JP2016146553A - Wireless communication system, base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless communication system in which signals are relayed for improving the reception performance, while reducing the resource for relaying the signals, and simplifying the processing in a relay station and a base station.SOLUTION: In a wireless communication system including a first wireless terminal 10A transmitting a first signal, a second wireless terminal 10B transmitting a second signal, a base station receiving the first signal and second signal, and a relay station for receiving the first signal and second signal, and transmitting a relay signal to the relay station, the base station allocates the same resource block as the resource block for transmitting the first signal and second signal, respectively, from the first wireless terminal 10A and second wireless terminal 10B to the relay station, and transmits the terminal-relay station allocation information indicating the allocated resource block to the first wireless terminal 10A and second wireless terminal 10B (S9). The relay station receives a signal synthesizing first signal and second signal, and transmits the received signal as a relay signal, without decoding, to the base station.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a radio communication system and a base station provided in the radio communication system.

  In order to improve reception performance, the first and second radio apparatuses not only transmit messages to the fourth radio apparatus, but also transmit to the third radio apparatus that is a radio relay apparatus. Is known (for example, Patent Document 1). The third wireless device generates another message based on the messages received from the first and second wireless devices, and transmits the generated message to the fourth wireless device.

  The third wireless device (hereinafter, relay station) will be described in more detail. The relay station decodes a message received from the first wireless device and also decodes a message received from the second wireless device. Then, the exclusive OR of both messages is calculated, and the calculation result is transmitted as a message to the fourth radio apparatus (hereinafter referred to as base station).

  When there is a signal that cannot be correctly decoded, the base station calculates a log likelihood ratio for the signal that cannot be correctly decoded. Then, the channel decoding process is repeated using this log likelihood ratio.

JP 2010-118910 A

  In Patent Document 1, since the relay station needs to decode messages received from the first wireless device and the second wireless device, the first wireless device and the second wireless device use different resources. The message is transmitted to the relay station. Therefore, there is a problem that a lot of resources are required for relaying.

  Further, since the relay station needs to decode the message and perform an exclusive OR operation, there is a problem that the operation processing is complicated. Further, the base station also needs to calculate the log likelihood ratio and repeats the channel decoding process, so that there is a problem that the calculation process is complicated.

  The present invention has been made on the basis of this circumstance, and the object of the present invention is to relay a signal in order to improve reception performance, and to reduce the resources for the relay, and to relay the signal. It is an object of the present invention to provide a radio communication system in which processing in a station and a base station is simplified, and a base station provided in the radio communication system.

  The above object is achieved by a combination of the features described in the independent claims, and the subclaims define further advantageous embodiments of the invention. Reference numerals in parentheses described in the claims indicate a correspondence relationship with specific means described in the embodiments described later as one aspect, and do not limit the technical scope of the present invention. .

  The invention relating to the communication system for achieving the above object includes a first wireless terminal (10A) that transmits a first signal as a radio wave, a second wireless terminal (10B) that transmits a second signal as a radio wave, and a first wireless terminal. A radio comprising a base station (30) that receives signals transmitted by the terminal and the second radio terminal, and a relay station (20) that receives the first signal and the second signal and transmits a relay signal to the base station. In the communication system, the first radio terminal and the second radio terminal transmit the first signal and the second signal to the relay station in the same period, and the relay station combines the first signal and the second signal. The base station transmits the received signal to the base station as a relay signal without decoding, and the base station subtracts a second signal from the relay signal received from the relay station, and a subtractor And the signal after calculating the first wireless terminal Characterized in that it comprises combining unit for combining the first signal et receives the (38).

  According to the present invention, the first radio terminal and the second radio terminal transmit the first signal and the second signal to the relay station in the same period. Therefore, the first signal and the second signal are combined and received by the relay station. The relay station transmits the received signal as a relay signal to the base station without decoding it. Therefore, the relay signal received by the base station is a signal obtained by combining the first signal and the second signal.

  When the second signal is subtracted from the relay signal in the subtracting unit, the first signal transmitted through the relay station is obtained. The combining unit combines the signal after the calculation by the subtracting unit and the first signal received from the first wireless terminal. The signals to be combined are different in the signal transmission path, but are both first signals. Therefore, by combining these signals, a first signal with improved S / N can be obtained. Therefore, the reception performance is improved as compared with only receiving the first signal from the first wireless terminal.

  Furthermore, in the present invention, the first radio terminal and the second radio terminal transmit the first signal and the second signal to the relay station in the same period, so that the resources for relay can be reduced.

  The relay station transmits the received signal as a relay signal to the base station without decoding. Therefore, in the relay station, the processing of the relay station is simplified as compared with the conventional technique in which the signals received from the two wireless terminals are decoded and the exclusive OR is calculated.

  In addition, the base station also calculates the likelihood of each received signal, and the processing becomes simpler than the conventional technique in which iterative decoding processing is performed.

  An invention relating to a base station for achieving the above object is that a first signal is received from a first radio terminal, a second signal is received from a second radio terminal, and the first radio terminal transmits to a relay station A base station that receives from the relay station a relay signal generated by the relay station from the first signal transmitted from the first wireless terminal and the second signal transmitted from the second wireless terminal to the relay station. A resource for transmitting a first signal to the relay station when the first radio terminal transmits a resource allocation request signal for requesting transmission and transmits a resource allocation request signal for requesting transmission of the second signal from the second radio terminal The same resource block is allocated to the block and the resource block in which the second radio terminal transmits the second signal to the relay station, and terminal-relay station allocation information indicating the allocated resource block is assigned to the first radio terminal and the second radio Characterized by comprising a first resource allocation section (31) to send to the end.

  According to the present invention, the first radio terminal and the second radio terminal that have received the terminal-relay station assignment information transmit the first signal and the second signal to the relay station in the same period. Therefore, resources for relay can be reduced.

1 is an overall configuration diagram of a wireless communication system 1 to which the present invention is applied. It is a figure which shows the structure of the transmission side with which radio | wireless terminal 10A, 10B of FIG. 1 is provided. It is a figure which shows the structure with which the relay station 20 of FIG. 1 is provided. It is a functional block diagram which shows the function with which the base station 30 of FIG. 1 is provided in order to determine allocation information. 5 is a flowchart for describing processing of first to third resource allocation units 31 to 33 illustrated in FIG. 4. It is a figure which shows the structure of the receiving side with which the base station 30 of FIG. 1 is provided. It is a flowchart which shows the process performed when the radio | wireless terminal 10 receives terminal-base station allocation information and terminal-relay station allocation information. It is a flowchart which shows the process performed after the relay station 20 receives relay station-base station allocation information. It is a flowchart which shows the process which the base station 30 performs after the process of FIG.

(overall structure)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. A radio communication system 1 shown in FIG. 1 includes a first radio terminal 10A, a second radio terminal 10B, a relay station 20, and a base station 30.

  The first wireless terminal 10A and the second wireless terminal 10B have the same configuration. When the two are not particularly distinguished, the wireless terminal 10 is simply used. The first radio terminal 10A is used in the first vehicle 2A, and the second radio terminal 10B is used in the second vehicle 2B. In the present embodiment, the first wireless terminal 10A and the second wireless terminal 10B transmit signals periodically (for example, 100 msec).

  The relay station 20 is a communication device that can transmit and receive signals to and from each other wirelessly with the first wireless terminal 10A, the second wireless terminal 10B, and the base station 30.

  The base station 30 is also a communication device that can transmit and receive signals to and from each other wirelessly with the first wireless terminal 10A, the second wireless terminal 10B, and the relay station 20. The base station 30 further communicates with another base station 30 (not shown) by wire or wireless.

  In the present embodiment, the radio terminal 10, the relay station 20, and the base station 30 use, as communication methods, an orthogonal frequency division multiple access (hereinafter referred to as OFDMA) method, an SC-FDMA (Single Carrier Frequency Division Multiple Access) method. A method in which the base station 30 performs communication by allocating resource blocks, such as an Access) method.

(Configuration of wireless terminal 10)
The radio terminal 10 has the configuration shown in FIG. 2 as the configuration on the transmission side. The configuration shown in FIG. 2 is configured by, for example, an IC or an LSI except for the antennas 16a and 18a.

  The message generation unit 11 generates a message to be transmitted. In the present embodiment, the message generator 11 periodically generates a message to be transmitted. In addition to generating a message to be transmitted, a resource allocation request signal is also generated.

  The resource allocation request signal is a signal that requests the base station 30 to allocate a resource block for transmitting the message. Therefore, the resource allocation request signal is also generated periodically. This resource allocation request signal includes the data amount of the message.

  The channel encoding unit 12 changes the message generated by the message generation unit 11 and the resource allocation request signal to a transmission code.

  The primary modulation unit 13 modulates the code generated by the channel coding unit 12 using a known primary modulation method such as QPSK or 16QAM.

  The secondary modulation unit 14 modulates the signal generated by the modulation by the primary modulation unit 13 using a known secondary modulation method such as OFDMA or SC-FDMA.

  Terminal-relay station allocation information is input to the signal arrangement unit 15. This terminal-relay station allocation information is information indicating a resource block allocated to transmit a message signal, which is a signal in which a message is encoded and modulated, to the relay station 20, and is transmitted from the base station 30. The The signal arrangement unit 15 arranges the message signal in the resource block indicated in the first resource block allocation information.

  The RF unit 16 performs DA conversion, waveform shaping, amplification, and the like on the message signal supplied from the signal placement unit 15 and transmits the signal as a radio wave from the antenna 16a.

  Terminal arrangement information is input to the signal arrangement unit 17. This terminal-base station allocation information is information indicating a resource block allocated for transmitting a message signal to the base station 30, and is transmitted from the base station 30. The signal arrangement unit 17 arranges the message signal in the resource block indicated in the terminal-base station allocation information. Further, the resource allocation request signal is arranged in a resource block obtained in advance.

  The RF unit 18 performs DA conversion, waveform shaping, amplification, and the like on the signal supplied from the signal placement unit 17 and transmits the signal as a radio wave from the antenna 18a.

  Hereinafter, the message signal transmitted from the RF unit 16 by the first radio terminal 10A is identified as the first signal Sa, and the message signal transmitted from the RF unit 16 by the second radio terminal 10B is identified as the second signal Sb.

  Further, the message signals transmitted from the two RF units 16 and 18 in the same wireless terminals 10A and 10B are the same signal although the resource blocks are different. Therefore, the signal transmitted from the RF unit 18 of the first radio terminal 10A is the first signal Sa, and the signal transmitted from the RF unit 18 of the second radio terminal 10B is the second signal Sb.

  Note that the signal placement unit 15 and the RF unit 16 that are configurations for transmitting signals to the relay station 20 and the signal placement unit 17 and the RF unit 18 that are configurations for transmitting signals to the base station 30 are different transmissions. Since the signal is transmitted first, this is a different function when considering the transmission destination. However, the hardware configuration may be the same. Therefore, it suffices to have one signal arrangement unit that functions as the signal arrangement units 15 and 17 and one RF unit that functions as the RF units 16 and 18.

(Configuration of relay station 20)
The relay station 20 has the configuration shown in FIG. The RF unit 22 performs amplification, AD conversion, waveform shaping, and the like on the radio wave received by the antenna 21 and outputs the result to the signal placement unit 23. When a signal is supplied from the signal amplifying unit 24, the supplied signal is subjected to DA conversion, waveform shaping, amplification, and the like, and transmitted as a radio wave from the antenna 21.

  Relay station-base station allocation information is input to the signal arrangement unit 23. The relay station-base station allocation information is information indicating a resource block allocated to the relay station 20 for transmitting a signal to the base station 30, and is transmitted from the base station 30. The signal arrangement unit 23 arranges the signal supplied from the RF unit 22 in the resource block indicated in the relay station-base station allocation information.

  The signal amplifying unit 24 amplifies the signal supplied from the signal arranging unit 23 so as to have a constant signal strength or with a constant amplification factor, and outputs the amplified signal to the RF unit 22. The signal supplied from the signal amplification unit 24 to the RF unit 22 is transmitted from the antenna 21 as a radio wave.

(Configuration of base station 30)
When receiving a resource allocation request signal from the radio terminal 10, the base station 30 transmits resource allocation information to the radio terminal 10, as is the case with known base stations that communicate by OFDMA or SC-FDMA. In the present embodiment, resource allocation information transmitted to the radio terminal 10 includes terminal-base station allocation information and terminal-relay station allocation information. The base station 30 also transmits relay station-base station allocation information to the relay station 20.

  In order to determine the allocation information, the base station 30 includes the configuration shown in FIG. 4, that is, the first resource allocation unit 31, the second resource allocation unit 32, and the third resource allocation unit 33.

  The second resource allocation unit 32 is used by the first radio terminal 10A to transmit the first signal Sa to the base station 30 based on the data amount of the message determined by the resource allocation request signal received from the first radio terminal 10A. Determine resource blocks. Further, the resource block used for the second radio terminal 10B to transmit the second signal Sba to the base station 30 is determined based on the data amount of the message determined by the resource allocation request signal received from the second radio terminal 10B. The resource block determination method will be described with reference to FIG.

  Further, the second resource allocation unit 32 transmits terminal-base station allocation information indicating the determined resource block to the first radio terminal 10A and the second radio terminal 10B from the RF unit 34 illustrated in FIG.

  Further, the second resource allocation unit 32 outputs the terminal-base station allocation information and the resource allocation request signal to the first resource allocation unit 31.

  The first resource allocation unit 31 is used for the first radio terminal 10A to transmit the first signal Sa to the relay station 20, and the second radio terminal 10B is used to transmit the second signal Sb to the relay station 20. Determine resource blocks. This resource block is determined based on the terminal-base station allocation information and the resource allocation request signal. The determination method will be described with reference to FIG.

  Further, the first resource allocation unit 31 transmits terminal-relay station allocation information indicating the determined resource block from the RF unit 34 to the first radio terminal 10A and the second radio terminal 10B. In addition, the first resource allocation unit 31 outputs a resource allocation request signal, terminal-relay station allocation information, and terminal-base station allocation information to the third resource allocation unit 33.

  The third resource allocation unit 33 uses the resource block used by the relay station 20 to transmit the relay signal Sr to the base station 30 based on the resource allocation request signal, the terminal-relay station allocation information, and the terminal-base station allocation information. decide. The determination method will be described with reference to FIG.

  Then, the third resource allocation unit 33 transmits relay station-base station allocation information indicating the determined resource block from the RF unit 34 to the relay station 20.

  FIG. 5 is a flowchart for explaining processing of the first to third resource assignment units 31 to 33 shown in FIG. Steps S1 to S6 are processes of the second resource allocation unit 32, steps S7 to S9 are processes of the first resource allocation unit 31, and steps S10 to S12 are processes of the third resource allocation unit 33.

  In step S1, a resource allocation request signal is received from the first radio terminal 10A. As described above, the first radio terminal 10A and the second radio terminal 10B periodically transmit the resource allocation request signal. When the first radio terminal 10A transmits a resource allocation request signal, the base station 30 receives the resource allocation request signal in step S1.

  Note that the second radio terminal 10B may transmit the resource allocation request signal before the first radio terminal 10A. However, the first radio terminal 10A and the second radio terminal 10B have the same configuration. Therefore, the process of step S1 is performed with the side that has received the resource allocation request signal first as the first wireless terminal 10A.

  In step S2, resource blocks that can be transmitted by the first signal Sa are determined based on the amount of data included in the resource allocation request signal. Then, terminal-base station allocation information indicating the determined resource block is transmitted to the first radio terminal 10A.

  In step S3, a resource allocation request signal is received from the second radio terminal 10B. Since the second radio terminal 10B also periodically transmits the resource allocation request signal, the resource allocation request signal is transmitted from the second radio terminal 10B after step S1 until the transmission period of the resource allocation request signal elapses. Will be received.

  In the subsequent step S4, an empty resource block capable of transmitting the second signal Sb to the first radio terminal 10A in the same time slot as the resource block allocated to transmit the first signal Sa to the base station 30. Judge whether there is. This is to transmit the second signal Sb to the base station 30 as soon as possible, that is, to reduce the delay. If this determination is YES, the process proceeds to step S6, and if NO, the process proceeds to step S5.

  In step S5, a free resource block capable of transmitting the second signal Sb in the time slot next to the time slot determined immediately before whether or not there is a free resource block capable of transmitting the second signal Sb. Judge whether there is.

  When the first step S5 is executed, the time slot determined immediately before is a time slot in which a resource block allocated for transmitting the first signal Sa to the base station 30 is present. Therefore, in the first execution of step S5, free resources that can transmit the second signal Sb in the time slot next to the time slot in which the resource block allocated for transmitting the first signal Sa to the base station 30 is present. Determine if there are any blocks. If the determination in step S5 is YES, the process proceeds to step S6, and if NO, step S5 is repeated.

  In step S <b> 6, the resource block determined to be free in step S <b> 4 or step S <b> 5 is determined as a resource block in which the second radio terminal 10 </ b> B transmits the second signal Sb to the base station 30. The resource block in which the second radio terminal 10B transmits the second signal Sb to the base station 30 is the most time slot in which there is a resource block allocated by the first radio terminal 10A to transmit the first signal Sa to the base station 30. Assigned to be close. And the terminal-base station allocation information which instruct | indicates the determined resource block is transmitted to the 2nd radio | wireless terminal 10B.

  In step S7, the first signal Sa and the second signal Sb can be transmitted to the relay station 20 using the same resource block in the same time slot as the resource block allocated to transmit the second signal Sb to the base station 30. Determine whether the resource block is free. This is because the first signal Sa and the second signal Sb are transmitted to the relay station 20 as soon as possible. If this determination is YES, the process proceeds to step S9, and if NO, the process proceeds to step S8.

  In step S8, the first signal Sa and the second signal are transmitted in the time slot next to the time slot in which it is determined whether or not there is an empty resource block that can transmit the first signal Sa and the second signal Sb immediately before. It is determined whether there is an empty resource block that can transmit Sb.

  When the first step S8 is executed, the time slot determined immediately before is the time slot in which the resource block allocated for transmitting the second signal Sb to the base station 30 is present. Therefore, in the first step S8, the first signal Sa and the second signal Sb are transmitted to the relay station 20 in the time slot next to the time slot in which the resource block allocated for transmitting the second signal Sb to the base station 30 is present. It is determined whether there is a free resource block that can be transmitted. If the determination in step S8 is YES, the process proceeds to step S9, and if NO, step S8 is repeated.

  In step S9, the first radio terminal 10A and the second radio terminal 10B transmit the first signal Sa and the second signal Sb to the relay station 20 for the resource blocks determined to be free in step S7 or step S8, respectively. Decide which resource block to use. Then, terminal-relay station allocation information indicating the determined resource block is transmitted to the first radio terminal 10A and the second radio terminal 10B.

  When the first radio terminal 10A and the second radio terminal 10B transmit the first signal Sa and the second signal Sb to the relay station 20 according to the terminal-relay station assignment information, the relay station 20 transmits the first signal Sa and the second signal Sb. A signal obtained by combining the signal Sb is received. The relay station 20 transmits this signal as it is to the base station 30 as it is without decoding but performing signal amplification.

  The time slot in which the relay signal Sr can be transmitted to the base station 30 earliest is the time slot next to the time slot in which the resource block allocated for transmitting the first signal Sa and the second signal Sb to the relay station 20 is present. . Therefore, in step S10, the relay signal Sr is transmitted to the base station 30 in the time slot next to the time slot in which the resource block allocated for transmitting the first signal Sa and the second signal Sb to the relay station 20 is present. It is determined whether or not a resource block that can be used is free. If this determination is YES, the process proceeds to step S12, and if NO, the process proceeds to step S11.

  In step S11, there is an empty resource block that can transmit the relay signal Sr in the time slot immediately after the time slot for which it is determined whether or not there is an empty resource block that can transmit the relay signal Sr. Determine whether or not. If the determination in step S11 is YES, the process proceeds to step S12, and if NO, step S11 is repeated.

  In step S <b> 12, the resource block determined to be free in step S <b> 10 or step S <b> 11 is determined as a resource block in which the relay station 20 transmits the relay signal Sr to the base station 30. Then, relay station-base station allocation information indicating the determined resource block is transmitted to the relay station 20.

  The base station 30 has the configuration shown in FIG. 6 in addition to the configuration shown in FIG. Note that the configuration shown in FIG. 6 is only a configuration related to reception. Of course, the base station 30 also includes a configuration related to transmission, such as an encoding unit and a modulation unit. However, the configuration related to transmission is the same as that of a known base station except that resource allocation information is determined by the configuration shown in FIG.

  As shown in FIG. 6, the base station 30 includes an RF unit 34, a signal dividing unit 35, a subtracting unit 36, two equalizing units 37A and 37B, a maximum ratio combining unit 38, and a channel decoding unit 39.

  The RF unit 34 includes an antenna 34a, and amplifies and demodulates the radio wave received by the antenna 34a and outputs the amplified signal to the signal dividing unit 35.

  The signal dividing unit 35 extracts the signal in the resource block determined based on the terminal-base station allocation information and the relay station-base station allocation information from the signal input from the RF unit 34, thereby obtaining the first signal Sa and the first signal Sa. Two signals Sb and relay signal Sr are extracted.

  The extracted first signal Sa and second signal Sb are output to the equalization unit 37A. Further, the first signal Sa and the second signal Sb are also output to the subtracting unit 36. The relay signal Sr is also output to the subtracting unit 36.

  It should be noted that “Sa / Sb” is indicated above the arrow from the signal dividing unit 35 to the equalizing unit 37A, and conversely, “Sb / Sb” is indicated above the arrow from the signal dividing unit 35 to the subtracting unit 36. Sa ”. This is because when the equalizer 37A processes the first signal Sa, the equalizer 37B processes a signal obtained by subtracting the second signal Sb from the relay signal Sr. Conversely, when the equalizer 37A processes the second signal Sb, it indicates that the equalizer 37B processes a signal obtained by subtracting the first signal Sa from the relay signal Sr.

  The subtracting unit 36 subtracts the first signal Sa or the second signal Sb from the relay signal Sr. The relay signal Sr is a signal obtained by combining the first signal Sa and the second signal Sb. Therefore, when the first signal Sa is subtracted from the relay signal Sr, the second signal Sb transmitted via the relay station 20 is obtained, and when the second signal Sb is subtracted from the relay signal Sr, the relay is performed. A first signal Sa transmitted via the station 20 is obtained. The subtraction unit 36 outputs the first signal Sa and the second signal Sb transmitted through the relay station 20 to the equalization unit 37B.

  However, since there is a difference in transmission path, the first signal Sa and the second signal Sb input from the subtracting unit 36 to the equalizing unit 37B, and the first signal Sa and the second signal Sb input to the equalizing unit 37A. Are not exactly the same signal.

  The equalization unit 37A and the equalization unit 37B correspond to a first equalization unit and a second equalization unit, respectively. Each of these equalization units 37A and 37B performs an equalization process for correcting the signal distortion that has changed due to the transmission path. The equalization units 37A and 37B can perform various well-known equalization processes such as MMSE equalization and ZF equalization.

  The maximum ratio combining unit 38 combines the equalized first signals Sa output from the equalizing units 37A and 37B with their phases aligned. Further, the equalized second signals Sb output from the equalization units 37A and 37B are combined with each other in phase.

  The channel decoding unit 39 decodes the combined first signal Sa output from the maximum ratio combining unit 38 in accordance with a predetermined channel encoding method, and outputs a message generated by the first radio terminal 10A. . Further, the combined second signal Sb output from the maximum ratio combining unit 38 is decoded according to a predetermined channel encoding method, and a message generated by the second radio terminal 10B is output.

  FIG. 7 is a flowchart showing processing executed when the base station 30 performs the processing shown in FIG. 5 so that the radio terminal 10 receives the terminal-base station allocation information and the terminal-relay station allocation information. .

  Step S21 is a process performed by the message generation unit 11, and generates a message signal to be transmitted. Step S22 is a process performed by the channel encoder 12, and encodes the message signal generated in step S21. Step S23 is processing performed by the primary modulation unit 13, and the code generated in step S22 is modulated by a modulation scheme such as QPSK or 16QAM.

  Step S24 is a process performed by the secondary modulation unit 14, and the signal modulated in step S23 is further modulated by a predetermined method such as OFDMA or SC-FDMA.

  Step S25 is processing performed by the signal arrangement units 15 and 17, and the signal modulated in step S24 is converted into the resource block indicated in the terminal-base station allocation information and the resource block indicated in the terminal-relay station allocation information. Deploy.

  In step S26, the signal arranged in step S25 is output to the RF units 16 and 18. Thereby, a message signal is transmitted from the antenna.

  FIG. 8 is a flowchart showing processing executed by the relay station 20 after receiving relay station-base station allocation information from the base station 30.

  As described in step S9 of FIG. 5, the base station 30 has resource blocks for the first radio terminal 10A and the second radio terminal 10B to transmit the first signal Sa and the second signal Sb to the relay station 20, respectively. As the same resource block.

  In step S31, the RF unit 22 receives the first signal Sa and the second signal Sb transmitted by the first radio terminal 10A and the second radio terminal 10B in the same resource block.

  Step S32 is processing performed by the signal placement unit 23, and the signal received in step S31 is placed in the resource block indicated by the relay station-base station allocation information.

  Step S33 is processing performed by the signal amplifying unit 24, and amplifies the signal arranged in step S32. In step S34, the amplified signal is output to the RF unit 22. As a result, the relay signal is transmitted from the antenna 21.

  FIG. 9 is a flowchart illustrating a process executed by the base station 30 after the process of FIG. In step S41, the first signal Sa is acquired by extracting the resource block allocated to transmit the first signal Sa to the base station 30 from the signal output from the RF unit 34.

  In step S42, the first signal Sa acquired in step S41 is equalized by MMSE equalization, ZF equalization, or the like.

  In step S43, the resource block allocated for transmitting the second signal Sb to the base station 30 is extracted from the signal output from the RF unit 34, thereby obtaining the second signal Sb.

  In step S44, the relay signal Sr is acquired by taking out the resource block assigned to transmit the relay signal Sr to the base station 30 from the signal output from the RF unit 34.

  Step S45 is a process of the subtraction unit 36, and the second signal Sb acquired in step S43 is subtracted from the relay signal Sr acquired in step S44. Thereby, the first signal Sa transmitted through the relay station 20 is obtained.

  Step S46 is a process of the equalization unit 37B, and equalizes the signal obtained by the subtraction process of step S45.

  In step S47, the first signal Sa after the equalization process in step S42 and the signal after the equalization process in step S46 are combined in a maximum ratio.

  In step S48, the signal after the maximum ratio combining in step S47 is decoded according to a predetermined channel coding scheme. Thereby, the message transmitted by the first wireless terminal 10A is obtained (step S49).

  Note that the description of FIG. 9 is the process of acquiring the message transmitted by the first wireless terminal 10A, but the message transmitted by the second wireless terminal 10B can also be acquired by the same process.

  When acquiring the message which the 2nd radio | wireless terminal 10B transmitted, it replaces with 1st signal Sa and acquires 2nd signal Sb by step S41. Conversely, in step S43, the first signal Sa is obtained instead of the second signal Sb. In step S45, the equalized first signal Sa is subtracted from the relay signal Sr. In step S47, the equalized second signal Sb and the equalized signal Sr-Sa are combined at the maximum ratio. If the signal after the maximum ratio combining is decoded in step S48, a message from the second wireless terminal 10B can be acquired.

  In the present embodiment described above, the base station 30 uses the same resource block as the resource block in which the first radio terminal 10A and the second radio terminal 10B transmit the first signal Sa and the second signal Sb to the relay station 20. Allocation (first resource allocation unit 31, S9). Therefore, the first radio terminal 10A and the second radio terminal 10B transmit the first signal Sa and the second signal Sb to the relay station 20 in the same period, whereby the first signal Sa and the second signal Sb are Are combined and received by the relay station 20.

  The relay station 20 transmits the received signal as the relay signal Sr to the base station 30 without decoding it (S31 to S34). Therefore, the relay signal Sr received by the base station 30 is a signal obtained by combining the first signal Sa and the second signal Sb.

  When the second signal Sb is subtracted from the relay signal Sr by the subtracting unit 36, the first signal Sa transmitted via the relay station 20 is obtained. When the first signal Sa is subtracted from the relay signal Sr, the second signal Sb transmitted via the relay station 20 is obtained (S45).

  The maximum ratio combining unit 38 combines the first signal Sa transmitted via the relay station 20 and the first signal Sa transmitted directly to the base station 30 and transmits the combined signal via the relay station 20. The second signal Sb thus generated and the second signal Sb transmitted directly to the base station 30 are combined (S47). By this synthesis, the first signal Sa and the second signal Sb with improved S / N are obtained.

  Further, in the present embodiment, the first radio terminal 10A and the second radio terminal 10B transmit the first signal Sa and the second signal to the relay station 20 using the same resource block, so that resources for relay are allocated. Can be reduced.

  Further, the relay station 20 transmits the received signal to the base station 30 as the relay signal Sr without decoding. Therefore, in the relay station 20, the processing of the relay station 20 is simplified as compared with the conventional technique in which the signals received from the two wireless terminals 10A and 10B are decoded and the exclusive OR is calculated. In addition, the base station 30 also calculates the likelihood of each received signal, and the processing becomes simpler than the conventional technique that performs iterative decoding processing.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from a summary, it can implement variously.

1: wireless communication system 2A: first vehicle 2B: second vehicle 10: wireless terminal 10A: first wireless terminal 10B: second wireless terminal 11: message generator 12: channel encoder 13: primary modulator 14: second Next modulation unit 15: Signal arrangement unit 16: RF unit 16a: Antenna 17: Signal arrangement unit 18: RF unit 18a: Antenna 20: Relay station 21: Antenna 22: RF unit 23: Signal arrangement unit 24: Signal amplification unit 30: Base station 31: First resource allocation unit 32: Second resource allocation unit 33: Third resource allocation unit 34: RF unit 34a: Antenna 35: Signal division unit 36: Subtraction unit 37A: Equalization unit 37B: Equalization unit 38 : Maximum ratio combining unit 39: Channel decoding unit

Claims (7)

A first wireless terminal (10A) that transmits a first signal as a radio wave;
A second wireless terminal (10B) that transmits the second signal as a radio wave;
A base station (30) for receiving signals transmitted by the first wireless terminal and the second wireless terminal;
A wireless communication system comprising a relay station (20) for receiving the first signal and the second signal and transmitting a relay signal to the base station;
The first wireless terminal and the second wireless terminal transmit the first signal and the second signal to the relay station in the same period,
The relay station receives a signal obtained by combining the first signal and the second signal, and transmits the received signal to the base station as the relay signal without decoding the signal.
The base station
A subtractor (36) for subtracting the second signal from the relay signal received from the relay station;
A wireless communication system, comprising: a combining unit (38) that combines the signal after the subtraction unit calculates and the first signal received from the first wireless terminal. In claim 1,
When the first radio terminal needs to transmit the first signal, the first radio terminal transmits a resource allocation request signal to the base station,
When the second radio terminal needs to transmit the second signal, the second radio terminal transmits a resource allocation request signal to the base station,
When the base station receives the resource allocation request signal from both the first radio terminal and the second radio terminal, the first radio terminal transmits the first signal to the relay station; and The same resource block is allocated to the resource block in which the second radio terminal transmits the second signal to the relay station, and terminal-relay station allocation information indicating the allocated resource block is assigned to the first radio terminal and the second radio terminal. A first resource allocation unit (31) for transmitting to
The first wireless terminal transmits the first signal to the relay station according to the terminal-relay station assignment information received from the base station,
The wireless communication system, wherein the second wireless terminal transmits the second signal to the relay station according to the terminal-relay station assignment information received from the base station. In claim 1 or 2,
The base station
A first equalizer (37A) that receives the first signal and corrects the first signal to a signal in which transmission path distortion is corrected;
A second equalization unit (37B) that receives the signal calculated by the subtraction unit and corrects the input signal to a signal with corrected transmission line distortion;
The combining unit combines the signal in which the first signal is corrected by the first equalizing unit and the signal in which the signal calculated by the subtracting unit is corrected by the second equalizing unit. Wireless communication system. In claim 2,
The base station
When receiving the resource allocation request signal from the first radio terminal, the first radio terminal allocates a resource block for transmitting the first signal to the base station, and receives the resource from the second radio terminal. When the allocation request signal is received, the second radio terminal has the resource block allocated to transmit the first signal to the base station closest to a certain time slot. A resource block for transmitting the second signal to the base station is allocated, and a terminal-base station allocation information indicating the allocated resource block is transmitted to the first radio terminal and the second radio terminal. 32). A wireless communication system comprising: In claim 4,
The first resource allocation unit allocates the resource block indicated by the terminal-relay station allocation information so as to be closest to a time slot including the resource block indicated by the terminal-base station allocation information. A wireless communication system. In claim 5,
The relay station allocates a resource block for transmitting the relay signal to the base station so as to be closest to the time slot including the resource block indicated by the terminal-relay station allocation information. A wireless communication system, comprising: a third resource allocation unit (33) that transmits the relay station-base station allocation information shown to the relay station. Receiving a first signal from a first wireless terminal, receiving a second signal from a second wireless terminal; and
A relay signal generated by the relay station from the first signal transmitted from the first wireless terminal to the relay station and the second signal transmitted from the second wireless terminal to the relay station is received from the relay station. A base station that
When receiving a resource allocation request signal requesting transmission of the first signal from the first wireless terminal and receiving a resource allocation request signal requesting transmission of the second signal from the second wireless terminal, The same resource block is allocated and allocated to the resource block in which the first radio terminal transmits the first signal to the relay station and the resource block in which the second radio terminal transmits the second signal to the relay station. A base station comprising: a first resource allocation unit (31) that transmits terminal-relay station allocation information indicating a resource block to the first radio terminal and the second radio terminal.

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