BLIND CFO ESTIMATION FOR OFDM WITH CONSTANT MODULUS CONSTELLATIONS: PERFORMANCE BOUNDS AND ALGORITHMS

In this paper, we derive the Cramér-Rao bound for blind carrier frequency offset (CFO) estimation in orthogonal fre-quency division multiplexing (OFDM) with constant modu-lus constellations. A blind maximum likelihood CFO estima-tor is also proposed. It achieves highly accurate frequency synchronization with a single OFDM block, regardless of multipath fading and without the need for null-subcarriers. The approach is thus very attractive for time and frequency (i.e., doubly) selective channels where the CFO may be time varying. If sufficient additional pilot information is avail-able, maximum likelihood estimates of channel parameters and transmitted data can be obtained as a byproduct. Finally, performance bounds are evaluated for several commonly en-countered scenarios. 1