Turbo equalization of doubly selective channels

In this paper we discuss turbo equalization for transmission over doubly selective channels. The maximum a-posteriori (MAP) algorithm is used for detection as well as for channel decoding. The detection/decoding constituents can exchange soft information in an iterative manner resulting in the so-called turbo-equalization. The time-varying multi-path fading channel is modeled using the basis expansion model (BEM). In this BEM, the time-varying channel is viewed as a bank of time-invariant FIR filters and the time-variation is captured by means of time-varying complex exponential basis functions. Therefore, the time-varying transition tables that characterize the time-varying channel can also follow the BEM. This allows for a lower complexity MAP detector with comparable complexity to the MAP detector for time-invariant channels.