Abstract
Classrooms and laboratories of tomorrow are most likely enhanced with virtual presence in cyberspace allowing students and instructors to participate in the learning sessions using advanced Virtual Leaning Environments (VLE). These settings let difficult courses of science and engineering to be available for larger student " audiences. Despite vast technological advances in recent years, there are significant challenges suggesting further research and developments to ensure virtual classrooms be as good as or even better than what we have now in our physical lecture halls. This paper provides a state-of-the-art survey on a number of existing VLE solutions pinpointing their strengths and limitations. We distinguish between asynchronous distance learning and the synchronous settings whose model allows live participation of the learners as well as collaboration possibilities between them. Furthermore, we examine whether the selected VLEs maintain any virtual presence of the participants and scalability of the platform. Other comparison criteria include user interface, gesture & facial recognition, availability, affordability, compatibility and social awareness. As the virtual world moves closer to represent the real world, how these environments might facilitate different types of interactions inherent in a real classroom will largely dictate their future usefulness.