Abstract:
In the evolution of mobile and wireless communications, four generations can be identified. In 1980s, the first generation (1G) provided support for analog communication at very low bitrates. In 1990s, the second generation (2G) marked the transition to digital communications and an increase in bitrates, whereas in 2000s the third generation (3G) saw the introduction of broadband to mobile communications, leading the way towards the beyond 3G generation (B3G) and forth generation (4G). 4G represents the grand vision of mobile communications, providing mobile users access to advanced applications comparable to those offered by wired networks and, most importantly, maintaining the mobility support which is impossible in wired networks. The evolution of applications was also extremely rapid, but most importantly was inter-twined with that of the computing devices on which they run. In early years the addition of the graphical user interface to the basic word processing applications was considered an important leap in the development of applications. The latest addition to this concentrated effort was the support for mobility, which offered a rich new avenue for applications development, but put significant pressure on finding solutions, mostly in terms of quality-oriented data communications. In this context, the thesis covers important aspects of the emerging technologies in the heterogeneous next generation network environment with focus on wireless communications and quality of multimedia. It describes in details several important communications standards, identifies research issues and challenges and presents a survey of the proposed solutions in the literature. The thesis introduces the newly proposed Dynamic Quality-Oriented Adaptation Scheme (DQOAS), a user-oriented adaptation mechanism that improves user quality of experience (QoE) while also enabling a higher number of simultaneously connected clients to communicate in an IEEE 802.11 or a 3GPP LTE network. DQOAS enhances an existing solution, the Quality-Oriented Adaptation Scheme (QOAS) by adding different user QoE expectation levels in the adaptation process. By making use of these levels, DQOAS will perform a differentiated treatment of the users in the adaptive process, based not only on network conditions, but also on user requirements in terms of their QoE. When DQOAS is deployed in an LTE environment, its intrinsic prioritization offers a mapping alternative for LTE QoS parameters in case of a traffic mix generated by one application, in order to improve end-user QoE.
