Design and implementation of an OFDM system for vehicular communications with FPGA technologies

Abstract

This paper presents design and implementation results of an Orthogonal Frequency Division Multiplexing (OFDM) system customized for vehicular ad-hoc networks, based on the IEEE 802.11p standard specifications. The 802.11p is based on the widely spread IEEE 802.11a and intends to support both public safety and licensed private operations over communication channels. OFDM achieves very efficient use of the allocated bandwidth and the main advantage is its robustness to frequency selectivity in wireless environment, like in the case of vehicular communications. The OFDM transceiver implementation presented in this paper is based on FPGA technology and the VHDL hardware description language. The hardware modules designed include QPSK modulator-demodulator, serial to parallel converter, FFT, IFFT. The use of reconfigurable FPGA devices and VHDL descriptions allowed a large number of tests to be carried out for each module, in order to obtain optimum results. The final implementation consists of two identical Xilinx Virtex-4 FPGA development boards (one for the receiver and one for the transmitter), offering among others dual channel high performance ADCs and DACs, required for operation in the licensed ITS band of 5.9 GHz.