Authors
Abstract
This paper presents design and implementation of adaptive
modulation 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 of
using adaptive modulation in terms of probability of bit error and spectral
efficiency. It specifically examines the performance enhancement made
possible by using linear prediction along with channel estimation in
conjunction with adaptive modulation. Simulation results proved that the
adaptive system performance with estimator and predictor is better than
other modulation alone. The simulation results for adaptive modulation in
compared 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 system
improvement takes place by decreasing S/N by 1.3dB- 4dB. Recarding
BER=10-5 with same Doppler frequency, the improvement is by decreasing
S/N by 1.5dB-5 dB. Simulation results also show the flexibility of the
adaptive system to operate with different level of modulation based on
switching of S/N. Matlab7.8(R2009a) used for simulation of adaptive
modulation system with AWGN and fading channel.
Keywords
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