A New Method for Frequency Offset and Channel Estimation in OFDM

Efficient estimations of the carrier frequency offset (CFO) and channel are vital to orthogonal frequency division multiplexing (OFDM). In this paper, a new method based on limited channel length and null subspace is proposed to estimate the CFO in OFDM. The method needs only one OFDM block (symbol) as pilot. The identifiability of the method is analyzed and requirements for the pilot are found. The same pilot is also used for channel estimation. It is shown that a pilot with constant amplitude and random phases is the best choice for both channel and CFO estimation. Furthermore, an enhanced method is proposed by using multiple receiving antennas. Simulations demonstrate that the proposed methods are effective.