XII Preface

Although the two types of handovers occur under both circumstances, intra-domain handovers will be a priority due to their higher frequency of signalling load and packet transfers. One of the greatest difficulties in reducing the mobility impact in the terminals when there is a handover is that the protocols or mechanisms to provide quality of service are designed and limited to a certain kind of fixed or mobile networks or at macromobility level. Using these existing mechanisms of QoS involves adapting the dynamic characteristics of the mobile devices. There are cases such as adhoc networks that have special mobility specifications, making migration a complex challenge.

Until the third generation of mobile networks, the need to ensure reliable handovers was still an important issue. On the eve of a new generation of access networks (4G) and increased connectivity between networks of different characteristics commonly called hybrid (satellite, ad-hoc, sensors, wired, WIMAX, LAN, etc.), it is necessary to transfer mechanisms of mobility to future generations of networks. In order to achieve this, it is essential to carry out a comprehensive evaluation of the performance of current protocols and the diverse topologies to suit the new mobility conditions.

> **Dr Jesús Hamilton Ortiz**  School of Computer Engineering, University of Castilla La Mancha, Ciudad Real Spain
