802.11g A Physical Layer Ofdm Demodulation System, The Fpga Implementation

In recent years, there has been a great interest in researching and applying OFDM technology into high-speed wireless communications. OFDM based digital communication systems are robust in multipath environment. Moreover, OFDM can achieve high bandwidth efficiency and can be implemented with a simple structure. These advantages make OFDM technology particular suitable for high-rate data transmission in wireless environments.Following the description of the mathematic principle of OFDM and necessary elements for set up an OFDM system, this thesis discusses some non-ideal effects on the performance of OFDM digital communications,and put forward a synchronization scheme according to IEEE802.11a, suitable for using in the WLAN burst mode communications system. In the Acquire Phase, it utilizes the training symbols to achieve packet header detection, frequency offset estimation and symbol timing. During the Tracking Phase, it makes use of the pilot signal to fulfill the tasks of carrier phase correction, carrier frequency tracking and sampling clock tracking. This scheme has such advantages as simple computation and easy to realize. It satisfies the demand for rapid synchronization in the bust mode communications environment. The computer simulation results testify the scheme's good performance in slow time-variant channel.