A Study on Enhancement of User-Level QoS by Utilizing Mutually Compensatory Property of Multimedia

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This research deals with user-level QoS of audio-video IP transmission. The research results can be classified into the following five categories.1.The first subject is quantitative assessment of user-level QoS. We have studied the effect of monitor size, a scheme of continuous-time assessment and multidimensional assessment.We have also proposed a real-time estimation scheme using video spatial quality and audio-video temporal quality.2.We have investigated how the MAC protocols in IEEE802 11 affect application-level and user-level QoS A method for testing the feasibility of user-level QoS has been proposed for DCF and EDCA with and without media synchronization control. EDCA with TXOP-Bursting was evaluated in error-prone environments. We also proposed a method for user-level QoS guarantee with-HCCA and showed its effectiveness. In addition, we applied DCF and EDCA to ad hoc networks and evaluated QoS3.We have assessed user-level QoS in multipoint -to -multipoint TV conferencing applications with a multidimensional metric as well as a scalar one.4.We have studied a method of enhancing user-level QoS in bandwidth-guaranteed IP networks by utilizing the mutually compensatory property. Under the condition that the total guaranteed bandwidth of the audio-video streams is constant, we clarified how we should allocate the bandwidth between audio and video according to the content type in order to maximize the user-level QoS.5.We have proposed a SIP-based session control method that provides a mechanism to achieve desirable user-level QoS, which is referred to as GPSQ (Guarantee of Psychologically Scaled Quality). We implemented GPSQ in a simple experimental network and confirmed its effectiveness