JP2008104243A - Transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a control method for retransmission appropriately allocating retransmission data to a subcarrier excellent in line quality at all times, and capable of suppressing degradation in throughput. <P>SOLUTION: In the control method of retransmission, a mobile station measures quality in receiving line at every subcarrier or subcarrier group, and the measured quality is returned. Further, retransmission is required when an error is recognized in the received data. A base station required to be retransmitted transmits the retransmission data using the subcarrier other than the subcarrier or the subcarrier group determined as unused, on the basis of a predetermined information with respect to the line quality. The mobile station demodulates the retransmission data allocated to the subcarrier other than the subcarrier or the subcarrier group determined as unused. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retransmission control method that can be implemented in a communication system that employs a multicarrier modulation / demodulation method, and in particular, a retransmission control method and communication that can cope with a communication environment that may be affected by frequency selective fading. It relates to the device.

  Hereinafter, a conventional retransmission control method will be described. For example, an automatic repeat control method (ARQ: Automatic Repeat reQuest) is an important error control method in communication in an environment where code errors are likely to occur, such as mobile communication. ARQ is a technology that expects a time diversity effect that utilizes the fact that the propagation environment at a specific time is different from the propagation environment after a predetermined time has elapsed from the specific time.

  Also, as an example of ARQ, packet combining type HARQ (Hybrid ARQ) is known. In the packet combining type HARQ, when an error is detected, the received data is not discarded, but the soft decision information of the retransmission data and the previous received data is combined for each symbol without improving the received data. The code error rate is reduced.

  However, in the above ARQ, when the retransmission interval is shortened in order to increase the transmission efficiency, the signal power vs. noise power of the data received at the time of retransmission is affected by the same frequency selective fading at the time of retransmission even at the time of retransmission. The density may be almost the same as the initial delivery. In order to improve such problems, in mobile communication using multicarriers, in order to avoid frequency selective fading, data is allocated and transmitted to subcarriers excluding subcarriers with poor reception quality. Has been taken.

  Here, conventional multi-carrier mobile communication in which a retransmission control method is introduced will be described (for example, see Patent Document 1).

  FIG. 21 is a diagram showing a configuration of a conventional multicarrier mobile communication system 100. A multicarrier mobile communication system 100 includes a multicarrier transmission apparatus 110 that modulates and transmits a supplied information signal by an orthogonal frequency division multiplexing (OFDM), and a multicarrier reception apparatus that receives the signal. 120. For example, the multicarrier transmission apparatus 110 performs error correction coding on the input information signal, performs OFDM modulation, and radiates the modulated signal from the transmission antenna to the spatial transmission path. On the other hand, multicarrier receiving apparatus 120 receives a signal on a spatial transmission path via a receiving antenna, demodulates and decodes the received signal, and reproduces an information signal. Also, here, based on the carrier number information describing the carrier number in which the reception quality has deteriorated, the information signal is transmitted using a multicarrier with good reception quality.

  Next, the operation of each device will be described in detail. First, the input circuit 111 performs error correction coding on a signal such as a bit stream. The OFDM transmitter 112 modulates an information signal to be transmitted after error correction coding into an OFDM signal. Then, this signal is converted into a signal of a frequency band in the spatial transmission path, and further amplified to a predetermined transmission power. Thereafter, the amplified signal is radiated from the transmitting antenna to the spatial transmission path as an electromagnetic wave.

  On the other hand, the electromagnetic wave radiated to the spatial transmission path is input to the multicarrier receiving apparatus 120 via the receiving antenna, subjected to high frequency amplification processing, conversion processing to an intermediate frequency, intermediate frequency amplification processing, etc., and then received by OFDM. Input to the unit 121. The OFDM receiver 121 demodulates a signal modulated by the OFDM method. The output circuit 122 decodes the demodulated signal and notifies the malfunctioning carrier transmitting unit 123 of the subcarrier having a deteriorated reception quality. The malfunctioning carrier transmission unit 123 notifies the malfunctioning carrier reception unit 113 of the multicarrier transmission apparatus 110 of the notified subcarrier number with deteriorated reception quality via the spatial transmission path.

  The malfunctioning carrier receiving unit 113 notifies the input circuit 111 and the OFDM transmitting unit 112 of the notified subcarrier number so as not to use subcarriers with degraded reception quality during subsequent transmission and retransmission. Thereafter, multicarrier transmission apparatus 110 performs subsequent transmission processing and retransmission processing using only good carriers.

  As a result, in a conventional multicarrier mobile communication system, transmission processing is performed in a relatively stable state even on a transmission path where a C / N (Carrier to Noise ratio) of a specific carrier cannot be sufficiently obtained. Can do.

JP 2001-148682 A

  However, in the conventional multicarrier mobile communication system using the retransmission control method described above, the fluctuation cycle of frequency selective fading is short, and the propagation environment during transmission of initial transmission data and the propagation environment during transmission of retransmission data are different. If they are different, there is a problem that retransmission data cannot be appropriately allocated to subcarriers with good channel quality.

  In the multicarrier mobile communication, the frequency selective fading fluctuation period is short, the propagation environment at the initial transmission of the first transmission data is different from the propagation environment at the transmission of the retransmission data, and the time diversity effect by ARQ is sufficiently high. Even if it is obtained, there is a problem that the throughput is lowered due to a decrease in the number of subcarriers to which retransmission data can be assigned.

  In addition, the multicarrier mobile communication system has a problem in that the number of transmittable bits is reduced because the number of subcarriers assigned to retransmission data is reduced compared to the number of subcarriers assigned initial transmission data. It was.

  The present invention has been made in view of the above, and obtains a retransmission control method and a communication apparatus that can always appropriately allocate retransmission data to subcarriers with good channel quality and can suppress a decrease in throughput. For the purpose.

  In order to solve the above-described problems and achieve the object, in the retransmission control method according to the present invention, the receiving-side apparatus measures the received channel quality for each subcarrier or each subcarrier group, and And a retransmission request step for requesting retransmission when there is an error in received data, and a subcarrier that is determined not to be used by the transmitting side apparatus that has requested retransmission based on the predetermined information on the channel quality Alternatively, a transmission step of transmitting retransmission data using subcarriers other than the subcarrier group, and retransmission data allocated to subcarriers other than the subcarrier or subcarrier group determined to be unused by the receiving side device. And a demodulating step for demodulating.

  As described above, according to the invention of the first aspect (the present invention), the receiving-side apparatus notifies the transmitting-side apparatus of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and transmits For example, the side apparatus allocates retransmission data to subcarriers other than the subcarriers determined to have poor channel quality on the basis of fluctuations in channel quality for each subcarrier or each subcarrier group, and transmits to the receiving side. The apparatus demodulates the retransmission data allocated to subcarriers other than the subcarrier having poor channel quality. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, the ARQ time diversity effect can be obtained with subcarriers other than those with poor channel quality. In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect due to ARQ can be expected. Allocate and send data. As a result, the time diversity effect due to ARQ can be sufficiently obtained, and the reduction in throughput can be suppressed.

  Embodiments of a retransmission control method and a communication device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing the concept of subcarrier allocation processing in the retransmission control method according to the present invention. For example, when transmitting initial transmission data, the transmission side maps and transmits information data to all subcarriers (see FIG. 1A). On the other hand, on the receiving side, the received line quality such as SIR (Signal to Interference Ratio) for each subcarrier or each subcarrier group is measured using a common pilot channel or the like in which a known pattern is arranged, and the measurement result is obtained. Notify the sender. On the receiving side, when it is confirmed that an error has occurred in the received data by checking an error check code CRC (Cyclic Redundancy Code) or the like, a retransmission request signal is notified to the transmitting side. On the transmission side, when the retransmission request signal is received, the retransmission data is mapped and retransmitted using the subcarriers or subcarriers excluding the subcarrier group determined to have poor channel quality by a predetermined method (FIG. 1). (See (b)).

  FIG. 2 is a diagram illustrating a configuration of a base station (communication device) capable of executing the retransmission control method of the first embodiment. The base station includes an error correction coding unit 1, a data modulation unit 2, a frame generation unit 3, an S / P (Serial / Parallel) conversion unit 4, an interleaving unit 5, an IFFT (Inverse Fast Fourier Transform) unit 6, a GI (Guard) Interval) insertion unit 7, transmission RF (Radio Frequency) unit 8, reception RF unit 9, channel quality information detection unit 10, retransmission request information detection unit 11, format determination unit 12, and channel quality fluctuation measurement unit 13.

  Here, the retransmission control in the base station will be described. First, binary information data is input to the error correction encoding unit 1, and the error correction encoding unit 1 performs error correction encoding processing by, for example, turbo code, and sends the encoded data to the data modulation unit 2. Output.

  The data modulation unit 2 performs, for example, QPSK modulation on the received encoded data, and outputs the modulated data to the frame generation unit 3.

  The frame generation unit 3 receives the modulation data, pilot symbols, and control symbols such as format generation information output from the format determination unit 12, and the number of subcarriers (or the number of subcarrier groups) indicated by the format generation information. A frame signal corresponding to is generated, and the result is output to the S / P converter 4. FIG. 3 is a diagram illustrating an example of the frame signal generated by the frame generation unit 3.

  The S / P converter 4 performs serial / parallel conversion processing on the received frame signal based on the number of subcarriers indicated by the format generation information. Here, a frame signal associated with each sub-carrier constituting the OFDM modulated signal is generated, and the frame signal is output to interleaving section 5.

  The interleaving unit 5 rearranges the subcarriers corresponding to the frame signal based on the number of subcarriers indicated by the format generation information, and rearranges the rearranged frame to the IFFT unit 6. Output.

  The IFFT unit 6 performs IFFT processing on the rearranged frame signal based on the number of subcarriers indicated by the format generation information, and generates an OFDM (Orthogonal Frequency Division Multiplex) signal. At this time, the orthogonal frequency division multiplexed signal is output to the GI insertion unit 7.

  The GI insertion unit 7 adds a signal portion corresponding to the GI section at the end of the received orthogonal frequency division multiplexed signal to the head of the signal, and outputs the signal after the GI addition to the transmission RF unit 8.

  The transmission RF unit 8 converts the received signal into a signal in a frequency band on the spatial transmission path, further performs high frequency amplification to generate a signal having a predetermined transmission power, and transmits the amplified signal to the transmission antenna. To output. At this time, the output signal is radiated to the spatial transmission path as an electromagnetic wave.

  On the other hand, in the reception RF unit 9, the channel quality information for each subcarrier or each subcarrier group measured by the mobile station, and information indicating whether or not the information data has been correctly received by the mobile station (retransmission request information) Are received via a spatial transmission line and a receiving antenna. Then, high-frequency amplification processing, conversion to intermediate frequency, intermediate frequency amplification processing, and the like are performed, and further demodulation processing is performed. At the same time, the retransmission request information detector 11 is notified of the demodulated retransmission request information.

  The line quality information detection unit 10 performs threshold determination on the received line quality information for each subcarrier or each subcarrier group, and sets a subcarrier or subcarrier group below a predetermined line quality threshold to the line. The quality variation measuring unit 13 is notified.

  Based on the received retransmission request information, retransmission request information detection section 11 determines whether or not the information data has been correctly received at the mobile station, and shows information indicating whether or not to retransmit the information data as format determination section 12. And it notifies to a transmission information data buffer (not shown).

  The line quality variation measuring unit 13 stores the received line quality information for each subcarrier or each subcarrier group from the latest to the past a predetermined number of times, and the line quality is measured for each subcarrier or each subcarrier group. A quality variance value is measured to determine whether the variance value is below a predetermined threshold. If the subcarrier or subcarrier group that falls below the predetermined dispersion value threshold matches the subcarrier or subcarrier group that falls below the predetermined channel quality threshold, the effect of time diversity cannot be obtained. Therefore, it is notified to the format determination unit 12 as a subcarrier or a subcarrier group that does not use it (has poor channel quality). That is, subcarriers or subcarrier groups whose channel quality is below a predetermined threshold and whose variance value is small from the past history (the variation in channel quality is small) are not used. On the other hand, even if the channel quality falls below a predetermined threshold, time diversity is not used for subcarriers or subcarrier groups whose variance is large from the past history (the channel quality variation is large). Use because it is effective.

  The format determination unit 12 determines subsequent formats based on information indicating whether or not to retransmit the information data and information on the subcarriers or subcarrier groups not used. For example, when retransmitting information data, it is determined to use a format excluding subcarriers or subcarrier groups that are not used (poor channel quality). FIG. 4 is a diagram showing a format excluding subcarriers or subcarrier groups with poor channel quality. Then, format generation information for allocating retransmission data to subcarriers other than subcarriers in which the channel quality is in a poor state over a certain period is represented by error correction encoding unit 1, data modulation unit 2, frame generation unit 3, S / Notify P conversion unit 4, interleaving unit 5 and IFFT unit 6. On the other hand, if the information data is not retransmitted or if the subcarrier or subcarrier group that is not used is not notified even if the information data is retransmitted, the format using all subcarriers should be used. decide. Then, format generation information for allocating information data to all subcarriers is notified to the error correction encoding unit 1, the data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, the interleaving unit 5, and the IFFT unit 6. To do.

  FIG. 5 is a diagram showing a configuration of a mobile station (communication device) capable of executing the retransmission control method of the first embodiment. The mobile station includes a reception RF unit 20, a GI removal unit 21, an FFT (Fast Fourier Transform) unit 22, a deinterleave unit 23, a P / S (Parallel / Serial) conversion unit 24, a frame division unit 25, a data demodulation unit 26, An error correction decoding unit 27, a format information detection unit 28, a channel quality estimation unit 29, a retransmission request determination unit 30, and a transmission RF unit 31 are included.

  Here, retransmission control in the mobile station will be described. The reception RF unit 20 receives the electromagnetic wave addressed to the local station radiated to the spatial transmission path via the reception antenna. Then, the orthogonal frequency division multiplexed signal that has been subjected to the high frequency amplification process, the frequency conversion process to the intermediate frequency, the intermediate frequency amplification process, and the like is output to the GI removal unit 21.

  The GI removal unit 21 removes a signal portion corresponding to the GI section at the head of the received orthogonal frequency division multiplexed signal, and outputs the signal after the GI removal to the FFT unit 22.

  The FFT unit 22 performs an FFT calculation process on the received signal after GI removal, obtains the frequency component of each subcarrier, and outputs the result to the deinterleaving unit 23 and the channel quality estimation unit 29.

  The deinterleaving unit 23 performs a process reverse to the process performed by the interleaving unit 5 described above. That is, based on the format information output from the format information detection unit 28, the order of the subcarriers corresponding to the rearranged and transmitted frame signal is rearranged to the first arrangement. Then, the rearranged data is output to the P / S converter 24.

  The P / S conversion unit 24 performs parallel / serial conversion processing on the received data based on the format information, and outputs the result to the frame division unit 25 as a frame signal.

  The frame division unit 25 divides the received frame signal into control data including modulation data and format information based on the format information, notifies the modulation data to the data demodulation unit 26, and formats the control data. The information detection unit 28 is notified.

  The data demodulator 26 demodulates the received modulated data based on the format information and outputs the demodulated data to the error correction decoder 27.

  The format information detection unit 28 extracts information (format information) necessary for the deinterleaving process, P / S conversion process, frame division process, data demodulation process and error correction decoding process from the received control data. The extraction result is notified to the deinterleaving unit 23, the P / S conversion unit 24, the frame division unit 25, the data demodulation unit 26, and the error correction decoding unit 27.

  Based on the format information, the error correction decoding unit 27 performs error data detection processing and error correction processing on the received demodulated data, and the result is a baseband control unit inside the mobile station (not shown) as information data. Output for. At the same time, the retransmission request determination unit 30 is notified of the error data inspection result as error inspection data.

  Based on the received error check data, retransmission request determination section 30 notifies transmission RF section 31 of a signal indicating whether retransmission of information data is necessary or not as retransmission request information.

  The channel quality estimation unit 29 receives the frequency components of the pilot symbol subcarriers output from the FFT unit 22, estimates the received channel quality such as SIR for each subcarrier or each subcarrier group, and uses the result as channel quality information. To the transmission RF unit 31.

  The transmission RF unit 31 converts the received channel quality information and retransmission request information for each subcarrier or each subcarrier group into a signal in a frequency band on the spatial transmission path, and generates a signal having a predetermined transmission power. A high frequency amplification is performed, and the amplified signal is output via a transmission antenna. This output signal is radiated to the spatial transmission path as an electromagnetic wave.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. Based on the fluctuations in the channel quality, the retransmission data is allocated and transmitted to subcarriers other than the subcarriers determined to have poor channel quality, and the mobile station sends subcarriers other than the subcarriers with poor channel quality. Demodulate the allocated retransmission data. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, the time diversity effect of ARQ can be obtained with subcarriers other than the subcarrier with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect due to ARQ can be expected. Allocate and send data. Thereby, the time diversity effect by ARQ can fully be acquired, and the fall of a throughput can be suppressed.

  The retransmission control method according to the present embodiment uses a downlink from the base station to the mobile station and an uplink from the mobile station to the base station as a method for realizing simultaneous bidirectional communication (duplex communication). A case is assumed in which frequency division duplex transmission (FDD) for frequency separation is employed. Therefore, the channel quality for each subcarrier or each subcarrier group in the downlink is estimated by the mobile station and notified to the base station in the uplink. However, the method for realizing simultaneous bidirectional communication (duplex communication) is not limited to this. For example, time division duplex transmission (TDD) that separates the downlink and the uplink at the same frequency is performed. ) May be adopted. In this case, since it can be considered that the uplink and downlink channel quality fluctuations are the same, the mobile station notifies the base station of the channel quality for each subcarrier or subcarrier group in the downlink. There is no need. That is, in TDD, channel quality for each subcarrier or each subcarrier group in the uplink is estimated by the base station, and a subcarrier or subcarrier group that is not used at the time of retransmission is determined based on the fluctuation.

  Further, in the retransmission control method according to the present embodiment, the base station determines a threshold value for channel quality for each subcarrier or each subcarrier group estimated by the mobile station, and fluctuations in channel quality, and uses them during retransmission. Although the subcarriers that are not to be determined are determined, the determination process and the determination process are not limited to the base station, and may be performed by the mobile station. In this case, the mobile station performs threshold determination on channel quality and channel quality fluctuation, determines a subcarrier number or subcarrier group number that is not used during retransmission, and notifies the base station of the number.

  In addition, in the retransmission control method of the present embodiment, subcarriers to be excluded are determined by determining whether or not the channel quality is poor based on channel quality fluctuations for each subcarrier or each subcarrier group. However, the subcarriers to be excluded may be determined based on the number of subcarriers or the number of subcarrier groups with poor line quality. For example, even when the channel quality of a specific subcarrier is poor, a sufficient error correction effect can be obtained in a propagation environment where the BER of the entire subcarrier is small.

  Further, in the retransmission control method of the present embodiment, a subcarrier or subcarrier group in which the channel quality is poor over a certain period is determined based on the variance value. A poor subcarrier or subcarrier group may be determined based on a value averaged over a certain period.

Embodiment 2. FIG.
FIG. 6 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the second embodiment. In the present embodiment, a transmission request number counter unit 14 is added to the base station of the first embodiment. In addition, about the structure similar to Embodiment 1 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the first embodiment will be described.

  The retransmission request number counter unit 14 receives information indicating whether or not to retransmit the information data output from the retransmission request information detection unit 11. For example, if the received information indicates that retransmission is to be performed, the retransmission request number counter is incremented by “1”, and if it indicates that retransmission is not performed, the retransmission request number counter is reset to “0”. To do. At this time, the retransmission request number counter counts up to the maximum number of retransmission requests determined in advance by the system, and is reset to “0” again when the maximum number of retransmission requests is reached. The format determination unit 12 is notified of the value of the retransmission request counter.

  The format determination unit 12 determines the subsequent format based on the value of the retransmission request number counter and information on the unused subcarriers or subcarrier groups received from the channel quality variation measurement unit 13. For example, the number of subcarriers or subcarrier groups that are not used is determined based on the number of retransmission requests, and it is determined that a format using subcarriers excluding that number of subcarriers or subcarrier groups is used. Then, format generation information for allocating retransmission data only to subcarriers excluding subcarriers determined to have poor channel quality is represented by error correction encoding unit 1, data modulation unit 2, frame generation unit 3, S / P converter 4, interleave unit 5 and IFFT unit 6 are notified. On the other hand, when the value of the retransmission request number counter is “0”, or when the value of the retransmission request number counter is not “0”, a subcarrier or a subcarrier group that is not used is not notified, A format using all subcarriers is used. Then, format generation information for allocating information data to all subcarriers is notified to the error correction encoding unit 1, the data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, the interleaving unit 5, and the IFFT unit 6. To do.

FIG. 7 is a diagram illustrating a specific retransmission control method according to the second embodiment. Specifically, the format determination unit 12 determines the number of subcarriers or subcarrier groups that are not used based on the number of retransmission requests. The procedure to do is shown. Here, the maximum number of retransmission requests specified by the system is Nmax = 5, the number of retransmission requests notified by the retransmission request number counter unit 14 is N, and the number of defective subcarriers notified from the channel quality variation measuring unit 13 Is determined as Nng, and the number of unused subcarriers determined by the format determination unit 12 according to the number of retransmission requests is determined as Unused using the following equation (1).
Unused = Nng / (2 ^ (Nmax-N)) (1)

  That is, in this embodiment, not all subcarriers with poor channel quality are used, but the number of subcarriers that are not used in subcarriers with poor channel quality is increased as the number of retransmission requests increases. Go. The subcarriers that are not used are selected based on the average value and variance value of the channel quality, as in the first embodiment.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. The number of subcarriers that are not used and the number of subcarriers that are not used are determined from the subcarriers that are determined to have poor channel quality based on the fluctuation in channel quality and the number of retransmission requests, and are retransmitted to subcarriers that are not used. Data is allocated and transmitted, and the mobile station demodulates retransmission data allocated to subcarriers other than the subcarriers determined not to be used. That is, the base station uses all subcarriers at the initial transmission of data, and increases the ratio of the number of subcarriers that are not used as the number of data retransmissions increases. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, the time diversity effect of ARQ can be obtained with subcarriers other than the subcarrier with degraded channel quality.

  In addition, until the maximum number of retransmission requests specified in the system is reached, the ratio of the number of subcarriers that are not used is increased as the number of retransmission requests increases. Therefore, when the number of retransmission requests is small, time diversity by ARQ is performed. The effect and the coding gain by HARQ can be sufficiently obtained, and a decrease in throughput can be suppressed.

Embodiment 3 FIG.
Next, a retransmission control method according to the third embodiment will be described. Here, only operations different from those in the first or second embodiment will be described.

  FIG. 8 is a diagram illustrating the basic operation principle of HARQ. HARQ improves the SIR and improves the code error of the received signal by combining the retransmission data and the soft decision information of the previous received data for each symbol without discarding the erroneous received data detected on the receiving side. This is retransmission control that reduces the rate.

  Here, a specific example of representative HARQ will be described. First, in Type I HARQ, the information bit sequence to be transmitted is subjected to error correction coding processing at the same coding rate R for initial transmission data and retransmission data, and the reception side discards erroneous received data. Rather, the retransmission data and the soft decision information of the received data up to the previous time are synthesized for each symbol.

  Next, in Type III HARQ, after performing error correction coding processing at a coding rate R ′ on an information bit sequence to be transmitted, punctured coding is performed based on an erasure rule that differs depending on the number of transmissions. Then, the initial transmission data and the retransmission data stored in the reception buffer are code-combined to decode at the coding rate R ′ before thinning. As a result, in addition to the time diversity effect, the reception characteristics are improved by improving the coding gain.

  Next, in Type II HARQ, an error correction coding process is performed on an information bit sequence to be transmitted at a coding rate R ′, and then punctured coding is performed based on an erasure rule that varies depending on the number of transmissions. In this case, only the parity bit sequence is transmitted without including the information bit sequence, and the reception side code-combines the initial transmission data and the retransmission data stored in the reception buffer so that the coding rate R before thinning is performed. Decrypt with '. As a result, in addition to the time diversity effect, the reception characteristics are improved by improving the coding gain.

  FIG. 9 is a diagram illustrating a configuration of a base station that can execute the retransmission control method according to the third embodiment. In the present embodiment, the HARQ system selection unit 15a is provided in the format determination unit 12a. Further, the error correction encoding unit 1a of the present embodiment is configured by a turbo encoder described later. In addition, about the structure similar to Embodiment 1 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the first embodiment will be described.

  In the HARQ scheme selection unit 15a of the format determination unit 12a, when it is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the line quality variation measurement unit 13 Is determined to transmit retransmission data with a HARQ type different from that of initial transmission data, based on information on subcarriers or subcarrier groups that are not used. Then, the new HARQ type is notified to the format determination unit 12a. For example, a Type III HARQ in which an information bit sequence and a parity bit sequence are multiplexed is used at the time of initial transmission data transmission, and a Type II HARQ in which only a parity bit sequence is transmitted at the time of retransmission data transmission. In FIG. 8, Type II HARQ retransmission data has the same coding rate as Type III HARQ retransmission data, but the data length is halved since the information bit sequence is removed. That is, the number of subcarriers to which retransmission data is allocated is also halved.

  For example, when adopting Type II HARQ or Type III HARQ, the same HARQ type is used for the initial transmission data and the retransmission data, and the retransmission data is higher than the punctured coding rate in the initial transmission data. The punctured coding rate may be lowered. That is, in a turbo encoder described later (corresponding to a thinning / multiplexing unit 53 described later), the number of thinning out at the time of retransmission is increased from that at the initial transmission.

  In addition, when the format determination unit 12a is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13 are used. Based on the information on the carrier or the subcarrier group, it is determined to use a format using a subcarrier not used or a subcarrier other than the subcarrier group. Further, it is determined to use a HARQ type different from that at the initial transmission. Then, format generation information for allocating retransmission data to subcarriers other than subcarriers with poor channel quality using a HARQ type different from that at the time of initial transmission, error correction encoding unit 1a, data modulation unit 2, frame generation This is notified to the unit 3, the S / P conversion unit 4, the interleave unit 5 and the IFFT unit 6. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, format generation information for allocating information data to all subcarriers is notified to the error correction encoding unit 1a, the data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, the interleaving unit 5 and the IFFT unit 6. To do.

  FIG. 10 is a diagram illustrating a configuration of a mobile station capable of executing the retransmission control method according to the third embodiment. In the present embodiment, a reception information data buffer unit 32 is further provided in addition to the configuration of FIG. 5 of the first embodiment. Further, the error correction decoding unit 27a of the present embodiment is configured by a turbo decoder described later. In addition, about the structure similar to Embodiment 1 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the first embodiment will be described.

  The reception information data buffer unit 32 stores the soft decision information of the received demodulated data in association with the transmission order number. If the received demodulated data is retransmission data with reference to the transmission order number, etc., it corresponds to the same transmission order number as the retransmission data based on the HARQ type indicated by the format information from the format information detection unit 28a. The soft decision information of the received data up to the previous time is synthesized for each symbol, and the synthesis result is output to the error correction decoding unit 27a. If the received demodulated data is not retransmission data, the demodulated data is output to the error correction decoding unit 27a as it is. The stored soft decision information is deleted when the information data can be received correctly.

  The error correction decoding unit 27a decodes the correction signal algorithm of the error correction coding unit 1a based on the HARQ type indicated by the format information, and performs error data detection processing and error detection on the received demodulated data. A correction process is performed and information data is output. At the same time, the retransmission request determination unit 30 is notified of the error data inspection result as error inspection data.

  The format information detection unit 28a extracts information (format information) necessary for deinterleaving processing, P / S conversion processing, frame division processing, data demodulation processing, packet synthesis processing, and error correction decoding processing from the received control data. Then, the extraction result is notified to the deinterleaving unit 23, the P / S conversion unit 24, the frame division unit 25, the data demodulation unit 26, the reception information data buffer unit 32, and the error correction decoding unit 27a.

  FIG. 11 is a diagram showing a configuration of the error correction encoding unit 1a, that is, a turbo encoder. In this turbo encoder, first, an information bit sequence is input to the element encoder 50, and the element encoder 50 generates a parity bit sequence (1). The turbo interleaver 52 rearranges the information bit series and outputs the rearranged information bit series to the element encoder 51. The element encoder 51 generates a parity bit sequence (2).

  The decimation / multiplexing unit 53 performs decimation / multiplexing processing on the parity bit sequence (1) and the parity bit sequence (2). The multiplexer 54 further multiplexes the received multiplexed signal and the information bit sequence to generate a coded bit sequence. The decimation processing / multiplexing processing here refers to, for example, multiplexing while decimation of two input sequences so that a parity bit sequence (1) is output at an odd time point and a parity bit sequence (2) is output at an even time point. Indicates that There is also a method of performing only the multiplexing process without performing the thinning process.

  FIG. 12 is a diagram showing a configuration of the error correction decoding unit 27a, that is, a turbo decoder. In this turbo decoder, the element decoder 60 executes a decoding process using the encoded bit sequence and the prior value (1) that is reliability information notified from the element decoder 61, and increases the reliability. A certain external value (1) is output. The turbo interleaver 62 rearranges the external value (1) and notifies the result to the element decoder 61 as a prior value (2). The element decoder 61 executes decoding using the rearranged encoded sequence received from the turbo interleaver 62 and the prior value (2), and outputs an external value (2). The turbo deinterleaver 63 returns the external value (2) to the state before the rearrangement by the turbo interleaver 62, and notifies the element decoder 60 of the result as a prior value (1). Thereafter, iterative decoding is performed in the same procedure.

  Then, after repeating the above operation a predetermined number of times, the element decoder 61 outputs a final determination result by making a hard decision on the posterior value defined as the log posterior probability ratio.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, At the time of retransmission, a packet combination type different from that at the time of initial transmission is selected and transmitted, and the mobile station demodulates the retransmission data allocated to subcarriers other than the subcarrier having poor channel quality. That is, all subcarriers are used at the initial transmission of data, subcarriers other than the subcarriers determined to have poor channel quality are used at the time of data retransmission, and the packet combining type is changed. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  Further, in this embodiment, even when the number of subcarriers used at the time of retransmission is reduced compared to the time of initial transmission, a packet combination type different from that at the time of initial transmission can be selected at the time of retransmission. There is no shortage of the number of subcarriers to be allocated. As a result, the HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than those having poor channel quality.

  In the retransmission control method of the present embodiment, retransmission data is allocated to subcarriers other than subcarriers determined to have poor channel quality at the time of retransmission, according to channel quality variations for each subcarrier or subcarrier group, Whether or not to change the packet combining type is selected, but is not limited to this. For example, depending on the number of retransmission requests, subcarriers that are determined to be inferior in line quality are not used. The retransmission data may be assigned to subcarriers other than the subcarriers determined and not used, and whether or not to change the packet combining type may be selected.

Embodiment 4 FIG.
Next, a retransmission control method according to the fourth embodiment will be described. Here, only operations different from those in the first, second, or third embodiment will be described.

  FIG. 13 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the fourth embodiment. In the present embodiment, in addition to the configuration of FIG. 9 of the third embodiment, a transmission information data buffer unit 17 is further provided. Further, a retransmission data division determination unit 16b is provided in the format determination unit 12b. In addition, about the structure similar to Embodiment 1-3 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the third embodiment will be described.

  In the retransmission data division determination unit 16b of the format determination unit 12b, when it is notified that the information data is to be retransmitted, information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11, and the channel quality variation measurement unit 13 Whether to retransmit retransmission data is determined based on information on subcarriers or subcarrier groups that are not used. Then, it notifies the format determination unit 12b whether or not to divide the retransmission data. For example, when retransmission data is transmitted, if the number of unused subcarriers or subcarrier groups notified from the channel quality information detection unit 10 is half the total number of subcarriers, the format determination unit 12b divides the retransmission data into two. To decide.

  The transmission information data buffer unit 17 stores binary information data output to the error correction encoding unit 1a. Here, when it is notified from the retransmission request information detection unit 11 that the information data is retransmitted, the stored information data is extracted based on the transmission sequence number or the like. Further, the extracted information data is divided based on the number of divisions and the division size of the retransmission data indicated by the format generation information output from the format determination unit 12b, and the result is output as retransmission data. On the other hand, when the information data is not retransmitted, that is, when the information data is correctly received on the receiving side, the stored information data is deleted based on the transmission sequence number, etc., and new information data is output. .

  Further, when the format determination unit 12b is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13 are used. Based on the information on the carrier or the subcarrier group, it is determined to use the format using the subcarrier excluding the unused subcarrier or the subcarrier group. Further, the division size of retransmission data is determined. Then, format generation information for allocating retransmission data and next retransmission data only to subcarriers excluding the subcarriers determined to have poor channel quality, transmission information data buffer unit 17, error correction encoding unit 1a, The data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, the interleave unit 5 and the IFFT unit 6 are notified. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, format information for allocating information data to all subcarriers is transmitted to the transmission information data buffer unit 17, the error correction coding unit 1a, the data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, and the interleaving unit 5. And notify the IFFT unit 6.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, The division size of retransmission data is determined and transmitted, and the mobile station demodulates the divided retransmission data. That is, all the subcarriers are used for the initial transmission of data, and the retransmission data is divided and transmitted using a subcarrier other than the subcarrier that is determined to have poor channel quality when the data is retransmitted. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  Also, in this embodiment, even when the number of subcarriers used for retransmission is reduced compared to the time of initial transmission, retransmission data can be divided and transmitted. There is no shortage of numbers. Thereby, the time diversity effect of HARQ and a sufficient coding gain can be obtained by subcarriers excluding subcarriers having poor channel quality.

  In the retransmission control method of the present embodiment, retransmission data is transmitted to subcarriers other than the subcarriers determined to have poor channel quality at the time of retransmission according to the channel quality variation for each subcarrier or each subcarrier group. Allocation and whether or not to transmit retransmission data in a divided manner are selected, but this is not restrictive. For example, it is not used from subcarriers determined to have poor channel quality according to the number of retransmission requests. Subcarriers may be determined, retransmission data may be assigned to subcarriers other than the subcarriers determined not to be used, and whether to retransmit the retransmission data may be selected.

Embodiment 5. FIG.
Next, a retransmission control method according to the fifth embodiment will be described. Here, only operations different from those of the first, second, third, or fourth embodiments will be described.

  FIG. 14 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the fifth embodiment. In the present embodiment, in addition to the configuration of FIG. 9 of the third embodiment, an adaptive modulation unit 19 is further provided. In addition, an adaptive modulation scheme selection unit 18c is provided in the format determination unit 12c. In addition, about the structure similar to Embodiment 1-4 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the third embodiment will be described.

  In the adaptive modulation scheme selection unit 18c of the format determination unit 12c, when it is notified that the information data is to be retransmitted, information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11, and the channel quality variation measurement unit 13 Whether or not to change the data modulation scheme of retransmission data from the data modulation scheme in the initial transmission data is determined based on the information on the subcarriers or subcarrier groups that are not used. The format determining unit 12c is notified of the data modulation scheme of the retransmission data. For example, the number of bits that can be transmitted by one subcarrier is 2 bits when QPSK is used, and 4 bits that is twice when 16QAM is used. By using this, in the format determination unit 12c, when QPSK is used as the data modulation method of the initial transmission data, the number of subcarriers or subcarrier groups that are not used and are notified from the channel quality information detection unit 10 during retransmission data transmission If the number is half of the total number of subcarriers, it is decided to use 16QAM for the data modulation scheme of retransmission data.

  The adaptive modulation unit 19 performs modulation processing on the received encoded data using the modulation method notified from the format determination unit 12 c and outputs the modulation data to the frame generation unit 3.

  When the format determination unit 12c is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13 are used. Based on the information on the carrier or the subcarrier group, it is determined to use the format using the subcarrier excluding the unused subcarrier or the subcarrier group. In addition, a modulation scheme for retransmission data is determined. Then, format generation information for allocating retransmission data only to subcarriers excluding the subcarriers determined to have poor channel quality is converted into error correction encoding unit 1a, adaptive modulation unit 19, frame generation unit 3, S / Notify P conversion unit 4, interleaving unit 5 and IFFT unit 6. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, format generation information for allocating information data to all subcarriers is notified to the error correction encoding unit 1a, the adaptive modulation unit 19, the frame generation unit 3, the S / P conversion unit 4, the interleaving unit 5, and the IFFT unit 6. To do.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, The retransmission data modulation scheme is determined and transmitted, and the mobile station demodulates the retransmission data modulated by the new modulation scheme. That is, all subcarriers are used at the initial transmission of data, subcarriers other than the subcarriers determined to have poor channel quality are used at the time of data retransmission, and the modulation scheme of retransmission data is changed. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  In this embodiment, since the modulation scheme of retransmission data can be changed even when the number of subcarriers used at the time of retransmission is reduced compared to that at the time of initial transmission, There is no shortage of carriers. Thereby, the time diversity effect of HARQ and a sufficient coding gain can be obtained by subcarriers excluding subcarriers having poor channel quality.

  In the retransmission control method of the present embodiment, retransmission data is transmitted to subcarriers other than the subcarriers determined to have poor channel quality at the time of retransmission according to the channel quality variation for each subcarrier or each subcarrier group. Allocation and whether to change the modulation scheme of retransmission data are selected, but not limited to this, for example, from among subcarriers determined to have poor line quality according to the number of retransmission requests Subcarriers that are not used may be determined, retransmission data may be allocated to subcarriers other than the subcarriers determined not to be used, and whether to change the modulation scheme of retransmission data may be selected.

Embodiment 6 FIG.
Next, a retransmission control method according to the sixth embodiment will be described. Here, only operations different from those of the first, second, third, fourth, or fifth embodiments will be described.

  FIG. 15 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the sixth embodiment. In the present embodiment, in addition to the configuration of FIG. 9 of the third embodiment, a symbol copy unit 41, a spread processing unit 42, and a code multiplexing unit 43 are further provided. Further, a spreading factor selection unit 40d is provided in the format determination unit 12d. In addition, about the structure similar to Embodiment 1-5 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the third embodiment will be described.

  In the spreading factor selection unit 40d of the format determination unit 12d, when it is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the line quality variation measurement unit 13 Whether to change the spreading rate of retransmission data from the spreading rate of initial transmission data is determined based on information on subcarriers or subcarrier groups that are not used. The format determining unit 12d is notified of the spreading rate of the retransmission data. For example, in a multicarrier system to which CDMA (Code Division Multiple Access) is not applied, one subcarrier is required to transmit one symbol. In a multicarrier CDMA system to which CDMA is applied to OFDM, a spreading factor of 16 is set. When used, 16 subcarriers are required, and when a spreading factor of 8 is used, 8 subcarriers are required. By using this, in the format determination unit 12d, when the spreading factor of the initial transmission data is 16, the number of unused subcarriers or subcarrier groups notified from the channel quality information detection unit 10 at the time of retransmission data transmission Is half of the total number of subcarriers, the spreading factor of retransmission data is determined to be 8.

  The symbol copy unit 41 copies the rearranged frame signal output from the interleaving unit 5 for each symbol based on the format generation information notified from the format determining unit 12d. For example, when the spreading factor indicated by the format generation information is 8, 1 symbol is copied into 8 symbols.

  Based on the format generation information, the spread processing unit 42 multiplies the copied frame signal by an orthogonal code such as an orthogonal variable spreading factor (OVSF) code.

  The code multiplexing unit 43 code-multiplexes the data after spreading processing based on the format generation information. Then, the IFFT unit 6 is notified of the data after code multiplexing. On the receiving side, if the orthogonal codes such as OVSF multiplied by the spreading processing unit 42 are different, the data after code multiplexing can be separated by performing the despreading process.

  Further, when notified that the information data is to be retransmitted, the format determination unit 12 d receives information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13. Based on the information on the carrier or the subcarrier group, it is determined to use the format using the subcarrier excluding the unused subcarrier or the subcarrier group. Also, the spreading rate of retransmission data is determined. Then, format generation information for allocating retransmission data only to subcarriers excluding the subcarriers determined to have poor channel quality is converted into error correction encoding unit 1a, data modulation unit 2, frame generation unit 3, S / The P conversion unit 4, interleave unit 5, symbol copy unit 41, spreading processing unit 42, code multiplexing unit 43 and IFFT unit 6 are notified. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, format generation information for allocating information data to all subcarriers is converted into error correction coding section 1a, data modulation section 2, frame generation section 3, S / P conversion section 4, interleave section 5, symbol copy section 41, This is notified to the spread processing unit 42, the code multiplexing unit 43 and the IFFT unit 6.

  FIG. 16 is a diagram illustrating a configuration of a mobile station that can execute the retransmission control method according to the sixth embodiment. In the present embodiment, a despreading processing unit 44 and a symbol synthesis unit 45 are further provided in addition to the configuration of FIG. 10 of the third embodiment. In addition, about the structure similar to Embodiment 1-5 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the third embodiment will be described.

  In the despreading processing unit 44, the spread processing unit 42 used the frequency component signal in each subcarrier output from the FFT unit 22 based on the format information notified from the format information detecting unit 28b. By multiplying by the OVSF code, the desired signal is separated from the signal code-multiplexed by the code multiplexing unit 43.

  Based on the format information and the channel quality estimation result for each subcarrier output from the channel quality estimator 29, the symbol synthesizer 45 applies the details of the despread signal to the symbol copy unit 41 in detail. Maximum ratio combining is performed for each symbol copied according to the spreading factor. Then, the signal after the symbol synthesis is output to the deinterleave unit 23.

  The format information detection unit 28b is required for despreading processing, symbol synthesis processing, deinterleaving processing, P / S conversion processing, frame division processing, data demodulation processing, packet synthesis processing, and error correction decoding processing from the received control data. Information (format information) is extracted, and the extraction result is converted into a despreading processing unit 44, a symbol synthesis unit 45, a deinterleaving unit 23, a P / S conversion unit 24, a frame division unit 25, a data demodulation unit 26, and reception information. The data buffer unit 32 and the error correction decoding unit 27a are notified.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, The spreading rate of retransmission data is determined and transmitted, and the mobile station demodulates the despread retransmission data. That is, all subcarriers are used at the time of initial transmission of data, subcarriers other than those determined to have poor channel quality are used at the time of data retransmission, and the spreading factor of retransmission data is changed. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  In this embodiment, since the spreading factor of retransmission data can be changed even when the number of subcarriers used for retransmission is reduced compared to the time of initial transmission, There is no shortage of carriers. Thereby, the time diversity effect of HARQ and a sufficient coding gain can be obtained by subcarriers excluding subcarriers having poor channel quality.

  In the retransmission control method of the present embodiment, retransmission data is transmitted to subcarriers other than the subcarriers determined to have poor channel quality at the time of retransmission according to the channel quality variation for each subcarrier or each subcarrier group. Allocation and whether or not to change the spreading rate of retransmission data is selected, but is not limited to this. For example, depending on the number of retransmission requests, among subcarriers determined to have poor line quality Subcarriers that are not used may be determined, retransmission data may be assigned to subcarriers other than the subcarriers determined not to be used, and whether to change the spreading rate of retransmission data may be selected.

Embodiment 7 FIG.
Next, a retransmission control method according to the seventh embodiment will be described. Here, only operations different from those in the first, second, third, fourth, fifth or sixth embodiment will be described.

  FIG. 17 is a diagram illustrating a configuration of a base station that can execute the retransmission control method according to the seventh embodiment. In the present embodiment, in addition to the configuration of FIG. 13 of the fourth embodiment, a symbol copy unit 41, a spread processing unit 42, and a code multiplexing unit 43 are further provided. Further, a code multiplexing number selection unit 46e is provided in the format determination unit 12e. In addition, about the structure similar to Embodiment 1-6 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the fourth embodiment will be described.

  When it is notified that the information data is to be retransmitted, the code multiplexing number selection unit 46e of the format determination unit 12e has information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11, and the line quality variation measurement unit 13 Whether to change the code multiplexing number of retransmission data from the code multiplexing number of initial transmission data is determined on the basis of unused subcarrier or subcarrier group information. Then, the code determining unit 12e is notified of the code multiplexing number of the retransmission data. For example, if the code multiplexing number of the initial transmission data is 1, if the number of unused subcarriers or subcarrier groups notified from the channel quality information detection unit 10 during retransmission data transmission is half of the total number of subcarriers, The format determination unit 12e determines the code multiplexing number of the retransmission data as 2.

  The transmission information data buffer unit 17 stores binary information data output to the error correction encoding unit 1a. Here, when it is notified from the retransmission request information detection unit 11 that the information data is retransmitted, the stored information data is extracted based on the transmission sequence number or the like. Further, the extracted information data is divided based on the number of code multiplexes indicated by the format generation information output from the format determination unit 12e, and the result is output as retransmission data. On the other hand, when the information data is not retransmitted, that is, when the information data is correctly received on the receiving side, the stored information data is deleted based on the transmission sequence number, etc., and new information data is output. .

  The code multiplexing unit 43 code-multiplexes the data after spreading processing based on the format generation information. More specifically, when the number of multiplexed codes of retransmission data indicated by the format generation information is 2, a frame signal with a multiplexing number of 2 as shown in FIG. 18 is generated, and each retransmission data has a different orthogonal code. Spread and code-multiplexed. Then, the IFFT unit 6 is notified of the data after code multiplexing. On the receiving side, if the orthogonal codes such as OVSF multiplied by the spreading processing unit 42 are different, the data after code multiplexing can be separated by performing the despreading process.

  In addition, when the format determination unit 12e is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13 Based on the information on the carrier or the subcarrier group, it is determined to use the format using the subcarrier excluding the unused subcarrier or the subcarrier group. Also, the number of multiplexed codes of retransmission data is determined. Then, format generation information for allocating retransmission data only to the subcarriers excluding the subcarriers determined to have poor channel quality is sent to the transmission information data buffer unit 17, the error correction encoding unit 1a, the data modulation unit 2, The frame generation unit 3, S / P conversion unit 4, interleave unit 5, symbol copy unit 41, spreading processing unit 42, code multiplexing unit 43 and IFFT unit 6 are notified. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, the format generation information for allocating information data to all subcarriers is transmitted to the transmission information data buffer unit 17, the error correction encoding unit 1a, the data modulation unit 2, the frame generation unit 3, the S / P conversion unit 4, and the interleaving unit. 5, notify the symbol copy unit 41, the spread processing unit 42, the code multiplexing unit 43 and the IFFT unit 6.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, The code multiplexing number of retransmission data is determined and transmitted, and the mobile station demodulates the despread retransmission data. That is, all subcarriers are used for initial transmission of data, subcarriers other than subcarriers with poor channel quality are used for retransmission of data, and the number of code multiplexes of retransmission data is changed. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  Also, in this embodiment, even when the number of subcarriers used at the time of retransmission is reduced compared with the time of initial transmission, the number of code multiplexes of retransmission data can be changed. There is no shortage of subcarriers. Thereby, the time diversity effect of HARQ and a sufficient coding gain can be obtained by subcarriers excluding subcarriers having poor channel quality.

  In this embodiment, retransmission data is allocated to subcarriers other than subcarriers determined to have poor channel quality at the time of retransmission according to channel quality variations for each subcarrier or subcarrier group, and Whether or not to change the code multiplexing number of retransmission data is selected, but is not limited to this. For example, a sub-carrier that is not used among subcarriers determined to have poor channel quality according to the number of retransmission requests. The carrier may be determined, retransmission data may be allocated to subcarriers other than the subcarriers determined not to be used, and whether to change the number of multiplexed codes of retransmission data may be selected.

Embodiment 8 FIG.
Next, a retransmission control method according to the eighth embodiment will be described. Here, only operations different from those of the first, second, third, fourth, fifth, sixth or seventh embodiment will be described.

  FIG. 19 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the eighth embodiment. In the present embodiment, in addition to the configuration of FIG. 17 of the seventh embodiment, a transmission power control unit 48 is further provided. Further, the format determination unit 12f is provided with a power distribution ratio determination unit 47f. In addition, about the structure similar to Embodiment 1-7 demonstrated previously, the same code | symbol is attached | subjected and the description is abbreviate | omitted. Here, only operations different from those of the seventh embodiment will be described.

  In the power distribution ratio determining unit 47f of the format determining unit 12f, when it is notified that the information data is to be retransmitted, information indicating whether or not to retransmit the information data from the retransmission request information detecting unit 11, and the line quality variation measuring unit 13 Whether or not to change the power distribution ratio of subcarriers to which retransmission data is allocated from the power distribution ratio of initial transmission data is determined based on information on subcarriers or subcarrier groups that are not used. Then, the power distribution ratio for each subcarrier to which retransmission data is allocated is notified to the format determination unit 12f. For example, as shown in FIG. 20, when the power distribution of all subcarriers to which the initial transmission data is allocated is constant, the format determination unit 12f uses unused subcarriers notified from the channel quality information detection unit 10 during retransmission data transmission. If the number or the number of subcarrier groups is half of the total number of subcarriers, the transmission power of subcarriers to which retransmission data is not allocated is reduced by a certain value, and the transmission power for that amount is uniformly distributed to the subcarriers to which retransmission data is allocated. Decide to assign.

  In the transmission power control unit 48, based on the power distribution ratio for each subcarrier indicated by the format generation information output from the format determination unit 12f, the transmission power is transmitted to the data after spreading processing output from the spreading processing unit 42. assign. Then, the data subjected to transmission power control is output to the code multiplexer 43.

  Further, when the format determination unit 12f is notified that the information data is to be retransmitted, the information indicating whether or not to retransmit the information data from the retransmission request information detection unit 11 and the unused sub-channel from the channel quality variation measurement unit 13 are used. Based on the information on the carrier or the subcarrier group, it is determined to use the format using the subcarrier excluding the unused subcarrier or the subcarrier group. Also, a power distribution ratio for each subcarrier to which retransmission data is allocated is determined. Then, format generation information for allocating retransmission data only to the subcarriers excluding the subcarriers determined to have poor channel quality is sent to the transmission information data buffer unit 17, the error correction encoding unit 1a, the data modulation unit 2, The frame generation unit 3, S / P conversion unit 4, interleave unit 5, symbol copy unit 41, spreading processing unit 42, transmission power control unit 48, code multiplexing unit 43 and IFFT unit 6 are notified. On the other hand, if it is notified that the information data is not retransmitted, or if it is notified that the information data is retransmitted, but no subcarrier or subcarrier group is not notified, all subcarriers are used. Decide to use the format you used. Then, format generation information for allocating information data to all subcarriers is divided into transmission information data buffer unit 17, error correction encoding unit 1a, data modulation unit 2, frame generation unit 3, S / P conversion unit 4, and interleave unit. 5, the symbol copy unit 41, the spread processing unit 42, the transmission power control unit 48, the code multiplexing unit 43 and the IFFT unit 6.

  Thus, in the present embodiment, the mobile station notifies the base station of the retransmission request and the channel quality information for each subcarrier or each subcarrier group, and the base station performs each subcarrier or each subcarrier group. According to the fluctuation of the line quality, the retransmission data is assigned to subcarriers other than the subcarriers determined to be poor, and further, depending on the number of subcarriers or subcarrier groups with poor line quality, The power distribution for each subcarrier to which retransmission data is allocated is determined and transmitted, and the mobile station demodulates the retransmission data subjected to predetermined transmission power control. That is, all subcarriers are used for the initial transmission of data, subcarriers other than the subcarriers with poor channel quality are used for data retransmission, and the power distribution for each subcarrier to which retransmission data is allocated is changed. As a result, even if the same subcarrier is affected by frequency selective fading at the time of data re-transmission following the initial transmission of data, even if the channel quality deteriorates continuously, the error tolerance of the transmission signal Therefore, HARQ time diversity effect and sufficient coding gain can be obtained in subcarriers other than subcarriers with degraded channel quality.

  In addition, when the channel quality of the same subcarrier at the time of initial transmission of data and at the time of retransmission of data is temporally fluctuating, the time diversity effect by HARQ can be expected. Allocate and send data. Thereby, the time diversity effect by HARQ and sufficient encoding gain can be acquired, and the fall of a throughput can be suppressed.

  Also, in this embodiment, retransmission data can be allocated to subcarriers other than those having poor channel quality at the time of retransmission, and the power distribution for each subcarrier allocated to retransmission data can be changed. By increasing the power distribution to carriers and reducing the power distribution to poor subcarriers, the transmission power efficiency can be greatly improved. That is, it is possible to improve the signal power versus noise power density of retransmission data on the receiving side.

  In the retransmission control method of the present embodiment, retransmission data is transmitted to subcarriers other than the subcarriers determined to have poor channel quality at the time of retransmission according to the channel quality variation for each subcarrier or each subcarrier group. Allocation and whether to change the power distribution for each subcarrier to be allocated to retransmission data are selected. However, the present invention is not limited to this. For example, the line quality is determined to be poor depending on the number of retransmission requests. Select subcarriers that are not used from among subcarriers, assign retransmission data to subcarriers other than those determined not to be used, and select whether to change the power distribution for each subcarrier assigned to retransmission data It is good to do.

  As described above, the retransmission control method and the communication apparatus according to the present invention are useful for a communication system that employs a multicarrier modulation / demodulation method, and are particularly compatible with communication environments that may be affected by frequency selective fading. It is suitable as a reliable retransmission control method and communication apparatus.

It is a figure which shows the concept of the allocation process of the subcarrier of the retransmission control method concerning this invention. FIG. 3 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method of the first embodiment. It is a figure which shows an example of the frame signal produced | generated by the frame production | generation part. It is a figure which shows the format except a subcarrier or subcarrier group with inferior circuit quality. 3 is a diagram showing a configuration of a mobile station capable of executing the retransmission control method of Embodiment 1. FIG. FIG. 10 is a diagram illustrating a configuration of a base station that can execute the retransmission control method of the second embodiment. FIG. 10 is a diagram illustrating a specific retransmission control method according to the second embodiment. It is a figure which shows the basic operation principle of HARQ. FIG. 10 is a diagram illustrating a configuration of a base station that can execute the retransmission control method of the third embodiment. FIG. 11 is a diagram illustrating a configuration of a mobile station that can execute the retransmission control method according to the third embodiment. It is a figure which shows the structure of an error correction encoding part. It is a figure which shows the structure of an error correction decoding part. FIG. 10 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method of the fourth embodiment. FIG. 10 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the fifth embodiment. FIG. 10 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the sixth embodiment. FIG. 10 is a diagram illustrating a configuration of a mobile station capable of executing the retransmission control method according to the sixth embodiment. FIG. 10 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the seventh embodiment. FIG. 10 is a diagram illustrating a frame format according to the seventh embodiment. FIG. 10 is a diagram illustrating a configuration of a base station capable of executing the retransmission control method according to the eighth embodiment. It is a figure which shows an example of transmission power control. It is a figure which shows the structure of the conventional multicarrier mobile communication system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Error correction encoding part 2 Data modulation part 3 Frame generation part 4 S / P (Serial / Parallel) conversion part 5 Interleaving part 6 IFFT (Inverse Fast Fourier Transform) part 7 GI (Guard Interval) insertion part 8 Transmission RF (Radio Frequency) unit 9 Reception RF unit 10 Channel quality information detection unit 11 Retransmission request information detection unit 12, 12a, 12b, 12c, 12d, 12e, 12f Format determination unit 13 Channel quality fluctuation measurement unit 14 Transmission request number counter unit 15a HARQ scheme selection unit 16b retransmission data division determination unit 17 transmission information data buffer unit 18c adaptive modulation scheme selection unit 19 adaptive modulation unit 20 reception RF unit 21 GI removal unit 22 FFT (Fast Fourier Transform) unit 23 deinterleaving unit 24 P / S (Parallel / Serial) conversion unit 25 frame division unit 26 data demodulation unit 27, 27a Error correction decoding unit 28, 28a, 28b Format information detection unit 29 Channel quality estimation unit 30 Retransmission request determination unit 31 Transmission RF unit 32 Reception information data buffer unit 40d Spreading rate selection unit 41 Symbol copy unit 42 Spreading processing unit 43 Code multiplexing 44 Despreading processing unit 45 Symbol synthesis unit 46e Code multiplexing number selection unit 47f Power distribution ratio determination unit 48 Transmission power control unit

Claims (2)

A communication method applied to a receiving apparatus that performs communication using a subcarrier or a subcarrier group with a transmitting apparatus,
A retransmission data receiving step for receiving retransmission data from the transmission side device;
A line quality measurement step for measuring a line quality for each subcarrier or each subcarrier group;
A line for transmitting at least one of the average value of the line quality for each subcarrier or each subcarrier group and the variation amount of the line quality, which is derived based on the measured line quality and the past line quality, to the transmission side apparatus. A quality transmission step;
A communication method comprising: A communication method applied to a receiving apparatus that performs communication using a subcarrier or a subcarrier group with a transmitting apparatus,
A retransmission data receiving step for receiving retransmission data from the transmission side device;
A line quality measurement step for measuring a line quality for each subcarrier or each subcarrier group;
A channel quality information calculating step for calculating an average value and variance of the channel quality for each subcarrier or each subcarrier group based on the measured channel quality and the past channel quality;
A communication method comprising:

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