Coding and signal processing for multiple-antenna transmission and reception: Iterative receiver structures

We describe, in a semitutorial fashion, a fairly general class of iterative receivers for multiple-antenna systems. These receivers combine a soft decoder for a space-time code with a spatial-interference canceler. The performance of these receivers is analyzed by using EXIT charts, a convenient graphical description that yields quite accurate results. By properly combining the EXIT characteristics of the canceler and of the decoder, the convergence behavior of the iterative algorithms can be understood, and design guidelines derived. The idea here is to observe that both the interference canceler and the decoder can be studied by examining the evolution of the extrinsic information passed along to the connected blocks.