Study Of APSK Constellation Mapping For LDPC-BICM-ID Systems

In recent years,the Low-Density Parity-Check coded Bit-Interleaved Coded Modulation with Iterative Decoding(LDPC-BICM-ID)systems have received extensive attention.The design of constellation mapping schemes for LDPC-BICM-ID systems can greatly improve the system performance without affecting system complexity.On the other hand,amplitude phase shift keying is widely used due to its efficient spectrum utilization.For multimedia broadcast applications,the non-uniform APSK constellation mapping scheme can further improve system performance.At this stage,there are many options for the optimization method of APSK mapping scheme,but it is still to be studied to find an APSK mapping scheme for LDPC-BICM-ID systems.In this thesis,the APSK constellation mapping scheme for LDPC-BICM-ID systems is studied and the results are obtained.The main work is as follows:(1)Soft/Hard decision decoding algorithm of LDPC codes and Soft Input Soft Output demodulation algorithm for LDPC-BICM-ID systems are analyzed and compared.The simulation results show that when system's decode algorithm uses LLR-BP and demodulation algorithm uses MAX-Log-Map,it can greatly reduce the computational complexity while ensuring better performance.In this thesis,Extrinsic Information Transfer(EXIT)chart is studied to analysis decoding convergence characteristics.In addition,the influence of different mapping schemes of 16 QAM modulation on LDPC-BICM-ID system is discussed.The simulation results show that Gray mapping is still the best mapping scheme for LDPC-BICM-ID system.(2)A non-uniform(3,5)-8APSK mapping scheme is proposed for LDPC-BICM-ID systems.The mapping scheme optimizes the relative radius ratio based on the Euclidean distance design criterion,and optimizes the bit-to-symbol mapping scheme based on the maximize minimum decision area criteria.By simulating the channel capacity,BER and EXIT charts,the results show that the(3,5)-8APSK mapping scheme is superior to the existing mapping scheme in Additive White Gaussian Noise channel and Rayleigh fading channel.Among them,when it uses(2304,1920)LDPC codes,AWGN channel and the target BER is 10-5,the(3,5)-8APSK mapping scheme improves the gains of 0.9d B,0.5d B,1.1d B,1.5d B respectively compared to(2,6)-8APSK and 8PSK's Gray,Set Partitioning and Semi Set Partitioning mapping scheme.(3)A higher-order APSK constellation mapping optimization method is proposed based on bat algorithm(BA).The method optimizes the target by minimizing the bit error probability and can globally optimize the relative radius and the phase of the constellation point.The optimization results of 16 APSK alternative scheme and the 32 APSK mapping scheme of DVB-S2 standard are given in this thesis.The results of BER simulation and channel capacity simulation prove that the optimized constellation mapping scheme can improve system's BER performance and channel capacity compared with the unoptimized constellation mapping scheme.