JP2009049937A - Wireless communication system and relay wireless device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system in which mutual cancellation of relay signals in radio signals transmitted from a relay wireless device is reduced when performing communication via a plurality of relay wireless devices. <P>SOLUTION: The wireless communication system 1 comprises a calling-side wireless device 2-1, relay wireless devices 2-2-1, 2-2-2 and a called-side wireless device 2-3. The relay wireless devices 2-2-1, 2-2-2 demodulate signals received from the calling-side communication device 2-1 using demodulators 2-2-1-2, 2-2-2-2, respectively. A re-modulator 2-2-1-3, 2-2-2-3 re-modulates demodulated signals to produce a relay signal. A cyclic shift retarder 2-2-1-4, 2-2-2-4 cyclically shifts a part of symbols of a relay signal having a length corresponding to delay of the relay signal, between an own relay wireless device and another relay wireless device, that is generated in reception at the called-side wireless device 2-3 for each symbol of the relay signal and transmits the cyclically shifted relay signal to the called-side wireless device 2-3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication system that performs information transmission via a wireless section, and in particular, a wireless that realizes high-quality and long-distance wireless transmission by using a relay wireless device between a transmission side device and a reception side device. The present invention relates to a communication system and a relay radio apparatus.

  In a wireless communication system that transmits and receives data via a wireless signal, the wireless signal is attenuated according to the propagation distance. Therefore, the longer the propagation distance between the originating wireless device and the terminating wireless device is, the longer the received signal becomes. There is a problem that quality deteriorates. In order to solve this problem, it is only necessary to transmit a radio signal using a large amount of power in the transmitting side radio device. However, the radio device hardware restrictions such as the amplifier output and antenna gain of the transmitting side radio Since there is an upper limit on transmission output by law, there is a limit to increasing the power of the transmitting side radio device.

  Therefore, in recent years, cooperative relay transmission using a relay wireless device has been studied in order to realize high-quality wireless transmission even when the propagation distance is long (see, for example, Non-Patent Document 1). FIG. 9 is a diagram illustrating a wireless communication system 1 that performs cooperative relay transmission, in which one transmission-side wireless device 1-1, two relay wireless devices 1-2-1, 1-2-2, It is composed of one incoming-side wireless device 1-3. If direct transmission is performed between the originating wireless device and the terminating wireless device without using the relay wireless device, communication is performed via the propagation path h_SD indicated by the broken line in FIG. On the other hand, in cooperative relay transmission, the information signal transmitted from the originating side radio device 1-1 is transmitted via the propagation paths h_SR (1) and h_SR (2) to the relay radio devices 1-2-1, 1-2- Received on 2.

  Here, h_SR (k) represents a propagation path between the transmission side radio apparatus 1-1 and the relay radio apparatus 1-2-k (k = 1, 2), and the relay radio apparatus 1-2 -k relay processing includes a regenerative relay system that first receives and decodes a signal transmitted by a transmitting-side radio apparatus, reproduces it as information, and then re-encodes and modulates to generate a transmission signal. There is a non-regenerative relay method in which signal processing or amplification processing is performed in a state of any one of frequency, intermediate frequency, and baseband, and transmission is performed as a radio signal. Here, the regenerative relay system will be described.

  The relay signal received, demodulated, and re-modulated by the relay radio devices 1-2-1 and 1-2-2 is transmitted to the receiving radio device 1-3 via the propagation paths h_RD (1) and h_RD (2). Sent. Here, h_RD (k) represents a propagation path between the relay radio apparatus 1-2-k and the called radio apparatus 1-3. The receiving-side radio apparatus 1-3 receives and demodulates a plurality of relay signals that are combined in space and arrive at the same time.

By performing the above operation, the propagation path is divided into h_SR (k) and h_RD (k) around the repeater. The transmission signal is once received by the relay radio apparatuses 1-2-1 and 1-2-2, amplified after being remodulated by an amplifier included in each relay radio apparatus, and transmitted to the terminating radio apparatus 1-3.
Therefore, from the viewpoint of the transmitting side radio apparatus 1-1, it is possible to perform high-quality transmission with less power than when a signal is directly transmitted to the receiving side radio apparatus 1-3. Further, relay transmission is performed by a plurality of relay radio apparatuses 1-2-1 and 1-2-2, and signals are simultaneously transmitted to the callee-side radio apparatus 1-3. Since the same number of transmission signals as the number of relay radio apparatuses are combined and received in space, a space diversity effect can be obtained.
A. Sendonaris, E, Erkip, and B. Aazhang, "User Cooperation Diversity Part I: System Description", IEEE Transaction on Communications, Vol. 51, No. 11, November 2003.

However, in the above-described prior art, depending on the state of the propagation environment between each relay radio device 1-2-1, 1-2-2 and the terminating radio device 1-3, a plurality of relay radio devices 1-2- The relay signals transmitted from 1, 1-2-2 to the receiving wireless device 1-3 cancel each other, and the received signal strength of the receiving wireless device 1-3 decreases, so that the reception quality decreases. A problem occurs.
Here, when the same signal is transmitted from each relay radio device 1-2-1, 1-2-2 at the same timing, and a signal synthesized in space is received by the terminating radio device 1-3, From the viewpoint of the terminating wireless device 1-3, the relay signal is a delay that combines the complex delay profile between each terminating wireless device 1-2-1, 1-2-2 and the terminating wireless device 1-3. It will be observed equivalent to that received after passing through the propagation path represented by the profile (delay characteristic information).

  For example, in the prior art, when each delay profile of h_RD (1) and h_RD (2) is a two-wave model as shown in the left diagram of FIG. 10, the synthesized delay profile is shown in the right diagram of FIG. It becomes like this. In FIG. 10, j represents an imaginary unit. In this case, the received signal power in the incoming side radio apparatus 1-3 is lowered, and the communication quality is greatly degraded. In particular, the time spread of the delay profile of the propagation path between each relay radio apparatus 1-2-1, 1-2-2 and the terminating radio apparatus 1-3 in a rice fading environment that is a line-of-sight propagation path or a non-line-of-sight environment Is small, that is, when the number of delay waves constituting the delay profile is small, the communication quality deterioration due to the event that the preceding waves cancel each other out of phase is significant.

  The present invention has been made to solve the above problem, and its purpose is to cancel relay signals in a radio signal transmitted from a relay radio device when communication is performed via a plurality of relay radio devices. It is an object of the present invention to provide a radio communication system and a relay radio apparatus that reduce the frequency.

  In order to solve the above-described problem, the present invention provides a transmission side communication device that transmits a signal, a plurality of relay wireless devices that relay a signal transmitted from the transmission side communication device and transmit the signal by a radio signal, A wireless communication system including a receiving wireless device that receives a wireless signal from a relay wireless device, wherein the relay wireless device generates a relay signal by performing modulation based on a signal received from the transmitting communication device A part of the symbol of the relay signal having a length corresponding to the delay of the relay signal between the self-relay wireless device and the other relay wireless device generated at the time of reception of the receiving-side wireless device; A wireless communication system comprising: cyclic shift delay means for cyclically shifting each symbol of the relay signal and transmitting the cyclically shifted relay signal to the terminating radio device.

  According to the present invention, in the above-described invention, delay profile information indicating a delay state of a communication path to the terminating radio device for each relay radio device is detected, and based on the detected delay profile information. The amount of cyclic shift, which is the length of a part of the symbol to be circulated in the symbol of the relay signal, reduces the temporal overlap of the delay characteristics of the communication path from the plurality of relay radio devices to the destination radio device. Cyclic shift delay amount control means for calculating, wherein the cyclic shift delay means cyclically shifts the symbol of the relay signal based on the cyclic shift amount calculated by the cyclic shift delay amount control means. .

  Further, the present invention is characterized in that, in the above-described invention, the relay radio apparatus and the called radio apparatus perform modulation and demodulation by orthogonal frequency division multiplexing on radio signals to be transmitted and received.

  In the invention described above, the relay radio device and the called radio device perform modulation and demodulation by single carrier block transmission in which a cyclic prefix is added to a radio signal to be transmitted and received. Features.

  Further, the present invention is the above-described invention, wherein the originating communication device and the relay wireless device perform wireless communication, and the originating communication device, the relay wireless device, and the terminating wireless device are And a plurality of antennas, and wireless communication by MIMO transmission is performed by the plurality of antennas.

  Further, the present invention is the above-described invention, wherein the cyclic shift delay means is configured to transmit the relay signal having a length corresponding to a delay generated at the time of reception by the receiving radio device for each of the plurality of antennas. A part of the symbols is cyclically shifted for each symbol of the relay signal, and the cyclically shifted relay signal is transmitted to the terminating radio apparatus.

  Further, the present invention is the above-described invention, wherein the cyclic shift delay amount control means is information on a delay profile that indicates a delay state of a communication path to the destination radio device for each of a plurality of antennas of the relay radio device. A symbol to be circulated in the symbol of the relay signal that reduces the time overlap of the delay characteristics of the communication path to the receiving-side radio apparatus for each of the plurality of antennas based on the detected delay profile information The cyclic shift delay means calculates the amount of cyclic shift based on the cyclic shift amount for each of the plurality of antennas calculated by the cyclic shift delay amount control means. The symbol is cyclically shifted.

  The present invention also provides a transmitting communication device that transmits a signal, a plurality of relay wireless devices that relay a signal transmitted from the transmitting communication device and transmits a wireless signal, and a wireless signal from the relay wireless device A receiving wireless device, a relay wireless device in a wireless communication system comprising: modulation means for generating a relay signal by performing modulation based on a signal received from the transmitting communication device; A part of the symbol of the relay signal having a length corresponding to the delay of the relay signal between the own relay radio device and another relay radio device generated at the time of reception of the radio device is circulated for each symbol of the relay signal. A cyclic radio apparatus comprising cyclic shift delay means for transmitting a cyclic signal that has been shifted and cyclically shifted to the terminating radio apparatus.

According to the present invention, the wireless communication system generates a relay signal by performing modulation based on a signal received from the originating communication device, and the self-relay wireless device and other relays that are generated when receiving the receiving wireless device. A part of the symbols of the relay signal having a length corresponding to the delay of the relay signal with the wireless device is cyclically shifted for each symbol of the relay signal, and the cyclically shifted relay signal is transmitted to the terminating wireless device. .
As a result, it is possible to add a delay to each relay signal by individually performing a cyclic shift on the relay signals transmitted by a plurality of relay radio apparatuses. It is possible to reduce the probability that relay signals cancel each other out in the wireless device, enhance the space diversity effect, and obtain stable communication quality.

According to the present invention, the delay profile information indicating the delay state of the communication path to the terminating radio device for each relay radio device is detected, and based on the detected delay profile information, a plurality of relay radio devices are used. Calculate the amount of cyclic shift that is the length of a part of the symbol to be circulated in the symbol of the relay signal to reduce the time overlap of the delay characteristics of the communication path to the called wireless device, and to calculate the amount of cyclic shift Based on this, the symbols of the relay signal are cyclically shifted.
This makes it possible to set the optimal amount of cyclic shift according to the detected delay state of the communication path for each of the plurality of relay wireless devices, and stable communication even when there are fluctuations in the delay state of the communication path, etc. Quality can be obtained.

Further, according to the present invention, the relay radio apparatus and the called radio apparatus are configured to perform modulation and demodulation by orthogonal frequency division multiplexing on radio signals to be transmitted and received.
Therefore, by applying an orthogonal frequency division multiplexing (OFDM) modulation scheme to a radio communication system for cooperative relay transmission, it is possible to provide strong resistance to multipath fading.

Further, according to the present invention, the relay radio apparatus and the incoming radio apparatus are configured to perform modulation and demodulation by single carrier block transmission with a cyclic prefix added to radio signals to be transmitted and received.
Therefore, by using single carrier block transmission to which a cyclic prefix is added as a modulation method for a radio communication system for cooperative relay transmission, it is possible to have strong resistance against multipath fading.

Further, according to the present invention, the transmission side communication device and the relay radio device perform wireless communication, and the transmission side communication device, the relay radio device, and the call reception side wireless device include a plurality of transmission antennas, The wireless communication is performed by MIMO transmission using a plurality of transmission antennas.
As a result, a MIMO channel can be configured, and a wireless communication system that performs cooperative relay transmission with high quality and high transmission rate can be realized.

In addition, according to the present invention, a part of the symbols of the relay signal having a length corresponding to the delay generated at the time of reception by the receiving radio apparatus for each of the plurality of antennas is cyclically shifted for each symbol of the relay signal. In this configuration, the cyclically-shifted relay signal is transmitted to the terminating wireless device.
As a result, it is possible to individually perform cyclic shifts for relay antennas transmitted from a plurality of relay radio apparatuses for each antenna of the relay radio apparatus, reducing the probability that the relay signals cancel each other at the receiving radio apparatus, and stabilizing Communication quality can be obtained.

Further, according to the present invention, the delay profile information indicating the delay state of the communication path to the terminating wireless device for each of the plurality of antennas of the relay wireless device is detected, and based on the detected delay profile information, Calculate the amount of cyclic shift that is the length of a part of the symbol to be circulated in the symbol of the relay signal to reduce the temporal overlap of the delay characteristics of the communication path to the receiving radio device for each antenna, The relay signal symbol is cyclically shifted based on the amount of cyclic shift for each antenna.
This detects delay profile information when individually adding a cyclic shift delay for each relay radio device antenna to relay signals transmitted by a plurality of relay radio devices, and based on the detected delay profile information An optimum amount of cyclic shift can be set for each of a plurality of antennas, and stable communication quality can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic block diagram showing a wireless communication system 2 that performs cooperative relay transmission according to a first embodiment of the present invention. The wireless communication system 2 includes one transmission-side wireless device 2-1, two relay wireless devices 2-2-1 and 2-2-2, and one reception-side wireless device 2-3.

  The transmission side radio apparatus 2-1 includes a modulator 2-1-1 that modulates an input transmission information sequence, and a transmission antenna 2-1-2. The relay radio apparatus 2-2-1 remodulates the signal demodulated by the receiving antenna 2-2-1-1, demodulator 2-2-1-2, and demodulator 2-2-1-2. A remodulator 2-2-1-3 that performs transmission, a cyclic shift delay unit 2-2-1-4 that performs cyclic shift described later on the signal, and a transmission antenna 2-2-1-5. Prepare. The relay radio apparatus 2-2-2 decodes the signal demodulated by the receiving antenna 2-2-2-1, demodulator 2-2-2-2, and demodulator 2-2-2-2. A remodulator 2-2-2-3 for performing re-modulation and re-encoding, a cyclic shift delay unit 2-2-2-4 for performing a cyclic shift described later on the signal, and a transmitting antenna 2-2-2 2-5. The incoming-side radio apparatus 2-3 includes a reception antenna 2-3-1, and a demodulator 2-3-2 that demodulates the received signal into a received signal sequence.

  Here, the modulator 2-1-1 of the transmission side radio apparatus 2-1 and the remodulators 22-1-3, 2 provided in the relay radio apparatuses 2-2-1 and 2-2-2 are described. -2-2-3 shall perform the same modulation. Also, the demodulator 2-2-1-2 and 2-2-2-2 of the relay radio equipment 2-2-1 and 2-2-2 and the demodulator 2-3-2 of the incoming radio equipment 2-3 Shall perform the same demodulation.

  Hereinafter, as an example, an OFDM (Orthogonal Frequency Division Multiplexing) signal is used as a modulation method in the transmission side radio apparatus 2-1, the relay radio apparatuses 2-2-1 and 2-2-2, and the reception side radio apparatus 2-3. The case where it is used will be described.

  The transmission information sequence input to the transmitting-side radio apparatus 2-1 is converted into an OFDM signal by the modulator 2-1-1. The modulator 2-1-1 converts the modulated OFDM signal into the transmitting-side radio apparatus 2-1 Is transmitted to the radio section through the transmission antenna 2-1-2. The transmitted OFDM signal is received by the receiving antennas 2-2-1-1 and 2-2-2-1 of the relay radio apparatuses 2-2-1 and 2-2-2 through the radio section. The received signals received by the receiving antennas 2-2-1-1, 2-2-2-1 are demodulator 2-2-1-2, 2- of the relay radio equipment 2-2-1, 2-2-2. In 2-2-2, after being demodulated once into an information sequence, it is input to the remodulators 2-2-3-3, 2-2-3, and the remodulators 22-1-3, Converted to OFDM signal by 2-2-2-3.

  Cyclic shift delay units 2-2-1-4 and 2-2-2-4 are provided for each of the relay radio apparatuses 2-1-1 and 2-2-2 for the converted OFDM signal. Shift. The transmission antennas 2-2-1-5 and 2-2-2-5 of the relay radio apparatuses 2-1-1 and 2-2-2 send the relay signal subjected to the cyclic shift to the incoming-side radio apparatus 2-3. To the same timing. The OFDM signals transmitted from the two relay wireless devices 2-2-1 and 2-2-2 are combined in space and received by the receiving antenna 2-3-1 of the receiving wireless device 2-3. The demodulator 2-3-2 of the side radio apparatus 2-3 demodulates the received information sequence.

The difference between the above-described conventional technology and the first embodiment is obtained by cyclic shift delay devices 2-2-1-4 and 2-2-2-4 of relay radio apparatuses 2-2-1 and 2-2-2. The point is that the cyclic shift is individually performed on the relay signal. Here, it is assumed that the complex delay profiles (delay characteristic information) of h_RD (1) and h_RD (2) are the same as those in the left diagram of FIG. At this time, for example, the cyclic shift delay unit 2-2-1-4 does not perform a cyclic shift of 0 with respect to the relay signal, that is, does not perform cyclic processing. and a 2 × cyclic shift cyclically be allowed to indicate the portion of the symbol corresponding to the time length of the delay of t ₁ to (2) in the left view of FIG. 2 of one symbol of the relay signal went to relay signals. Here, the amount of cyclic shift performed by each of the cyclic shift delay units 2-2-1-4 and 2-2-2-4 (hereinafter also referred to as cyclic shift delay amount) is h_RD (1) and h_RD. Cyclic shift delay devices 2-2-1-4 and 2-2-2-4 of relay radio apparatuses 2-2-1 and 2-2-2 so that there is less time overlap in the delay profile of (2) Is a value set in advance.

In this case, the signal transmitted from the relay wireless devices 2-2-2 becomes equivalent to that the delay time of 2 × t ₁ has expired addition, the terminating wireless device 2, and the relay wireless devices 2-2-2 The complex delay profile between 3 and 3 is observed as a signal delayed by 2 × t ₁ as shown in the right diagram of FIG. Therefore, in such a case, the delay profile obtained by combining the propagation path h_RD (1) and the propagation h_RD (2) observed in the receiving-side radio apparatus 2-3 is as shown on the right side of FIG.

In the case of the prior art that does not use cyclic delay shift in the relay radio apparatus 2-2-2, delayed wave components having opposite phases to each other arrive at the same time as shown in FIG. In contrast to the fact that the power is significantly reduced, in the first embodiment, as shown in FIG. 3, since the delayed waves are received without canceling each other, the received signal power in the incoming side radio apparatus 2-3 is significantly higher. There is an effect that the probability of the decrease is lowered and the communication quality is stabilized.

  Note that the modulator 2-1-1 of the transmitting side radio device 2-1 and the demodulator 2-2-1-2, 2-2-2-2 of the relay radio devices 2-2-1 and 2-2-2 Remodulators 2-2-1-3, 2-2-2-3 and cyclic prefix instead of the OFDM mentioned above as the modulation method used by the demodulator 2-3-2 of the receiving side radio device 2-3 Single carrier block transmission to which is added may be used.

  Due to the configuration of the first embodiment described above, the relay signal transmitted by the relay radio apparatus 2-2-1, 2-2-2 is specific to each relay radio apparatus 2-2-1, 2-2-2. As a result of performing cyclic shift of the above, an effect equivalent to adding a delay time to the entire complex delay profile between each relay radio device 2-2-1 and 2-2-2 and the terminating radio device 2-3 is obtained. It becomes possible to give. This reduces the probability that the received signal strength will drop due to cancellation of the combined relay signals received at the receiving side radio device 2-3, thereby improving the spatial diversity effect and improving the transmission quality Can be realized.

  In the first embodiment, the transmission side radio apparatus 2-1, the relay radio apparatuses 2-2-1 and 2-2-2, the transmission antenna 2-1-2 of the reception side radio apparatus 2-3, and transmission The antennas 2-2-1-5,2-2-2-5, the receiving antennas 2-2-1-1, 2-2-2-1, and the receiving antenna 2-3-1 are physically different It is supposed to be. However, for example, in the case of a system that performs communication by dividing the uplink and downlink having different communication directions by time using the same frequency, such as a TDD (Time Division Duplex) system, The antenna can be shared for transmission and reception.

  In addition, the communication path between the originating wireless device 2-1 and the relay wireless devices 2-2-1 and 2-2-2 does not have to be a wireless line, instead of the originating wireless device 2-1 Equipped with a communication device on the transmission side, instead of the relay wireless device 2-2-1 and 2-2-2, the transmission side has a terminal for wired connection, and the transmission side has a transmission antenna 2-2-1-5 , 2-2-2-5, a relay wireless device that transmits a wireless signal to the called wireless device 2-3 may be provided. In such a case, the replaced transmission side communication device and the relay wireless device are connected by a wired connection such as an optical fiber, and the relay wireless device receives the transmission information sequence transmitted from the transmission side communication device through the wired connection. Become.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is a schematic block diagram showing the configuration of the wireless communication system 3 that performs cooperative relay transmission in the second embodiment. The wireless communication system 3 includes one transmission-side wireless device 3-1, two relay wireless devices 3-2-1 and 3-2-2, and one reception-side wireless device 3-3. The relay radio apparatuses 3-2-1 and 3-2-2 and the receiving radio apparatus 3-3 each have one antenna, and the relay radio apparatuses 3-2-1 and 3-2- Transmission and reception in 2 are switched by the TDD switch.

  The transmission side radio apparatus 3-1 includes a modulator 3-1-1 and a transmission antenna 3-1-2. The relay radio devices 3-2-1 and 3-2-2 are configured by transmitting and receiving antennas 3-2-1-1, 3-2-2-1 and TDD switches 3-2-1-2, 3-2-2, respectively. 2-2, demodulator 3-2-1-3, 3-2-2-3, remodulator 3-2-1-4, 3-2-2-4, cyclic shift delay unit 3- 2-1-5, 3-2-2-5, and cyclic shift delay amount control circuits 3-2-1-6, 3-2-2-6. The incoming-side wireless device 3-3 includes a transmitting / receiving antenna 3-3-1, a TDD switch 3-3-3, a demodulator 3-3-3, and a modulator 3-3-4.

  Modulator 3-1-1 of transmitting side radio equipment 3-1 and remodulator 3-2-1-4, 3-2-2-4 of relay radio equipment 3-2-1, 3-2-2 And the modulator 3-3-4 of the receiving side radio apparatus 3-3 performs the same modulation. Also, the demodulator 3-2-1-3, 3-2-2-3 of the relay radio equipment 3-2-1, 3-2-2 and the demodulator 3-3-3 of the incoming radio equipment 3-3 3 shall perform the same demodulation. As a modulation method used in each apparatus, in the following description, an OFDM signal is used as an example. In the system according to the second embodiment, the transmission-side wireless device 3-1 transmits a wireless packet to the reception-side wireless device 3-3 via the two relay wireless devices 3-2-1 and 3-2-2. The incoming-side radio devices 3 and 3 are systems that respond to the acknowledgment packet to the relay radio devices 3-2-1 and 3-2-2 when receiving the radio packet.

  FIG. 5 is a diagram illustrating an example of a temporal flow of operations of the transmission-side wireless device 3-1, the relay wireless devices 3-2-1 and 3-2-2, and the reception-side wireless device 3-3. In FIG. 5, the time length of the packet is indicated as T. The transmission information sequence is converted into an OFDM signal by the modulator 3-1-1 of the transmission side radio apparatus 3-1, and transmitted to the radio section by the transmission antenna 3-1-2 of the transmission side radio apparatus 3-1. The transmitted OFDM signal is received by the transmission / reception antennas 3-2-1-1, 3-2-2-1 of the relay radio apparatuses 3-2-1 and 3-2-2 through the radio section. The TDD switches 3-2-1-2 and 3-2-2-2 switch the transmission and reception antennas 3-2-1-1, 3-2- at the timing of receiving signals, that is, from time 0 to T. 2-1 is connected to the demodulator 3-2-1-3 and 3-2-2-3, and the received signal is output to the demodulator 3-2-1-3 and 3-2-2-3. . Then, at the timing of transmitting the signal, that is, from time T to 2T, the switch is switched so that the transmission / reception antenna 3-2-1-1, 3-2-2-1 is connected to the cyclic shift delay unit 3-2-1-. Connected to 5,3-2-2-5, and relay signal that is the output of cyclic shift delay units 3-2-1-5, 3-2-2-5 Output to 3-2-2-1.

  In the demodulator 3-2-1-3 and 3-2-2-3 of the relay radio apparatus 3-2-1 and 3-2-2, the relay signal is once demodulated into an information sequence and then remodulated. It is converted into an OFDM signal by 3-2-1-4 and 3-2-2-4. The OFDM signal is subjected to individual cyclic shift for each of the cyclic shift delay units 3-2-1-5 and 3-2-2-5 of the relay radio apparatuses 3-2-1 and 3-2-2. Same timing to the receiving side radio equipment 3-3 by the transmitting / receiving antenna 3-2-1-1, 3-2-2-1 via TDD switches 3-2-1-2 and 3-2-2-2 Sent by. The OFDM signals transmitted from the two relay radio apparatuses 3-2-1 and 3-2-2 are combined in space.

  The TDD switch 3-3-3 of the receiving side radio device 3-3 connects the transmission / reception antenna 3-3-1 to the demodulator 3-3-3 from time T to 2T, and combines the synthesized OFDM signal. Is received by the transmission / reception antenna 3-3-1 and the received OFDM signal is demodulated into an information sequence by the demodulator 3-3-3 of the receiving side radio apparatus 3-3. A determination is made as to whether or not the demodulated information sequence has been correctly received by the receiving wireless device 3-3. For example, since the information included in the packet is encoded with an error detection code, it is determined whether or not the information is correctly received. Then, the TDD switch 3-3-3 of the incoming-side wireless device 3-3 connects the transmission / reception antenna 3-3-1 to the modulator 3-3-4 between time 2T and time 3T and is correctly received. In this case, an ACK (Acknowledgement: Acknowledgment) packet is sent from the modulator 3-3-3 via the TDD switch 3-3-3 and the transmitting / receiving antenna 3-3-1. A NACK (Negative-ACK) packet modulator 3-3-4 transmits the data from the transmitting / receiving antenna 3-3-1 via the TDD switch 3-3-3. From time 2T to 3T, the TDD switches 3-2-1-2 and 3-2-2-2 of the relay radio apparatuses 3-2-1 and 3-2-2 3-2-2-1 and demodulator 3-2-1-3, 3-2-2-3, and demodulator 3-2-1-3, 3-2-2-3 The ACK packet or NACK packet is received through the transmitting / receiving antennas 3-2-1-1, 3-2-2-1, and the demodulated received signal is converted into a cyclic shift delay amount control circuit 3-2-1-6,3- Enter in 2-2-6.

  The amount of cyclic shift performed in the cyclic shift delay units 3-2-1-5 and 3-2-2-5 (cyclic shift delay amount) is the cyclic shift delay amount control circuit 3-2-1-6,3- Input from 2-2 and 6. In the cyclic shift delay amount control circuits 3-2-1-6, 3-2-2, and 6, based on the delay profile between the relay wireless device provided with the circuit and the terminating wireless device 3-3, The amount of cyclic shift is calculated so that the temporal overlap of the delay profile between the other relay wireless device and the called-side wireless device 3-3 is minimized, and the calculated cyclic shift amount is calculated as a cyclic shift delay device. Input to 3-2-1-5 and 3-2-2-5.

  Each relay radio device 3-2-1, 3-2-2 is used between the relay radio device 3-2-1, 3-2-2 and the terminating radio device 3-3 used to calculate the amount of cyclic shift. As a method for acquiring the delay profile information indicating the delay state of the communication path, there are the following methods. For example, when the incoming wireless device 3-3 receives a wireless packet from the relay wireless device in the section from time T to 2T in the bucket transmission / reception procedure of FIG. 5, a delay profile indicating the state of the communication path is detected.

  Then, a method of superimposing the detected delay profile on the ACK / NACK packet transmitted by the called wireless device 3-3 in the interval from 2T to 3T and notifying the relay wireless devices 3-2-1 and 3-2-2 There is. As a result, each of the cyclic shift delay amount control circuits 3-2-1-6, 3-2-2 and 6 has a delay profile between itself and the called radio apparatus 3-3, and other relay radio apparatuses. And the delay profile between the receiving wireless device 3-3 and the receiving side wireless device 3-3. In the example of FIG. 4, the cyclic shift delay amount control circuits 3-2-1-6, 3-2-2, and 6 are respectively connected between the relay wireless device 3-2-1 and the called wireless device 3-3. And the delay profile between the relay radio apparatus 3-2-2 and the called radio apparatus 3-3 can be acquired.

For any one of the relay radio apparatuses, the cyclic shift delay amount control circuits 3-2-1-6, 3-2-2, and 6 are set in advance so that the cyclic shift is not performed. For the relay wireless device, the amount of cyclic shift can be calculated based on the acquired delay profile. For example, when the relay radio apparatus 3-2-1 does not perform cyclic shift and the relay radio apparatus 3-2-2 is set to perform cyclic shift, the delay profile is the delay shown in FIG. when having spread, the relay wireless devices 3-2-2 towards performing cyclic shift to detect the spread t ₁ of the delay from the delay profile of the other relay wireless devices 3-2-1, detected t ₁ or more The amount of cyclic shift is calculated so as to cause the above delay, and the calculated amount of cyclic shift is input to the cyclic shift delay unit 3-2-2-5.

  There is also a technique that utilizes the symmetry of the uplink channel and downlink channel of the TDD wireless communication system. Specifically, in the section from time 2T to 3T, cyclic shift delay amount control circuits 3-2-1-6 and 3-2-2-6 of relay radio apparatuses 3-2-1 and 3-2-2 Detects the delay profile when receiving the ACK / NACK packet transmitted from the terminating wireless device 3-3, and obtains the delay profile from the terminating wireless device 3-3 to the local relay wireless device from the detected delay profile In this method, the delay profile from the self-relay wireless device to the terminating wireless device 3-3 is acquired by taking the complex conjugate of the acquired delay profile. When using this method, the cyclic shift delay amount control circuits 3-2-1-6 and 3-2-2-6 of the relay radio apparatuses 3-2-1 and 3-2-2 are connected to each other. The cyclic shift delay control circuits 3-2-1-6 and 3-2-2-6 of the relay radio devices 3-2-1 and 3-2-2 The delay profile between the device and the called wireless device 3-3 is acquired, and the acquired delay profile is acquired between the other cyclic shift delay amount control circuits 3-2-1-6 and 3-2-2-6. Performs transmission and reception, and there is little time overlap between the delay profile between its own relay wireless device and the called wireless device 3-3 and the delay profile between other relayed wireless devices and the called wireless device 3-3 The amount of cyclic shift is calculated as follows.

The information transmitted and received between the cyclic shift delay amount control circuits 3-2-1-6 and 3-2-2-6 includes, in addition to the delay profile information, whether or not it performs cyclic shift itself. In addition, information indicating this is also transmitted and received.
In addition, when there is a relay radio apparatus in which the amount of cyclic shift is already determined, information on the amount of cyclic shift determined from the relay radio apparatus is received, and the second and subsequent relay radio apparatuses are The amount of cyclic shift may be determined in order.

In the second embodiment, the two relay radio apparatuses 3-2-1 and 3-2-2 always perform cooperative relay transmission to the incoming radio apparatus 3-3. In the case of applying to a mesh network that performs exhaustive transmission by arranging exhaustively, it is assumed that a partner that performs cooperative relay transmission varies with the passage of time. In such a case, each cyclic shift delay amount control circuit controls the cyclic shift delay amount with reference to the cyclic shift delay amount and the delay profile currently used by the relay radio apparatus that is a partner that performs cooperative relay. A cyclic shift delay amount set in the relay radio apparatus to which the circuit belongs is set.
By performing such setting processing, it becomes possible to set an optimal cyclic shift delay amount for each relay signal with respect to the state of the communication path, even when the state of the communication path or the communication path changes. A high spatial diversity gain can be obtained.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a schematic block diagram showing the configuration of the wireless communication system 4 that performs cooperative relay transmission in the third embodiment. In the wireless communication system 4 according to the third embodiment, each of the transmission side wireless device, the relay wireless device, and the reception side wireless device performs cooperative relay transmission using MIMO (Multiple-Input Multiple-Output) transmission using two transmission / reception antennas. Do.

  In FIG. 6, the transmitting side radio apparatus 4-1 includes a modulator 4-1-1 and two transmitting antennas 4-1-2-1, 4-1-2-2. The relay radio devices 4-2-1 and 4-2-2 have two receiving antennas 4-2-1-1-1, 4-2-1-1-2 and receiving antennas 4-2-2-1, respectively. -1, 4-2-2-1-2, demodulator 4-2-1-2,4-2-2-2, remodulator 4-2-1-3,4-2-2- 3, two transmitting antennas 4-2-1-6-1, 4-2-1-6-2 and transmitting antennas 4-2-2-6-1, 4-2-2-6-2 And cyclic shift delay units 4-2-1-4-1, 4-2-1-4-2 provided for each transmitting antenna, and cyclic shift delay units 4-2-2-4-1, 4-2 -2-4-2 and cyclic shift delay amount control circuits 4-2-1-5 and 4-2-2-5. The terminating radio apparatus 4-3 includes two receiving antennas 4-3-1-1, 4-3-1-2 and a demodulator 4-3-2.

  Here, the modulator 4-1-1 of the transmission side radio apparatus 4-1 and the remodulator 4-2-1-3,4-2- of the relay radio apparatus 4-2-1, 4-2-2 2-3 shall perform the same modulation. Also, the demodulator 4-2-1-2 and 4-2-2-2 of the relay radio equipment 4-2-1 and 4-2-2, and the demodulator 4-3- of the incoming radio equipment 4-3 2 shall perform the same demodulation.

  As a modulation scheme used in each radio apparatus, a scheme that enables correct reception even when cyclic shift is performed is used. For example, Orthogonal Frequency Division Multiplexing (OFDM) with a guard interval added or single carrier block transmission with a cyclic prefix added can be considered. In the third embodiment, a case where an OFDM signal is used will be described as an example.

  The transmission information sequence is converted into an OFDM signal by the modulator 4-1-1 of the transmission side radio apparatus 4-1. In the third embodiment, the transmission-side radio apparatus 4-1 has a plurality of transmission antennas, and is arranged between the transmission-side radio apparatus 4-1 and each relay radio apparatus 4-2-1 and 4-2-2. Since a MIMO communication channel has been established, the transmission rate can be improved by spatial multiplexing using multiple transmit antennas, diversity gain can be obtained by STBC (Space Time Block Code) transmission, and transmit beamforming can be used for communication It becomes possible to take the form of improving quality.

  Two series of transmission signals are transmitted to the radio section by the two transmission antennas 4-1-2-1 and 4-1-2-2 of the transmission side radio apparatus 4-1-1. Each transmitted OFDM signal is transmitted to the two receiving antennas 4-2-1-1-1 and 4-2-1-1-2 for each relay radio device 4-2-1 and 4-2-2 throughout the radio section. Are received by the receiving antennas 4-2-2-1-1 and 4-2-2-1-2. The received signal is demodulated once into an information sequence by the demodulator 4-2-1-2 and 4-2-2-2 of the relay radio apparatus 4-2-1 and 4-2-2, and then remodulated. Input to 4-2-1-3 and 4-2-2-3, and converted into two series of OFDM signals. The converted OFDM signal includes cyclic shift delay units 4-2-1-4-1 and 4-2-1-4-2 and cyclic shift delay units 4-2-2-4-1 and 4-2-2. -4-2, a cyclic delay shift having a unique value is added to each transmission signal sequence of each relay radio apparatus, and then the two transmission antennas 4-2 of the relay radio apparatus 4-2-1 and 4-2-2 are added. Identical to the terminating wireless device 4-3 by -1-6-1, 4-2-1-6-2 and transmitting antennas 4-2-2-6-1, 4-2-2-6-2 It is transmitted at the timing.

  The amount of cyclic shift added in the cyclic shift delay unit is the cyclic shift delay amount control circuit 4-2-1-5, 4-2-2- in each relay radio apparatus 4-2-1, 4-2-2. 5 is set uniquely. Control information and propagation path information, that is, the delay profile described above are input to the cyclic shift delay amount control circuits 4-2-1-5 and 4-2-2-5 by the method exemplified in the second embodiment. Based on this, cyclic shift delay devices 4-2-1-4-1, 4-2-1-4-2 and cyclic shift delay devices 4-2-2-4-1, 4-2-2-4 Sets the amount of cyclic shift of -2. In the third embodiment, two relay radio apparatuses 4-2-1 and 4-2-2 each have two cyclic shift delay units 4-2-1-4-1, 4-2-1-4-2, and Since cyclic shift delay units 4-2-2-4-1 and 4-2-2-4-2 are provided, four types of cyclics are provided by two repeater radio devices 4-2-1 and 4-2-2. The amount of shift will be set.

  In the third embodiment, as in the first embodiment described above, the origination-side radio apparatus 4-1, relay radio equipment 4-2-1 and 4-2-2, and destination-side radio apparatus 4-3 The transmitting antenna and the receiving antenna are physically different. However, for example, a radio communication system that uses the same frequency for uplink and downlink, such as a time division multiplexing system, and a radio communication system that uses different frequencies for uplink and downlink, such as frequency division multiplexing, can transmit and receive. If the wireless communication system does not perform simultaneously, the antenna can be shared for transmission and reception.

  In addition, the communication path between the originating wireless device 4-1 and the relay wireless device 4-2-1, 4-2-2 need not be a wireless line, instead of the originating wireless device 4-1. Equipped with a communication device on the transmission side, instead of the relay wireless device 4-2-1 and 4-2-2, the transmission side has a terminal for wired connection, and the transmission side has a transmission antenna 4-2-1-6 -1,4-2-1-6-2 and relay radio that transmits a radio signal to the receiving radio device 4-3 through the transmitting antennas 4-2-2-6-1 and 4-2-2-6-2 You may make it provide an apparatus. In such a case, the replaced transmission side communication device and the relay wireless device are connected by a wired connection such as an optical fiber, and the relay wireless device receives the transmission information sequence transmitted from the transmission side communication device through the wired connection. Become.

(Computer simulation results)
Next, referring to FIGS. 7 and 8, the result of evaluating the packet error rate characteristic improvement effect by computer simulation for the wireless communication system 4 of the third embodiment will be described. FIG. 7 is a table showing simulation conditions.

  For comparison, as a method according to the prior art (hereinafter referred to as the conventional method), assuming a configuration in which two relay radio apparatuses each having two transmission antennas transmit the same signal to the incoming radio apparatus at the same time Yes. In the third embodiment, the cyclic shift delay units 4-2-1-4-1, 4-2-1-4-2 and the cyclic shift delay units of the relay radio apparatuses 42-1 and 4-2-2 The amount of cyclic shift specific to 4-2-2-4-1 and 4-2-2-4-2 will be set. In this simulation, the following amounts were set.

(1) First transmission antenna of first relay radio apparatus 4-2-1 4-2-1-6-1: 0 ns
(2) Second transmitting antenna of first relay radio apparatus 4-2-1 4-2-1-6-2: -800ns
(3) First transmission antenna of the second relay radio apparatus 4-2-2 4-2-26-1: 600 ns
(4) Second transmission antenna of second relay radio apparatus 4-2-2 4-2-26-2: -200ns

  In addition, as a simulation condition, it is assumed that there is no error in the wireless transmission between the transmitting side wireless device 4-1 and each of the relay wireless devices 42-1 and 4-2-2.

  FIG. 8 shows bucket error rate characteristics obtained as a result of computer simulation based on the above conditions. The horizontal axis represents the carrier-to-noise power ratio (CNR), and the vertical axis represents the packet error rate. Compared with the conventional method, the third embodiment of the present invention achieves an improvement effect of 3.3 dB when compared with the CNR for achieving a packet error rate of 0.001.

  This is because, when the present invention is applied, a unique cyclic shift amount is set for each relay radio apparatus and each transmission antenna, and delayed waves having large signal levels arrive at the same timing and in opposite phases and cancel each other. As a result, it is possible to improve the characteristics due to the stable reception quality.

1 is a block diagram showing an outline of a wireless communication system according to a first embodiment of the present invention. It is the figure which showed the cyclic shift of the symbol in the relay radio | wireless apparatus by the same embodiment, and the change of the delay profile observed in the receiving side radio | wireless apparatus. It is the figure which showed an example of the delay profile synthesize | combined in the receiving side radio | wireless apparatus at the time of performing cyclic shift separately for every relay radio | wireless apparatus by the same embodiment. It is the block diagram which showed the outline of the radio | wireless communications system by 2nd Embodiment of this invention. It is the figure which showed the example of operation | movement of the transmission side radio | wireless apparatus by the same embodiment, a relay radio | wireless apparatus, and the incoming side radio | wireless apparatus. It is the block diagram which showed the outline of the radio | wireless communications system by 3rd Embodiment of this invention. It is the figure which showed the conditions used for the computer simulation to which this invention is applied. It is the figure which showed the result by the computer simulation. 1 is a schematic diagram of a conventional cooperative relay transmission system. It is the figure which showed an example in which the quality of a received signal falls in the receiving side radio | wireless apparatus in the conventional cooperative relay transmission system.

Explanation of symbols

2-1 Originating wireless device
2-1-1 Modulator
2-1-2 Transmit antenna
2-2-1, 2-2-2 Relay radio equipment
2-2-1-1-, 2-2-2-1 Receive antenna
2-2-1-2, 2-2-2-2 Demodulator
2-2-1-3,2-2-2-3 Remodulator
2-2-1-4,2-2-2-4 Cyclic shift delay device
2-2-1-5,2-2-2-5 Transmit antenna
2-3 Incoming wireless device
2-3-1 Receiving antenna
2-3-2 Demodulator

Claims (8)

A transmitting side communication device that transmits a signal, a plurality of relay wireless devices that relay signals transmitted from the transmitting side communication device and transmit them by radio signals, and an incoming side radio that receives radio signals from the relay radio devices A wireless communication system comprising:
The relay wireless device is
Modulation means for generating a relay signal by modulating based on a signal received from the originating communication device;
A part of the symbol of the relay signal having a length corresponding to the delay of the relay signal between the self-relay radio device and another relay radio device generated at the time of reception of the incoming-side radio device is a symbol of the relay signal A cyclic shift delay means for cyclically shifting each time, and transmitting the cyclically shifted relay signal to the destination wireless device;
A wireless communication system comprising: Detect delay profile information indicating a delay state of a communication path to the terminating radio device for each relay radio device, and based on the detected delay profile information, the plurality of relay radio devices to the terminating radio device A cyclic shift delay amount control means for calculating a cyclic shift amount that is a length of a part of a symbol to be circulated in the symbol of the relay signal to reduce a temporal overlap of delay characteristics of a communication path to
The cyclic shift delay means includes
The radio communication system according to claim 1, wherein the symbol of the relay signal is cyclically shifted based on the cyclic shift amount calculated by the cyclic shift delay amount control means. The relay wireless device and the incoming wireless device are:
The radio communication system according to claim 1, wherein modulation and demodulation are performed by orthogonal frequency division multiplexing on radio signals to be transmitted and received. The relay wireless device and the incoming wireless device are:
The radio communication system according to claim 1 or 2, wherein modulation and demodulation are performed by single carrier block transmission with a cyclic prefix added to radio signals to be transmitted and received. The calling-side communication device and the relay wireless device perform wireless communication,
The originating communication device, the relay wireless device, and the terminating wireless device are:
5. The wireless communication system according to claim 1, comprising a plurality of antennas, and performing wireless communication by MIMO transmission using the plurality of antennas. The cyclic shift delay means includes
A part of the symbols of the relay signal having a length corresponding to a delay generated at the time of reception of the receiving-side radio apparatus for each of the plurality of antennas is cyclically shifted for each symbol of the relay signal, and is cyclically shifted. The wireless communication system according to claim 5, wherein a relay signal is transmitted to the terminating wireless device. The cyclic shift delay amount control means includes:
Detect delay profile information indicating a delay state of a communication path to the called radio device for each of the plurality of antennas of the relay radio device, and based on the detected delay profile information, the incoming call for each of the plurality of antennas Calculating the amount of cyclic shift, which is the length of a part of the symbol to be circulated in the symbol of the relay signal, reducing the temporal overlap of the delay characteristics of the communication path to the side wireless device,
The cyclic shift delay means includes
The radio communication system according to claim 6, wherein the symbol of the relay signal is cyclically shifted based on the cyclic shift amount for each of the plurality of antennas calculated by the cyclic shift delay amount control unit. A transmitting side communication device that transmits a signal, a plurality of relay wireless devices that relay signals transmitted from the transmitting side communication device and transmit them by radio signals, and an incoming side radio that receives radio signals from the relay radio devices A wireless relay system in a wireless communication system comprising:
Modulation means for generating a relay signal by modulating based on a signal received from the originating communication device;
A part of the symbol of the relay signal having a length corresponding to the delay of the relay signal between the self-relay radio device and another relay radio device generated at the time of reception of the incoming-side radio device is a symbol of the relay signal A cyclic shift delay means for cyclically shifting each time, and transmitting the cyclically shifted relay signal to the destination wireless device;
A relay radio apparatus comprising:

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