Abstract
In this thesis, we propose an energy-efficient transport layer handoff mechanism for VoIP (Voice over Internet Protocol) service in heterogeneous network environment using SCTP (Stream Control Transmission Protocol). The proposed handoff mechanism is used to improve the transmission quality of VoIP service and reduce the power consumption of mobile hosts. The multi-homing feature of SCTP allows two SCTP endpoints to maintain an association with multiple transmission paths accessed by different types of wireless access networks. The proposed handoff mechanism implements a new path selection mechanism to select the best path from all available paths based on the VoIP quality and power consumption of each path and use SCTP multi-homing feature to handover to that selected path. VoIP quality is measured by the MOS (Mean Opinion Score) calculated from the ITU-T (International Telecommunication Union Technical standards) E-model. SCTP is a newly standardized transport layer protocol, and not widely used as TCP or UDP. In order to increase the generality of our proposed handoff mechanism, we design and implement a new transparent transformation mechanism between SCTP and TCP.