Residual Carrier and Sampling Frequency Offset Tracking In OFDM Wireless LAN Systems

In this paper, we propose the residual carrier frequency offset tracking and sampling clock offset tracking algorithm that can be used in IEEE 802.11a and HIPERLAN Type 2 systems. Above Wireless LAN systems has short and long preambles, the carrier frequency offset is estimated and compensated. In case that the frame length is long, however, residual carrier frequency offset induces the severe performance degradation due to a phase rotation. And the sampling frequency offset also degrades the system performance. To prevent such performance degradations, the carrier frequency offset and sampling frequency tracking algorithms using pilot symbols are necessary. We can extract synchronization parameters by observing the phase variation of pilot symbols, such as an average and a slope. The initially estimated channel updates by using these synchronization parameters. In the frequency domain equalizer, we compensate the synchronization parameters. Computer simulation results demonstrate the performance of the proposed algorithm.