Abstract:
A MIMO multiple transmission device, comprising a packet data block generator ( 111 ) for generating a packet data block as a resent unit for hybrid ARQ; a CRC adder ( 112 ) for adding an error detection code; a channel encoder ( 113 ) for performing channel encoding, the packet data block generator, the CRC adder and the channel encoder being coupled in series in one or more data streams; a parallel-to-serial converter ( 114 ) for converting output of the channel encoder to serial form; an interleaver between transmission streams ( 115 ) for performing interleaving between transmission streams on outputs from the parallel-to-serial converter; a serial-to-parallel converter ( 116 ) for converting outputs from the interleaver between transmission streams to parallel form; a coding rate changer ( 117 ) for changing a coding rate; and a data modulator ( 119 ) for modulating data, the coding rate changer and the data modulator being connected in series in plural data streams divided by the serial-to-parallel converter.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to a MIMO multiple transmission device and method.  
         [0002]     In general, the more the communication data rate is increased, the more the reception errors occur. For example, if the data modulation system is changed from 2 bits/1 symbol QPSK (Quadrature Phase Shift Keying) to 4 bits/1 symbol 16QAM (Quadrature Amplitude Modulation) or 6 bits/1 symbol 64QAM, the data rate is increased, but the data error rate is also increased.  
         [0003]     As one technology in which the relationship between the data rate and the data error rate is adequately controlled according to communication status, the AMC (Adaptive Modulation and channel Coding) is known, where the data modulation system and the channel coding rate are adequately controlled according to communication status.  
         [0004]      FIG. 1  is a conceptual diagram of a general adaptive modulation and channel coding (AMC) system. A base station  100  transmits to a user # 1  terminal  201  and a user # 2  terminal  202  with the same transmission power. The user # 1  terminal  201  located near to the base station  100  receives high receiving power and has good channel conditions. Accordingly, a high data rate modulation system (for example, 16QAM) and a high channel coding rate are selected for the user # 1  terminal  201 . The user # 2  terminal  202  located far away from the base station  100  receives low receiving power and has bad channel conditions. Accordingly, a low data rate but low data error rate modulation system (for example, QPSK) and low channel data rate are selected for the user # 2  terminal  202 .  
         [0005]      FIG. 2  is a chart showing combinations of data modulation systems and channel coding rates. In the direction (downward direction) shown by an arrow, the data rates are increased, but the data error rates are also increased. Accordingly, the better the channel conditions are, the lower is the combination of modulation system and channel selected in the chart. Conversely, the worse the channel conditions are, the higher is the combination of modulation system and channel selected in the chart. In practice, a table is previously prepared, in which SIR (Signal to Interference power Ratio) as an index of channel conditions corresponds to data modulation systems and channel coding rates. With reference to the table in accordance with a measured channel condition, an adequate combination of data modulation system and channel coding rate is selected to realize AMC.  
         [0006]     As one technology for dealing with data errors, the hybrid ARQ (Automatic Repeat Request) is known. The ARQ is a combination of packet re-send request when detecting error by CRC (Cyclic Redundancy Check) and error channel demodulation by error correction coding (channel coding).  
         [0007]      FIG. 3  shows procedures of a general hybrid ARQ system. At a transmitter side, CRC bit addition (Step S 1 ) and error correction coding (Step S 2 ) are performed. At a receiver side, error correction decoding (Step S 3 ) and error detection using CRC bits (Step S 4 ) are performed. If an error exists, a re-send request is sent to the transmitter side. If no error exists, the transmission (reception) is completed (Step S 5 ).  
         [0008]      FIG. 4  shows three processing types (a), (b) and (c) in the hybrid ARQ. In the type (a), if a packet P 1  has a demodulation error, the packet P 1  is discarded, and a packet P 2  having the same contents is re-sent and demodulated again. In the types (b) and (c), if a packet P 1  has a demodulation error, the packet P 1  is not discarded but held, and the held packet P 1  and a re-sent packet P 2  are combined to generate a packet P 3 , which is demodulated. In the type (b), the same packet is re-sent and the packet combination is performed to improve reception SIR. In the type (c), the re-sent packet had been punctured with a different pattern, and the packet combination is performed to improve coding gain.  
         [0009]      FIG. 5  shows a structure of one antenna transmission frame generating unit in which the above mentioned AMC and hybrid ARQ are employed. The transmission frame generating unit comprises a packet data block generator  101 , a CRC adder  102 , a channel encoder  103 , a coding rate changer  104 , an interleaver  105  and a data modulator  106 , which are connected in series. The packet data block generator  101  generates a packet data block (referred to as “transport block” in 3GPP (3rd Generation Partnership Project)) as one re-sent unit for the hybrid ARQ. The CRC adder  102  adds CRC. The channel encoder  103  performs channel encoding. The coding rate changer  104  performs coding rate changing by rate matching (puncture, repetition), and controls the repetition pattern and puncturing when resending in the hybrid ARQ. The interleaver  105  performs interleaving between transmission streams (including interleaving between frequencies in OFDM (Orthogonal Frequency Division Multiplexing)). The data modulator  106  performs data modulation.  
         [0010]     As one technology realizing large capacity high speed information communication, the MIMO (Multi Input Multi Output) multiple system is known.  FIG. 6  schematically shows the concept of the MIMO multiple system. As shown in (a), in a transmitter side, data are serial-to-parallel converted (Step S 11 ) and transmitted via plural transmitting antennas # 1 ˜#N with the same frequency. In a receiver side, signals received at plural antennas # 1 ˜#M are signal-separated (Step S 12 ) and parallel-to-serial converted to recover the information. In the MIMO multiple system, since a large amount of different pieces of information can be transmitted at the same time, it is possible to drastically increase information bit rates. Data flow A˜D when two antennas are used is schematically shown in (b).  
         [0011]      FIG. 7  shows two types of MIMO multiple systems. In one type shown in (a), two transmission data signals (transmission streams) # 1 , # 2  are transmitted via transmitting antennas # 1 , # 2 , respectively. In another type shown in (b), transmission data signals (transmission streams) # 1 , # 2  are weighted by w 1,1 , w 1,2 , w 2,1 , w 2,2 , and transmitted via the transmission antennas # 1 , # 2  to obtain antenna beam patterns as shown in (b). The present invention can be applied to both. types.  
         [0012]     FIGS.  8 ˜ 10  show some conventional technologies employing the AMC and the hybrid ARQ in the MIMO multiple system (for example see LGE, “Multiplexing Chain for MIMO System,” 3GPP TSG RAN WG1, R1-040259, Malagua, Spain, February 2004).  
         [0013]      FIG. 8  is a first conventional example of a transmission frame generating unit in the MIMO multiple system. As shown in (a), the transmission frame generating unit has a transmission stream # 1  comprising a packet data block generator  101 - 1 , a CRC adder  102 - 1 , a channel encoder  103 - 1 , a coding rate changer  104 - 1 , an interleaver  105 - 1  and a data modulator  106 - 1 , which are connected in series. The transmission frame generating unit has another transmission stream # 2  comprising a packet data block generator  101 - 2 , a CRC adder  102 - 2 , a channel encoder  103 - 2 , a coding rate changer  104 - 2 , an interleaver  105 - 2  and a data modulator  106 - 2 , which are connected in series. The transmission streams # 1  and # 2  are arranged in parallel. This transmission frame generating unit has features as shown in (b).  
         [0014]      FIG. 9  is a second conventional example of a transmission frame generating unit in the MIMO multiple system. As shown in (a), the transmission frame generating unit, comprises a packet data block generator  101 , a CRC adder  102 , a channel encoder  103  and a coding rate changer  104 . After these functions, the data stream is separated by a serial-to-parallel converter  107  into two streams # 1  and # 2 , which have interleavers  105 - 1 ,  105 - 2  and data modulators  106 - 1 ,  106 - 2 , respectively. This frame generating unit has features shown in (b).  
         [0015]      FIG. 10  is a third conventional example of a transmission frame generating unit in the MIMO multiple system. As shown in (a), the transmission frame generating unit comprises a packet data block generator  101 , a CRC adder  102  and a channel encoder  103 . After these functions, the data stream is separated by a serial-to-parallel converter  107  into two streams # 1  and # 2 , which have coding rate changers  104 - 1 ,  104 - 2 , interleavers  105 - 1 ,  105 - 2 , and data modulators  106 - 1 ,  106 - 2 , respectively. This frame generating unit has features shown in (b).  
         [0016]     The above mentioned conventional examples shown in FIGS.  8 ˜ 10  have problems discussed below.  
         [0017]     In the MIMO multiple system, each transmission stream has different channel conditions, and therefore the AMC can be separately performed per each transmission stream to obtain better reception properties (throughput, packet error rate) than common transmission stream processing. With regards of this point, the first conventional example shown in  FIG. 8  and the third conventional example shown in  FIG. 10  are satisfactory, but the second conventional example shown in  FIG. 9  does not allow the channel coding rate change to be separately controlled per transmission stream.  
         [0018]     In the MIMO multiple system, the channel coding and the hybrid ARQ over individual transmission streams are preferable from the viewpoint of increasing the diversity effect at channel decoding. With respect to this point, the second conventional example shown in  FIG. 9  and the third conventional example shown in  FIG. 10  are satisfactory, but the first conventional example shown in  FIG. 8  cannot realize the diversity effect.  
         [0019]     The larger the packet data block size becomes, the larger the wastefulness in resending a packet in response to reception error becomes with respect to this point, the second conventional example shown in  FIG. 9  and the third conventional example shown in  FIG. 10  are disadvantageous.  
         [0020]     Further, when the channel coding speed is fast, the work load in the receiver side becomes heavy. With respect to this point, the second conventional example shown in  FIG. 9  and the third conventional example shown in  FIG. 10  are disadvantageous.  
       SUMMARY OF THE INVENTION  
       [0021]     The present invention may provide a MIMO multiple transmission device and method in which the AMC and the hybrid ARQ can be adequately performed, the wastefulness in resending packet data blocks is small, and the channel decoding work load in the receiver side is small.  
         [0022]     In a preferred embodiment of the present invention is provided a MIMO multiple transmission device, comprising: a packet data block generator ( 111 ) for generating a packet data block as a resent unit for hybrid ARQ; a CRC adder ( 112 ) for adding an error detection code; a channel encoder ( 113 ) for performing channel encoding, the packet data block generator, the CRC adder and the channel encoder being coupled in series in one or more data streams; a parallel-to-serial converter ( 114 ) for converting output of the channel encoder to serial form; an interleaver between transmission streams ( 115 ) for performing interleaving between transmission streams on outputs from the parallel-to-serial converter; a serial-to-parallel converter ( 116 ) for converting outputs from the interleaver between transmission streams to parallel form; a coding rate changer ( 117 ) for changing a coding rate; and a data modulator ( 119 ) for modulating data, the coding rate changer and the data modulator being connected in series in plural data streams divided by the serial-to-parallel converter.  
         [0023]     In another embodiment of the present invention is provided a MIMO multiple transmission device, comprising: a packet data block generator ( 111 ) for generating a packet data block as a resent unit for hybrid ARQ; a CRC adder ( 112 ) for adding an error detection code; a channel encoder ( 113 ) for performing channel encoding, the packet data block generator, the CRC adder and the channel encoder being coupled in series in one or more data streams; a parallel-to-serial converter ( 114 ) for converting output of the channel encoder to serial form; an interleaver between transmission streams ( 115 ) for performing interleaving between transmission streams on outputs from the parallel-to-serial converter; a serial-to-parallel converter ( 116 ) for converting outputs from the interleaver between transmission streams to parallel form; a coding rate changer ( 117 ) for changing a coding rate; and a data modulator ( 119 ) for modulating data, the coding rate changer and the data modulator being connected in series in plural data streams divided by the serial-to-parallel converter; all the above elements being provided for each of plural user data streams; further comprising plurals multiplexers of users ( 132 ), each of which combines outputs from the plural data modulators per each of the transmission streams.  
         [0024]     In further another embodiment of the present invention is provided a MIMO multiple transmission method, comprising the steps of: generating a packet data block; adding an error detection code; performing channel encoding, the above steps being sequentially performed in one or more data streams; converting output after the channel encoding step to serial form; performing interleaving between transmission streams on outputs after the converting step; converting outputs after the interleaving step to parallel form; changing a coding rate; and modulating data, the coding rate changing step and the data modulating step being sequentially performed in plural data streams divided by the converting-to-parallel step.  
         [0025]     According to the embodiments of the present invention, a MIMO multiple transmission device and method are provided in which the AMC and the hybrid ARQ can be adequately performed, the wastefulness in resending packet data blocks is small, and the channel decoding work load in the receiver side is small.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a conceptual diagram of a general adaptive modulation and channel coding (AMC) system;  
         [0027]      FIG. 2  is a chart showing combinations of data modulation systems and channel coding rates;  
         [0028]      FIG. 3  shows procedures of a general hybrid ARQ system;  
         [0029]      FIG. 4  shows three processing types (a), (b) and (c) in the hybrid ARQ;  
         [0030]      FIG. 5  shows a structure of one antenna transmission frame generating unit;  
         [0031]      FIG. 6  schematically shows the concept of MIMO multiple systems;  
         [0032]      FIG. 7  shows two types of MIMO multiple systems;  
         [0033]      FIG. 8  is a first conventional example of a transmission frame generating unit in the MIMO multiple system;  
         [0034]      FIG. 9  is a second conventional example of a transmission frame generating unit in the MIMO multiple system;  
         [0035]      FIG. 10  is a third conventional example of a transmission frame generating unit in the MIMO multiple system;  
         [0036]      FIG. 11  is a transmission frame generating unit according to a first embodiment of the present invention;  
         [0037]      FIG. 12  illustrates operations of a parallel-to-serial converter;  
         [0038]      FIG. 13  illustrates operations of a serial-to-parallel converter;  
         [0039]      FIG. 14  illustrates operations of interleaving between transmission streams;  
         [0040]      FIG. 15  shows in detail an interleaver between transmission streams using block interleaving;  
         [0041]      FIG. 16  shows operations of writing packet data blocks into the interleaver between transmission streams;  
         [0042]      FIG. 17  shows operations of reading out packet data blocks from the interleaver between transmission streams;  
         [0043]      FIG. 18  shows another structure of an interleaver between transmission streams;  
         [0044]      FIG. 19A  is a block diagram of a first structure of a transmitter according to the present invention;  
         [0045]      FIG. 19B  is a block diagram of a second structure of a transmitter according to the present invention;  
         [0046]      FIG. 20  is a block diagram of a transmitter for multiplexing plural users&#39; data;  
         [0047]      FIG. 21  shows examples of symbol arrangement in OFDM for multiplexing plural users&#39; data;  
         [0048]      FIG. 22A  is a block diagram of a first receiver corresponding to the transmitter according to the present invention; and  
         [0049]      FIG. 22B  is a block diagram of a first receiver corresponding to the transmitter according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]     The following is a description of embodiments of the present invention, with reference to the accompanying drawings.  
         [0051]     Throughout all the figures, members and parts having the same or similar functions are assigned the same or similar reference signs, and redundant explanations are omitted.  
         [0052]      FIG. 11  is a transmission frame generating unit according to a first embodiment of the present invention. As shown in (a), two upper streams of the transmission frame generating unit comprise packet data block generators  111 - 1 ,  111 - 2  for generating a packet data block as a resending unit in the hybrid ARQ, CRC adders  112 - 1 ,  112 - 2  for adding error detection code, channel encoders  113 - 1 ,  113 - 2  for performing channel encoding in series, respectively. The number of streams may alternatively be one or any number more than two.  
         [0053]     The transmission frame generating unit further comprises a parallel-to serial converter  114  for converting the outputs from the channel encoders  113 - 1 ,  113 - 2  to serial form, an interleaver between transmission streams  115  for interleaving the outputs from the parallel-to-serial converter  114  by changing the order of transmission streams, and a serial-to-parallel converter  116  for converting the outputs from the interleaver between transmission streams  115  to parallel form.  
         [0054]     The two streams separated by the serial-to-parallel converter  116  of the transmission frame generating unit comprise coding rate changers  117 - 1 ,  117 - 2 , interleavers between transmission streams  118 - 1 ,  118 - 2 , and data modulators  119 - 1 ,  119 - 2 , respectively. The coding rate changers  117 - 1 ,  117 - 2  change a coding rate by level matching (puncture, repetition), and control repetition and puncture when resending in the hybrid ARQ. The interleavers  118 - 1 ,  118 - 2  interleave by changing the order of transmission streams (including frequencies in the OFDM). The data modulators  119 - 1 ,  119 - 2  modulate data. Two transmission streams are shown here, but the number of transmission streams is not limited to that.  
         [0055]      FIG. 11 ( b ) illustrates features of the above embodiment. As for the AMC, since the data modulators  119 - 1 ,  119 - 2 , and the channel coding rate changers  117 - 1 ,  117 - 2  are provided in the corresponding transmission streams, adequate control can be separately performed for each transmission stream in accordance with channel conditions in the corresponding transmission stream. As for the hybrid ARQ, since the CRC adders  112 - 1 ,  112 - 2 , and the channel encoders  113 - 1 ,  113 - 2  are provided over the corresponding streams, the diversity effect can be expected due to the interleaving between transmission streams.  
         [0056]     Since plural packet data block generating units  111 - 1 ,  111 - 2  generate packet data blocks as a resending unit in the hybrid ARQ, the wastefulness in resent packet data blocks is small. Further, since the channel encoders  113 - 1 ,  113 - 2  perform channel coding in these streams, the work load in a receiver side due to channel demodulation is small.  
         [0057]      FIG. 12  illustrates an operational example of the parallel-to-serial converter  114 . Packet data blocks input in parallel are converted to serial form.  FIG. 13  illustrates an operational example of the serial-to-parallel converter  116 . Serially input packet data blocks are converted to parallel form.  
         [0058]      FIG. 14  illustrates an operational example of the interleaver between transmission streams  115 . Packet data blocks # 1 ˜# 3  are converted by the parallel-to-serial converter  114  to a serial packet data sequence, which is written into a memory region in the interleaver between transmission streams  115 . The interleaver between transmission streams  115  reads out packet data sequentially across plural packet data blocks. The read packet data sequence is converted by the serial-to-parallel converter  116  to parallel form, the transmission streams of which are given to the coding rate changers  117 - 1 ,  117 - 2 , respectively.  
         [0059]      FIG. 15  shows in detail the interleaver between transmission streams  115  using a block interleaver. The lateral (left-right) size is a packet data block length T. The vertical (up-down) size is the number P of packet data blocks. The positions of the read packet data can be identified with column numbers 0-T-1. Writing is performed in the lateral direction per packet data block. Reading is performed in the vertical direction from upper to lower. First, the least column number in the columns satisfying the following equation is read. 
 [Column number] mod [the number  N  of transmission streams]=0  
         [0060]     Next, the least column number in the columns satisfying the following equation is read. 
 
[Column number] mod [the number  N  of transmission streams]=1 
 
         [0061]     These reading procedures are repeated. Last, all the columns satisfying the following equation are read and then the reading procedures are finished. 
 
[Column number] mod [the number  N  of transmission streams]= N− 1 
 
         [0062]     Mod means a remainder operation, that is A mod B means the remainder of A divided by B.  
         [0063]      FIG. 16  illustrates an operational example of writing packet data blocks into the interleaver between transmission streams  115 . In this example, a packet data block length T is 12 and the number P of packet data blocks is 3.  
         [0064]      FIG. 17  illustrates an operational example of reading out packet data blocks from the interleaver between transmission streams  115 . Reading is performed in the vertical direction from upper to lower sequentially in each of column positions indicated by black triangles in  FIG. 17 . The read packet data sequence is converted by the serial-to-parallel converter  116  to plural streams. Each of the streams has a specific length (length 6 for # 1  stream, 9 for # 2 , 9 for # 3 , 12 for # 4 ) and is given to the corresponding coding rate changer.  
         [0065]      FIG. 18  illustrates another example of the interleaver between transmission streams  115 , in which writing and reading operations can be controlled based on control information. The control information includes the number P of packet data blocks, packet data block length T, the number N of transmission streams, etc.  
         [0066]      FIGS. 19A and 19B  show two embodiments of a transmitter (MIMO multiple transmitter) according to the present invention. A packet data block generating unit  121  shown in  FIG. 19A  corresponds to the packet data block generating units  111 - 1 ,  111 - 2  shown in  FIG. 11 . CRC adders  122 - 1 ,  122 - 2  shown in  FIG. 19A  correspond to the CRC adders  112 - 1 ,  112 - 2  shown in  FIG. 11 . Turbo encoders  123 - 1 ,  123 - 2  shown in  FIG. 19A  correspond to the channel encoders  113 - 1 ,  113 - 2  shown in  FIG. 11 . A parallel-to-serial converter  124 , an interleaver between transmission streams  125  and a serial-to-parallel converter  126  shown in  FIG. 19A  correspond respectively to the parallel-to-serial converter  114 , the interleaver between transmission streams  115  and the serial-to-parallel converter  116  shown in  FIG. 11 .  
         [0067]     Turbo coding rate adjusters  127 - 1 ,  127 - 2  shown in  FIG. 19B  correspond to the coding rate changers  117 - 1 ,  117 - 2  shown in  FIG. 11 . Interleavers between transmission streams  128 - 1 ,  128 - 2  shown in  FIG. 19B  correspond to the interleavers between transmission streams  118 - 1 ,  118 - 2  shown in  FIG. 11 . Data modulators  129 - 1 ,  129 - 2  shown in  FIG. 19B  correspond to the data modulators  119 - 1 ,  119 - 2  shown in  FIG. 11 . OFDM modulators  130 - 1 ,  130 - 2  perform the OFDM modulation, but are not needed when the OFDM modulation is not employed. An adaptive modem/channel coding controller  131  controls the turbo coding rate and adjuster  127 - 1 ,  127 - 2 , . . . and the data modulators  129 - 1 ,  129 - 2 , . . . separately based on channel condition information per each of transmission stream.  
         [0068]      FIG. 20  shows a structure example of a transmitter for multiplexing plural user data streams. A structure the same as from the packet data block generating unit  121  to the data modulators  129 - 1 ,  129 - 2 , . . . , is provided for each user. Multiplexer of users  132 - 1 ,  132 - 2 , . . . , provided after the data modulators  129 - 1 ,  129 - 2 , . . . , multiplex the modulated data per each stream.  
         [0069]      FIG. 21  illustrates symbol arrangement examples in the OFDM for multiplexing plural users. As shown in (a)˜(d), the symbols of users&#39; transmission data sequences are arranged in the same positions in plural transmission streams # 1 ˜# 3 . In this manner,. the same users are placed at the same places in all the transmission streams, and accordingly it is possible to avoid property degradation due to signal separation between different users, and complex processing for received signals.  
         [0070]      FIGS. 22A and 22B  show an example of a receiver corresponding to a transmitter according to the present invention. The receiver shown in  FIGS. 22A and 22B  comprises OFDM demodulators  211 - 1 ,  211 - 2 , . . . , a channel estimator  212 , a channel condition information generator  213 , a control channel demodulator  214 , a signal separator  215 , likelihood calculators per bit  216 - 1 ,  216 - 2 , . . . , and de-interleavers between transmission streams  217 - 1 ,  217 - 2 , . . . The OFDM demodulators  211 - 1 ,  211 - 2 , . . . perform the OFDM demodulation on signals received at each antenna. The OFDM demodulators are not needed if the OFDM modulation is not employed. The channel estimator  212  performs channel estimation for each transmission stream based on pilot signal included in the received signal. The channel condition information generator  213  generates channel condition information per each transmission stream for the adaptive modulation/channel coding, and notify the transmitter of it via a counter link. The control channel demodulator  214  demodulates a control channel from the received signal. The signal separator  215  separates a signal (data) from the received signal in accordance with the channel estimation given by the channel estimator  212  and modulation system information given by the control channel demodulator  214 . The likelihood calculators per bit  216 - 1 ,  216 - 2 , . . . calculates the likelihood of each bit based on the signal per transmission stream of the signal separator  215 . The de-interleavers between transmission streams  217 - 1 ,  217 - 2 , . . . perform de-interleaving between transmissions based on outputs from the likelihood calculator per bit.  
         [0071]     The receiver shown in  FIGS. 22A and 22B  further comprises a parallel-to-serial converter  218 , a de-interleaver between transmission streams  219 , a serial-to-parallel converter  220 , packet combiners  221 - 1 ,  221 - 2 , . . . , a buffer  222 , turbo decoders  223 - 1 ,  223 - 2 , . . . , a CRC checkers  224 - 1 ,  224 - 2 , . . . , and a packet data block combiner  225 . The parallel-to-serial converter  218  converts the outputs from the de-interleavers between transmission streams  217 - 1 ,  217 - 2 , . . . to serial form. The de-interleavers between transmission streams  219  perform de-interleaving between transmission streams on outputs from the parallel-to-serial converter  218 . The serial-to-parallel converter  220  converts outputs from the de-interleavers  219  to parallel form. The packet combiners  221 - 1 ,  221 - 2 , . . . combines parallel packet data blocks only when resending, and does not combine them when not resending. The buffer  222  buffers packet data in accordance with information indicating whether to resend or not. The turbo decoders  223 - 1 ,  223 - 2 , . . . decode outputs from the packet combiners  221 - 1 ,  221 - 2 , . . . The CRC checker  224 - 1 ,  224 - 2 , . . . checks CRC based on outputs from the turbo decoders  223 - 1 ,  223 - 2 , . . . and notifies the transmitter if an error exists. The packet data block combiner  225  combines outputs from the turbo decoders  223 - 1 ,  223 - 2 , . . . to recover the transmitted data sequence, and outputs the recovered data sequence.  
         [0072]     The present application is based on Japanese Priority Application No. 2005-027733 filed on Feb. 3, 2005 with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.