WO2013001837A1

WO2013001837A1 - Receiving device and buffer control method

Info

Publication number: WO2013001837A1
Application number: PCT/JP2012/004247
Authority: WO
Inventors: 大輔富嶋
Original assignee: パナソニックモバイルコミュニケーションズ株式会社; 株式会社エヌ・ティ・ティ・ドコモ
Priority date: 2011-06-29
Filing date: 2012-06-29
Publication date: 2013-01-03
Also published as: JP2013012916A

Abstract

The purpose of the present invention is to reduce writing of soft decision data to a buffer and reduce power consumption without leading to throughput reduction in a HARQ process. A receiving device has a buffer (20) for storing soft decision data in a symbol string extracted from a received signal, and is provided with a buffer controller (30) for modifying the storage size of soft decision data to be written to the buffer (20) on the basis of quality information that expresses the quality of a communication channel, in a receiving device that re-decodes the original data on the basis of the soft decision data stored in the buffer (20) and the symbol string of resent received signals in the case that the original data cannot be reproduced from the symbol string.

Description

Receiving apparatus and buffer control method

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

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

In the HARQ technology, a terminal (UE: User Equipment) is required to be provided with a buffer that temporarily stores soft decision data of a received code string (for example, a symbol 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 symbol string extracted from the received signal is soft-decided, and the 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 symbol 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 that define 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.

Also, Non-Patent Document 2 discloses a technique for performing the following measures when the transmission data after turbo encoding becomes 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.

In the above-described conventional HARQ process, all the LLR data of the received symbol string is stored in the IR buffer regardless of the communication quality and the radio wave propagation environment. Therefore, if the error rate of the received symbol sequence is low due to good communication quality or propagation environment, the LLR data stored in the IR buffer is hardly used, and 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 symbol string, a buffer for storing soft decision data of the symbol 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 a retransmitted symbol sequence of the received signal, a decoding unit that performs decoding processing 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 can be reduced to reduce wasteful power consumption. Furthermore, when many code errors occur and many error corrections are required, it is possible to prevent the decoding processing throughput from being lowered by returning the soft decision data writing size to the original size.

The block diagram which shows the structure of the radio | wireless receiver of embodiment of this invention Block diagram showing in detail the periphery of the IR buffer of the first embodiment A flowchart for explaining the operation of the buffer control unit according to the first embodiment. The figure explaining the storage state of LLR data when the usage rate of the IR buffer is 100% in the first embodiment FIG. 10 is a diagram for explaining an example of a storage state of LLR data when the usage rate of the IR buffer is set low in the first 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 Embodiment 2 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 Flowchart for explaining the operation of the buffer control unit of the second embodiment The figure explaining the storage state of LLR data when the usage rate of the IR buffer is 100% in the second embodiment FIG. 10 is a diagram for explaining an example of a storage state of LLR data when the IR buffer usage rate is set low in the second embodiment Block diagram showing in detail the periphery of the IR buffer of the third embodiment First part of a flowchart for explaining the operation of the buffer control unit according to 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 performs communication 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 synchronization process for signals AD-converted by the receiving radio unit 13 And an IFFT processing unit 14 for extracting a symbol string by performing an inverse Fourier transform process, and signal separation / demodulation for obtaining an LLR (log likelihood ratio) by performing channel estimation and soft decision on the extracted symbol string Unit 15, a derate matching unit 16 that restores the symbol arrangement rate-matched at the base station to the LLR data (soft decision data) of the symbol sequence, and the LLR data for processing by the derate matching unit 16 The circular buffer 17 for temporarily storing, the IR buffer 20 for temporarily storing LLR data for the HARQ process, and the overall IR buffer 20 An IR buffer control unit 30 that performs control, a HARQ synthesis processing unit 18 that performs synthesis processing of LLR data of the symbol sequence retransmitted by the HARQ process, and LLR data stored in the IR buffer 20, and a received symbol sequence A turbo decoding unit 19 that performs turbo decoding processing to restore original data is provided.

In addition, the 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 subcarrier modulation with a symbol string after rate matching in parallel The modulation unit 44, the FFT unit 45 for adding a CP (cyclic prefix) by performing FFT (Fast Fourier Transform) processing on a 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, this wireless communication apparatus is provided with 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 received by being superimposed. As a result, the wireless communication apparatus can be switched to a MIMO (Multi-Input-Multi-Output) transmission method.

The HARQ combining processing unit 18 performs combining processing between the LLR data of the retransmitted symbol string and the stored LLR data as described above during the period in which the data retransmission by the HARQ process is performed. Then, the HARQ synthesis processing unit 18 sends the synthesized LLR data to the turbo decoding unit 19 and the IR buffer control unit 30. On the other hand, during the period in which the data retransmission by the HARQ process is not performed and the first data transmission is performed, the HARQ synthesis processing unit 18 uses the LLR data of the symbol sequence transmitted from the derate matching unit 16 as it is. The data is sent to the turbo decoding unit 19 and the IR buffer control unit 30.

(Embodiment 1)
FIG. 2 is a block diagram showing details of the IR buffer 20 and the IR buffer control unit 30 according to the first embodiment.

The IR buffer control unit 30 according to 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 valid signal generation unit 33. Then, the write control unit 31 converts the LLR data (w.LLR) sent from the HARQ combining processing unit 18 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 write control unit 31 discards the LLR data sent from the HARQ synthesis processing unit 18 during a period in which 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. When an automatic retransmission request is made in the HARQ process and data retransmission is performed, the read control unit 32 starts read control in synchronization with the reception process of the retransmission data. When the read control is started, the read control unit 32 reads 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. The read control unit 32 does not read LLR data while the buffer enable is invalid. Read address r. “add” is incremented every time the LLR data is read.

The buffer control unit 34 determines the size of LLR data to be 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 the control information, any 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: whether or not 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 the 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, the buffer control unit 34 compares these with predetermined thresholds th_CQI and th_PER (step 302). As a result, if both average values avg_CQI, avg_PER are equal to or greater than the threshold values th_CQI, th_PER, the buffer control unit 34 sets the number of internal loops, which is an internal variable, to “0” (step 303), and the IR buffer 20 Is determined to be 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 and avg_PER are smaller than the threshold values th_CQI and th_PER, the buffer control unit 34 determines whether or not the current HARQ process retransmission count is 1 or less. (Step 305). If it is two or more times, the buffer control unit 34 performs the processing of steps 303 and 304. If it is one or less time, the processing of the buffer control unit 34 proceeds to step 306.

In step 306, the buffer control unit 34 determines whether or not the number of inner loops is greater than “0”. If “0”, the buffer controller 34 determines the usage rate of the IR buffer 20 to be 70% (step 307), and The number of 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, the buffer control unit 34 adds “+1” to the number of inner loops (step 309), and then determines whether or not the current transmission data is for retransmission. Is determined (step 310). If it is retransmission data, the buffer control unit 34 increases the usage rate of the IR buffer by one step (step 311). On the other hand, if it is the first transmission data, the buffer control unit 34 reduces the usage rate of the IR buffer 20 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. Multiply rate. Then, the buffer control unit 34 determines the size of the calculation result as the total use size of the IR buffer 20 that stores 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 buffer control unit 34 must distribute the total used size of the IR buffer 20 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). When LTE-TDD wireless connection is selected, the buffer control unit 34 equally distributes all used sizes of the IR buffer 20 by a plurality of HARQ processes, and assigns them to the IR buffer 20 by each HARQ process. The data length of the LLR data to be stored may be determined. Then, the buffer control unit 34 notifies the IR buffer storage valid signal generation unit 33 of the data length of the LLR data as the storage size information (LLR size).

The buffer control unit 34 performs the above-described change control of the storage size of the LLR data in accordance with the start timing of each HARQ process. Alternatively, the buffer control unit 34 executes such change control at an arbitrary cycle and an arbitrary timing. When the storage size of the LLR data is changed at an arbitrary timing, the buffer control unit 34 applies the change in the storage size from the start of the next HAQR process (when receiving the first data, not the retransmission data). To be controlled.

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 a different code range is performed based on RV (Redundancy Version), the following processing is performed. That is, only the LLR data that overlaps the code range 22 in which the LLR data is previously stored is stored in the IR buffer 20, and the LLR data in a range that does not overlap with 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 symbol arrangement of the received symbol string is changed by the derate match unit 16. Therefore, when only the LLR data in the predetermined code range 22 is stored in the IR buffer 20, it is distinguished whether or not the LLR data of the received symbol 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 LLR data of the received symbol sequence in the circular buffer 17 in the order of addresses, and then reads them 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. The IR buffer storage valid signal generation unit 33 inputs the read address of the circular buffer 17 and validates the buffer enable if the read address is in the address range 17b, and enables the buffer enable if the read address is outside the address range 17b. Is invalid.

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 symbol string is extracted from the signals received by the reception radio unit 13 and the synchronization / IFFT processing unit 14.
Subsequently, after the symbol separation is determined softly 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 symbol sequence by the turbo decoding unit 19 and the original data cannot be restored due to a code error, an automatic retransmission request for 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, the reception radio unit 13 and the synchronization / IFFT processing unit 14 extract a signal reception and redundant symbol sequence, and the signal separation / demodulation unit 15 extracts this symbol sequence. Is soft-decided.

Subsequently, the LLR data stored in the IR buffer is read out under the control of the IR buffer control unit 30, and the LLR data and the LLR data of the redundant symbol sequence 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 radio 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.

(Embodiment 2)
FIG. 7 is a block diagram illustrating details of the IR buffer 20 and the IR buffer control unit 30 according to 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 symbol string as in the first embodiment. And stored in the IR buffer 20.

The IR buffer control unit 30 according to 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.

As with 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. Then, the write control unit 31A writes the LLR data supplied when the buffer enable is valid to the IR buffer 20. Furthermore, the write control unit 31A according to the second embodiment receives right bit shift amount data (right bit shift value) 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. Then, the write control unit 31A writes this LLR data to the IR buffer 20.

FIG. 8A shows a diagram for explaining bit shift processing of LLR data 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, when the most significant value of the bits to be discarded is “1”, the write control unit 31A adds “1” to the least significant bit of the remaining bits and rounds off. It is also possible to prevent the fraction processing error from accumulating.

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. Read LLR data from. Then, the read control unit 32A outputs the read LLR data to the HARQ synthesis processing unit 18. Furthermore, the read control unit 32A according to the second embodiment receives left bit shift amount data (left bit shift value) from the buffer control unit 34A. Then, when reading the LLR data from the IR buffer 20, the read control unit 32A performs bit shift on the individual LLR data by the left bit shift amount, and restores the bit width of the individual LLR data. After that, the read control unit 32A sends the LLR data to the HARQ synthesis processing unit 18.

FIG. 8B is a diagram illustrating the bit shift processing of LLR data performed by the read control unit 32A. For example, when the left bit shift amount is 4 bits and the 4-bit-wide LLR data is stored in the IR buffer 20, the read control unit 32A bit-shifts the bit string before the shift in the upper direction and sets the lower 4 bits to zero. Pack with 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 HARQ synthesis processing unit 18 can synthesize LLR data by a normal processing operation in the LLR data synthesis process. 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 buffer control unit 34A writes the right bit shift amount data (right bit shift value) and the left bit shift amount data (left bit shift value) corresponding to the bit width to the write control unit 31A and the read control unit 32A. And output respectively.

FIG. 9 shows a flowchart for explaining the operation of the buffer control unit 34A. In this flowchart, the processing (steps 301 to 313) until the total use size of the IR buffer 20 is determined is the same as 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, the buffer control unit 34A causes the maximum value of the total size of the LLR data stored in each of the plurality of HARQ processes to be the above-determined total use size. The total used size of the IR buffer 20 is distributed to each HARQ process. When the LTE-TDD wireless connection is selected, the buffer control unit 34A may distribute all the used sizes of the IR buffer 20 evenly in a plurality of HARQ processes. Then, the buffer control unit 34A determines the bit width of the LLR data so that each buffer size distributed to each HARQ process fits from the start end to the end of a set of transmitted symbol sequences (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 symbol sequence 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 symbol sequence are uniformly reduced in bit width, and the IR buffer 20 Stored in In FIGS. 10A and 10B, the LLR data storage portion is shown by shading.

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 communication channel quality 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.

(Embodiment 3)
FIG. 11 is a block diagram showing details of the IR buffer and IR buffer control unit of the third embodiment.

In the third embodiment, the IR buffer 20 is composed of a plurality of buffer blocks 20A to 20F that can individually control power. In Embodiment 3, when the usage rate of the IR buffer 20 is reduced, the power of the unused blocks among the buffer blocks 20A to 20F is switched off to further reduce the power consumption.

The buffer blocks 20A to 20F are divided into different sizes (some 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 the size of the buffer block 20A being “518400 bits” and the size of the buffer block 20B being “259200 bits”, are described in each column of “Block A” to “Block F” in Table 2 to be described later. is 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 the corresponding block among the buffer blocks 20A to 20F. Further, when the write control unit 31B sequentially writes a series of LLR data in the HARQ process, the write control unit 31B sequentially generates the addresses of blocks that are powered on among the buffer blocks 20A to 20F as write addresses. Has a function of generating addresses.

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 the series of LLR data in the HARQ process, the read control unit 32B sequentially generates the addresses of the blocks that are powered on among the buffer blocks 20A to 20F as read addresses. It has a function to generate an address.

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, the buffer control unit 34B, for example, turns on the power of the buffer blocks 20A to 20F. It is configured to send off information to the write control unit 31B and the read control unit 32B. Alternatively, the buffer control unit 34B is configured to appropriately select an address range used for automatic generation for each HARQ process, and to send information on this address range to the write control unit 31B and the read control unit 32B. May be. Thereby, the above address generation is realized.

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. Then, the buffer control unit 34B outputs the right bit shift amount data and the left bit shift amount data corresponding to the bit width to the write control unit 31A and the read control unit 32A, respectively. Further, the buffer control unit 34B determines which of the buffer blocks 20A to 20F are used and which block is not used, and outputs a signal “Power ON / OFF” for switching these power on / off. Next, details of these operations will be described.

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

In the third embodiment, in order to prevent the usage rate of the IR buffer 20 from being switched in the range of 80% or more, the buffer control unit 34B may change the usage rate setting stepwise in

step

311 or 312. , The process proceeds to step 1001. Then, the buffer control unit 34B determines whether the usage rate of the IR buffer 20 set at this time is 80% or more (step 1001). If the result is less than 80%, the processing of the buffer control unit 34B proceeds to step 1003 as it is. On the other hand, if it is 80% or more, the buffer control unit 34B sets the usage rate of the IR buffer 20 to 100% and sets the number of internal loops, which is an internal variable, to “0” (step 1002). Then, the buffer control unit 34B advances the process to step 1003.

When the usage rate of the IR buffer 20 is determined in

steps

304, 307, 311, 312, and 1002, and the processing proceeds to step 1003, the buffer control unit 34 multiplies the specified size of the IR buffer by the usage rate. Then, the buffer control unit 34 determines the size of the calculation result as the total use size of the IR buffer 20 that stores the LLR data. Further, the buffer control unit 34 determines a block to be turned on and a block to be turned off among the buffer blocks 20A to 20F so as to ensure the total use size (step 1003).

In the column of “Block A to Block F” in 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%, the buffer control unit 34 sets the three

buffer blocks

20A, 20C, and 20D to power on in step 1003. decide. As a result, the total used size “864000 bits” of the IR buffer 20 is secured. If the UE category is HSPA + category 20 and the usage rate of the IR buffer is determined to be 35%, the buffer control unit 34 determines in step 1003 that the buffer block 20C is a block to be powered on. As a result, the total use size “172800 bits” of the IR buffer 20 is secured.

When the block for switching power on / off is determined in Step 1003, the buffer control unit 34 outputs a signal for switching power on / off 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 buffer control unit 34 determines the data length (number of LLRs) and bit width of the LLR data (step 1004). Then, the buffer control unit 34 outputs the determined data length of the LLR data to the IR buffer storage effective signal generation unit 33 as storage size information (LLR size). Further, the buffer control unit 34 associates the determined bit width with the right bit shift amount data (right bit へ shift value) to the write control unit 31B and the left bit shift amount data (left bit shift value) to the read control unit 32B. ) Is output.

The IR buffer storage valid signal generator 33 operates in the same manner as in the first embodiment. That is, the IR buffer storage valid signal generation unit 33 inputs the storage size information and the read address of the circular buffer 17. The IR buffer storage valid signal generation unit 33 compares the read address with the address range 17b (see FIG. 5) determined based on the storage size information, and determines whether the buffer enable is valid based on the comparison result. Switch between 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 and the total use size of the IR buffer 20 is reduced, the buffer block Of the 20A to 20F, the power of the unused blocks 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, examples in which the number of retransmissions by CQI, PER, and HARQ process are applied as quality information indicating the quality of the communication channel are shown. However, the quality information may include the Doppler shift frequency of the radio signal or the delay spread of the radio signal. In the first to third embodiments, a configuration is shown in which the HSPA + and LTE wireless connection schemes, MIMO and other wireless transmission modes can be switched, but the wireless connection scheme and the wireless transmission mode are fixed. Also good. In the first to third embodiments, an example is shown in which LLR is applied as soft decision data of a received symbol string. However, another function value is applied if it represents the likelihood of a symbol string. May be.

The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2011-144411 filed on June 29, 2011 is incorporated herein by reference.

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

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

A buffer for storing soft decision data of a symbol sequence extracted from a received signal;
The original data is decoded from the symbol sequence, and when the original data cannot be restored, the original data is regenerated based on the soft decision data stored in the buffer and the retransmitted symbol sequence of the 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;
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 when the decoding process is performed again;
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 symbol sequence extracted from the received signal is stored in a buffer,
When the original data could not be restored from the symbol sequence, the original data is decoded again based on the soft decision data stored in the buffer and the retransmitted symbol sequence of the 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.