On equalization for OFDM-dedicated short range communication (DSRC) modem

Dedicated short range communication (DSRC) applications need flexible and robust air interface technology to support high data rate services. OFDM is a good candidate for DSRC applications in harsh mobile environments, with time and frequency-selective channels. This doubly spread channel renders channel estimation, needed for the equalizer when using coherent detection, a challenging problem. We focus on the the channel estimation methods for coherent detection of QAM signals. Two adaptive algorithms, NLMS and RLS are considered for the rotating pilot (RP) scheme and the repeated reference (RR) scheme to track the channel variations. Further maximum likelihood (ML) deterministic channel estimation is applied jointly with the above methods to get optimal channel estimation. The combination of NLMS and ML is best suited for an OFDM-DSRC modem with rather low complexity and a performance loss of only 1 dB with respect to a perfect channel knowledge situation.