Performance analysis of OFDM in frequency selective time-variant channels with application to IEEE 802.16 broadband wireless access

In this paper, the performance of Orthogonal Frequency Division Multiplexing systems in frequency selective and time-variant Rayleigh fading channels is analyzed. Channel variations severely degrade the performance of OFDM by introducing both a complicated multiplicative distortion and an additive Intercarrier Interference.. The IEEE 802.16 standard is designed to provide broadband wireless services for fixed and pedestrian terminals, and hence, the channel is assumed to be slowly variant during one OFDM symbol. Under this assumption, the multiplicative distortion can be simplified as a sum of two correlated Rayleigh random variables. Based on this simplification, and by observing that the signal-to-interference-plus-noise ratio of the OFDM system is similar to the expression of the signal-to-noise ratio at the output of an Equal Gain Combiner, eve derive a closed form analytical expression for the symbol error rate. The proposed analytical expression is verified through numerical evaluation using the parameters of the IEEE 802.16 standard.