JP2005269670A - Multicarrier transmitter, multicarrier receiver, and multicarrier transmitting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an error rate characteristic by retransmission upon multicarrier communication. <P>SOLUTION: A sequence converter 104 replaces the upper bits with lower bits, upper bits at which errors hardly occur and lower bits at which errors easily occur that are used by a multi-value modulation part 105, for every retransmission. In the multi-value modulation part 105, a multi-value modulation is performed by using the upper bits and the lower bits that are replaced for each retransmission. A symbol after the multi-value modulation is interleaved with different interleave patterns for each retransmission and transmitted by using multicarriers via a spreading part 108 and an OFDM transmission part 109. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multicarrier transmission apparatus, a multicarrier reception apparatus, and a multicarrier transmission method, and is particularly suitable when applied to a case where an error rate is reduced by packet combining retransmission signals.

  Conventionally, in this type of multi-carrier communication system, a packet obtained by initial transmission and a retransmitted packet are combined and decoded to improve the error rate characteristic at the time of decoding on the receiving side. . Conventionally, in order to improve the data throughput, various ideas have been proposed to achieve a desired error rate with a small number of retransmissions.

  In particular, in a multicarrier communication system, reception levels differ for each subcarrier due to frequency selective fading. Accordingly, the reception level of a signal superimposed on a subcarrier of a certain frequency increases, but the reception level of a signal superimposed on another subcarrier decreases. As a result, the error rate of a signal superimposed on a subcarrier with a low reception level does not readily reach a desired value, and the number of retransmissions increases.

Conventionally, there are methods disclosed in Patent Documents 1 and 2, etc., paying attention to this point. In these methods, by changing the interleave pattern for each retransmission, the subcarrier in which the symbol is arranged is changed for each retransmission. As a result, the signal level of each symbol at the time of packet synthesis can be made uniform, and the error rate characteristic can be improved.
JP 2001-60934 A JP 2000-269929 A

  By the way, according to the conventionally proposed method of changing the interleave pattern for each retransmission, it is possible to increase the variation of transmission symbols by interleaving processing, so it is possible to reduce symbols with extremely bad error rate and effectively Throughput can be improved.

  However, in recent years, there has been a demand for transmitting large amounts of data such as image data at high speed. To achieve this, the error rate characteristics are further improved and the number of retransmissions is further reduced to further improve the throughput. It is necessary to make it.

  The present invention has been made in view of such points, and an object of the present invention is to provide a multicarrier transmission apparatus, a multicarrier reception apparatus, and a multicarrier transmission method that can further improve error rate characteristics due to retransmission in a multicarrier communication system. And

  In order to solve this problem, the present invention adopts the following configuration.

  (1) The multicarrier transmission apparatus of the present invention is a multi-level modulation unit that modulates transmission data of 3 bits or more into one symbol, and an upper bit and a lower bit when performing modulation processing by the multi-level modulation unit for each retransmission. It adopts a configuration comprising bit replacement means for replacement, and multicarrier transmission means for transmitting the symbols obtained by the multi-level modulation means superimposed on a plurality of subcarriers.

  According to this configuration, since the lower bits that are likely to cause errors in the previous transmission are the higher bits that are less likely to cause errors in the next transmission (retransmission), the quality of the lower bits when the receiving side demodulates the modulation symbols. Is avoided continuously worsening. As a result, a time diversity effect by retransmission is obtained for each bit, and the error rate of the combined packet data is improved.

  (2) The multicarrier transmission apparatus according to the present invention employs a configuration in (1) further including an interleaver that interleaves bits before multi-level modulation with different interleave patterns for each retransmission.

  According to this configuration, the bits constituting one symbol of multi-level modulation are different for each retransmission, so even if the reception level of the same symbol is low in the previous transmission and the next transmission (retransmission), the same The probability that the reception level of bits continuously decreases can be reduced. As a result, the time diversity effect due to retransmission for each bit can be further enhanced, and the error rate characteristics of the combined packet data are further improved.

  (3) The multicarrier transmission apparatus of the present invention employs a configuration in which the interleaver of (2) interleaves the upper bits and the lower bits with independent interleave patterns for each retransmission.

  According to this configuration, the bits constituting one symbol of multi-level modulation are varied for each higher-order bit and lower-order bit for each retransmission, so that the reception level of the same symbol is low in the previous transmission and the next transmission (retransmission). Even if this happens, the probability that the reception level of the same bit is lowered can be reduced, and each bit string can be easily restored on the reception side. In other words, on the transmitting side, it is possible to reliably replace the upper bits and the lower bits and interleave each bit, and on the receiving side, simply perform the reverse process to restore the original bit string. Become.

  (4) In the multicarrier transmission apparatus of the present invention, in (1), the bit separation means for separating transmission data composed of one system bit string into two systems of bit strings, and the separated bit strings of each system for each retransmission A plurality of interleavers for interleaving with different interleave patterns, and a multiplexing means for changing the order of each interleaved bit sequence for each retransmission and time-division multiplexing. The multi-level modulation means is multiplexed by the multiplexing means. A configuration for modulating a bit string is adopted.

  According to this configuration, without changing the configuration of the constellation mapping of the multi-level modulation means, processing such as exchanging upper bits and lower bits for each retransmission and exchanging bits constituting one symbol for each retransmission is easily performed. Will be able to.

  (5) The multicarrier transmission apparatus of the present invention further includes detection means for detecting the reception level of each subcarrier in (2) to (4), and the interleaver receives signals based on the detection results. A configuration is adopted in which an interleave pattern is selected so that the same bit is not arranged in a subcarrier with a low level.

  According to this configuration, it is possible to reliably avoid the reception level of the same bit continuously lowering in the previous transmission and the next transmission (retransmission).

  (6) The multicarrier transmission apparatus of the present invention further includes an interleaver that interleaves the symbols obtained by the multi-level modulation means with different interleave patterns for each retransmission in (1) to (4). The transmission means adopts a configuration in which interleaved symbols are transmitted by being superimposed on a plurality of subcarriers.

  According to this configuration, it is possible to avoid lowering the reception level of the same symbol in the previous transmission and the next transmission (retransmission), so that compared to the cases (1) to (4), The probability that the reception level continuously decreases further decreases.

  (7) The multicarrier receiver of the present invention is a multicarrier receiver that receives and demodulates the multicarrier signal transmitted from the multicarrier transmitter of (2), and extracts transmission symbols from the received multicarrier signal. Symbol extraction means, demodulation means for restoring transmission bits by softly determining the extracted symbols, and interleaving processing opposite to the interleaver of (2) for each retransmission of the bit string obtained by the demodulation means A deinterleaver to be applied; (2) a bit rearranging unit that restores the bit sequence replaced by the exchanging unit; and a combining unit that performs packet synthesis for each retransmission using the restored bit sequence Take.

  According to this configuration, it is possible to restore the original transmission data satisfactorily by returning the bits that have been bit interleaved for each retransmission on the transmission side and in which the upper bits and the lower bits are switched to the original order.

  (8) The radio base station apparatus of the present invention employs a configuration including the multicarrier transmission apparatus according to any one of (1) to (6).

  (9) A communication terminal apparatus according to the present invention employs a configuration including the multicarrier transmission apparatus according to any one of (1) to (6).

  (10) In the multicarrier transmission method of the present invention, a multilevel modulation step for modulating transmission data of 3 bits or more into one symbol, and an upper bit and a lower bit when performing modulation processing in the multilevel modulation step for each retransmission A bit exchanging step for exchanging and a multi-carrier transmitting step for transmitting the symbols obtained in the multi-level modulation step superimposed on a plurality of subcarriers are included.

  According to this method, since the lower bits that are likely to cause errors in the previous transmission are made higher bits that are less likely to cause errors in the next transmission (retransmission), the quality of the lower bits when the modulation symbol is demodulated on the receiving side. Is avoided continuously worsening. As a result, a time diversity effect by retransmission is obtained for each bit, and the error rate of the combined packet data is improved.

  (11) In addition to the step of (10), the multicarrier transmission method of the present invention further includes a step of interleaving bits before multi-level modulation with different interleave patterns for each retransmission.

  According to this method, the bits constituting one symbol of multilevel modulation are different for each retransmission, so even if the reception level of the same symbol is low in the previous transmission and the next transmission (retransmission), the same The probability that the reception level of bits continuously decreases can be reduced. As a result, the time diversity effect due to retransmission for each bit can be further enhanced, and the error rate characteristics of the combined packet data are further improved.

  (12) The program of the present invention causes a computer to perform a multi-level modulation procedure for modulating transmission data of 3 bits or more into one symbol, and an upper bit and a lower bit when performing modulation processing in the multi-level modulation procedure for each retransmission. A bit replacement procedure for replacement and a multicarrier transmission procedure for transmitting a symbol obtained by the multi-level modulation procedure superimposed on a plurality of subcarriers are performed.

  As described above, according to the present invention, when multi-level modulation is performed on transmission data and the modulated symbol is subjected to multi-carrier transmission, the high-order bit that is unlikely to cause an error and the low-order bit that is not likely to cause an error are exchanged for each retransmission. A multi-carrier transmission apparatus capable of improving error rate characteristics due to retransmission by performing multi-level modulation and performing bit interleaving so that bits constituting one symbol of multi-level modulation differ for each retransmission, A multicarrier receiver and a multicarrier transmission method can be realized.

  The essence of the present invention is that when multi-level modulation is performed on transmission data and the modulated symbol is transmitted by multi-carrier, the high-order bit that is not likely to cause an error and the low-order bit that is likely to cause an error are exchanged for each retransmission. It is to apply modulation. In addition, bit interleaving processing is performed so that bits constituting one symbol of multilevel modulation differ for each retransmission.

  As a result, even if the reception level of the same symbol is low in the previous transmission and the next transmission (retransmission), the probability that the reception level of the same bit continuously decreases is low, and time diversity due to retransmission on the reception side is reduced. The effect can be enhanced. As a result, it is possible to improve the error rate characteristics after packet combination on the receiving side, thereby reducing the number of retransmissions and improving the data throughput.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In FIG. 1, reference numeral 100 generally indicates the configuration of the multicarrier transmission apparatus according to Embodiment 1 of the present invention. Multicarrier transmission apparatus 100 is provided in a radio base station apparatus or a communication terminal apparatus. Multicarrier transmission apparatus 100 performs multilevel modulation processing on transmission data, spreads symbols obtained by modulation, and transmits chips obtained by spreading on a plurality of subcarriers orthogonal to each other. That is, the multicarrier transmission apparatus 100 according to this embodiment transmits transmission data by an OFDM (Orthogonal Frequency Division Multiplexing) -CDMA (Code Division Multiple Access) system.

  Multicarrier transmission apparatus 100 encodes transmission data by encoding section 101 and sends the encoded data to storage section 102. The storage unit 102 is controlled to read based on the count value of the counter 103. Here, the counter 103 increments the count value every time a NACK signal (retransmission request signal) is sent from the receiving side, and resets the count value to 0 when the ACK signal is sent. The storage unit 102 sends the stored data to the sequence conversion unit 104 every time the count value is incremented (that is, sends retransmission data). On the other hand, when the count value becomes 0, the data from the encoding unit 101 is sent to the sequence conversion unit 104 as it is (that is, the initial transmission data is sent).

  Each time the count value from the counter 103 is incremented, the series conversion unit 104 changes the order of the higher-order bits that are less likely to cause errors and the lower-order bits that are likely to cause errors, which are modulated by the subsequent multi-level modulation unit 105.

  Multi-level modulation section 105 modulates a plurality of bits of data input from sequence conversion section 104 into one symbol. In the case of this embodiment, the multi-level modulation section 105 performs 16 QAM (Quadrature Amplitude Modulation) on the input data and modulates 4 bits into one symbol.

  Processing of the sequence conversion unit 104 and the multilevel modulation unit 105 will be described with reference to FIG. Here, FIG. 2A shows an arrangement of bits input to the series conversion unit 104. FIG. 2B shows an arrangement of bits constituting each symbol at the first transmission. FIG. 2C shows an arrangement of bits constituting each symbol at the time of retransmission (at the first retransmission). FIG. 2D shows an arrangement of bits output from the sequence conversion unit 104 at the time of retransmission (at the first retransmission).

  Here, in FIGS. 2B and 2C, b0 and b1 indicate high-order bits that are unlikely to cause errors when 16QAM modulation is performed, and b2 and b3 indicate low-order bits that are likely to generate errors. As can be seen from FIG. 2, the higher-order bits and the lower-order bits are switched by the sequence conversion unit 104 between the initial transmission and the retransmission. For example, looking at the symbol with symbol number 1, the first and second bits are the upper bits and the third and fourth bits are the lower bits (FIG. 2 (B)) at the first transmission, whereas three and four bits are at the time of retransmission. Bits are upper bits and 1, 2 bits are lower bits (FIG. 2C).

  The symbol after multilevel modulation is input to the selection circuit 106. A plurality of interleavers 107-1, 107-2,..., 107 -N having different interleave patterns are connected to the output side of the selection circuit 106. The selection circuit 106 switches between the interleavers 107-1, 107-2,..., 107-N for inputting modulation symbols according to the count value from the counter 103. As a result, symbols with different arrangement orders are sent to the spreading unit 108 for each retransmission.

  The spreading unit 108 spreads the symbols on a chip basis by multiplying the input symbols by a spreading code. The OFDM transmitter 109 is configured by an IFFT (inverse Fourier transform circuit), a radio transmitter circuit, and the like, and superimposes chips obtained by spreading on a plurality of subcarriers orthogonal to each other. The signal after the OFDM transmission processing is transmitted via the antenna 110.

  FIG. 3 shows a configuration of multicarrier receiving apparatus 200 that receives a multicarrier signal transmitted by multicarrier transmitting apparatus 100. Multicarrier receiving apparatus 200 inputs a received signal to OFDM receiving section 202 via antenna 201.

  The OFDM receiving unit 202 includes a wireless receiving unit, an FFT (Fourier transform circuit), and the like, and extracts each chip superimposed on a plurality of subcarriers. Despreading section 203 despreads the input signal using the spreading code to restore the symbols before spreading, and sends the restored symbols to selection circuit 204.

  A plurality of deinterleavers 206-1, 206-2,..., 206-N having different interleave patterns are connected to the output side of the selection circuit 204. Each of the deinterleavers 206-1, 206-2,..., 206-N performs processing opposite to that of the transmitting side interleavers 107-1, 107-2,..., 107-N (FIG. 1). Each symbol is returned to the original arrangement.

  The selection circuit 204 selects the deinterleavers 206-1, 206-2,..., 206-N that output input signals according to the count value of the counter 205. Here, the counter 205 is incremented every time a NACK signal is inputted, as in the counter 103 on the transmission side (FIG. 1). That is, between the multicarrier transmission apparatus 100 and the multicarrier reception apparatus 200, corresponding interleavers 107-1, 107-2, ..., 107-N (FIG. 1) and deinterleaver 206- correspond to the number of retransmissions. 1, 206-2,..., 206-N are selected, and the symbol arrangement is restored by the deinterleavers 206-1, 206-2,.

  The symbols returned to the original arrangement by the deinterleavers 206-1, 206-2,..., 206-N are input to the multilevel demodulation unit 207. The multilevel demodulator 207 demodulates 4-bit data from one symbol by performing a demodulation process corresponding to the multilevel modulator 105 (FIG. 1).

  The sequence conversion unit 208 performs sequence conversion opposite to that of the transmission side sequence conversion unit 104 (FIG. 1) according to the number of retransmissions. Specifically, the input bits are output in the same arrangement when receiving the initial transmission data, while the arrangement of the upper bits and the lower bits is exchanged for each retransmission when the retransmission signal is received. Thereby, a signal having the same bit arrangement as that of the transmission data is obtained. The output of sequence conversion section 208 is input to combining circuit 209 that combines retransmission packets.

  The synthesizing circuit 209 includes a storage unit 211 and an addition unit 210, and the packet data until the current retransmission stored in the storage unit 211 and the packet data retransmitted this time are added by the addition unit 210. For example, when the packet data input this time is packet data by the second retransmission, the combined packet data by the first and first retransmissions stored in the storage unit 211 and the packet data by the current retransmission are combined. The

  The combined packet data is decoded by the decoding unit 212, and error detection such as CRC (Cyclic Redundancy Check) is performed by the error detection unit 213. As a result, the error detection unit 213 outputs decoded data, and outputs an ACK signal when the CRC is OK, and a NACK signal when the CRC is NG. The ACK / NACK signal is transmitted to the counter 205 and also transmitted to the multicarrier transmission apparatus 100 (FIG. 1).

  Next, the operation of this embodiment will be described. In this embodiment, the multicarrier transmission apparatus 100 replaces the upper bit and the lower bit at the time of multi-level modulation for each retransmission, so that the error rate in bit units on the receiving side can be improved. become. First, this will be described with reference to FIGS. 4, 5 and 6.

FIG. 4 shows a mapping position on the IQ plane of each symbol by 16QAM. At the time of demodulation, soft decision processing is performed on the upper 2 bits by using the determination threshold value of width i _{1 in} the figure for the in-phase component and the determination threshold value of width q _{1 in} the figure for the quadrature component. On the other hand, the lower 2 bits are subjected to soft decision processing using the determination threshold value of width i ₂ for the in-phase component and the determination threshold value of width q ₂ for the quadrature component. As is apparent from the figure, since the lower two-bit decision threshold widths i ₂ and q ₂ are narrower than the upper two-bit decision threshold widths i ₁ and q ₁ , the symbol phase and amplitude depend on the propagation path. When it fluctuates, an error is likely to occur compared to the upper 2 bits.

  FIG. 5 shows the relationship between the SIR (Signal to Interference Ratio) and the BER (Bit Error Rate) of the upper 2 bits S0 and S1 and the lower 2 bits S2 and S3. As is apparent from the figure, the BER is lower for the upper bits if the SIR is the same.

  In this embodiment, as shown in FIG. 6, the bits S0 and S1 are transmitted as high-order bits at high quality during the first transmission, and the bits S2 and S3 are high-order bits as high-order bits at the second transmission (during retransmission). It is trying to transmit with. As a result, when packets are combined on the receiving side, all bits S0 ', S1', S2 ', and S3' can be restored with a quality that does not cause an error.

  In other words, compared with the case where the lower bit is transmitted as the lower bit at the time of initial transmission, the time diversity effect in units of bits by retransmission is obtained, and the error rate characteristic of the combined packet data is improved. be able to.

  Further, in this embodiment, since the multi-level modulated symbols are interleaved by different interleave patterns for each retransmission and are transmitted by multicarrier, it is possible to improve the error rate characteristics in symbol units. In other words, even if the signal level of a specific subcarrier falls due to frequency selective fading, the probability that the same symbol is continuously assigned to that subcarrier is low, so a time diversity effect in units of bits by retransmission can be obtained, The error rate characteristics of the combined packet data can be further improved.

  According to the above configuration, when multi-level modulation is performed on transmission data and the modulated symbol is transmitted by multi-carrier, the high-order bit and the low-order bit are switched for each retransmission to perform multi-level modulation. Thus, it is possible to obtain a time diversity effect by retransmission for each bit and to improve the error rate characteristics of the packet data after combining. As a result, the number of retransmissions can be reduced, so that the data throughput can be improved.

(Embodiment 2)
In this embodiment, as in the first embodiment, in addition to performing multilevel modulation by exchanging upper bits and lower bits for each retransmission, bits assigned to upper bits and lower bits in multilevel modulation are assigned. The bits are divided, and an interleave process is performed on each divided bit string using a different interleave pattern for each retransmission.

  As a result, in addition to the high-order bits and the low-order bits being exchanged for each retransmission, the bits constituting one symbol by multi-level modulation are also exchanged for each retransmission. As a result, when viewed between retransmissions, each bit can be separated one step (that is, the probability that the same bit is allocated to the same subcarrier for each retransmission) can be reduced. The time diversity effect can be further enhanced.

  In FIG. 7 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, the multicarrier transmission apparatus 300 of this embodiment separates transmission bits output from the storage unit 102 by a separation unit 301. In this embodiment, since 16QAM is performed with 4 bits as one symbol, input bits are separated every 2 bits. Specifically, as illustrated in FIG. 8, the separation unit 301 separates the input bits every two bits into the separation unit output 1 and the separation unit output 2 and supplies them to each input terminal of the subsequent selection circuit 302.

  The output terminal of the selection circuit 302 is connected to interleavers 303-1 and 302-2 having different interleave patterns through movable contacts. The selection circuit 302 selects the interleavers 303-1 and 302-2 that supply the input bit string in accordance with the count value (that is, the number of retransmissions) from the counter 305. For example, at the time of initial transmission, the separation unit output 1 shown in FIG. 8 is supplied to the interleaver 303-1, and the separation unit output 2 is supplied to the interleaver 303-2. On the other hand, at the first retransmission, the separation unit output 1 is supplied to the interleaver 303-2, and the separation unit output 2 is supplied to the interleaver 303-1.

  The outputs of the interleavers 303-1 and 302-2 are supplied to the input terminals of the subsequent selection circuit 304. The output terminal of the selection circuit 304 is connected to two input terminals of the multiplexing unit 306 via a movable contact. The selection circuit 304 switches the input terminal of the multiplexing unit 306 that supplies the outputs of the interleavers 303-1 and 302-2 according to the count value (that is, the number of retransmissions) from the counter 305.

  Here, the multiplexing unit 306 converts the two bit strings input from the two input terminals into a single bit sequence by time-division multiplexing and outputs the result. At this time, the two bits supplied to the first input terminal are output first, and then the two bits supplied to the second input terminal are output, so that two bits are selected alternately. Output.

  The state of input and output of the multiplexing unit 306 will be described with reference to FIG. At the first transmission, 1, 2, 5, 6,..., N0, n1 are input to the first input terminal as the multiplexer input 1, and 3, 4, 7, 8,. ..., n2, n3 are input. At this time, the multiplexing unit 306 outputs a bit string in the order of 1, 2, 3, 4, 5, 6, 7, 8,..., N0, n1, n2, and n3 as the multiplexing unit output.

  On the other hand, although not shown, at the time of retransmission, 3, 4, 7, 8,..., N2, n3 are input to the first input terminal as the multiplexing unit input 1, and 1, 2 as the multiplexing unit input 2 to the second input terminal. , 5, 6,..., N0, n1 are input. At this time, the multiplexing unit 306 outputs a bit string in the order of 3, 4, 1, 2, 7, 8, 5, 6,..., N2, n3, n0, n1 as a multiplexing unit output (however, in FIG. In order to simplify the above, the bit arrangement ignores the interleaving process by the interleavers 303-1, 302-2, but each bit is actually interleaved).

  As a result, multi-level modulation section 105 can perform multi-level modulation processing in which the upper bits and lower bits are interchanged at the time of initial transmission and retransmission, so that the lower bit reception quality is prevented from continuously worsening. An effect similar to that of the first embodiment can be obtained.

  FIG. 10 shows an arrangement of bits actually output from the multiplexing unit 306. As is clear from this figure, in the initial transmission shown in FIG. 10 (A) and the retransmission shown in FIG. 10 (B), in addition to the upper bits and the lower bits being switched, The assigned bits are also swapped. As a result, for example, even when each symbol is assigned to the same subcarrier at the time of initial transmission and at the time of retransmission, each bit is allocated to a different subcarrier at the time of initial transmission and at the time of retransmission. The time diversity effect due to can be obtained with certainty.

  Here, the reason why the error rate characteristic is improved by changing the subcarrier in which bits are arranged at the time of initial transmission and at the time of retransmission will be briefly described with reference to FIG. When the same interleave pattern # 1 is used at the time of initial transmission and at the time of retransmission, the same data is arranged on the same subcarrier at the time of initial transmission and at the time of retransmission, so the initial transmission signal and the retransmission signal are combined. Even so, the data allocated to the subcarriers whose reception level has dropped due to frequency selective fading hardly obtains the diversity effect due to retransmission. Data 2 and 7 indicated by x in the figure correspond to this.

  On the other hand, when the same different interleave patterns # 1 and # 2 are used for the first transmission and the retransmission, the same data is arranged in different subcarriers for the first transmission and the retransmission. When the initial transmission signal and the retransmission signal are combined, there is a high possibility that data that cannot be obtained with a sufficient reception level in the first transmission can be obtained with a sufficient reception level in the second transmission. As a result, a diversity effect by retransmission can be obtained. Data 2 and 7 indicated by ○ in the figure correspond to this.

  FIG. 12 shows a configuration of multicarrier receiving apparatus 400 that receives and demodulates a signal transmitted from multicarrier transmitting apparatus 300 (FIG. 7). In FIG. 12, in which parts corresponding to those in FIG. 3 are assigned the same reference numerals, the multicarrier receiving apparatus 400 inputs the despread signal to the multilevel demodulation section 401. Here, the multilevel demodulation unit 401, the separation unit 402, the selection circuit 403, the deinterleavers 404-1, 404-2, the selection circuit 405, and the multiplexing unit 406 basically correspond to the corresponding parts of the multicarrier transmission device 300. The reverse process is performed.

  Specifically, the multilevel demodulator 401 is the multilevel modulator 107, the demultiplexer 402 is the multiplexer 306, the selector 403 is the selector 304, and the deinterleavers 404-1, 404-2 are the interleaver 303. -1, 303-2, the selection circuit 405, the selection circuit 302, the multiplexing unit 406, and the separation unit 301, respectively. Thereby, the multiplexing unit 406 restores and outputs a bit string similar to the bit string input to the separation unit 301 (FIG. 7) except for transmission degradation.

  According to the above configuration, in addition to exchanging the upper and lower bits of multi-level modulation for each retransmission, the subcarriers in which bits are arranged by interleaving the upper and lower bits with a different interleave pattern for each retransmission. By replacing each retransmission, in addition to the effect in the first embodiment, the time diversity effect by retransmission can be further enhanced for each bit. As a result, the error rate characteristics after packet synthesis can be further improved.

  Further, by providing the separation unit 301, the selection circuit 302, the interleavers 303-1, 303-2, the selection circuit 304, and the multiplexing unit 306, retransmission can be performed without changing the configuration of the constellation mapping of the multilevel modulation unit 107. It becomes possible to exchange the upper bit and the lower bit for each bit and the bits constituting one symbol for each retransmission. Thereby, it can be set as a simple apparatus structure.

(Embodiment 3)
In FIG. 13, in which parts corresponding to those in FIG. 7 are assigned the same reference numerals, the multicarrier transmission apparatus 500 of this embodiment interleaves the upper bits and lower bits separated by the separation unit 301 with independent interleave patterns. It is like that. As a result, the variation between the upper bits and the lower bits can be further increased as compared with the second embodiment, so that the time diversity effect due to retransmission can be further enhanced for each bit, and the improvement effect of the bit error rate characteristic due to retransmission can be further increased. It can be raised.

  More specifically, the upper bits and the lower bits separated by the separation unit 301 are input to the selection circuit 501 and distributed to the selection circuit 502 or the selection circuit 503 according to the count value of the counter 507 (that is, the number of retransmissions), respectively. . Interleavers 504-1, 504-2,..., 504-N having different interleave patterns are provided at the output terminal of the selection circuit 502, and interleavers having different interleave patterns are also provided at the output terminal of the selection circuit 503. 505-1, 505-2, ..., 505-N are provided.

  Then, the selection circuits 502 and 503, according to the count value of the counter 507, respectively, interleavers 504-1, 504-2,..., 504-N, 505-1, 505-2,. Switch N. As a result, the upper bits and the lower bits are interleaved with completely different interleave patterns for each retransmission.

  The interleaved upper bits and lower bits are input to the multiplexing unit 306 via the selection circuit 506. At this time, as described in the second embodiment, the selection unit 506 switches the upper bit and the lower bit input to the input terminal to the multiplexing unit 306 for each retransmission, so that the multilevel modulation unit 107 handles them. The upper bit and the lower bit are switched at each retransmission.

  FIG. 14 shows a configuration of multicarrier receiving apparatus 600 that receives and demodulates a signal transmitted from multicarrier transmitting apparatus 500. In FIG. 14, in which parts corresponding to those in FIG. 12 are assigned the same reference numerals, multicarrier receiving apparatus 600 inputs a signal after multilevel demodulation to demultiplexing section 402. Here, the separation unit 402, selection unit 601, selection unit 602, selection unit 603, deinterleavers 604-1, 604-2, ..., 604-N, deinterleavers 605-1, 605-2, ..., 605- N, the selection unit 606, and the multiplexing unit 607 basically perform the reverse process of the corresponding part of the multicarrier transmission apparatus 500.

  Specifically, the separation unit 402 is a multiplexing unit 306, the selection unit 601 is a selection unit 506, the selection unit 602 is a selection unit 502, the selection unit 603 is a selection unit 503, and deinterleavers 604-1 and 604-. 2, ..., 604-N are interleavers 504-1, 504-2, ..., 504-N, and deinterleavers 605-1, 605-2, ..., 605-N are interleavers 505-1, 505-N. 2,..., 505-N, the selection unit 606 performs the reverse processing of the selection unit 501, and the multiplexing unit 607 performs the reverse processing. Accordingly, the multiplexing unit 607 outputs a bit string similar to the bit string input to the separation unit 301 except for transmission degradation.

  According to the above configuration, in addition to the second embodiment, the higher bits and lower bits separated by the separation unit 301 are interleaved with independent interleave patterns, respectively, so that compared with the second embodiment, Since the variation between the upper bits and the lower bits can be further increased, the time diversity effect due to retransmission can be further enhanced for each bit. In other words, the bits constituting one symbol of multi-level modulation are varied for each higher-order bit and lower-order bit for each retransmission, so that the reception level of the same symbol is lowered in the previous transmission and the next transmission (retransmission). However, the probability that the reception level of the same bit is lowered can be lowered. As a result, the improvement effect of the bit error rate characteristic due to retransmission can be further enhanced.

  Further, by interleaving the upper bits and lower bits separated by the separation unit 301 with independent interleave patterns, each bit string can be easily restored on the receiving side. That is, on the receiving side, the original bit string can be restored by simply performing the reverse process of the transmitting side for each upper bit and lower bit.

(Other embodiments)
In the above-described first embodiment, the sequence conversion unit 104 is provided, so that the upper bit and the lower bit are switched at the time of multi-level modulation for each retransmission. In the second embodiment, the separation unit 301 and the interleaver 303 are replaced. -1, 303-2, selection unit 304, and multiplexing unit 306 have been described to perform different bit interleaving processes for each retransmission and perform replacement processing of upper bits and lower bits. However, the interleaver may be provided with a bit interleaving function and a function of exchanging upper bits and lower bits.

  For example, as shown in FIG. 15, a plurality of interleavers 701-1, 701-2,... Each having a function of switching upper bits and lower bits in multi-level modulation and having different interleave patterns. , 702-N can provide the same effects as those of the first and second embodiments.

  That is, in FIG. 15 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, multicarrier transmission apparatus 700 has a function of switching the upper bits and lower bits in multi-level modulation, and A plurality of interleavers 701-1, 701-2, ..., 702-N having different interleave patterns are provided. In the multicarrier transmission apparatus 700, the selection circuit 701 selects any one of interleavers 701-1, 701-2, ..., 702-N to which transmission data is supplied according to the number of retransmissions. As a result, the same effect as described in the first embodiment or the second embodiment can be achieved by the configuration as shown in FIG.

  Incidentally, the multicarrier signal transmitted from the multicarrier transmission apparatus 700 shown in FIG. 15 can be received and demodulated by the multicarrier reception apparatus 800 configured as shown in FIG. In FIG. 16, in which the same reference numerals are assigned to the parts corresponding to FIG. 3, multicarrier receiving apparatus 800 inputs the signal demodulated by multilevel demodulation section 801 to selection section 802. Here, the selection unit 802 and the deinterleavers 803-1, 803-2,..., 803-N basically perform processing reverse to the corresponding part of the multicarrier transmission apparatus 700.

  Specifically, the multilevel demodulator 801 is the multilevel modulator 107, the selector 802 is the selector 701, the deinterleavers 803-1, 803-2, ..., 803-N are interleavers 702-1, 702-2,..., 702-N and the opposite processes are performed. As a result, the deinterleavers 803-1, 803-2,..., 803-N output a bit string similar to the bit string input to the selection unit 701 on the transmission side, except for transmission degradation.

  In the above-described embodiment, the case where 16QAM is used as multi-level modulation has been described. However, the present invention is not limited to this, and can be applied to the case where 64QAM, 16PSK, or the like is used. In short, the present invention can be widely applied in the case of using multi-level modulation in which there are upper bits that are unlikely to cause transmission errors and lower bits that are likely to cause transmission errors.

  In the above embodiment, the configuration of the OFDM transmitter 109 has not been described in detail. However, even if the spread chips are spread in the frequency axis direction, they are spread in the time axis direction. Also, the same effect as the above-described embodiment can be obtained. Furthermore, the same effect can be obtained even in multicarrier transmission without spreading.

  In the above-described embodiment, a case has been described in which a counter is provided on the receiving side and the number of retransmission signals is detected by counting NACK signals, but the number of transmissions transmitted from the transmitting side has been described. The number of retransmission signals may be detected based on the signal.

  Furthermore, a detection means for detecting the reception level of each subcarrier is provided on the transmission side or the reception side, and based on this detection result, an interleave pattern at the time of retransmission is set so that the same bit is not placed on a subcarrier with a low reception level. If selected, it is possible to reliably avoid the reception level of the same bit continuously lowering in the previous transmission and the next transmission (retransmission), so that the error rate characteristics can be further improved. .

  Further, although cases have been described with the above embodiment where the present invention is implemented by hardware, the same functions as those of the embodiment may be implemented by a program.

The block diagram which shows the structure of the multicarrier transmission apparatus which concerns on Embodiment 1 of this invention. Diagram used to explain the exchange of upper and lower bits FIG. 3 is a block diagram showing a configuration of the multicarrier receiving apparatus according to the first embodiment. Diagram for explaining mapping by 16QAM and determination threshold at demodulation Diagram used to explain the quality of the upper and lower bits The figure for demonstrating the effect of Embodiment 1 Block diagram showing a configuration of a multicarrier transmission apparatus according to Embodiment 2 Diagram for explaining the input / output data of the separation unit Diagram used to explain the input / output data of the multiplexing unit The figure which shows the bit arrangement | sequence when performing the interleaving process by Embodiment 2, and the replacement process of an upper bit and a lower bit Diagram for explaining the effect when bit interleaving is performed with a different interleaving pattern for each retransmission FIG. 3 is a block diagram showing a configuration of a multicarrier receiving apparatus according to a second embodiment. FIG. 9 is a block diagram showing a configuration of a multicarrier transmission apparatus according to Embodiment 3. FIG. 3 is a block diagram showing a configuration of a multicarrier receiving apparatus according to a third embodiment. The block diagram which shows the structure of the multicarrier transmission apparatus of other embodiment. The block diagram which shows the structure of the multicarrier receiver of other embodiment

Explanation of symbols

100, 300, 500, 700 Multi-carrier transmitter 104, 208 Sequence converter 105 Multi-level modulator 106, 204, 302, 304, 403, 405, 501, 502, 503, 506, 601, 602, 603, 606, 701, 802 selection circuit 107-1 to 107-N, 303-1, 303-2, 504-1 to 504-N, 505-1 to 505-N, 702-1 to 702-N interleaver 200, 400, 600, 800 Multi-carrier receivers 206-1 to 206-N, 404-1, 404-2, 604-1 to 604-N, 605-1 to 605-N, 803-1 to 803-N Deinterleaver 207 , 401, 801 Multilevel demodulator 209 Synthesis circuit 301, 402 Separator 306, 406, 607 Multiplexer

Claims (10)

Multi-level modulation means for modulating transmission data of 3 bits or more into one symbol;
Bit replacement means for replacing upper bits and lower bits when performing modulation processing by the multi-level modulation means for each retransmission;
An interleaver that interleaves the bits before multi-level modulation with different interleave patterns for each retransmission; and
Multicarrier transmission means for transmitting a symbol obtained by the multilevel modulation means by superimposing the symbols on a plurality of subcarriers;
A multicarrier transmission apparatus comprising: Bit separation means for separating transmission data composed of one system of bit strings into two systems of bit strings;
A plurality of interleavers for interleaving the separated bit strings of each system with different interleave patterns for each retransmission; and
Multiplexing means for time-division-multiplexing the bit sequence of each sequence after interleaving by changing the order for each retransmission;
Comprising
The multi-level modulation means modulates the bit string multiplexed by the multiplexing means;
The multicarrier transmission apparatus according to claim 1. Detection means for detecting a reception level of each subcarrier, and the interleaver selects an interleave pattern based on the detection result such that the same bit is not arranged in a subcarrier having a low reception level;
The multicarrier transmission apparatus according to claim 1 or 2, characterized by the above. An interleaver that interleaves the symbols obtained by the multi-level modulation means with a different interleave pattern for each retransmission is further provided, and the multicarrier transmission means transmits the interleaved symbols superimposed on a plurality of subcarriers. ,
The multicarrier transmission apparatus according to any one of claims 1 to 3, wherein Multi-level modulation means for modulating transmission data of 3 bits or more into one symbol;
Bit replacement means for replacing upper bits and lower bits when performing modulation processing by the multi-level modulation means for each retransmission;
An interleaver that interleaves the symbols obtained by the multilevel modulation means with different interleave patterns for each retransmission;
Multicarrier transmission means for transmitting interleaved symbols superimposed on a plurality of subcarriers;
A multicarrier transmission apparatus comprising: A multicarrier receiver for receiving and demodulating a multicarrier signal transmitted from the multicarrier transmitter according to any one of claims 1 to 4,
Symbol extraction means for extracting transmission symbols from the received multicarrier signal;
Demodulation means for recovering the transmitted bits by soft-decision of the extracted symbols;
A deinterleaver that performs an interleaving process opposite to the interleaver for each retransmission on the bit string obtained by the demodulation means;
Bit rearrangement means for returning the bit string replaced by the replacement means;
A combining means for performing packet combining for each retransmission using the restored bit string;
A multi-carrier receiving apparatus comprising:   A radio base station apparatus comprising the multicarrier transmission apparatus according to any one of claims 1 to 5.   A communication terminal apparatus comprising the multicarrier transmission apparatus according to any one of claims 1 to 5. A multi-level modulation step of modulating transmission data of 3 bits or more into one symbol;
A bit replacement step of replacing upper bits and lower bits when performing modulation processing in the multi-level modulation step for each retransmission;
An interleaving step for interleaving bits before multi-level modulation with different interleaving patterns for each retransmission;
A multicarrier transmission step of transmitting the symbols obtained in the multilevel modulation step superimposed on a plurality of subcarriers;
A multi-carrier transmission method comprising: A multi-level modulation procedure for modulating transmission data of 3 bits or more into one symbol in a computer;
A bit replacement procedure for replacing the upper bit and the lower bit in the multi-level modulation procedure for each retransmission;
An interleaving procedure for interleaving bits before multi-level modulation with different interleaving patterns for each retransmission;
A program for executing a multicarrier transmission procedure in which symbols obtained by a multilevel modulation procedure are transmitted by being superimposed on a plurality of subcarriers.

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