Modeling OFDM irreducible BER with impact of CP length and CFO in multipath channel with small delay dispersion
In this paper, we propose an analytical model for estimating the irreducible bit error ratio BER in multipath channel with small-extent delay dispersion, such as indoor, where the signal-to-noise ratio is high, implying dominance of inter-symbol interference as error-generating mechanism. Both channel and overall orthogonal frequency-division multiplexing OFDM symbols are modeled stochastically, resulting with novel expression for the residual BER prediction that is shown to analytically distinguish power delay profiles with equal delay spreads but having different profile shapes. In addition, the model could simply accommodate insertion of cyclic prefix onto the OFDM symbol, providing a means for either testing adequacy of any applied standard cyclic prefix length or finding its optimal value as a compromise between the performance enhancement achieved by inserting cyclic prefix and the consequently added redundancy. Finally, the model was modified as to include the analysis of effects of subcarrier frequency inaccuracy or Doppler shift, by adding additional equivalent delay dispersion with equal effect on BER degradation, while considering the system virtually free of carrier frequency offset. All analytically achieved results and conclusions are tested and successfully verified by conducted extensive Monte Carlo simulations. Copyright © 2015John Wiley & Sons, Ltd.