Intercarrier and intersymbol interference analysis of OFDM systems on time-invariant channels

In order to derive the mathematical description of interference and useful power in the case of insufficient guard length of an OFDM system, the channel impulse response is truncated into two parts, the so-called two truncated channels, in mathematical analysis. The first one describes the behaviour inside the guard interval, the other outside. Assuming the channel to be wide-sense stationary with uncorrelated scattering (WSSUS), the linear characteristic of Fourier transformation allows to be obtained exactly the mathematical expressions of intercarrier interference (ICI) power, P_ICI, intersymbol interference (ISI) power, P_ISI, and useful power, P_U, in dependence of the correlation functions and the multipath channel profiles of the two truncated channels. We consider only the case of the time-invariant channel. The simulation results show a good agreement with the theoretical results.