JP2008270863A - Radio receiving apparatus, radio transmitting apparatus, and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio receiver capable of preventing a processing delay of a decoding process and performing high performance iterative decoding.
A radio receiving apparatus 1 uses a decoding unit 14 that decodes packet data for each symbol, a buffering unit 28 that stores decoded data, and iterative decoding using the decoded data decoded by the decoding unit 14. Which decoding data is to be acquired among the iterative decoding unit 18 that performs the decoding, the decoded data sequentially stored in the buffering unit, and the decoded data that is sequentially generated by the iterative decoding unit 18 using the decoded data Packet data is configured using decoded data sequentially acquired from the iterative decoding unit 18 or the buffering unit 28 via the switching unit 32, and whether or not a transmission error has occurred in the packet data. The MAC unit 24 to be determined and a transmission unit 26 that transmits a confirmation response when the MAC unit 24 determines that a transmission error has not occurred.
[Selection] Figure 1

Description

  The present invention relates to a wireless reception device and a wireless transmission device using a wireless LAN, and more particularly to a technique for reducing a packet error rate.

  In recent years, wireless LANs conforming to the IEEE 802.11 standard have been actively used for computer communication and the like. According to this standard, when communication is successful, the wireless reception device receives an acknowledgment (Ack :) at a timing (hereinafter referred to as “SIFS timing”) when a predetermined time (SIFS: Short Interframe Space, 16 μsec) has elapsed since completion of reception. Acknowledgment) signal is required to be returned.

  Data transmitted and received in the wireless LAN is composed of a predetermined fixed preamble portion and a signal portion. The preamble part has a time length of 16 μsec and is composed of STS (Short Training Symbol) and LTS (Long Training Symbol). The signal part following the preamble part is composed of SIGNAL, MAC header, and FCS (Frame Check Sequence). SIGNAL is a symbol indicating a modulation scheme, a coding rate, and a data length. The MAC header is composed of frame control, duration, and address of the wireless receiver.

  When a signal addressed to itself is transmitted from the wireless transmission device, the wireless reception device shifts to an idle state without returning an Ack signal if an error occurs as a result of error detection by FCS, and the packet is Wait for it to be resent. If no error has occurred, the wireless reception device returns an Ack signal to the wireless transmission device. According to the standard, the return timing of the Ack signal is determined to be the SIFS timing.

  The wireless transmission device that has received the Ack signal returned from the wireless reception device performs synchronization and channel estimation using the preamble portion of the Ack signal, and then determines a signal after the preamble. If there is no error as a result of error detection using FCS, the wireless transmission device transitions to the idle state without retransmission. When an error is detected, or when reception of the Ack signal cannot be confirmed after the SIFS timing has elapsed, the wireless transmission device retransmits the target packet.

  IEEE 802.11n, which is a high-speed wireless LAN standard, employs MIMO (Multi-Input Multi-Output) transmission technology. The MIMO transmission technique is a technique for simultaneously transmitting and receiving a plurality of transmission streams using a plurality of transmission and reception antennas. As one technique for improving the reception quality of a MIMO transmission system, the application of iterative decoding processing in which decoding processing of a received signal is repeated has been studied. By performing the iterative decoding process an appropriate number of times, the reception quality can be improved.

  In order to sufficiently obtain the effect of the iterative decoding process, it is necessary to increase the number of times of iterative decoding. However, if the number of iterations is increased, the processing time also increases, so that the error detection timing for detecting whether or not the communication is successful is also delayed. When the error detection timing is delayed from the SIFS timing, consistency with the standard defined by IEEE cannot be maintained.

  Non-Patent Document 1 discloses a method of returning an Ack signal in consideration of a delay due to iterative decoding. In the reply method described in Non-Patent Document 1, the wireless reception device generates an Ack signal before the iterative decoding process is completed. Then, even if the error detection by FCS is not completed, the wireless reception device starts transmission of the preamble portion of the Ack signal at the SIFS timing. The wireless reception device completes the iterative decoding process during transmission of the preample part of the Ack signal, and performs error detection by FCS. When no error due to FCS is detected, the wireless reception device continues to transmit the Ack signal as it is, and when an error is detected, the receiving station address in the Ack signal is changed to that addressed to itself. As a result, transmission of an Ack signal is started at SIFS timing to maintain consistency with the standard, and a situation in which an Ack signal is returned despite an error has occurred and data is not retransmitted is prevented.

Patent Document 1 discloses another method for enabling an Ack signal to be returned at SIFS timing. Patent Document 1 considers a delay in iterative decoding, and adds dummy data irrelevant to the information signal after the information signal. Since the SIFS timing is calculated from the time point when the data reception is completed, by adding dummy data, the wireless reception device is longer by the time for receiving the dummy data and can secure the time for the iterative decoding process of the information signal.
JP 2006-197045 A "A Modified Medium Access Control Algorithm for Systems with Iterative Decoding", Inkyu Lee et al., IEEE Trans. On Wireless Communications, vol.5, no.2, Feb. 2006

  However, since the technique described in Non-Patent Document 1 described above transmits the preamble part of the Ack signal even when an error occurs, the wireless channel shared with other terminals is wasted, Transmission efficiency is reduced. In addition, there is a problem that power consumption increases.

  Further, in the transmission system described in Patent Document 1 described above, it is necessary for the wireless reception device to grasp that dummy data is added. In other words, the wireless transmission device needs to show that the wireless reception device is different from the standard specification in some way.

  The wireless LAN standard IEEE802.11a stipulates that an optimum modulation scheme and coding rate can be selected according to the state of the transmission path. Information such as modulation scheme and coding rate is called MCS (Modulation and Coding Scheme). The wireless reception device decodes the information data according to the MCS. MCS is transmitted by a symbol called SIGNAL transmitted prior to information data. SIGNAL is encoded with a known and fixed modulation scheme (BPSK) and code rate. The wireless reception device decodes information data following SIGNAL based on the modulation scheme and coding rate described in MCS.

  When the packet length of only the information data not including dummy data is described in the SIGNAL according to the standard, and the dummy data is added to the information data and transmitted, the wireless receiver in accordance with the standard completes the reception of the dummy data. There is a possibility that the transmission data radio wave and the reception data radio wave interfere with each other in the air because transmission has been started before. In the first place, since the access point side has not shifted to the reception mode, there may be a situation where communication fails.

  This is because the signal level at the wireless reception device at the moment when the dummy data is transmitted is lower than the specified level value (−62 dBm) in carrier sense performed by the wireless reception device before transmission, and the SIGNAL modulation method. This occurs because the packet length described in SIGNAL can be accurately grasped, for example, when it is higher than the reception sensitivity (−82 dBm) of a certain BPSK. That is, transmission is permitted after the timing lower than the carrier sense level and after adding the random back-off time to the DIFS (Distributed Coordination Function) time (= 34 μsec) to the packet length described in SIGNAL. The standard wireless receiver starts transmission. Therefore, the time length of the dummy data to be added needs to be 34 μsec or less.

  The larger the modulation multi-level number and the coding rate, the larger the number of bits per symbol, so that the processing delay increases and it becomes difficult to return the Ack signal by the SIFS timing. Further, a process of adding padding bits after the information data is performed so that the total number of bits transmitted in the physical layer is a multiple of the number of bits per symbol. The time until the Ack signal is returned also varies depending on the number of padding bits. That is, when the number of bits of data to be reported per packet is Ni and the number of bits per symbol is Ns, the number of padding bits Np = Ns−Modulo (Ni / Ns) (Modulo (Ni / Ns) ≠ 0 , Modulo (Ni / Ns) = 0, Np = 0), and the time margin that can be obtained by padding bits that do not require decoding processing decreases as Np decreases. Therefore, the time until the return of the Ack signal is determined by the MCS and the information data length per packet.

  Patent Document 1 does not have a detailed description of a method for ensuring mutual connectivity between a wireless transmission device and a wireless reception device. In order to ensure the interoperability, for example, at the start of communication, a signal indicating that communication using dummy data is performed is transmitted, and the wireless reception device determines whether communication using dummy data is possible. A method for judging the above can be considered. However, this confirmation method is performed in a layer higher than the physical layer in the OSI (Open Systems Interconnection) reference model, whereas information signal reception and iterative decoding are controlled in the physical layer.

  Therefore, the confirmation of the interconnectivity in the upper layer must be fed back to the physical layer for processing. This complicates the device to be mounted, increases the number of man-hours for device verification, and increases the possibility of problems. In addition, there is a problem that the circuit scale of the wireless reception device is increased and the power consumption is increased. Furthermore, by adding dummy data considering delay in iterative decoding, a radio channel is wasted and transmission efficiency is reduced.

  Therefore, an object of the present invention is to provide a wireless reception device and a wireless transmission device capable of preventing a processing delay of decoding processing and performing high-performance iterative decoding.

  A wireless receiver of the present invention includes a packet data receiving unit that receives packet data modulated by a digital modulation method, a decoding unit that decodes the packet data for each symbol, and a decoding data decoded by the decoding unit. A buffering unit for storing; an iterative decoding unit that performs iterative decoding using the decoded data decoded by the decoding unit; decoded data that is decoded by the decoding unit and sequentially accumulated in the buffering unit; Of the decoded data sequentially generated by the iterative decoding unit using the decoded data, a switching unit that switches which decoding data is acquired, and the iterative decoding unit or the buffering via the switching unit The packet data is composed using the decoded data sequentially obtained from the unit, and it is determined whether or not a transmission error has occurred in the packet data That includes a transmission error determination unit, when a transmission error by the transmission error determination unit determines not occurred, the acknowledgment transmitting unit for transmitting the acknowledgment.

  The decoded data obtained by the iterative decoding unit has higher decoding accuracy than the decoded data obtained by the decoding unit, but requires processing time. According to the configuration of the present invention, by switching which of the decoded data obtained by the decoding unit and the decoded data obtained by the iterative decoding unit is acquired by the switching unit, and input to the transmission error determination unit, Processing time required for decoding can be shortened while maintaining high decoding accuracy. As a result, the decoding process can be completed by the SIFS timing, and the Ack signal can be transmitted at a timing according to the standard.

  In the radio reception apparatus of the present invention, the switching unit obtains decoded data corresponding to symbols from the last symbol to a predetermined number of symbols before the final symbol from the buffering unit, and the decoded data corresponding to the remaining symbols is the iteration. Switching may be performed so as to obtain from the decoding unit.

  With this configuration, the decoding process of the received packet data can be completed in time for the SIFS timing determined based on the reception timing of the final symbol. In addition, since iterative decoding can be performed up to a predetermined number of symbols before the final symbol, highly accurate decoding can be performed.

  The wireless reception apparatus of the present invention is configured such that the completion of the iterative decoding process in the iterative decoding unit is delayed from the transmission timing of a predetermined acknowledgment response, and the interruption time in which the decoding process by the decoding unit is interrupted between symbols. A switching timing determination unit may be provided that determines a minimum integer equal to or greater than the value obtained by dividing the predetermined number as the predetermined number.

  With this configuration, it is possible to appropriately determine the timing for switching the acquisition source from which the decoded data is acquired by the switching unit from the iterative decoding unit to the decoding unit.

  In the radio reception apparatus of the present invention, the switching timing determination unit may determine the predetermined number based on the number of padding bits included in the final symbol.

  Since the decoding process can be performed while the padding bits are being received, the length of time during which the decoding process can be performed before the SIFS timing determined by the reception timing of the final symbol differs depending on the number of bits of the padding bits. According to the configuration of the present invention, the switching timing can be appropriately determined based on the number of padding bits.

  In the wireless reception device of the present invention, the switching timing determination unit may have a table storing the number of padding bits associated with the predetermined number, and may determine the predetermined number with reference to the table .

  With this configuration, since the switching timing can be determined with reference to the table, it is not necessary to calculate the switching timing, and processing can be performed quickly with a small circuit scale.

  The wireless communication system of the present invention includes a wireless transmission device that modulates and transmits packet data by a digital modulation method, and the above-described wireless reception device that receives the packet.

  With this configuration, the processing time required for decoding can be shortened while maintaining high decoding accuracy, as with the above-described wireless reception device.

  In the wireless communication system of the present invention, the wireless transmission device may include a packet division unit that divides transmission data into packet data having a length that is an integral multiple of the number of bytes that can be transmitted in one symbol + 1 byte.

  With this configuration, since the number of padding bits included in the final symbol can be increased, the reception time of padding bits can be increased, and decoding processing can be performed during that time.

  In the wireless communication system according to the present invention, the wireless transmission device may include a puncture processing unit that performs puncture processing for thinning out the transmission data, and a puncture processing unit that interposes a final symbol among a plurality of symbols carrying packet data. And a radio signal generation unit that generates a radio signal including the drawn puncture data.

  With this configuration, the wireless reception device that has received the packet data can perform decoding using the puncture data included in the final symbol, so that highly accurate decoding can be performed.

  In the wireless communication system of the present invention, the decoding unit of the wireless reception device may include a depuncture processing unit that performs a depuncture process using puncture data included in a final symbol.

  With this configuration, decoding can be performed using the puncture data included in the final symbol, so that highly accurate decoding can be performed.

  The wireless transmission device of the present invention generates a packet dividing unit that divides transmission data into packet data having an integral multiple of the number of bytes that can be transmitted in one symbol + 1 byte, and a wireless signal that carries the packet data A radio signal generation unit; and a transmission unit that transmits the radio signal.

  With this configuration, since the number of padding bits included in the final symbol can be increased, the reception time of padding bits can be increased, and decoding processing can be performed during that time.

  A wireless transmission device according to another aspect of the present invention includes a puncture processing unit that performs puncturing processing to thin out transmission data, a packet division unit that divides the transmission data into a plurality of packet data, and a plurality of units that carry the packet data A radio signal generation unit that generates a radio signal including puncture data thinned out by the puncture processing unit in a final symbol of the symbols, and a transmission unit that transmits the radio signal.

  With this configuration, the wireless reception device that has received the packet data can perform decoding using the puncture data included in the final symbol, so that highly accurate decoding can be performed.

  The wireless reception method of the present invention includes a step of receiving packet data modulated by a digital modulation method, a step of decoding the packet data for each symbol, a step of storing the decoded data in a buffering unit, Which decoding data is to be acquired among the step of performing iterative decoding using, the decoded data sequentially stored in the buffering unit, and the decoded data sequentially generated by iterative decoding using the decoded data A step of switching, a step of determining whether or not a transmission error has occurred in the packet data by configuring packet data by using the decoded data sequentially obtained while switching in the switching step, and a transmission error has occurred Sending a confirmation response when it is determined that Obtain.

  With this configuration, as with the wireless reception device of the present invention, it is possible to shorten the processing time required for decoding while maintaining high decoding accuracy. Various configurations of the wireless reception device of the present invention can be applied to the wireless reception method of the present invention.

  The wireless transmission method of the present invention includes a step of dividing transmission data into packet data having a length of an integral multiple of the number of bytes that can be transmitted in one symbol + 1 byte, and a step of generating a wireless signal carrying the packet data; And transmitting the radio signal.

  With this configuration, similarly to the wireless transmission device of the present invention, it is possible to lengthen the reception time of padding bits and perform decoding processing during that time.

  A wireless transmission method according to another aspect of the present invention includes a step of performing a puncturing process for thinning out the transmission data, a step of dividing the transmission data into a plurality of packet data, and a plurality of symbols carrying the packet data Generating a radio signal including the puncture data thinned out from the transmission data in the final symbol, and transmitting the radio signal.

  With this configuration, the wireless reception device that has received the packet data can perform decoding using the puncture data included in the final symbol, so that highly accurate decoding can be performed.

  A program of the present invention is a program for receiving packet data modulated by a digital modulation method, the step of receiving the packet data by a computer, the step of decoding the packet data for each symbol, and the decoding Steps of storing data in a buffering unit, steps of performing iterative decoding using decoded data, decoded data sequentially stored in the buffering unit, and iterative decoding using the decoded data are sequentially generated Of the decoded data, the step of switching which decoded data is to be acquired and the packet data is configured using the decoded data sequentially acquired while performing the switching in the switching step, and a transmission error occurs in the packet data. A step of determining whether there is a transmission error There If it is determined that not occurred, and a step of transmitting an acknowledgment.

  With this configuration, as with the wireless reception device of the present invention, it is possible to shorten the processing time required for decoding while maintaining high decoding accuracy. Various configurations of the wireless reception device of the present invention can be applied to the program of the present invention.

  A program according to another aspect of the present invention is a program for modulating packet data by a digital modulation method and transmitting the packet data to a computer, which is an integral multiple of the number of bytes that can be transmitted in one symbol plus one byte. And a step of generating a radio signal carrying the packet data and a step of transmitting the radio signal.

  With this configuration, similarly to the wireless transmission device of the present invention, it is possible to lengthen the reception time of padding bits and perform decoding processing during that time.

  A program according to another aspect of the present invention is a program for modulating packet data by a digital modulation scheme and transmitting the packet data to a computer, performing a puncturing process for thinning transmission data, and transmitting the transmission data to a plurality of Dividing into packet data; generating a radio signal including puncture data thinned out from transmission data in a final symbol of a plurality of symbols carrying packet data; and transmitting the radio signal With.

  With this configuration, the wireless reception device that has received the packet data can perform decoding using the puncture data included in the final symbol, so that highly accurate decoding can be performed.

  According to the present invention, it is possible to apply high-performance iterative decoding while conforming to a standard specification, and to improve reception performance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a block configuration diagram of a wireless reception device 1 according to the first embodiment. As a configuration for receiving and decoding data, the wireless reception device 1 according to the present embodiment has a reception unit 8, a synchronization unit 10, a demodulation unit 12, a decoding unit 14, a packet analysis unit 16, and an iterative unit. The decoding part 18, the MAC part 24, and the transmission part 26 are provided.

  The receiving unit 8 has a function of receiving a wireless signal transmitted from the wireless transmission device. The receiving unit 8 inputs the received radio signal to the synchronization unit 10 via various processing units (not shown). Here, the various processing units include, for example, a processing unit that converts an analog baseband signal into a digital signal.

  The synchronization unit 10 measures the power after AD conversion and performs automatic gain control (AGC) for adjusting the gain of an RF unit (not shown). In addition, the synchronization unit 10 performs frequency synchronization for compensating for a frequency error, and performs time synchronization for adjusting the timing of fast Fourier transform (FFT).

  The demodulation unit 12 performs FFT at a timing determined by the signal from the synchronization unit 10, estimates channel characteristics using a known preamble, and equalizes the data signal according to the estimation result (or stream separation) I do). Here, in the case of MIMO transmission, a method is generally used in which a stream is separated by calculating an inverse matrix when a channel estimation value between antennas is matrixed and performing a matrix operation on a data signal. .

  The decoding unit 14 performs error correction decoding by determining the demodulation result according to the modulation method of the received data. The decoding unit 14 obtains a distance (likelihood) from an ideal signal point (or a threshold value between signal points) determined by a modulation scheme corresponding to MCS obtained by SIGNAL, and performs error correction decoding by maximum likelihood decoding. Do. The SIGNAL signal is transmitted with a known MCS (BPSK, coding rate 1/2). The packet analysis unit 16 obtains the MCS and packet length of the data signal portion.

  The iterative decoding unit 18 cancels interference components and the like from the data decoded by the decoding unit 14 and then performs the decoding process again. The iterative decoding unit 18 includes a canceling unit 20 that cancels interference components, and a decoding unit 22 that performs error correction decoding on the canceled signal in accordance with each modulation scheme.

  The cancel unit 20 performs re-modulation based on the decoding result obtained from the decoding unit 14 and the channel characteristics estimated by the demodulation unit 12, and the other channels that interfere with each stream of the MIMO channel. Generate a replica of the signal. Then, the replica signal of the interference signal is subtracted from the signal subjected to FFT in the demodulator 12. After the process of subtracting the replica signal from the stream obtained by each receiving antenna is performed, the signals that should be the same stream are combined by maximum ratio combining to obtain diversity gain. Subsequently, the decoding unit 22 obtains a distance (likelihood) from an ideal signal point (or a threshold value between signal points) determined by a modulation method corresponding to MCS, and performs error correction decoding again by maximum likelihood decoding. .

  The MAC unit 24 has a function of controlling data transmission. The MAC unit 24 performs error detection based on the FCS of the decoded received data. If no error is detected, the MAC unit 24 generates an Ack signal and transmits the Ack signal at the SIFS timing. The MAC unit 24 passes the Ack signal to the transmission unit 26, and the transmission unit 26 transmits the Ack signal.

  The wireless reception device 1 according to the first embodiment includes the following configuration in order to determine whether or not data can be received without error before the SIFS timing. That is, the wireless reception device 1 includes a buffering unit 28 that stores the output of the decoding unit 14, a read control unit 30 that reads data stored in the buffering unit 28, and an iterative decoding unit as input data to the MAC unit 24. And a switching unit 32 that switches between using the data decoded at 18 and using the data read out by the read control unit 30.

  The switching unit 32 is connected to the switching timing determination unit 34 and switches between the output from the iterative decoding unit 18 and the output from the read control unit 30. The switching timing determination unit 34 is also connected to the read control unit 30 and notifies the read control unit 30 of the switching timing. Accordingly, the read control unit 30 can start reading data from the buffering unit 28 at a timing when the switching unit 32 starts data transmission from the read control unit 30 to the MAC unit 24.

  Next, the timing of switching by the switching unit 32 will be described. The switching unit 32 inputs the output data from the iterative decoding unit 18 to the MAC unit 24 from the start of data reception to several symbols before the final symbol, and reads the read data from the buffering unit 28 for the final several symbols. It switches so that it may input into the part 24. The final number of symbols to be read from the buffering unit 28 is determined based on the MCS and the packet length.

  The processing time required for completing the reception of a packet and completing the decoding of the data signal differs depending on the MCS and the packet length. This is because the data signal is transmitted in units of OFDM symbols. If there is a remainder when the number of bits of data to be transmitted in one packet is divided by the number of bits that can be transmitted per OFDM symbol, a bit called a padding bit is added, which is always a multiple of the number of bits per OFDM symbol. Adjustment is performed so that the number of bits becomes. The more padding bits, the fewer the number of data signal bits that must be decoded included in the final symbol, and the shorter the time required for the decoding process. On the other hand, when data can be received without error, transmission of an Ack signal is started when a predetermined time has elapsed (SIFS) after reception of the packet is completed.

  FIG. 2 is a diagram illustrating the timing at which decoded data is output from the decoding unit 14 and the iterative decoding unit 18. FIG. 2 shows the decoding timing of L-3 to L symbols out of L symbols. As shown in FIG. 2, a certain interruption time D generally occurs between symbols. In the case of IEEE802.11a, a waiting time is generated between symbols for at least the guard interval length.

  The digital signal processing circuit in the wireless reception device 1 is generally configured using one of frequencies that is a multiple of the clock frequency for performing FFT. In this case, the redundant waiting time between symbols further increases in addition to the waiting time of the guard interval length. For example, in the case of MCS15 (64QAM, coding rate 5/6, 2 streams) defined in IEEE802.11n, assuming that the Viterbi decoding unit performs decoding using a 160 MHz clock signal, the total clock per symbol The number is 640 clocks. Of these, the number of clocks required for decoding is 375 clocks, which is the number of bits including puncture bits per symbol, so there is a waiting time of 265 clocks.

  The SIFS timing is determined by the time when the last symbol is received. For example, a time obtained by adding 16 μsec to the time when the last symbol is received is the SIFS timing. In the example shown in FIG. 2, the timing at which the iterative decoding unit 18 completes the iterative decoding is delayed by ΔTi from the SIFS timing. Therefore, if the iteratively decoded signal is transmitted to the MAC unit 24 and it is determined whether or not the MAC unit 24 has correctly received the signal, the Ack reply is not in time for the SIFS timing, and the standard is not consistent. I can't take it.

  The switching unit 32 transmits the decoded data of the decoding unit 14 that has been processed before the iterative decoding unit 18 to the MAC unit 24 for several symbols close to the final symbol so that the Ack signal can be returned at the SIFS timing. To do. The MAC unit 24 uses the data decoded by the decoding unit 14 to determine whether or not there is a transmission error.

  FIG. 3 is a diagram illustrating processing performed by the wireless reception device 1 according to the present embodiment. FIG. 3 shows the decoding timing of L-3 to L symbols out of L symbols as in FIG. As illustrated in FIG. 3, the switching unit 32 selects the L-3 symbol and the L-2 symbol output from the iterative decoding unit 18 and transmits them to the MAC unit 24. The switching unit 32 selects the decoded data output from the decoding unit 14 and transmits the L-1 symbol and the L symbol to the MAC unit 24. That is, the switching unit 32 reads the L-1 symbol and the L symbol output from the decoding unit 14 and buffered in the buffering unit 28, and transmits them to the MAC unit 24. Thereby, the radio | wireless receiver 1 can process to the last L symbol so that SIFS timing may be met.

  The decoded data by the decoding unit 14 is inferior to the decoded data by the iterative decoding unit 18 in error rate characteristics. In order to improve the reception performance of the wireless reception device 1, it is desirable that the MAC unit 24 configures the received packet data by using as much decoded data as possible by the iterative decoding unit 18. The switching timing determination unit 34 determines the number of symbols for reducing the data decoded by the decoding unit 14 as much as possible. Here, the number of symbols read from the decoding unit 14 will be described.

  As shown in FIG. 2, the waiting time between symbols is D, and the time that the output completion of the iterative decoding unit 18 is delayed from the SIFS timing is ΔTi. At this time, the switching timing determination unit 34 determines the number N of symbols to be read from the output of the decoding unit 14 by N = [ΔTi / D] +1 ([X] is the maximum integer not exceeding X). As a result, it is possible to minimize the amount of use of symbols with inferior reception performance, that is, the decoded data of the decoding unit 14.

  Here, since the waiting time D between symbols is determined by MCS, the value of D corresponding to each MCS may be stored in the switching timing determination unit 34. The time ΔTi that the output completion of the decoding unit 22 is delayed from the SIFS timing is determined by the MCS and the number of padding bits Np. Therefore, the number N of symbols acquired from the decoding unit 14 based on the excess time ΔTi when the number of padding bits is changed for each MCS may be stored in the table.

  FIG. 4 is a diagram illustrating an example of a table storing the number N of symbols read from the decoding unit 14. In the table shown in FIG. 4, when MCS is “3” or less, even if iterative decoding is performed on all signals, iterative decoding processing is completed by the SIFS timing, so N = 0 is described. That is, all symbols are read from the iterative decoding unit 18.

  When MCS is “4”, if iterative decoding is performed when the padding bit is “113” or less, the iterative decoding process will not be in time by the SIFS timing, so only the last symbol is read by the read control unit 30. It is shown that it is necessary to output the symbol to the MAC unit 24. Even if MCS is “4”, if the padding bit is “114” or more, there is a time margin due to padding bits that do not require decoding processing, and even if iterative decoding is performed, iterative decoding is performed by the SIFS timing. Since the process is completed, N = 0 is described.

In this way, by storing the table shown in FIG. 4, the switching timing determination unit 34 can easily calculate the number N of switching symbols without performing the calculation N = [ΔTi / D] +1. it can. If tables are similarly created for other modulation schemes, the switching timing can be defined for all MCSs.
Heretofore, the wireless reception device 1 according to the first embodiment has been described.

  The wireless reception device 1 according to the first embodiment inputs the decoded data decoded by the decoding unit 14 having a shorter processing time than the iterative decoding unit 18 to the MAC unit 24 for the last several symbols of the received symbols. The MAC unit 24 can determine whether or not the data has been normally received before the SIFS timing, and can return an Ack signal at the SIFS timing when the data has been normally received.

  In addition, since the wireless reception device 1 according to the first embodiment performs iterative decoding processing before the last several symbols, the reception performance can be improved.

  In the first embodiment, an example has been described in which the switching timing for switching between decoding data acquired by the decoding unit 14 and decoding data acquired by the iterative decoding unit 18 is controlled in symbol units. It is also possible to switch with. As a result, more decoded data after iterative decoding with high reception performance can be acquired, leading to improvement in reception performance. In this case, it is necessary to strictly control the switching timing by the switching unit 32. For example, after the number N of switching symbols is determined, the switching timing is further determined according to the number of padding bits. As the number of padding bits increases, the switching timing can be delayed and the time for outputting the signal after iterative decoding can be lengthened.

(Second Embodiment)
FIG. 5 is a diagram illustrating a configuration of the wireless reception device 2 according to the second embodiment. The wireless reception device 2 of the second embodiment has the same basic configuration as the wireless reception device 1 of the first embodiment described above. In the wireless reception device 2 according to the second embodiment, the output of the decoding unit 14 is not input to the buffering unit 28, but the output of the demodulation unit 12 is input to the buffering unit 28. In the second embodiment, a hard decision unit 36, a hard decision cancellation unit 38, and a hard decision decoding unit 40 are provided between the demodulation unit 12 and the buffering unit 28, and are output from the demodulation unit 12. Data is decoded and stored in the buffering unit 28. Hereinafter, these configurations will be described.

  The hard decision unit 36 makes a hard decision on the output data from the demodulation unit 12 and determines “1” or “0” of the received data. The hard decision cancel unit 38 performs re-modulation based on the hard decision result obtained by the hard decision unit 36 and the channel characteristics estimated by the demodulation unit 12, and causes interference with each stream of the MIMO channel. Generate a replica of the other channel's signal. Thereafter, the hard decision canceling unit 38 performs a process of subtracting a replica of the interference signal from the signal demodulated by the demodulating unit 12, and synthesizes the signals that should be the same stream by the maximum ratio combining to obtain a diversity gain. The hard decision decoding unit 40 obtains a distance (likelihood) from an ideal signal point (or a threshold value between signal points) determined by a modulation method corresponding to MCS, and performs error correction decoding again by maximum likelihood decoding. .

  Also in the present embodiment, the data read from the buffering unit 28 before iterative decoding has a lower error rate characteristic than the output data from the iterative decoding unit 18, so that the output data from the iterative decoding unit 18 is used as much as possible. Thus, switching control is performed so that the error rate is as small as possible without increasing the processing delay.

  The radio reception apparatus 2 according to the present embodiment cancels interference components for data stored in the buffering unit 28 as well, thereby minimizing signal quality degradation and realizing high reception performance.

  Moreover, since the radio reception apparatus 2 according to the present embodiment stores the output data from the demodulation unit 12 in the buffering unit 28, it is particularly suitable for a configuration in which the processing of the decoding unit 14 takes time.

  FIG. 6 is a diagram illustrating an example of the configuration of the decoding unit 14. The decoding unit 14 illustrated in FIG. 6 includes a likelihood calculation unit 42, a deinterleaving unit 44, and an error correction decoding unit 46. In this configuration, when the deinterleaving unit 44 performs deinterleaving for each symbol, a processing delay of at least one symbol occurs.

  Further, as specified in IEEE 802.11, when error correction coding is convolutional coding and the transmission format is such that decoding cannot be completed in symbol units, the processing delay further increases. . This is because, when Viterbi decoding is performed on the receiving side corresponding to convolutional coding, a traceback length several times the constraint length of convolutional coding is required. For this reason, even if reception of one symbol is completed, in order to decode the last bit in the symbol, it is necessary to wait for the input of the next symbol. As described above, when iterative decoding is performed, it is necessary to always use a signal delayed by one symbol or more, which is a cause of increasing the processing delay.

  In the case of the block Ack mode defined by the IEEE 802.11n draft, iterative decoding can be performed regardless of the MCS and the packet length. This means that an Ack signal is always returned regardless of whether or not an error has occurred as a result of decoding. Therefore, even if the iterative decoding of the last packet has not been completed, it is possible to afford time by first returning the error determination result for the packet received before the iterative decoding has already been completed. Because. However, it is assumed that iterative decoding has been completed before the timing of returning the error determination result of the last packet.

  When the wireless reception device 2 according to the second embodiment is a wireless reception device including the decoding unit 14 (see FIG. 6) including the deinterleave unit 44, for example, it takes time for the decoding process in the decoding unit 14. Is particularly effective.

(Third embodiment)
Next, the wireless transmission device 3 according to the embodiment of the present invention will be described. The wireless transmission device 3 according to the third embodiment has a maximum number of padding bits when the data to be transmitted is divided into packets in an upper layer based on a network structure design policy “OSI (Open Systems Interconnection)”. Control to be

  FIG. 7 is a diagram illustrating a configuration for performing packet division in the wireless transmission device 3 according to the third embodiment. The wireless transmission device 3 includes a packet dividing unit 50 and a division unit determining unit 52. The packet division unit 50 divides the input data into packets having a size determined by the division unit determination unit 52. In addition, the wireless transmission device 3 includes a buffer 54 and a buffer 56 before and after the packet dividing unit 50. These buffers 54 and 56 have a role of mitigating the influence of jitter before and after packet division.

  When the MCS determined according to the state of the propagation path is input, the division unit determination unit 52 checks the number of bytes Ns that can be transmitted per symbol, and sets the packet length Ni to Ni = Ns × M + 1. Stipulated in Here, M is an arbitrary natural number, but it is general that the designer sets an optimal value based on the state of the propagation path, the hardware configuration, and the like so as to maximize the throughput.

  By setting the packet length Ni as described above, the number of padding bits is always (Ns−1) × 8, which is the maximum value, so that a time margin for performing the iterative decoding process is obtained. In particular, when transmitting a stream signal such as a video signal, it is assumed that transmission is continued with a constant packet length, and it is sufficient to set the packet length Ni once when MCS is set, and control is easy. It is. The wireless reception device that has received the packet transmitted from the wireless transmission device 3 according to the present embodiment has a time margin for receiving almost one symbol, and can return an Ack signal at the SIFS timing. Increases nature.

  Since the wireless transmission device 3 of the third embodiment does not add unnecessary dummy data, there is no adverse effect such as a decrease in transmission efficiency. A high-performance reception method using iterative decoding can be adopted while conforming to the standard, which is preferable.

  The function for dividing the data to be transmitted in units of packets may be implemented in any layer as long as the OSI reference model has three or more layers. Therefore, it is necessary to control to set the packet length based on the MCS.

(Fourth embodiment)
Next, the wireless transmission device 4 according to the fourth embodiment will be described. The wireless transmission device 4 of the fourth embodiment has the same basic configuration as the wireless transmission device 3 of the third embodiment, but the padding bits are set to predetermined values (for example, all 0). Instead, the padding bits include a signal having error correction capability.

  For example, when the wireless transmission device 4 performs puncturing after convolutional coding to improve the coding rate, the punctured bits are collectively transmitted as padding bits. In the radio reception apparatus, the decoding performance is improved by using this puncture bit during Viterbi decoding. By transmitting the puncture bits without interleaving, deinterleaving is not required and the occurrence of latency can be prevented.

  FIG. 8 is a diagram illustrating a configuration of the wireless transmission device 4 according to the fourth embodiment. As illustrated in FIG. 8, the wireless transmission device 4 includes a scramble unit 60, a convolutional coding unit 62, a puncture unit 64, an interleave unit 66, a switching unit 68, and an interleave pattern determination unit 70. The scramble unit 60 has a function of scrambling data input from the MAC unit with a predetermined pattern. The convolutional encoding unit 62 has a function of convolutionally encoding the scrambled data. The puncturing unit 64 has a function of puncturing the convolutionally encoded data at a predetermined interval. The interleave unit 66 has a function of interleaving the punctured data. Interleave pattern determining section 70 determines an interleave pattern based on MCS (modulation scheme and coding rate), and inputs the determined interleave pattern to interleave section 66.

  The data from the MAC part includes a predetermined padding bit. In the present embodiment, the bits before puncturing are extracted from the puncturing unit 64 and input to the switching unit 68. The switching unit 68 performs switching control so that the bit before puncturing input from the puncturing unit 64 is output at the timing when padding bits are output. Here, when predetermined convolutional coding and puncturing are performed on the number of padding bits (Ns−1) × 8 before error correction coding or the like is performed, the number of bits changes to K. That is, it should be noted that the number of bits before puncturing that can be transmitted is limited to K bits instead of (Ns−1) × 8. The switching unit 68 controls the switching timing so that puncture bits for K bits are transmitted from the final data.

  FIG. 9 is a diagram illustrating a configuration of a decoding unit of the wireless reception device 5 that receives a packet transmitted from the wireless transmission device 4 described above. The basic configuration of the wireless reception device 5 is the same as that of the first embodiment except for the decoding unit shown in FIG.

  As illustrated in FIG. 9, the decoding unit of the wireless reception device 5 includes a demapping unit 80, a likelihood calculating unit 82, a deinterleaving unit 84, a depuncturing unit 86, a Viterbi decoding unit 88, and a timing control unit 90. Have The demapping unit 80 demaps the signal output from the demodulation unit based on a predetermined modulation method, and inputs the demapped result to the likelihood calculating unit 82. The likelihood calculating unit 82 calculates the minimum value of the distance from the ideal signal point on the phase space diagram. The deinterleaving unit 84 performs deinterleaving using the likelihood calculated by the likelihood calculating unit 82. The depuncture unit 86 depunctures the deinterleaved data.

  Conventionally, the depuncture unit 86 always depunctures an intermediate value between the likelihood corresponding to bit 0 and the likelihood corresponding to bit 1. The debanking unit 86 in the present embodiment depunctures the same value as before from the last data to K + 1 bits, and the likelihood value obtained by the likelihood calculating unit 82 for data after K bits before the last data. Replace with

  FIG. 10 is a diagram illustrating processing timing in the wireless reception device 5. In FIG. 10, the number of symbols to be transmitted is L, and the last three symbols are shown. As shown in FIG. 10, the processing is not started in the subsequent deinterleaving unit 84 until the processing is completed for each symbol in the likelihood calculating unit 82. The depuncture unit 86 starts depuncturing after the processing delay P1 has elapsed from the deinterleave unit 84. In the present embodiment, in order to use the depuncture data obtained by the likelihood calculating unit 82, the timing control unit 90 controls so that the depuncture timing is delayed by P2 only for the second symbol from the last.

  As described above, the depuncture unit 86 performs the depuncture process performed using the puncture data inserted at the position of the padding bit only for several symbols close to the final symbol. As a result, the depuncture unit 86 performs the depuncture up to several symbols close to the final symbol without using the puncture data, so that the depuncture process can be completed quickly.

  In the present embodiment, instead of padding bits, puncture data is included in a symbol and transmitted, so that the radio reception apparatus performs error correction using this puncture data, and does not perform iterative decoding. As for, reception performance can be improved. Therefore, as described in the first embodiment and the second embodiment described above, even when the decoded data decoded by the decoding unit is used in order to meet the SIFS timing, it is input to the MAC unit. It is possible to reduce errors in the decoded data.

  The present invention has an effect of preventing a reduction in transmission efficiency due to retransmission and a reduction in throughput while minimizing the occurrence of errors, for example, attenuation of radio waves due to obstacles such as wireless video transmission It can be applied to wireless communication or the like in a large environment.

The figure which shows the structure of the radio | wireless receiver of 1st Embodiment The figure which shows the decoding timing in the decoding process of the conventional radio | wireless receiver. The figure which shows the decoding timing in the decoding apparatus of the radio | wireless receiver in 1st Embodiment The figure which shows the example of the table which determines a switching timing in a radio | wireless receiver. The figure which shows the structure of the radio | wireless receiver of 2nd Embodiment. The figure which shows the example of the decoding apparatus which the radio | wireless receiver of 2nd Embodiment has The figure which shows the structure for the packet division | segmentation in the radio | wireless transmitter of 3rd Embodiment The figure which shows the structure for the symbol production | generation in the radio | wireless transmitter of 4th Embodiment. The figure which shows the structure of the radio | wireless receiver which receives the packet transmitted from the radio | wireless transmitter of 4th Embodiment. The figure which shows the timing of the reception process in a radio | wireless receiver.

Explanation of symbols

8 Receiving Unit 10 Synchronizing Unit 12 Demodulating Unit 14 Decoding Unit 16 Packet Analyzing Unit 18 Iterative Decoding Unit 20 Canceling Unit 22 Decoding Unit 24 MAC Unit 26 Transmitting Unit 28 Buffering Unit 30 Reading Control Unit 32 Switching Unit 34 Switching Timing Determination Unit 36 Hard Determination unit 38 Hard decision cancellation unit 40 Hard decision decoding unit 42 Likelihood calculation unit 44 Deinterleaving unit 46 Error correction decoding unit 50 Packet division unit 52 Division unit determination unit 54 Buffer 56 Buffer 60 Scramble unit 62 Convolution coding unit 64 Puncture unit 66 Interleave unit 68 Switching unit 70 Interleave pattern determination unit 80 Demap unit 82 Likelihood calculation unit 84 Deinterleave unit 86 Depuncture unit 88 Viterbi decoding unit 90 Timing control unit

Claims (17)

A packet data receiver for receiving packet data modulated by the digital modulation method;
A decoding unit for decoding the packet data for each symbol;
A buffering unit for storing the decoded data decoded by the decoding unit;
An iterative decoding unit that performs iterative decoding using the decoded data decoded by the decoding unit;
Which decoded data is acquired from the decoded data decoded by the decoding unit and sequentially stored in the buffering unit, and the decoded data sequentially generated by the iterative decoding unit using the decoded data A switching unit for switching between,
Transmission error determination for determining whether or not a transmission error has occurred in the packet data by configuring the packet data using the decoded data sequentially acquired from the iterative decoding unit or the buffering unit via the switching unit And
An acknowledgment transmission unit for transmitting an acknowledgment when the transmission error determination unit determines that a transmission error has not occurred;
A wireless receiver comprising:   The switching unit switches to obtain decoded data corresponding to symbols from the last symbol to a predetermined number of symbols before the final symbol from the buffering unit, and to obtain decoded data corresponding to the remaining symbols from the iterative decoding unit. The wireless receiver according to claim 1, wherein:   The time obtained by completing the iterative decoding process in the iterative decoding unit from the predetermined acknowledgment transmission timing divided by the interruption time in which the decoding process by the decoding unit is interrupted between symbols is greater than or equal to the value obtained The radio reception apparatus according to claim 2, further comprising a switching timing determination unit that determines the smallest integer as the predetermined number.   The radio reception apparatus according to claim 3, wherein the switching timing determination unit determines the predetermined number based on the number of padding bits included in a final symbol. The switching timing determination unit
A table storing the number of padding bits and the predetermined number in association with each other;
The radio reception apparatus according to claim 4, wherein the predetermined number is determined with reference to the table. A wireless transmission device that modulates and transmits packet data using a digital modulation method;
The wireless reception device according to any one of claims 1 to 5, which receives the packet;
A wireless communication system.   The wireless communication system according to claim 6, wherein the wireless transmission device includes a packet division unit that divides transmission data into packet data having a length that is an integral multiple of the number of bytes that can be transmitted in one symbol + 1 byte. The wireless transmission device
A puncture processing unit for performing a puncture process to thin out the transmission data;
A radio signal generation unit that generates a radio signal including puncture data thinned out by the puncture processing unit in a final symbol of a plurality of symbols carrying packet data;
The wireless communication system according to claim 6. The decoding unit of the wireless reception device,
The wireless communication system according to claim 8, further comprising a depuncture processing unit that performs depuncture processing using puncture data included in the final symbol. A packet division unit that divides transmission data into packet data having an integer multiple of the number of bytes that can be transmitted in one symbol + 1 byte;
A radio signal generator for generating a radio signal carrying the packet data;
A transmitter for transmitting the wireless signal;
A wireless transmission device comprising: A puncture processing unit that performs puncture processing to thin out transmission data;
A packet division unit for dividing the transmission data into a plurality of packet data;
A radio signal generation unit that generates a radio signal including puncture data thinned out by the puncture processing unit in a final symbol of a plurality of symbols carrying the packet data;
A transmitter for transmitting the wireless signal;
A wireless transmission device comprising: Receiving packet data modulated by a digital modulation scheme;
Decoding the packet data for each symbol;
Storing the decoded data in the buffering unit;
Performing iterative decoding using the decoded data;
Switching between which decoded data is to be acquired among the decoded data that is sequentially stored in the buffering unit and the decoded data that is sequentially generated by iterative decoding using the decoded data;
Configuring packet data using decoded data obtained sequentially while performing switching by the switching step, and determining whether a transmission error has occurred in the packet data; and
Sending an acknowledgment when it is determined that no transmission error has occurred;
A wireless reception method comprising: Dividing the transmission data into integer multiples of the number of bytes that can be transmitted in one symbol + 1 byte long packet data;
Generating a radio signal carrying the packet data;
Transmitting the wireless signal;
A wireless transmission method comprising: A step of performing puncture processing to thin out transmission data;
Dividing the transmission data into a plurality of packet data;
Generating a radio signal including puncture data thinned out from transmission data in a final symbol of a plurality of symbols carrying packet data;
Transmitting the wireless signal;
A wireless transmission method comprising: A program for receiving packet data modulated by a digital modulation method,
Receiving the packet data;
Decoding the packet data for each symbol;
Storing the decoded data in the buffering unit;
Performing iterative decoding using the decoded data;
Switching between which decoded data is to be acquired among the decoded data that is sequentially stored in the buffering unit and the decoded data that is sequentially generated by iterative decoding using the decoded data;
Configuring packet data using decoded data obtained sequentially while performing switching by the switching step, and determining whether a transmission error has occurred in the packet data; and
Sending an acknowledgment when it is determined that no transmission error has occurred;
A program that executes A program for modulating and transmitting packet data by a digital modulation method, to a computer,
Dividing the transmission data into integer multiples of the number of bytes that can be transmitted in one symbol + 1 byte long packet data;
Generating a radio signal carrying the packet data;
Transmitting the wireless signal;
A program that executes A program for modulating and transmitting packet data by a digital modulation method, to a computer,
A step of performing puncture processing to thin out transmission data;
Dividing the transmission data into a plurality of packet data;
Generating a radio signal including puncture data thinned out from transmission data in a final symbol of a plurality of symbols carrying the packet data;
Transmitting the wireless signal;
A program comprising

Images