Mobility Protocols and Handover Optimization: Design, Evaluation and Application

Preface

In a span of less than thirty years, cell phones have become ubiquitous, and wireless voice and data have become one of the most common methods of communication today. Wireless networks have also evolved to support much higher bandwidth and lower end-to-end delay, supporting delay-sensitive applications such as interactive voice and video. For example, the 1G and 2G networks that were deployed in the late 1980s and early 1990s could only support data rates of up to a few tens of kilobits per second, in addition to voice communication, but by the start of the new millennium, they had evolved into 3G networks supporting up to 2 Mb/s data rate. Currently, 4G networks, primarily based on LTE, HSPA+, and, to a lesser extent, WiMAX, are being deployed that support multimedia communication and provide data transfer rates up to 100 Mb/s while reducing access packet delay to 50 ms. As these networks have been improving, there has also been a dramatic growth in the use of mobile devices and bandwidth-intensive applications, primarily in entertainment and interactive video. All of these applications are sensitive to disruptions due to handoffs between different cell sites and networks. Driven by increased data needs and limited spectrum availability, cell sizes are shrinking, leading to further increases in handoff frequency.

Recently, increased indoor usage and the availability of cheap Wi-Fi access points have motivated interest in heterogeneous networks, combining base stations ...