Tuesday, 20 March 2012

Digital Communication


This project was done by two students -me and a friend- for Digital Communication course in a graduate level at Concordia university.

Figure showing an antenna and a receiving device.

Abstract:
Digital communication aims essentially to optimize the transmission of digital data to be received as it was sent keeping the probability of errors that may occur low. Many transmitting schemes have been introduced aiming to insure getting highly reliable communication systems and to keep the bit error rate as low as possible since it is a major factor in evaluating digital communication systems. The goal in this project was to implement different techniques and simulate them using Matlab and compare their performance from theoretical and simulation points of view.

The first method of optimizing data transmission considered was baseband uncoded BPSK and QPSK communication systems without pulse shaping filter and matched filter. The channel used is an Additive White Gaussian Noise (AWGN) channel. Theoretical and simulation results are done using Matlab, the bit error rate (BER) versus Eb/No of the system is sketched in both cases and the results are compared.
Second, Finite impulse response filter ( Square Root Raised Cosine Filter) is added to the QPSK as pulse shaping and matched filters. They are added to minimize the effect of AWGN on the transmitted signal by convolving it with the impulse response of the filter. In other words, Signal to Noise Ratio (SNR) goes up and the data will be easier to detect at the decision block without error which consequently improve the overall system performance.

Third, we design a code system considering Hamming (7, 4)  as channel coding of the system and add it to the QPSK scheme, and we plot two graphs showing the BER versus Eb/N0 using Matlab for simulation and theoretical results, then we compared them. 

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