Turbo equalization in high doppler mobile environments: Channel estimation, fast algorithms and adaptive solutions

Abstract

High Doppler effects resulting from fast time varying dispersive channels represent the most critical impairment to channel equalization techniques in block transmissions. In multicarrier systems, it gives rise to the so-called intercarrier interference (ICI), whose modeling for correct data recovery is paramount. Considering a practical scenario where the designer has no control on the transmitter side, we present a novel turbo equalization scheme based on recent frameworks for the time varying channel parametrization via its derivatives. This includes a fast method for estimating the channel derivatives running on a decision-directed turbo equalization scheme that can be implemented at either symbol or bit level. Unlike recent approaches, the derivatives estimation is adaptive, in the sense that at each turbo estimation it incorporates information on previously estimated parameters.