Noise immunity characteristics of cooperative analog relay in a Vanet network

Today the capabilities of intelligent transport systems are largely determined by the characteristics of the hybrid wireless vehicular ad hoc networks (VANET). These networks use orthogonal frequency-division multiplexing (OFDM) technique for direct communications between vehicles as well as communications between vehicles and stationary infrastructure devices. Connections can be direct or they can be relayed by means of cooperative diversity when it is needed to improve noise immunity. One of the specifics of the vehicular ad hoc networks is the presence of high-speed vehicles, for which the Doppler spread results in the lost orthogonality of the OFDM signal and interchannel interference which decreases the noise immunity. The article considers the impact of the interchannel interference on the noise immunity of OFDM system using analog relay based cooperative diversity with two vehicles. Fading is modelled individually for each of the OFDM signal subcarriers using baseband equivalents and Rayleigh statistics. Doppler spread model corresponds to isotropic scattering. Keywords: cooperative diversity, AF relay, Rayleigh fading, spectral Doppler spreading, SEP