A robust CD3-OFDM receiver architecture for DSRC systems

IEEE 802.11 organization has adpoted OFDM technology as part of their DSRC standard (802.11p PHY). In this paper, we present a robust code decision directed demodulation (CD3-OFDM) receiver architecture to take care of the time-variant channel characteristics in DSRC environment and the device-mismatched degradation between the transmitter and the receiver. The architecture consists of an innovative inner receiver and an outer receiver. The outer receiver is a Viterbi decoder. The inner receiver includes a synchronizer, a one-tap frequency domain equalizer (FDE) and a pilot-based phase estimator. The equalizer applies normalized least-mean-square (NLMS) algorithm to track not only the variation of the channel but also the residual frequency/phase errors that are not yet being entirely corrected by the synchronizer device. In order to keep the NLMS equalizer working well, we utilize a pilot-based phase estimator to help estimate them. For getting more performance improvement, a feedback connection from the Viterbi decoder output to the equalizer is adopted to help tracking. The simulation results indicate that our proposed CD3-OFDM receiver works fairly well for DSRC systems.