Mobility Protocols and Handover Optimization: Design, Evaluation and Application

Chapter 1Introduction

Wireless connectivity to communications and information has advanced the world towards ubiquitous computing. In the space of less than thirty years, cell phones have become ubiquitous and wireless data access has become common. However, this access has brought with it a variety of technical problems. Radio physics and power constraints, the need to reuse spectrum, economic constraints on facility placement, and service balkanization due to competitive and political factors force us to implement wireless systems as cells of limited range. Furthermore, cells may use very different wireless technologies or provide fundamentally different services, such as VoIP (Voice over IP), streaming, or direct short-range communications for telematics. We then need handoff mechanisms, often in multiple protocol layers, to allow a mobile terminal to move from cell to cell and maintain service continuity.

Mobility can be described as movement of a terminal, resulting in the release of the terminal's binding to the current cell (point of attachment to the network) and the establishment of bindings to the new cell being entered, while preserving the existing sessions associated with higher-level services. The cellular telephony community has long implemented service- and technology-specific mobility protocols that hand off voice sessions as the user moves from cell to cell. Because voice service quality is highly sensitive to service interruptions, cell-to-cell handoffs in ...