Abstract
The deployment of the Next Generation Wireless Network (NGWN) involves different service providers, different radio access technologies and multi-mode mobile terminals that have to be compatible with existing services and technologies. It has provided many challenges for researchers and service providers. In particular, it is a difficult task to provide desired services, such as video streaming, teleconferencing, and data download/upload, with an acceptable Quality of Service (QoS) anywhere and anytime to the mobile users. These diverse needs of NGWN demand efficient and reliable technologies to satisfy users as well as network providers. Also NGWNs are expected to provide a high data rate and optimized QoS to multimedia and real-time applications over the Internet Protocol (IP) net-works. However, due to the movement of the mobile terminals, seamless connectivity needs to be maintained when a mobile terminal moves across different cells or networks. Handover, which is the process of transferring an ongoing call from one base station to another, plays a critical role in achieving the above goals.
This thesis focuses on providing an end-to-end QoS to the users during the handover process in NGWNs. First, the thesis evaluates the performance of two kinds of popular wireless networks operating according to the WiMAX and UMTS standards, in terms of supporting Voice over Internet Protocol (VoIP) traffic. It then proposes a novel handover scheme compliant with the IEEE 802.21 standard (i.e. the Media Independent Handover protocol) which enables handover in an integrated network with UMTS and WiMAX. It takes into account the quality of a call and the load of the call among all the available access points while transferring the call between cells and net-works. Mean Opinion Score (MOS) is used as the major metric of the call quality in handover optimization. Comparing the novel MOS- based handover scheme with the traditional handover scheme based on Radio Signal Strength (RSS) through simulation of an integrated network of WiMAX and UMTS, the simulation results demonstrate that the proposed MOS-based scheme can maintain high call quality and reduce the probabilities of handover dropping and call dropping. Finally, the thesis proposes an energy efficient handover scheme that does not require frequent scanning of the network during handover process. Two schemes, heuristic and optimal, are proposed to select the optimal base station during handover. The simulation results show the handover scheme can significantly reduce energy consumption of mobile terminals.