Efficient Spectrum Utilization of UHF Broadcast Band LEI SHI Doctoral Thesis in Information and Communication Technology Stockholm, Sweden, 2014 TRITA-ICT-COS-1406 KTH Communication Systems ISSN 1653–6347 SE-100 44 Stockholm ISRN KTH/COS-14/06-SE Sweden Akademisk avhandling som med tillstånd av Kungl Tekniska högskolan framlägges till of- fentlig granskning för avläggande av teknologie doktorsexamen i telekommunikation tors- dagen den 12 June 2014 klockan 14.00 i Room E, Forum, Kungliga Tekniska Högskolan, Isafjordsgatan 26, Kista. © Lei Shi, June 2014 Tryck: Universitetsservice US AB i Abstract The UHF band between 470-790 MHz, currently occupied by digital ter- restrial TV (DTT) distribution in Europe, is widely regarded as a premium spectrum band for providing mobile coverage. With the exponential increase in wireless data traffic in recent years, there has been growing interests in gaining access to this spectrum band for wireless broadband services. The secondary access in TV White Space is considered as one cost-effective way to reuse the spectrum unoccupied by the primary DTT network. On the other hand, the declining influence of DTT and the converging trends of video con- sumption on TV and mobile platforms are new incentives for the regulator to reconsider the optimal utilization of the UHF broadcast band. The proposal to re-farm the UHF band for a converged content distribution network was born under theses circumstances. This thesis intends to develop a methodology for evaluating the technical performance of these options for utilizing UHF broadcast band and quantify- ing their gains in terms of achievable extra capacity and spectrum savings. For the secondary access in TV white space, our study indicates a considerable po- tential for low power secondary, which is mostly limited by the adjacent chan- nel interference generated from the densely deployed secondary devices due to the cumulative effect of multichannel interference. On the other hand, this potential does not translate directly into capacity for a WiFi-like secondary system based on CSMA/CA protocol, as the network congestion and self- interference within the secondary system has a greater impact on the network throughput than the primary interference constraint. Our study on the cellular content distribution network reveals more po- tential benefits for re-farming the UHF broadcast band and reallocating it for a converged platform. This platform is based on cellular infrastructure and can provide TV service with the same level of quality requirement as DTT by delivering the video content via either broadcast or unicast as the situa- tion dictates. We have developed a resource manage framework to minimize its spectrum requirement for providing TV service and identified a significant amount of spectrum that can be reused by the converged platform to provide extra mobile broadband capacity in urban and sparsely populated rural areas. Overall, we have arrived at the conclusion that the concept of cellular con- tent distribution in a re-farmed UHF band shows a more promising prospect than the secondary access in TV white space in the long run. Nevertheless, low power secondary is still considered as a flexible and low-cost way to exploit the underutilized spectrum in the short term, despite its uncertainty in future availability. On the other hand, the re-farming of UHF broadcast band is a long and difficult regulation process with substantial opposition from the in- cumbent.The results from this study could serve as input for future regulatory decisions on the UHF band allocation and cost-benefit analysis for deploying new systems to access this spectrum band. Acknowledgements Along the journey towards making this PhD thesis during the last four and a half years, there is no lack of occasions of feeling stressed and confused. But looking back from today, I would say, without regrets, it has been a truly unforgettable and rewarding experience, thanks to the encouragement, support and friendship from the people in this environment. Therefore, I would like to take the opportunity here to express my sincere gratitude to these special people. First of all, I am most grateful to my main supervisor, Prof. Jens Zander, who has offered me the extraordinary opportunity to pursue the doctoral study here. His critical and visionary thinking has always inspired me the most and taught me to live with and even enjoy the uncertainties in both research and the life ahead. I am also very thankful for his trust and support, especially for my application to the EIT ICT doctoral program, which may turn out into another wonderful journey into the ’uncertainties’. I am also deeply in debt to Docent Ki Won Sung, my co-advisor, with whom I have enjoyed working closely in most of the projects and publica- tions during my PhD study. He has always been extremely patient in giv- ing me invaluable advices and feedbacks in our countless discussions. And I have learned a great deal from his expertise and knowledge that he has always shared without any reservation. I greatly appreciate Docent Svante Signell, for his time spent in reviewing my Licentiate thesis. I owe special thanks to Dr. Tim Irnich, for accepting the role of opponent for my Licentiate thesis defense. I would like to thank Lasse Wieweg for reviewing my PhD thesis proposal and Prof. Mats Bengtsson for his valuable comments during the evaluation of this thesis. My special thanks to Prof. Linda Doyle for accepting to be my opponent in the Doctoral dissertation. I am also grateful to the members of the grading committee: Dr. Joachim Sachs, Prof. Tommy Svensson and Prof. Mikael Sköglund. I consider myself lucky and privileged to have met and worked together with many talented people in different research projects. I am especially thankful to Evanny Obregon and Javier Ferrer: the time we spent working together has been a fun and fruitful year at the beginning of the PhD. I would also like to say thanks to all of you who made the Radio Communication ii iii System group such a unique and friendly environment: Ali Özyagci, Sibel Tombaz, Serveh Shalmashi, Du Ho Kang, Luis Martinez, Miurel Tercero, Yan- peng Yang, Haris Celik, Amirhossein Ghanbari, Anders Laya, Ashraf Widaa, Vlad-Ioan Bratu, Dr. Sang-Wook Han, Prof. Jan Markendahl, Prof. Ben Sli- mane, Prof. Claes Beckman, Prof. Guowang Miao, Dr. Luca Stabellini, Göran Andersson, Anders Västberg and many more. I am also grateful to Sarah Winther, Jenny Minnema, Gunilla Gabrielsson and Lissi Perseus for their excellent administrative support. My special thanks goes to Irina Radulescu and Dr. Bogdan Timus, not only for their help even before I started my PhD but also for their genuine friendship. It is just impossible to describe how grateful I am for my parents, Rudong Shi and Ling Yang. Your unconditional love has always been the pillar for me to lean on. I am also extremely grateful to my wife, Molan, for coping with my fluctuating stress level during all these years. But you have not only helped me to get through the difficult times with your encouragements and patience, but also created the space where I can live a balanced and healthy life. Finally, I would like to dedicate this thesis to my family: without your support and understanding, I would never reach this far. Contents Preface ii Contents iv List of Figures vi List of Abbreviations viii I1 1 Introduction 2 1.1 Background . 2 1.2 Spectrum Access in UHF Band . 6 1.3 Previous Work . 9 1.4 Problem Formulation . 13 1.5 Thesis Contributions and Outline . 16 2 Research Methodology 20 2.1 Methodology for Analyzing the Spectrum Opportunity for Secondary Access in TV White Space . 21 2.2 Methodology for Evaluating the Spectrum Saving by Cellular TV Distribution . 26 3 Secondary Access in TV White Space 30 3.1 Interference Modeling . 30 3.2 Protection of Primary System . 31 3.3 Spectrum Opportunity and Secondary Capacity . 34 4 Cellular Content Distribution Network in a Re-farmed UHF Band 39 4.1 Feasibility Analysis . 39 4.2 CellTV Deployment in Inhomogeneous Environments . 41 5 Discussion 45 iv CONTENTS v 5.1 Benefits . 45 5.2 Challenges . 46 5.3 Summary . 48 6 Conclusions and Future Work 49 6.1 Concluding Remarks . 49 6.2 Future Work . 51 Bibliography 52 II Paper Reprints 58 7 Experimental Verification of Indoor TV White Space Opportu- nity Prediction Model (P1) 60 8 A Model for Aggregate Adjacent Channel Interference in TV White Space (P2) 67 9 Permissible Transmit Power for Secondary User in TV White Space (P3) 74 10 Controlling Aggregate Interference under Adjacent Channel In- terference Constraint in TV White Space (P4) 81 11 Secondary Spectrum Access in TV Bands with Combined Co- Channel and Adjacent Channel Interference Constraint (P5) 89 12 On the Capacity of Wi-Fi System in TV White Space with Ag- gregate Interference Constraint (P6) 100 13 CellTV - on the Benefit of TV Distribution over Cellular Net- works A Case Study (P7) 108 14 Opportunities and challenges for TV and Mobile broadband in 470-790 MHz (P8) 122 15 Spectrum Requirement for Cellular TV distribution in UHF Band from Urban to Rural Environment (P9) 141 16 Cellular TV Distribution in Heterogeneous Environments (P10) 147 List of Figures 1.1 Spectrum allocation in the UHF broadcast band [1] [2] . 3 1.2 TV consumption share on different platforms (%) [3]. 3 1.3 Wireless data traffic growth forecast (Exabytes per month) [4]. 4 1.4 Secondary Access in TV White Space. 6 1.5 Cellular content distribution network. 8 1.6 Summary of related literature in TV white space. 10 1.7 The correlation of the investigated scenarios. 13 2.1 Overall research approach of the thesis.