Method and apparatus for transmitting data streams in mimo system

Abstract

A method for transmitting data streams in a multiple input multiple output (MIMO) system is provided, where each data stream is mapped to multiple layers in an MIMO channel space for transmission, and the method includes: performing inter-layer interleaving for N data streams to obtain N interleaved data streams; mapping the N interleaved data streams respectively to N layers in the MIMO channel space, and transmitting the N interleaved data streams that are mapped to the N layers. By using the method of the present invention, a combined CQI can be used in a better way to improve MIMO transmission performance. Further, an impact of inter-layer interference is canceled by using an interference cancellation technology (for example, an SIC technology) based on the inter-layer interleaving.

What is claimed is: 
     
         1 . A method for transmitting four data streams in a multiple input multiple output (MIMO) system, wherein four data streams are mapped to four layers in an MIMO channel space for transmission, wherein the four data streams are grouped into two groups, and the two groups are processed by two transport channel processing units separately, and the method comprises:
 performing inter-layer interleaving for two data streams in each group to obtain two interleaved data streams;   mapping the two interleaved data streams respectively to two layers in the MIMO channel space; and   transmitting the two interleaved data streams that are mapped to the two layers;   wherein when transmitting the two interleaved data streams is performed, spectrum spreading and scrambling processing are separately performed for the two interleaved data streams, precoding is performed for each code channel or channel by multiplying a coding coefficient, a common pilot channel is added to each precoded code channel or channel, and the two interleaved data streams that have been processed are transmitted on a MIMO channel; wherein the different code channels are multiplied by different spreading codes during the spectrum spreading operation.   
     
     
         2 . The method according to  claim 1 , wherein inter-layer interleaving is performed for the two data streams, so that bits of each data stream among the two data streams are distributed to different layers among the two layers, and for a part of or all modulation symbols comprised in the two layers, modulation symbols on different layers among the two layers of a same code channel at a same time come from different data streams among the two data streams, and bits in a same modulation symbol come from a same data stream. 
     
     
         3 . The method according to  claim 1 , wherein performing inter-layer interleaving for two data streams comprises:
 placing M pieces of data from each of the two data streams into a first 2×M matrix, wherein the M pieces of data from each data stream are placed in a row of the first matrix;   grouping the first matrix into   
       
         
           
             
               Q 
               = 
               
                 ⌈ 
                 
                   M 
                   P 
                 
                 ⌉ 
               
             
           
         
       
       groups with every P columns as one group, wherein ┌ ┐ represents an arithmetic of rounding up to an integer;
 grouping the Q groups into two sets; and 
 performing row displacement separately for the two sets to generate a second matrix; 
 wherein two rows of the second matrix are respectively used as the two interleaved data streams; 
 wherein the grouping the Q groups into two sets comprises: placing a q th  group of the first matrix into an n th  set, wherein 0≦q<Q, n=mod(q, 2), 0≦n<2, and mod represents a modulo arithmetic; and 
 performing row displacement separately for the two sets comprises: moving each row of the two sets across a number of rows, wherein the number of rows moved across varies among the two sets. 
 
     
     
         4 . The method according to  claim 3 , further comprising:
 performing bit scrambling, code block segmentation, channel coding, a physical layer hybrid automatic repeat request (HARQ) operation, physical code channel allocation, high speed downlink shared channel (HS-DSCH) interleaving, constellation point arrangement, physical channel mapping, and constellation point mapping separately for the two data streams, to obtain two constellation point symbol streams;   performing inter-layer interleaving for two data streams further comprises: performing interleaving for the two constellation point symbol streams, to obtain two interleaved constellation point symbol streams;   mapping the two interleaved data streams respectively to two layers further comprises: mapping the two interleaved constellation point symbol streams respectively to the two layers; and   transmitting the two interleaved data streams that are mapped to the two layers further comprises: transmitting the constellation point symbols that are mapped to the two layers,   wherein the M pieces of data are M constellation point symbols.   
     
     
         5 . An apparatus for transmitting four data streams in a multiple input multiple output (MIMO) system, wherein four data streams are mapped to four layers in an MIMO channel space for transmission, wherein the four data streams are grouped into two groups, and the two groups are processed by two transport channel processing units separately, and the apparatus comprises:
 an interleaving unit, configured to perform inter-layer interleaving for two data streams in each group to obtain two interleaved data streams;   a mapping unit, configured to map the two interleaved data streams respectively to two layers in the MIMO channel space; and   a transmitting unit, configured to transmit the two interleaved data streams that are mapped to the two layers;   when the transmitting unit performs the transmission for the two interleaved data streams, spectrum spreading and scrambling processing are separately performed for the two interleaved data streams, precoding is performed for each code channel or channel by multiplying a coding coefficient, a common pilot channel is added to each precoded code channel or channel, and the two interleaved data streams that have been processed are transmitted on a MIMO channel;   wherein the different code channels are multiplied by different spreading codes during the spectrum spreading operation.   
     
     
         6 . The apparatus according to  claim 5 , wherein the interleaving unit performs inter-layer interleaving for the two data streams, so that bits of each data stream among the two data streams are distributed to different layers among the two layers, and for a part of or all modulation symbols comprised in the two layers, modulation symbols on different layers among the two layers of a same code channel at a same time come from different data streams among the two data streams, and bits in a same modulation symbol come from a same data stream. 
     
     
         7 . The apparatus according to  claim 5 , wherein the interleaving unit performs inter-layer interleaving for the two data streams by using the following operations:
 placing M pieces of data from each of the two data streams into a first 2×M matrix, wherein the M pieces of data from each data stream are placed in a row of the first matrix;   grouping the first matrix into   
       
         
           
             
               Q 
               = 
               
                 ⌈ 
                 
                   M 
                   P 
                 
                 ⌉ 
               
             
           
         
       
       groups with every P columns as one group, wherein ┌ ┐ represents an arithmetic of rounding up to an integer;
 grouping the Q groups into two sets; and 
 performing row displacement separately for the two sets, to generate a second matrix; 
 wherein two rows of the second matrix are respectively used as the two interleaved data streams; 
 the interleaving unit groups the Q groups into two sets by using the following operation: placing a q th  group of the first matrix into an n th  set, wherein 0≦q<Q, n=mod(q, 2), 0≦n<2, and mod represents a modulo arithmetic; and 
 the interleaving unit performs row displacement separately for the two sets by using the following operation: moving each row of the two sets across a number of rows, wherein the number of rows moved across varies among the two sets. 
 
     
     
         8 . The apparatus according to  claim 5 , further comprising:
 a bit scrambling unit, configured to perform bit scrambling for the two data streams separately;   a code block segmenting unit, configured to perform code block segmentation separately for the bit-scrambled two data streams;   a channel coding unit, configured to perform channel coding separately for the code-block-segmented two data streams;   a physical layer HARQ function unit, configured to perform a physical layer HARQ operation separately for the channel-coded two data streams;   a physical code channel allocating unit, configured to perform physical code channel allocation separately for the two data streams for which the physical layer HARQ operation is performed;   an HS-DSCH interleaving unit, configured to perform HS-DSCH interleaving separately for the two data streams for which the physical code channel allocation is performed;   a constellation point arranging unit, configured to perform constellation point arrangement separately for the HS-DSCH-interleaved two data streams;   a physical channel mapping unit, configured to perform physical channel mapping separately for the two data streams for which the constellation point arrangement is performed; and   a constellation point mapping unit, configured to perform constellation point mapping separately for the two data streams for which the physical channel mapping is performed, to obtain two constellation point symbol streams;   wherein the interleaving unit performs interleaving for the two constellation point symbol streams to obtain two interleaved constellation point symbol streams;   the mapping unit maps the two interleaved constellation point symbol streams respectively to the two layers;   the transmitting unit transmits the constellation point symbols that are mapped to the two layers; and   the M pieces of data are M constellation point symbols.   
     
     
         9 . A method for receiving four data streams in a multiple input multiple output (MIMO) system, wherein four data streams are mapped to four layers in an MIMO channel space for transmission, wherein the four data streams are divided into two groups of data streams, and inter-layer interleaving is performed for the two groups of data streams separately; and the method comprises:
 performing front-end receipt of data signals on four antennas in the MIMO system separately, and performing linear minimum mean square error (LMMSE) equation, descrambling, and dispreading for the received data signals separately, to obtain the two groups of data streams, wherein each group of data streams comprises two interleaved data streams that are mapped to two layers;   performing inter-layer deinterleaving separately for the two data streams comprised in each group of data streams among the two groups of data streams, to obtain four data streams that are not interleaved; and   performing log-likelihood ratio (LLR) and decoding operations separately for the four data streams that are not interleaved, to obtain four bit data streams.   
     
     
         10 . The method according to  claim 9 , wherein performing inter-layer deinterleaving separately for the two data streams comprised in each group of data streams among the two groups of data streams comprises:
 placing M pieces of data from each of the two data streams into a second 2×M matrix, wherein the M pieces of data from each data stream are placed in a row of the second matrix;   grouping the second matrix into   
       
         
           
             
               Q 
               = 
               
                 ⌈ 
                 
                   M 
                   P 
                 
                 ⌉ 
               
             
           
         
       
       groups with every P columns as one group, wherein ┌ ┐ represents an arithmetic of rounding up to an integer;
 grouping the Q groups into two sets; and 
 performing row displacement separately for the two sets to generate a first matrix; 
 wherein two rows of the first matrix are respectively used as the two interleaved data streams; 
 wherein grouping the Q groups into two sets comprises: placing a q th  group of the second matrix into an n th  set, wherein 0≦q<Q, n=mod(q, 2), 0≦n<2, and mod represents a modulo arithmetic; and 
 performing row displacement separately for the two sets comprises: 
 moving each row of the two sets across a number of rows, wherein the number of rows moved across varies among the two sets, the number a of rows moved across for each set is corresponding to a number b of rows that are moved across when the second matrix is obtained by inter-layer interleaving, and mod(a+b,2)=0. 
 
     
     
         11 . The method according to  claim 9 , wherein the method further comprises:
 performing a cyclic redundancy check (CRC) for the four bit data streams separately, and cancelling successive interference according to a result of the CRC performed for the four bit data streams.   
     
     
         12 . The method according to  claim 9 , wherein the method further comprises:
 acquiring channel quality of physical channels corresponding to the two groups of data streams, to determine an average channel quality indicator (CQI) of each group of data streams; and   reporting the respective average CQI of the two groups of data streams to a base station.   
     
     
         13 . A user equipment, configured to receive four data streams in a multiple input multiple output, MIMO system, wherein the four data streams are mapped to four layers in an MIMO channel space for transmission, the four data streams are divided into two groups of data streams, and inter-layer interleaving is performed for the two groups of data streams separately, and the user equipment comprises:
 a receiver, configured to perform front-end receipt of data signals on four antennas in the MIMO system separately, and perform linear minimum mean square error (LMMSE) equation, descrambling, and dispreading for the received data signals separately, to obtain the two groups of data streams, wherein each group of data streams comprises two interleaved data streams that are mapped to two layers;   a deinterleaver, configured to perform inter-layer deinterleaving separately for the two data streams comprised in each group of data streams among the two groups of data streams, to obtain four data streams that are not interleaved; and   a decoder, configured to perform log-likelihood ratio (LLR) and decoding operations separately for the four data streams that are not interleaved, to obtain four bit data streams.   
     
     
         14 . The user equipment according to  claim 13 , wherein the deinterleaver is configured to perform inter-layer deinterleaving separately for the two data streams comprised in each group of data streams among the two groups of data streams, comprising:
 placing M pieces of data from each of the two data streams into a second 2×M matrix, wherein the M pieces of data from each data stream are placed in a row of the second matrix;   grouping the second matrix into   
       
         
           
             
               Q 
               = 
               
                 ⌈ 
                 
                   M 
                   P 
                 
                 ⌉ 
               
             
           
         
       
       groups with every P columns as one group, wherein ┌ ┐ represents an arithmetic of rounding up to an integer;
 grouping the Q groups into two sets; and 
 performing row displacement separately for the two sets to generate a first matrix; 
 wherein two rows of the first matrix are respectively used as the two interleaved data streams; 
 wherein the grouping the Q groups into two sets comprises: placing a q th  group of the second matrix into an n th  set, wherein 0≦q<Q, n=mod (q, 2), 0≦n<2, and mod represents a modulo arithmetic; and 
 performing row displacement separately for the two sets comprises: 
 moving each row of the two sets across a number of rows, wherein the number of rows moved across varies among the two sets, the number a of rows moved across for each set is corresponding to a number b of rows that are moved across when the second matrix is obtained by inter-layer interleaving, and mod(a+b,2)=0. 
 
     
     
         15 . The user equipment according to  claim 13 , wherein the user equipment further comprises:
 a successive interference cancellation module, configured to perform a cyclic redundancy check (CRC) for the four bit data streams separately, and cancelling successive interference according to a result of the CRC performed for the four bit data streams.   
     
     
         16 . The user equipment according to  claim 13 , wherein the user equipment further comprises:
 a channel quality indicator (CQI) computing module, configured to: acquire channel quality of physical channels corresponding to the two groups of data streams, to determine an average CQI of each group of data streams; report the respective average CQI of the two groups of data streams to a base station.