Research On Coding And Decoding Algorithm Of Space-time Trellis Code For MIMO System

MIMO technology has been widely used in 4G because of its role in improving the data transmission rate.MIMO technology is generally combined with space-time coding technology to generate multiple paths for data transmission,Compared with a single propagation path,the probability of multiple propagation paths being interfered at the same time will be smaller,thus ensuring the quality of the signal at the receiver.As a kind of spacetime coding,space-time trellis code has always been a hotspot of people's research.However,when the number of transmitting antennas is large,obataining an optimal space-time trellis code requires a lot of calculation and search,and the Viterbi decoding at the receiver also requires a lot of iterative calculations.Moreover,in a frequency-selective fading channel environment,the performance of decoding algorithms such as Viterbi decoding algorithms will deteriorate.Therefore,reducing the calculation amount of optimal space-time trellis code search,optimizing the decoding algorithm at the receiver and realizing the space-time trellis code decoding in the MIMO channel environment are key issues in the research of space-time trellis codes.Based on the above problems,the coding and decoding problems of space-time trellis codes of MIMO systems are mainly studied in this thesis.First of all,the characteristics of wireless channel and space-time coding technology is expounded,then the research status at home and abroad is analyzed and summarized.Combined with the space-time coding system model,the performance of space-time coding in slow fading channels is analyzed,and the coding design criteria for slow fading channels are also summarized.In view of the large number of calculations for searching for the optimal encoder,three search algorithms to reduce the number of calculations are studied.They are the conjugate characteristic of codeword difference matrix search algorithm,the column exchange of generator matrix search algorithm,and the coset partitioning search algorithm.And a search algorithm combining the above three methods is proposed,which further reduces the number of calculations for searching for the optimal encoder.Based on the idea of reducing decoding delay and reducing hardware storage overhead,an overlapped Viterbi decoding method is proposed on the basis of path memory truncation.Simulation results show that the overlapped Viterbi decoding method based on path memory truncation still has better performance,and it can reduce the decoding delay and storage overhead,but does not increase the amount of calculation too much.Aiming at the problem of the deterioration of the performance of the Viterbi decoding algorithm under the frequency selective fading channel,combined with the channel equalization technology,a space-time trellis code decoding scheme for the frequency selective fading channel is proposed.And this decoding scheme can improve the performance of Viterbi decoding algorithm under frequency selective fading channel.