Apparatus for estimating carrier and clock frequency offsets in OFDM systems employs a maximun likelihood estimator operation on the demodulated signals. The invention has the benefit of low complexity and obviates the need for any requirement for a dedicated training channel....http://www.google.com.au/patents/US6198782?utm_source=gb-gplus-sharePatent US6198782 - Estimation of frequency offsets in OFDM communication systems
