Printed on acid-free paper Printed in Germany ISBN 978-3-8348-1398-5 Preface This thesis was written during my research as a doctorate candidate at the Communication Networks Group (ComNets) at the University of Bremen within TZI (Center for Computer Science and Information Technology). Throughout the years at ComNets I have always enjoyed the very inspiring, encouraging, deeply rewarding, and exceptionally collegial research atmosphere. To the greatest extent I would like to thank Prof. Dr. rer. nat. habil. Carmelita Görg for her supervising this thesis, for her guidance, and her encouragements. She has given me a lot of great advice and inspiring ideas, not only to my thesis but also to other scientific work. She has provided me an open and challenging research environment in the ComNets group, where it is a pleasure to conduct research and to take teaching responsibilities. Furthermore, she has given me a lot of opportunities to participate in national and international workshops and conferences, which helped me keep an open mind and view on the ongoing research fields that have inspired me in many ways for my research work. Besides, I am also deeply grateful for the comments and suggestions by Prof. Dr.-Ing. Ralf Lehnert, who has been my Professor during my master study at Dresden University of Technology and who also is the second examiner of this thesis. During the years of my master study, he gave me a lot of great advice and guidance on performing the scientific work as well as on many other technical aspects. I very much appreciate him for taking his valuable time to have discussions with me on my thesis. The discussions with him were of great help to me. In addition, I would like to thank Dr. Andreas Timm-Giel, who was always very open for discussions and has given me a great amount of valuable suggestions over the past years. I without a doubt greatly benefited from this, both in my research work and personally. His encouragements and advice have been a great support for me. Further thanks go to my col