JP2007214783A - Transmitting apparatus, receiving apparatus, and transmission method - Google Patents

Abstract

Transmission characteristics are improved when HARQ technology or repetition technology is applied.
A mapping unit 103 that maps a bit in transmission information to a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component and creates a transmission symbol, and a mapping pattern used for the mapping are shared with a receiving apparatus And at least one mapping pattern at the time of overlapping transmission or retransmission is a mapping pattern at the time of transmission other than a combination of bits in transmission information mapped to the modulation symbol. It is characterized by being different.
[Selection] Figure 1

Description

  The present invention relates to a transmission device, a reception device, and a transmission method.

  Conventionally, HARQ (Hybrid Auto Request) technology (for example, refer to nonpatent literature 1), duplication (repetition) technology, etc. are known as a transmission technology for improving communication reliability. In the HARQ technology, retransmission control and error correction are combined, a packet subjected to error correction coding is transmitted, and when the packet is not correctly received, another packet created from the same transmission information is transmitted. Transmission information is obtained from the plurality of packets. In the repetition technique, a plurality of symbols created from the same transmission information are transmitted, and the reception side demodulates and combines the plurality of symbols to obtain transmission information. As a result, accurate transmission information can be obtained with a higher probability than when transmission information is obtained from a single symbol.

  In both the HARQ technique and the repetition technique, transmission symbols are generated a plurality of times from the same transmission information, and bits in the transmission information are mapped to modulation symbols when the transmission symbols are generated. An example of the mapping pattern is shown in FIG. The example of FIG. 12 is a case where 16QAM (16-positions Quadrature Amplitude Modulation) whose constellation pattern is shown in FIG. 11 is used as a modulation method, and two times from the same transmission information (16 bits in this example). It is a mapping pattern when creating a transmission symbol. As shown in FIG. 11, 16QAM modulation symbols are composed of 4 bits of “m (0) m (1) m (2) m (3)”. In FIG. 12, when the first transmission symbol is created, the bit string “b (0) b (1)... B (15)” in the transmission information is “m (0) m (1) m (2)” in the same order. m (3) "is mapped sequentially. Next, mapping is performed in exactly the same pattern at the time of the second transmission symbol creation.

  FIG. 13 shows another example of the mapping pattern when 16QAM is used. In the example of FIG. 13, when the first transmission symbol is created, the bit string “b (0) b (1)... B (15)” in the transmission information is “m” in the same order as in the mapping pattern of FIG. (0) m (1) m (2) m (3) "are sequentially mapped. However, when the second transmission symbol is created, the bit combination mapped to the modulation symbol is the same as when the first transmission symbol is created, but the first bit m (0) and the third bit m (2) The bit to be mapped is switched, and the bit mapped to the second bit m (1) and the fourth bit m (3) is switched.

  In 16QAM, as shown by the constellation pattern in FIG. 11, there is a difference in reliability depending on the bit mapping position. More specifically, FIG. 11 shows a range of bit value = 1 of each bit of “m (0) m (1) m (2) m (3)”, which can be understood from the range. Thus, it can be said that each bit of “m (2) m (3)” is more likely to be erroneous than each bit of “m (0) m (1)”. Therefore, if the bits to be mapped are exchanged according to the mapping pattern of FIG. 13, a diversity effect by the first transmission symbol and the second transmission symbol can be obtained, and the demodulation performance can be improved.

A turbo code is known as an error correction code as a transmission technique for improving the reliability of communication. Non-Patent Document 2 describes a twin turbo decoding technique with improved decoding performance.
Sawabashi Mamoru, Higuchi Kenichi, Shin Hiroyuki, Miki Nobuhiko, “W-CDMA High-Speed Packet Radio Access and Radio Link Characteristics”, IEICE (B), vol. J84-B, no.10, pp1725-1745, 2001 10 Moon T. Suzuki, N. Miyazaki, Y. Hatakawa, “A Proposal of Twin Turbo Detector and Its Evaluation for M-QAM OFDM”, Proc. Of 2005 IEICE Society Conference, B-5-6, Sept. 2005.

  However, the above-described conventional mapping pattern has a problem that transmission characteristics cannot be sufficiently improved when the HARQ technique or the repetition technique is applied.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a transmission apparatus, a reception apparatus, and a transmission method capable of improving transmission characteristics when applying HARQ technology or repetition technology. There is to do.

  In order to solve the above-described problem, a transmission apparatus according to the present invention provides a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component in a transmission apparatus that transmits or retransmits all or part of transmission information. Modulation means for mapping the bits in the transmission information to create a transmission symbol, and mapping pattern sharing means for sharing the mapping pattern used for the mapping with the receiving apparatus, and at least one at the time of duplicate transmission or retransmission The two mapping patterns are characterized in that a combination of bits in transmission information mapped to the modulation symbols is different from other mapping patterns at the time of transmission.

  The transmission apparatus according to the present invention maps the bits in the transmission information to the modulation symbols in which a plurality of bits are arranged in the transmission apparatus that duplicates or retransmits all or part of the transmission information and performs code spread multiplexing. Modulation means for generating transmission symbols and mapping pattern sharing means for sharing a mapping pattern used for the mapping with a receiving apparatus, and at least one of the mapping patterns at the time of duplicate transmission or retransmission is the modulation A combination of bits in transmission information mapped to symbols is different from other mapping patterns at the time of transmission.

  The transmission apparatus according to the present invention is characterized by comprising encoding means for performing error correction encoding on transmission information.

  In the transmission apparatus according to the present invention, the error correction code is a turbo code.

  In the transmission apparatus according to the present invention, the error correction code is a low density parity check code.

  The receiving apparatus according to the present invention creates a transmission symbol by mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component, and transmits all or part of the transmission information in duplicate or In a receiving apparatus that receives the transmission symbol transmitted from a transmitting apparatus that performs retransmission, a symbol likelihood calculating unit that calculates a symbol likelihood of each received symbol, and a mapping pattern used for the mapping are shared with the transmitting apparatus Mapping pattern sharing means, and demodulation means for determining transmission information transmitted from the transmission device based on the mapping pattern and symbol likelihood for each received symbol, and at least one at the time of duplicate transmission or retransmission The two mapping patterns are bits of transmission information mapped to the modulation symbol. See combined are different from each other and the other at the time of transmission mapping pattern.

  The receiving apparatus according to the present invention creates a transmission symbol by mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged, and transmits or retransmits all or part of the transmission information, and In a receiving apparatus that receives the transmission symbol transmitted from a transmitting apparatus that performs code spread multiplexing, symbol likelihood calculating means for calculating a symbol likelihood of each received symbol, and a mapping pattern used for the mapping, the transmitting apparatus A mapping pattern sharing means for sharing, and a demodulating means for determining transmission information transmitted from the transmission device based on the mapping pattern and symbol likelihood for each received symbol, and at least during duplicate transmission or retransmission One mapping pattern is a bit of transmission information mapped to the modulation symbol. See combined are different from each other and the other at the time of transmission mapping pattern.

  In the receiving apparatus according to the present invention, from the determination result of the demodulating means, the decoding means for decoding the error correction coding applied to the transmission information by the transmitting apparatus, and the probability of the received signal obtained in the decoding process are determined. Feedback means to the demodulating means, wherein the demodulating means uses the accuracy of the feedback signal received for the determination of the transmission information.

  In the receiving apparatus according to the present invention, the error correction code is a turbo code.

  In the receiving apparatus according to the present invention, the error correction code is a low density parity check code.

  The transmission method according to the present invention is a transmission method in which all or part of transmission information is transmitted or retransmitted in duplicate, and the transmission apparatus transmits transmission information to a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component. A modulation process for mapping the bits in the frame to create a transmission symbol, a mapping pattern sharing process for sharing a mapping pattern used for the mapping between the transmission apparatus and the reception apparatus, and A symbol likelihood calculation process for calculating a degree, and a demodulation process in which the reception apparatus determines transmission information transmitted from the transmission apparatus based on the mapping pattern and symbol likelihood for each received symbol. At least one mapping pattern at the time of transmission or retransmission is transmission information to be mapped to the modulation symbol The combination of the bits are different from each other and the other at the time of transmission mapping pattern.

  A transmission method according to the present invention is a transmission method in which all or part of transmission information is duplicated or retransmitted and code spread multiplexed, wherein the transmission apparatus applies modulation symbols to which a plurality of bits are arranged. A modulation process for mapping bits in transmission information to create a transmission symbol, a mapping pattern sharing process for sharing a mapping pattern used for the mapping between the transmission apparatus and the reception apparatus, and the reception apparatus for each received symbol A symbol likelihood calculation process for calculating a symbol likelihood, and a demodulation process in which the receiver determines transmission information transmitted from the transmitter based on the mapping pattern and symbol likelihood for each received symbol. At least one of the mapping patterns at the time of duplicate transmission or retransmission is a transmission that maps to the modulation symbol The combination of bits in the multi-address are different from each other and the other at the time of transmission mapping pattern.

  According to the present invention, it is possible to improve transmission characteristics when HARQ technology or repetition technology is applied.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
In the first embodiment, a transmission system that duplicates and transmits all or part of transmission information using a duplication (repetition) technique will be described as an example.
FIG. 1 is a block diagram showing a configuration of a transmission apparatus according to the first embodiment of the present invention. 2 and 3 are block diagrams showing the configuration of the receiving apparatus according to the embodiment.

First, the transmission apparatus will be described with reference to FIG.
In the transmission apparatus shown in FIG. 1, the encoding unit 101 performs error correction encoding on a bit string “a (0) a (1)... A (7)” in transmission information, and generates a codeword string “b (0) b ( 1) ... b (15) "is output. In each embodiment of the present invention, for convenience of explanation, transmission information consists of 8 bits, and the coding rate of error correction coding is ½.

  The repetition unit 102 copies all or part of the codeword string “b (0) b (1)... B (15)”. In this embodiment, as an example of repetition, as shown in FIG. 1, the entire codeword string “b (0) b (1)... B (15)” is copied and two codeword strings “b ( "0) b (1) ... b (15)" and "b (0) b (1) ... b (15)" are output.

  Mapping section 103 maps the two codeword strings “b (0) b (1)... B (15), b (0) b (1). Transmission symbol group “c (0), c (1), c (2), c (3)”, “c ′ (0), c ′ (1), c ′ (2), c ′ (3)” Is output. The mapping unit 103 uses a modulation scheme (hereinafter referred to as a multi-level modulation scheme) that performs mapping to a modulation symbol in which a plurality of bits are arranged in an in-phase component (I channel) or a quadrature component (Q channel). In this embodiment, 16QAM whose constellation pattern is shown in FIG. 11 is used as an example of the multi-level modulation method. The mapping pattern to the 16QAM modulation symbol is supplied from the mapping pattern sharing unit 104.

  Two transmission symbol groups “c (0), c (1), c (2), c (3)”, “c ′ (0), c ′ (1), c ′ (2), c ′ (3 ) "Is transmitted to the transmission line, but the transmission method is not particularly limited.

  The mapping pattern sharing unit 104 has a function of sharing a mapping pattern used for bit mapping to a modulation symbol with a receiving apparatus. Examples of the sharing method include (Example 1) holding a plurality of common mapping patterns in advance between the transmission device and the reception device, (Example 2) notifying the reception device of the mapping pattern dynamically changed by the transmission device, etc. Is mentioned.

  FIG. 4 shows an example of the mapping pattern according to the present embodiment. The example of FIG. 4 is a case where 16QAM whose constellation pattern is shown in FIG. 11 is used, and the same transmission information (in this example, codeword string “b (0) b (1)... B (15) )) Is a mapping pattern when two transmission symbols are created. As shown in FIG. 11, 16QAM modulation symbols are composed of 4 bits of “m (0) m (1) m (2) m (3)”. In FIG. 4, when the first transmission symbol is created, according to the mapping rule 1, the code word string “b (0) b (1)... B (15)” is “m (0) m (1) m” in the order as they are. (2) m (3) "is mapped sequentially.

  Next, at the time of the second transmission symbol creation, the mapping rule 2 makes the combination of bits mapped to the modulation symbols different from that at the first transmission symbol creation. In FIG. 4, at the time of the first transmission symbol creation, “b (0) b (1) b (2) b (3)”, “b (4) b (5) b (6) b (7)”, Four combinations of "b (8) b (9) b (10) b (11)" and "b (12) b (13) b (14) b (15)" Mapping to (1) m (2) m (3) ". However, at the time of creating the second transmission symbol, four combinations different from the first, “b (0) b (4) b (8) b (12)”, “b (1) b (5) b (9 ) b (13) '', `` b (2) b (6) b (10) b (14) '' and `` b (3) b (7) b (11) b (15) '' 0) m (1) m (2) m (3) ".

  In 16QAM, as shown in the constellation pattern of FIG. 11, since the I channel and the Q channel are completely independent, each of “m (0) m (1) m (2) m (3)” The relevant bits are m (0) and m (2), m (1) and m (3). When the combination of bits mapped to the modulation symbol is the same as in the prior art when the first transmission symbol is created and when the second transmission symbol is created (see FIGS. 12 and 13), these two transmission symbols are used. Even if is considered, b (2) is the only bit related to b (0). However, in this embodiment, when the first transmission symbol is created and the second transmission symbol is created, the bit combinations mapped to the modulation symbols are made different so that the two transmission symbols can be taken into account. For example, the bits related to b (0) can be increased to b (2) and b (8). As a result, on the receiving side, in addition to the time diversity effect due to repetition, by demodulating a plurality of symbols created from different bit combinations, the deterioration of each bit received by the transmission path is smoothed, so that the transmission characteristics are improved. improves.

Next, the receiving apparatus will be described with reference to FIGS.
In the receiving apparatus shown in FIG. 2, two transmission symbol groups “c (0), c (1), c (2), c (3)”, “c ′ (0), c ′” transmitted from the transmitting apparatus. (1), c ′ (2), c ′ (3) ”are two received symbol groups“ g (0), g (1), g (2), g (3) ”,“ g ′ (0 ), G ′ (1), g ′ (2), g ′ (3) ”.

  Symbol likelihood calculating section 201 receives received symbols g (0), g (1), g (2), g (3), g ′ (0), g ′ (1), g ′ (2), g Calculate the likelihood of '(3) respectively, symbol likelihood h (0), h (1), h (2), h (3), h' (0), h '(1), h' ( 2) Output h '(3).

  The channel value generation unit 202 has symbol likelihoods h (0), h (1), h (2), h (3), h ′ (0), h ′ (1), h ′ (2), Based on h ′ (3) and the mapping pattern for each received symbol, the channel value sequence “j (0) corresponding to the codeword sequence“ b (0) b (1)... b (15) ”transmitted from the transmission device. ) j (1) ... j (15) "is generated and output.

  The decoding unit 203 performs an error correction code decoding process on the channel value sequence “j (0) j (1)... J (15)”, and receives the received information bit sequence “I (0) I” as a decoding result. (1) ... I (7) "is output. The probability k (0), k (1),..., K (15) of the received signal obtained in the decoding process is fed back to the channel value generation unit 202. In this embodiment, k (0), k (1), ..., k (15) are posterior values obtained in the decoding process, and codewords b (0), b (1), ..., b (15) respectively. The posterior value obtained in the decoding process represents the likelihood of each bit in decoding, and represents the probability that each bit is 1. The channel value generation unit 202 uses the posterior value obtained in the decoding process for channel value generation.

  The mapping pattern sharing unit 204 supplies a bit mapping pattern to modulation symbols for each received symbol to the channel value generation unit 202. The mapping pattern is shared with the transmission device. In the present embodiment, the mapping pattern shown in FIG. 4 is shared between the transmission apparatus and the reception apparatus as a mapping pattern of bits to 16QAM modulation symbols.

FIG. 3 shows a block configuration diagram of the channel value generation unit 202 shown in FIG.
In FIG. 3, the channel value calculation unit 211 performs symbol likelihoods h (0), h (1), h (2) of received symbols g (0), g (1), g (2), g (3). ), H (3) and the mapping pattern for each received symbol, the channel value j ′ () corresponding to the codewords b (0), b (1),..., B (15) transmitted from the transmitting apparatus. 0), j ′ (1),..., J ′ (15) are calculated. Here, the received symbols g (0), g (1), g (2), and g (3) are transmitted symbols c (0), c (1), c (3) created by the first transmission symbol creation. Since it corresponds to 2) and c (3), the mapping pattern (mapping rule 1) at the time of the first transmission symbol creation shown in FIG. 4 is used.

  Similarly, the channel value calculation unit 212 performs symbol likelihoods h ′ (0), h ′ (1) of the received symbols g ′ (0), g ′ (1), g ′ (2), g ′ (3). ), H ′ (2), h ′ (3), and codewords b (0), b (1),..., B (15) transmitted from the transmission device based on the mapping pattern for each received symbol The channel values j '' (0), j '' (1), ..., j '' (15) to be calculated are calculated. Here, received symbols g ′ (0), g ′ (1), g ′ (2), and g ′ (3) are transmitted symbols c ′ (0) and c ′ created by the second transmission symbol creation. Since it corresponds to (1), c ′ (2), and c ′ (3), the mapping pattern (mapping rule 2) at the time of the second transmission symbol creation shown in FIG. 4 is used.

  The adder 213 includes communication channel values j ′ (0), j ′ (1),..., J ′ (15) and communication channel values j ″ (0), j ″ (1),. (15) is added for each corresponding bit to determine the channel values j (0), j (1),..., J (15).

Further, the channel value calculation units 211 and 212 reflect the posterior values k (0), k (1),..., K (15) fed back from the decoding unit 203 to the respective channel value calculations. Specifically, the likelihood P _{C of} each bit m (0), m (1), m (2), m (3) constituting a 16QAM modulation symbol is represented by an arithmetic expression represented by Expression (1). (m (0)), P _C (m (1)), P _C (m (2)), P _C (m (3)) are calculated.

In the above equation (1), an arithmetic expression for calculating the likelihood P _C (m (0)) of the bit m (0) is representatively shown. In this equation (1), only m (2) is reflected with respect to m (0) because it is sufficient to reflect only the bits mapped on the same I channel (FIG. 11). reference). In addition, the value k () fed back from the decoding unit 203 as a posterior value obtained in the decoding process can be used as the prior value represented by P ().

Here, the calculation method of the communication channel value will be described by taking as an example the case of calculating the communication channel value j (0) corresponding to the codeword b (0) transmitted from the transmission device.
When the posterior values k (0), k (1),..., K (15) at the time of the previous decoding are fed back, the channel value calculation unit 211 returns the posterior values k (0), k (1), ..., k (15) is used as a prior value. At this time, since the channel value calculation unit 211 uses the mapping pattern (mapping rule 1) at the time of the first transmission symbol creation shown in FIG. 4, the bit likelihood j ′ corresponding to the codeword b (0) is used. When obtaining (0), the posterior value k (2) corresponding to the codeword b (2) is used and reflected in the prior value related to m (2) according to the above equation (1).

  On the other hand, when the posterior values k (0), k (1),..., K (15) at the previous decoding are fed back, the channel value calculation unit 212 returns the posterior values k (0), k (1 ),..., K (15) are used as prior values. At this time, the channel value calculation unit 211 uses the mapping pattern (mapping rule 2) at the time of the second transmission symbol creation shown in FIG. Therefore, when the bit likelihood j ″ (0) corresponding to the code word b (0) is obtained, the posterior value k (8) corresponding to the code word b (8) is expressed by m ( Use and reflect in advance values related to 2).

  As a result, the channel value calculation units 211 and 212 calculate the bit likelihood (communication channel value) with a combination of different bits. The result of combining the channel values calculated by the channel value calculation units 211 and 212 is used for the decoding process. Thereby, the demodulation performance can be improved.

Note that although the equation (1) shows an arithmetic expression for calculating the likelihood P _C (m (0)) of the bit m (0), the other bits m (1), m (2) , M (3) likelihoods P _C (m (1)), P _C (m (2)), and P _C (m (3)) can be calculated by the same arithmetic expression.

Next, error correction codes applicable to this embodiment will be described.
Examples of error correction codes applicable to the present embodiment include turbo codes, low-density parity check codes (LDPC codes), and the like.

[Example of application of turbo code]
FIG. 5 is a block diagram showing a configuration of a turbo encoder as encoding section 101 of the transmission apparatus shown in FIG. The configuration of FIG. 5 is well known. FIG. 6 is a block diagram showing a configuration of an embodiment in which a twin turbo decoder is applied to the receiving apparatus shown in FIG. The twin turbo decoder is described in Non-Patent Document 2.

  The turbo encoder shown in FIG. 5 includes two element encoders 1101 and 1102 and performs encoding using two element codes. In FIG. 5, an element encoder 1101 generates a parity bit a1 from transmission information bits. The interleaver 1103 crosses the order of the input transmission information bits. Element encoder 1102 generates parity bit a2 from the transmission information bits output from interleaver 1103. Thereby, parity bits a1 and a2 are generated from the same transmission information bits. However, in the element encoders 1101 and 1102, the input order of transmission information bits is mixed. The turbo encoder 110 outputs a total of 3 bits of the input transmission information bits and parity bits a1 and a2 as encoded data.

  In the receiving device shown in FIG. 6, two communication channel value generation units 202 (communication channel value generation units 202-1 and 202-2) shown in FIG. 3 are provided. The channel value generators 202-1 and 202-2 include symbol likelihoods h (0), h (1), h (2), h (3), h ′ ( 0), h ′ (1), h ′ (2), and h ′ (3) are respectively input. The channel value generators 202-1 and 202-2 have symbol likelihoods h (0), h (1), h (2), h (3), h ′ (0), h ′ (1), Based on h ′ (2) and h ′ (3) and the mapping pattern for each received symbol supplied from the mapping pattern sharing unit 204, each channel value corresponding to the transmission information bits and the parity bits a1 and a2 is generated. And output.

  The twin turbo decoder shown in FIG. 6 has a configuration corresponding to the turbo encoder shown in FIG. 5 and includes a decoder 221 corresponding to the element encoder 1101 and a decoder 222 corresponding to the element encoder 1102. Prepare. With this configuration, the posterior value is iteratively calculated.

  In FIG. 6, first, the decoder 221 inputs the channel values of both the transmission information bit and the parity bit a1 from the channel value generation unit 202-1. Further, when the decoding process is first performed by the decoder 221, the prior value of the transmission information bits is set to “1/2” (log likelihood is 0). As a result, the external value and the posterior value of the transmission information bit are calculated. However, generally at this stage, only the external value is used for the next processing.

  The external value output from the decoder 221 is interlaced by the interleaver 231 and then input to the decoder 222 as a prior value. Also, the channel values of both the transmission information bit and the parity bit a2 are input from the channel value generator 202-2 to the decoder 222. Here, the channel value of the transmission information bits is input to the decoder 222 after being interlaced by the interleaver 232, similarly to the external value after the output of the decoder 221. The decoder 222 outputs the external value and the posterior value of the transmission information bit as a result of the decoding process. The posterior value after output from the decoder 222 is subjected to bit determination and output as received data (received information bits).

  The external value output from the decoder 222 is input to the decoder 221 as a prior value after being inversely interlaced by the deinterleaver 241. Thereby, the arithmetic processing is executed again from the decoder 221.

  Further, the a posteriori value after output from the decoder 222 is inversely interlaced by the inverse interleaver 242, and then input to the channel value generation unit 202-1 as the prior value of the modulation symbol bit. As a result, the channel value to be used at the time of execution of the re-calculation process from the decoder 221 is updated by reflecting the prior value of the modulation symbol bit by the channel value generator 202-1. It can be expected that the accuracy is improved over the previous channel value.

  In addition, the channel value generation unit 202-2 updates the channel value input to the decoder 222 using the posterior value after the output of the decoder 221 as the prior value. Thereby, the channel value delivered to the decoder 222 can be updated using the certainty of the transmission information bits obtained by the decoder 221, and the accuracy of the channel value input to the decoder 222 is improved. Is possible.

  According to the receiving apparatus to which the twin turbo decoder is applied, the performance of error correction is improved and the transmission characteristics can be further improved.

[Example of application of LDPC code]
FIG. 7 is a block diagram showing a configuration of an embodiment in which the LDPC decoder 2200 is applied to the receiving apparatus shown in FIG. Note that the configuration of the LDPC decoder 2200 itself is well known.

  In the receiving apparatus illustrated in FIG. 7, the channel value generation unit 202 includes symbol likelihoods h (0), h (1), h (2), h (3), h after output of the symbol likelihood calculation unit 201. '(0), h' (1), h '(2), h' (3) are input. The channel value generation unit 202 has symbol likelihoods h (0), h (1), h (2), h (3), h ′ (0), h ′ (1), h ′ (2), Based on h ′ (3) and the mapping pattern for each received symbol supplied from the mapping pattern sharing unit 204, soft decision data (communication channel value) for each bit of the modulation symbol is output. The channel value is input to the LDPC decoder 2200.

  The LDPC decoder 2200 repeatedly calculates the posterior value as in the case of the turbo code described above. Typical examples of the decoding algorithm are Min Sum and Sum Product. The iterative calculation is performed until the decoding result becomes a correct codeword or a predetermined number of iterations is reached.

  In the LDPC decoder 2200, first, the row direction calculation unit 2201 performs row direction calculation on the input channel value and outputs a prior value (or external value). When performing the row direction calculation, an external value (or a prior value) input from the column direction calculation unit 2203 is referred to. The codeword estimator 2202 performs codeword estimation based on the channel value after direct output from the demodulator 12a and the prior value (or external value) after output from the row direction calculator 2201, and outputs a posterior value. The column direction calculation unit 2203 performs row direction calculation based on the determination result of the maximum iteration number determination unit 2213 and outputs an external value (or a prior value).

  The bit determination unit 2211 performs bit determination based on the input posterior value. The code checker 2212 determines whether or not the code check is successful based on the result of the bit determination. If the code check passes, the result of bit determination is output as received data (received information bits). On the other hand, if the code check fails, the maximum iteration number determination unit 2213 determines whether the number of iterations in the LDPC decoder 2200 has reached the maximum number of iterations. When the maximum number of repetitions is reached, the result of this bit determination is output as reception data (reception information bits). On the other hand, if the maximum number of iterations has not been reached, the LDPC decoder 2200 is instructed to repeat.

  Further, the posterior value after output from the codeword estimation unit 2202 is fed back to the channel value generation unit 202 as the prior value of the bits of the modulation symbol. As a result, the next communication channel value from the communication channel value generation unit 202 is updated by reflecting the prior value of the bit of the modulation symbol, and the accuracy is improved over the previous communication channel value. Can be expected. As a result, the error correction performance is improved, and the transmission characteristics can be further improved.

  When using a demodulation method that updates the channel value for each iteration, such as the above-described twin turbo decoder and LDPC decoder, by creating a mapping pattern so as to produce a synergistic effect, a larger transmission characteristic can be obtained. Can be improved.

[Second Embodiment]
In the second embodiment, as in the first embodiment described above, a transmission system that transmits all or a part of transmission information by duplication (repetition) technology and further performs code spreading multiplexing and multicarrier transmission is taken as an example. I will explain.
FIG. 8 is a block diagram showing a configuration of a transmission apparatus according to the second embodiment of the present invention. In FIG. 8, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  In the transmission apparatus illustrated in FIG. 8, the spreading and multiplexing unit 111 includes two transmission symbol groups “c (0), c (1), c (2), c (3)”, “c ′” output from the mapping unit 103a. (0), c ′ (1), c ′ (2), c ′ (3) ”are code-spread multiplexed with a spreading code for each symbol group, and two transmission symbol groups“ d (0) ”after the code spread multiplexing , D (1), d (2), d (3) "," d '(0), d' (1), d '(2), d' (3) "are output. In the code spread multiplexing process, an arithmetic expression represented by Expression (2) is used.

However, w ₀₀ , w ₀₁ , w ₁₀ and w ₁₁ are spreading codes. Note that the type of spreading code is not particularly limited.

  Each transmission symbol group `` d (0), d (1), d (2), d (3) '', `` d '(0), d' (1), d '(2), d' (3) "Is arranged on each subcarrier for each symbol group by the inverse fast Fourier transform (IFFT) unit 112, and is transmitted in multicarrier.

  In the mapping unit 103a according to the present embodiment, a modulation scheme that performs mapping to a modulation symbol in which a plurality of bits are arranged is used. Unlike the above-described first embodiment, the modulation scheme is a multi-level modulation scheme. It is not limited to. This is because the I channel and the Q channel are not independent by performing code spread multiplexing transmission. Thereby, the transmission characteristic can be improved by using the same mapping pattern as that of the first embodiment. Note that examples of modulation schemes for mapping to modulation symbols in which a plurality of bits are arranged include 16QAM, QPSK (Quadrature Phase Shift Keying, Quadri-Phase Shift Keying), and the like.

  As for the receiving apparatus, the receiving function of the conventional multicarrier code spread multiplex transmission may be provided in the receiving apparatus of the first embodiment described above.

[Third Embodiment]
In the third embodiment, a transmission system that retransmits all or part of transmission information using HARQ technology will be described as an example.
FIG. 9 is a block diagram showing a configuration of a transmission apparatus according to the third embodiment of the present invention. In FIG. 9, parts corresponding to those in FIG. 1 are given the same reference numerals, and explanation thereof is omitted.

  In the transmission apparatus shown in FIG. 9, the codeword string “b (0) b (1)... B (15)” output from encoding section 101 is input to mapping section 103 and stored in buffer 121. . The buffer 121 outputs all or part of the stored codeword string “b (0) b (1)... B (15)” for retransmission in accordance with the retransmission command.

  The mapping unit 103 according to the present embodiment uses a multi-level modulation method as in the first embodiment. Then, in accordance with the mapping pattern supplied from the mapping pattern sharing unit 104, the mapping unit 103 normally uses the mapping pattern (mapping rule 1) at the time of creating the first transmission symbol in FIG. c (1), c (2), c (3) "are created, and at the time of retransmission, the transmission symbol group transmission symbol group" c '( 0), c ′ (1), c ′ (2), c ′ (3) ”. Thereby, the transmission characteristics can be improved as in the first embodiment.

  As for the receiving apparatus, the conventional retransmission control function may be provided in the receiving apparatus of the first embodiment described above.

[Fourth Embodiment]
In the fourth embodiment, as in the third embodiment, all or part of transmission information is retransmitted by the HARQ technique, and in addition, code spread multiplexing and multicarrier transmission are performed as in the second embodiment. The system will be described as an example.
FIG. 10 is a block diagram showing a configuration of a transmission apparatus according to the fourth embodiment of the present invention. In FIG. 10, parts corresponding to those in FIGS. 1, 8, and 9 are given the same reference numerals, and the description thereof is omitted.

  In the transmission apparatus shown in FIG. 10, the buffer 121 shown in FIG. 9 is provided to support retransmission control, and the spread multiplexing unit 111 and the IFFT unit 112 shown in FIG. 8 are provided to perform code spread multiplexing and multicarrier transmission. I am doing so. The mapping unit 103a according to the present embodiment uses a modulation scheme that performs mapping to a modulation symbol in which a plurality of bits are arranged, as in the second embodiment described above, but is similar to the second embodiment. For this reason, the modulation method is not limited to the multilevel modulation method. Thereby, the transmission characteristic can be improved by using the same mapping pattern as that of the third embodiment.

  As for the receiving apparatus, a receiving function and a retransmission control function of the conventional multicarrier code spread multiplexing transmission may be provided in the receiving apparatus of the first embodiment described above.

  According to each embodiment described above, in the repetition scheme and retransmission control scheme, which are schemes for creating a plurality of transmission symbols, based on the same transmission information, using transmission information that has already been used once to create a transmission symbol, When a transmission symbol is created after the second time, bit mapping to a modulation symbol is performed at least once with a combination of bits different from that at the time of other creation. As a result, the number of bits that affect the reliability can be increased during demodulation, so that a large diversity effect can be obtained. As a result, there is an effect that a required signal-to-noise ratio (SNR) for achieving a predetermined error rate can be reduced.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, examples of the multi-level modulation method include the above-described 16QAM, 64QAM, and the like. In addition, as a modulation scheme that performs mapping to a modulation symbol in which a plurality of bits are arranged and is not a multi-level modulation scheme, for example, QPSK is cited.

  In the second and fourth embodiments described above, the transmission system that performs code spread multiplexing and multicarrier transmission has been described as an example. However, the transmission system that performs code spread multiplexing and single carrier transmission also includes the second and fourth embodiments described above. The present invention can be applied similarly to the fourth embodiment. In other words, a modulation scheme that performs mapping to a modulation symbol in which a plurality of bits are arranged can be used as long as it performs code spread multiplexing even for single carrier transmission, and the same effect can be obtained. is there.

  Note that the transmission device and the reception device according to the present invention can be applied to both a wireless transmission system and a wired transmission system. Further, it can be applied to various transmission systems such as communication and broadcasting.

It is a block diagram which shows the structure of the transmitter which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the receiver which concerns on the same embodiment. It is a block diagram which shows the structure of the communication path value production | generation part 202 which concerns on the same embodiment. It is a figure which shows an example of the mapping pattern which concerns on the same embodiment. It is a block diagram which shows the structure of a turbo encoder. FIG. 3 is a block diagram showing a configuration of an embodiment in which a twin turbo decoder is applied to the receiving apparatus shown in FIG. 2. 3 is a block diagram showing a configuration of an embodiment in which an LDPC decoder 2200 is applied to the receiving apparatus shown in FIG. It is a block diagram which shows the structure of the transmitter which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the transmitter which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structure of the transmitter which concerns on 4th Embodiment of this invention. It is a figure which shows the constellation pattern of 16QAM. It is a figure which shows an example of the conventional mapping pattern. It is a figure which shows the other example of the conventional mapping pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Coding part, 102 ... Repetition part, 103, 103a ... Mapping part, 104, 204 ... Mapping pattern sharing part, 111 ... Spreading multiplexing part, 112 ... Inverse fast Fourier transform (IFFT) part, 121 ... Buffer, 201 ... Symbol likelihood calculation unit, 202 ... channel value generation unit, 203 ... decoding unit, 211, 212 ... channel value calculation unit, 213 ... adder

Claims (12)

In a transmission apparatus that duplicates or retransmits all or part of transmission information,
Modulation means for mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component and creating a transmission symbol;
Mapping pattern sharing means for sharing a mapping pattern used for the mapping with a receiving device,
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A transmission apparatus characterized by the above. In a transmission apparatus that performs duplicate transmission or re-transmission of all or part of transmission information and code spread multiplexing,
Modulation means for mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged to create a transmission symbol;
Mapping pattern sharing means for sharing a mapping pattern used for the mapping with a receiving device,
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A transmission apparatus characterized by the above.   The transmission apparatus according to claim 1, further comprising an encoding unit configured to perform error correction encoding on the transmission information.   The transmission apparatus according to claim 3, wherein the error correction code is a turbo code.   The transmission apparatus according to claim 3, wherein the error correction code is a low density parity check code. A transmission symbol is created by mapping bits in transmission information to a modulation symbol in which a plurality of bits are arranged in the in-phase component or the quadrature component, and all or a part of the transmission information is transmitted from a transmitter that performs redundant transmission or retransmission. In the receiving device for receiving the transmission symbol,
Symbol likelihood calculating means for calculating the symbol likelihood of each received symbol;
Mapping pattern sharing means for sharing a mapping pattern used for the mapping with the transmission device;
Demodulation means for determining transmission information transmitted from the transmission device based on the mapping pattern and symbol likelihood for each received symbol;
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A receiving apparatus. A bit in transmission information is mapped to a modulation symbol in which a plurality of bits are arranged to create a transmission symbol, and all or a part of the transmission information is redundantly transmitted or retransmitted and transmitted from a transmitter that performs code spread multiplexing. In the receiving apparatus for receiving the transmitted symbol,
Symbol likelihood calculating means for calculating the symbol likelihood of each received symbol;
Mapping pattern sharing means for sharing a mapping pattern used for the mapping with the transmission device;
Demodulation means for determining transmission information transmitted from the transmission device based on the mapping pattern and symbol likelihood for each received symbol;
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A receiving apparatus. Decoding means for decoding error correction coding applied to transmission information by the transmission device from the determination result of the demodulation means;
Means for feeding back the probability of the received signal obtained in the decoding process to the demodulation means,
The demodulation means uses the likelihood of the feedback signal received for the determination of the transmission information.
The receiving apparatus according to claim 6 or 7, characterized in that:   The receiving apparatus according to claim 8, wherein the error correction code is a turbo code.   The receiving apparatus according to claim 8, wherein the error correction code is a low density parity check code. A transmission method in which all or part of transmission information is duplicated or retransmitted,
A modulation process in which a transmission device creates a transmission symbol by mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged in an in-phase component or a quadrature component;
A mapping pattern sharing process in which a mapping pattern used for the mapping is shared between the transmitting device and the receiving device;
A symbol likelihood calculation process in which the receiving apparatus calculates a symbol likelihood of each received symbol;
A demodulation process for determining, based on the mapping pattern and symbol likelihood for each received symbol, the transmission information transmitted from the transmission device, the reception device;
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A transmission method characterized by the above. A transmission method in which all or part of transmission information is duplicated or retransmitted and code spread multiplexed,
A modulation process in which the transmission device creates a transmission symbol by mapping a bit in transmission information to a modulation symbol in which a plurality of bits are arranged;
A mapping pattern sharing process in which a mapping pattern used for the mapping is shared between the transmitting device and the receiving device;
A symbol likelihood calculation process in which the receiving apparatus calculates a symbol likelihood of each received symbol;
A demodulation process for determining, based on the mapping pattern and symbol likelihood for each received symbol, the transmission information transmitted from the transmission device, the reception device;
At least one mapping pattern at the time of duplicate transmission or retransmission is a combination of bits in transmission information mapped to the modulation symbol different from the mapping pattern at the time of other transmissions.
A transmission method characterized by the above.

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