Coping with inconsistency due to network delays in collaborative virtual environments

Abstract

Collaborative Virtual Environments (CVEs) are shared virtual spaces designed to enhance collaboration between the -usually remote -participants. The deployment of Collaborative Virtual Environments over wide area networks increases typical network delays, potentially breaking the consistency between the replicated versions of an environment at the participants' sites. This paper presents our qualitative observations of an experiment involving two players engaged in a virtual ball game in the presence of increasing network delays. It also describes how network delay affected the participants' behaviour and produced collaboration breakdowns. We observed that, as the network delay increases, the users modify their playing strategies in an attempt to cope with the situation, presenting several types of adaptation strategy. Knowledge of the presence and effect of delays is a major factor in allowing users to adopt strategies for coping with inconsistencies. We propose that if the participants were made more aware of the behaviour of the system, e.g. the presence of delays, then they might be able to improve their performance. Consequently, we propose a number of techniques to increase the user's knowledge of infrastructural characteristics such as delay.

The effects of local lag on tightly-coupled interaction in distributed groupware

“…In a virtual ping-pong game that has large interaction granularity, users did not seem to perceive less than 150 ms latency, and were able to keep playing up to latencies of 500 ms [22]. In contrast, a study of a racing game, where players interact more quickly, showed that latency above 100ms made the game difficult [18].…”

“…Delays can have severe effects on collaboration -on coordination, communication, and understanding of the shared situation [2,9,18,22]. Delay can make turn taking difficult to negotiate, can hinder social locking protocols, and can cause inconsistencies that lead to confusing rollback actions.…”

The Effects of Network Delays on Group Work in Real-Time Groupware

“…Limited previous research has considered delay effects on collaborative task performance in 3D virtual environments (e.g. Park and Kenyon 1999, Vaghi et al 1999). One study suggests that performance is negatively affected by latencies of only 200ms (Park and Kenyon 1999), but the "two-person thread the needle" task used differs substantially from tasks in most 2D sharedworkspace groupware systems.…”

“…One study suggests that performance is negatively affected by latencies of only 200ms (Park and Kenyon 1999), but the "two-person thread the needle" task used differs substantially from tasks in most 2D sharedworkspace groupware systems. A qualitative study (Vaghi et al 1999) saw a variety of strategy changes in the presence of latencies from 200ms -1000ms, and suggests that the task became difficult at about 500ms latency.…”

“…People may be better able to adapt their behaviour to delays if they are aware of the presence and magnitude of the delay. Delay can be represented in the interface by devices like delay gauges, or by "ghosting" effects on moving objects (Vaghi et al 1999).…”