Abstract:
The present invention discloses a transmission method and apparatus for a wireless communication system. The data transmission apparatus includes an encoder capable of encoding input data to generate first coded bits and second coded bits; a channel interleaver capable of interleaving said first coded bits and said second coded bits, to generate first interleaved coded bits and second interleaved coded bits; a partially swap unit capable of partially swapping said first interleaved coded bits to generate partially swapped first interleaved coded bits, and combining said partially swapped said first interleaved coded bits and said second interleaved coded bits to generate processed bits; a modulator capable of mapping said processed bits to modulation symbols in a predetermined modulation scheme; and a transmitter capable of transmitting the modulation symbols. Related methods are also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Divisional of pending U.S. patent application Ser. No. 12/715,410, filed Mar. 2, 2010, and entitled “Apparatus and Method for Transmitting/Receiving Data in a Wireless Communication System,” which claims priority to provisional application no. 61/156,720, the entireties of which are incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to an apparatus and method for transmitting/receiving data in a wireless communication system, more particularly, related to an apparatus and method for improve reliability at data transmission. 
       BACKGROUND 
       [0003]    On wireless high-speed, high-quality data services, it is very difficult in practice to receive pure signals without signal distortion or noise. Adverse influences are attributed to a radio channel environment in a wireless communication system. For a wireless communication system, the radio channel environment varies frequently because of white noise, fading-incurred signal power changes, shadowing and interference from other users and multi-path signals. If the data is received in a mobile terminal, the influence further includes the Doppler Effect that occurs due to the movement and frequent velocity changes of a terminal. 
         [0004]    Accordingly, great amounts of time and energy have been expended toward minimizing the influence of distortion or noise involved with signal transmission and reception in a wireless communication system. Common techniques in communication systems with unreliable and time-varying channel conditions are AMCS (Adaptive Modulation &amp; Coding Scheme) and HARQ (hybrid automatic repeat request). 
         [0005]    AMCS adjusts a modulation order and a coding rate according to changes in downlink channel condition. The downlink channel quality is usually evaluated by measuring the SNR (Signal-to-Noise Ratio) of a received downlink signal at a UE (User Equipment). The UE feeds back the channel quality information to a BS (Base Station) on an uplink. Then the BS estimates the downlink channel condition based on the channel quality information and determines an appropriate modulation scheme and coding rate for a channel encoder according to the downlink channel condition estimate. 
         [0006]    HARQ is a retransmission control technique, which is to correct errors in initially transmitted data packets based on automatic repeat request (ARQ) schemes together with a forward error correction (FEC) technique. Schemes for implementing HARQ include chase combining (CC), full incremental redundancy (FIR), and partial incremental redundancy (PIR). 
         [0007]      FIG. 1  is a block diagram of a transmitter/receiver in a typical high-speed wireless data packet communication system. Referring to  FIG. 1 , the transmitter  100  includes an encoder  110 , a channel interleaver  120  and a modulator  130 . Upon input of information bits, the encoder  110  is operable to encode the information bits at a predetermined coding rate. f coding rate R (=n/k, n is prime to k.) is set to, for example, ½ or ¾, the encoder  110  outputs n coded bits for the input of k information bits. The burst errors, which are often generated on a fading channel, can be prevented by interleaving. The channel interleaver  120  performs interleaving to distribute coded bits having the same information to overcome the shortcoming of the error control coding, and to minimize data loss caused by burst errors. The modulator  130  modulates the interleaved bits in a predetermined modulation scheme, such as QPSK, 8PSK, 16QAM, and 64QAM. The modulated data is transmitted over the communication channel  190 . The communication channel is typically a radio communication channel experiencing unreliable and time-varying channel conditions. Preferably, the transmitter  100  can further include a controller to select the coding rate for the encoder  110 , and modulation scheme for modulator  130 . 
         [0008]    The receiver  101  includes a decoder  160 , a deinterleaver  150  and a demodulator  140 . The demodulator  140  demodulates the received data into a corresponding bit domain sequence. The deinterleaver  150  performs deinterleaving the bit sequence from the demodulator  140 , by applying a determined, pseudo-random or random permutation of the input bit sequences which is applied by the interleaver  120 . The decoder  160  then decodes the deinterleaved data to output the information bits. 
         [0009]    As stated before, the modulator  140  supports various modulation schemes including QPSK, 8PSK, 16QAM and 64QAM with respect to the interleaved bits. In modulator  140 , an interleaved data mapped on a modulation symbol, and the symbol mapping refers to designation of symbol positions in a two-dimensional symbol constellation having an I channel along an X axis and a Q channel along a Y axis. As a modulation order increases, the number of bits in one modulation symbol increases. Bits mapped to one modulation symbol have different transmission reliabilities according to their positions. With regard to transmission reliability, two bits of a modulation symbol representing a macro region defined by left/right and up/down have a relatively high reliability in an I (In Phase)-Q (Quadrature Phase) signal constellation. The other bits representing a micro region within the macro region have a relatively low reliability. 
         [0010]      FIG. 2  illustrates an exemplary signal constellation in 16QAM. Referring to  FIG. 2 , one 16QAM modulation symbol contains 4 bits [a 3 , a 2 , a 1 , a 0 ] in a reliability pattern [H, L, H, L] (H denotes high reliability and L denotes low reliability). That is, the two bits [a 1 , a 3 ] have a relatively high reliability, and the two bits [a 0 , a 2 ], a relatively low reliability.  FIG. 3  illustrates an exemplary signal constellation in 64QAM. Referring to  FIG. 3 , one 64QAM modulation symbol contains 6 bits [a 5 , a 4 , a 3 , a 2 , a 1 , a 0 ] in a reliability pattern [H, M, L, H,M, L] (M denotes medium reliability). 
         [0011]    In conventional HARQ, however, initial transmission bits and their retransmission bits are the same in reliability. Bits mapped to a low reliability position still have the low reliability at retransmission and the same occurs to bits mapped to a high reliability. 
         [0012]    In IEEE 802.16 standard, one of the forward error correction (FEC) schemes is duo-binary turbo code called convolutional turbo code (CTC).  FIG. 4  illustrates a block diagram of conventional CTC encoder. CTC encoder  400  comprises a CTC interleaver  410 , a first constituent encoder  421  and a second constituent encoder  422 . Upon input of A code and B code, the CTC encoder  400  outputs six code groups including A code, B code, Y 1  code,W 1  code, Y 2  code and W 2  code, wherein A code and B code are systematic parts. Y 1  code and W 1  code are the parity parts generated by the first convolutional encoder  421 . Y 2  and W 2  are the parity parts generated by the second convolutional encoder  422 . 
         [0013]      FIG. 5  illustrates a schematic view of conventional channel interleaving scheme for CTC encoder. The channel interleaver performs following operations: bit separation  51 , subblock interleaving  52 , bit grouping  53  and bit selection  54 . In operation of bit separation  51 , the encoded bits outputted from CTC encoder  400  are sequentially distributed into six subblocks. A code subblock  551 , B code subblock  552 , Y 1  code subblock  553 , Y 2  code subblock  554 , W 1  code subblock  555  and W 2  code subblock  556 . These six subblocks are respectively inputted to subblock interleaver  591 ,  592 ,  593 ,  594 ,  595  and  596  in operation of sub block interleaving  52 . In bit grouping  53 , the interleaved A and B subblock sequences are grouped directly, YI and Y 2  subblock sequences are bit-by-bit multiplexed, and WI and W 2  subblock sequences are bit-by-bit multiplexed. In bit selection, the grouped bits are selected continuously and circularly to generate subblocks and fed to the modulator. 
         [0014]    However, this channel interleaving scheme has some disadvantages. First, some contiguous coded bits are mapped onto the bit location with the same level of reliability on the constellation. Besides, when 16-QAM is considered, subblocks YI (WI) and Y 2  (W 2 ) are always mapped into more and less reliable bit location respectively, as shown in  FIG. 6 . Third, the reliability distribution of systematic and parity bits corresponding to the same information bit is not uniform. 
       SUMMARY OF THE INVENTION 
       [0015]    Therefore, an object of the present invention is to provide a transmission apparatus and method, so as to improve reliability at first transmission or retransmission in a wireless communication system. 
         [0016]    The object of the present invention can be achieved by providing a transmission method for retransmitting in a transmitter of a wireless communication system, and the method comprises the steps of transmitting a first data mapped in a QAM constellation pattern in a first transmission, and retransmitting a second data mapped in the QAM constellation pattern in a retransmission. The second data is reversion of the first data. 
         [0017]    The object of the present invention can be achieved by providing a transmission method for retransmitting in a transmitter of a wireless communication system, and the method comprises steps of transmitting a bit sequence (b 3 , b 2 , b 1 , b 0 ) mapped in a 16 QAM constellation pattern in a first transmission; upon receiving a retransmission request, performing a rearrangement by swapping b 3  and b 1  with b 2  and b 0 , to generate a rearranged bit sequence (b 2 , b 3 , b 0 , b 1 ); retransmitting the rearranged bit sequence mapped in said QAM constellation pattern in a retransmission. 
         [0018]    The object of the present invention can be achieved by providing a transmission method for retransmitting in a transmitter of a wireless communication system, and the method comprises steps of transmitting a bit sequence (b 5 , b 4 , b 3 , b 2 , b 1 , b 0 ) mapped in a 64 QAM constellation pattern in a first transmission; upon receiving a retransmission request, performing a rearrangement by swapping b 5 , b 3  and b 1  with b 4 , b 2  and b 0 , to generate a rearranged bit sequence (b 4 , b 5 , b 2 , b 3 , b 0 , b 1 ); retransmitting said rearranged bit sequence mapped in said 64 QAM constellation pattern in a retransmission. 
         [0019]    The object of the present invention can be achieved by providing a transmission method for retransmitting in a transmitter of a wireless communication system, and the method comprises steps of transmitting a bit sequence (b 5 , b 4 , b 3 , b 2 , b 1 , b 0 ) mapped in a  64  QAM constellation pattern in a first transmission; upon receiving a retransmission request, performing a rearrangement by swapping b 5 , b 2  with b 3  and b 0 , to generate a rearranged bit sequence (b 3 , b 4 , b 5 , b 0 , b 1 , b 2 ); retransmitting said rearranged bit sequence mapped in said QAM constellation pattern in a retransmission. 
         [0020]    The object of the present invention can be achieved by providing a transmission apparatus capable of retransmitting in a wireless communication system. The apparatus comprises an encoder, a channel interleaver, a modulator and a transmitter. The encoder is capable of encoding input data and outputting coded bits. The channel interleaver is capable of interleaving the coded bits to generating interleaved bits, and reversing said interleaved bits upon receiving a retransmission request from a receiver. The modulator is capable of mapping said reversed bits to modulation symbols in a predetermined modulation scheme. 
         [0021]    The object of the present invention can be achieved by providing a transmission apparatus capable of retransmitting in a wireless communication system. The apparatus comprises an encoder, a channel interleaver, a bit swap unit, a modulator and a transmitter. The encoder is capable of encoding input data and outputting coded bits. The channel interleaver is capable of interleaving the coded bits to generate interleaved bits. The bit swap unit is capable of swapping the interleaved bits to generate swapped bits, upon receiving a retransmission request from a receiver. The modulator is capable of mapping the swapped bits to modulation symbols in a predetermined modulation scheme. The transmitter is capable of transmitting the modulation symbols to said receiver. 
         [0022]    The object of the present invention can be achieved by providing a transmission method comprising steps of: encoding input data to generate an encoded data containing first coded bits; interleaving said first coded bits to generate first interleaved bits; partially swapping said first coded bits to generate processed bits; mapping said interleaved bits to modulation symbols in a predetermined modulation scheme; transmitting the modulation symbols. 
         [0023]    The object of the present invention can be achieved by providing a transmission apparatus, comprising an encoder, a channel interleaver, a partially swap unit, a modulator and a transmitter. The encoder is capable of encoding input data to generate first coded bits and second coded bits. The channel interleaver is capable of interleaving said first coded bits and said second coded bits, to generate first interleaved coded bits and second interleaved coded bits. The partially swap unit is capable of partially swapping said first interleaved coded bits to generate partially swapped first interleaved coded bits, and combining said partially swapped said first interleaved coded bits and said second interleaved coded bits to generate processed bits. The modulator is capable of mapping said processed bits to modulation symbols in a predetermined modulation scheme. The transmitter is capable of transmitting the modulation symbols. 
         [0024]    The object of the present invention can be achieved by providing a transmission method comprising steps of encoding input data to generate first coded bits and second coded bits; multiplexing said first coded bits and said second coded bits per N bits, N is an integer larger than 1, to form processed bits; mapping said processed bits to modulation symbols in a predetermined modulation scheme; transmitting the modulation symbols. 
         [0025]    The object of the present invention can be achieved by providing a transmission apparatus comprising an encoder, a channel interleaver, a modulator and a transmitter. The encoder is capable of encoding input data to generate first coded bits and second coded bits. The channel interleaver is capable of interleaving said first coded bits and said second coded bits to generate said first interleaved coded bits and said second interleaved coded bits, and multiplexing said first interleaved coded bits and said second interleaved coded bits per N bits, N is an integer larger than 1, to form processed bits. The modulator is capable of mapping said processed bits to modulation symbols in a predetermined modulation scheme. The transmitter is capable of transmitting the modulation symbols. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. 
           [0027]      FIG. 1  illustrates a block diagram of an exemplary transmitter and receiver in accordance with the present invention; 
           [0028]      FIG. 2  illustrates an exemplary signal constellation in 16QAM; 
           [0029]      FIG. 3  illustrates an exemplary signal constellation in 64QAM; 
           [0030]      FIG. 4  illustrates a block diagram of conventional CTC encoder; 
           [0031]      FIG. 5  illustrates a schematic view of conventional channel interleaving scheme for CTC encoder; 
           [0032]      FIG. 6  illustrates a schematic view of reliability of code bit by 16 QAM in conventional channel interleaving scheme; 
           [0033]      FIG. 7  illustrates a flow chart of first embodiment of transmission method in accordance with the present invention; 
           [0034]      FIG. 8  illustrates a flow chart of second embodiment of transmission method in accordance with the present invention; 
           [0035]      FIG. 9  illustrates examples of bit swap scheme in accordance with the present invention; 
           [0036]      FIG. 10  illustrates a block diagram of first embodiment of transmission data in accordance with the present invention; 
           [0037]      FIG. 11  illustrates a flow chart of third embodiment of transmission method in accordance with the present invention; 
           [0038]      FIG. 12  illustrates a first example of multiplexing scheme of transmission method in accordance with the present invention; 
           [0039]      FIG. 13  illustrates a second example of multiplexing scheme of transmission method in accordance with the present invention; 
           [0040]      FIG. 14  illustrates a third example of multiplexing scheme of transmission method in accordance with the present invention; 
           [0041]      FIG. 15  illustrates a fourth example of multiplexing scheme of transmission method in accordance with the present invention; 
           [0042]      FIG. 16  illustrates a flow chart of fourth embodiment of transmission method in accordance with the present invention; 
           [0043]      FIG. 17  illustrates a schematic view of partially swapping scheme of transmission method in accordance with the present invention; 
           [0044]      FIG. 18  illustrates an example of partially swapping scheme the present invention applied in the CTC encoder; 
           [0045]      FIG. 19  illustrates a flow chart of fifth embodiment of transmission method in accordance with the present invention; 
           [0046]      FIG. 20  illustrates an example of transmission method applied in the CTC encoder; and 
           [0047]      FIG. 21  illustrates a block diagram of second embodiment of transmission apparatus in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0048]    In the following detailed description, reference is made to the accompanying drawing figures which form a part hereof, and which show by way of illustration specific embodiments of the invention. It is to be understood by those of ordinary skill in this technological field that other embodiments may be utilized, and structural, electrical, as well as procedural changes may be made without departing from the scope of the present invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. 
         [0049]      FIG. 7  illustrates a flow chart of first embodiment of transmission method in accordance with the present invention. This first embodiment comprises the following steps. In step  701  a first data mapped in a QAM constellation pattern is transmitted in a first transmission. And in retransmission, a second data which is reversion of said first data, is mapped in the QAM constellation pattern and transmitted. Preferably, the QAM constellation pattern is a 16 QAM constellation pattern, and the first data is bit sequence (b 3 , b 2 , b 1 , b 0 ) and the second data is a bit sequence (b 0 , b 1 , b 2 , b 3 ). While modulation symbol of the 16 QAM constellation pattern contains 4 bits [a 3 , a 2 , a 1 , a 0 ] and bits [a 3 , a 1 ] have a high reliability and bits [a 2 , a 0 ] have a low reliability, then bits [b 2 , b 0 ] of data, which are mapped to low reliability location in 16 QAM constellation pattern in first transmission, can be mapped to high reliability location in retransmission. 
         [0050]    Preferably, the QAM constellation pattern can be a 64 QAM constellation pattern, and the first data is a bit sequence (b 5 , b 4 , b 3 , b 2 , b 1 , b 0 ) and the second data is a bit sequence (b 0 , b 1 , b 2 , b 3 , b 4 , b 5 ). While modulation symbol of the 64 QAM constellation pattern contains 6 bits [a 5 , a 4 , a 3 , a 2 , a 1 , a 0 ] and bits [a 5 , a 2 ] have a high reliability and bits [a 4 , a 1 ] have a medium reliability and bits [a 3 , a 0 ] have a low reliability, then bits [b 3 , b 0 ] of data, which are mapped to low reliability location in 64 QAM constellation pattern in first transmission, can be mapped to high reliability location in retransmission. Therefore, reliability at data retransmission can be improved efficiently. 
         [0051]      FIG. 8  illustrates a flow chart of second embodiment of transmission method in accordance with the present invention. As shown in  FIG. 2 , second embodiment comprises the following steps. In step  711 , in a first transmission a bit sequence mapped in a QAM constellation pattern is transmitted. In step  712 , it is determined whether a retransmission request from a receiver is received. If such retransmission request is received, a rearrangement is performed by swapping the bit sequence to generate a rearranged bit sequence in step  713 . In step  714 , in a retransmission the rearranged bit sequence mapped in the QAM constellation pattern is transmitted. 
         [0052]      FIG. 9  illustrates examples of bit swap scheme in accordance with the present invention. In 16 QAM constellation pattern, the bit sequence (b 3 , b 2 , b 1 , b 0 )  721  is rearranged by swapping b 3  and b 1  with b 2  and b 0  in step  713 , to generate the rearranged bit sequence (b 2 , b 3 , b 0 , b 1 )  722 , as shown the example (A) in  FIG. 9 . 
         [0053]    In 64 QAM constellation pattern, the bit sequence (b 5 , b 4 , b 3 , b 2 , b 1 , b 0 )  723  is rearranged by swapping b 5 , b 3  and b 1  with b 4 , b 2  and b 0  in step  713 , to generate a rearranged bit sequence (b 4 , b 5 , b 2 , b 3 , b 0 , b 1 )  724 , as shown the example (B) in  FIG. 9 . In another example, the bit sequence (b 5 , b 4 , b 3 , b 2 , b 1 , b 0 )  723  can be rearranged by swapping b 5 , b 2  with b 3  and b 0  in step  713 , to generate the rearranged bit sequence (b 3 , b 4 , b 5 , b 0 , b 1 , b 2 )  725 , as shown the example (C) in  FIG. 9 . 
         [0054]    Preferably, the rearrangement can be performed by reversing the bit sequence. As shown the example (D) in  FIG. 9 , the rearranged bit sequence (b 0 , b 1 , . . . , b L-2 , B L-1 , b L )  725  is the reversion of the bit sequence (b L , b L-1 , B L2 , . . . , b 1 , b 0 )  726 , L is a positive integer larger than 2. 
         [0055]      FIG. 10  illustrates a block diagram of first embodiment of transmission data in accordance with the present invention. The transmission apparatus  730  comprises an encoder  731 , a channel interleaver  732 , a bit swap unit  733 , a modulator  734  and a transmitter  735 . The encoder  731  is operable to encode input data  741  and outputting coded bits  742 . The channel interleaver  732  is operable to interleave the coded bits  742  to generate interleaved bits  743 . In first transmission, the modulator  734  is operable to map the interleaved bits  743  to modulation symbols  744  in a predetermined modulation scheme and the modulation symbols  744  is then transmitted by transmitter  735 . 
         [0056]    While the transmission apparatus  730  receives a retransmission request  729  from a receiver, the bit swap unit  733  swaps the interleaved bits  743  to generate swapped bits  745 , and modulator  734  maps the swapped bits  745  to modulation symbols  744  in the predetermined modulation scheme. The transmitter  735  transmits the modulation symbols  744  to the receiver. Preferably, the predetermined modulation scheme is a 16QAM modulation scheme or a 64QAM modulation scheme. The bit swap scheme operated by bit swap unit  733  is described in preceding paragraph, so not explain in detail again. Preferably, the bit swap unit  733  can be implemented inside the channel interleaver  732 , and bit swap scheme is also executed by the channel interleaver  732 . 
         [0057]      FIG. 11  illustrates a flow chart of third embodiment of transmission method in accordance with the present invention. The third embodiment comprises the following steps. In step  801 , input data is encoded to generate an encoded data containing first coded bits and second coded bits. In step  802 , the first coded bits and the second coded bits are multiplexed per N bits, N is an integer larger than 1, to form interleaved bits. In step  803 , the interleaved bits are mapped to modulation symbols in a predetermined modulation scheme, and the modulation symbols are transmitted in step  804 . Preferably, N can be 2 or 6 when the predetermined modulation scheme is 16QAM modulation scheme; N can be 3 or 6 when the predetermined modulation scheme is 64QAM modulation scheme. 
         [0058]      FIG. 12  illustrates a first example of multiplexing scheme of transmission method in accordance with the present invention. In  FIG. 12 , such multiplexing scheme is applied in CTC encoder, the data outputted from the subblock interleaver  593  corresponding to YI code is multiplexed with the data outputted from the subblock interleaver  594  corresponding to Y 2  code per  6  bits. Similarly, the data outputted from the subblock interleaver  595  corresponding to WI code is multiplexed with the data outputted from the subblock interleaver  596  corresponding to W 2  code per 6 bits. Therefore, the YI code, Y 2  code, WI code, W 2  code under multiplexing scheme of the present invention can have more uniform reliability in transmission in 16 QAM modulation scheme or 64 QAM modulation scheme. 
         [0059]      FIG. 13  illustrates a second example of multiplexing scheme of transmission method in accordance with the present invention. In this example, the data outputted from the subblock interleaver  591  corresponding to A code and the data outputted from the subblock interleaver  592  corresponding to B code are multiplexed per 6 bits, so that the systematic (A code and B code) and parity bits (YI code, Y 2  code, WI code and W 2  code) can have more uniform reliability in transmission. 
         [0060]      FIG. 14  illustrates a third example of multiplexing scheme of transmission method in accordance with the present invention. In  FIG. 14 , such multiplexing scheme is applied in CTC encoder, the data outputted from the subblock interleaver  593  corresponding to YI code is multiplexed with the data outputted from the subblock interleaver  594  corresponding to Y 2  code per 2 bits. Similarly, the data outputted from the subblock interleaver  595  corresponding to WI code is multiplexed with the data outputted from the subblock interleaver  596  corresponding to W 2  code per 2 bits. Therefore, the YI code, Y 2  code, WI code, W 2  code under multiplexing scheme of the present invention can have more uniform reliability in transmission in 16 QAM modulation scheme. 
         [0061]      FIG. 15  illustrates a fourth example of multiplexing scheme of transmission method in accordance with the present invention. In  FIG. 15 , such multiplexing scheme is applied in CTC encoder, the data outputted from the subblock interleaver  593  corresponding to YI code is multiplexed with the data outputted from the subblock interleaver  594  corresponding to Y 2  code per  3  bits. Similarly, the data outputted from the subblock interleaver  595  corresponding to WI code is multiplexed with the data outputted from the subblock interleaver  596  corresponding to W 2  code per 3 bits. Therefore, the Y 1  code, Y 2  code, W 1  code, W 2  code under multiplexing scheme of the present invention can have more uniform reliability in transmission in 64 QAM modulation scheme. 
         [0062]    Preferably, the data outputted from the subblock interleaver  591  corresponding to A code and the data outputted from the subblock interleaver  592  corresponding to B code can be, if necessary, multiplexed per 2 bits or 3 bits. 
         [0063]      FIG. 16  and  FIG. 17  illustrate respectively a flow chart of fourth embodiment of transmission method in accordance with the present invention, and a schematic view of partially swapping scheme of transmission method in accordance with the present invention. In  FIG. 16 , the embodiment comprises the following steps. In step  900 , input data is encoded to generate an encoded data containing first coded bits. In step  901 , the first coded bits are interleaved to generate first interleaved bits, such as the interleaved bits  910  shown in  FIG. 17 . In step  902  the first coded bits partially swapped to generate processed bits, such as the processed bits  913  shown in  FIG. 17 . In step  903  the processed bits are mapped to modulation symbols in a predetermined modulation scheme and the modulation symbols are transmitted in step  904 . Preferably, the step  902  can further comprise the following steps  902   a,    902   b  and  902   c.  In step  902   a,  the first coded bits are separated into a first bit partition and a second bit partition. 
         [0064]    As shown in  FIG. 17 , bit partition  911  and bit partition  912  are respectively referred to first bit partition and second bit partition. The ratio of first bit partition to second bit partition is m:n, such as 1:0, 1:1 or 1:2, m and n are integer larger than or equal to zero. 
         [0065]    In step  902   b,  bits of said second bit partition is swapped based on a predetermined swapping pattern to generate a swapped second bit partition. In step  902   c  the first bit partition and the swapped second bit partition are combined to form the processed bits. 
         [0066]    When the encoded data contains second coded bits, this embodiment can further steps of interleaving the second coded bits to generate second interleaved bits, and then combining the partially swapped first coded bits and the second interleaved coded bits based on a predetermined multiplexing pattern, to form the processed bits, such as the processed bits  923  shown in  FIG. 17 . 
         [0067]    Preferably, the second interleaved bits can be partially swapped, if necessary, to generate partially swapped second coded bits, and the partially swapped first coded bits and the partially swapped second coded bits are combined based on the predetermined multiplexing pattern, to form the processed bits. For example, bit swap is performed on the bit partition  931  of the interleaved bits  930  based on the predetermined swap pattern. The partially swapped interleaved coded bits  910  and  930  are combined based on a predetermined multiplexing pattern, to generate the processed bits. It is noted that, for easily understanding, the bit partition marked by slant lines in  FIG. 17  indicates the bit partition where the bit swap is performed. 
         [0068]    Preferably, the bit partition where the bit swap is performed can be change in retransmission. For example, when a retransmission request is received from a receiver, bits of the first bit partition is swapped based on the predetermined swapping pattern and the swapped first bit partition and the second bit partition are combined based on the predetermined multiplexing pattern, to form the processed bits. The processed bits then are mapped to modulation symbols in the predetermined modulation scheme. The modulation symbols are retransmitted to the receiver. 
         [0069]      FIG. 18  illustrates an example of partially swapping scheme the present invention applied in the CTC encoder. A′ code, B′ code, YI′ code, Y 2 ′ code, WI′ code and W 2 ′ code respectively represent the interleaved A code, B code, YI code, Y 2  code, WI code and W 2  code. Blocks marked by slant lines represent bit partitions which are performed bit swap. The scheme (A) and scheme (B) are two partially swap schemes. Locations of swapped bit partition of A′ code, B′ code, YI′ code, Y 2 ′ code, WI′ code and W 2 ′ code in two example are different, so these two scheme can be respectively applied in first transmission and retransmission. 
         [0070]    It is noted that the bit reversing scheme, bit swap scheme, bit partially swap scheme and multiplexing scheme described in four preceding embodiments of transmission method, if necessary, can be applied together for better effect.  FIG. 19  illustrates a flow chart of fifth embodiment of transmission method in accordance with the present invention. In step  941  input data is encoded to generate first coded bits and second coded bits. In step  942  the first coded bits and second coded bits are interleaved respectively to generate first interleaved coded bits and second interleaved coded bits. In step  943  the first interleaved coded bits and second interleaved coded bits are partially swapped respectively. In step  944  the partially swapped first interleaved coded bits and partially swapped first interleaved coded bits are combined based on a predetermined multiplexing pattern, to generate processed bits which are then mapped to modulation symbols in a predetermined modulation scheme in step  945  for further transmission. 
         [0071]      FIG. 20  illustrates an example of transmission method applied in the CTC encoder. In  FIG. 20 , the bit sequence outputted from CTC encoder are separated into A code, B code, YI code, Y 2  code, WI code and W 2  code. A code and B code are systematic bits, and YI code, Y 2  code, WI code and W 2  code are parity bits. A code, B code, YI code, Y 2  code, WI code and W 2  code are fed into subblock interleaver  591 ,  592 ,  593 ,  594 ,  595  and  596  for interleaving, and the interleaved codes are performed partially swap. The blocks marked with slant lines represent the bit partitions being performed bit swap, such as the bit swap scheme example (A) shown in  FIG. 9 . In the block marked with slant lines, first bit is swapped with third bit, fourth bit is swapped with 6th bit, 7th bit is swapped with 9th bit and such swapping rule is repeated sequentially for further bits. Partially swapped interleaved bits  961  and  962  are mapped directly as processed data  971  and  972 . Partially swapped interleaved bits  963  and  964  are multiplexed based on the multiplexing scheme shown in  FIG. 15 , to form the processed  973 . Similarly, partially swapped interleaved bits  965  and  966  are multiplexed based on the multiplexing scheme shown in  FIG. 15 , to form the processed  974 . 
         [0072]      FIG. 21  illustrates a block diagram of second embodiment of transmission apparatus in accordance with the present invention. Transmission apparatus  990  comprises an encoder  731 , a channel interleaver  991 , a modulator  734  and a transmitter  735 . The channel interleaver  991  further comprises a subblock interleaver  992 , a partially swapping unit  993  and a multiplexing unit  994 . The encoder  731  is operable to encode input data  741  to generate coded bits  742 . The subblock interleaver  992  is operable to interleave the coded bits  742 . Based on a ratio value  9932 , the partially swapping unit  993  determines location of the bit partition for bit swapping, and then the partially swapping unit  993  performs partially swap based on a predetermined swapping pattern  9931  on the interleaved coded bits outputted from the subblock interleaver  992 . Multiplexing unit  994  is operable to multiplex the bits outputted from the partially swapping unit  993  based on a predetermined multiplexing pattern  9941 , to generate processed bits  9942 . The modulator  734  is operable to map the processed bits  9942  to modulation symbols in a predetermined modulation scheme, and the transmitter  735  transmits the modulation symbols to remote receiver. 
         [0073]    While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.