FPGA based implementation of IEEE 80211a physical layer

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier transmission technique, in which a single bitstream is transmitted over a large number of closely-spaced orthogonal subcarriers. It has been adopted for several technologies, such as Wireless Local Area Networks (WLAN), Digital Audio and Terrestrial Television Broadcasting and Worldwide Interoperability for Microwave Access (WiMAX) systems. In this work, IEEE802.11a WLAN standard was implemented on Field Programmable Gate Array (FPGA) for being familiar with the implementation problems of OFDM systems. The algorithms that are used in the implementation were firstly built up in MATLAB environment and the performance of system was observed with a simulator developed for this purpose. The transmitter and receiver FPGA implementations, which support the transmission rates from 6 to 54 Mbps, were designed in Xilinx System Generator Toolbox for MATLAB Simulink environment. The modulation technique and the Forward Error Coding (FEC) rate used at the transmitter are automatically adjusted by the desired bitrate as BPSK, QPSK, 16QAM or 64QAM and 1/2, 2/3 or 3/4, respectively.The transceiver utilizes 5986 slices, 45 block RAMs and 73 multipliers of a Xilinx Virtex-4 sx35 chip corresponding to % 39 of the resources. In addition, the FPGA implementation of the transceiver was also tested by constructing a wireless link between two Lyrtech Software Defined Radio Development Kits and the bit error rate of the designed system was measured by performing a digital loop-back test under an Additive White Gaussian Noise (AWGN) channel.