Researches On Key Technologies In IEEE 802.11N

As one of the most important broadband wireless access technologies, wireless local area network (WLAN) has gained rapid development in recent years. IEEE 802.11n, a new generation standard, represents the latest achievement in WLAN. In PHY layer, MIMO-OFDM structure is introduced to support higher transfer rate. In order to improve the system throughput, the standard adopts some new technologies such as frame aggregation, BlockACK and PSMP, and optimizes the frame structure and schedule mechanism in MAC layer.This paper mainly focuses on the key technologies which are involved in IEEE 802.11n Draft 4.0, including two aspects.Firstly, we introduce the basic theory of WLAN physical layer, and propose a receiver solution according to the transmitter structure and the key system parameters in protocol, then evaluate the performance of data-aided synchronization methods based on training sequence. Frame synchronization algorithm appropriately sets the searching widow size according to the characteristics of short training sequence, thus gets frame header by searching the peak value of autocorrelation curve. Carrier frequency offset (CFO) estimation reduces minimum square error (MSE) by making good use of 802.11n preamble structure and receive diversity. Our phase offset estimation plan represses common phase error (CPE) by orthogonal pilot design and receive diversity technology.Secondly, we research the key MAC technologies in 802.11n protocol including MAC frame aggregation, time reservation strategy and power saving multi-user polling (PSMP) and so on. Some aggregation algorithms such as A-MSDU, A-MPDU, Two-level MPDU aggregation are modeled and verificated based on NS2 network simulator. Simulation results show that MAC frame aggregation improves the system throughput greatly.