(A) study on handover prioritization scheme for low earth orbit mobile satellite systems

Abstract

In this thesis, we consider LEO mobile satellite systems (LEO-MSS``s) and propose a handover prioritization scheme that is suitable for LEO-MSS``s. Dynamic channel assignment (DCA) schemes are more proper in LEO-MSS``s, and lots of handover attempts are expected to be generated, because of the satellite motion and extreme non-uniform traffic distribution along the orbit. For the mobile subscriber``s point of view, forced call termination is more undesirable than new call blocking. Hence, handover attempts should have higher priority than new call attempts. Therefore, we need a handover prioritization scheme that can be applied to DCA schemes. A proper handover prioritization scheme should decrease the handover failure rate as the results of increasing the new call blocking probability. Although several handover prioritization schemes have been introduced for fixed channel assignment schemes, none has been proposed for DCA. The main objective of this thesis is to design a handover prioritization scheme that is suitable for DCA and can be used in LEO-MSS``s. We propose an extra-channel assignment scheme (ECAS) as a revised version of guard channel scheme for DCA. ECAS is suitable for DCA scheme and gives handover priority according to system manager``s preference. Our computer simulations show that the weighted penalty of lost calls of ECAS is significantly less than that of DCA scheme.