Videoconference Services Research Articles

Satellite services for disaster management and security applications

Advantages of communications satellites are the inherent broadcast capability, high bandwidth, reliability and flexibility in network expansion. Small transportable terminals can be made operational very quickly. Recent developments in communications and computer technology allow to provide low-cost equipment, which is affordable even in developing countries. Communications satellites can also play an important role in case of emergencies or natural disasters. The combination of satellite communications and navigation can support new services for emergency teams. At the Institute of Applied Systems Technology and the Institute of Communication Networks and Satellite Communications highly transportable terminals have been developed, both for star and mesh network topologies. A fully meshed VSAT system is used for symmetrical links. For other applications, which do not require high return link capacity an asymmetrical system is an efficient solution. It uses low-cost DVB technology for the forward link and satellite phones with data capability on the return link. Novel multicast protocols allow to use these asymmetrical links in an efficient way. The paper describes the different systems and their applications in disaster management and security applications. Emphasis is put on transfer of remote sensing images and voice over IP (VoIP) as well as videoconference services.

Broadband nursing: a multi-method evaluation of a one-way video-conferencing health information and advice service: "InVision"

Broadband nursing: a multi-method evaluation of a one-way video-conferencing health information and advice service: "InVision"

Evaluation of the Cable Modem Technology DOCSIS 1.0 in an MMDS Access Network for Video Conference Services

The Cable Modem technology evaluation under the DOCSIS 1.0 specification operating in an MMDS (Multichannel Multipoint Distribution System) access network for video conference service is carried on this work in a qualitative and quantitative approach, making observations in videoconference terminals, modems and access network. The results obtained show the need to add quality of service tools, for IP traffic over Cable Modem technology in order to get a better performance in videoconference applications. The conclusions of this work can be extended to other VoIP services under this technology.

Evaluation of the Cable Modem Technology DOCSIS 1.0 in an MMDS Access Network for Video Conference Services

Evaluation of the Cable Modem Technology DOCSIS 1.0 in an MMDS Access Network for Video Conference Services

Architectural design and bandwidth demand analysis for multiparty videoconferencing on SONET/ATM rings

In this paper, we propose a scheme for implementing multiparty videoconferencing service on SONET/ATM rings. We focus on the architectural design and bandwidth demand analysis. Different multicasting methods on SONET/ATM rings are discussed and compared. A new multicast virtual path (VP) called Multidrop which is particularly suitable for SONET/ATM rings is proposed. An add-drop multiplexer (ADM) structure for rings capable of multidropping is also presented. Several VP assignment schemes are proposed and their bandwidth utilizations are compared.

Performance analysis of a prototypal multimedia service in an intelligent broadband network

Advanced multimedia multiparty services call for sophisticated signalling systems able to manage multiple parties and media in broadband environments. In this paper we dealt with the support of multimedia applications in an Intelligent Broadband Network (IBN), where the Intelligent Network, in a closed interaction with the B-ISDN, furnishes control functionality to handle complex service configuration. Some different options for an IN/B-ISDN interaction are discussed starting from the results of the INSIGNIA project (carried out in the framework of the European Union ACTS program) where a prototypal IBN system has been specified and developed in a field trial. Two main architectural solutions are discussed and a generic modelling methodology for the performance analysis of the control plane is presented. The objective of this modelling methodology is to provide insights into the behaviour of the system under dynamic conditions and to capture the influence of alternative functional settings. The proposed model is applied to the evaluation of the support of the Broadband Video Conference service in the prototypal system as well as to compare the performance of alternative architectural solutions for the IBN.

Congestion control for multipoint videoconferencing

Multipoint videoconference service allows multiple and far-away conferees to conduct a meeting without leaving their offices. Variable-bit-rate video compression is attractive for videoconferencing, because it can provide a constant image quality and it can effectively utilize the communication bandwidth via statistical multiplexing. When some conferences temporarily generate heavy traffic to a link, congestion occurs and some video packets have to be discarded. Since the packets of different conferences are multicast to different number of conferees, the loss of different packet will affect different number of people. If we discard the packets sent to the smallest number of conferees, we can minimize the number of affected conferees to give the best mean quality of service, but the conference having a smaller number of conferees will suffer from a poorer quality of service. Therefore, we must consider both the mean quality of service and fairness in congestion control. We propose a congestion-control strategy for multipoint videoconferencing. This strategy has a control parameter which we can tune to make a tradeoff between the mean quality of service and fairness. In addition, the strategy only involves some simple arithmetic and logic operations, and hence, it can be executed quickly for real-time congestion control.

Videoconference Traffic and Network Design

Recent technological progress is making possible the creation of a new form of videoconference service based on a public network interconnecting private studios located on user premises. We suppose that transmission links in such a network would be reserved in advance by users as and when they arrange their meeting. This and other significant differences with telephony-like services make the use of traditional teletraffic models inappropriate for network dimensioning and performance evaluation. In this paper, we propose an original model of the videoconference reservation traffic process in which essential parameters are the size and distribution of the studio population and the mean studio busy hour utilization rate. This model is used to study certain network architectures in order to identify the effect on link and node dimensions of major design options. First conclusions suggest that the most economical structure might be a simple star network where all studios are connected directly to a central switching facility. Advance reservation makes it possible to employ elaborate routing algorithms, such as call rearrangement, which might be exploited to optimize network or switching node design.