The latest advances in wireless data access technologies and increased popularity of mobile computing have enabled the development of the future mobile Internet. The various wireless technologies and standards already developed or under development support the existence of a highly heterogeneous wireless communication environment in which mobile users access the network from diverse devices and exchange data of various types. In the context of such a heterogeneous wireless and mobile environment, maintaining certain level of Quality of Service required by some applications and consequently providing high user Quality of Experience is very challenging. This chapter analyzes the state of the art in quality-oriented mobility management in heterogeneous wireless environments in the context of mobile multimedia applications. Most important wireless access technologies and multimedia support systems and protocols for wireless delivery are presented, while requirements for quality-oriented mobility management are identified. Handover management is discussed as the component of the mobility management system with the greatest impact on the quality as measured by the user. Finally a novel multimedia mobility management framework is presented which aims at maintaining high user perceived quality while efficiently exploiting all the communication resources available in a heterogeneous wireless environment.
TopIntroduction
Mobile communication devices have evolved rapidly from the legacy analogue mobile phones to the currently high computational performance mobile devices. Considering the large variety of computing devices available on the market one may observe two interesting trends. The once large computers (desktop computers) are becoming smaller while maintaining, if not increasing, their computational and communication capabilities and providing support for mobility (laptop computers). At the same time the mobile phones which used to have very limited capabilities include increasing computational power and data communication features as well as advanced graphical user interfaces (smart phones).
Consequently mobile devices are widely available in various forms with increased capabilities in terms of computational power, graphical display capabilities and most important in terms of data communication resources. Having all these features available, the Internet users start accessing various services (i.e. web surfing, e-mail, multimedia applications, online gaming, etc.), they once accessed using traditional desktop PCs, from wireless enabled mobile devices (i.e. smart phones, personal digital assistants - PDAs, notebook PCs, etc.). The electronic services, including the ones mentioned before and many others, provide important benefits to their users in their professional and social lives. Making these services “location independent” increases their availability and allow the users to access them in a more flexible and efficient way. In order to have all these services available to mobile users, wireless networking environments need to be available. Various wireless access technologies have been developed in the last decade. Wireless access technologies provide data communication services with bandwidth closer to that of wired solutions, but having the highly valuable benefit of mobility (which is not the case of their wired counterparts) (Kuran, 2007; Ortiz, 2007). The current standardized or under development wireless access technologies range from Wireless Local Area Networks (WLAN), Wireless Metropolitan Area Networks (WMAN) and Wireless Wide Area Networks (WWAN) to cellular networks (2G, 2.5G, 3G, and 4G).
In the context of the large variety of wireless access technologies available, the future of networking goes towards an all Internet Protocol (IP) network environment which provides Internet access to a variety of computational devices. The IP protocol stack is a good choice for incorporating the emergent heterogeneous wireless environment, mainly because of the cost effectiveness and flexibility of its layer-based model. However the main disadvantage of the original IP stack is the lack of mobility oriented design. Consequently mobility management support has to be incorporated in the current IP stack.
Considering the heterogeneity of the wireless networking environment and the wide range of applications running on the user mobile device as schematically described in Figure 1, mobility management has the challenging task of providing applications with required Quality of Service (QoS) levels in the context of host mobility and wireless networks dynamics. Real-time multimedia applications are increasingly popular among the Internet users. For these applications to be successful on long term, the service providers have to make sure that the user perceived service quality is at high levels.
Figure 1. Multimedia streaming over a heterogeneous wireless environment
This chapter focuses on quality-oriented multimedia delivery to mobile devices over heterogeneous wireless networks. Mobility management as a whole is discussed and handover management is presented in details as one of the major components of a mobility management system in relation to quality. The requirements of a quality oriented mobility management system are identified and several current solutions are presented. A novel multimedia mobility management framework is presented which aims at maintaining a high user perceived quality while efficiently exploiting all the communication resources available in a heterogeneous wireless environment.