1. Laboratoire LRIA, Université Paris 8, 15 Rue Catulienne, 93200 Saint-Denis, France
2. Center for Research in Wireles Mobility and Networking (CReWMaN), Department of Computer Science & Engineering, University of Texas at Arlington, Arlington, TX 76019-0019, USA
3. Department of Computer Science, University of Nevada at Las Vegas, Las Vegas, NV 89154-4019, USA
4. Laboratoire HEUDIASYC, Université de Technologie de Campiègne BP 20529, 60205 Campiègne, France