Impacts of Channel Impairments and Imperfections on OFDM System Performances

An important indicator commonly used to evaluate the quality of a communication link is Signal-to-Interference ratio (SIR). However, there are relatively few papers which deal with SIR of OFDM systems in the literature. This paper analytically investigates OFDM system performance by including major channel impediments such as excess delay spread over cyclic prefix, frequency offset, and time varying fading. We derive a closed-form expression for SIR accounting for details of the interferences. Variations of ICI and ISI with the number of subcarriers, Doppler spread are also investigated. A condition relating peak ISI and peak ICI is derived. We also analyze the leakage of power (unwanted power distributions across subcarriers) for desired subcarrier demodulation.