Comparative Analysis of Mobility Management Schemes in a Low Earth Orbit Satellite Network

摘要

In the 60's the United Status and the Union of Soviet Socialist Republics engaged in a 'space race' to be the first to put a man on the moon. Today, the space race is between large multinational telecommunication corporations with the winner receiving the financial rewards by providing communication services to the billions without even a simple telephone. Many entrants are using Low Earth Orbit (LEO) satellites to provide the communications infrastructure, but the number of customers a satellite can support is limited by bandwidth available. This resource must be used efficiently, and this involves reducing the management overhead. This thesis investigates one aspect of management overhead, the bandwidth cost associated with mobility management. This thesis provides a performance analysis of three different mobility management topologies and their associated protocols when used in a LEO satellite constellation. Simulations were developed to compare two aspects of mobility management protocols. The first aspect was to determine which is the better location for the Visitor Location Register (VLR) and Authentication Center, collocated with the Home Location Register in the terrestrial gateways or placed on the communications satellites. The second aspect compared three methods of updating the VLR, if the VLR is onboard the satellite. Three different update schemes were examined: using the standard IS- 4l-C protocol, transferring the database from one satellite to another, or discarding the database and rebuilding it from scratch. The thesis results concluded that simply moving the VLR from the gateway to the satellite did not decrease the traffic overhead associated with mobility management. In fact, the amount of traffic increased about 33 percent. Moving the AC and VLR together to the satellite however decreased the traffic load by average of 10 percent over the standard model.