Adaptive modulation for OFDM system with varying speed receiver

Adaptive modulation exploits the channel conditions to improve spectral efficiency of the wireless communication system. Moreover, channel characteristics also depend upon Doppler shift, due to the motion of the mobile station. In this paper, a new technique of adaptive modulation is proposed which takes into account the effect of varying speed receiver. For the purpose, mapping between channel correlation and instantaneous signal-to-noise ratio is obtained based on varying speed receiver and is used to select the best suitable modulation scheme. The system performance is obtained over frequency-selective fading channel and Kalman-filter based method is used to predict the frequency domain channel coefficients. The numerical results shows the improved performance of the proposed adaptive scheme to keep required bit error rate with varying speed receiver compared to the adaptive schemes with static receiver.