Multi-Ary EXIT Chart Analysis with Chi-Square Distributed A Priori Information for Concatenation of USTM and Signal-Based Turbo Coding

Conventional extrinsic information transfer (EXIT) chart fits for Gaussian distributed a priori information. In this paper, we propose a multi-ary EXIT chart with Chi-square distributed a priori information to analyze the convergence behavior of unitary space-time signal-based turbo code (UST-SB- TC) for multiple-input multiple-output (MIMO) wireless communication systems. We give the model of a priori information via the conditional probability density function (PDF) of the received signals and use the a priori signal-to-noise ratio (SNR) as the connection between the a priori and the extrinsic information. Simulations show that the model of a priori information is appropriate and the EXIT chart can well depict the iterative decoding.