OFDM with Cyclic-Pilot Time Diversity

We present a novel transceiver design for orthogonal frequency-division multiplexing (OFDM) wireless systems employing pilot symbol aided channel estimation (PSACE). The design is based on the insertion of known pilots into the time- frequency OFDM grid in a controlled cyclic fashion to exploit time diversity in the pilot tones without consuming additional bandwidth resource. Semi-blind iterative detection based on the expectation-maximization algorithm along with optimum combining is employed at the receiver. Despite moderately increased transceiver complexity, simulations show that the proposed design has superior error rate performance compared to conventional PSACE methods for the same pilot overhead.