The Synchronization Algorithm Research Of OFDM System

Synchronozation technology is one of the key technologies of OFDM system, which has become the hot spot in recent years. OFDM is more sensitive to the synchronization errors, because of its carriers demand on completely orthogonal between sub carriers. However, owing to the differences of oscillators' frequency at transmitter and receiver, and Doppler frequency offset existing in channels, both of those will affect sub carriers' orthogonal relation and bring into ICI (Inter Carrier Interface). At the same time, if the symbol timing estimation is not correct, it will bring into ISI (Inter Symbol Interface), which also will decrease the demodulate performance of the system.This dissertation gives an over view on the development of OFDM technology. It is summarized the effects of synchronization errors. Then it gives introduction of some classical synchronization algorithm, such as the ML algorithm which is base on the cyclic prefix and the T.M.Schmidl's algorithm which is based on training sequence and so on. At the end of this paper, it makes basic researches on symbol synchronization and frequency synchronization schemes of IEEE802.11a WLAN system. This article analyzes the reason that results in the platform in Schmidl timing algorithm, and proposed an improved algorithm based on the same training sequence without adding extra complexity and has a better timing performance. The performance of timing synchronization gets rid of platform, and becomes sharp at the right synchronize time. The system emulation of IEEE802.11a WLAN standard results show that compard with Scmidl algorithom, the proved synchronization algorithom decrease the system bit err rate more.