Design Of OFDM Baseband Transmitting And Processing System Based On802.11a And Realization On FPGA

Wireless local area network, the “last100meter” wireless access solutions, use radiowaves to transmit, whose appearance has made up the inadequacy of the cable networks.Compared to cable networks, it has the features of being easily installed, strong scalability,and flexible mobility. IEEE802.11a is one kind of criterions of wireless local area networks,which has prescribed the protocol specification of wireless local area networks and is able toprovide data rates up to54Mbps.OFDM, a way of multi-carrier modulations, which can effectively combating againstcompressing delay spread, has already become a hot technology in the communication fieldin recent years. Its principle is that it can transfer the serial high speed data streams intoparallel low speed ones, and these streams are modulated to orthogonal sub-carriers to betransmitted, thus saving valuable frequency spectrum resources. In the meantime, becausesignal frequency bandwidth of each sub-channels is less than the channel’s correlationbandwidth, OFDM symbol has excellent combating against frequency-selective fadingability.The WLAN standard IEEE802.11a use OFDM tech as the physical layer access. Inaccordance with IEEE802.11a protocol，the paper has proposed hardware implementationscheme based on Xilinx FPGA for OFDM baseband transmitting system, that is, dividing itinto a number of the secondary units at system level by the up-to-down module partitionmethod, and then dividing each secondary units into the next level systerms till you are ableto use functionally independent module or IP core to achieve it directly. But the problem is,hierarchy of a system may be relatively large, so it needs FPGA development tools tocomb the levels effectively. Fortunately, popular development tools are provided for thisfunction, which make FPGA development gett more and more convenient, shorten thedevelopment cycle, and enhance the development efficiency greatly. The paper has carefullyanalyzed and implemented each part of unit frame of physical layer protocol data, such asshort training sequence, long training sequence, signal field and data field, and finallyconstructed OFDM baseband transmitting and processing system and implemented the entiresystem on FPGA development platform.