ABSTRACT

This thesis presents the spectral efficiency of modulation and coding schemes in order to access their frequency maximization capacity using orthogonal frequency division multiplexing (OFDM). The performance of bit-error-rate and signal-to-noise ratio was obtained using Matlab/Simulink. Models were developed namely OFDM model with phase keying method, OFDM model with space-time block code (STBC) and OFDM model without space-time block code. Different digital modulation and coding techniques were used in the developed models and the models were simulated in the Matlab environment. The results of the simulation showed that the highest value for BER with STBC was 8x10^-5 and highest value for BER without STBC was 9x10^-5. The highest value for SNR with STBC and the highest value for SNR without STBC were 21.78 dB and 10.84 dB while the lowest value for SNR with STBC and the lowest value for SNR without STBC were 22.23dB and 0 dB respectively. Again, when SNR was 5 dB, the BER (X10^-4) for Binary Phase Shift Keying, Quadrature Phase Shift Keying, 8-Quadrature Amplitude Modulation, 16- Quadrature Amplitude Modulation and 64- Quadrature Amplitude Modulation was 40, 20, 4, 10 and 30 and when SNR was 10 dB, the BER(X10^-4) was 4, 2, 0.4, 1 and 3. However, it was observed that OFDM model with STBC produces better performance than OFDM model without STBC. This indicated that the bit-error-rate decreases with an increase in signal-to-noise ratio and also improve the quality of service of the crowded spectrum. The results obtained from the literature shows that MIMO-OFDM system with STBC has better signal to noise ratio with less BER than the non STBC MIMO-OFDM system but was purely based on analysis without a Simulink model. The introduction of Space Time Block Code (STBC) Simulink has proven to be better technique in reducing bit error rate and thereby improving weak signals compared to results of other researchers.