FHSS DSSS And Hybrid DSFH Performance Evaluation For VSAT

Abstract The performance of any radio communication system is affected by several factors such as interference and jamming caused by some other parallel networks for the purpose of decreasing the performance of a given system. Direct Sequence Spread Spectrum DSSS Frequency Hopping Spread Spectrum FHSS and a hybrid approach of both techniques DSFH are proposed to solve the problem. Whereas DSSS generates a sequence of bit and sends them over a fixed data rate and spread the spectrum with a spreading sequence FHSS send the data into different channels with variable data rates and the hybrid DSFH approach takes advantage of DSSS and uses it in multiple channels. Various modulation techniques which are suitable for Very small aperture terminal VSAT were simulated with each of the mentioned approaches such as Phase Ship Keying PSK Frequency Shift Keying FSK and Quadrature Amplitude Modulation QAM to in order to work properly with each technique. The performance of each approach was evaluated in terms of Signal to Noise Ratio vs Bit Error Rate throughput delay and datarate. The results are very close to each other in terms of BER but the best approach was the DSSS. The Hybrid DSFH needs more power to operate so it best fits the applications with high frequencies. The Hybrid DSFH approach was the best of the three tested approaches in terms of throughput delay and datarate. The FHSS technique was average in all the parameters and had greater delay time due to the delay gap in the hopping process.