JP5461485B2 - Wireless communication system, wireless communication method, and destination station - Google Patents

Description

  The present invention relates to a technique for effectively combining (diversity combining technique) signals transmitted from a transmitting station and a relay station when performing coordinated transmission.

  In recent years, cooperative communication transmission that improves communication characteristics by causing cooperative relay transmission to be performed between a source station and a wireless station other than a destination station has attracted attention. For this reason, much research has been conducted on cooperative relay transmission. The system model of the communication system in cooperative relay transmission is mainly determined by the three elements of relay station forward system, cooperative system configuration (topology), and cooperative protocol.

  The relay station forward method indicates what kind of signal processing is performed on a signal received by a relay station from a transmission station and transmitted to a destination station. The most basic relay forward method is the DF (Decode-and-Forward) method and the AF (Amplify-and-Forward) method. The DF method is a technique in which a signal received by a relay station is reproduced and demodulated and decoded, and then the reproduced signal is encoded and modulated and transmitted to a destination station. The AF method is a method of amplifying a signal received by a relay station and transmitting the amplified signal to a destination station.

  Also, the cooperative system configuration (topology) includes the number of communication devices as a source station, a relay station, and a destination station that constitute a wireless communication system using cooperative communication transmission, and cooperative relay hops performed in the wireless communication system. Indicates a number. For example, the simplest configuration of a wireless communication system using cooperative communication transmission includes a source station (Source; S), a relay station (Relay; R) that relays a signal transmitted by the source station, and a destination station (Destination; D) and a 1-Relay2-HOP (1R2H) configuration.

  In the 1R2H configuration, generally, one slot of radio resources (time and frequency) is allocated to transmission / reception from the transmission station to the relay station and transmission / reception from the relay station to the destination station. In many cases, one cycle in transmission / reception is set to two slots.

  The cooperative protocol indicates a combination of transmission / reception relationships between communication devices (source station, relay station, and destination station) in one cycle of the wireless communication system.

  FIG. 6 is a conceptual diagram illustrating an example of a cooperation protocol in the wireless communication system 3 having the 1R2H configuration. As shown in FIG. 6, the wireless communication system 3 includes a transmission station 31, a relay station 32, and a destination station 33. The source station 31, the relay station 32, and the destination station 33 perform radio communication using OFDM modulation, and one cycle of the radio communication system 3 is divided into two slots, slot # 1 and slot # 2. .

  As shown in FIG. 6A, in slot # 1, the transmission station 31 performs broadcast transmission to the relay station 32 and the destination station 33. As shown in FIG. 6B, the source station 31 and the relay station 32 perform simultaneous transmission to the destination station 33 in the slot # 2. At this time, the relay station 32 requires a processing time Dr to transmit the subpacket P1 in the slot # 2, as shown in FIG. 6C, in order to amplify the subpacket P1 received in the slot # 1. Further, in order to match the timing at which the sub-station P2 is transmitted in slot 2 with the timing at which the relay station 32 transmits the sub-packet P1, the transmitting station 31 has a period after the standby time Ds has elapsed as shown in FIG. 6C. Send. The standby time Ds is determined in advance according to the processing time Dr.

  The destination station 33 receives one type of signal (subpacket P1) transmitted from the transmission station 31 in the slot # 1, and the signal transmitted from the transmission station 31 (subpacket P2) and the relay station in the slot # 2. A signal obtained by combining two kinds of signals with the signal (subpacket P1) transmitted by the terminal 32 is received.

  The cooperative protocol shown in FIGS. 6A to 6C is called a protocol I or a MIMO (Multiple-Input Multiple-Output) type (see, for example, Non-Patent Documents 1 and 2). Hereinafter, the transmission / reception relationship of the transmission station 31, the relay station 32, and the destination station 33 when the protocol I is applied as the cooperative protocol in the wireless communication system 3 will be described in the frequency domain.

When the protocol I is applied as the cooperative protocol, the transmission station 31 broadcasts the subpacket P1 to the relay station 32 and the destination station 33 in the slot # 1. At this time, the received signal Y _d1 received by the destination station 33 is expressed as the following expression (1) in the frequency domain.

Here, P _s1 is the transmission power of the transmission station 31 in the slot # 1. H _sd is a channel frequency response (CFR) between the transmission station 31 and the destination station 33. X ₁ is a transmission signal corresponding to the sub-packet P1. W _d1 is a frequency domain representation of additive white Gaussian noise (AWGN) in slot # 1 at the destination station 33.

Also, the reception signal Y _r1 received by the relay station 32 in the slot # 1 is expressed as the following equation (2).

Here, H _sr is a channel frequency response between the transmission station 31 and the relay station 32. W _r1 is a frequency domain representation of the additional white Gaussian noise at slot # 1 in the relay station 32, and its standard deviation is σ ₁ .

The relay station 32 amplifies the received signal Y _r1 received in the slot # 1 by the amplification coefficient α _r and transmits the amplified received signal to the destination station 33 in the slot # 2. The transmission station 31 transmits the transmission signal X ₂ (subpacket P2) to the destination station 33. At this time, considering that transmission signals are simultaneously transmitted from the transmission station 31 and the relay station 32 and the presence of additional noise at the time of reception, the reception signal Y _d2 received by the destination station 33 in the slot # 2 is It is represented by Formula (3). The amplification coefficient α _r is determined according to the characteristic that the relay station 32 amplifies the reception signal Y _r1 .

Here, P _r2 is the transmission power of the relay station 32 in the slot # 2, and P _s2 is the transmission power of the transmission station 31 in the slot # 2. H _rd is a channel frequency response at the relay station 32 and the destination station 33. W ′ _d2 is a frequency domain representation of the additional white Gaussian noise in slot # 2 at the destination station 33, and its standard deviation is σ ₂ .

  When Formula (1) and Formula (3) are put together, it can be expressed as the following Formula (4).

Here, when the AF method is used for the relay station forward method, H ₁₁ , H ₂₁ , and H ₂₂ in Expression (4) are respectively expressed as the following Expressions (5) to (7).

In addition, when the DF method is used for the relay station forward method, H ₁₁ , H ₂₁ , and H22 in Expression (4) are respectively expressed as the following Expressions (8) to (10).

The destination station 33 calculates the estimated values of the channel frequency responses H ₁₁ , H ₂₁ and H ₂₂ . The destination station 33 uses the estimated value of _{H 11, H 21, H 22} the calculated, demodulation of the transmitted signal included in the received signal _{Y d2} received in slot # 2, the decoding performed. In the conventional method, X ₁ = X ₂ and Equation (4) is obtained by the following Equation (11).

Therefore, demodulation and decoding are performed by combining Y _d1 and Y _d2 . In the synthesis here, for example, when maximum ratio synthesis is performed, the formula is the following formula (12).

Here, X ₁ with a hat (^) is a detected value of X ₁ . Moreover, about the right side of Numerical formula (12), it is following Formula (13), (14).

Regarding Equation (14), when decoding is | (H ₂₁ + H ₂₂ ) | ² and H ₂₁ and H ₂₂ are out of phase, the channel power decreases, and therefore the received signal in slot # 2 is attenuated. Occurs.

RU Nabar, H. Bolcskei, and FW Kneubuhler, “Fading relay channels: Performance limits and space-time signal design,” IEEE J. Sel. Areas Commun., Vol. 22, no. 6, pp. 1099-1109, Jun . 2004. Z. Zhao, et al, “Application of Cooperative Diversity in 802.11a Ad-hoc Networks,” ICCCN’07, 1016-1021, Aug. 2007.

  However, in the prior art, since the same data is transmitted from different radio stations (transmitting station 31 and relay station 32) in slot # 2, the destination station 33 weakens when these signals strengthen each other. There are cases. When the destination station 33 performs maximum ratio combining of the signal received in slot # 1 and the signal received in slot # 2, when H21 and H22 are out of phase, the received signal in slot # 2 is attenuated and decoded. There is a problem that the possibility of making an error increases.

  In view of the above circumstances, an object of the present invention is to provide a technique capable of improving the overall decoding characteristics when performing cooperative transmission.

  According to one aspect of the present invention, a modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and space-time encoding the symbol sequence, the first signal and the second signal And a second time slot obtained by radio transmission of the first signal in a first time slot obtained by time-division of one radio channel. And a transmitter that wirelessly transmits the second signal in the first time slot, the first signal transmitted by the transmitter station is received in the first time slot, and the second signal is transmitted in the second time slot. A relay station having a relay transmitter for transmitting a first signal; and receiving the first signal transmitted by the source station in the first time slot; and receiving the first signal in the second time slot. A receiving unit that receives a combined signal of the second signal transmitted from the transmitting station and the first signal transmitted from the relay station; and a combination of the combined signal received in the second time slot. A demodulator that performs a complex conjugate process on the even-numbered symbol sequence and performs a demodulation process based on the result of the complex conjugate process and the first signal received in the first time slot; And a destination station that includes a decoding unit that performs a decoding process based on a result of the process.

  In one aspect of the present invention, the space-time encoding unit generates the first signal and the second signal by performing space-time encoding with a set of even-numbered symbols.

  One aspect of the present invention is a modulation step in which a transmitting station modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and the transmitting station performs space-time coding on the symbol sequence. Performing a space-time coding step to generate a first signal and a second signal, and the transmitting station wirelessly transmits the first signal in a first time slot obtained by time-division of one radio channel. Transmitting and wirelessly transmitting the second signal in a second time slot obtained by the time division, and the relay station transmits the first signal transmitted by the transmitting station in the first time slot. A relay transmission step of receiving a signal and transmitting the first signal in the second time slot; a destination station transmitting the signal in the first time slot; A receiving step of receiving the first signal and receiving a combined signal of the second signal transmitted by the transmitting station and the first signal transmitted by the relay station in the second time slot; The destination station performs a complex conjugate process on the even-numbered symbol sequence of the composite signal received in the second time slot, and the result of the complex conjugate process is received in the first time slot. A demodulation step for performing a demodulation process based on the first signal; and a decoding step for the destination station to perform a decoding process based on a result of the demodulation process.

  According to one aspect of the present invention, a modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and space-time encoding the symbol sequence, the first signal and the second signal And a second time slot obtained by radio transmission of the first signal in a first time slot obtained by time-division of one radio channel. And a transmitter that wirelessly transmits the second signal in the first time slot, the first signal transmitted by the transmitter station is received in the first time slot, and the second signal is transmitted in the second time slot. A relay station including a relay transmission unit that transmits a first signal; and a destination station that receives a radio signal from the relay station, wherein the first signal transmitted by the transmission station in the first time slot A receiving unit that receives the combined signal of the second signal transmitted from the source station and the first signal transmitted from the relay station in the second time slot; Complex conjugate processing is performed on the even-numbered symbol sequence of the composite signal received in the slot, and demodulation is performed based on the result of the complex conjugate processing and the first signal received in the first time slot. A demodulation unit that performs processing; and a decoding unit that performs decoding processing based on a result of the demodulation processing.

  According to one aspect of the present invention, a modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and space-time encoding the symbol sequence, the first signal and the second signal And a second time slot obtained by radio transmission of the first signal in a first time slot obtained by time-division of one radio channel. And a transmitter that wirelessly transmits the second signal in the first time slot, the first signal transmitted by the transmitter station is received in the first time slot, and the second signal is transmitted in the second time slot. A wireless communication method performed by a relay station including a relay transmission unit that transmits a first signal and a destination station that receives a radio signal from the relay station, wherein the transmission station transmits the signal in the first time slot. A receiving step of receiving the first signal and receiving a combined signal of the second signal transmitted from the transmitting station and the first signal transmitted from the relay station in the second time slot; And complex conjugate processing is performed on the even-numbered symbol sequence of the composite signal received in the second time slot, and the result of the complex conjugate processing and the first received in the first time slot A demodulation step for performing demodulation processing based on the signal, and a decoding step for performing decoding processing based on the result of the demodulation processing.

  According to the present invention, space-time coding is performed on the transmitting side, complex conjugate processing is performed on the even-numbered symbols on the receiving side, and the obtained results of the received signals in the first and second slots are combined in a maximum ratio. The overall decoding characteristics can be improved.

It is a block diagram which shows the structure of the radio | wireless communications system by 1st embodiment of this invention. It is a figure which shows the state of transmission of each subpacket in slot # 1 and slot # 2. It is a flowchart of the process which transmits the information bit sequence of the transmission station in 1st embodiment, and the process which restore | restores the information bit sequence of a destination station. It is a flowchart which shows the process which demodulates by the data demodulation part by 1st embodiment. It is a flowchart of the process which decompress | restores an information bit sequence from the data demodulated soft decision value of the channel decoding part in 2nd embodiment. It is a conceptual diagram which shows an example of the cooperation protocol in the radio | wireless communications system which has 1R2H structure.

[First embodiment]
FIG. 1 is a block diagram showing a configuration of a wireless communication system 1 according to the first embodiment of the present invention. As shown in FIG. 1, a wireless communication system 1 includes a transmission station 11, a relay station 12, and a destination station 13 as communication devices, and has a 1R2H (1-Relay2-Hop) configuration using cooperative communication transmission. Have. In the wireless communication system 1, one slot of radio resources (time and frequency) is provided for transmission / reception from the transmission station 11 to the relay station 12 and transmission / reception from the transmission station 11 and the relay station 12 to the destination station 13. Assigned. In the wireless communication system 1, wireless communication is performed with two slots (slot # 1 and slot # 2) as one cycle.

  The transmission station 11, the relay station 12, and the destination station 13 perform wireless communication using OFDM modulation. The transmission station 11 transmits an information bit string to be transmitted to the destination station 13. The relay station 12 relays and transmits the information bit string received from the transmission station 11 to the destination station 13. The destination station 13 receives information bit strings from the transmission station 11 and the relay station 12. Hereinafter, the radio | wireless communications system 1 at the time of applying AF method as a relay station forward system is demonstrated.

  The transmitting station 11 includes a channel encoding unit 111, a data modulation unit 112, a space-time encoding unit 113, a frequency-time conversion unit 114, and a passband conversion unit 115. An information bit string (information bit stream) transmitted to the destination station 13 is input to the channel encoding unit 111. The channel coding unit 111 performs error correction coding on the input information bit string, and converts the information bit string into coded bits. Channel encoding section 111 then outputs the obtained encoded bits.

  The data modulation unit 112 performs constellation mapping of each of the M coded bits output from the channel coding unit 111 using a predetermined conversion rule, and converts the coded bits into complex QAM (Quadrature Amplitude Modulation) signal points. . Here, M is a modulation multi-value number. At this time, the data modulation unit 112 associates the converted complex QAM signal point with each subcarrier.

Here, the frequency domain complex signal point of the _i- th OFDM symbol for a certain subcarrier is denoted by X _i . The space-time coding unit 113 performs space-time coding on the frequency domain complex signal point X _i as follows.

  Here, the equations (15) and (16) are the signals that become the subpacket P1 and the subpacket P2 sent from the transmission station 11 to the slots # 1 and # 2, respectively. The i-th element of the vector corresponds to the i-th OFDM symbol of each subpacket. FIG. 2 is a diagram illustrating a transmission state of each subpacket in slot # 1 and slot # 2. As shown in FIG. 2, when a signal subjected to space-time coding is transmitted by the source station 11 and the relay station 12, the destination station 13 represents the following equation (17) in slot # 2: The synthesized signal is received.

The processing of the space-time coding unit 113 is performed by performing transmission processing with a set of OFDM symbols (X _21-1 , X ₂₁ ) of even numbers (two in this embodiment) as a set. Thus, the signal that has been conventionally synthesized as (H ₂₁ + H ₂₂ ) is synthesized as | H ₂₁ | ² + | H ₂₂ | ² . In other words, this is equivalent to the signal transmitted from the transmission station 11 and the signal transmitted from the relay station 12 being separated on the receiving side and subjected to channel equalization processing.

  The frequency-time conversion unit 114 converts each of the subpacket P1 and the subpacket P2 from a frequency domain signal to a time domain signal using IDFT, and converts the converted subpacket P1 and the converted subpacket P2. Output a packet containing.

  The passband conversion unit 115 converts the packet output from the frequency-time conversion unit 114 from baseband to passband (carrier frequency band). Further, among the converted packets, passband conversion section 115 transmits subpacket P1 in slot # 1 and transmits subpacket P2 in slot # 2 via the connected antenna. At this time, the passband conversion unit 115 transmits the subpacket P2 after the standby time Ds has elapsed after transmitting the subpacket P1.

  Here, the standby time Ds is determined in advance according to the processing time Dr required for the relay processing in the relay station 12. When the passband conversion unit 115 transmits the subpacket P2 after the time Ds elapses, the destination station 13 aligns the timing at which the subpacket P1 from the relay station 12 and the subpacket P2 are received. Note that a time lag due to a propagation path or the like is compensated by a guard interval.

  The destination station 13 includes a baseband converter 131, a time-frequency converter 132, a data demodulator 133, and a channel decoder 134. The baseband conversion unit 131 receives signals transmitted from the transmission station 11 and the relay station 12 via the connected antenna, converts the received signal from the passband to the baseband, and converts the converted signal to time. -It outputs to the frequency conversion part 132.

  The time-frequency conversion unit 132 removes the guard interval from the signal input from the baseband conversion unit 131 and converts the signal in the frequency domain from the time domain signal using DFT (Discrete Fourier Transform). And conversion. The data demodulator 133 performs channel equalization on the packet included in the signal converted by the time-frequency converter 132 based on the channel frequency response. Further, the data demodulating unit 133 detects a frequency domain complex signal point for each separated packet, and outputs a detection value (soft decision value) corresponding to each encoded bit to the channel decoding unit 135. The channel decoding unit 134 performs channel decoding on the detection value input from the data demodulation unit 133 and outputs a decoded information bit string.

  FIG. 3 is a flowchart of the process of transmitting the information bit string of the source station 11 and the process of restoring the information bit string of the destination station 13 in the first embodiment. FIG. 3A is a flowchart showing a transmission process in the transmission station 11. In the transmission station 11, when an information bit string is input to the channel encoder 111, the channel encoder 111 performs error correction encoding on the input information bit string at a predetermined encoding rate (step S101).

The data modulation unit 112 modulates the information bit sequence encoded by the channel encoding unit 111 (step S102). A complex QAM signal point obtained by modulation is associated with each subcarrier. Here, the frequency domain complex signal point of the _i- th OFDM symbol for a certain subcarrier is denoted by X _i .

The space-time coding unit 113 performs space-time coding on the frequency domain complex signal point X _{i as shown in} the following equations (18) and (19) (step S103).

  Here, Equations (18) and (19) are signals that become subpacket P1 and subpacket P2 sent from the transmitting station 11 to slot # 1 and slot # 2, respectively, and the i-th element of the vector is each subpacket Corresponds to the i th OFDM symbol.

  The frequency-time conversion unit 114 converts the subpacket P1 and the subpacket P2 into a time domain signal (step S104). Next, the passband conversion unit 115 converts the signal converted by the frequency-time conversion unit 114 into a passband, and transmits it through the antenna (step S105).

  FIG. 3B is a flowchart showing reception processing in the destination station 13. The baseband conversion unit 131 receives signals transmitted from the transmission station 11 and the relay station 12 via the antenna, and converts the received signals to baseband (step S201). Next, the time-frequency conversion unit 132 converts the signal converted by the baseband conversion unit 131 into a frequency domain signal (step S202).

  The data demodulator 133 demodulates the data included in the subpacket P1 and the subpacket P2 from the signal converted by the baseband converter 131, and outputs each soft decision value (step S203). Details of step S203 will be described later.

  The channel decoding unit 134 performs error correction decoding using the soft decision value output from the data demodulation unit 133, restores the information bit string, and outputs it (step S204 in FIG. 3B).

  FIG. 4 is a flowchart showing processing for performing demodulation of the data demodulator 133 according to the first embodiment. In the destination station 13, the reception signal Y input to the data demodulation unit 133 is expressed as the following equation (20).

Here, Y _{d1 and 2l-1} are received signals corresponding to odd-numbered OFDM symbols in slot # 1, and _Yd1 and _2l are received signals corresponding to even-numbered OFDM symbols in slot # 1. , Y _d2 , _21-1 are received signals corresponding to odd-numbered OFDM symbols in slot # 2, and Y _d2 , ₂₁ are received signals corresponding to even-numbered OFDM symbols in slot # 2.

H ₁₁ is a channel frequency response between the transmission station 11 and the destination station 13 in the slot # 1. H ₂₁ is a channel frequency obtained by combining the channel frequency response between the transmission station 11 and the relay station 12 in the slot # 1 and the channel frequency response between the relay station 12 and the destination station 13 in the slot # 2. It is a response. H ₂₂ is the channel frequency response between the source station 11 and the destination station 13 in slot # 2. W _d1,2l-1 and W _d1,2l are thermal noises in the slot # 1, and W _d2,2l-1 and W _d2,2l are thermal noises in the slot # 2.

The data demodulation unit 133 performs a complex conjugate on a received signal _{Y D1,2l} and _{Y D2,2l} corresponding to the even-numbered OFDM symbol (step S301). At this time, Expression (20) becomes the following Expressions (21) and (22).

  Here, Expression (21) and Expression (22) are expressed by row vectors and matrices, and expressed by the following Expressions (23) and (24).

Subsequently, the data demodulating unit 133 performs synthesis on the y ₁ and y ₂ (step S302). For example, when the maximum ratio combining is performed in the combining here, an output obtained by decoding the received signal obtained by the maximum ratio combining is expressed by the following equation (25).

Here, x with a hat (^) is a detected value of x = [X ₁ X ₂ ]. Moreover, about the right side of Formula (25),

It is. With respect to Equation (27), | H ₂₁ | ² + | H ₂₂ | ² and channel power can be separated by decoding. From this, it is possible to solve the problem that the received signal of slot # 2 is attenuated when H ₂₁ and H ₂₂ are in opposite phases.

X _i with a hat (^) represents a detection value of a complex QAM signal point. By performing constellation demapping on this value, a soft decision of the coded bit represented by the right side of the following equation (28) is obtained.

  In the first embodiment described above, space-time coding is performed on the transmission side, and complex conjugate processing is performed on even-numbered symbols on the reception side. The reception side can improve the overall decoding characteristics by combining the results of the reception signals of the first and second slots with the maximum ratio.

[Second Embodiment]
The second embodiment of the present invention can be applied to the channel decoding unit 134 of the destination station 13 in combination with the first embodiment. The configurations of the communication system 1, the transmission station 11, the relay station 12, and the destination station 13 are the same as those in FIG.
Similarly to the flowchart shown in FIG. 3B, the channel decoding unit 134 of the destination station 13 performs error correction decoding using the soft decision value output from the data demodulation unit 133, restores and outputs the information bit string (step S204). ).

  FIG. 5 is a flowchart of the process of restoring the information bit string from the data-demodulated soft decision value of the channel decoding unit 134 in the second embodiment. The soft decision b value input to the channel decoding unit 134 takes into account the sum of the noise component contained in the subpacket P1 forwarded by the relay station 12 and the additional noise of the destination station 13 as the noise component value of slot # 2. Bit likelihood weighting as shown in the following equation (29) is performed (step S401).

  By performing weighting in this way, decoding can be performed with the maximum likelihood, and an improvement in error characteristics can be obtained.

Next, the channel decoding unit 134 performs channel decoding using the soft decision b value subjected to the bit likelihood weighting, restores the information bit string, and outputs it (step S402).
In the second embodiment described above, the bit likelihood weighting considering the sum of the noise component included in the packet forwarded by the relay station 12 and the additional noise at the destination station 13 as the noise component value of the slot # 2 is performed. Done. The characteristics can be improved by performing soft decision channel decoding on the weighted values.

  In the first embodiment and the second embodiment described above, the channel encoding unit 111 performs predetermined scrambling on the input information bit sequence in order to prevent the information bit sequence transmitted to the destination station 13 from leaking. Scrambling may be performed using a code.

  Further, the channel encoding unit 111 may add a cyclic shift delay (CSD) in order to reduce the influence of the multipath wave.

  In the first and second embodiments described above, the case where OFDM modulation is used as a multicarrier system has been described. However, the present invention is not limited to this, and a single carrier system may be used.

  In the first embodiment and the second embodiment described above, the case where OFDM modulation is used as the multicarrier system has been described. However, the present invention is not limited to this, and Orthogonal Frequency Division Multiple Access (OFDMA) A system or multi-carrier code division multiple access (MC-CDMA) may be used.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 11 ... Originating station, 12 ... Relay station, 13 ... Destination station, 111 ... Channel encoding part, 112 ... Data modulation part (modulation part), 113 ... Space-time encoding part, 114 ... Frequency- Time conversion unit, 115 ... passband conversion unit (transmission unit), 131 ... baseband conversion unit (reception unit), 132 ... time-frequency conversion unit, 133 ... data demodulation unit (demodulation unit), 134 ... channel decoding unit ( Decryption unit)

Claims (5)

A modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols;
A space-time coding unit that performs space-time coding on the symbol sequence to generate a first signal and a second signal;
A transmitter that wirelessly transmits the first signal in a first time slot obtained by time-sharing one wireless channel, and wirelessly transmits the second signal in a second time slot obtained by the time-division. A transmitting station comprising and
A relay station comprising: a relay transmitter that receives the first signal transmitted by the source station in the first time slot and transmits the first signal in the second time slot;
In the first time slot, the first signal transmitted by the source station is received, and in the second time slot, the second signal transmitted by the source station and the relay station transmitted by the relay station. A receiving unit for receiving a combined signal with the first signal;
Complex conjugate processing is performed on even-numbered symbol sequences of the composite signal received in the second time slot, and the result of the complex conjugate processing and the first signal received in the first time slot , And a demodulator that performs demodulation processing based on
A destination station comprising: a decoding unit that performs a decoding process based on a result of the demodulation process;
A wireless communication system including:   2. The wireless communication system according to claim 1, wherein the space-time coding unit generates the first signal and the second signal by performing space-time coding with the even number of symbols as a set. . A modulation step in which a transmitting station modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols;
A space-time coding step in which the transmitting station performs space-time coding on the symbol sequence to generate a first signal and a second signal;
The transmitting station wirelessly transmits the first signal in a first time slot obtained by time-division of one radio channel, and transmits the second signal in a second time slot obtained by the time division. A transmission step for wireless transmission;
A relay transmission step in which a relay station receives the first signal transmitted by the source station in the first time slot and transmits the first signal in the second time slot;
A destination station receives the first signal transmitted by the source station in the first time slot, and the second signal transmitted by the source station and the relay station in the second time slot. A receiving step of receiving a composite signal with the first signal transmitted by;
The destination station performs complex conjugate processing on the even-numbered symbol sequence of the composite signal received in the second time slot, and the result of the complex conjugate processing and the received in the first time slot A demodulation step for performing a demodulation process based on the first signal;
A decoding step in which the destination station performs a decoding process based on a result of the demodulation process. A modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and a space-time that performs space-time coding on the symbol sequence to generate a first signal and a second signal An encoding unit wirelessly transmits the first signal in a first time slot obtained by time-division of one radio channel, and transmits the second signal in a second time slot obtained by the time division. A transmitting station including a transmitting unit that wirelessly transmits the first signal transmitted by the transmitting station in the first time slot, and transmits the first signal in the second time slot; A relay station having a relay transmitter, and a destination station that receives a radio signal from the relay station,
In the first time slot, the first signal transmitted by the source station is received, and in the second time slot, the second signal transmitted by the source station and the relay station transmitted by the relay station. A receiving unit for receiving a combined signal with the first signal;
Complex conjugate processing is performed on even-numbered symbol sequences of the composite signal received in the second time slot, and the result of the complex conjugate processing and the first signal received in the first time slot , And a demodulator that performs demodulation processing based on
A destination station comprising: a decoding unit that performs a decoding process based on a result of the demodulation process. A modulation unit that modulates an information bit sequence to be transmitted to generate a symbol sequence including a plurality of symbols, and a space-time that performs space-time coding on the symbol sequence to generate a first signal and a second signal An encoding unit wirelessly transmits the first signal in a first time slot obtained by time-division of one radio channel, and transmits the second signal in a second time slot obtained by the time division. A transmitting station including a transmitting unit that wirelessly transmits the first signal transmitted by the transmitting station in the first time slot, and transmits the first signal in the second time slot; A wireless communication method performed by a relay station including a relay transmission unit and a destination station that receives a radio signal from the relay station,
In the first time slot, the first signal transmitted by the source station is received, and in the second time slot, the second signal transmitted by the source station and the relay station transmitted by the relay station. A receiving step of receiving a composite signal with the first signal;
Complex conjugate processing is performed on even-numbered symbol sequences of the composite signal received in the second time slot, and the result of the complex conjugate processing and the first signal received in the first time slot A demodulation step for performing a demodulation process based on
And a decoding step of performing a decoding process based on a result of the demodulation process.

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