Decision feedback frequency estimator for the coherent DS-CDMA system

This paper presents a fast frequency estimator which can be used for a pilot-channel aided coherent DS-CDMA system in the reverse link. Since the pilot signal power is normally set to 4 to 9 dB lower than the traffic signal power in the reverse link, the power of the extracted pilot signal in the receiver is not strong enough to estimate an accurate frequency error. To get a better frequency estimate, a decision feedback frequency estimator (DFFE) is employed to remove the polarity of the information in the traffic channel. Then both the pilot signal and the polarity-removed traffic signal are used to estimate a frequency error such that the maximum achievable signal to noise ratio (SNR) for the fast frequency estimator is the sum of the power of the traffic signal and that of the pilot signal. Simulation using Jake channel model shows that the performance of this frequency estimator is significant in mean square error (MSE) sense.