1.2.
Contributions and Published Material
The research work presented in this thesis has been published and presented in several peer- reviewed journals and conferences. In detail, the related publications are six conference papers (in three of these I am the first author and in the other three the second author) [1, 23–27] and two journal articles (one as first author and one as second author) [2, 28]. As of writing these lines another journal paper (second author) is under submission, which extends the work presented in [1]. Parts of this work have been presented as two demos [29, 30], one invited talk [31] as well as several posters. Finally, during my PhD I contributed to one peer-reviewed conference paper [32], which is out of the scope of the current thesis and thus not discussed.
Research is a collaborative process and all of these works have been the result of the joint efforts of their authors. For completeness and in order to have everything presented in its proper context, in the following chapters, I present the work in a similar fashion as it was originally published, without highlighting or isolating my own contributions. The goal of this section is to present a summary of the above publications and clarify what was my contribution to each one. In order to comply with plagiarism rules, content from papers where I am not the first author is either presented as an appendix or shortened, paraphrased and the figures’ captions cite the original paper.
The main topic of this thesis is, as its title declares, “optimizing the delivery of multimedia over mobile networks”. In an attempt to make it a stand alone and cohesive work, only the most relevant parts of the published papers to its main topic are presented. Some work that I did during my PhD that is not discussed in this text includes measuring the performance accuracy over WiFi and speed and delay measurements of mobile networks.
I have studied in depth the arrival patterns of IP packets to mobile devices and analysed the possible artifacts that may distort their accurate observation. To do so, I gathered an extensive set of traces in a variety of conditions and countries, as well as generated vast simulation data. Then, I proposed two algorithms that may use arrival pattern information to passively estimate bandwidth, either by analysing the first few packets of a TCP flow, or by sampling a minimal portion of the traffic generated by bigger flows. Chapter 5 presents the measurement artifacts and Chapters 6 and 7 the two algorithms. Further, Chapter 2 is mostly original content created specifically for this thesis and acts as supplementary material to the peer reviewed work presented in the other three chapters. To the best of my knowledge, there is no other public resource that analyses the whole process of delivering a packet to a mobile phone as Chapter 2, does. The available resources are scattered, outdated or wrong and some parts of the process, like the baseband operation, have notoriously limited public documentation. Thus, it is a good starting point for anyone interested in learning about mobile communications. The related publications are:
Foivos Michelinakis, Nicola Bui, Guido Fioravantti, Joerg Widmer, Fabian Kaup, David Hausheer, “Lightweight Capacity Measurements For Mobile Networks”, in Com- puter Communications, 84. pp. 73-83, June 2016, ISSN 0140-3664.
8 Introduction
Foivos Michelinakis, Gunnar Kreitz, Riccardo Petrocco, Boxun Zhang, Joerg Wid- mer, “Passive Mobile Bandwidth Classification Using Short Lived TCP Connections” in The 8th IFIP Wireless and Mobile Networking Conference (WMNC 2015), 5-7 October 2015, Munich, Germany.
Foivos Michelinakis, Nicola Bui, Guido Fioravantti, Joerg Widmer, Fabian Kaup, David Hausheer, “Lightweight Mobile Bandwidth Availability Measurement”, in The 14th IFIP Networking 2015 Conference, 20-22 May 2015, Toulouse, France.
A crucial part of the above was validating that smartphones are capable of reporting accurately enough the timing of packet arrivals. Chapter 4 analyses how we assessed smartphone measure- ment accuracy. In this work, I created the experiment logic and performed the experiments, as well as analyse the gathered data. I also performed experiments regarding the accuracy of mea- surements over the WiFi interface, which are not discussed in this thesis. The related publication, an extension of which is under submission to the “Pervasive and Mobile Computing” Journal, is: Nicola Bui,Foivos Michelinakis, Joerg Widmer, “Fine-grained LTE Radio Link Es- timation for Mobile Phones”, in The 18th International Symposium on a World of Wireless Mobile and Multimedia Networks (WoWMoM 2017), 12-15 June 2017, Macau, China. In collaboration with researchers from TU Darmstadt I contributed to two works evaluating the QoS of mobile networks based on crowd sourced data. I worked on gathering traces from Spanish operators and analysing the dataset. Parts of this work are presented in Section 8.6. The related publications are:
Fabian Kaup, Foivos Michelinakis, Nicola Bui, Joerg Widmer, Katarzyna Wac, David Hausheer, “Assessing the Implications of Cellular Network Performance on Mo- bile Content Access”, in IEEE Transactions on Network and Service Management, 13 (2). pp. 168-180, March 2016, ISSN 1932-4537.
Fabian Kaup, Foivos Michelinakis, Nicola Bui, Joerg Widmer, Katarzyna Wac, David Hausheer, “Behind the NAT – A Measurement Based Evaluation of Cellular Ser- vice Quality”, in The 11th International Conference on Network and Service Management (CNSM 2015), 9–13 November 2015, Barcelona, Spain.
I performed extensive measurements and analysis of the performance of third-party services over twelve dominant European network operators, using the MONROE experiment testbed. This work is discussed in Chapter 8 and the related publication is:
Foivos Michelinakis, Hossein Doroud, Abbas Razaghpanah, Andra Lutu, Narseo Vallina-Rodriguez, Phillipa Gill, Joerg Widmer, “The Cloud that Runs the Mobile Internet: A Measurement Study of Mobile Cloud Services”, in The 37th IEEE International Confer- ence on Computer Communications (IEEE INFOCOM 2018), 15-19 April 2018, Honolulu, HI, USA.