Carrier Frequency Offset Estimation in Multiuser Simultaneous Channel Access for MIMO-OFDM based WLANs

The goal of this paper is to propose a method for carrier frequency offset estimation in a scenario where multiple users upload to a central coordinator simultaneously. OFDM based systems are highly prone carrier frequency offsets. The CFO estimation method proposed here is performed in time domain thereby facilitating a reduction in complexity at the central coordinator. The estimator makes use of the orthogonal training sequences that were transmitted by the different users. It is shown that the resulting CFO estimator is optimal not only in the sense that it minimizes the estimation error variance due to inter carrier interference.