JP2008011260A - Radio communication method, radio transmitter, and radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve performance of error correction by preventing a transmission error of information bits when information bits and a parity bit are subjected to multi-level modulation and transmitted. <P>SOLUTION: A radio communication method includes the steps of: performing by a radio transmitter, error correction encoding where the parity bit is added to the information bits; allocating by the radio transmitter, information bits and parity bit to a symbol so that the information bits are allocated to bits having high error tolerance among a plurality of bits allocated to the one symbol; and decoding by a radio receiver, the information bits and parity bit allocated to the symbol received from the radio transmitter, based upon the allocation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication method, a wireless transmission device, and a wireless reception device that perform communication using symbols to which a plurality of bits are assigned.

  Conventionally, in a wireless communication system, a turbo code that realizes transmission characteristics close to the limit of information theory (Shannon limit) is known as an error correction code technique for strongly correcting transmission errors in a transmission line (for example, non-patented). Reference 1).

  In such a wireless communication system, a turbo encoder is disposed in a transmitting-side wireless communication apparatus (hereinafter referred to as a wireless transmitting apparatus), and a turbo decoder is disposed in a receiving-side wireless communication apparatus (hereinafter referred to as a wireless receiving apparatus).

  In a turbo encoder arranged in a wireless transmission device, error correction coding is performed in which a parity bit is added to information bits.

  On the other hand, the turbo decoder arranged in the wireless receiver corrects transmission errors in the transmission path by repeating the decoding process of the received information bits and parity bits.

Further, in such a wireless communication system, the wireless transmission device increases transmission efficiency by modulating information bits and parity bits using multi-level modulation in which a plurality of bits are assigned to one symbol.
C. Berrou, A. Glavieux and P. Thitimajshima, “Near Shannon limit error-correcting coding and decording: turbo codes”, Proc. ICC'93, pp. 1064-1070, 1993

  By the way, when error correction is performed by decoding information bits and parity bits, if there is a transmission error in the information bits, the influence on the accuracy of the decoding result, that is, error correction characteristics, is greater than when there is a transmission error in the parity bits. large.

  In particular, when information bits and parity bits are subjected to multilevel modulation and transmitted in an environment with a poor radio propagation path, there has been a problem that error correction performance is likely to deteriorate due to transmission errors of information bits.

  Accordingly, the present invention provides a wireless communication method, a wireless transmission device, and a wireless reception device that prevent transmission errors of information bits and improve error correction performance when information bits and parity bits are transmitted after being subjected to multilevel modulation. The purpose is to provide.

  According to a first aspect of the present invention, there is provided a wireless communication method for transmitting a symbol to which a plurality of bits are assigned from a wireless transmission device to a wireless reception device, wherein the wireless reception device receives the symbol. However, a step of performing error correction coding for adding a parity bit to information bits, and the wireless transmission device assigns the information bits to bits having high error resistance among the plurality of bits (bit mapping pattern). Assigning the information bits and the parity bits to the symbols, and based on the assignment, the wireless reception device decodes the information bits and parity bits assigned to the symbols received from the wireless transmission device. And a step of performing.

  According to such a feature, when information bits and parity bits are multi-value modulated and transmitted by the wireless transmission device, the wireless transmission device gives priority to a bit having high error resistance among a plurality of bits allocated to one symbol. By allocating information bits automatically, transmission errors of information bits can be prevented and error correction performance can be improved.

  In the first aspect of the present invention, the wireless transmission device further includes a step of determining whether or not the propagation path quality with the wireless reception device is less than a predetermined threshold, The step of allocating the information bits and the parity bits to the symbols may be performed when the information bits are less than a predetermined threshold.

  According to such a feature, when the channel quality between the wireless transmission device and the wireless reception device is less than a predetermined threshold, by assigning information bits and parity bits to symbols as described above, the wireless transmission device The optimum allocation pattern can be selected according to the propagation path quality.

  In the first aspect of the present invention, the wireless transmission device notifies the wireless reception device of information indicating the assignment, and the wireless reception device performs the wireless transmission based on the notification from the wireless transmission device. Detecting the assignment of the symbols received from a device, and if the assignment is detected for the symbols received from the wireless transmission device, reducing the number of decoding iterations less than a predetermined number, or at least The method may further include a step of preventing the number of repetitions from increasing.

  According to this feature, the radio reception apparatus can estimate that transmission errors of information bits that have a large influence on the accuracy of the decoding result are reduced by detecting the above-described assignment.

  Therefore, the radio reception apparatus reduces the processing load related to decoding by reducing the number of iterations of decoding the restored information bits and parity bits less than a predetermined number, or at least preventing the number of iterations from increasing. can do.

  In the first aspect of the present invention, the wireless receiving device further includes a step of determining whether or not the propagation path quality with the wireless transmission device is less than a predetermined threshold, The step of reducing the number of repetitions may be performed when the value is equal to or greater than a predetermined threshold.

  According to such a feature, the wireless reception device has a transmission error in the information bits and parity bits from the wireless transmission device when the propagation path quality between the wireless transmission device and the wireless reception device is equal to or higher than a predetermined threshold. It can be estimated that the probability is low.

  Therefore, the radio reception apparatus can reduce the processing load related to decoding by reducing the number of repetitions of decoding of the restored information bits and parity bits below a predetermined number.

  On the other hand, when the propagation path quality between the wireless transmission device and the wireless reception device is less than a predetermined threshold value, the decoding result converges by repeating the decoding of the restored information bits and parity bits a predetermined number of times. It is possible to prevent the decoding iteration from ending before.

  A second feature of the present invention is a wireless transmission device that transmits a symbol to which a plurality of bits are allocated to a wireless reception device, and an error correction coding unit that performs error correction coding that adds a parity bit to an information bit (Turbo coding unit 133) and an allocation unit (bit mapping pattern generation) that allocates the information bits and the parity bits to the symbols by allocating the information bits to bits having high error resistance among the plurality of bits. And a modulation unit 135).

  In the second aspect of the present invention, the wireless communication apparatus further includes a propagation path quality determination unit (a propagation path quality determination unit 132) that determines whether or not the propagation path quality with the wireless reception device is less than a predetermined threshold. The assigning unit may assign the information bits and the parity bits to the symbols when the propagation path quality is less than a predetermined threshold.

  According to a third aspect of the present invention, there is provided a wireless reception device for receiving a symbol assigned with a plurality of bits transmitted from a wireless transmission device, wherein an information bit is included in a bit having high error resistance among the plurality of bits. A receiving unit that receives the symbols to which the information bits and the parity bits are assigned, and a decoding unit (turbo decoding unit 237) that performs decoding on the information bits and the parity bits assigned to the symbols. The gist is to do.

  In the third aspect of the present invention, a detection unit (bit mapping pattern detection unit 232) that detects the allocation of the symbol received from the radio transmission device based on a notification from the radio transmission device; and the radio When the assignment is detected for the symbol received from the transmitting apparatus, the number of repetitions of decoding is less than a predetermined number, or at least the number of repetitions is not increased. 236).

  In the third aspect of the present invention, the wireless communication apparatus further includes a channel quality determination unit (channel quality determination unit 235) that determines whether or not the channel quality with the wireless transmission device is less than a predetermined threshold. The repeat count control unit may reduce the repeat count when the propagation path quality is equal to or higher than a predetermined threshold value.

  According to the present invention, when an information bit and a parity bit are transmitted after being subjected to multilevel modulation, an information bit transmission error is prevented and an error correction performance is improved, a wireless transmission device, a wireless transmission device, and a wireless reception device Can be provided.

(Schematic configuration of the wireless communication system according to the present embodiment)
A schematic configuration of a wireless communication system according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the wireless communication system according to the present embodiment is configured such that a wireless transmission device 10 and a wireless reception device 20 communicate with each other via a wireless propagation path 30.

  The wireless transmission device 10 is a wireless communication device on the transmission side, and is installed in a mobile station for uplink communication between a base station and a mobile station (for example, a mobile phone terminal), and a base station for downlink communication. Mounted on.

  On the other hand, the radio reception device 20 is a radio communication device on the reception side, and is installed in the base station for uplink communication between the base station and the mobile station, and is installed in the mobile station for downlink communication.

  In the wireless communication system according to the present embodiment, multi-level modulation such as 16QAM (16 Quadrature Amplitude Modulation) or 64QAM (64 Quadrature Amplitude Modulation) is used in communication between the wireless transmission device 10 and the wireless reception device 20.

  Multilevel modulation is a modulation method in which a plurality of bits are assigned to one symbol and information of a plurality of bits can be transmitted in one symbol. In the present embodiment, among multi-level modulation, in particular, 16 QAM capable of transmitting 4 bits (16 values) of information with one symbol, 64 QAM capable of transmitting 6 bits (64 values) of information with one symbol, etc. The description will be made assuming that modulation is used.

(Characteristics of multi-level modulation)
The characteristics of multilevel modulation, specifically, the characteristics of bits assigned to symbols by multilevel modulation will be described with reference to FIGS.

  With reference to FIG. 2, the symbol point arrangement in 16QAM Gray Coding and the characteristics of the bits allocated to the symbols will be described. In 16QAM, 4 bits are assigned to one symbol, and, for example, symbol points are arranged as shown in FIG.

  Here, when the reception symbol R1 having the same distance from four adjacent ideal symbol points is demodulated by the radio reception device 20, a symbol determination error that is erroneously determined to be one of the adjacent ideal symbol points due to noise or the like Shall occur. In this case, as shown in FIG. 2B, the received symbol R1 is “1” in bits S3 and S0 among the bits S3 to S0, regardless of which of the four ideal symbol points adjacent to the received symbol R1 is erroneously determined. It is.

  Therefore, out of bits S3 to S0 assigned to one symbol, bits S3 and S1 have a lower probability of occurrence of a determination error and higher error tolerance than bits S2 and S4.

  Next, with reference to FIG. 3, the symbol point arrangement in 64QAM Gray Coding and the characteristics of the bits allocated to the symbols will be described. In 64QAM, 6 bits are allocated to one symbol, and, for example, symbol points are arranged as shown in FIG.

  Here, it is assumed that a symbol determination error occurs due to noise or the like when the radio reception apparatus 20 demodulates the reception symbol R2 having the same distance from four adjacent ideal symbol points. In this case, as shown in FIG. 3B, the received symbol R2 is erroneously determined to be any of the four adjacent ideal symbol points, and among the bits S5 to S0, the bit S5 is “1”. S4 is “0”, bit S2 is “1”, and bit S1 is “0”.

  Therefore, among bits S5 to S0 assigned to one symbol, bits S5, S4, S2, and S1 are less likely to cause a determination error than bits S3 and S0, and have high error resistance.

  As described above, the present invention is applied to multi-level modulation having a characteristic that error tolerance differs among a plurality of bits allocated to one symbol. Hereinafter, the block configurations of the wireless transmission device 10 and the wireless reception device 20 according to the present embodiment will be specifically described.

(Block configuration of wireless transmission device)
A block configuration of the wireless transmission device 10 according to the present embodiment will be specifically described with reference to FIGS. 1 and 4 to 5.

  As illustrated in FIG. 1, the wireless transmission device 10 includes a wireless unit 11, a reception unit 12, a transmission unit 13, and an antenna 14.

  The radio unit 11 converts the modulated baseband transmission signal into a radio frequency transmission signal and transmits the radio baseband transmission signal to the radio reception device 20 via the antenna 14. Further, the radio unit 11 converts a radio frequency band received signal received via the antenna 14 into a baseband band received signal.

  The receiving unit 12 performs demodulation, error correction decoding, and the like of the received signal input from the wireless unit 11. In particular, in the present embodiment, the receiving unit 12 acquires the channel quality of the radio channel 30 that transmits a transmission signal from the radio transmission device 10 to the radio reception device 20 from the radio reception device 20. Here, the propagation path quality is, for example, S / N (Signal power to noise power ratio).

  The transmission unit 13 performs error correction encoding and modulation on transmission data. Specifically, the transmission unit 13 includes a channel quality acquisition unit 131, a channel quality determination unit 132, a turbo encoding unit 133, a bit mapping pattern generation unit 134, and a modulation unit 135.

  The propagation path quality acquisition unit 131 acquires the S / N transmitted from the wireless reception device 20 from the reception unit 12.

  The propagation path quality determination unit 132 determines the propagation path quality of the wireless propagation path 30 that transmits the transmission signal from the wireless transmission device 10 to the wireless reception device 20 based on the S / N acquired from the propagation channel quality acquisition unit 131. To do.

  Specifically, when the S / N is less than a predetermined threshold, the channel quality determination unit 132 notifies the bit mapping pattern generation unit 134 that the S / N is less than the predetermined threshold. Similarly, when the S / N is equal to or greater than a predetermined threshold, the channel quality determination unit 132 notifies the bit mapping pattern generation unit 134 that the S / N is equal to or greater than the predetermined threshold.

  The turbo encoding unit 133 performs error correction encoding on the transmission data using the turbo code. Specifically, as illustrated in FIG. 4, the turbo encoding unit 133 includes two recursive systematic convolutional encoders (RSCs) 133a and 133c that perform recursive systematic convolutional encoding, an interleaver 133b, The turbo coder includes a puncturing / multiplexing unit 133d and a multiplexing unit 133e.

  The convolutional encoder 133a performs recursive systematic convolutional encoding on the information bit sequence X (n), which is each bit of the input transmission data, and outputs a parity bit sequence Y (n).

  The interleaver 133b rearranges the order of the information bit sequence X (n) at random and inputs the information bit sequence X (n) to the convolutional encoder 133c.

  The convolutional encoder 133c performs recursive systematic convolutional encoding on the information bit sequence X (n) whose order is rearranged by the interleaver 133b, and outputs a parity bit sequence Y ′ (n). Note that the configuration of the convolutional encoder 133c may be the same as or different from the configuration of the convolutional encoder 133a.

  The puncturing / multiplexing unit 133d converts the parity bit sequence Y (n) output from the convolutional encoder 133a and the parity bit sequence Y ′ (n) output from the convolutional encoder 133c into coding rates. In response, the output is simply multiplexed or multiplexed while being punctured.

  The multiplexing unit 133e multiplexes the information bit sequence X (n) and the parity bit sequence output from the puncture / multiplexing unit 133d, and outputs the result as a turbo encoded transmission signal sequence. For example, when turbo coding is performed at a coding rate of 1/3, the multiplexing unit 133e outputs a transmission signal sequence as shown in FIG.

  The bit mapping pattern generation unit 134 assigns (maps) a transmission signal sequence including information bits and parity bits output from the turbo encoding unit 133 to symbols based on the notification from the channel quality determination unit 132. .

  Specifically, when the channel quality determination unit 132 is notified that the S / N is less than a predetermined threshold (that is, when the channel state is bad), the bit mapping pattern generation unit 134 performs turbo coding. Mapping is performed using a bit mapping pattern for preventing transmission errors of information bits in the transmitted signal sequence.

  On the other hand, when the propagation path quality determination unit 132 notifies that the S / N is equal to or greater than a predetermined threshold (that is, when the propagation path state is good), the bit mapping pattern generation unit 134 performs the above bit mapping. Perform mapping without using a pattern.

  Here, the bit mapping pattern is an allocation pattern for allocating each bit of the transmission signal sequence output from the turbo encoding unit 133 to a symbol. In particular, in the present embodiment, a bit mapping pattern for preventing an information bit transmission error is a plurality of bits (for example, bits S3 to S0 in FIG. 2B and bits in FIG. 3B) assigned to one symbol. S5 to S0), information having higher error tolerance (for example, bits S3 and S1 in FIG. 2B and bits S5, S4, S2 and S1 in FIG. 3B) have priority over parity bits. This is an allocation pattern for allocating bits.

  Next, an example of mapping using the bit mapping pattern by the bit mapping pattern generation unit 134 will be specifically described with reference to FIG.

  FIG. 5A is a diagram illustrating a transmission signal sequence output from the turbo encoding unit 133. Here, X (0), X (1), X (2)... X (n) are information bits, Y (0), Y (1), Y (2)... Y (n) and Y ′ (0 ), Y ′ (1), Y ′ (2)... Y ′ (n) are parity bits.

  FIG. 5B is a diagram showing allocation of each bit to a symbol when a bit mapping pattern for preventing a transmission error of information bits is used in 16QAM. When the channel quality determination unit 132 is notified that the S / N is less than a predetermined threshold, the bit mapping pattern generation unit 134 has high error tolerance in one symbol as shown in FIG. Information bits X (0), X (1), X (2)... X (n) are preferentially assigned to bits S3 and S1. Specifically, the bit mapping pattern generation unit 134 realizes the assignment illustrated in FIG. 5B by changing the order of the transmission signal series illustrated in FIG.

  In such a case, the bit mapping pattern generation unit 134 notifies the wireless reception device 20 of information (for example, ON) indicating that a bit mapping pattern that prevents transmission errors of information bits is used using a control signal or the like. .

  FIG. 5C is a diagram illustrating allocation of each bit to a symbol when the above-described bit mapping pattern is not used. When the channel quality determination unit 132 is notified that the S / N is equal to or greater than a predetermined threshold, the bit mapping pattern generation unit 134 transmits the transmission illustrated in FIG. 5A as illustrated in FIG. The signal series is assigned to bits S3 to S0 in order.

  In such a case, the bit mapping pattern generation unit 134 notifies the wireless reception device 20 of information (for example, OFF) indicating that a bit mapping pattern for preventing an information bit transmission error is not used, using a control signal or the like. .

  Further, the bit mapping pattern generation unit 134, as shown in FIG. 5B or FIG. 5C, shows information bits X (n) and parity bits Y (n), Y ′ (n) assigned to S3 to S0. ) Is mapped to a predetermined symbol point (see FIG. 2) of 16QAM by GrayCoding according to the value.

  Although 16QAM has been described here as an example, even in 64QAM, a bit mapping pattern is a bit with high error tolerance (bits S5, S4, S2, and S1 in FIG. 2) that is an information bit in preference to a parity bit. It can be similarly applied by using an allocation pattern for allocating.

  The modulation unit 135 performs a predetermined modulation process on the symbol (transmission signal) mapped to the predetermined symbol point by the bit mapping pattern generation unit 134.

(Block configuration of wireless receiver)
With reference to FIG.1 and FIG.6, the block structure of the radio | wireless receiver 20 which concerns on this embodiment is demonstrated concretely.

  As illustrated in FIG. 1, the wireless reception device 20 includes a wireless unit 21, a transmission unit 22, a reception unit 23, and an antenna 24.

  The radio unit 21 converts a radio frequency band received signal received via the antenna 24 into a baseband band received signal. The modulated baseband transmission signal is converted into a radio frequency transmission signal and transmitted to the radio transmission apparatus 10 via the antenna 24.

  The transmission unit 22 performs error correction encoding and modulation of transmission data. In particular, in the present embodiment, the transmission unit 22 acquires the propagation path quality (for example, S / N) of the wireless propagation path 30 through which the reception signal from the wireless transmission device 10 measured by the reception unit 23 is transmitted, Transmit to the wireless transmission device 10.

  The receiving unit 23 performs demodulation, error correction decoding, and the like of the received signal input from the wireless unit 21. Specifically, the receiving unit 23 includes a demodulating unit 231, a bit mapping pattern detecting unit 232, a bit mapping pattern restoring unit 233, a channel quality measuring unit 234, a channel quality determining unit 235, and determining the number of repetitions. Unit 236 and a turbo decoding unit 237.

  The demodulator 231 performs demodulation processing on the received signal (symbol) input from the radio unit 21. Specifically, the demodulator 231 demaps a received signal (symbol) based on a predetermined symbol point by GrayCoding, and outputs information bits and parity bits assigned to each symbol as a received signal sequence.

  The bit mapping pattern detection unit 232 detects that a bit mapping pattern that prevents transmission errors of information bits is used for information bits and parity bits assigned to symbols received from the wireless transmission device 10.

  Specifically, the bit mapping pattern detection unit 232 acquires information (for example, ON) indicating that a bit mapping pattern for preventing an information bit transmission error is used from the wireless transmission device 10 by notification.

  Also, the bit mapping pattern detection unit 232 acquires information (for example, OFF) indicating that the above-described bit mapping pattern is not used from the wireless transmission device 10 by notification.

  Note that the above-described information indicating ON or OFF is notified by, for example, a control signal from the wireless transmission device 10. The information indicating ON or OFF may be notified at the start of communication between the wireless transmission device 10 and the wireless reception device 20, and can be changed for each predetermined symbol by being notified at predetermined time intervals. May be.

  The bit mapping pattern restoration unit 233 restores information bits and parity bits assigned to the symbols received from the wireless transmission device 10 based on the information indicating ON acquired by the bit mapping pattern detection unit 232.

  Specifically, when the bit mapping pattern detection unit 232 obtains information indicating ON, the bit mapping pattern restoration unit 233 converts the order of each bit of the received signal sequence output from the demodulation unit 231 to the above-described bit. Restore to the order of each bit before applying the mapping pattern.

  For example, in the wireless transmission device 10, when each bit is assigned to a symbol using the above bit mapping pattern as shown in FIG. 5B, the bits assigned to the symbol are restored in order from S3 to S0. , Received signal series are X (0), Y (0), X (3), Y '(1), X (1), Y (1), Y (3), Y' (2), X ( 2), Y (2), Y '(0), Y' (3) ...

  Therefore, the bit mapping pattern restoration unit 233 restores the received signal series in the order shown in FIG. 5A by changing the order based on the bit mapping pattern.

  On the other hand, when the bit mapping pattern detection unit 232 acquires information indicating OFF, the bit mapping pattern restoration unit 233 outputs the received signal sequence output from the demodulation unit 231 as it is.

  That is, in the wireless transmission device 10, when each bit is assigned to a symbol without using the above bit mapping pattern as shown in FIG. 5C, the bits assigned to the symbol are sequentially changed from S3 to S0. When restored, the received signal sequence is X (0), Y (0), Y '(0), X (1), Y (1), Y' (1), X (2), Y (2), Y ′ (2), X (3), Y (3), Y ′ (3). At this time, since the received signal sequence is the same as the order shown in FIG.

  The propagation path quality measurement unit 234 measures the propagation path quality (for example, S / N) of the wireless propagation path 30 to which the reception signal from the wireless transmission device 10 is transmitted based on the reception signal from the wireless transmission device 10. . In addition, the propagation path quality measurement unit 234 instructs the transmission unit 22 to transmit the measured propagation path quality (for example, S / N) to the wireless transmission device 10.

  The propagation path quality determination unit 235 determines the propagation path quality of the wireless propagation path 30 to which the reception signal from the wireless transmission device 10 is transmitted, based on the S / N measured by the propagation path quality measurement unit 234.

  Specifically, when the S / N is less than a predetermined threshold, the propagation path quality determination unit 235 notifies the repetition count determination unit 236 that the S / N is less than the predetermined threshold. Similarly, when the S / N is equal to or greater than a predetermined threshold, the propagation path quality determination unit 235 notifies the repetition count determination unit 236 that the S / N is equal to or greater than the predetermined threshold.

  The iteration count determination unit 236 determines the number of iterations of turbo decoding in the turbo decoding unit 237 based on the notification from the bit mapping pattern detection unit 232 and the channel quality determination unit 235.

  Specifically, when the information indicating ON is acquired by the bit mapping pattern detection unit 232, the iteration number determination unit 236 makes the turbo decoding iteration number less than a predetermined number. Alternatively, the iteration number determination unit 236 may prevent at least the iteration number of turbo decoding from increasing.

  In addition, when it is notified that the S / N is equal to or higher than a predetermined threshold by the propagation path quality determination unit 235 (that is, when the propagation path state is good), the repetition count determination unit 236 The number of iterations of turbo decoding is made smaller than the predetermined number.

  On the other hand, when it is notified by the propagation path quality determination unit 235 that the S / N is less than a predetermined threshold (that is, when the propagation path state is bad), the repetition count determination unit 236 is operated by the bit mapping pattern detection unit 232. Until the information indicating ON is acquired, at least the number of repetitions of turbo decoding in the turbo decoding unit 237 is increased more than a predetermined number.

  The turbo decoding unit 237 performs decoding on the received signal sequence using a turbo code. Specifically, as shown in FIG. 6, the turbo decoding unit 237 includes a depuncture / demultiplexing unit 237a, two convolutional decoders 237b and 237d, an interleaver 237c, and a deinterleaver 237e. Consists of.

  The depuncture / demultiplexing unit 237a performs depuncture and demultiplexing on the received signal sequence restored by the bit mapping pattern restoration unit 233. Then, the depuncture / demultiplexing unit 237a outputs an information bit sequence X (n), a parity bit sequence Y (n), and a parity bit sequence Y ′ (n) from the restored received signal sequence.

  The convolutional decoder 237b corresponds to the convolutional encoder 133a of FIG. 4, and includes information bit sequence X (n) and parity bit sequence Y (n), and reliability information (initial value is 0) from the deinterleaver 237e. Decode using. The convolutional decoder 237b outputs the decoded bit sequence.

  The interleaver 237c corresponds to the interleaver 133b in FIG. 4 and rearranges the order of the bit sequences output from the convolutional decoder 237b. The bit sequence rearranged by the interleaver 237c is input to the convolutional decoder 237d as reliability information. Note that the rearrangement method of the interleaver 237c and the interleaver 133b is the same.

  The convolutional decoder 237d corresponds to the convolutional encoder 133c of FIG. 4, and performs decoding using the information bit sequence X (n) and the parity bit sequence Y ′ (n) and the bit sequence output from the interleaver 237c. Do. The convolutional decoder 237d outputs the decoded bit sequence.

  The deinterleaver 237e returns the order of the bit sequence output from the convolutional decoder 237d. The bit sequence whose order has been returned by the deinterleaver 237e is input to the convolutional decoder 237b as reliability information, and is repeatedly decoded.

  This iterative decoding is repeated for the number of times determined by the above-mentioned number-of-repetitions determination unit 236, whereby final determination is performed and reception data that is an error-corrected information bit sequence is output.

(Communication method of wireless communication system according to this embodiment)
Hereinafter, a communication method in the wireless communication system according to the present embodiment will be described with reference to FIGS.

  With reference to FIG. 7, the operation of the wireless transmission device 10 according to the present embodiment will be described.

  In step S101, the wireless transmission device 10 performs turbo encoding on the transmission data and outputs a transmission signal sequence including information bits and parity bits.

  In step S102, the wireless transmission device 10 determines whether or not the propagation path quality (for example, S / N) of the wireless propagation channel 30 that transmits the transmission signal from the wireless transmission device 10 to the wireless reception device 20 is less than a predetermined threshold value. Determine whether. As described above, the wireless transmission device 10 receives the propagation path quality (S / N) of the wireless propagation channel 30 from the wireless reception device 20.

  When the propagation path quality (S / N) is less than the predetermined threshold (that is, when the propagation path state is bad), the operation proceeds to step S103. On the other hand, when the transmission path quality (S / N) is equal to or higher than a predetermined threshold (that is, when the propagation path state is good), the operation proceeds to step S105.

  In step S103, the wireless transmission device 10 performs mapping using a bit mapping pattern that prevents a transmission error of information bits in the transmission signal sequence output in step S101.

  In such a case, parity bits Y (n), Y ′ (n) are added to bits having high error resistance (for example, in the case of 16QAM, bits S3 and S1 in FIG. 5B) among a plurality of bits assigned to one symbol. The information bit X (n) is assigned with higher priority (see FIG. 5B).

  In step S104, the wireless transmission device 10 notifies information (for example, ON) indicating that the above-described bit mapping pattern is used using a control signal or the like to the wireless reception device 20.

  In step S105, the wireless transmission device 10 performs mapping without using a bit mapping pattern that prevents an information bit transmission error.

  In such a case, each bit of the transmission signal sequence output in step S101 is assigned to bits S3 to S0 constituting one symbol in the output order of step S101 (see FIG. 5C).

  In step S <b> 106, the wireless transmission device 10 notifies information (for example, OFF) indicating that the above-described bit mapping pattern is not used using a control signal or the like to the wireless reception device 20.

  In step S107, modulation processing is performed on the symbols mapped to predetermined symbol points by GrayCoding in step S103 or S105.

  In step S <b> 108, the wireless transmission device 10 transmits the modulated signal to the wireless reception device 20 via the wireless propagation path 30.

  Next, the operation of the wireless reception device 20 according to the present embodiment will be described with reference to FIG.

  In step S <b> 201, the wireless reception device 20 receives a signal transmitted from the wireless transmission device 10 via the wireless propagation path 30.

  In step S202, the wireless reception device 20 performs demodulation processing on the received signal. Specifically, the wireless reception device 20 performs demapping based on a predetermined symbol point by GrayCoding, and outputs each bit assigned to the received symbol as a received signal sequence.

  In step S <b> 203, based on the notification from the wireless transmission device 10, the wireless reception device 20 uses a bit mapping pattern that prevents an information bit transmission error for the reception signal sequence output in step S <b> 203 ( ON) or not used (OFF).

  When a bit mapping pattern for preventing transmission errors of information bits is used for the reception signal sequence output in step S203 (when ON is notified from the wireless transmission device 10), wireless reception is performed in step S204. The apparatus 20 restores the order of each bit of the received signal sequence output in step S203 to the order of each bit before applying the above bit mapping pattern.

  In step S205, since the bit mapping pattern for preventing the transmission error of the information bits is used, the wireless reception device 20 subtracts the number of repetitions of turbo decoding in step S208 from a predetermined number. Alternatively, the wireless reception device 20 may prevent at least the number of turbo decoding iterations from increasing.

  In step S206, the radio reception device 20 determines whether or not the channel quality (S / N) of the radio channel 30 to which the reception signal from the radio transmission device 10 is transmitted is less than a predetermined threshold value.

  When the propagation path quality (S / N) is equal to or higher than a predetermined threshold (that is, when the propagation path state is good), in step S207, the radio reception apparatus 20 sets the number of repetitions of turbo decoding in step S208 to a predetermined number. Than subtract.

  In step S208, the radio reception apparatus 20 performs turbo decoding of the reception signal sequence restored in step S204 based on the number of turbo decoding iterations determined in steps S205 and S207.

(Operations and effects of the communication system and communication method according to the present embodiment)
According to the communication system and the communication method according to the present embodiment, when information bits and parity bits are subjected to multilevel modulation and transmitted by the wireless transmission device 10, the wireless transmission device 10 has a plurality of bits assigned to one symbol. Among them, by using a bit mapping pattern that preferentially assigns information bits to bits with high error tolerance, transmission errors of information bits can be prevented and error correction performance can be improved.

  According to the communication system and the communication method according to the present embodiment, when the channel quality between the wireless transmission device 10 and the wireless reception device 20 is less than a predetermined threshold, the above bit mapping pattern is used. The radio transmission apparatus 10 can select an optimum bit mapping pattern according to the propagation path quality.

  According to the communication system and the communication method according to the present embodiment, the radio reception device 20 detects the bit mapping pattern described above, thereby reducing information bit transmission errors that have a large effect on the accuracy of the decoding result. Can be estimated.

  Therefore, the radio reception apparatus 20 reduces the processing load related to decoding by reducing the number of iterations of decoding the restored information bits and parity bits to be less than a predetermined number, or at least not increasing the number of iterations. Can be reduced.

  According to the communication system and the communication method according to the present embodiment, when the channel quality between the wireless transmission device 10 and the wireless reception device 20 is equal to or higher than a predetermined threshold, the wireless reception device 20 It can be estimated that there is a low probability of transmission errors occurring in the information bits and parity bits.

  Therefore, the wireless reception device 20 can reduce the processing load related to decoding by reducing the number of repetitions of decoding of the restored information bits and parity bits below a predetermined number.

  On the other hand, when the channel quality between the wireless transmission device 10 and the wireless reception device 20 is less than a predetermined threshold, the decoding result is obtained by repeating the decoding number of times of the restored information bits and parity bits a predetermined number of times. It is possible to prevent the repetition of decoding from being completed before convergence.

(Other embodiments)
As mentioned above, although an example of the present invention has been described, it is merely a specific example, and the present invention is not particularly limited, and the specific configuration and the like of each part can be appropriately changed in design.

  For example, in the above-described embodiment, it has been described that the mapping using the bit mapping pattern for preventing the transmission error of information bits is performed as shown in FIG. 5B. However, the information bits are bits with high error tolerance. If it is assigned to, it is not limited to the above-mentioned system.

  In the above-described embodiment, 16QAM and 64QAM have been described. However, the present invention can be similarly applied to 256QAM.

  In addition, the configuration of each embodiment and the configuration of each modified example can be combined. In addition, the operation and effect of each embodiment and each modification are merely a list of the most preferable operations and effects resulting from the present invention, and the operation and effect according to the present invention are described in each embodiment and each modification. It is not limited to the ones.

1 is an overall schematic configuration diagram of a communication system according to an embodiment of the present invention. It is a figure which shows the example of Gray Coding of 16QAM. It is a figure which shows the example of Gray Coding of 64QAM. It is a block block diagram of the turbo encoding part 133 which concerns on embodiment of this invention. It is a figure which shows the mapping by the bit mapping pattern production | generation part 134 which concerns on embodiment of this invention. It is a block block diagram of the turbo decoding part 237 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radio | wireless transmitter 10 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radio | wireless receiver 20 which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Radio transmission apparatus, 11 ... Radio | wireless part, 12 ... Reception part, 13 ... Transmission part, 131 ... Propagation path quality acquisition part, 132 ... Propagation path quality determination part, 133 ... Turbo encoding part, 133a ... Turbo encoder 133b ... interleaver, 133c ... turbo encoder, 133d ... puncture / multiplexer, 133e ... multiplexer, 134 ... bit mapping pattern generator, 135 ... modulator, 14 ... antenna, 20 ... radio receiver, 21 ... wireless unit, 22 ... transmitting unit, 23 ... receiving unit, 24 ... antenna, 30 ... radio propagation path, 231 ... demodulating unit, 232 ... bit mapping pattern detecting unit, 233 ... bit mapping pattern restoring unit, 234 ... propagation path quality Measurement unit, 235... Propagation path quality determination unit, 236... Iteration number determination unit, 237... Turbo decoding unit, 237a .. depuncture / demultiplexing unit 237b ... turbo decoder, 237 c ... interleaver, 237d ... turbo decoder, 237e ... deinterleaver

Claims (9)

A radio communication method of transmitting a symbol to which a plurality of bits are assigned from a radio transmission device to a radio reception device, wherein the radio reception device receives the symbol,
The wireless transmission device performs error correction encoding to add parity bits to information bits;
Assigning the information bit and the parity bit to the symbol in such a manner that the wireless transmission device assigns the information bit to a bit having high error resistance among the plurality of bits;
And a step of decoding the information bits and parity bits assigned to the symbol received from the wireless transmission device based on the assignment. The wireless transmission device further includes a step of determining whether or not a propagation path quality with the wireless reception device is less than a predetermined threshold;
The radio communication method according to claim 1, wherein the step of assigning the information bits and the parity bits to the symbols is performed when the propagation path quality is less than a predetermined threshold. The radio transmission apparatus notifies the radio reception apparatus of information indicating the allocation, and the radio reception apparatus assigns the allocation of the symbols received from the radio transmission apparatus based on the notification from the radio transmission apparatus. Detecting steps,
When the allocation is detected for the symbol received from the radio transmission apparatus, the method further comprises a step of reducing the number of repetitions of decoding to be less than a predetermined number, or at least preventing the number of repetitions from increasing. The wireless communication method according to claim 1 or 2. The wireless receiving device further includes a step of determining whether or not a propagation path quality with the wireless transmitting device is less than a predetermined threshold;
The wireless communication method according to claim 3, wherein the step of reducing the number of repetitions is performed when the propagation path quality is equal to or higher than a predetermined threshold. A wireless transmission device that transmits a symbol to which a plurality of bits are assigned to a wireless reception device,
An error correction encoding unit for performing error correction encoding to add a parity bit to information bits;
A radio transmission apparatus comprising: an allocation unit that allocates the information bits and the parity bits to the symbols so that the information bits are allocated to bits having high error tolerance among the plurality of bits. Further comprising a propagation path quality determination unit for determining whether or not the propagation path quality with the wireless reception device is less than a predetermined threshold;
The radio transmission apparatus according to claim 5, wherein the allocating unit allocates the information bits and the parity bits to the symbols when the propagation path quality is less than a predetermined threshold value. A radio reception apparatus that receives a symbol assigned with a plurality of bits transmitted from a radio transmission apparatus,
A receiving unit for receiving a symbol to which the information bit and the parity bit are assigned so that an information bit is assigned to a bit having high error resistance among the plurality of bits;
A radio receiving apparatus comprising: a decoding unit that decodes information bits and parity bits assigned to the symbol. A detection unit that detects the assignment of the symbol received from the wireless transmission device based on a notification from the wireless transmission device;
A repetition number control unit that reduces the number of repetitions of decoding less than a predetermined number, or at least prevents the number of repetitions from increasing when the assignment is detected for the symbol received from the wireless transmission device; The wireless receiver according to claim 7, further comprising: Further comprising a propagation path quality determination unit for determining whether the propagation path quality with the wireless transmission device is less than a predetermined threshold;
The radio reception apparatus according to claim 8, wherein the repetition count control unit makes the repetition count less than the predetermined count when the propagation path quality is equal to or higher than a predetermined threshold value.

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