JP2013012916A - Receiver device and buffer control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption by reducing storage of a soft decision data into a buffer, without producing a decreased throughput in an HARQ process.SOLUTION: A reception device includes a buffer (20) for storing a soft decision data of a code string extracted from a reception signal. When the original data cannot be restored from the code string, the reception device performs re-decoding processing of an original data, based on the soft decision data stored in the buffer (20) and the code string of the retransmitted reception signal. The reception device further includes a buffer control unit (30) for modifying the storage size of the soft decision data to be stored into the buffer (20), based on quality information representing the quality of a communication channel.

Description

  The present invention relates to a receiving apparatus, for example, a HARQ (Hybrid Automatic Repeat reQuest) process applied to communication processing of a downlink physical layer of HSPA + (High Speed Packet Access plus) and LTE (Long Term Evolution). The present invention relates to buffer control technology.

  Conventionally, FEC (Forward Error Control: Forward) using turbo codes to perform error correction in HSSCH + HS-DSCH (High Speed Downlink Shared Channel) PDSCH (Physical Downlink Shared Channel) transmission or LTE PDSCH transmission Error correction) technology and HARQ technology are employed.

  In the HARQ technique, a terminal (UE: User Equipment) is required to be provided with a buffer that temporarily stores soft decision data of a received code string. Such a buffer is called a soft buffer or an IR (Incremental Redundancy) buffer. The size of the IR buffer is defined in the UE capability (terminal capability) information together with the throughput information and the like, and the IR buffer size is notified from the terminal to the base station side.

  In PDSCH transmission, transmission data is turbo-encoded, and then processing for matching the data size to the size of the IR buffer of the terminal (HSPA + first rate match, LTE rate match) is performed, and then transmitted to the terminal . At the terminal, the code string extracted from the received signal is softly determined, and LLR (log likelihood ratio) data of the determination result is stored in the IR buffer. Then, in the terminal, the original data is decoded from this code string. If the original data cannot be restored due to a code error as a result of the decoding process, an automatic retransmission request is made from the terminal to the base station by the HARQ process. When the redundant data is retransmitted from the base station in response to this request, the terminal combines the LLR data of the redundant data with the LLR data stored in the IR buffer, and tries to decode the original data again.

  In addition, as a related art related to the present invention, Non-Patent Document 1 shows contents defining the size of a soft buffer. The terminal must appropriately hold the LLR of PDSCH transmission data for HARQ combining, but the size of turbo-encoded data is very redundant and large, more than three times the original data. On the other hand, it is not easy for the terminal to increase the buffer size because it increases the circuit scale and power consumption. Therefore, Non-Patent Document 1 categorizes the size of the soft buffer capable of storing LLR data for some transmission data, and describes the contents that define the size of the soft buffer of the terminal according to this category. Yes.

  Non-Patent Document 2 discloses a technique for performing the following measures when transmission data after turbo encoding is larger than the size of the soft buffer of the terminal. That is, when the transmission data after turbo coding is divided into a plurality of code blocks and transmitted, individual sizes (division sizes) obtained by dividing the soft buffer of the terminal by the number of code blocks are calculated. And the data of the said division size is extracted from the head of each code block, This data is transmitted, On the other hand, the remaining part of each code block is not transmitted.

3GPP TS36.300 V8.2.0, "UE-Category" 3GPP contribution R1-080515

  In the conventional HARQ process, all the LLR data of the received code string is stored in the IR buffer regardless of the communication quality and the radio wave propagation environment. Therefore, when the communication rate or the propagation environment is good and the error rate of the received code string is low, the LLR data stored in the IR buffer is hardly used, so the power consumption when writing the LLR data to the IR buffer is wasted. Become a thing. On the other hand, if the size of the LLR data stored in the IR buffer is simply reduced regardless of the communication quality and radio wave propagation environment, if the error rate of received data increases, the HARQ process There arises a problem that the retransmission combined gain due to becomes low.

  An object of the present invention is to provide a receiving apparatus capable of reducing power consumption by reducing writing of soft decision data to a buffer without causing a decrease in throughput in the HARQ process.

  The receiving apparatus according to the present invention performs a decoding process of the original data from the code string and a buffer for storing the soft decision data of the code string extracted from the received signal, and when the original data cannot be restored, Based on the soft decision data stored in the buffer and the code sequence of the retransmitted received signal, a decoding unit that performs decoding of the original data again, and on the buffer based on quality information indicating the quality of the communication channel And a buffer control unit that changes the storage size of the soft decision data to be written.

  According to the present invention, it is possible to appropriately change the write size of the soft decision data used in the decoding process of the original data to the buffer based on the quality information of the communication channel. Therefore, when code errors do not occur much, the soft decision data write size is reduced to reduce unnecessary power consumption, and when many code errors occur and many error corrections are required. Can return to the original write size of the soft decision data and avoid a decrease in the throughput of the decoding process.

The block diagram which shows the structure of the radio | wireless receiver of embodiment of this invention The block diagram which shows the periphery of IR buffer of 1st Embodiment in detail The flowchart explaining operation | movement of the buffer control part of 1st Embodiment. The figure explaining the storage state of LLR data when the usage rate of the IR buffer is 100% in the first embodiment The figure explaining an example of the storage state of LLR data when the usage rate of IR buffer is set low in 1st Embodiment The figure explaining the order of writing and reading to the circular buffer by the derate match unit The figure which shows an example of the output data of a circular buffer, and the output pattern of a buffer enable The block diagram which shows the periphery of IR buffer of 2nd Embodiment in detail The figure explaining the bit shift process of LLR data performed by the writing control part The figure explaining the bit shift process of LLR data performed by the reading control part The flowchart explaining operation | movement of the buffer control part of 2nd Embodiment. The figure explaining the storage state of LLR data when the usage rate of the IR buffer is 100% in the second embodiment The figure explaining an example of the storage state of LLR data when the usage rate of IR buffer is set low in 2nd Embodiment. The block diagram which shows the periphery of IR buffer of 3rd Embodiment in detail The first part of the flowchart explaining the operation of the buffer control unit of the third embodiment Same as above, part 2 of the flowchart

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a wireless communication apparatus according to an embodiment of the present invention. This wireless communication apparatus is mounted on a mobile terminal (UE: User Equipment) and communicates with a base station using the HSPA + and LTE wireless connection schemes. This radio communication apparatus has a receiving unit (receiving device) configured as a receiving radio unit (Rx-RF) 13 that performs signal processing in the radio frequency domain, and a signal that is AD-converted by the receiving radio unit 13. And an IFFT processing unit 14 for extracting a code string by performing an inverse Fourier transform process, and a signal separation / demodulation for obtaining an LLR (log likelihood ratio) by performing channel estimation and soft decision on the extracted code string Unit 15, a derate matching unit 16 that restores the code sequence rate matched at the base station to the LLR data (soft decision data) of the code string, and the LLR data for processing by the derate matching unit 16 A circular buffer 17 that temporarily stores, an IR buffer 20 that temporarily stores LLR data for the HARQ process, and an IR buffer that performs overall control of the IR buffer 20 And the HARQ synthesis processing unit 18 for synthesizing the LLR data of the code sequence retransmitted by the HARQ process and the LLR data stored in the IR buffer 20, and turbo decoding for the received code sequence A turbo decoding unit 19 that performs processing to restore original data is provided.

  In addition, this wireless communication apparatus includes a CRC adding unit 41 that adds a CRC (Cyclic Redundancy Check) code for error detection to transmission data, and error correction for the transmission data to which the CRC code is added. A turbo encoding unit 42 that generates a turbo code that enables transmission, a rate matching unit 43 that performs rate matching on transmission data after turbo encoding, and a code string after rate matching is parallel-subcarrier modulated The modulation unit 44, the FFT unit 45 for adding a cyclic prefix (CP) by performing FFT (Fast Fourier Transform) processing on the plurality of subcarrier signals output from the modulation unit 44, and the FFT-processed signal for wireless transmission A transmission radio unit (Tx-RF) 46 for adjusting and amplifying and outputting is provided.

  Further, the wireless communication apparatus includes an antenna element 11 that transmits and receives radio waves, an antenna sharing unit 12 that switches the antenna element 11 between reception and transmission, and a control unit 50 that performs communication processing in an upper layer. It has been. The reception data decoded by the turbo decoding unit 19 is input to the control unit 50, and the transmission data sent to the CRC adding unit 41 is output from the control unit 50. The control unit 50 performs error detection on the received data. In addition, the control unit 50 monitors the reception operation and generates various information related to the quality of the communication channel and the communication method.

  Although not shown in FIG. 1, the wireless communication apparatus includes a W-CDMA (Wideband Code Division Multiple Access) wireless unit and a modulation / demodulation unit. These can be switched to the configuration of the receiving radio unit 13, the synchronization / IFFT processing unit 14, the signal separation / demodulation unit 15, the transmission radio unit 46, the FFT unit 45, and the modulation unit 44 of the OFDMA (Orthogonal Frequency Division Multiple Access) system. Has been. By this switching, the LTE system and the HSPA + system can be switched. In addition, the wireless communication apparatus includes a plurality of antenna elements 11 and a signal separation unit that separates a plurality of reception signals transmitted from the plurality of antennas and superimposed and received, and is configured to perform MIMO (Multi Input Multi Output). It is also possible to switch to the transmission method.

  The HARQ combining processing unit 18 performs combining processing of the LLR data of the retransmitted code string and the stored LLR data as described above during the period in which the data retransmission by the HARQ process is performed. The LLR data is sent to the turbo decoding unit 19 and the IR buffer control unit 30. On the other hand, during the period when the data retransmission by the HARQ process is not performed and the first data transmission is performed, the LLR data of the code string sent from the derate matching unit 16 is directly used as the turbo decoding unit 19 and the IR buffer. It is configured to send to the control unit 30.

[First Embodiment]
FIG. 2 is a block diagram showing details of the IR buffer 20 and the IR buffer control unit 30 of the first embodiment.

  The IR buffer control unit 30 of the first embodiment includes a write control unit 31, a read control unit 32, an IR buffer storage valid signal generation unit 33, a buffer control unit 34, and the like.

  The write control unit 31 receives the LLR data supplied from the HARQ synthesis processing unit 18 and the buffer enable signal output from the IR buffer storage effective signal generation unit 33. Then, the LLR data (w.LLR) sent from the HARQ synthesis processing unit 18 during the period in which the buffer enable is valid is converted into the write address w. By outputting to the IR buffer 20 together with the add, the LLR data is written to the IR buffer 20. On the other hand, the LLR data sent from the HARQ synthesis processing unit 18 is discarded during the period when the buffer enable is invalid. Write address w. The add is initialized to the start address for each HARQ process at the start of one HARQ process, and thereafter incremented and updated each time LLR data is written.

  The read control unit 32 receives the buffer enable output from the IR buffer storage valid signal generation unit 33, and performs control to read LLR data (r.LLR) from the IR buffer 20 in synchronization with the HARQ process. Specifically, at the start of one HARQ process, the read address r. add is initialized to the start address for each HARQ process. Then, when an automatic retransmission request is made in the HARQ process and data retransmission is performed, read control is started in synchronization with the reception process of the retransmission data. When the read control is started, the read address r. The add is output to the IR buffer 20 to read the LLR data, which is output to the HARQ synthesis processing unit 18. During the period when the buffer enable is invalid, LLR data is not read. Read address r. “add” is incremented every time the LLR data is read.

  The buffer control unit 34 determines the size of the LLR data stored in the IR buffer 20 based on the line quality information and control information supplied from the control unit 50, and uses this storage size information (LLR size) as an IR buffer storage valid signal. The data is output to the generation unit 33. Here, the channel quality information, which is a parameter for determining the storage size, includes CQI (channel quality indicator), PER (packet error rate) generated by the control unit 50 for feedback to the base station, and the number of retransmissions by the HARQ process. Is included. In addition, as the control information, any of currently selected RAT (Radio Access Technology: LTE-FDD (frequency division duplex), LTE-TDD (time division duplex) or HSPA + is selected as the system information. ) And wireless transmission mode (Transmission Mode: MIMO). The control information includes the specified size of the IR buffer corresponding to the currently selected RAT, the number of HARQ processes executed in parallel, and the number of code blocks when transmission data is divided into blocks and transmitted. Each information is included.

  FIG. 3 shows a flowchart for explaining the operation of the buffer control unit 34 of the first embodiment.

  When the buffer control unit 34 acquires CQI and PER information from the control unit 50, the buffer control unit 34 obtains the average values avg_CQI and avg_PER from the CQI and PER acquired in the immediately preceding fixed period (step 301). Next, these are compared with predetermined thresholds th_CQI and th_PER, respectively (step 302). As a result, if both of the average values avg_CQI and avg_PER are equal to or greater than the threshold values th_CQI and th_PER, the internal loop count which is an internal variable is set to “0” (step 303), and the usage rate of the IR buffer 20 is set to 100%. (Step 304). In this embodiment, the CQI is defined so that the quality decreases when the value is small and the quality improves when the value is large. The number of inner loops is an internal variable indicating whether or not the usage rate of the IR buffer 20 is being reduced, and the number of times the usage rate has been changed during the period of reduction.

  On the other hand, if it is determined in the comparison in step 302 that both average values avg_CQI, avg_PER are smaller than the thresholds th_CQI, th_PER, respectively, it is determined whether the current HARQ process retransmission count is 1 or less (step 305). If it is two or more times, the processing of steps 303 and 304 is performed.

  In step 306, it is determined whether the number of inner loops is greater than “0”. If “0”, the usage rate of the IR buffer 20 is determined to be 70% (step 307), and the number of inner loops is set to “1”. (Step 308).

  On the other hand, if the number of inner loops is greater than “0” in step 306, first, “+1” is added to the number of inner loops (step 309), and then it is determined whether or not the current transmission data is a retransmission (step 309). 310). If it is retransmission data, the IR buffer usage rate is increased by one step (step 311). On the other hand, if it is the first transmission data, the usage rate of the IR buffer 20 is lowered by one step (step 312).

  As described above, when the usage rate of the IR buffer 20 is determined in steps 304, 307, 311, 312, the buffer control unit 34 then uses the specified size of the IR buffer 20 notified from the control unit 50. By multiplying the rate, the size of the calculation result is determined as the total use size of the IR buffer 20 storing the LLR data (step 313).

  For example, as shown in Table 1, when the UE category is a certain category of LTE and the usage rate of the IR buffer 20 is not limited, the total usage size of the IR buffer is defined as “1327248 bits” defined in the UE category. To be determined. Further, when the UE category is HSPA + category 20 and the IR buffer 20 usage rate is not limited, the total use size of the IR buffer is determined to be “518400 bits” defined in the UE category. When the usage rate is determined to be 70%, 50%, 35%, etc., the IR buffer 20 has a size similar to the value obtained by multiplying the prescribed size corresponding to each UE category by the usage rate. It is determined as the total use size.

  When the total use size is determined in step 313, the buffer control unit 34 subsequently determines the IR buffer from the total use size and the information on the number of HARQ processes, the number of code blocks, and the radio transmission mode notified from the control unit 50. The data length (number of LLRs) of the LLR data stored in 20 is determined as follows. That is, since a plurality of HARQ processes are executed in parallel, the total use size of the IR buffer 20 must be distributed among the plurality of HARQ processes. For this reason, the buffer control unit 34 stores the data length of the LLR data in each HARQ process (the number of LLRs) so that the maximum value of the total size of the LLR data stored in each process becomes the determined total use size. Is determined (step 314). In addition, when the LTE-TDD wireless connection is selected, the data of the LLR data stored in the IR buffer 20 in each HARQ process by equally allocating all the used sizes of the IR buffer 20 in a plurality of HARQ processes. The length may be determined. Then, the data length of the LLR data is notified to the IR buffer storage valid signal generation unit 33 as the storage size information (LLR size).

  The buffer control unit 34 executes the above-described change control of the storage size of the LLR data in accordance with the start timing of each HARQ process. Alternatively, such change control is executed at an arbitrary cycle and an arbitrary timing. When the storage size of the LLR data is changed at an arbitrary timing, control is performed so that the change of the storage size is applied from the start of the next HAQR process (when the first data is received instead of the retransmission data). .

  4A is a diagram for explaining a storage state of LLR data when the usage rate of the IR buffer 20 is 100%, and FIG. 4B is an example of a storage state of LLR data when the usage rate of the IR buffer 20 is set low. FIG. 4A and 4B show the storage state of LLR data in LTE, and RV shows a redundancy version representing the beginning of the transmission code range at the time of retransmission.

  As shown in FIG. 4A, when the line quality is poor and the usage rate of the IR buffer 20 is 100%, all the LLR data of the received data is stored in the IR buffer 20. On the other hand, as shown in FIG. 4B, when the line quality is good and the usage rate of the IR buffer 20 is set low, only the LLR data in the code range 22 of a part of the received data is stored in the IR buffer 20. Be controlled. In this embodiment, when data retransmission is performed by the HARQ process and data retransmission of different code ranges is performed based on RV (Redundancy Version), the following processing is performed. That is, only the LLR data corresponding to the code range 22 in which the LLR data is previously stored is stored, and the LLR data in the range not overlapping the code range 22 is not stored in the IR buffer 20.

  FIG. 5 is a diagram illustrating the order of writing and reading to the circular buffer 17 by the derate matching unit 16, and FIG. 6 is a diagram illustrating an example of output data of the circular buffer 17 and an output pattern of buffer enable. , Respectively.

  The code sequence of the received code string is changed by the derate matching unit 16. Therefore, when only the LLR data of the predetermined code range 22 is stored in the IR buffer 20, it is distinguished whether the LLR data of the received code string is included in the code range 22 in the array after the derate match. There is a need to. In this embodiment, such a distinction is realized by the operation of the IR buffer storage valid signal generation unit 33 based on the read address of the circular buffer 17.

  That is, as shown in FIG. 5, the derate match unit 16 stores the received LLR data of the code string in the circular buffer 17 in the order of addresses, and then reads them out in the order prescribed for the derate match and sends them to the subsequent stage. .

  The IR buffer storage valid signal generation unit 33 first determines the address range 17b of the circular buffer 17 to which the LLR data to be stored in the IR buffer 20 is written based on the storage size information of the LLR data notified from the buffer control unit 34. To do. Then, the read address of the circular buffer 17 is input. If this read address is in the address range 17b, the buffer enable is enabled, and if it is out of the address range 17b, the buffer enable is disabled.

  By such processing, the buffer enable value is switched according to the read address of the circular buffer 17, as shown in FIG. Then, by such a buffer enable signal, the write operation of the write control unit 31 and the read operation of the read control unit 32 are permitted or prohibited, and only the LLR data in the address range 17b is read from or written to the IR buffer 20. It has become.

In the wireless communication apparatus configured as described above, the following reception process is performed.
That is, when a radio wave transmitted from the base station is received, a code string is extracted from the signals received by the wireless reception unit 13 and the synchronization / IFFT processing unit 14.
Subsequently, after the code string is softly determined by the signal separation / demodulation unit 15, the size of the LLR data of the determination result is adjusted by the control of the IR buffer control unit 30 and stored in the IR buffer 20.
Then, when the original data is decoded from the code string by the turbo decoding unit 19 and as a result, the original data cannot be restored due to a code error, an automatic retransmission request of the HARQ process is controlled by the control unit 50. Is transmitted via the transmitter.
Further, when redundant data is retransmitted from the base station in response to this request, signal reception and redundant code strings are extracted by the radio reception unit 13 and the synchronization / IFFT processing unit 14, and this code string is extracted by the signal separation / demodulation unit 15. Is soft-decided.
Subsequently, the LLR data stored in the IR buffer is read under the control of the IR buffer control unit 30, and the LLR data and the LLR data of the redundant code string are combined by the HARQ combining processing unit 18.
Then, the synthesized LLR data is sent to the turbo decoding unit 19, and the original data is decoded again. The synthesized LLR data is also adjusted in size under the control of the IR buffer control unit 30 and stored in the IR buffer 20 in case a second decoding error occurs.
By repeating such reception processing, data transmitted from the base station is received.

  According to the wireless communication apparatus of the first embodiment, during the above reception process, when the communication channel quality is good and the received code error is small, the size of the LLR data stored in the IR buffer 20 is reduced. Thus, the amount of access to the IR buffer 20 is reduced. Therefore, the power consumed by the IR buffer 20 can be reduced. On the other hand, when the quality of the communication channel is poor and the number of received code errors is large, the size of the LLR data stored in the IR buffer 20 is changed in a direction approaching the original size. Can be avoided.

[Second Embodiment]
FIG. 7 is a block diagram showing details of the IR buffer 20 and the IR buffer control unit 30 of the second embodiment.

  In the second embodiment, when the usage rate of the IR buffer 20 is reduced, the bit width of each LLR data is reduced instead of reducing the number of LLR data of the received code string as in the first embodiment. And stored in the IR buffer 20.

  The IR buffer control unit 30 of the second embodiment includes a write control unit 31A, a read control unit 32A, an IR buffer storage valid signal generation unit 33, a buffer control unit 34A, and the like.

  Similarly to the first embodiment, the write control unit 31A receives the LLR data supplied from the HARQ synthesis processing unit 18 and the buffer enable signal output from the IR buffer storage valid signal generation unit 33, respectively. The LLR data supplied when the buffer enable is valid is written to the IR buffer 20. Furthermore, the write control unit 31A of the second embodiment receives right bit shift value data from the buffer control unit 34A. When the LLR data is written to the IR buffer 20, the LLR data is bit-shifted by the right bit shift amount to reduce the bit width of each LLR data. After that, the LLR data is written to the IR buffer 20.

  FIG. 8A is a diagram for explaining the LLR data bit shift processing performed by the write control unit 31A. For example, when one LLR data supplied from the HARQ synthesis processing unit 18 is 8 bits and the right bit shift amount is 4 bits, as shown in FIG. 8A, the write control unit 31A converts the upper 4 bits into the lower direction. Bit shift to the lower 4 bits. By this bit shift, the bit width of the individual LLR data is halved, and the same effect as when the value of the individual LLR data is rounded (rounded) to the upper 4 digits is obtained. In this bit shift, if the most significant value of the bits to be rounded down is “1”, “1” is added to the least significant bit of the remaining bits, and the rounding process error may occur as rounded off. It may not be accumulated.

  Similar to the first embodiment, the read control unit 32A receives the buffer enable signal output from the IR buffer storage valid signal generation unit 33, and synchronizes with the HARQ process when the buffer enable is valid. LLR data is read out from, and output to the HARQ synthesis processing unit 18. Furthermore, the read control unit 32A according to the second embodiment receives left bit shift value data from the buffer control unit 34A. When the LLR data is read from the IR buffer 20, the individual LLR data is bit-shifted by the left bit shift amount to restore the bit width of the individual LLR data. In addition, the LLR data is sent to the HARQ synthesis processing unit 18.

  FIG. 8B is a diagram for explaining the LLR data bit shift processing performed by the read control unit 32A. For example, when the left bit shift amount is 4 bits and LLR data having a 4 bit width is stored in the IR buffer 20, the bit string before the shift is bit-shifted in the upper direction, and the lower 4 bits are padded with zero values. By this bit shift, the bit width of the LLR data is restored to the original while the values of the individual LLR data are rounded to the upper 4 digits. Therefore, the LLR data can be synthesized by the normal processing operation in the LLR data synthesis process of the HARQ synthesis processing unit 18. In addition, the error of the LLR data value due to the reduction / expansion of the bit width due to the bit shift is limited to the lower-order digits.

  The buffer control unit 34A determines the bit width of the LLR data stored in the IR buffer 20 based on the control information supplied from the control unit 50 as shown below. Then, the right bit shift value data (right bit shift value) and the left bit shift value data (left bit shift value) corresponding to the bit width are output to the write control unit 31A and the read control unit 32A, respectively.

  FIG. 9 shows a flowchart for explaining the operation of the buffer control unit 34A. In this flowchart, processing (steps 301 to 313) until the total use size of the IR buffer 20 is determined is the same as that in the first embodiment.

  When the total use size of the IR buffer 20 is determined in step 313, the buffer control unit 34A then stores the information in the IR buffer 20 from the HARQ process number, code block number, and radio transmission mode information notified from the control unit 50. The bit width of the LLR data to be determined is determined as follows. That is, since a plurality of HARQ processes are executed in parallel, each HARQ process is set such that the maximum value of the total size of the LLR data stored in each of the plurality of HARQ processes becomes the above-determined total use size. All the used sizes of the IR buffer 20 are distributed to. In addition, when the LTE-TDD wireless connection is selected, the total used size of the IR buffer 20 may be equally distributed among a plurality of HARQ processes. Then, the bit width of the LLR data is determined so that each buffer size distributed to each HARQ process fits from the start end to the end of a set of transmitted code strings (step 701).

  FIG. 10A is a diagram for explaining the storage state of LLR data when the usage rate of the IR buffer 20 is 100%, and FIG. 10B is an example of the storage state of LLR data when the usage rate of the IR buffer 20 is set low. FIG. As shown in FIG. 10A, when the line quality is not good and the usage rate of the IR buffer 20 is 100%, all the LLR data of the received code string is stored in the IR buffer 20 without reducing the bit width. On the other hand, as shown in FIG. 10B, when the line quality is good and the usage rate of the IR buffer 20 is set low, all the LLR data of the received code string is uniformly reduced in bit width to the IR buffer 20. Stored (the storage portion of the LLR data is shown by shading in FIGS. 10A and 10B).

  In the second embodiment, the storage size information (LLR size) output from the buffer control unit 34A to the IR buffer storage valid signal generation unit 33 is a value according to the prescribed size of the UE category. Therefore, the IR buffer storage valid signal generation unit 33 validates the buffer enable regardless of the read address range of the circular buffer 17 sent from the derate matching unit 16.

  According to the radio communication apparatus of the second embodiment, when the quality of the communication channel is good and the received code error is small, the bit size of the LLR data stored in the IR buffer 20 in each HARQ process is reduced. Therefore, the access amount to the IR buffer 20 is reduced. Therefore, the power consumed by the IR buffer 20 can be reduced. On the other hand, when the quality of the communication channel is poor and the number of received code errors is large, the bit width of the LLR data stored in the IR buffer 20 in each HARQ process changes in the direction in which it is restored. A reduction in the combined gain can be avoided.

[Third Embodiment]
FIG. 11 is a block diagram showing details of the IR buffer and the IR buffer control unit of the third embodiment.

  In the third embodiment, when the IR buffer 20 is configured from a plurality of buffer blocks 20A to 20F that can individually control power, and the usage rate of the IR buffer 20 is reduced, the unused blocks of the buffer blocks 20A to 20F are not used. The power is switched off to further reduce power consumption.

  The buffer blocks 20A to 20F are divided into different sizes (some of which may be the same size), and the total block size can be selected from a large number of sizes by changing the combination of the blocks. . The sizes of the buffer blocks 20A to 20F, such as “518400 bits” for the size of the buffer block 20A and “259200 bits” for the size of the buffer block 20B, are described in each column of “Block A” to “Block F” in Table 2 to be described later. doing.

  As shown in FIG. 11, the IR buffer control unit 30 of the third embodiment includes a write control unit 31B, a read control unit 32B, an IR buffer storage valid signal generation unit 33, and a buffer control unit 34B.

  In addition to the operation of the write control unit 31A of the second embodiment, the write control unit 31B is configured to distribute and output a write address and write data to corresponding blocks among the buffer blocks 20A to 20F. In addition, when a series of LLR data is sequentially written in the HARQ process, a function of generating a series of addresses so that addresses of blocks that are powered on among the buffer blocks 20A to 20F are sequentially generated as write addresses. have.

  In addition to the operation of the read control unit 32A of the second embodiment, the read control unit 32B distributes and outputs the read address to the corresponding block among the buffer blocks 20A to 20F, and reads the read data from the corresponding block. It is configured. In addition, when reading a series of LLR data in the HARQ process, a function of generating a series of addresses so that addresses of blocks that are powered on among the buffer blocks 20A to 20F are sequentially generated as read addresses. Have.

  Although omitted in FIG. 11, in order to realize the address generation function of the write control unit 31B and the address generation function of the read control unit 32B, for example, the buffer control unit 34B may turn on the power of the buffer blocks 20A to 20F. The off information is sent to the write control unit 31B and the read control unit 32B. Alternatively, for each HARQ process, the address range used by the buffer control unit 34B for automatic generation is appropriately selected, and the address generation information is sent to the write control unit 31B and the read control unit 32B. Can also be performed.

  The buffer control unit 34B determines the data length and bit width of the LLR data stored in the IR buffer 20 based on the control information supplied from the control unit 50, and the right bit shift amount data corresponding to this bit width and The left bit shift amount data is output to the writing control unit 31A and the reading control unit 32A, respectively. Further, the block to be used and the non-use block are determined from among the buffer blocks 20A to 20F, and a signal “Power ON / OFF” for switching the power on / off is output. Next, details of these operations will be described.

  12A and 12B are flowcharts for explaining the operation of the buffer control unit 34B of the third embodiment. In this flowchart, the processing of steps 301 to 312 is the same as that of the first embodiment.

  In the third embodiment, in order to prevent the usage rate of the IR buffer 20 from being switched in a range of 80% or more, if the usage rate setting is changed stepwise in step 311 or 312, the processing proceeds to step 1001. Then, it is determined whether the usage rate of the IR buffer 20 set at this time is 80% or more (step 1001). As a result, if it is less than 80%, the process proceeds to step 1003 as it is, but if it is 80% or more, the usage rate of the IR buffer 20 is set to 100%, and the number of internal loops as an internal variable is set to “0”. (Step 1002). Then, the process proceeds to Step 1003.

  When the usage rate of the IR buffer 20 is determined in steps 304, 307, 311, 312, and 1002, and the process proceeds to step 1003, the buffer control unit 34 multiplies the specified size of the IR buffer by the usage rate, The size is determined as the total used size of the IR buffer 20 that stores the LLR data. Further, among the buffer blocks 20A to 20F, the block to be turned on and the block to be turned off are determined so as to ensure the total use size (step 1003).

  In the column of “Block A to Block F” of this table, determination patterns of power on / off (“1” is on and “0” is off) of the buffer blocks 20A to 20F under each condition are shown. For example, if the UE category is the LTE category and the IR buffer usage rate is determined to be 70%, in step 1003, the three buffer blocks 20A, 20C, and 20D are determined to be power-on blocks, and the IR buffer is selected. Control is performed so that all the 20 used sizes “864000 bits” are secured. If the UE category is HSPA + category 20 and the IR buffer usage rate is determined to be 35%, in step 1003, the buffer block 20C is determined to be a power-on block, and the IR buffer 20 total usage size is determined. Control is performed so that "172800 bits" are secured.

  After determining the block for switching on / off the power in Step 1003, the buffer control unit 34 outputs a signal for switching on / off the power to each of the buffer blocks 20A to 20F according to this determination.

  Subsequently, the buffer control unit 34 determines the IR buffer 20 based on the total use size of the IR buffer 20 determined in Step 1003 and the information on the number of HARQ processes, the number of code blocks, and the radio transmission mode notified from the control unit 50. The data length (number of LLRs) of the LLR data stored in and the bit width of each LLR data are determined as follows. That is, the maximum value of the total size of the LLR data stored in the IR buffer 20 in a plurality of HARQ processes becomes the determined total use size, and the influence of the reduction of the LLR data in each HARQ process is not biased. The data length (number of LLRs) and bit width of the LLR data are determined (step 1004). Then, the determined data length of the LLR data is output to the IR buffer storage valid signal generation unit 33 as storage size information (LLR size). Further, right bit shift amount data (right bit shift value) and left bit shift amount data (left bit shift value) are output to the write control unit 31B and the read control unit 32B in correspondence with the determined bit width.

  The IR buffer storage valid signal generator 33 operates in the same manner as in the first embodiment. That is, the storage size information and the read address of the circular buffer 17 are input, and the read address is compared with the address range 17b (see FIG. 5) determined based on the storage size information. Based on the above, the buffer enable is switched between enabled and disabled.

  According to the wireless communication apparatus of the third embodiment, when the data length or bit width of the LLR data stored in the IR buffer 20 is reduced by the HARQ process to reduce the total use size of the IR buffer 20, the buffer block 20A The power of the unused block among ˜20F is turned off. Therefore, the power consumed by the IR buffer 20 can be further reduced by reducing the size of the LLR data.

  In the first to third embodiments, the example in which the CQI, PER, and the number of retransmissions by the HARQ process are applied as the quality information indicating the quality of the communication channel is shown. The Doppler shift frequency or the delay spread of the radio signal may be included. In the first to third embodiments, the HSPA + and LTE wireless connection schemes and MIMO and other wireless transmission modes can be switched. However, the wireless connection scheme and the wireless transmission mode are fixed. It is good. In the first to third embodiments, an example is shown in which LLR is applied as soft decision data of a received code string. However, another function value is applied if it represents the likelihood of a code string. May be.

  The receiving apparatus according to the present invention can be applied to, for example, communication terminals using HSPA + and LTE wireless connection schemes.

16 Derate match unit 17 Circular buffer 18 HARQ synthesis processing unit 19 Turbo decoding unit 20 IR buffer 30 IR buffer control unit 31, 31A, 31B Write control unit 32, 32A, 32B Read control unit 33 IR buffer storage valid signal generation unit 34 , 34A, 34B Buffer control unit

Claims (9)

A buffer for storing soft decision data of a code string extracted from a received signal;
When the original data is decoded from the code string, and the original data cannot be restored, the original data is regenerated based on the soft decision data stored in the buffer and the code string of the retransmitted received signal. A decoding unit for performing the decoding process of
A buffer control unit that changes a storage size of the soft decision data to be written to the buffer based on quality information indicating a quality of a communication channel;
A receiving device. The buffer control unit changes the storage size of the soft decision data based on the quality information and system information representing a signal transmission system.
The receiving device according to claim 1. The buffer has a plurality of buffer blocks that can be switched on and off individually,
The buffer control unit switches off the power of a buffer block that is no longer used among the plurality of buffer blocks due to a change in the storage size of the soft decision data.
The receiving device according to claim 1. The buffer control unit changes the storage size of the soft decision data by reducing or expanding the bit width of each of the soft decision data.
The receiving device according to claim 1. A write control unit for writing the soft decision data into the buffer with a storage size according to the control of the buffer control unit;
When the decoding process is performed again, a read control unit that reads the soft decision data from the buffer with a storage size according to the control of the buffer control unit;
The receiving device according to claim 1, further comprising: A write control unit that discards the lower bits of the individual soft decision data and changes the bit width according to the control of the buffer control unit, and writes the soft decision data with the changed bit width to the buffer;
When the decoding process is performed again, the soft-decision data whose bit width has been changed is read from the buffer, and a read control unit that makes up any lower bits and restores the original bit width;
The receiving device according to claim 4, further comprising: The quality information includes a channel quality indicator generated for feedback to the base station, an error rate of the received packet, the number of retransmissions of the received signal, a Doppler shift frequency of the radio signal, or a delay spread of the radio signal.
The receiving device according to claim 1. The method information includes wireless connection method information or wireless transmission mode information.
The receiving device according to claim 2. The soft decision data of the code string extracted from the received signal is stored in the buffer,
When the original data cannot be restored from the code string, the original data is decoded again based on the soft decision data stored in the buffer and the code string of the retransmitted received signal,
Based on the quality information representing the quality of the communication channel, the storage size of the soft decision data to be written to the buffer is changed.
Buffer control method.

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