OPTIMIZATION OF DIGITAL SATELLITE COMMUNICATION NETWORKS.

摘要

The rapid growth in transmission of digital information and the advantages offered by incorporating satellites as the means of communications emphasize the need for cost effective networks. In planning a digital satellite communication network, the designer is faced with many system parameters such as statistical parameters of digital traffic, transmission performance requirements or ground station hardware configuration. To design a network which provides the required performance at a minimum cost, a system approach is necessary. This dissertation presents a method which can be used to design the "optimal" digital satellite communication system or to analyze an existing satellite network.; In this study a simplified model includes ground, space, and channel segments. In the ground segment, analog hardware is studied and optimized as a subsystem. In the space segment, a basis for the satellite transponder cost is obtained. The channel architecture, which links the space and ground segments, consists of two dimensions: channelization techniques and channel derivation schemes.; In channelization techniques, Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and combined Frequency and Time Division Multiple Access (combined FDMA-TDMA) are studied. The channel allocation schemes consist of preassigned, random access and reservation techniques. Several multiple access techniques are studied and their performance is evaluated by applying queueing theory. Both circuit switching and packet switching are considered wherever appropriate.; As another subsystem optimization study, modulation coding schemes are examined for power-limited and/or band-limited channels. To illustrate the application of the model, an example of future digital satellite networks--namely, databank--is considered. The results for this case study clearly demonstrate the impact of the combined FDMA-TDMA technique and the effectiveness of the channel allocation schemes for different digital traffic characteristics. The study also reflects the cost efficiency of the small size antenna (4.5 meters) for the earth station.