1Centre Tecnologic de Telecommunication de Catalunya (CTTC), Access Technologies Research Area, ParcMediterrani de la Tecnologia, Av. Canal Olimpic-Casstelldefels, 08860 Barcelona, Spain 2LIP Laboratory ENS Lyon, Institut National de Recherche en Informatique et en Automatique (INRIA), 46, allee d’Italie, F-69364 Lyon Cedex 07, France 3Department of Electrical and Computer Engineering, Queen’s University, Kingston, ON, Canada K7L 3N6 4Communication Networks Laboratory, Department of Informatics & Telecommunications, University of Athens, Panepistimiopolis, Ilisia 15784, Athens, Greece 5Defence & Security, Defence Electronics, EADS Deutschland GmbH, 89070 Ulm, Germany