Performance evaluation of adaptive OFDM systems in time-varying channels

One of advantages of the OFDM transmission technique is that it has the inherent flexibility to adapt the modulation scheme on each subcarrier according to the signal-to-noise ratio (SNR) on the subcarrier, leading to an adaptive OFDM (AOFDM) system. We proposed a coded AOFDM system in a time-varying channel. By choosing an optimal M-QAM modulation scheme used by a subcarrier on the instantaneous channel knowledge, we extensively investigate the bit-error-rate (BER) performances of AOFDM systems with different vehicle speeds, modulation schemes and bit rates under Rayleigh fading channels.