The impact of gateway distribution on the system capacity of CDMA mobile satellite systems

Recent research indicates that satellite diversity is a practical means of mitigating the effects of satellite fading for Mobile Satellite Systems (MSS) employing CDMA. However, the underlying assumption of such research is that satellite diversity is available all the time, which is not true in reality. We will investigate the impact of improper gateway distribution on the system capacity of MSS. We investigate the principle of distributing the gateways to ensure single and. double satellite service and present some strategies of searching for the optimal gateway distribution for single and double satellite service. To analyze the impact of gateway distributions on the system capacity of MSS, we classify the general mobile terminal environments into five states. By computing the required power margin of each state to reach the same average Bit-Error Rate (BER) and taking the occurrence probability of each state into account, the capacity of a Mobile Satellite System, expressed as the average number of mobile terminals per satellite over the area ranging from South 80° to North 80°, is analytically derived and thoroughly validated by means of computer simulations. After comparing the system capacity of a MSS with improper gateway distributions to that with the optimal gateway distribution, we show that the capacity of a MSS is decreased considerably due to improper gateway distributions. Moreover, the quantitative results indicate that a MSS in a propagation environment of light shadowing suffers more capacity loss due to improper gateway distribution than a MSS in an environment of heavy shadowing.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat