A Doppler offset estimator by using the signal´s cyclostationarity in CDMA system

In wireless communication, there may be a large frequency-offset between the transmitter and receiver due to Doppler effects. So it is very complex to synchronize the mobile unit with the base station, and the receiver´s performance degrades rapidly. We propose a Doppler offset estimator using the CDMA signal´s cyclostationarity. The CDMA signal´s cyclic frequency drifts with the Doppler offset. Exploiting the CDMA signal´s cyclostationarity and taking account of the finite sample data, we estimate the Doppler offset by calculating the signal´s cyclic frequency. The estimator needs no training sequences, so it does not lower the data rate; the added stationary noise cannot affect the estimator. Simulation results show the estimator can estimate the Doppler offset quickly and correctly in fading environments.