Research On Joint Coded And Modulation With Iterative Decoding

Joint coded modulation is a key technology in furture communication systems. In these years, many new technologies are developed and applied to joint coded modulation systems, such as new error-correcting codes, space-time modulation on MIMO channels and iterative decoding algorithm. This paper is mainly considered: 1) How joint coded modulation transmitter is designed based on the iterative decoder. 2) The combination of LDPC code with Bit-interleaved coded modulaton. 3) The Optimization of two dimensional signal constellations in joint coded modulation with iterative decoder.The bit-interleaved coded modulation with iterative decoding for bandwidth-efficient transmission over Rayleigh fading channel is studied. A serially concatenated iterative scheme (BPCM-ID) combining Low-Density Parity-Check codes (LDPC) with multilevel modulation is proposed. Differ from other serially concatenated iterative decoding schemes, the whole iterative process of BPCM-ID is divided into outer iteration and inner iteration to avoid too much errors feedback to the demapper which may cause severe degradation of decoding performance. Another advantage, contrast to using convolutional codes or turbo codes, is its low complexity while maintain high BER performance because the check equations are used to terminate the both iterations. We develop the theoretical error free feedback bound for BPCM-ID and predict the threshold for decder convergence using the extrinsic information ransfer chart (EXIT).In this section, we give the defination of a new class of LDPC codes which are called Mutilevel LDPC (M-LDPC) code. The charictrization, construction and searching algorithm of M-LDPC codes were studied and analsised. Base on M-LDPC codes, a new joint coded modulation scheme is proposed (BP-MLC-ID), which differ form conventional MLC schems in that only one channel coder was used. Theory analsis and simulation result show that proposed BP-MLC-ID scheme could approach the same channel capacity as MLC while has very low complexities as BICM. After analysis the Discretized Density Evolution theory and the Differential Evolution algorithm, a method is proposed to search optimal M-LDPC code for joint optimizing of the system.In the next section, M-LDPC codes were applied in MIMO space and a scheme of...