Simulation of adaptive coded modulation for OFDM communication Systems.

Arkan Waleed Ubdul-Malik
Dr. Ra'ad S. Fyath

Abstract: In this thesis, an adaptive modulation and coding (AMC) scheme is applied to OFDM wireless communication systems. This scheme offers an alternative wireless link adaptation approach that promises to raise the overall system capacity. The AMC provides the flexibility to match the modulationcoding scheme to the average channel conditions. With AMC, the power of the transmitted signal is held constant over a frame interval while both the modulation and coding formats are changed to match the received signal quality. The performance of OFDM wireless communication systems operating under fixed-power adaptive turbo coded modulation scheme is simulated in detail. The results indicate clearly that for a target bit-error-rate (BER) of 10-2, the turbo coded modulation offers a signal-to-noise (SNR) gains of 3.2dB, 2.1dB, 1.1dB for a BPSK, 16-QAM and 64-QAM operating with code rates of 1/2, 1/3, 2/3, respectively compared to uncoded states. Simulation results show that the proposed adaptive OFDM scheme exhibits an SNR gain of more than 6.6, 7.8 and 8.6 dB relative to nonadaptive turbo coded modulation at target BER=10-2, 10-3 and 10-4, respectively. A software package is developed using MATLAB 7.2 (R2006a) environment to assess system performance under different modulation and turbo code parameters.