JP2010226676A - Radio repeater system and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication method for achieving highly-interchangeable relay transmission by using a signal format which is common to conventional specifications without newly defining a signal format for relay transmission with respect to a signal format when a relay station is not used. <P>SOLUTION: In this radio communication method in a radio repeater system 3 which relays the communication of information in the case of communicating information between first communication equipment 1 and second communication equipment 2, information is transmitted with a frame including a plurality of information bits, the frame is configured of a plurality of signal blocks, the leading section of each of the plurality of signal blocks includes a cyclic prefix as the same signal as the tail of the signal block, and the first signal block of the frame to be transmitted from the radio repeater system includes the cyclic prefix which is shorter than the cyclic prefix of the signal block which is not the first one. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless relay device and a wireless communication method.

  In the fourth generation cellular mobile communication system, it is necessary to realize a data communication speed of 1 Gbps or more at rest. Since the transmission bandwidth increases to 100 MHz and the carrier frequency shifts to the 5 GHz band, power consumption and propagation path loss increase. Increasing the transmission power to compensate for the propagation path loss leads to an increase in the temperature of the device and an increase in power consumption. Especially in mobile communication terminals that are portable terminals for human beings, it is difficult to implement due to terminal temperature and battery capacity limitations. is there. There is a method using a micro cell / pico cell in which the cell size is reduced and the propagation path loss is reduced, but there is a problem that the number of base stations is increased and the infrastructure cost is increased.

  As one method for solving such a problem, it is effective to use a relay station that relays (relays) a signal between the mobile communication terminal and the base station. In particular, an in-band relay in which communication between a base station and a mobile communication terminal and communication between a base station and a relay station coexist is effective because it is not necessary to prepare a new relay frequency.

  However, in the in-band relay, there is a problem of resource allocation between communication between the base station and the relay station (relay link) and communication between the relay station and the mobile communication terminal (access link). If this resource allocation is not successful, the relay link and the access link may interfere with each other, or resources that cannot be used effectively for communication may be generated.

  Patent Document 1 describes a method for adjusting a transmission / reception switching gap when a signal received by a relay station is transmitted to the next relay station or a receiving station as a transmission destination. In Patent Document 1, a method of transmitting and receiving only a part of an OFDM signal becomes a repetitive signal by setting subcarriers of OFDM (Orthogonal Frequency Division Multiplexing) in which data is arranged at a constant interval. It is shown.

JP 2007-166620 A

  However, since the method described in Patent Document 1 performs allocation so that only specific subcarriers are used in OFDM symbols before and after the transmission / reception switching gap, signal allocation change processing is required. There is a problem that the transmission speed is lowered.

  The present invention has been made in view of the above circumstances, and does not define a new signal format for relay transmission with respect to a signal format when a relay station is not used. It is an object of the present invention to provide a wireless relay device and a wireless communication method capable of realizing highly compatible relay transmission using the above.

  The present invention is a wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device, wherein the information includes a plurality of information Transmitted in a frame including bits, the frame is composed of a plurality of signal blocks, each of the plurality of signal blocks includes a cyclic prefix that is the same signal as the end of the signal block, The first signal block of the frame transmitted from the wireless relay device includes a cyclic prefix having a shorter length than a cyclic prefix of a non-first signal block.

  The present invention is a wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device, wherein the information includes a plurality of information Transmitted in a frame including bits, the frame is composed of a plurality of signal blocks, each of the plurality of signal blocks includes a cyclic prefix that is the same signal as the end of the signal block, When the wireless relay device receives the frame, the last signal block of the received frame is received at a reception timing earlier than the reception timing of the non-last signal block.

  The present invention is a wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device, wherein the information includes a plurality of information Transmitted in a frame including bits, the frame is composed of a plurality of signal blocks, each of the plurality of signal blocks includes a cyclic prefix that is the same signal as the end of the signal block, The first signal block of the frame transmitted from the radio relay apparatus includes a cyclic prefix with a length shorter than the cyclic prefix of the non-first signal block, and is received when the radio relay apparatus receives the frame. In the last signal block of the frame to be received, the reception timing earlier than the reception timing of the non-last signal block Characterized by receiving at grayed.

  In the present invention, when a propagation path delay between the first communication device and the wireless relay device is larger than a predetermined threshold, the wireless relay device starts the first frame to be transmitted to the first communication device. The signal block includes a cyclic prefix having a length shorter than the cyclic prefix of the non-first signal block. When receiving the frame from the first communication device, the last signal block of the received frame is the last. When the reception delay is earlier than the reception timing of the non-signal block, and the propagation path delay is equal to or less than a predetermined threshold, the wireless relay device transmits the first frame to be transmitted to the second communication device. The signal block contains a cyclic prefix that is shorter than the cyclic prefix of the non-first signal block , When receiving the frame from the second communication device, the last signal block of a frame to be received is characterized by receiving at an earlier reception timing from the reception timing of the last non signal block.

  The present invention is characterized in that the first communication device is a base station device and the second communication device is a mobile communication terminal.

  The present invention is characterized in that the signal block is an OFDM symbol to which a cyclic prefix is added.

  The present invention is characterized in that the signal block is obtained by adding a cyclic prefix to a blocked single carrier signal.

  The present invention is characterized in that the signal block is a DFT Spread-OFDM symbol to which a cyclic prefix is added.

  In the present invention, a signal block of a frame transmitted from the first communication apparatus to the second communication apparatus is an OFDM symbol to which a cyclic prefix is added, and the second communication apparatus to the first communication apparatus A signal block of a frame to be transmitted to is a DFT Spread-OFDM symbol to which a cyclic prefix is added.

  The present invention is transmitted in a frame including a plurality of information bits in order to communicate information between the first communication device and the second communication device, the frame is composed of a plurality of signal blocks, Each of the plurality of signal blocks is a wireless relay device that relays information including a cyclic prefix that is the same signal as the end of the signal block, and when transmitting the frame, Transmitting means for setting a cyclic prefix shorter in length than a cyclic prefix of a non-first signal block is provided in the first signal block of the frame.

  The present invention is transmitted in a frame including a plurality of information bits in order to communicate information between the first communication device and the second communication device, the frame is composed of a plurality of signal blocks, Each of the plurality of signal blocks is a wireless relay device that relays communication of information including a cyclic prefix that is the same signal as the end of the signal block, and is received when the frame is received. In the last signal block of the frame to be received, receiving means for receiving at a reception timing earlier than the reception timing of the non-last signal block is provided.

  The present invention is transmitted in a frame including a plurality of information bits in order to communicate information between the first communication device and the second communication device, the frame is composed of a plurality of signal blocks, Each of the plurality of signal blocks is a wireless relay device that relays information including a cyclic prefix that is the same signal as the end of the signal block, and when transmitting the frame, Transmission means for setting a cyclic prefix shorter in length than the cyclic prefix of the non-first signal block in the first signal block of the frame, and the last signal block in the last frame of the received frame when receiving the frame Receiving means for receiving at a reception timing earlier than the reception timing of the non-signal block. And butterflies.

  According to the present invention, without newly defining a signal format for relay transmission with respect to a signal format in the case of not using a relay station, the overhead for relay transmission is achieved using a signal format common to the conventional standard. As a result, it is possible to realize efficient relay transmission with high compatibility.

It is a block diagram which shows the structure of the radio | wireless communications system of one Embodiment of this invention. It is a block diagram which shows the detailed structure of the reception process part shown in FIG. It is a figure which shows the signal of the uplink in a relay station. It is a flowchart which shows the operation | movement of the cut-out process of a reception block. It is a block diagram which shows the detailed structure of the reception process part shown in FIG. It is a flowchart which shows the operation | movement of the reception block cut-out process in the case of using a cyclic shift. It is a block diagram which shows the detailed structure of the transmission process part shown in FIG. It is a figure which shows the signal of the downlink in a relay station. It is a flowchart which shows operation | movement of CP production | generation processing. It is a block diagram which shows the detailed structure of the reception process part shown in FIG. It is a block diagram which shows the detailed structure of the transmission process part shown in FIG. It is a block diagram which shows the detailed structure of the reception process part shown in FIG. It is a block diagram which shows the detailed structure of the transmission process part shown in FIG. It is a flowchart which shows the parameter setting operation | movement at the time of downlink. It is explanatory drawing which shows the timing regarding the parameter setting at the time of downlink. It is explanatory drawing which shows the timing regarding the parameter setting at the time of downlink. It is a flowchart which shows the parameter setting operation | movement at the time of uplink. It is explanatory drawing which shows the timing regarding the parameter setting at the time of uplink. It is explanatory drawing which shows the timing regarding the parameter setting at the time of uplink.

<First Embodiment>
A wireless communication relay device according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the wireless communication system of the embodiment. In this figure, reference numeral 1 denotes a mobile communication terminal used in a radio communication system. Reference numeral 2 denotes a base station apparatus (hereinafter referred to as a base station) that has a communication service area and establishes a wireless communication transmission path with the mobile communication terminal 1. Reference numeral 3 is a relay station that is arranged in the far end of the communication service area of the base station 2 or in a radio wave insensitive zone and has a specific communication service area for the purpose of expanding the communication service area of the base station 2 or improving communication quality. Device (hereinafter referred to as a relay station). When wireless communication is performed between the mobile communication terminal 1 and the base station 2, the communication service area of the base station 2 is expanded and the communication quality is improved by performing relay communication via the relay station 3. Reference numeral 4 denotes a core network to which the base station 2 is connected. A plurality of base stations 2 are connected to the core network 4 but are not shown in FIG. In addition, a plurality of relay stations 3 may be installed for the relay station 3 in order to expand the communication service area of one base station 2, but is omitted in FIG. FIG. 1 shows a so-called two-hop configuration in the case where there is one relay station 3, but there are a plurality of relay stations 3 between the mobile communication terminal 1 and the base station 2 and relay communication of three or more hops. A configuration for performing the above may be possible.

  Reference numeral 31 denotes a transmission / reception unit for the base station, which includes a reception processing unit 32 that performs reception processing on a signal transmitted from the base station 2 and a transmission processing unit 33 that performs transmission processing on the signal to the base station 2. Reference numeral 34 denotes a transmission / reception unit for a mobile communication terminal, which includes a transmission processing unit 35 that transmits a signal to the mobile communication terminal 1 and a reception processing unit 36 that receives and processes a signal transmitted from the mobile communication terminal 1. Constitute. Reference numeral 37 denotes a control unit that performs overall control of processing operations of the relay station 3.

  The control unit 37 controls processing operations of the base station transceiver unit 31 and the mobile communication terminal transceiver unit 34. Here, the control operation related to the cutout of the received signal and the control related to CP (Cyclic Prefix) generation. explain. The reception processing unit 36 shifts the cut-out section (reception window) of the reception signal, and the transmission processing unit 35 shortens the CP of the transmission signal. This is because the propagation distance between the relay station 3 and the mobile communication terminal 1 is shorter than the propagation distance between the base station 2 and the relay station 3, and even if the CP is shortened, the delayed wave exceeds the CP section and the next This is because the communication quality is hardly deteriorated by affecting the signal block. When applied to a relay system of 3 hops or more, the base station transceiver 31 may communicate with another relay station 3 located on the base station 2 side, and the mobile communication terminal transceiver 34 There is a possibility of communicating with another relay station 3 located on the mobile communication terminal 1 side. Also in this case, there is no change in the processing operation of the relay station 3 regarding the control related to the cut-out of the received signal and the CP generation.

  In describing the configurations of the mobile communication terminal 1, the base station 2, and the relay station 3 with reference to FIG. 1, the known functions and configurations that the mobile communication terminal 1, the base station 2, and the relay station 3 normally have are as follows. Unless otherwise directly related to the description of the present invention, the description and illustration of the configuration are omitted. 1 shows a configuration in which the transmission / reception unit 31 for the base station and the transmission / reception unit 34 for the mobile communication terminal are separated, but the transmission processing units 33 and 35 or the reception processing units 32 and 36 are moved to the base station. It is possible to adopt a configuration for sharing with a communication terminal, and the antenna may be shared by switching with a switch. Moreover, the transmission / reception part 31 for base stations and the transmission / reception part 34 for mobile station terminals can reduce the interference of a mutual signal by installing in the position which mutually separated. In order to obtain such an effect, each of the base station transceiver unit 31, the mobile station transceiver unit 34, and the control unit 37 is provided as a separate device, or the base station unit including the functions of the control unit and the mobile unit. These may be connected as a cable or a wireless line, for example, as a device divided into two units for a station.

  Next, the detailed configuration of the reception processing units 32 and 36 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the reception processing units 32 and 36 when the multiplexing method is OFDM. Since the reception processing units 32 and 36 have the same configuration, the configuration of the reception processing unit 36 will be described here. The signal cutout unit 361 cuts out a DFT processing block from the received signal. At this time, based on the control signal output from the control unit 37, the cutout position of the block is controlled by the timing signal output from the timing control unit 362.

  The DFT processing unit 363 performs DFT (Discrete Fourier Transform) processing on the signal cut out by the signal cutout unit 361 and converts the signal into a frequency domain signal. Since the pilot signal is embedded in the OFDM signal, the channel estimation unit 364 extracts the pilot signal from the signal subjected to the DFT processing in the DFT processing unit 363 and performs channel estimation. The configuration of the pilot signal and the channel estimation can be performed using a known technique. The demodulation processing unit 365 performs a demodulation process for obtaining a demodulation result equivalent to the case where the channel estimation value is cut out at the original timing by correcting the phase rotation. The decoding processing unit 366 performs error correction on the demodulated signal and performs decoding processing. The signal (data) received and processed by the reception processing unit 36 for the mobile communication terminal is sent to the transmission processing unit 33 for the base station, and a transmission signal is generated.

  Here, with reference to FIG. 3, control of the cutout position of the block will be described. The signal shown in FIG. 3 is an uplink signal, and a signal transmitted from the mobile communication terminal 1 to the base station 2 after the signal transmitted from the mobile communication terminal 1 is received and processed by the relay station 3 This is illustrated with timing. However, since processing at the relay station 3 generally has a processing delay, this does not mean that the received signal in FIG. 3 is immediately transmitted to the base station 2 at the next transmission timing. Further, since the relay station 3 demodulates the received signal once, performs decoding processing, and then performs encoding and modulation processing again, the encoding rate and modulation method of the received signal and transmission signal may differ.

  Here, transmission and reception are alternately performed for each frame. As shown in FIG. 3, one frame includes six signal blocks, and each signal block is an OFDM symbol to which a CP (Cyclic Prefix) is added. Except for the last signal block among the six received blocks, a reception window is set in accordance with the rear side of the signal block as in window # 1. On the other hand, in the last block of the received signal, the window is shifted forward by ΔT as in window # 6 so that it does not overlap with the transmission timing. At this time, the width of the window does not change. Since it is not necessary to receive the signal after the reception window, the reception processing is not performed even if there is an upstream signal in the dotted line portion. A method for determining ΔT will be described later.

Even if the reception window is shifted forward, if the maximum delay difference is smaller than (CP length−ΔT), the component of the previous signal block does not enter the reception window, so that no interference occurs between the blocks. However, since the phase of the signal after DFT changes, correction is required during demodulation. The signal components after DFT of the signal cut out at the reception window # 6 are X ₀ , X ₁ ,..., X _N−1, and the signal components obtained by DFT of the signal cut out at the original timing are Y ₀ , Y ₁ ,. _Let Y _N-1 . The subscripts X and Y indicate subcarriers. Further, k = ΔT / Ts. Here, Ts is a sample interval. At this time, the relationship between X and Y is as follows.

  That is, when the reception window is shifted, the phase estimation is corrected for the channel estimation value, so that a demodulation result equivalent to the case where the reception window is cut out at the original timing can be obtained.

  Next, the received block cutout processing operation will be described with reference to FIG. Based on the information from the control block, it is determined whether or not the block to be received is the last block of the frame (step S1). If it is the last block, the cut-out timing of the received block is shifted by ΔT, and the window # 6 The signal is cut out at the position (step S2). Further, the phase of the channel estimation value is converted (step S3), and reception processing is performed (step S4). If the block to be received is not the last block in the frame, the cutout timing is not shifted, and cutout is performed after the block as in window # 1.

  Next, with reference to FIG. 5 and FIG. 6, a description will be given of a processing operation for avoiding a phase change after DFT processing by cyclic shift of a received signal instead of performing phase correction of a channel estimation value. FIG. 5 shows a configuration in which the reception processing unit 36 shown in FIG. 2 is modified so as to perform processing to avoid phase change after DFT processing by cyclic shift of the received signal instead of performing phase correction of the channel estimation value. It is a block diagram. The configuration shown in FIG. 5 is different from the configuration shown in FIG. 2 in that a cyclic shift processing unit 367 is provided. FIG. 6 is a flowchart showing a processing operation in which the processing operation shown in FIG. 4 is modified so as to perform a process for avoiding a phase change after the DFT process by a cyclic shift of the received signal instead of performing the phase correction of the channel estimation value. It is. The processing operation shown in FIG. 6 differs from the processing operation shown in FIG. 4 in that cyclic shift processing (step S5) is performed instead of processing for converting the phase of the channel estimation value.

Assuming that the signals cut out by the reception window # 6 shown in FIG. 3 are Z ₀ , Z ₁ ,..., Z _N−1 , the cyclic shift processing unit 367 performs Z _k , Z _{k + 1} ,. , Z _N−1 , Z ₀ ,..., Z _k−1 and then performing DFT processing in the DFT processing unit 363 eliminates the need for phase correction of the channel estimation value. If the block to be received is the last block of the frame, the cyclic shift processing unit 367 performs cyclic shift processing on the signal cut out by the signal cutout unit 361 (step S5), and is not the last block. In this case, the cyclic shift process is not performed.

  Next, a detailed configuration of the transmission processing units 33 and 35 shown in FIG. 1 will be described with reference to FIG. FIG. 7 is a block diagram illustrating the configuration of the transmission processing units 33 and 35 when the multiplexing method is OFDM. Since the transmission processing units 33 and 35 have the same configuration, the configuration of the transmission processing unit 35 will be described here. The encoding processing unit 351 performs error correction encoding processing on the data output from the reception processing unit 32. Modulation processing section 352 performs subcarrier component modulation processing on the signal that has been subjected to error correction coding processing. The signal modulated in the modulation processing unit 352 is blocked for each DFT unit, and an IDFT (Inverse Discrete Fourier Transform) processing unit 353 converts the blocked signal into a time domain signal. Then, the CP generation unit 354 receives a control signal, performs a process of assigning the component at the rear of the signal block as a CP to the head of the block in accordance with the timing of the control signal, and outputs it as a transmission signal.

  Here, the CP generation control operation will be described with reference to FIG. In signal blocks other than the first signal block of the transmission signal of the frame, a specified CP length is copied from the rear part of the signal block and added to the head of the signal block as in CP # 2. In the first block of the transmission signal, a CP having a length shorter than the specified CP length is added to the head of the signal block so as not to overlap with the timing of the reception signal as in CP # 1.

Next, the processing operation of the CP generation unit 354 shown in FIG. 7 will be described with reference to FIG. It is determined whether or not the block to be transmitted is the first block of the frame (step S11). If the block is the first block, the shortened _{CP is} shortened with respect to the specified CP length (T _CP ). set length of _{(T CP} -.DELTA.T) as a CP length (step S12), the performs transmission processing (step S14). On the other hand, if it is not the first block, a prescribed CP length (T _CP ) is set as the CP length (step S13), and transmission processing is performed (step S14). As for the setting of the shortened CP length here, the control signal from the base station 2 may be received by the relay station 3, and the CP length may be set in the relay station 3 according to the control signal information.

<Second Embodiment>
Next, detailed configurations of the reception processing unit and the transmission processing unit according to the second embodiment will be described with reference to FIGS. FIG. 10 is a block diagram illustrating a configuration of the reception processing units 32 and 36 when frequency domain equalization (FDE) is used in single carrier transmission using CP. The configuration shown in FIG. 10 is different from the configuration shown in FIG. 2 in that an FDE processing unit 368 and an IDFT processing unit 369 are newly provided.

  The signal cutout unit 361 cuts out a DFT processing block from the received signal. At this time, the signal cutout unit 361 controls the block cutout position by the control signal from the timing control unit 362. The control of the block cutout position is the same as in the case of the OFDM signal described above. The DFT processing unit 363 converts the extracted signal into a frequency domain signal, and the FDE processing unit 368 equalizes the frequency domain signal. The channel estimation value output from the channel estimation unit 364 is used for frequency domain equalization, but when the reception window is shifted, correction corresponding to the phase rotation is performed to perform frequency domain equalization processing. Thereby, a signal equivalent to the case of cutting out at the original timing can be obtained. Further, the IDFT processing unit 369 converts the signal into a time domain signal, the demodulation processing unit 356 performs demodulation processing on the subcarrier modulation, and the decoding processing unit 366 performs error correction decoding processing.

  Instead of providing the cyclic shift processing unit 3 between the signal cutout unit 361 and the DFT processing unit 363 and performing phase correction of the channel estimation value, a phase change after the DFT processing is avoided by cyclic shift of the received signal. It may be.

  Next, the configuration of the transmission processing units 33 and 35 in the case of single carrier transmission using CP will be described with reference to FIG. Since the transmission processing units 33 and 35 have the same configuration, the configuration of the transmission processing unit 35 will be described here. The encoding processing unit 351 performs error correction encoding processing on the data output from the reception processing unit 32. Modulation processing section 352 performs subcarrier component modulation processing on the signal that has been subjected to error correction coding processing. Further, the CP generation unit 354 performs a process of assigning the rear component of the block as a CP to the head of the block. At this time, the CP generation unit 354 receives a control signal and controls CP generation based on the control signal. The CP generation control operation is the same as in the case of using the OFDM signal.

<Third Embodiment>
Next, detailed configurations of the reception processing unit and the transmission processing unit according to the third embodiment will be described with reference to FIGS. FIG. 12 is a block diagram showing the configuration of the reception processing units 32 and 36 when DFT Spread-OFDM is used. The signal cutout unit 361 cuts out a DFT processing block from the received signal. At this time, the signal cutout unit 361 controls the block cutout position by the control signal from the timing control unit 362. The control of the block cutout position is the same as in the case of the OFDM signal described above. The DFT processing unit 363 converts the extracted signal into a frequency domain signal, and the FDE processing unit 368 equalizes the frequency domain signal. The channel estimation value output from the channel estimation unit 364 is used for frequency domain equalization, but when the reception window is shifted, correction corresponding to the phase rotation is performed to perform frequency domain equalization processing. Thereby, a signal equivalent to the case of cutting out at the original timing can be obtained. Further, the IDFT processing unit 369 converts the signal into a time domain signal, the demodulation processing unit 365 performs demodulation processing on the subcarrier modulation, and the decoding processing unit 366 performs error correction decoding processing.

  Next, the configuration of the transmission processing units 33 and 35 in the case of DFT Spread-OFDM will be described with reference to FIG. Since the transmission processing units 33 and 35 have the same configuration, the configuration of the transmission processing unit 35 will be described here. The encoding processing unit 351 performs error correction encoding processing on the data output from the reception processing unit 32. Modulation processing section 352 performs subcarrier component modulation processing on the signal that has been subjected to error correction coding processing. The DFT processing unit 355 performs DFT processing on the modulated signal and converts it to the frequency domain. Subsequently, the subcarrier mapping processing unit 356 performs subcarrier allocation, and the IDFT processing unit converts it into the time domain by IDFT processing. Further, the CP generation unit 354 performs processing for assigning the rear component of the signal block as a CP to the head of the block. At this time, the CP generation unit 354 controls CP generation by a control signal. Control of CP generation is the same as when using an OFDM signal.

<Fourth Embodiment>
Next, a method for determining the shift amount of the reception window and the shortened CP length will be described. FIG. 14 is a flowchart showing an operation during downlink communication. First, the base station 2 measures the propagation path delay T1 between the base station and the relay station (step S21). Then, a value obtained by multiplying the specified cyclic prefix length T _CP by the maximum CP shortening rate k (kT _CP ) is compared with the measured T1 (step S22). The maximum CP shortening rate k is a coefficient for obtaining the maximum allowable amount when shortening the _CP . If k is 0.8 with respect to the CP length T _CP , the CP is 20% of the specified value at the shortest. It can be reduced to.

Result of the comparison, T1 is equal to or smaller than _{kT CP,} set the value of T1 to [Delta] T (step S23), and notifies the relay station 3 (step S24). The relay station 3 uses a method of shortening the _CP (T _CP −ΔT) in the first block of the frame (step S25). As shown in FIG. 15, the relay station 3 shortens the CP so that the timing of reception and transmission does not overlap as shown in FIG.

On the other hand, the result of the comparison, T1 is the larger than _{kT CP} sets the value of _{kT CP} to [Delta] T (step S26), and notifies the value of the value of [Delta] T and T1 to the relay station 3 (step S27). In this case, as shown in FIG. 16, both CP shortening and reception window shifting are performed. That is, the relay station 3 shortens the reception interval by a window shift of T1-ΔT, and shortens the transmission interval by shortening the CP of ΔT (step S28). By combining these two methods, the transmission signal and the reception signal are prevented from overlapping due to the propagation path delay of T1. At this time, the value of ΔT and the value of T1 are notified to the relay station 3, but by notifying the relay station 3 of the value of k in advance, only T1 is notified to the relay station 3, and ΔT The calculation may be performed by the relay station 3. Alternatively, the communication with the base station 2 may be reduced by measuring the T1 at the relay station 3.

Next, an operation during uplink communication will be described with reference to FIG. First, the base station 2 measures the propagation path delay T1 between the base station and the relay station (step S31). Then, the measured T1 is compared with a value obtained by multiplying the specified cyclic prefix length _TCP by the maximum CP shortening rate k (step S32).

Result of the comparison, T1 is equal to or smaller than _{kT CP,} set the value of T1 to [Delta] T (step S33), and notifies the relay station 3 (step S34). In the last block of the relay station 3 frames applying the method of the reception window shifts _{(T CP -ΔT) (step} S35). As shown in FIG. 18, the relay station 3 uses a reception window shift so that the reception and transmission timings do not overlap each other.

On the other hand, the result of the comparison, T1 is set the value of _{kT CP} to ΔT in larger than _{kT CP,} notifies the values of ΔT and T1 to the relay station 3 (step S37). In this case, as shown in FIG. 19, both processing for shortening the CP and shifting the reception window are performed. That is, the relay station 3 shortens the reception interval by a window shift of ΔT, and shortens the transmission interval by shortening the CP of T1−ΔT (step S38). By combining these two methods, the transmission signal and the reception signal are prevented from overlapping due to the propagation path delay of T1.

  Note that the value of ΔT can be controlled using different values for the uplink and the downlink, but by making the value common, processing such as setting of ΔT and notification to the relay station 3 and communication are performed. The amount can be reduced.

  The method shown in this embodiment is an example of a method for determining the shift amount of the reception window and the shortened CP length, and ΔT shown in Embodiments 1 to 3 is determined by the method of this embodiment. It is not intended to limit.

  In the above description, the measured value T1 of the delay amount is set to ΔT, but ΔT is preferably a discrete amount at the sampling cycle interval with respect to the continuous amount T1. That is, ΔT may be a value obtained by quantizing T1, or a representative value may be obtained by referring to a table. Further, since it is not preferable that ΔT fluctuates frequently, it is desirable that the average value of the delay amount is T1 and fixed within a certain time.

  In addition, another threshold value T0 is introduced, and control is performed such that CP shortening or reception window shift is applied when the propagation path delay is larger than T0, and is not applied when T0 or less. May be. This is effective, for example, when a guard interval is provided in advance between frames. When the propagation path delay is larger than T0, the above-described method may be applied with T1 being a value obtained by subtracting T0 from the propagation path delay.

  In the description of the first, second, and third embodiments, the transmission processing unit 35 controls the CP generation in the downlink and adjusts so that the transmission and reception timings do not overlap. The reception processing unit 32 may shift the reception window together with the processing unit 35 controlling the CP generation to adjust the downlink timing. Also, in the uplink, the reception processing unit 36 performs reception window shift processing to adjust the transmission and reception timing so that they do not overlap. However, the reception processing unit 36 shifts the reception window. The transmission processing unit 33 may control the CP generation to adjust the timing.

  Further, the method of relaying both the downlink and the uplink in the relay station 3 has been described. For example, in the downlink, the signal from the base station 2 is directly received by the mobile communication terminal 1, and only the uplink signal from the mobile communication terminal 1 is received. May be relayed by the relay station 3. By using such a relay method, it is possible to suppress battery consumption of the mobile communication terminal 1 by suppressing the transmission power of the mobile communication terminal 1. That is, when the transmission signal from the mobile communication terminal 1 is received by the relay station 3, the reception window is shifted at the last block of the frame, and it is possible to avoid duplication of timing with the transmission to the base station 2. is there. Alternatively, it is possible to control CP generation during transmission from the relay station 3 to the base station 2 to shorten the CP at the beginning of the frame, and avoid timing overlap with reception. Furthermore, reception window shift and CP generation control may be performed together.

  Cellular network relay stations must both transmit and receive on the downlink or uplink frequency. When time division multiplexing is adopted, it is possible to distinguish between a transmission period and a reception period. However, the current standard does not provide a guard period that is necessary for switching, so that a short time transmission and reception overlap. there is a possibility.

  In order to solve such a problem, in the case of a single carrier signal to which an OFDM signal and a CP (cyclic prefix) are added, if the maximum delay is shorter than the CP length, a signal extraction section (reception window) for performing DFT processing is provided. Taking advantage of the possibility of shifting, reception is terminated earlier than usual, and transmission is started later than usual by using a CP having a shorter length than usual during transmission. By using these methods at the relay station when shifting from reception to transmission, reception and reception of signals can be prevented from overlapping.

  As described above, the method of ending reception of a frame early by shifting the reception window in the last signal block of the frame in the present invention is OFDM, single carrier, DFT Spread for a signal block with a cyclic prefix. -Applicable to various signals such as OFDM. This is also applicable to Clustered DFT Spread-OFDM and Nx DFT Spread-OFDM that are being studied in LTE-Advanced. Also, the method of delaying the start of frame transmission by shortening the cyclic prefix in the first signal block of the frame can be applied to various signals as long as the signal block has a cyclic prefix, and Clustered DFT Spread-OFDM. And Nx DFT Spread-OFDM can be similarly applied.

  DESCRIPTION OF SYMBOLS 1 ... Mobile communication terminal, 2 ... Base station apparatus (base station), 3 ... Relay station apparatus (relay station), 31 ... Transmission / reception part for base stations, 32 ... Reception processing part, 33: Transmission processing unit, 34: Transmission / reception unit for mobile communication terminals, 35: Transmission processing unit, 36: Reception processing unit, 37: Control unit

Claims (12)

A wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device,
The information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. Each of the plurality of signal blocks has a sign that is the same signal as the end of the signal block. A wireless communication method, wherein a click prefix is included, and a first signal block of the frame transmitted from the wireless relay device includes a cyclic prefix having a shorter length than a cyclic prefix of a non-first signal block. A wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device,
The information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. Each of the plurality of signal blocks has a sign that is the same signal as the end of the signal block. A radio communication method characterized by including a click prefix and receiving the frame at the last signal block of the received frame at a reception timing earlier than the reception timing of the non-last signal block when the radio relay apparatus receives the frame. . A wireless communication method in a wireless relay device that relays communication of information when performing communication of information between a first communication device and a second communication device,
The information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. Each of the plurality of signal blocks has a sign that is the same signal as the end of the signal block. Includes a click prefix,
The first signal block of the frame transmitted from the wireless relay device includes a cyclic prefix with a length shorter than the cyclic prefix of the non-first signal block;
When receiving the frame in the wireless relay apparatus, the last signal block of the received frame is received at a reception timing earlier than the reception timing of a non-last signal block. When the propagation path delay between the first communication device and the wireless relay device is larger than a predetermined threshold, the wireless relay device uses the first signal block of the frame to be transmitted to the first communication device. Includes a cyclic prefix having a length shorter than the cyclic prefix of the non-first signal block, and when receiving the frame from the first communication device, the last signal block of the received frame is not the last signal block. Receive at a reception timing earlier than the reception timing,
When the propagation path delay is less than or equal to a predetermined threshold, the wireless relay device is shorter than the cyclic prefix of the first signal block in the first signal block of the frame transmitted to the second communication device. A cyclic prefix of a length is included, and when the frame is received from the second communication device, the last signal block of the received frame is received at a reception timing earlier than the reception timing of the non-last signal block. The wireless communication method according to claim 3, wherein:   The wireless communication method according to claim 1, wherein the first communication device is a base station device, and the second communication device is a mobile communication terminal.   5. The wireless communication method according to claim 1, wherein the signal block is an OFDM symbol to which a cyclic prefix is added.   5. The radio communication method according to claim 1, wherein the signal block is a block-formed single carrier signal added with a cyclic prefix.   5. The radio communication method according to claim 1, wherein the signal block is a DFT Spread-OFDM symbol to which a cyclic prefix is added.   The signal block of the frame transmitted from the first communication apparatus to the second communication apparatus is an OFDM symbol to which a cyclic prefix is added, and the frame transmitted from the second communication apparatus to the first communication apparatus. 5. The radio communication method according to claim 1, wherein the signal block is a DFT Spread-OFDM symbol to which a cyclic prefix is added. In order to communicate information between the first communication device and the second communication device, the information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. A wireless relay device that relays communication of information including a cyclic prefix that is the same signal as the end of the signal block at the head of each block,
A radio relay apparatus comprising: a transmission unit configured to set a cyclic prefix having a shorter length than a cyclic prefix of a non-first signal block in the first signal block of the frame when transmitting the frame. In order to communicate information between the first communication device and the second communication device, the information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. A wireless relay device that relays communication of information including a cyclic prefix that is the same signal as the end of the signal block at the head of each block,
A radio relay apparatus comprising: a receiving unit configured to receive a reception timing earlier than a reception timing of a non-last signal block in a last signal block of a received frame when receiving the frame. In order to communicate information between the first communication device and the second communication device, the information is transmitted in a frame including a plurality of information bits, and the frame is composed of a plurality of signal blocks. A wireless relay device that relays communication of information including a cyclic prefix that is the same signal as the end of the signal block at the head of each block,
Transmitting means for setting a cyclic prefix having a length shorter than the cyclic prefix of the non-first signal block in the first signal block of the frame when transmitting the frame;
A radio relay apparatus comprising: a receiving unit configured to receive a reception timing earlier than a reception timing of a non-last signal block in a last signal block of a received frame when receiving the frame.

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