A novel carrier frequency estimating algorithm for QAM signals

Carrier frequency recovery and compensation are of the key factors in digital QAM receivers due to transceiver oscillator instabilitiy and/or channel Doppler effects. There are some carrier estimation algorithms for the non-cooperative communication environment, but they are all adopted when carrier frequency offset is small comparing with the symbol rate. In this paper, a carrier estimation algorithm has been proposed, which is non-data-aided and can be implemented in digital form. Because of its open-loop structure, the proposed algorithm is very simple and easy to be implemented. Using the property of the transmitted symbols, its estimation time is independent of the frequency and the estimation range is large, on the order of the symbol rate. The proposed estimator can be improved to adap the estimation of the carrier frequency directly. The simulation results show that the proposed algorithm can estimate the carrier frequency offset, while the amending algorithm can also be used to estimate the carrier frequency directly, and the performance is very good for all QAM signals. © 2010 by Editorial Department of Chinese Journal of Radio Science.