Design and Implementation of Adaptive Modulation Modem Based on Software Defined Radio(SDR) for WiMAX System


This paper presents design and implementation of adaptivemodulation modem for WiMAX system. (BPSK, QPSK, 8QAM, 16QAM,32QAM and 64QAM) are used in this work. Software Defined Radio(SDR)is used for implementing this modem. This work examines the benefits ofusing adaptive modulation in terms of probability of bit error and spectralefficiency. It specifically examines the performance enhancement madepossible by using linear prediction along with channel estimation inconjunction with adaptive modulation. Simulation results proved that theadaptive system performance with estimator and predictor is better thanother modulation alone. The simulation results for adaptive modulation incompared to each modulation technique alone show that for BER=10-3 with(fd=50Hz -200Hz)system the improvement occurs by decreasing S/N by 2-3dB. As for BER=10-4 with same Doppler frequency, the systemimprovement takes place by decreasing S/N by 1.3dB- 4dB. RecardingBER=10-5 with same Doppler frequency, the improvement is by decreasingS/N by 1.5dB-5 dB. Simulation results also show the flexibility of theadaptive system to operate with different level of modulation based onswitching of S/N. Matlab7.8(R2009a) used for simulation of adaptivemodulation system with AWGN and fading channel.