The most prevailing feature that led to the massive success of current Wireless Mobile Tele-Communication systems, is mobility. Being able to communicate on the go, anywhere and anytime has revolutionized modern day communication. In recent times the focus has not been only on simply being reachable while on the move but at the same time to use a variety of rich media content services over a variety of available network technologies, termed as 4G networks. The telecommunication development from the very beginning took two different tracks. One was the Internet which provided a fixed means of communication delivering rich media content taking full advantage of its packet switched nature. The second track was that of the cellular systems taking advantage of their circuit switched nature providing mainly voice and short messaging services to wireless and mobile users. In time both these technologies made major advances following their own respective tracks and it became evident that the convergence of both these technologies would be of even greater value. The driving force for this convergence was that a great need was felt for the support of mobility in the Internet. But since the Internet was not designed keeping mobility in mind, it did not support mobility by design. On the other hand in cellular systems in addition to circuit switching, packet switching was needed for flexibility, to make better use of network resources, and to deliver rich media content to the user at cheaper prices.
For non-mobile user’s, packet switched networks performed really well in providing the required Quality of Service (QoS). However such networks faced considerable problems to achieve similar QoS for mobile users. With no support for mobility in the Internet from scratch, new components and functionalities were needed to be incorporated into the Internet for mobility support. Examples of such functionality include location tracking, network discovery, packet re-routing to the current point of attachment of the Mobile Node (MN), accounting, authorization and authentication. Special mobility management protocols to provide the required new functionalities were needed. For this purpose the Internet Engineering Task Force (IETF) proposed Mobile IP version 4 (MIPv4) and Mobile IP version 6 (MIPv6) to support mobility for a single IP host and Network Mobility (NEMO) protocol to support mobility for a whole network in motion. These protocols have the ability to maintain data connections for mobile IP enabled devices when they roam across different subnets or networks. When a mobile user moves across network boundaries, it has to perform handover to maintain its connections. When performing a handover a MN may not be able to send or receive data packets therefore the handover duration becomes a critical factor in guaranteeing real time applications (e.g. Voice over IP (VoIP)) their QoS.
The purpose of this research work is to deal with handover issues in packets switched networks. A stepwise approach was followed during this study. Starting at layer-2 of the TCP/IP protocol stack and after identifying major problems at this layer for 802.11 networks, solutions were devised for seamless handovers by utilizing the Media Independent Information Service (MIIS) of the Media Independent Handover (MIH).
After dealing with major handover issues at the MAC layer of 802.11 networks, the work moved one layer up in the TCP/IP protocol stack to layer three or the IP layer. The MIH framework which was originally proposed for vertical handovers is proposed to be utilized for improving the efficiency of horizontal handovers. Keeping the research work focused on horizontal handovers in 802.11 networks only, an Access Point (AP) selection scheme is proposed and an investigation was carried out regarding the implications of proposed solutions at the MAC layer, on MIPv6 handover delays.
In the next step, the study is extended to vertical or heterogeneous handovers. This part proposes to break up a heterogeneous handover algorithm in a Wi-Fi/WiMAX integrated environment, into two parts. The handover algorithm parts are proposed to be executed separately from each other distributed among multiple network components, resulting in intelligent resource utilization and good scalability, without sacrificing handover efficiency.
For proof of concept and the effectiveness of the proposed schemes simulations were performed in Network Simulator-2 (ns-2) for a scenario in which a MN moves linearly in the topology, performs handovers and makes use of MIH facilities for improved handovers.
An important portion of this research also deals with the analysis of a variety of NEMO route optimization schemes proposed in the literature and their implications on handovers in NEMO networks. The goal of this part is to overview the handover signaling complexity of the various proposed NEMO route optimization schemes.