Discrimination of visual and haptic rendering delays in networked environments

Many networked human-machine interface systems have a distributed structure for certain purposes such as more computational power, tele-presence, collaboration, and portability. However, network delays are inevitable in the distributed structure, and often make sensory information delivered behind time to the user. In the literature, the effect of network delays on the quality of information presentation has been considered with respect to task performances in most cases. In this paper, we pay attention to a more stringent criterion, namely whether perceptual artifacts caused by network delays are perceptible by the user. We examined minimum perceptible visual and/or haptic rendering delays by measuring their discrimination thresholds between normal and delayed virtual environments with and without a task, and report the results in this paper. We also provide a simple guideline for determining whether active delay compensation algorithms are required in a networked human-machine interface system by comparing representative network delays to the measured discrimination thresholds. Recommended by Guest Editor Phill Kyu Rhee. This work was supported in parts by a grant R01-2006-000-10808-0 and a NRL grant R0A-2008-000-20087-0 both from KOSEF and by a ITRC support program C1090-0804-0002 from IITA, all funded by the Korea government. In Lee is a Ph.D student in Computer Science and Engineering at POSTECH, of Korea. He received the B.S. degree in Information and Communication Engineering from Sungkyunkwan University in 2006. His research interests include haptics, virtual reality, and human-computer interaction. Seungmoon Choi is an Assistant Professor in Computer Science and engineering at POSTECH, Korea. He received the B.S. and M.S. degrees in Control and Instrumentation Engineering from Seoul National University in 1995 and 1997, respectively, and the Ph.D. degree in Electrical and Computer Engineering from Purdue University in 2003. His research areas include haptics, virtual reality, data perceptualization, and applied perception.