Visual Media Coding and Transmission

7.2 State of the Art: Wireless Multimedia Communications

7.2.1 QoS in Wireless Networks

In a wireless environment, providing multimedia applications that deliver text, audio, images, and video (often in real time) with a QoS guarantee is a complex problem, due to, for example, the limited bandwidth resources and time-varying transmission characteristics of wireless channels, caused by user mobility and interference. In addition, QoS provisioning has many interrelated aspects, such as resource allocation, call admission control, traffic policing, routing, and pricing. QoS in wireless networks may be supported at three levels: the connection level, the application level (or packet level), and the transaction level.

Connection-level QoS is related to connection establishment and management, with parameters such as call-blocking probability, which measures service connectivity, and call-dropping probability, which measures service continuity during handoff [1].

New-call-blocking and existing-call-dropping probabilities have been considered central and critical QoS parameters in mobile networks [2,3]. Dropping an ongoing call is assumed to be more annoying than blocking a new call. Therefore, minimizing the call-dropping probability is usually a main objective in wireless system design. On the other hand, the goal of a network service provider is to maximize revenue by improving network resource utilization, which is usually associated with minimizing the call-blocking probability while ...