Performance of OFDM Systems with Residual Carrier Frequency Offset over Time-varying Rayleigh Channels

In this paper, the performance of orthogonal frequency division multiplexing (OFDM) systems with residual carrier frequency offset over time-varying Rayleigh channels is investigated. The power of different received signal components (the desired signal, the ICI signals caused by frequency offset and channel variations, and noise signals) are firstly calculated and analyzed, and the SINR (Signal to Interference plus Noise ratio) and BER (Bit Error Rates) calculations for 16-QAM OFDM systems are then investigated. Analytical analysis and computer simulations show the following important results: (1) residual frequency offset and channels´ time variations greatly degraded the performance of OFDM systems; (2) the intercarrier interference (ICI) energy caused by channel variations or frequency offset is concentrated in cyclically adjacent subcarriers, which is important for developing low complexity ICI cancellation techniques; (3) the influence of residual carrier frequency offset on OFDM system performance can be modeled as the effects of equivalent channels´ time variations, and a time-varying channel model including the residual carrier frequency offset effect is proposed.