Precoder-aided iterative detection assisted multilevel coding and three-dimensional EXIT-chart analysis

A novel three-dimensional (3D) EXIT chart is developed for investigating the iterative behaviour of multilevel coding (MLC) invoking multistage decoding (MSD). The extrinsic information transfer characteristics of both the symbol-to-bit demapper used and those of the different protection constituent decoders suggest that potential improvements can be achieved by appropriately designing the demapper. The proposed 3D EXIT chart is then invoked for studying the precoder-aided multilevel coding scheme employing both MSD and parallel independent decoding (PID) for communicating over AWGN and uncorrelated Rayleigh fading channels with the aid of 8PSK modulation. At BER=10-5, the precoder was capable of enhancing the achievable E_b/N₀ performance by 0.5 dB to 2.5 dB over AWGN and Rayleigh channels, respectively