Synchronization Algorithm Based On Ieee 802.11n Mimo Ofdm Wireless Lan Systems

Broadband wireless access (BWA) has fundamentally changed the way people access the information. Wireless local area network (WLAN) is one of the BWA technologies, and has rapid developments in recent years. The upcoming IEEE 802.11n standard represents the latest advancement of WLAN technologies. The 802.11n standard adopts many key technologies of next generation wireless communication systems, e.g. MIMO and OFDM, which remarkably enhance the throughput of WLAN systems. Synchronization is one of the most important tasks of MIMO OFDM receivers. We researched the synchronization problems of IEEE 802.11n MIMO OFDM WLAN systems, and proposed the synchronization scheme for 802.11n systems.The proposed scheme includes timing synchronization, carrier frequency synchronization and sampling clock synchronization. The synchronization algorithms proposed in this paper are data-aided algorithms. These algorithms use 802.11n preamble for rapid synchronization, and are hence well-suited for burst mode transmission systems, e.g. WLAN systems.The proposed timing synchronization algorithms consist of frame synchronization and symbol timing. Through in-depth analysis of the statistical properties of frame synchronization metric, and utilizing the synchronization results provided by all the receive antennas, the frame synchronization algorithm achieves a high probability of detection. The proposed symbol timing algorithm has solved the timing problem caused by the cyclic shift of 802.11n systems.In this paper, the carrier frequency synchronization algorithm is divided into two categories, namely, coarse frequency offset estimation and fine frequency offset estimation. The coarse estimation algorithm has a wide estimation range of frequency offset; the fine estimation algorithm makes best use of the 802.11n preamble structure, and significantly reduces the variance of the estimator. Both the coarse estimation algorithm and the fine estimation algorithm exploit the receive diversity, and therefore have remarkably improved the accuracy of estimation.The sampling clock synchronization algorithm presented in this paper analyzed the statistical properties of the sampling clock offset estimators, and introduced a weighted method which could minimize the variance of the estimator. The algorithm also exploits receive diversity to further improve the accuracy of estimation.