DISI - University of Trento Energy-Efficient Medium Access Control Protocols and Network Coding in Green Wireless Networks

PhD Dissertation International Doctorate School in Information and Communication Technologies DISI - University of Trento Energy-Efficient Medium Access Control Protocols and Network Coding in Green Wireless Networks Raul Palacios-Trujillo Advisor: Prof. Fabrizio Granelli University of Trento December 2014 Abstract Wireless networks are a popular means of communications in daily social and business activities of many users nowadays. However, current estimates indicate that wireless networks are expected to significantly con- tribute to the rapidly increasing energy consumption and carbon emissions of the Information and Communication Technologies (ICT) sector. Crucial factors leading to this trend are the continuous growth of wireless network infrastructure coupled with the increased number of user wireless devices equipped with various radio interfaces and batteries of extremely limited capacity (e.g., smartphones). The serious problem of energy consumption in wireless networks is mainly related to the current standard designs of wireless technologies. These approaches are based on a stack of protocol layers aiming to maximize performance-related metrics, such as throughput or Quality of Service (QoS), while paying less attention to energy efficiency. Although the focus has shifted to energy efficiency recently, most of the existing wireless solutions achieve energy savings at the cost of some performance degradation. This thesis aims at contributing to the evolution of green wireless networks by exploring new approaches for energy saving at the Medium Access Con- trol (MAC) protocol layer and the combination of these with the integration of the Network Coding (NC) paradigm into the wireless network protocol stack for further energy savings. The main contributions of the thesis are divided into two main parts. The first part of the thesis is focused on the design and performance analysis and evaluation of novel energy-efficient distributed and centralized MAC protocols for Wireless Local Area Net- works (WLANs). The second part of the thesis turns the focus to the design and performance analysis and evaluation of new NC-aware energy- efficient MAC protocols for wireless ad hoc networks. The key idea of the proposed mechanisms is to enable multiple data exchanges (with or without NC data) among wireless devices and allow them to dynamically turn on and off their radio transceivers (i.e., duty cycling) during periods of no transmission and reception (i.e., when they are listening or overhearing). Validation through analysis, computer-based simulation, and experimenta- tion in real hardware shows that the proposed MAC solutions can significantly improve both the throughput and energy efficiency of wireless networks, compared to the existing mechanisms of the IEEE 802.11 Standard when alone or combined with the NC approach. Furthermore, the results presented in this dissertation help understand the impact of the on/off transitions of radio transceivers on the energy efficiency of MAC protocols based on duty cycling. These radio transitions are shown to be critical when the available time for sleeping is comparable to the duration of the on/off radio transitions. Keywords [Wireless network, energy efficiency, medium access control protocol, network coding, cross-layering] iv A mi familia. Para Susana. Acknowledgments This PhD dissertation would not have been possible without the help and support of many people. Herein, I would like to express my gratitude to all of them. First of all, I would like to thank Prof. Claudio Sacchi, Prof. Tommaso Pecorella, and Prof. Igor Bisio for accepting the invitation to be part of my PhD defense committee. I would also like to thank my advisor, Prof. Fabrizio Granelli, for his guidance during the last three years of the PhD degree and for giving me the opportunity to work and grow as a researcher at the University of Trento within the framework of the GREENET European research project. You have always been very kind with me and have always tried to provide me with all the materials and tools I needed to properly carry out my research. I feel that you have been far more than my mentor and, besides a great professor and researcher, I believe that you are a very nice person. I wish you all the best for the future and hope we can continue working together for many years. I would like to extend my gratitude to the GREENET project for sev- eral reasons. One is the financial support from the project through the University of Trento, which allowed me to purchase equipment to conduct top-notch research and attend the project meetings and many international conferences and workshops. Another reason is the top-level training I received from the project through very interesting and useful seminars organized by the partners of the project, exchange activities such as visits and secondments to other partners of the project, and the organization and participation to workshops and industrial dissemination days. Finally, the third reason is the multi-cultural and multi-disciplinary network of tal- ented young researchers and top-level research scientists from whom I have learned to be a better researcher and person and with whom I have spent many hours of work but also some of fun during the social dinners of the project meetings. More specifically related to the previous point, I would like to thank the GREENET coordinators, Prof. Luis Alonso Zarate, Dr. Christos Verik- oukis, and Melani Gurdiel Garcia, for managing such a fantastic project and making it by all of us together a success story. Also, I wish to acknowledge all the GREENET supervisors, Harald Haass, Marco di Renzo, Fabrizio Graziosi, Andreas Foglar, Hugo Marques, Jonathan Rodriguez, Gerrit Shulte, Kimon Kontovasilis, and Cristophe Gruet, for all their valu- able comments and suggestions regarding my research activities. A special thanks goes to Marco di Renzo, who was the president of my qualifying exam committee at the end of the first year of the PhD degree and gave me very interesting comments and ideas to complete this thesis. In addition, I would like to thank Andreas Foglar for organizing my secondment in his company, InnoRoute Gmbh, located in Munich (Germany) and for believing in me and my ideas to prepare and submit a patent. I would like to extend my gratitude to the rest of the InnoRoute team, Klaus Starnberger, Christian Liss, Tamas Fendler, Daniel Scharfen, Lorenzo di Gregorio, and Danica Gajic, with whom I felt very comfortable during the months I spent there. Related to my secondment, I also spent few weeks at CTTC to work with Francisco Vazquez Gallego for the implementation of my ideas on programmable wireless platforms. I would like to thank him for all his help and the lessons learned and I want to take this opportunity viii to express my special thanks to Dr. Verikoukis for authorizing me to have such a great experience at CTTC. I will never forget all the former and current GREENET researchers, Konstantinos Ntontin, Athanasios Stavridis, Xiping Wu, Danica Gajic, Saud Althunibat, Alexandra Bousia, Agapi Mesodiakaki, Vasileios Mili- otis, Riccardo Bassoli, Victor Sucasas, Eleni-Constantina Davri, Dereje Assefa, Xeonofon Foucas, Gergo Ertli, Pol Torres Compta, Marium Jalal Chaudhry, Sandeedp Narayanan, and Xavier Pons Masbernat, for the great moments we had together during these three years. Likewise, I cannot forget my main research collaborators during these three years: Jesus Alonso Zarate, Luis Alonso, Dzmitry Kliazovich, Janus Heide, and Frank H. P. Fitzek. I would like to thank you all for all your very useful comments and suggestions to improve our papers and my research in general. I look forward to continuing our fruitful collaboration in the future. The work presented in this thesis could not have been possible without the invaluable collaboration of some of my bachelor and master's students: Moatez Larbaa, Alessandro De Rossi, Habte Haile, Peter Nakeba, Francesco Franch, and Gedlu Mengistie. Thank you all for your valu- able contributions to some parts of the thesis. Also, I want to take this opportunity to thank Mbiika Ceriano (as a former master's student), Car- los Astudillo (as an exchange master's student), and my current master's students (Robel Endeshaw, Biniam Hailu, Habte Dechasa, and Mamun Rashid) for all what I have learned from you to become a better supervisor and person for the future. I must say that I have been very lucky to meet you all and wish you all the best for your future careers. Also, I wish to acknowledge the great work that all the staff of the DISI department at the University of Trento do, who have made possible that the development of this thesis has been a wonderful experience. My special ix gratitude goes to Mirella Collini, Andrea Stenico, and Manuel Zucchelini, who have always been available to help me whenever I have had a problem. My stay at the University of Trento has also left me very good friends, such as, Qi Wang, Le Dieu Thu, and Mai Anh Nguyen, among others. I thank you all for the time being together where we enjoyed multi-cultural dinners and had very interesting discussions about research, the PhD, and life in general. Also, I cannot forget to thank all my colleagues of "open space" from the DISI department with whom I have shared PhD courses, seminars, and talks. I would also like to thank my close friends, who, since the time they knew I was going to Trento to do research and pursue the PhD degree at the University of Trento, they have always been supporting me. As in every step forward in my life, I cannot forget that this achievement could not have been possible without the support of my family: my parents and my sister. You have always been there with me throughout all my life and thanks to your teachings and advice I have become the man who I am today.

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