Flow Control in a Hybrid Satellite-Terrestrial Network: Analysis and Algorithm Design

The Internet is making its way into our day-to-day life. Start-up companies and industry leaders in communication networks are competing in the market place for offering new and high performance solutions to their increasing number of customers. Individuals that, due to their job characteristics have access to the Internet via their workplace desktop have quite a different experience with the cyberspace versus those that are accessing networking services from their homes. Typically, a common Internet ``surfer'' that connects from home, will be frustrated by the speed at which his/her service is working. This is due to the limits imposed by the classical dial-up connection, via an Internet Service Provider. To-date, various alternatives to this situation have been reported: access via cable television networks and access via satellite links, not to mention ISDN line solutions. The first alternative is more likely to be implemented in crowded areas where the cable infrastructure may be already in place. However there are studies that show that a large investment is necessary to cover vast areas with this kind of infrastructure. Major costs are primarily due to the effort of laying out cable. Satellite Internet on the other hand is not restricted to work in a given area. Satellites ``see'' virtually everywhere. However there are trade-offs concerning the available bandwidth and its allocation. Also, satellite Internet is primarily dedicated to persons that receive more data than they generate for output. In this thesis we pursue a study of the flow-control in a satellite-terrestrial network. An analysis study is first performed for the DirecPC Hybrid Internet service. Then different bandwidth allocation strategies are compared, with the performance criterion being the delay in interactive sessions. The best service obviously minimizes the delay. We present theoretical and analytical background on the interactive traffic modeling problem. Fractal-type traffic is fed into the network models and different performance metrics are measured and discussed. We end by concluding that in the event that a satellite-terrestrial network would exclusively be used for interactive users, the optimal policy is to first serve the connection that suffers the largest instantaneous delay.