Adaptive iterative decoding : block turbo codes and multilevel codes

New adaptive, iterative approaches to the decoding of block Turbo codes and multilevel codes are developed. Block Turbo codes are considered as they can readily provide high data rates, low decoding complexity and good performance. Multilevel codes are considered as they provide a moderate complexity approach to a high complexity code and can provide codes with good bandwidth efficiency. The work develops two adaptive sub-optimal soft output decoding algorithms for block Turbo codes. One is based on approximation and the other on the distance properties of the component codes. They can be used with different codes, modulation schemes, channel conditions and in different applications without modification. Both approaches provide improved performance compared to previous approaches on the additive white Gaussian noise (AWGN) channel. The approximation based adaptive algorithm is also investigated on the uncorrelated Rayleigh fiat fading channel and is shown to improve performance over previous approaches. Multilevel codes are typically decoded using a multistage decoder (MSD) for complexity reasons. Each level passes hard decisions to subsequent levels. If the approximation based adaptive algorithm is used to decode component codes in a traditional MSD it improves performance significantly. Performance can be improved further by passing reliability (extrinsic) information to all previous and subsequent levels using an iterative MSD. A new iterative multistage decoding algorithm for multilevel codes is developed by treating the extrinsic information as a Gaussian random variable. If the adaptive algorithms are used in conjunction with iterative multistage decoding on the AWGN channel, then a significant improvement in performance is obtained compared to results using a traditional MSD

Binary Multilevel Convolutional Codes with Unequal Error Protection Capabilities

Binary multilevel convolutional codes (CCs) with unequal error protection (UEP) capabilities are studied. These codes belong to the class of generalized concatenated (GC) codes. Binary CCs are used as outer codes. Binary linear block codes of short length, and selected subcodes in their two-way subcode partition chain, are used as inner codes. Multistage decodings are presented that use Viterbi decoders operating on trellises with similar structure to that of the constituent binary CCs. Simulation results of example binary two-level CC\u27s are also reported

Three-Dimensional EXIT Chart Analysis of Iterative Detection Aided Coded Modulation Schemes

The iterative convergence of iteratively detected coded modulation schemes having different block lengths, decoding complexity and an unequal error protection capability is studied, when communicating over AWGNchannels using 8PSK modulation. More specifically, the coded modulation schemes investigated include Multilevel Coding (MLC), Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) as well as Bit-Interleaved Coded Modulation employing Iterative Decoding (BICM-ID). A novel three dimensional EXIT chart was introduced for studying the iterative convergence behaviour of the Multistage Decoding (MSD) scheme used in MLC

Generalized Low-Density Parity-Check Coding Aided Multilevel Codes

Classic Low-Density Parity-Check (LDPC) codes have recently been used as component codes in Multilevel Coding (MLC) due to their impressive BER performance as well as owing to their flexible coding rates. In this paper, we proposed a Multilevel Coding invoking Generalized Low-Density Parity-Check (GLDPC) component codes, which is capable of outperforming the classic LDPC component codes at a reduced decoding latency, when communicating over AWGN and uncorrelated Rayleigh fading channels