WLCp1-12: MAP based Equalizer for OFDM Systems in Time-Varying Multipath Channels

In this paper, we propose maximum a posteriori probability (MAP) based equalizers for orthogonal frequency division multiplexing (OFDM) systems over time-varying multipath channels. Under the approximation of linear variation in an OFDM symbol, it is easy to obtain the equivalent channel matrix. Based on the Tailbiting trellis structure and the fact that intercarrier interference (ICI) energy is concentrated in adjacent subcarriers, a new Tailbiting BCJR equalizer, operating in the frequency domain, is developed. Furthermore, a Tailbiting DF- BCJR algorithm is proposed to achieve better performance, and an MBCJR algorithm is also introduced to reduce the implementation complexity. Simulation results indicate that, by successfully taking advantage of the diversity gain caused by time-selective channels, our equalizers demonstrate good performance in fast fading environments.