1. University Politehnica of Bucharest,Telecommunications Department,Bucharest,Romania
2. School of Electr. & Comp. Eng., Aristotle University of Thessaloniki,Thessaloniki,Greece,54124
3. SingularLogic S.A.,European Projects Department,Athens,Greece,14564
4. School of Computing and Engineering, University of Huddersfield,Huddersfield,UK,HD1 3DH