Network Support for Turn-Taking in Multimedia Collaboration

Abstract

The e ectiveness of collaborative m ultimedia systems depends on the regulation of access to their shared resources, such as continuous media or instruments used concurrently by m ultiple parties. Existing applications use only simple protocols to mediate such resource contention. Their cooperative rules follow a strict agenda and are largely application-speci c. The inherent problem of oor control lacks a systematic methodology. This paper presents a general model on oor control for correct, scalable, ne-grained and fair resource sharing that integrates user interaction with network conditions Quality-of-Service, and adaptation to various media types. The notion of turn-taking known from psycholinguistics in studies on discourse structure is adapted for this framework. Viewed as a computational analogy to speech communication, online collaboration revolves around dynamically allocated access permissions called oors. The control semantics of oors derives from concurrency control methodology. An explicit speci cation and veri cation of a novel distributed Floor Control Protocol FCP are presented. Hosts assume sharing roles that allow for e cient dissemination of control information, agreeing on a oor holder which is granted mutually exclusive access to a resource. Performance analytic aspects of oor control protocols are also brie y discussed.

Number of floors for a voice-only conference on packet networks – a conjecture

“…There are detailed studies [7][8][9] on floor control for CSCW. Significantly, however, there has been no attempt to specify N. Perhaps this is due to the universal tacit assumption that only one person speaks at a time.…”

“…We do not delve into psycho-acoustic impact of mixing two or more streams but argue with an appraisal that the conference is 'well behaved' and fair. We do not intend to provide explicit 'grant floor' (GF) messages for the conferees [9] to speak. Explicit GF messaging precludes impromptu speech and disfavours natural interactions.…”