A Comparison of Frequency Offset Synchronization Algorithms for WiMAX OFDM Systems

Synchronization of the carrier frequency offset (CFO) is a crucial issue in the implementation of orthogonal frequency division multiplexing (OFDM) systems. Several estimation techniques for frequency offset have been proposed in the literature but varied test conditions make comparison difficult. This paper compares different synchronization algorithms for the wireless communication standard IEEE 802.16 (WiMAX) with a QPSK signal constellation in a Rayleigh channel. Furthermore, two of the synchronization techniques compared are novel schemes proposed in this paper. Bit error rate (BER) results of different data-aided and non-data-aided synchronization schemes in frequency and time domain are shown and compared. Acquisition is always based on the properties of the short or long preambles defined in WiMAX. Tracking is based on either the pilot tones included in a WiMAX OFDM symbol, or decision-directed algorithms. Results show that synchronization schemes with decision-directed tracking improve the BER with respect the pilot-aided tracking technique at the cost of increased complexity. Furthermore, non-data-aided synchronization schemes maintain the BER within 10% of the value obtained from an offset free system.