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This paper presents simulation results for the transmission of unicast MAC frames over 802.11a/g. Fading channel models at various Doppler spreads are developed to generate time-correlated SNR waveforms. These are used in a bit accurate MAC/PHY simulator to estimate frame loss rate, transmission delay, jitter and throughput for a steady flow of transmit frames. Time-correlated channels are required to correctly simulate the bursty nature of packet loss in a wireless channel. The Doppler spread is shown to have a strong effect on the performance of 802.11 ARQ at the MAC layer. Compared to the slow fading case, in a fast fading channel fewer MAC layer retransmissions are required and the end-to-end delay is significantly reduced. Under poor channel conditions the simulated delay and frame loss rate are seriously underestimated if time-uncorrelated fading is assumed.