KR20070034408A - Hybrid Forwarding Apparatus and Method for Cooperative Relaying in Orthogonal Frequency Multiplexing Network - Google Patents

Abstract

The present invention relates to a hybrid forwarding device and method for cooperative relaying in an orthogonal frequency multi-division network, and to a hybrid forwarding device of a repeater for transmitting data using a repeater in an orthogonal frequency multi-division network. A forwarding structure selector for determining a transmission forwarding scheme, an AF unit for amplifying data received from the forwarding structure selector when using an AF and a forwarding structure selector, and a forwarding structure when using a decode and forward (DF) scheme A DF unit for decoding and encoding data received from a selector, and a multiplexer for providing the AF and DF output data to an orthogonal frequency division multiplexing (OFDM) modulator. Based on the bit error probability, the transmission method is determined. Therefore, since a more suitable forwarding scheme can be selected and used based on the bit error probability, there is an advantage of obtaining a communication link having a lower bit error probability and a higher transmission rate.

Relay, Hybrid Forwarding, Orthogonal Frequency Division Multiplexing (OFDM).

Description

Hybrid Forwarding Apparatus and Method for Cooperative Relaying in Orthogonal Frequency Multiplexing Networks {APPARATUS AND METHOD FOR HYBRID FORWARDING FOR COOPERATIVE RELAYING IN OFDM NETWORK}

1 is a diagram showing an OFDM-based repeater using a conventional AF method,

2 is a diagram illustrating an OFDM-based repeater using a conventional DF scheme;

3 is a diagram illustrating a network structure according to an embodiment of the present invention;

4 is a diagram illustrating a channel according to time division transmission according to an embodiment of the present invention;

5 is a diagram illustrating a case where a hybrid forwarding scheme is used for each subcarrier in a repeater according to an exemplary embodiment of the present invention.

6 is a view showing the configuration of a repeater according to an embodiment of the present invention;

7 is a diagram illustrating a configuration of a receiving node according to an embodiment of the present invention;

8 is a diagram illustrating a configuration of a transmitting node according to an embodiment of the present invention.

9 is a flowchart illustrating an operation flow of a repeater according to an embodiment of the present invention;

10 is a flowchart illustrating an operation of a receiving node according to an embodiment of the present invention, and

11 illustrates an example of forward link reverse link transmission in an OFDM system according to an embodiment of the present invention.

12 is a graph comparing the performance of the hybrid forwarding method and the direct transmission method.

The present invention relates to an orthogonal frequency multi-division network, and more particularly, to a hybrid forwarding apparatus and method in a cooperative relay method using a relay.

In order to switch from the 2nd and 3rd generation systems to the 4th generation systems in mobile communication systems, it is necessary to improve the frequency utilization and the performance of QoS (Quality of Service) in the wireless section.

In order to satisfy the requirements related to the data rate and stability, a single input single output (SISO) having one input and output has a problem that is not practical due to limited frequency usage characteristics.

In order to satisfy the requirements of the QoS, it is necessary to develop a new transmission method. A multiple antenna technology such as a multiple input multiple output (MIMO) technology increases the system capacity.

The MIMO communication technology has a very high frequency efficiency compared to the SISO communication in a high scattering environment. The capacity increases linearly as the number of antennas on the receiving side is equal to or larger than the number of antennas on the transmitting side.

The MIMO technology simultaneously transmits the same signal to multiple receivers using multiple antennas. In the present invention, each signal is called a diversity branch.

If the diversity branch of the signal transmitted from the receiving side is increased, the probability of experiencing fading is reduced and the reliability is increased. However, the technique requires multiple antennas at the transmitter. There is a problem of increasing hardware complexity and cost.

In addition, system performance depends on the number of antennas, distributed environment, spatial fading relationship between transmit and receive antennas, and the distance of each network element, so it is not always possible to obtain performance improvement through conventional MIMO technology. .

The advantages of conventional multi-antenna techniques can also be achieved by collaborative communication using a virtual antenna array (VAA). The virtual antenna array is generated by a repeater for assisting communication between the transmitting side and the receiving side, and cooperative communication indicates that the repeater relays a communication signal to communication between the transmitting side and the receiving side. That is, in the SISO environment, the VAA can be used to obtain the advantages of the multiple antenna technology.

In addition, since the virtual antenna array serves as a virtual antenna of the transmitting side or the receiving side, it is possible to increase the reliability and expand the communication range, thereby reducing the probability of communication loss and the bit error probability between the transmitting side and the receiving side. This can be reduced.

In addition, due to the virtual antenna array, because it is less sensitive to the surrounding environment it is possible to obtain a high transmission rate, if the same transmission rate, it is possible to reduce the power consumption.

The purpose of the cooperative communication system is to improve stability in communication between the transmitting side and the receiving side. In order to achieve the above object, it is particularly desirable to improve a forwarding scheme using diversity using the virtual antenna array. need.

In the forwarding method, an Amplify and Forward (AF) method and a Decode and Forward (DF) method are commonly used in the repeater network.

The AF method is a method of amplifying and forwarding a signal after receiving the signal, and the DF is a method of decoding and forwarding the received signal again after decoding.

1 illustrates an OFDM-based repeater using a conventional AF method. In the following description, orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) scheme is described as an example, and code division multiple access or time division multiple access using TDD (Time Division Duplex) is used. Also applicable to (Time Division Multiple Access).

Referring to FIG. 1, the receiving apparatus includes a radio frequency (RF) processor 122, an OFDM demodulator 120, and a buffer 114. The OFDM demodulator 120 includes an analog / digital conversion module. (Analog / Digital Converter), OFDM demodulation module, and decoding module.

The RF processor 122 converts a radio frequency (RF) signal received through an antenna into a baseband analog signal.

The analog / digital conversion module of the OFDM demodulator 120 converts the analog signal provided from the RF processor 122 into a digital signal to provide the OFDM demodulation module, and the OFDM demodulation module is the analog / digital conversion module. Fast domain Fourier transform (FAST Fourier transform) provided from the time domain to output the data of the frequency domain to provide to the decoding module.

The decoding module decodes the data provided from the OFDM demodulation module with a corresponding demodulation scheme and a predetermined code rate and stores the data in the buffer 124.

The transmitter includes a radio frequency (RF) processor 112, an OFDM modulator 110, and an AF module 114. The OFDM modulator 110 includes a digital / analog conversion module, an OFDM modulator module, and an encoding. It consists of modules.

First, the AF module 114 performs gain amplification for each subcarrier loaded from the buffer 124, and then provides the gain amplification to the OFDM modulator 110.

The gain amplification range is determined according to channel state information (hereinafter referred to as CSI) of data received by the repeater.

The coding module of the OFDM modulator 110 encodes the data provided from the AF module 114 to the OFDM module by encoding the code rate and the corresponding modulation scheme according to MCS (Modulation & Coding Scheme) level information. Here, the modulation scheme may be Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), or 64QAM.

The OFDM modulation module performs an inverse fast Fourier transform on the data provided from the coding module and outputs sample data (OFDM symbols) in the time domain to the digital / analog conversion module.

The digital / analog conversion module converts sample data from the OFDM modulation module into an analog signal and provides it to the RF processor 112.

The RF processor 112 converts an analog signal from the OFDM modulator 110 into a radio frequency (RF) signal and transmits the same through an antenna.

The RF switch 130 connects a reception signal received through the antenna to the receiver, and when transmitting data, connects a transmitter and an antenna to transmit the data.

2 illustrates an OFDM-based repeater using a conventional DF scheme. In the following description, an Orthogonal Frequency Division Multiplexing (hereinafter, referred to as OFDM) scheme is described as an example, and code division multiple access or time division multiplexing using time division duplex is illustrated. It is also applicable to a connection (Time Division Multiple Access).

Referring to FIG. 2, the reception apparatus includes a radio frequency (RF) processor 122, an OFDM demodulator 120, a detector 240, a decoder 270, and a buffer 280. The OFDM demodulator 120 includes an analog / digital converter, an OFDM demodulation module, and a decoding module.

The RF processor 122 converts a radio frequency (RF) signal received through an antenna into a baseband analog signal.

The analog / digital conversion module of the OFDM demodulator 120 converts an analog signal provided from the RF processor 122 into a digital signal to provide the OFDM demodulation module, and the OFDM demodulation module is provided from the analog / digital conversion module. Fast Fourier Transform (FAST Fourier Transform) is provided to output the frequency domain data to the decoding module.

The decoding module decodes the data provided from the OFDM demodulation module at a corresponding demodulation scheme and a predetermined code rate, and decodes the data from the corresponding bit string to provide the detector 240.

The detector 240 checks whether the received data is data based on CSI.

The decoder 270 detects the reception of the data based on the CSI by the detector 240, and if the data received from the detector 240 is the data that the channel side accepts channel coding for, the data is received. Is decoded using the channel coding and stored in the buffer 280.

The transmission apparatus includes a radio frequency (RF) processor 112, an OFDM modulator 110, a subcarrier symbol mapper 230, and an encoder 260, and the OFDM modulator 110 includes a digital / analog conversion. Module, OFDM modulation module, and coding module.

First, when the data loaded from the buffer 280 is the data decoded by the decoder 270, the encoder 260 re-encodes the data to the subcarrier symbol mapper 230. to provide.

The subcarrier symbol mapper 230 maps the data provided from the encoder 124 to the subcarrier, arranges the mapped data in parallel, and provides the mapped data to the OFDM modulator 110. .

The encoding module of the OFDM modulator 110 encodes the data provided from the encoder 124 by the code rate and the corresponding modulation scheme in accordance with the MCS level information to provide the OFDM module. Here, the modulation scheme may be Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16QAM), or 64QAM.

The OFDM modulation module performs inverse fast Fourier transform on the data provided from the coding module and outputs sample data (OFDM symbols) in the time domain to the digital / analog conversion module.

The digital / analog conversion module converts sample data from the OFDM modulation module into an analog signal and provides it to the RF processor 112.

The RF processor 112 converts an analog signal from the OFDM modulator 110 into a radio frequency (RF) signal and transmits the same through an antenna.

The RF switch 130 connects a reception signal received through the antenna to the receiver, and when transmitting data, connects a transmitter and an antenna to transmit the data.

The modulation function of the modulator 260 and the demodulation function of the demodulator 270 are not necessarily functions but optional functions. In the present invention, the optional modulator 260 and the demodulator 270 are indicated by dotted lines.

The AF technique is greatly influenced by the signal noise from the transmitting side to the repeater, and the DF technique is greatly influenced by the accuracy of signal transmission from the transmitting side to the repeater. In addition, the method using the repeater may not have a performance improvement compared to the method using the direct transmission.

Therefore, there is a need for a description of what forwarding scheme to use in hybrid forwarding using the AF technique and the DF technique in the frequency selective environment.

Accordingly, an object of the present invention is to provide a hybrid forwarding apparatus and method using a cooperative relay method in an orthogonal frequency multi-division network.

An apparatus of the present invention for solving the above problems is a hybrid forwarding apparatus of a repeater for transmitting data using a repeater in an orthogonal frequency multiplexing network, the forwarding structure selector for determining a transmission forwarding scheme and An AF unit for amplifying data received from the forwarding structure selector when using an AF and a DF unit for decoding and encoding data provided from the forwarding structure selector when using a decode and forward method. And a multiplexer for providing output data of the AF unit and the DF unit to an orthogonal frequency division multiplexing (OFDM) modulator.

The method of the present invention for solving the above problems is a hybrid forwarding method of a repeater for transmitting data using a repeater in an orthogonal frequency multiplexing network, the AF method based on the CSI of the received data, Calculating the bit error probability of the direct transmission method without using the DF method and the repeater, and after calculating the respective bit error probability, the AF method is used if the bit error probability of the AF method is the lowest It characterized in that it comprises a process.

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

The present invention will now be described with respect to hybrid forwarding apparatus and method for cooperative relaying in an orthogonal frequency multi-division network.

3 illustrates a network structure according to an embodiment of the present invention.

Referring to FIG. 3, the present invention assumes a terminal having one antenna and focuses on the forward link. A transmitting node (Source) 310 represents a base station, and a receiving node (Destination) 330 represents a terminal. The repeater 320 transmits the signal transmitted by the transmitting node to the receiving node 330.

4 illustrates a channel according to time division transmission according to an embodiment of the present invention.

)은 송신노드(310)에 의해 전송된 OFDM 심볼(symbol)을 나타낸다.Referring to FIG. 4, index n (

) Denotes an OFDM symbol transmitted by the transmitting node 310.

During odd timeslots, transmitting node 310 transmits symbols for all subcarriers, and repeater 320 and transmitting node 330 receive the symbols. During an even timeslot, the transmitting node 310 stops transmitting and the repeater 320 forwards the received symbols during the last timeslot.

In the present invention, it is assumed that the repeater 320 forwards the symbols for all subcarriers. During the even timeslot, only the receiving node 330 receives the symbol forwarded by the repeater 320. The channel configuration as described above may configure a virtual reception diversity channel.

In the present invention, it is assumed that the data transmission rate and the total transmission power are the same in the case of the direct transmission and the case of using the repeater to compare the AF, DF, and direct transmission structures.

In addition, in the direct transmission scheme, Binary Phase Shift Keying (BPSK) modulation is used, and the transmitting node 310 transmits a symbol in both an even time slot and an odd time slot. In the method using the repeater 320, quadrature phase shift keying (QPSK) modulation is used.

The hybrid forwarding algorithm in the system of the structures of FIGS. 3 and 4 is as follows.

It is assumed that the repeater 320 knows the SNR (ignal to noise ratio) of symbols for all subcarriers between S-> D, R-> D, and S-> R. The SNR information is transmitted to the repeater 320 through a virtual diversity channel.

S denotes a transmitting node 310, R denotes a repeater 320, and D denotes a receiving node 330. Accordingly, S-> D is a link between the transmitting node 310 and the receiving node 330, R-> D is a link between the repeater 320 and the receiving node 330, and S-> R is The link between the transmitting node 310 and the repeater 320 is shown.

Based on the SNR information, the repeater 320 calculates a bit error probability of a symbol for a subcarrier related to the AF, DF, and direct transmission schemes.

Equation 1 shows the bit error probability when the repeater 320 uses the AF method.

In Equation 1, the function Q () represents QPSK modulation.

Equation 2 shows the bit error probability when the repeater 320 uses the DF method.

In Equation 2, the function Q () represents QPSK modulation.

Equation 3 below shows the bit error probability when using the direct transmission method without the intervention of the repeater 320.

In Equation 3, the function Q () represents QPSK modulation.

Equation 4 below shows the smallest bit error probability when the hybrid forwarding method and the direct transmission method are used together.

,

,그리고

는 각각 S->R, S->D, 그리고 R->D 사이의 부 반송파에 대한 심볼의 SNR을 나타낸다. In Equations 1, 2, and 3

,

,And

Denotes the SNR of the symbol for the subcarrier between S-> R, S-> D, and R-> D, respectively.

와

를 상기 송신노드(310)와 중계기(320)에서의 평균전송전력이라고 할 경우, QPSK 심볼당 평균 총 전송전력은 하기 수학식 5와 같다.

Wow

When the average transmission power in the transmitting node 310 and the repeater 320, the average total transmission power per QPSK symbol is expressed by the following equation (5).

는 심볼주기를 나타내고 1/2이 곱해진 것은 상기 송신노드(310) 과 중계기(320)는 각각 전체 전송시간의 반만 전송하기 때문이다.In Equation 5

Represents a symbol period and 1/2 is multiplied because the transmitting node 310 and the repeater 320 each transmit only half of the total transmission time.

와

는 상기 중계기(320)에서의 어떠한 송신전력의 증가에서도 선형적으로 같이 증가한다. 직접전송방식과 비교하기 위해 상기 중계기(320)에서의 전력증가로 인한 상기

의 증가의 효과는 상기 수학식 3과 같이 직접전송모드에서 동작하는 수신노드(330)의 송신전력에 반영되어야 한다.remind

Wow

Increases linearly with any increase in transmit power at the repeater 320. The increase due to the power increase in the repeater 320 to compare with the direct transmission method

The effect of increasing should be reflected in the transmission power of the receiving node 330 operating in the direct transmission mode as shown in Equation 3 above.

A method of selecting the forwarding structure having the smallest bit error probability for the repeater 320 to apply to a symbol for a specific subcarrier is as follows.

이면, 상기 중계기(320)는 특정 부반송파에 대한 심볼에 AF방식을 사용한다.if,

In this case, the repeater 320 uses an AF method for a symbol for a specific subcarrier.

이면, 상기 중계기(320)는 특정 부반송파에 대한 심볼에 DF방식을 사용한다.if,

In this case, the repeater 320 uses a DF method for a symbol for a specific subcarrier.

이면, 상기 중계기(320)는 중계기능을 중지한다.if,

If so, the repeater 320 stops the relay function.

The repeater 320 notifies the receiving node 330 of the type of forwarding scheme for each subcarrier. However, the notification of the change of the forwarding method is necessary only when the forwarding method is changed. The receiving node 330, which has received the change of the forwarding method, uses the forwarding method.

FIG. 5 illustrates a case where a hybrid forwarding scheme is used for each subcarrier in a repeater according to an exemplary embodiment of the present invention.

Referring to FIG. 5, since the symbols for each subcarriers in the m slots have independent SNRs for the SR, S-> D, and R-> D links, the repeater 320 may use the most suitable scheme. Choose. After a predetermined time, the repeater repeats the process in slot l.

6 illustrates a configuration of a repeater according to an embodiment of the present invention.

Referring to FIG. 6, the forwarding structure selector 650 calculates a bit error probability based on the CSI of the symbol for each subcarrier provided by the OFDM demodulator 120, and then determines a suitable forwarding method to determine a corresponding forwarding block. To send.

The DF unit 668 includes a subcarrier symbol mapper 662, a modulator / demodulator 664, and a detector 660 when using the DF method and performs a modulation / demodulation function for DF forwarding.

The subcarrier symbol mapper 662, the modulator / demodulator 664, and the detector 660 have the same function as the corresponding apparatus in FIG.

The AF unit 680 amplifies the subcarrier provided by the OFDM demodulator 120 when using the AF method.

The multiplexer 690 multiplexes the symbols for the subcarriers stored in the buffer 670 and transmits the symbols to the OFDM modulator 110.

The functions of the OFDM modulator 110, the OFDM demodulator 120, the RF processors 112 and 122, and the RF switch 130 have the same functions as the corresponding apparatus of FIG.

7 illustrates a configuration of a receiving node according to an embodiment of the present invention.

Referring to FIG. 7, the maximum efficiency merger 740 determines a method of merging symbols for subcarriers based on a forwarding method delivered by a repeater. In this case, the CSI may be referred to.

The detector and decoder 750 decode the received data if the received data is a symbol for a subcarrier that accommodates channel coding.

The subcarrier symbol mapper 730 maps the received data to subcarriers, arranges them in parallel, and provides them to the OFDM modulator 110.

The functions of the OFDM modulator 110, the OFDM demodulator 120, the RF processors 112 and 122, and the RF switch 130 have the same functions as the corresponding apparatus of FIG.

8 illustrates a configuration of a transmitting node according to an embodiment of the present invention.

The encoder 870 encodes the received data using channel coding and then provides the encoded data to the symbol mapper 850.

The symbol mapper 850 maps the data provided from the encoder 870 to subcarriers and provides the data to the serial / parallel converter 830.

The serial / parallel converter converts the data provided by the symbol mapper 850 into parallel data and provides the same to the OFDM modulator 110.

The receiver 840 receives the data provided from the OFDM demodulator 120 and transmits the data to the demodulator 860.

The decoder 860 decodes the data using the channel coding if the received data is data that accommodates channel coding.

The functions of the OFDM modulator 110, the OFDM demodulator 120, the RF processors 112 and 122, and the RF switch 130 have the same functions as the corresponding apparatus of FIG.

9 illustrates an operation flow of a repeater according to an embodiment of the present invention.

,

,그리고

를 구한다. Referring to FIG. 9, the repeater 320 receives a symbol for a subcarrier from a transmitting node 310 in step 905, and in step 910 for the subcarrier.

,

,And

Obtain

를 구한다. Thereafter, the process proceeds to step 915 using the equations (1), (2) and (3).

Obtain

를 구한다.Thereafter, the process proceeds to step 920 using the equation (4) based on the value obtained in step 915.

Obtain

이면, 상기 중계기(320)는 930단계로 진행하여 특정 부반송파의 심볼에 대해 AF방식을 사용한다.After that, proceed to step 925

In step 930, the repeater 320 proceeds to step 930 and uses an AF method for a symbol of a specific subcarrier.

이면, 상기 중계기(320)는 940단계로 진행하여 특정 부반송파의 심볼에 대해 DF방식을 사용한다.If at 935

In step 940, the repeater 320 proceeds to step 940 and uses the DF method for the symbol of the specific subcarrier.

일 경우는 ,

와 같으므로 상기 중계기(320)는 945단계로 진행하여 중계기능을 사용하지 않고 본 발명에 따른 알고리듬을 종료한다.If, in step 935

If is,

Since the repeater 320 proceeds to step 945 to end the algorithm according to the present invention without using the relay function.

10 illustrates an operation flow of a receiving node according to an embodiment of the present invention.

Referring to FIG. 10, when the receiving node 330 receives the forwarding method from the repeater 320 in step 1005, the receiving node 330 checks whether the method is an AF method in step 1010.

In the case of the AF method in step 1010, the receiving node 330 proceeds to step 1015 to apply the AF method.

If it is not the AF method in step 1010, the process proceeds to step 1020 and determines whether the method is a DF method.

In the case of the DF method in step 1010, the receiving node 330 proceeds to step 1025 to apply the DF method.

If the DF method is not performed in step 1030, the receiving node 330 proceeds to step 1030 to directly receive data from the transmitting node 310 and terminates the algorithm according to the present invention.

, DF 방식을 적요함에 따라 발생하는 지연시간을

라고 정의한다.As the repeater 320 applies the hybrid forwarding method and the AF or the DF method, a delay time is generated.

The delay time caused by the DF method

It is defined as.

와

보다 커야 한다.Guard time is required to synchronize the repeater 320. The guard time represents the time from the moment when the transmitting node 310 completes the transmission to the moment when the repeater 320 starts forwarding. Thus, the guard time is

Wow

Must be greater than

11 illustrates an example of forward link reverse link transmission in an OFDM system according to an embodiment of the present invention.

Referring to FIG. 11, there are several OFDM symbols in each forward link frame and reverse link frame. In this case, the repeater 320 starts the forward link frame transmission after the reverse link frame is transmitted.

In such a case, the repeater 320 may be used for a synchronization operation for transmission of a subcarrier using a reverse link frame transmission time in another forwarding scheme.

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

As described above, in the present invention, the repeater determines a transmission method by obtaining a bit error probability based on the SNR on the communication link. Therefore, since a more suitable forwarding scheme can be selected and used based on the bit error probability, there is an advantage of obtaining a communication link having a lower bit error probability and a higher transmission rate.

Theoretical and simulation results for the above scheme are as follows. The environment for the following simulation is shown in Table 1 below.

System Bandwidth, B & Carrier Frequency 20MHZ & 5 GHZ Number of subcarriers, N 400

S-> R Link:

1.26 msec, 3 subcarriers S-> D link:

0.23 msec, 17 subcarriers R-> D link:

1.26 msec, 17 subcarriers

,

,

는 각각의 링크에 대한 RMS(Root Mean Square) 지연확산(Delay Spread)을 나타낸다. 주파수 선택적(Frequency Selective)이고, 상호 독립적인 (Mutually Independant) 채널이 각각의 링크에서 고려되었다.

는 반송주파수의 수에 대한 코헤런스 대역폭(Coherence Bandwidht)를 나타낸다.In Table 1 above

,

,

Denotes the root mean square (RMS) delay spread for each link. Frequency Selective and Mutually Independant channels were considered on each link.

Denotes a coherence bandwidth for the number of carrier frequencies.

는 기대값을 나타낸다. 즉

는 S->D 링크상의 부 반송파의 심볼에 대한 비트에러확율의 기대값을 나타낸다. 그리고, 상기

,

,

는 S->R 링크, S->D 링크, R->D 링크상의 SNR값을 나타낸다. 세로축은 비트에러확율을 나타낸다.12 is a graph comparing the performance of the hybrid forwarding method and the direct transmission method.

Indicates the expected value. In other words

Denotes the expected value of the bit error probability for the symbol of the subcarrier on the S-> D link. And the above

,

,

Denotes the SNR values on the S-> R link, S-> D link, and R-> D link. The vertical axis represents the bit error probability.

과

이 5dB 이고

가 15dB 일 경우의 기대값을 나타낸 것이다. 12a),

and

Is 5dB

Expected value when is 15dB.

Referring to FIG. 12A), the hybrid forwarding scheme of the present invention has a gain of about 12dB over a 1 / 100-bit bit error probability compared to the case of using only the conventional AF or DF scheme.

,

,

모두 20dB 일경우의 기대값을 나타낸 것이다. 12b),

,

,

In all cases, the expected value is 20 dB.

12a), the hybrid forwarding scheme of the present invention has a bit error probability of 13 dB compared to the result of using only the conventional AF method for the 3/1000 section and much more than 13 dB compared to the result using only the DF method. Can be obtained.

Claims (19)

In a hybrid forwarding device of a repeater for transmitting data using a repeater in an orthogonal frequency multiplexing network, A forwarding structure selector for determining a transmission forwarding scheme; An AF unit for amplifying data provided from the forwarding structure selector when using an AF (Amplify and Forward) method; A DF unit for decoding and encoding data provided from the forwarding structure selector when using a DF (Decode and Forward) method; And a multiplexer for providing output data of the AF unit and the DF unit to an orthogonal frequency division multiplexing (OFDM) modulator. The method of claim 1, The forwarding structure selector calculates the bit error probability of the AF method, the DF method, and the direct transmission method without using the repeater based on the channel state information (CSI) of the received data, and then the bit error probability of the AF method is increased. When the lowest, the device characterized in that using the AF method. The method of claim 2, Bit error probability of the AF method is characterized in that as shown in Equation 6.

here,

,

,And

Denote the SNR of the symbol for the subcarrier of the link between the transmitting node and the repeater, the link between the transmitting node and the receiving node, and the link between the transmitting node and the receiving node, respectively. The method of claim 1, The forwarding structure selector calculates the bit error probability of the AF method, the DF method, and the direct transmission method that does not use the repeater, based on the CSI of the received data, and then the bit error probability of the DF method is the lowest. A device using the DF method. The method of claim 4, wherein The bit error probability of the DF method is represented by the following equation (7).

here,

,

,And

Denote the SNR of the symbol for the subcarrier of the link between the transmitting node and the repeater, the link between the transmitting node and the receiving node, and the link between the transmitting node and the receiving node, respectively. The method of claim 1, The forwarding structure selector calculates the bit error probability of the AF method, the DF method, and the direct transmission method without using the repeater, respectively, based on the channel state information (CSI) of the received data, and then the bit of the direct transmission method. The device characterized in that the direct transmission method is used when the error probability is the lowest. The method of claim 6, Bit error probability of the direct transmission method is characterized in that as shown in Equation 8

here,

,And

Denotes the SNR of a symbol for a subcarrier of a link between a transmitting node and a receiving node, and a link between a receiving node and a repeater, respectively. The method of claim 1, The AF unit amplifies the received data based on the CSI. The method of claim 1, The DF unit detects whether the received data is data based on CSI; A modulator / demodulator for decoding and re-coding data provided by the detector; And a subcarrier symbol mapper for mapping data provided by the modulator / demodulator to subcarriers. In a hybrid forwarding receiver of a receiving node for receiving data using a repeater in an orthogonal frequency multiplexing network, Apparatus comprising a maximum efficiency combining unit for determining the reception method based on the forwarding method delivered by the repeater The method of claim 10, And the maximum efficiency merger merges data using the DF method when the forwarding method delivered by the repeater is the DF method, and merges the symbols for the subcarriers using the AF method when the AF method is used. In a hybrid forwarding method of a repeater for transmitting data using a repeater in an orthogonal frequency multiplexing network, Calculating bit error probability of the AF method, the DF method, and the direct transmission method without using the repeater based on the CSI of the received data; Calculating the bit error probability and using the AF method when the bit error probability of the AF method is the lowest. The method of claim 12, The bit error probability of the AF method is represented by the following equation (9).

here,

,

,And

Denote the SNR of the symbol for the subcarrier of the link between the transmitting node and the repeater, the link between the transmitting node and the receiving node, and the link between the transmitting node and the receiving node, respectively. The method of claim 12, And after calculating the respective bit error probability, using the DF method when the bit error probability of the DF method is the lowest. The method of claim 14, The bit error probability of the DF method is represented by the following equation (10).

here,

,

,And

Denote the SNR of the symbol for the subcarrier of the link between the transmitting node and the repeater, the link between the transmitting node and the receiving node, and the link between the transmitting node and the receiving node, respectively. The method of claim 12, Calculating the bit error probability and using the direct transmission method when the bit error probability of the direct transmission method is the lowest. The method of claim 16, The bit error probability of the direct transmission method is represented by Equation 11 below.

here,

,And

Denotes the SNR of a symbol for a subcarrier of a link between a transmitting node and a receiving node, and a link between a receiving node and a repeater, respectively. In a hybrid forwarding reception method of a receiving node for receiving data using a repeater in an orthogonal frequency multiplexing network, And determining the reception method based on the forwarding method delivered by the repeater. The method of claim 18, The reception method includes merging data using the DF method when the forwarding method delivered by the repeater is the DF method, and merging symbols for subcarriers using the AF method when the AF method is used.

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