Multipoint Videoconferences Research Articles

Discrete bit loading and power allocation for OFDMA downlink with minimum rate guarantee for users

Performance optimization of the communication networks with quality of service (QoS) considerations for all active users is of great practical importance in highly delay-sensitive applications like multipoint videoconferences and interactive video games. Using minimum data rate as the primary criterion for the QoS and the BER as a second one, in this paper, we provide the optimum discrete bit loading for an OFDMA downlink in which the QoS of all users are satisfied. We formulate the problem and solve the dual problem efficiently and without any suboptimality. Albeit the problem is non-convex, it has been shown that the duality gap tends zero in practical scenarios. We propose a novel approach to solve the dual problem by decomposing dual function and finding discrete rate allocation solution for practical applications. Also, we present a novel fast converging iterative algorithm to find the solution with much less complexity compared to that of well-known ellipsoid optimization algorithm. We analyze the complexity of these solutions, and using simulation results, show the superiority of our novel approach.

Design of a service platform for delay-sensitive video streaming applications based on multicast p2p and scalable MDC encoding

The great diffusion of Internet accesses in the world and the enormous evolution of the Internet technologies have strongly determined dissemination and consolidation of many applications of video content distribution. However, multicast real-time video communications for interactive service applications with a very high number of users, like for example multipoint videoconferences and interactive video games, remains a challenging research topic for the presence of very strict requirements in terms of end-to-end delay and perceived quality.The target of this paper is to propose a video distribution platform that is able to provide a huge number of users with a delay constrained multicast video streaming. To this purpose, the proposed content delivery platform is based on a peer-to-peer approach that exploits multicast overlay organization of the peers to address the challenges due to bandwidth heterogeneity. To improve reliability and flexibility, video is coded using a scalable multiple description approach. Some design guidelines are provided taking into account some requirements in terms of delay, average PSNR, robustness against underlying network bandwidth fluctuations, and fairness.

Improving Proton Therapy Accessibility Through Seamless Electronic Integration of Remote Treatment Planning Sites

Proton radiotherapy is a relatively scarce treatment modality in radiation oncology, with only nine centers currently operating in the United States. Funded by Public Law 107-248, the University of Pennsylvania and the Walter Reed Army Medical Center have developed a remote proton radiation therapy solution with the goals of improving access to proton radiation therapy for Department of Defense (DoD) beneficiaries while minimizing treatment delays and time spent away from home/work (time savings of up to 3 weeks per patient). To meet both Health Insurance Portability and Accountability Act guidelines and the more stringent security restrictions imposed by the DoD, our program developed a hybrid remote proton radiation therapy solution merging a CITRIX server with a JITIC-certified (Joint Interoperability Test Command) desktop videoconferencing unit. This conduit, thoroughly tested over a period of 6 months, integrates both institutions' radiation oncology treatment planning infrastructures into a single entity for DoD patients' treatment planning and delivery. This telemedicine solution enables DoD radiation oncologists and medical physicists the ability to (1) remotely access a proton therapy treatment planning platform, (2) transfer patient plans securely to the University of Pennsylvania patient database, and (3) initiate ad-hoc point-to-point and multipoint videoconferences to dynamically optimize and validate treatment plans. Our robust and secure remote treatment planning solution grants DoD patients not only access to a state-of-the-art treatment modality, but also participation in the treatment planning process by Walter Reed Army Medical Center radiation oncologists and medical physicists. This telemedicine system has the potential to lead to a greater integration of military treatment facilities and/or satellite clinics into regional proton therapy centers.

A Brazilian educational experiment: teleradiology on web TV

Since 2004, educational videoconferences have been held in Brazil for paediatric radiologists in training. The RUTE network has been used, a high-speed national research and education network. Twelve videoconferences were recorded by the Health Channel and transformed into TV programmes, both for conventional broadcast and for access via the Internet. Between October 2007 and December 2009 the Health Channel website registered 2378 hits. Our experience suggests that for successful recording of multipoint videoconferences, four areas are important: (1) a pre-planned script is required, for both physicians and film-makers; (2) particular care is necessary when editing the audiovisual material; (3) the audio and video equipment requires careful adjustment to preserve clinical discussions and the quality of radiology images; (4) to produce a product suitable for both TV sets and computer devices, the master tape needs to be encoded in low resolution digital video formats for Internet media (wmv and rm format for streaming, and compressed zip files for downloading) and MPEG format for DVDs.

Videoconferencing in the Queensland health service.

Videoconferencing was introduced in the Queensland health service in 1995. By the end of 1999, there were more than 150 videoconferencing units in health facilities around the state. Six audits of videoconferencing usage were conducted using similar methodology at six-month intervals from November 1997 to May 2000. Between November 1997 and November 1999, the number of calls more than doubled, from 566 to 1378. Hours of usage almost trebled, from 671 to 1724. The average duration of calls remained similar, at about 1 h 12 min. The proportion of calls involving more than two sites (multipoint videoconferences) increased from 44% to 65%. The majority of the activity was for education (including training). Videoconferencing was also used for administration and clinical care. Mental health staff were the heaviest users, but use by health professionals from other specialty areas increased during the study period. The Queensland health service has realized a number of important benefits from telehealth.

Guidelines for multipoint videoconferencing using low-cost, PC-based equipment.

We have compiled a set of guidelines for effective multipoint videoconferencing carried out with low-cost, PC-based systems. The guidelines are based on experience gained during multipoint videoconferences in epidemiology and orthopaedics/radiology. Joint data inspection and manipulation were carried out by application sharing between the PCs. The guidelines are categorized by the time of their application and also by their content. For effective multipoint videoconferences, preparation of the agenda and of digital documents is mandatory. The prevention of echo effects and half-duplex audio connections are of special importance. A protocol to optimize the order of speakers increases the efficient use of conference time. The guidelines worked well when used in a multisite research project and addressed the most important weak points of multipoint videoconferences using low-cost equipment.

Analysis of multipoint videoconferencing under reroutable route-configuration assignment

In this paper, we study the use of reroutable assignment for multipoint videoconferences in a high-speed network. A conference model is constructed and conference calls are classified. A conference of a particular type can ride on different route-configurations. According to the location of the current speaker, a conference has different modes of operation. Two network management functions are discussed: call admission ensures a preset quality-of-service requirement by blocking new calls that causes congestion; route-configuration assignment determines the multicast tree for distributing the video of the current speaker. The reroutable route-configuration assignment is introduced. It allows a change of route-configuration when there is a change of speaker. Two reroutable assignment schemes are studied. In the normal scheme, a conference is always rerouted to the least congested route-configuration; while in the sticky scheme, a conference is only rerouted when the current route-configuration is congested. The video freeze probability, rerouting probability and the extended capacity space are derived. An example shows that the video freeze probabilities of the two schemes do not differ significantly. The sticky scheme, however, is superior as it gives a much smaller rerouting probability than the normal scheme. © 1998 John Wiley & Sons, Inc.

Dynamic bit allocation in video combining for multipoint conferencing

For multipoint video conferencing over a wide-area network, a video bridge is often used to combine the coded video signals from multiple participants into a single video for display. The video combining can be done in the coded-domain by concatenating coded video bitstreams, or in the pixel-domain by transcoding. In this paper we compare the video quality using the two approaches for a multipoint video conference over a symmetrical wide-area network such as Integrated Service Digital Network (ISDN). We observe that in most multipoint video conferences usually only one or two persons are active at one time, while other participants are just listening with little motion. To achieve similar video quality for all the conference participants, the active persons require higher bit rates than the inactive persons. By doing video combining using the transcoding approach and dynamically allocating more bits to the active persons, we show that the achieved video quality can be much better than that can be achieved using the coded-domain video combining approach.

Connection optimisation for two types of videoconference

The connection optimisation problem for two types of multipoint videoconferences is formulated. The first type is called a selectable media conference. In this type each conferee can choose to receive a particular video composition. In the second type, called a common media conference, only one composite video is generated for all conferees in this type of conference. Algorithms that use a combination of look-up table and online processing are designed for computation of the optimal paths for connecting the conference sites. The blocking probabilities for these two types of videoconference in fully connected networks are derived and compared. The sensitivity of network throughput to conference-size distribution is also studied.