This paper presents a decision directed frequency tracking scheme to improve the spectrum efficiency of Orthogonal Frequency Division Modulation （OFDM） transmission for frequency selective channels. OFDM divides a broadband channel into parallel narrowband subchannels with different channel characteristics. The subcarriers with lower attenuation are selected to do the decision directed based frequency tracking. A phase error detection method is needed to keep the hard decision working stable during tracking. The algorithm ensures that the carrier frequency offset could be solved from the detected phase error. The Mean Square Error （MSE） estimate and the loop bandwidth are also presented. Simulations illustrate that this scheme has better MSE and bit error rate performance than the traditional scheme. Furthermore, the pilots are saved in this scheme, which lead to improved spectrum efficiency.
