Abstract

Satellite communications systems are ideally equipped to provide future multimedia services on a global level and at a distance-independent cost. In order to meet the ever-growing bandwidth demands of these new applications, satellites employing multiple spot beam antennas are required. An on-board packet switch is an essential element in such a system as it offers full connectivity among users and offers efficient utilization of the space segment. This thesis evaluates the performance of a satellite-switched system in a multimedia environment mainly composed of voice, video, and data sources. Aggregate voice or video traffic is modeled as a 2-state Markov Modulated Poisson Process (MMPP) while two models for aggregate data traffic, MMPP and Pareto Modulated Poisson Process (PMPP) are used to examine the effects of traffic burstiness and long-range dependent behaviour. Multiple Frequency Time Division Multiple Access (MF-TDMA) is utilized on the uplink in conjunction with a dynamic capacity allocation scheme. Higher priority is given to voice and video real-time traffic to avoid delay variation. On-board downlink queue is provided for data jitter-tolerant traffic to achieve high statistical multiplexing gain. Simulation results show that the system can support traffic predominantly composed of real-time applications. As jitter-tolerant data becomes the dominant traffic component and becomes highly correlated, the size of the uplink and downlink queues need to be increased to maintain an acceptable quality-of-service (QoS). The packet loss due to the Knockout contention scheme is much lower than that due to the limited capacity on the uplink and downlink. This makes the Knockout switch fabric attractive for on-board switching since it achieves low complexity. The need for a congestion control scheme that can shape the traffic is required, especially when the traffic has long-range dependent behaviour.