Research On The LDPC Code And Mapping Schemes In BICM-ID Systems

As one of the key technologies in wireless communication systems,Bit-Interleaved Coded Modulation with Iterative Decoding?BICM-ID? technique can save bandwidth and has low complexity.Moreover,Low-Density Parity-Check coded BICM-ID has the advantages of strong agility,high spectrum efficiency,excellent decoding performance and low complexity.Error correction coding and mapping constellation design in LDPC-BICM-ID systems are discussed,and some corresponding conclusions are reached.The main research contents and results in this dissertation are as follows:1.An eIRA-QC-LDPC code construction method applied in BICM-ID systems is proposed by the modus of Quasi-Cyclic?QC?.The novel method has simple structure that can save storage space,and regulate the code length and rate flexibly according to the actual demand.The elements of index matrix at each row constitute arithmetic progressions with the monotonically increasing tolerances,so the parity check matrix does not contain girth 4.The simulation shows that at the bit error rate of 10^-6,the net coding gain?NCG?of the constructed eIRA-QC-LDPC?4599,4307? code between with RU-QC-LDPC?4288,4020? code and GF?2?-QC-LDPC?4599,4307? code are 0.50dB and0.75dB respectively.At the bit error rate of 10^-6,the NCG of the constructed eIRA-QC-LDPC?1224,612? code between with Masking-QC-LDPC?1224,612? and FS-irregular QC-LDPC?1224,612? code are 1.00dB and 1.20dB respectively.2.In order to increase the effectiveness and reliability of the BICM-ID systems,a novel so-called Tricyclic-16QAM mapping scheme with tricyclic structure is optimized by combining the Minimum Square Euclidean Weight?MSEW? criterion,the maximization of bit minimum decision region criterion and the Euclidean distance criterion.The construded eIRA-QC-LDPC?4599,4307? combined with the Tricyclic-16QAM mapping scheme in BICM-ID system has the advantages of channel capacity,BER simulation and Extrinsic Information Transfer?EXIT? simulation.Presented results show that,at the bit error rate of 10^-7,the coding gain of the novel Tricyclic-16QAM mapping scheme is 0.77dB and 0.84dB more than DP-16QAM and Precoding-16QAM mapping scheme respectively.3.To satisfy the increasing demand for spectrum utilization in wireless communication systems,it is necessary to continuously increase the channel capacity of the BICM-ID systems and improve the coding gain of the system.Therefore,an innovative PSS-16QAM mapping scheme based on precoding and sub-segmentation is proposed.By adding precoding algorithm to increase the average Hamming distance between adjacent symbols,and using the improved sub-segmentation method of 16QAM to improve the minimum Euclidean distance between any pair of symbols whose labels differ in only one bit position,the purpose of improving the CG of the BICM-ID system,ameliorating the“waterfall”effect and increasing the channel capacity are achieved.Presented results have shown that in Rayleigh channels the proposed mapping can save few decibels of transmit power for a target bit error rate of 10^-7 compared to the DP-16QAM,precoding-16QAM and Tricyclic-16QAM mapping schemes while it offers a comparable channel capacity and EXIT performance.The proposed PSS-16QAM mapping scheme offers a NCG of 0.38dB,1.15dB and 1.22dB over DP-16QM,predcoding-16QAM and Tricyclic-16QAM respectively.Moreover,the decoding performance of the eIRA-QC-LDPC?4599,4307? code is better matched with the proposed tricyclic-16QAM mapping scheme.