Design Methodologies Comparison of an OFDM System and Implementation Issues Using FPGA Technology for Vehicular Communications
Orthogonal frequency division multiplexing (OFDM) is a promising technique that has established a significant presence in the wireless technology market. The combination of high data transfer rates, high performance, and multipath attenuation strength, render OFDM ideal for current and future communication applications, allowing response to high service-quality requirements. The system presented in this chapter is prototyped based on the IEEE 802.11p standard, customized for vehicular ad hoc networks, and the signals are transmitted and received using a bandwidth of 10 MHz. The OFDM transceiver implementation is based on FPGA technology and the very-high-speed integrated circuit hardware description language (VHDL). Two different design techniques using the Xilinx System Generator tool and handwritten code in VHDL were applied in order to achieve optimum results. The hardware modules designed include a QPSK modulator-demodulator, serial-to-parallel converter, FFT, and IFFT. The use of reconfigurable FPGA devices and VHDL descriptions allowed a large number of tests to be carried out for each module. The final implementation consists of two identical Xilinx Virtex-4 FPGA development boards (one for the receiver and one for the transmitter), offering dual channel high-performance ADCs and DACs, for operation in the baseband area.