MTMR Channel Estimation and Pilot Design in the Context of Space-Time Block Coded OFDM-Based WLANs

In this paper, we focus on pilot-aided channel estimation methods in the context of OFDM-based WLANs with Multiple Transmit Multiple Receive (MTMR) antennas, and we compare several solutions together with several pilot designs in a realistic context. In particular, we take into account null subcarriers as specified in the WLANs standards. We consider channel estimation based on the Minimum Mean Square Error (MMSE) and Least Square (LS) criteria. For the latter, we present an optimality criterion for the pilots, and corresponding optimal designs enabling complexity reductions. In addition, suboptimal performance/complexity trade-offs are studied. Finally, the comparison of the performance of different space-time block coded schemes using 2 and 4 transmit antennas, combined with these various options, complements the study by highlighting the impact of channel estimation errors on the Packet Error Rate (PER).