Level Sensitivity of Adaptive Modulation in Fast Fading Channels

In this paper it first illustrate that the real bit error rate (BER) of adaptive modulation in fading channels may away from the design BER due to the sensitivity of switching levels. A moving average method is presented to resolve this issue in the slow fading channels. For fast fading channels, a method by offsetting the switching levels is presented. Simulation results show that constant BER as well as high throughout can be achieved if the presented methods are applied to the adaptive quadrature amplitude modulation with orthogonal frequency division multiplexing (AQAM-OFDM) system in multi-path fading channels.