- Visited Imperial College, UK , May 2010.
- Visited Imperial College, UK , Dec 2009.
- Visited University of Southampton, August 2006.
- Visited Imperial College, University of London, November-December 2004.
- Visited University of Northern British Columbia (UNBC), Prince George, BC, Canada,
- Visited Imperial College, London, October 2003.
- Visited University of Tromso, Norway, September 2002.
- Visited University of Texas at Arlington, USA, December 2001.
- Visited Carnegie Mellon University,USA, December 2001.
- Visited Kent Ridge Digital Labs,Singapore, November 2001.
- Visited University of Tunisia, TunisTunisia, July 2001.
- Visited L'Universite Bordeaux,France, June 2001.
- Visited University of London,England, September 2000.
University of Pisa, Italy, and Centro Studi E Laboratori
Telecommunicazioni S.P.A (CSELT), Torino, Italy, November
- Visited Western Sydney University, University of New South Wales,
- Visited University of Toronto, University of Ottawa, and University
Carleton, in Canada, in early 1998.
- Visited University of California at Berkeley, Intl. Computer Science
Institute (ICSI), University of California at San Diego (UCSD), and QUALCOM
research center , in USA, in winter
- Visited Orrego University, Trujillo, and University of Lima,
Lima in PERU (1996)
- Visited University of Twente, Enschede, Delft University and
of Amsterdam in NETHERLANDS (1995)
- Visited Electronics and Telecommunications Research Institute
Seoul, Samsung Advanced Research Center, Seoul and Seoul National University,
Seoul, in Korea (1995)
- Visited University of Montreal, Concordia University, University of
Ottawa and BNR labs, Montreal in CANADA
- Visited University of Maryland at Baltimore, John Hopkins University,
University of Maryland at College park, Bowie University, and Telecommunication
center, Baltimore in USA (1992)
- Visited University of California, Los Angeles, University of
Berkeley, Washington State University, Seattle in USA
- Visited National University of Singapore, Institute of Systems
in Singapore (1988)