The work presented in this dissertation examines the performance of two satellite radio communication systems by computer simulation. Two simulations were separately performed for a spread spectrum chirp system as an analog communications system, and for the Land Mobile Satellite System (LMSS) channel as a digital communications system. For the simulation of analog communications, a spread spectrum system using chirp techniques called ‘Coded Multiple Chirp Spread Spectrum’ was proposed as a simple, cost-effective alternative for conventional spread spectrum systems. Its application as a spread spectrum overlay service on analog FM-TV was examined through the mutual interference analysis and spectral analysis using software programming. For the simulation of digital communications, various digital modulation schemes as well as channel encoding, block interleaving/deinterleaving, and differential encoding techniques were used for a thorough performance evaluation of a Land Mobile Satellite System under fading conditions. For this purpose, an LMSS fading channel simulator capable of simulating diverse fading characteristics for a satellite channel was designed and tested to yield various performance measures such as symbol error rate and average bit error rate. / Ph. D.