Improving initiation, decision and execution phases for vertical handover in heterogeneous wireless mobile networks
One of the challenging issues in Next Generation Wireless Systems (NGWS) is seamless \ud Vertical Handover (VHO) during the mobility between different types of technologies \ud (3GPP and non-3GPP) such as Global System for Mobile Communication (GSM), \ud Wireless Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (WiMAX), \ud Universal Mobile Telecommunications System (UMTS) and Long Term Evolution \ud (LTE). Therefore, the telecommunication operators are required to develop an\ud interoperability strategy for these different types of existing networks to get the best \ud connection anywhere, anytime without interruption of the ongoing sessions. In order to \ud identify this problem accurately, the research study presented in this thesis provides four \ud surveys about VHO approaches found in the literature. In these surveys, we classify the \ud existing VHO approaches into categories based on the available VHO techniques for \ud which we present their objectives and performances issues. After that, we propose an \ud optimised VHO approach based on the VHO approaches that have been studied in the \ud literature and take into consideration the research problems and conclusions which are\ud arisen in our surveys. The proposed approach demonstrates better performance (packet \ud loss, latency and signaling cost), less VHO connection failure (probability of minimising \ud VHO reject sessions), less complexity and an enhanced VHO compared with that found\ud in the literature. It consists of a procedure which is implemented by an algorithm. \ud The proposed procedure of loose coupling and Mobile Internet Protocol version 4 \ud (MIPv4) provides early buffering for new data packets to minimise VHO packet loss and \ud latency. Analysis and simulation of the proposed procedure show that the VHO packet \ud loss and latency are significantly reduced compared with previous MIPv6 procedures \ud found in the literature.\ud The proposed algorithm is composed of two main parts: Handover Initiation and \ud Optimum Radio Access Technologies (RATs) list of priority. The first part includes two \ud main types of VHO and gives priority to imperative sessions over alternative sessions. III\ud This part is also responsible for deciding when and where to perform the handover by \ud choosing the best RATs from the multiple ones available. Then, it passes them to the \ud decision phase. This results in reducing the signaling cost and the inevitable degradation \ud in Quality of Service (QoS) as a result of avoiding unnecessary handover processes. The \ud second part defines RATs list of priority to minimise VHO connection failure. Analysis \ud and simulation based performance evaluations then demonstrate that the proposed \ud algorithm outperforms the traditional algorithms in terms of: (a) the probability of VHO\ud connection failure as a result of using the optimum RATs list of priority and (b) the\ud signaling cost and the inevitable degradation in QoS as a result of avoiding unnecessary \ud handover processes.