JP2019022053A - Radio communication device and radio communication method - Google Patents

Abstract

To reduce bit errors during reception in radio communication in which automatic retransmission control is carried out.SOLUTION: A radio communication device as an embodiment of the present invention includes: a likelihood descrambling unit that detects a first scramble seed from a prescribed region of first likelihood information, i.e. likelihood information on first packet data, and uses the first scramble seed to descramble the first likelihood information and generate second likelihood information; a likelihood combination unit that combines the second likelihood information with third likelihood information to generate fourth likelihood information; and a decoder that decodes the fourth likelihood information.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a wireless communication apparatus and a wireless communication method.

  One of the error control techniques used in wireless communication is HARQ (hybrid automatic repeat request). HARQ uses a combination of automatic retransmission control (ARQ) and forward error correction (FEC). When HARQ is applied to wireless packet communication, when a packet related to the same data is retransmitted, an operation for combining the likelihood information of the original packet and the likelihood information of the retransmission packet is performed on the receiving side, and the combined likelihood By performing decoding using the degree information, the error rate of the retransmission packet can be improved.

  However, in wireless LAN (Local Area Network), even if the retransmitted packet relates to the same data as the original packet, the likelihood information regarding different bit strings is synthesized due to the difference in the scramble initial value. The error rate improvement effect of the retransmitted packet cannot be obtained.

  To avoid this problem, the scrambled initial value is extracted after decoding the retransmitted data once, and after correcting the bit sequence difference caused by the difference in the scrambled initial value for the original packet and the retransmitted packet data, the likelihood is increased. There is a method of synthesizing degree information. However, since this method requires at least two decoding processes, there is a problem that the amount of calculation and the circuit scale increase.

International Publication No. 2015/094257

  Embodiments of the present invention provide a wireless communication apparatus that improves the retransmission error rate of hybrid automatic retransmission control.

  A wireless communication apparatus as an embodiment of the present invention includes a likelihood descrambling unit, a likelihood combining unit, and a decoder. The likelihood descrambling unit detects a first scramble seed from a predetermined region of first likelihood information that is likelihood information of first packet data, and uses the first scramble seed to generate the first likelihood information. The second likelihood information is generated by descrambling. The likelihood combining unit generates the fourth likelihood information by combining the second likelihood information with the third likelihood information. The decoder decodes the fourth likelihood information.

1 is a block diagram illustrating an example of a wireless communication apparatus according to a first embodiment. The figure showing the LPDC encoding process performed at the time of transmission of data. The block diagram which shows the receiving part of the radio | wireless communication apparatus which concerns on 1st Embodiment, and its periphery structure. The figure which shows the detailed structure of the likelihood descrambling part which concerns on 1st Embodiment. The figure which shows the structural example of the scramble part which concerns on 1st Embodiment. The figure showing the process in the code conversion part which concerns on 1st Embodiment. The figure which shows the example which scrambles likelihood information using likelihood conversion bit sequence. The figure showing the processing flow concerning preservation | save of likelihood information of the radio | wireless communication apparatus which concerns on 1st Embodiment, the synthetic | combination calculation of likelihood, and decoding. The figure which shows the example of each data format which concerns on 1st Embodiment. The figure showing the detection of the reception bit error in the radio | wireless communication apparatus which concerns on 1st Embodiment, and a subsequent processing flow. The block diagram which shows an example of the receiving part of the radio | wireless communication apparatus which concerns on 2nd Embodiment, and its periphery structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

(First embodiment)
FIG. 1 is a block diagram illustrating an example of a wireless communication apparatus according to the first embodiment.

  The wireless communication device 1 is electrically connected to the host system 3 and carries data output from the host system 3 by wireless communication. As a form of the host system 3, a tablet, a personal computer, a smart phone, a feature phone, a game machine, a digital camera, a video camera, a smart watch, a health band, a route guidance device, office equipment, a biological information monitor, a POS terminal, a product management terminal An emergency transmitter, a telemetry transmitter, a robot on which a sensor is mounted, a vehicle on which a sensor is mounted, a drone on which a sensor is mounted, and the like may be used.

  The wireless communication system used by the wireless communication apparatus 1 is, for example, an IEEE 802.11 series or a successor standard wireless LAN system, or an IEEE 802.16 series or a successor standard mobile communication system. It may be.

  The wireless communication device 1 includes an antenna 10, an RF unit 50, and a baseband unit 100.

  The antenna 10 is electrically connected to the RF unit 50, and the antenna 10 transmits an electric signal output from the RF unit 50 as a radio wave. The radio wave received by the antenna 10 is input to the RF unit 50 as an electrical signal.

  Although only one antenna 10 is shown in FIG. 1, the wireless communication device 1 may include a plurality of antennas. In this case, the wireless communication apparatus 1 may perform MIMO (Multiple Input, Multiple Output) using a plurality of antennas. Moreover, the structure provided with the antenna for transmission and the antenna for reception separately may be sufficient.

  The size and shape of the antenna 10 are not particularly limited. The antenna 10 may be built in the wireless communication device 1 or may be externally attached. An array antenna may be used as the antenna 10.

  The RF unit 50 includes a local oscillator 51, a mixer 52, a low noise amplifier (LNA) 53, a selector 54, an RF amplifier 55, and a mixer 56. The RF unit 50 converts the signal from the baseband unit 100 from a baseband frequency to a radio frequency and transmits the signal using the antenna 10. The RF unit 50 converts the signal received by the antenna 10 from a radio frequency to a baseband frequency and transfers the signal to the baseband unit 100.

  The local oscillator 51 and the mixers 52 and 56 are used for frequency conversion. The low noise amplifier 53 amplifies the received signal. The RF amplifier 55 amplifies the signal at the time of transmission. The use of the antenna 10 can be switched between reception and transmission of signals by the selector 54.

  The baseband unit 100 includes a scramble unit 110, an LPDC encoder (encoder) 111, a mapping unit 112, a D / A converter (DAC) 113, an A / D converter (ADC) 120, and a demapping unit 121. A likelihood descrambling unit 122, a field determination unit 123, a storage unit 124, a likelihood combining unit 125, a decoder 126, an access control unit 127, and a host interface 128.

  Among these, the scrambler 110, the LPDC encoder 111, the mapping unit 112, and the D / A converter 113 are components related to the transmission function of the baseband unit 100 and are included in the transmission unit 101.

  In addition, the A / D converter 120, the demapping unit 121, the likelihood descrambling unit 122, the field determination unit 123, the storage unit 124, the likelihood combining unit 125, and the decoder 126 are related to the reception function of the baseband unit 100. Element and included in the receiving unit 102.

  The RF unit 50 and each element in the RF unit 50 in FIG. 1, each element in the baseband unit 100 and the baseband unit 100, and the host system 3 are software (programs) that operate on a processor such as a CPU (Central Processing Unit). ), Or dedicated hardware such as a dedicated circuit, or a combination of these. The wireless communication device of FIG. 1 may include a processor that executes software, and a storage medium such as a memory that stores software and data, a hard disk, and an SSD (Solid State Drive).

  Hereinafter, after describing the components included in the transmission unit 101, the components included in the reception unit 102 and other components in the baseband unit 100 will be described.

  FIG. 2 shows LDPC (Low Density Parity Code) encoding processing performed at the time of transmission by the transmission unit 101. Error correction codes are roughly classified into block codes and convolutional codes. LDPC is a kind of block code.

  The scramble unit 110 scrambles the transmission target data 201 using the scramble initial value 204. As an example, the scramble initial value 204 is a random 7-bit bit string excluding a bit string in which all bits are “0”. Data 201 is converted into a data series 202 by scramble processing. Since the scramble initial value 204 is necessary when descrambling data on the receiving side, it is added to the head of the data series 202. The illustrated bit string 203 is a bit string including a scramble initial value 204 and a data series 202.

  The encoder 111 generates a plurality of LDPC frames by performing LDPC encoding of the data series 202 for each predetermined number of bits. By LDPC encoding, a data sequence is generated for each fixed number of bits, and a redundant portion called a parity portion is added after the generated data sequence. The parity part has a role of protecting the input data series 202. The size (length) of the parity part and the size (length) of the generated data sequence are determined by the coding rate.

  The leading LDPC frame 207 is a bit sequence including a scramble initial value 204, a data sequence 205, and a parity part 206. The second and subsequent LDPC frames are bit sequences including a data sequence and a parity part. For example, the second LDPC frame 210 includes a data series 208 and a parity part 208. One or more LDPC frames not shown in FIG. 2 may follow behind the LDPC frame 210. The LDPC frame 207 including the scramble initial value 204 corresponds to the head portion of packet data (hereinafter referred to as a packet).

  The mapping unit 112 modulates the bit sequence of the LDPC frame output from the encoder 111. As an example of the modulation method used by the mapping unit 112, ASK (amplitude shift keying), BPSK (binary phase shift keying), FSK (frequency shift keying, etc.) or QAM (quadrature modulation, etc.) are used. May be.

  The mapping unit 112 may further perform secondary modulation as necessary. Secondary modulation schemes include DS (direct sequence), FH (frequency hopping), TDMA (time division multiple access), FDMA (frequency division multiple access), CDMA (code division multiple access), CDMA (code division multiplex access). However, any method may be used. In the following description, it is assumed that secondary modulation as described here is not performed.

  The D / A converter 113 converts the digital modulation signal output from the mapping unit 112 into an analog signal. The circuit system of the D / A converter includes a current output type, a resistance ladder type, and a delta sigma type, but other types may be used.

  The analog signal output from the D / A converter 113 is transmitted from the antenna 10 after being up-converted to a radio frequency and power amplified by the RF unit 50.

  As shown in FIG. 2, the scramble initial value 204 is arranged in the LDPC frame 207 corresponding to the head part of the packet. The value and position of this scramble initial value 204 do not change before and after LDPC encoding. That is, the scramble initial value 203 is added to the head of the data sequence 202 before the LDPC encoding of the encoder 111, and the scramble initial value 204 is positioned at the start in the first LDPC frame 207 even after the LDPC encoding. doing. Therefore, the receiving side wireless communication apparatus can specify the scramble initial value without performing the decoding process.

  In the embodiment of the present invention, LDPC is used for the error correction code. However, as long as the scramble initial value 204 can be extracted without decoding, it is not excluded to use other encoding methods.

  Next, the receiving unit 102 will be described. FIG. 3 shows the receiving unit 102 of FIG. 1 and its peripheral configuration.

  As shown in FIG. 3, the A / D converter 120 samples an electric signal (analog signal) of a received packet at a sampling frequency, and quantizes the amplitude. Thereby, an analog signal is converted into a digital signal. As the A / D converter system, there are a flash type and a pipeline type, but other types may be used.

  The demapping unit 121 converts each bit of the digital signal output from the A / D converter 120 into a log likelihood ratio (LLR) of probability of being “1” or “0”. Hereinafter, the log likelihood ratio is referred to as likelihood information. The likelihood information is a soft value indicating which one of the probability that the value of each bit of the received digital signal is “1” and the probability of “0” is higher from the sign and amplitude of the digital signal. . For example, when the amplitude is positive and the amplitude is large, the probability that the data is “1” is high, and when the amplitude is negative and the amplitude is large, the probability that the data is “0” is high.

  Although the log likelihood ratio is used in the embodiment of the present invention, it is not excluded to use a likelihood other than the log likelihood ratio as long as it represents data reliability information.

  A signal propagated by wireless communication is distorted due to fading in the propagation path or noise in the wireless communication device. The demapping unit 121 calculates likelihood information in consideration of the influence of signal distortion. Each time the demapping unit 121 receives a packet, the demapping unit 121 can calculate likelihood information about the packet.

  The likelihood descrambling unit 122 performs processing (descrambling processing) for converting the likelihood information output from the demapping unit 121 into an unscrambled bit sequence.

  FIG. 4 shows a detailed configuration of the likelihood descrambling unit. As shown in FIG. 4, the likelihood descrambling unit 122 includes a seed detection unit 301, a scramble unit 302, an encoder 303, and a code conversion unit 304.

  The seed detection unit 301 converts the soft likelihood information output from the demapping unit 121 into a bit string having a binary value of “0” or “1” by hard decision. For example, if the sign of likelihood information is negative, it is converted to “0”, and if the sign of likelihood information is positive, it is converted to “1”. The seed detection unit 301 detects a scramble initial value from a predetermined area at the beginning of the bit string. When the number of bits of the scramble initial value is 7 bits, the value of the first 7 bits of the bit string is detected as the scramble initial value.

  The scrambler 302 generates a scramble code by scrambling a 0-bit sequence (followed by 0 bits for the packet length) using the scramble initial value as a scramble seed value. A bit of 0 corresponds to a bit having a first value as an example, and a bit of 1 corresponds to a bit having a second value as an example. This definition may be reversed. As shown in FIG. 5, the scramble unit includes a plurality of flip-flops connected in series.

  In wireless communication, transmission data is generally scrambled to smooth the frequency spectrum of the transmission signal, avoid spike-like spectrum, and reduce the PAPR (Peak to Average Power Ratio) of the time waveform of the transmission signal. Is.

  The configuration of the scrambler (shift register connection) is defined by a generator polynomial S (x) (generator polynomial). In FIG. 5, seven flip-flops are connected in series. Then, the output x_4 of the fourth flip-flop counted from the input side and the output x_7 of the seventh (output terminal) flip-flop are supplied to the EX-OR circuit. In this case, the generator polynomial S (x) is S (x) = x_7 + x_4 + 1.

  The scramble initial value is a set value in the initial state of the seven flip-flops. The scramble initial value is a bit pattern having the same number of bits as the number of flip-flops, excluding a bit string in which all bits are “0”. A scramble code can be obtained by scrambling a bit string to be scrambled based on a scramble initial value and a generator polynomial.

  Even in the scramble part related to the same generator polynomial, the scramble code obtained from the same bit sequence to be scrambled is different if the scramble initial value is different. The scramble code has periodicity, and the period changes according to the number of stages of the shift register (number of flip-flops).

  The encoder 303 performs LDPC encoding on the bit string output from the scrambler 302 (that is, a scrambled 0-bit sequence). The coding rate used in the LDPC coding needs to be the same as the coding rate used in the LDPC coding at the time of transmitting data related to the received packet.

  The bit string output from the encoder 303 is used when descrambling the likelihood information input to the likelihood descrambling unit. This bit string is called a likelihood conversion bit string.

  The code conversion unit 304 descrambles the likelihood information related to the received packet data output from the demapping unit 121 using the likelihood conversion bit string. FIG. 6 illustrates processing in the code conversion unit of the likelihood descrambling unit. Hereinafter, description will be given with reference to FIG.

  The likelihood information 401 output from the demapping unit 121 is input to the code conversion unit 304. The code conversion unit 304 descrambles the likelihood information 401 by converting the likelihood information 401 using the likelihood conversion bit string 402 output from the encoder 303. The conversion process in the code conversion unit 304 is executed as follows.

  When the bit of the likelihood conversion bit string 402 is “0”, the corresponding bit of the likelihood information 401 is not converted. When the bit of the likelihood conversion bit string 402 is “1”, it differs depending on whether the corresponding bit of the likelihood information 401 is a bit representing a code or a bit related to an amplitude. If it is a bit representing a sign, the bit (sign) is inverted, and if it is a bit related to amplitude, the bit is not inverted. Here, sign inversion means that in the case of a positive sign (in the case of a bit indicating positive), it is converted into a negative sign (a bit representing negative), and in the case of a negative sign, it is converted into a positive sign. means. An image of the conversion is shown in FIG. FIG. 7 shows likelihood information corresponding to one bit of the packet data and a corresponding portion of the likelihood conversion bit string. Since the value of the bit of the likelihood conversion bit string corresponding to the sign bit of the likelihood information is 1, the sign bit of the likelihood information is inverted from 1 to 0. The bit related to the amplitude is not converted regardless of the bit value of the likelihood conversion bit string.

  The likelihood information 403 output from the code conversion unit 304 is free from the influence of scrambling performed on the transmission side. The descrambled likelihood information 403 is transferred to the field determination unit 123.

  The field determination unit 123 determines whether or not the descrambled likelihood information is an object of likelihood combining calculation. The likelihood combining operation is a process of combining two or more likelihoods to obtain one likelihood. Details of processing performed by the field determination unit 123 will be described later.

  The storage unit 124 is a storage area for storing likelihood information (descrambled likelihood information) regarding one or more packets.

  The storage unit 124 includes, for example, a nonvolatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, and an optical disk, or a register, a volatile storage device such as an SRAM, a DRAM, or a combination thereof. .

  FIG. 8 shows a flow of processing relating to storage of likelihood information, likelihood combining calculation, and decoding. Below, it demonstrates, referring FIG.

  In step S501, the field determination unit 123 confirms whether or not likelihood information obtained from packet data received in the past (hereinafter referred to as past likelihood information) is stored in the storage unit 124, and processing is performed according to the result. Branch. If no past likelihood information is stored in the storage unit 124, the process proceeds to step S502. If at least one piece of past likelihood information is stored in the storage unit 124, the process proceeds to step S504.

  In step S502, the field determination unit 123 stores the descrambled likelihood information (current likelihood information) obtained from the currently received packet in the storage unit 124. After execution of step S502, the field determination unit 123 instructs the decoder 126 to perform decoding using the current likelihood information in step S503. Details of the decoder 126 will be described later.

  In step S <b> 504, the field determination unit 123 compares the current likelihood information with past likelihood information stored in the storage unit 124. When two or more pieces of past likelihood information are stored in the storage unit 124, the past likelihood information is compared with each piece of likelihood information.

  For example, the comparison is performed based on the similarity between the past likelihood information and the current likelihood information. The similarity of likelihood information can be used to determine whether the packet for which the current likelihood information is obtained is a retransmission packet of the packet for which the past likelihood information is obtained. This is because the similarity between these pieces of likelihood information is assumed to be high because the data transmitted in the retransmission packet is the same as the original packet (the amplitude values of the likelihood information are different, but the signs are the same). Or tend to be nearly the same).

  Normally, even the data in the relationship between the original packet and the retransmission packet may have different scramble initial values at the time of transmission, and the likelihood information may not be similar to each other. However, in the embodiment of the present invention, the likelihood descrambling unit 122 corrects the difference in the bit string due to the difference in the initial scramble value at the time of transmission, so the current likelihood information and the past likelihood information Can be determined whether or not the same data has been retransmitted.

  As a method for examining the similarity between two pieces of likelihood information, for example, a method for calculating a cross-correlation between two pieces of likelihood information can be used. However, an index other than cross-correlation may be used, and the method is not particularly limited.

  In step S505, based on the comparison result in step S504, the field determination unit 123 determines whether or not to perform a likelihood combining operation on the past likelihood information and the current likelihood information. As an example, when cross-correlation is used as an index related to the similarity of likelihood information, if the value of cross-correlation (similarity) with the current likelihood information exceeds a certain threshold value, the two are similar. It is determined that the past likelihood information is to be the target of the synthesis operation. If the value of the cross-correlation is smaller than the threshold value, it is determined that the two are not similar, and it is determined not to perform the likelihood combining calculation on the past likelihood information.

  If multiple pieces of past likelihood information with a cross-correlation value with the current likelihood information equal to or greater than a certain threshold are found, the past likelihood information with the maximum cross-correlation value is synthesized. It can also be selected as the target of calculation. Alternatively, past likelihood information that maximizes the value of the cross-correlation with the current likelihood information regardless of the threshold value may be the target of the synthesis operation.

  If it is determined in step S505 that the likelihood combining operation is to be performed, the process proceeds to step S506, and if it is determined not to perform the likelihood combining operation, the process proceeds to step S502. In step S502, the current likelihood information is stored in the storage unit 124. When there is no free area in the storage unit 124, the past likelihood information may be overwritten with the current likelihood information. In subsequent step S503, the field determination unit 123 instructs the decoder 126 to perform decoding using the current likelihood information.

  In step S <b> 506, the field determination unit 123 issues a command to the likelihood combining unit 125 for combining and calculating the past likelihood information stored in the storage unit 124 and the current likelihood information. Details of processing of likelihood combining calculation in the likelihood combining unit 125 will be described later.

  In step S507, likelihood combining section 125 (or field determination section 123) stores new likelihood information obtained by the combining operation in storage section 124.

  In step S508, the field determination unit 123 (or likelihood combining unit 125) instructs the decoder 126 to perform decoding using the new likelihood information obtained by the combining operation.

  Hereinafter, the likelihood combining calculation process performed by the likelihood combining unit 125 performed in step S506 will be described. If the likelihood information obtained from the data related to the original packet and the likelihood information obtained from the data related to the retransmission packet are corrected for differences in the bit string due to the difference in the initial scramble value at the time of transmission Should ideally be equal.

  However, due to the effects of noise such as thermal noise, multiple wave propagation (multipath) due to diffraction, reflection and refraction, interference and fading in the propagation path, the likelihood information of the original packet and the retransmitted packet is usually not the same Absent. These effects often appear in the form of random distortion to the amplitude of the likelihood information. Therefore, the likelihood synthesizer 125 calculates the likelihood information of the original packet and the likelihood information of the retransmission packet to obtain new likelihood information.

ここで、Ｌ_ｇは新たな尤度情報、Ｍは演算対象とする尤度情報の数であり、Ｌ_１は１つめの尤度情報、Ｌ_２は２つめの尤度情報、Ｌ_ＭはＭ個めの尤度情報に対応する。ｃ_１、ｃ_２、・・・、ｃ_Ｍは、尤度情報の重みづけ定数である。Ｎは尤度情報のビット数であり、式（１）を用いる場合には、Ｎ個めのビットまで、尤度情報のそれぞれのビットｉについて線形演算を行う。 There are various methods for combining likelihood information. As an example, there is a method of performing a linear operation such as the following equation (1) for a plurality of pieces of likelihood information.

Here, L _g is new likelihood information, M is the number of likelihood information to be calculated, L ₁ is first likelihood information, L ₂ is second likelihood information, and L _M is M Corresponds to individual likelihood information. c ₁ , c ₂ ,..., c _M are weighting constants of likelihood information. N is the number of bits of likelihood information, and when equation (1) is used, linear calculation is performed for each bit i of the likelihood information up to the Nth bit.

In this example, since linear calculation is performed using the two pieces of likelihood information of the likelihood information of the original packet and the likelihood information of the retransmission packet, M = 2, and Equation (1) is expressed by the following equation ( It can be expressed as 2).

  The likelihood information stored in the storage unit 124 in step S507 may be treated as past likelihood information in step S501 and may be a target of the synthesis operation. In other words, even if error correction is performed using the likelihood information obtained by the linear calculation of Expression (2) using the likelihood information of the retransmission packet, the bit error may not be completely removed. In such a case, the packet is retransmitted again, and the likelihood information of the retransmitted packet is combined with the likelihood information stored in the storage unit 124 in step S507. Even if decoding is performed using the newly obtained likelihood information, if bit errors still remain, the same processing may be repeated and the likelihood combining operation performed three times or more.

  FIG. 9 is a diagram for explaining fields to be subjected to likelihood combining calculation in a packet format used in a wireless LAN. In a packet format used in a wireless LAN, there may be a field whose value changes between initial transmission and retransmission. For this reason, the likelihood synthesis unit 125 needs to determine whether or not each field is to be a synthesis calculation target.

  The packet format 801 is a format example of a physical layer packet. In order from the beginning of the packet, a preamble, a header, and a payload necessary for physical layer control are arranged. (The preamble of the data format 801 and the header may be collectively referred to as a preamble.) Of these, it is performed on a coded payload by an arbitrary error correction code on the transmission side. Arbitrary error correction codes used here include LDPC, BCC, turbo code, and the like.

  The frame format 802 is a format of a PSDU (Physical Layer Data Unit) frame of the IEEE 802.11 standard in the data link layer. In order from the top, a service field including a scramble initial value, a MAC header, a frame body which is a data body, and an FCS (Frame Check Sequence) are arranged. The FCS stores a checksum code used for bit error detection of a packet on the receiving side. Examples of checksum codes include CRC (Cyclic Redundancy Check).

  The frame format 803 is a format of an LDPC encoded frame.

  In order to obtain the effect of reducing the bit error rate in the likelihood combining unit 125, it is necessary to perform likelihood combining calculation while avoiding a field whose value changes between the original packet and the retransmission packet.

  For example, since the service field in the PSDU frame 802 includes a scramble initial value, there is a possibility that the value changes between the previous data transmission and the same data retransmission.

  The MAC header includes a frame control field indicating an attribute indicating whether or not a received packet is a retransmission. In the case of a retransmission packet, the value is “1”, and in the first transmission, the value is “0”. Therefore, it can be said that the MAC header is also a field whose value changes.

  The FCS stores a CRC calculated using the MAC header and the frame body. When the value of the MAC header changes, the value of the FCS changes accordingly.

  As described above, it is necessary to exclude the bit string related to the service field, the MAC header, and the FCS from the targets of the synthesis operation. When excluding the service field, MAC header, and FCS, only the bit string corresponding to the frame body field can be used for the composition operation.

  In the actual processing, since the LDPC encoded frames 1, 2,..., M shown in the format 803 in FIG. 9 are input to the likelihood combining unit 125, the frame body field in the LDPC frame. It is necessary to extract the part corresponding to.

  When the PSDU frame 802 is LDPC-encoded, the PSDU frame 802 is divided as an information part for each fixed number of bits, and a parity part is attached to each divided information part. In wireless communication, after the LDPC frame length is determined, a code rate is designated on the transmission side, and the lengths of the information part and the parity part are determined.

  For example, when the frame length is 1944 bytes and the coding rate is 2/3, the length of the information part is 1296 bytes and the length of the parity part is 648 bytes. If the coding rate changes between the original packet and the retransmission packet, the length and value of the parity part may also change. Therefore, the parity part of the LDPC frame is excluded from the synthesis operation in the likelihood synthesis unit 125.

  Thus, considering the packet format and field properties used in the wireless LAN, the likelihood combining unit 125 corresponds to the frame body field that is a predetermined region of the PSDU frame in the information portion of the LDPC frame. The bit string related to is the target of the synthesis operation.

  The decoder 126 performs a decoding process using the likelihood information transferred from the field determination unit 123 or the likelihood synthesis unit 125. The decoder 126 decodes the LDPC encoded data into a frame format 802 which is a PSDU frame.

  The access control unit 127 refers to the CRC of the data decoded by the decoder 126 and confirms the presence or absence of a bit error. Subsequent processing differs depending on whether or not a bit error is detected in the access control unit 127.

  The host interface 128 provides means for transmitting and receiving electrical signals between the wireless communication device 1 and the host system 3. Examples of the host interface 128 include PCI Express, USB, UART, SPI, and SDIO, but an interface based on other standards may be used.

  FIG. 10 shows a processing flow of the access control unit 127. Below, it demonstrates along FIG.

  In step S601, the CRC is referred to and it is confirmed whether or not there is a bit error in the decoded data. If there is no bit error, the process proceeds to step S602, and if there is a bit error, the process proceeds to step S604.

  In step S602, the wireless communication device 1 on the reception side transmits an acknowledgment (ACK) to the wireless communication device on the transmission side. In the next step S603, the decrypted data is transferred to the host interface 128. The data transferred to the host interface 128 is further transferred to the host system 3 by a predetermined protocol. Step S602 and step S603 may be performed simultaneously or the order may be changed.

  In step S604, processing for discarding decoded data including bit errors is performed. You may perform the process which transmits a negative response (Negative Acknowledge: NACK) to the radio | wireless communication apparatus of a transmission side.

  If the wireless communication device on the transmission side has not received an ACK even after a certain period of time has elapsed, or if it has received a NACK, it retransmits a packet related to the same data. Here, the retransmitted packet corresponds to a retransmission packet. Note that a retransmission packet is not always a packet in which data relating to a packet at the time of initial transmission is retransmitted for the first time. For example, if the packet that has been checked for the presence or absence of bit errors in step S601 is the retransmission packet of the packet at the first transmission, the packet that is retransmitted here is the packet that is retransmitted the second time. .

  Until no CRC error is detected in step S601, the process of retransmission, likelihood combining, and decoding of packets related to the same data may be repeated. A limit may be placed on the number of retransmissions of packets related to the same data, and the packet retransmission may be aborted when the number of retransmissions reaches a threshold value. When the packets related to the same data are retransmitted and the likelihood combining operation is repeated, the effect of bit error removal can be enhanced. Specifically, it is possible to cancel distortion that appears randomly in the amplitude of the likelihood information due to noise or the like. For this reason, if packet retransmission, combining operation, and decoding are repeatedly executed, it is expected that no CRC error will be detected and bit errors will be eliminated in step S601 in some trials.

  In the present embodiment, an LDPC code is used, but another block code such as a Reed-Solomon code may be used.

  As described above, according to the embodiment of the present invention, by detecting the scramble initial value from the predetermined region (head region) of the likelihood information of the packet data, and descrambling the likelihood information using the detected scramble initial value, Likelihood information in which the difference in the initial scramble value is corrected is calculated. By using this likelihood information and combining with other likelihood information and subsequent decoding, it is possible to reduce the number of times the decoding process is performed and to significantly reduce the processing time. In addition, since the required circuit scale can be reduced, it contributes to lower hardware costs and lower power consumption.

  When a convolutional code or the like is used as an error correction code, a scramble initial value cannot be extracted unless decoding processing is performed once. For this reason, it is necessary to perform a descrambling process after the decoding process. On the other hand, in this embodiment, LDPC which is a block code is used as an error correction code, and according to this, since the region where the scramble initial value exists is known in the likelihood information before decoding, A scramble initial value can be detected from this region. Therefore, decoding for extracting the scramble initial value is unnecessary, and the processing time can be greatly reduced.

(Second Embodiment)
In the wireless communication apparatus according to the second embodiment, the decoder repeatedly performs the decoding process on the likelihood information, thereby repeatedly updating the likelihood information and increasing the reliability of the likelihood information. Decoding is performed using likelihood information. The LDPC has a function of iterative decoding processing, and this embodiment uses iterative decoding provided in the LDPC. When a bit error is detected, the reliability of the likelihood information is further increased by restarting the decoding process repeatedly for this likelihood information until the retransmission packet is received from the transmission side. The degree information is combined with the likelihood information of the retransmission packet. Thereby, the possibility of reducing bit errors can be further increased. The functions of the antenna, the RF unit, and the transmission unit of the baseband unit of the wireless communication device according to the second embodiment are the same as those of the antenna 10, the RF unit 50, and the transmission unit 101 of the wireless communication device according to the first embodiment, respectively. It is. Below, it demonstrates centering on the part which has a difference with the radio | wireless communication apparatus which concerns on 1st Embodiment.

  FIG. 11 is a block diagram illustrating an example of a reception unit and its peripheral configuration of the wireless communication apparatus according to the second embodiment.

  The functions of the A / D converter 130, the demapping unit 131, and the likelihood descrambling unit 132 are the same as those of the A / D converter 120, the demapping unit 121, and the likelihood descrambling unit 122 according to the first embodiment, respectively. Therefore, when a packet at the time of initial transmission is received, likelihood descrambling section 132 generates likelihood information in which the packet is descrambled.

  In the second embodiment, the decoder 136 then repeatedly performs decoding using the descrambled likelihood information. The reliability of the likelihood information can be increased according to the number of times decoding is repeated. After performing iterative decoding, the decoder 136 stores the likelihood information with improved reliability (likelihood information updated repeatedly) in the storage unit 135 and checks whether there is a bit error in the CRC check.

  The number of times the decoder 136 repeats decoding may be two times or three times or more, and is not particularly limited. The number of repetitions of decoding may be changeable. For example, each time a packet is received, the number of times of decoding performed until the bit error is eliminated can be recorded, and the average value, maximum value, etc. of the number of times of decoding can be set to a prescribed number of times of decoding.

  In a wireless LAN, the number of times that decoding can be repeatedly performed on the receiving side is limited by time, such as until a negative acknowledgment (NACK) is transmitted to the transmitting side, or until an acknowledgment (ACK) reception on the transmitting side times out. There may be. In this case, decoding may be repeated within that time.

  If a bit error remains as a result of the CRC check after the decoding process is performed by the decoder 136 a predetermined number of times or within the time limit, the wireless communication apparatus according to the second embodiment Data to be discarded or a negative acknowledgment (NACK) is transmitted to the wireless communication apparatus on the transmission side.

  When the wireless communication device on the transmission side does not receive an acknowledgment (ACK) within a certain period after packet transmission or receives a negative acknowledgment (NACK), it retransmits a packet related to the same data.

  At this time, since the wireless communication apparatus according to the second embodiment has a time delay until the retransmitted packet is received from the transmission side, the decoder 136 uses the likelihood information stored in the storage unit 135. Used to resume the iterative decoding process. Then, likelihood information obtained from the retransmit packet after descrambling and likelihood information obtained by repetitive decoding after restart are combined and calculated by likelihood combining section 134. The combined likelihood information is repeatedly decoded for a specified number of times or within a limited time range to improve the reliability of the likelihood information, and the likelihood information is decoded and a CRC check is performed.

  As described above, according to the present embodiment, the reception-side wireless communication apparatus continues the decoding process repeatedly after transmitting a NACK or discarding a packet until receiving a retransmission packet. It is possible to further enhance the bit error reduction effect of the retransmission packet data.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. Further, for example, a configuration in which some components are deleted from all the components shown in each embodiment is also conceivable. Furthermore, you may combine suitably the component described in different embodiment.

DESCRIPTION OF SYMBOLS 1 Wireless communication apparatus 3 Host system 10 Antenna 50 RF part 51 Local oscillator 52 56 Mixer 53 Low noise amplifier 54 Selector 55 RF amplifier 100 Baseband part 101 Transmission part 102 Receiving part 110 Scramble part 111 Encoder 112 Mapping part 113 D / A Converter 120 130 A / D converter 121 131 Demapping unit 122 132 Likelihood descrambling unit 123 133 Field determination unit 124 135 Storage unit 125 134 Likelihood synthesis unit 126 136 Decoder 127 137 Access control unit 128 138 Host interface 201 Data 202 205 208 Data sequence 203 Frame 204 Scramble initial value 206 209 Parity section 207 210 LDPC frame 301 Seed detection section 302 Scramble section 3 03 Encoder 304 Code conversion unit 401 403 Likelihood information 402 Likelihood conversion bit string 801 802 803 Format

Claims (11)

The first scramble seed is detected from a predetermined region of the first likelihood information which is the likelihood information of the first packet data, and the first likelihood information is descrambled by using the first scramble seed. A likelihood descrambling section for generating likelihood information;
A likelihood combining unit that combines the second likelihood information with the third likelihood information to generate fourth likelihood information;
A wireless communication device comprising: a decoder that decodes the fourth likelihood information. The likelihood descrambling unit generates a scramble code by scrambling a bit sequence of bits of a first value using the first scramble seed, and the scramble code is generated in the same encoding method as the first packet data. The wireless communication apparatus according to claim 1, wherein an encoded bit string is generated by encoding, and the first likelihood information is descrambled by the encoded bit string. The radio communication apparatus according to claim 2, wherein the likelihood descrambling unit descrambles the first likelihood information by inverting a code bit corresponding to a bit of a second value in the encoded bit string. The radio communication apparatus according to any one of claims 1 to 3, wherein the predetermined area is a predetermined number of bits at the beginning of the first likelihood information. The likelihood descrambling unit detects a second scramble seed from a predetermined region of fifth likelihood information that is likelihood information of second packet data, and uses the second scramble seed to generate the fifth likelihood information. Generating the third likelihood information by descrambling
The radio communication apparatus according to any one of claims 1 to 4, wherein the first packet data is retransmission packet data of the second packet data. The radio communication apparatus according to any one of claims 1 to 5, wherein only the portion corresponding to a predetermined region of the first packet data in the second likelihood information is combined with the third likelihood information. The similarity between the first likelihood information and the third likelihood information is evaluated, and when the first likelihood information and the third likelihood information are similar, the first likelihood information and the third likelihood information The wireless communication apparatus according to any one of claims 1 to 6, wherein the likelihood information is combined and the first likelihood information and the third likelihood information are not combined if they are not similar. When a bit error is detected in the decoded data of the fourth likelihood information, the second likelihood information or the fourth likelihood information is repeatedly decoded until retransmission packet data of the first packet data is received. By updating the second likelihood information or the fourth likelihood information,
The likelihood descrambling unit detects a third scramble seed from a predetermined region of sixth likelihood information that is likelihood information of the retransmission packet data, and uses the third scramble seed to generate the sixth likelihood information. 7th likelihood information is generated by descrambling
The said likelihood synthetic | combination part synthesize | combines the said updated 2nd likelihood information or the said updated 4th likelihood information with the said 7th likelihood information. Wireless communication device. The radio communication apparatus according to any one of claims 1 to 8, wherein an encoding method of the first packet data is LDPC. The wireless communication apparatus according to any one of claims 1 to 9, wherein the first likelihood information and the third likelihood information are log likelihood ratios. The first scramble seed is detected from a predetermined region of the first likelihood information which is the likelihood information of the first packet data, and the first likelihood information is descrambled by using the first scramble seed. Generate likelihood information,
Combining the second likelihood information with the third likelihood information to generate fourth likelihood information;
A wireless communication method for decoding the fourth likelihood information.

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