1. a University of Poitiers & CNRS (CeRCA UMR 6234) – 99, ave du Recteur Pineau , F-86000, Poitiers, France
2. b University of Toulouse II & CNRS (CLLE-LTC UMR 5263) – MDR , 5 allées A. Machado, F-31058 Toulouse Cedex 9, France
3. c University of Rennes II (CRPCC) – 6, ave Gaston Berger , F-25043, Rennes Cedex, France
4. d Orange Labs France Telecom – 2, ave Pierre Marzin , F-22700, Lannion, France