An Adaptive Videoconferencing Framework for Collaborative Telemedicine

In the medical area, most of medical facilities (hospitals, clinics, ...) use distributed applications, such as telediagnosis for example. As information security is mandatory, these applications must be able to cross the security protocols (secured gateways like proxies, firewalls ...). User Datagram Protocol (UDP), which is classically recommended for videoconferencing applications, does not cross firewalls or proxies unless explicitly configured fixed ports are declared. These fixed ports are considered as a security breach. In this paper, we propose a new and novel platform called VAGABOND (Video Adaptation framework, crossing security GAteways, Based ON transcoDing) which works, in a very efficient and original way; on TCP (Transmission Control Protocol). VAGABOND is composed of Adaptation Proxies (APs), which have been designed to take into consideration medical experts videoconferencing preferences, device heterogeneities, and network dynamic bandwidth variations. VAGABOND is able to adapt itself at the user and network levels. The cumulative binomial probability law and the Bayesian inference on a binomial proportion are used to trigger user profile adaptations. Probabilities are calculated based on the number of retained video packets on all those received in a given lapse of time. A Bayesian inference is used to calculate a posterior probability by taking into account a prior and a likelihood. With the Bayesian probability interpretation, Baye's theorem expresses how a subjective degree of belief should rationally change to account for evidence. In fact, we aim at being more tolerant to severe network bandwidth variations. With a finer precision and following these probability laws, user profile adaptation is only triggered when severe network congestions arise. The framework uses TCP for the delivery of videoconferencing data. The advantage of this protocol is its ability to spontaneously cross firewalls and proxies (use of TCP ports 80 or 443). However, as TCP is a reliable transport protocol, we needed to design and to employ new intelligent adaptation strategies together with data transmission in order to cope with latency issues and sockets timeout.