A study of joint tracking algorithms of carrier frequency offset and sampling clock offset for OFDM-based WLANs

We present three joint tracking algorithms of carrier frequency and sampling clock offsets for OFDM-based WLAN systems, such as IEEE 802.11a standard. In such systems, one symbol usually contains a few pilots so that the estimation accuracy and robustness of conventional methods do not satisfy the system requirement. In this paper, three joint tracking algorithms for accurate frequency and sampling estimation are presented. The first method is performed by a one-dimensional least square estimation and averaging over L symbols. The second algorithm compares the phase difference of the current symbol with the subsequent D-th symbol and gives better performance, especially when the SNR or synchronization offset is smaller. The third method uses two-dimensional linear least square estimation within the frequency and time domains. Simulations using these algorithms have been performed with 16-QAM modulation schemes. Simulation results show that the three algorithms can improve the estimation accuracy and robustness.