Controlling quality of session in adaptive multimedia multicast systems

Controlling the quality of collaborative multimedia sessions, that deploy multiple media streams, is a challenging problem. In this paper we present a framework for achieving quality of session (QoSess) control focusing on two main components of the QoSess control layer. The first component is a scalable and robust feedback mechanism which allows for determining the worst case state among a group of receivers of a stream. This mechanism is used for controlling the transmission rate of multimedia sources in the cases of layered and single-rate streams. The second component is the inter-stream bandwidth adaptation mechanism that dynamically controls the bandwidth shares of the streams belonging to a session. We compare the performance of several adaptation algorithms. Additionally, in order to ensure stability and responsiveness in the inter-stream adaptation process, several measures are taken, including devising a domain rate control protocol. The performance of our mechanisms is analyzed and their advantages are demonstrated by simulation and experimental results.