly demonstrates the remarkable effect of the present invention without lowering the spectral efficiency.

In addition, referring to Figure 2, the BER performance is slightly changed by the value of d, which means that the flexible control of the cooperative communication using the relay (R) (120) is possible.

)을 10^-3,10^-4,10^-5로 변경한 경우의 E_DT/N₀ 대 BER의 특성을 나타낸다.On the other hand, Figure 3 is a reference value in a fixed state of d = 0.6 (

E _DT / N ₀ when) is changed to 10 ^-3 , 10 ^-4 , 10 ^-5 Versus BER.

)의 변경은 본 발명의 BER 특성에 약간의 차이를 발생시키나, 이러한 도 3의 경우 또한 안테나의 갯수와는 무관하게 항상 DT 통신방식에 비해 우수한 특성을 보이는 것으로 나타났다.The reference value mentioned above

) Changes slightly the BER characteristics of the present invention, but in the case of FIG. 3, it is also shown that the characteristics are always superior to the DT communication scheme regardless of the number of antennas.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

1 is a configuration diagram of a general dual-hop network cooperative communication in which a source transmits information to a destination side by cooperation of a relay;

2 is a block diagram of a cooperative relay system in which spectral efficiency is not degraded according to an embodiment of the present invention;

3 is a conceptual diagram of FIG. 2;

4 to 5 are graphs showing the performance of the cooperative relay system according to the configuration of FIG.

<Explanation of symbols for the main parts of the drawings>

100 ... cooperative relay system with no deterioration of spectrum efficiency

110.Source 120.Relay

130 ... Destination

Claims (3)

In the cooperative relay system consisting of a source (S), a destination (D) and a relay (R) for relaying between the source (S) and the destination (D), The source S transmits the N-th information to the relay R and the destination D for an N-th frame time (N is an even number including 2) and the N-th frame. Transmits N-th information to the destination (D) for an N-th frame time after time; The relay R may be configured to read the demodulated N-1 information about the N-1 information received from the source S at the N-1th frame time, which is a previous frame time, during the Nth frame time. As you send to the destination (D), The operation of transmitting the N-th information from the source S to the destination D and the operation of transmitting the demodulated N-I information from the relay R to the destination D are performed in the Nth operation. A cooperative relay system in which spectral efficiency is not degraded, which is simultaneously performed during frame time. The method of claim 1, wherein the destination (D) during the N-th frame time, The cooperative relay does not deteriorate the spectral efficiency, characterized in that to recover the original signal by distinguishing the N-th information received from the source S and the demodulated N-1 information received from the relay (R). system. The method of claim 2, wherein the destination (D) during the N-th frame time, When recovering the N-th information received from the source S, the demodulated N-th information received from the relay R is determined to be an interference signal, and is individually recovered in a state excluding the interference signal. When recovering the demodulated N-th signal transmitted from the relay R, the N-th information received from the source S is determined to be an interference signal, and is individually recovered in a state in which the interference signal is excluded. Cooperative relay system that does not lower spectral efficiency.

Images