Scientific Consultant, AT&T Bell Laboratories, Murray Hill,        USA (1986, 1981)

    Visiting Scientist, NEC Europe Labs., Germany (2H08)

    Visiting Professor: Hong Kong Univ. of Science and        Technology, China (1H08)

    Visiting Professor: Politecnico di Torino, Italy (1989)

    Other Visiting assignments: CSELT - Telecom Italia Labs        (Italy), Telecom Paris (France), University of Toronto        (Canada), University of California, Los Angeles (USA),        E.T.S.I. de Telecomunicación (Madrid, Spain)

    Served as an Expert for European Commission FP6.