Study Of OFDM System Based On IEEE802.11a

New generation wireless communication networks will be new networks which are based on IPV6 Packet Switching, providing peak transmission rate over 100Mbits/s and supporting seamless roaming among all kinds of wireless networks. Orthogonal Frequency Division Multiplexing (OFDM) system is becoming a very hot research topic recently because of high bandwidth efficiency, easy hardware implementation and robustness against frequency selective fading channel and narrow-band interference, and therefore is widely regarded as the key underlying air interface technology for future wireless systems such as WiMAX, 3GPP Long Term Evolution (LTE) and 3GPP2 Ultra Mobile Broadband (UMB).Since the standard formulation of IEEE802.11 in 1997,IEEE802.11 has been the mainstream standard of WLAN(Wireless Local Area Network).OFDM is adopted by both IEEE802.11a and IEEE802.11g in physical layer standard ,which were put forward successively and provide data transmission rate to 54Mbps.New generation wireless communication technology, such as MIMO, Software Radio and Smart Antenna Technology and so on, will be taken into next generation High-rate Wireless LAN , in order to provide higher transmission rate and farer transmission distance.In this dissertation, the basic principle and system structure of OFDM and the physical layer standard of IEEE802.11a are introduced, and also how to design OFDM transmitter according to the physical layer standard of IEEE802.11a and the working principle and implementation method of main modules in the transmitter are discussed in detail. During the design of receiver, the cause of synchronous error and the effect of synchronous error on OFDM system are simply analyzed first of all, proper synchronization scheme is designed in view of the characteristics of burst communication adopted by WLAN based on IEEE802.11a. According to the characteristics of the preamble structure of the transmit signal and the guides in the standard, frame synchronization, frequency synchronization and symbol synchroni-zation are implemented in time domain with the training sequence, while carrier phase tracking and channel estimation and equalization are implemented in frequency domain with the training sequence and pilots. This synchronization scheme has simple structure, less calculation amount and meets the synchronization requirements of burst communication well. The float point simulation of baseband OFDM System based on IEEE802.11a and simulation of 30M IF digital OFDM System based on IEEE802.11a are finished with MATLAB; sideband suppression, pilots characteristics and CCDF(Power Complementary Cumulative Distribution Function) of signal are discussed based on the finished communication platform; combined with fix point simulation, the hardware implementation of 30M IF digital OFDM transmitter on FPGA is completed with EP2S180 which belongs to StratixII and is produced by Altera company and Verilog language,and corresponding testing is finished at last.