On Residual Carrier Frequency Offset Mitigation for 802.11N

Due to the preamble design for mixed-mode transmission of 802.11n, carrier-frequency offset (CFO) estimation errors (or residual CFO) may cause significant errors in estimating the high-throughput (HT) MIMO channel because of the time-varying phase error as a result of residual CFO. In this paper, we propose a joint residual CFO and channel estimation technique using HT preambles. We show that the proposed technique is robust against residual CFO. We also present a simple technique for performing residual CFO estimation utilizing the 802.11n cyclic structure of pilot patterns. We demonstrate that with the proposed techniques, the performance loss due to residual CFO can be essentially recovered.