Today we are approaching a truly connected and wireless world where users can be always connected by switching between different carriers and providers.

At first, God bless us all. I would like to thank my advisor, Jean-Yves Tigli for his guidance, support and encouragement during the preparation of this dissertation and articles. Words cannot express my appreciation and deepest gratitude to my father, my mother and my brother for their love and emotional support. Thanks to all my family. My special thanks to Diane Lingrand for her support and for the articles. I want to express my gratitude to my friends from Brazil and to my new friends here in France to the moral support. I would like also to thank Celio Trois for his friendship. Finally, thank for all people involved during the academic year. "If the future's looking dark We're the ones who have to shine If there's no one in control