Preface

The growth in the use of mobile networks has come mainly with the third generation systems and voice traffic. With the current third generation and the arrival of the 4G, the number of mobile users in the world will exceed the number of landlines users. Audio and video streaming have had a significant increase, parallel to the requirements of bandwidth and quality of service demanded by those applications. Mobile networks require that the applications and protocols that have worked successfully in fixed networks can be used with the same level of quality in mobile scenarios.

One of the main differences between fixed and mobile networks lies in the dynamic nature of the latter. The constant movement of mobile devices has a clear impact in the quality of service that can be achieved (delay or loss of packets during a handover from one cell to another). The migration of mechanisms initially meant for fixed networks to mobile networks may cause problems related to topology and mobility factors. Other difficulties may appear when we want to move mechanisms designed for infrastructure and wired networks to ad-hoc or mobile networks in general. These are some of the drawbacks:

Problems related to topology:

One of the great remaining difficulties from the first generation to the fourth generation of mobile devices occurs when there is a handover, either from one cell to another or from one access network to another. This circumstance clearly affects the quality of service in diverse ways: delay of packet transfers, increase of the jitter of audio and video streaming or even damage or loss of packets. There are different types of handovers that produces diverse signalling loads in the access network. A handover involves a route variation in order to reach the mobile terminal. To provide a good level of QoS in mobile environments, a minimal handover delay is always welcome to ensure the smallest traffic interruption during a transfer.

Problems related to mobility: macromobility and micromobility.

