Apostolis K. Salkintzis, Motorola Inc., Greece Received his Diploma in 1991 and his Ph.D. degree in 1997, both from the Department of Electrical and Computer Engineering, Democritus University of Thrace, Xanthi, Greece Worked as a research Engineer at the Democritus University, studying mobile data networks and working on research projects dealing with the design and implementation of wireless data networks and protocols. Was a Sessional Lecturer at the Department of Electrical & Computer Engineering, The University of British Columbia, Canada, in 1999. Has been with Motorola Inc., since Sept. 1999, working on the design and standardization of modern telecommunication networks, focusing in particular on GPRS, UMTS and WLANs. Is a member of the IEEE and a member of the Technical Chamber of Greece. Nikos Passas, University of Athens, Greece Received his Diploma (honours) from the Department of Computer Engineering, University of Patras, Greece, and his Ph.D. degree from the Department of Informatics and Telecommunications, University of Athens, Greece. Has been with the Communication Networks Laboratory of the University of Athens, working as a sessional lecturer and research associate since 1995.