Synchronization and Latency-Effects in Distributed Multi-Touch Tabletops in a Collaborative Environment

Multi-touch tabletops are convenient devices for co-located collaboration. However, there exist scenarios where not all participants are in the same physical location. To be able to collaborate using multi-touch tabletops in a remote setting we introduce the concept of distributed multi-touch tabletops. That is a system in which multiple tabletops show the same application, and control of the application in the form of multi-touch gestures is exchanged between connected tabletops. In this thesis, we present a protocol and framework implementation for writing dis- tributed multi-touch applications. Traffic generated by this framework was analyzed in several real-world network settings. Network delays and variations in this delay show the necessity of a coordination process: synchronization. Synchronization in multi-touch ges- ture exchange is defined at several levels. The impact of network latency on task execution performance was measured in a user study. Using three distributed multi-touch applica- tions, thirteen couples of two participants executed three collaborative tasks while their task completion times were measured. The tasks were executed co-located, and distributed with simulated network delays of 0ms, 100ms, 500ms, 1000ms, and 2000ms. The results show that there is no significant difference in performance between co- located and distributed task execution. Furthermore, task execution times are significantly higher at relatively large network latencies of 500ms and 1000ms.