A Thesis Submitted for the Degree of PhD at the University of Warwick Permanent WRAP URL: http://wrap.warwick.ac.uk/117170 Copyright and reuse: This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications Terahertz Communications at the Nanoscale by Zhichao Rong Thesis Submitted to the University of Warwick for the degree of Doctor of Philosophy School of Engineering October 2017 Contents List of Figures ............................................................................................................. v List of Tables ............................................................................................................. ix Acknowledgements ..................................................................................................... x Declaration ………………………………………………………………………...xi List of Publications ................................................................................................... xii Abstract …………......……………………………………………………..….xiii Nomenclature........................................................................................................... xiv List of Symbols ........................................................................................................ xvi Introduction ...................................................................................... 1 1.1 Background ................................................................................................... 1 1.2 Communication Paradigms among Nanosensors .......................................... 3 Molecular Communications ................................................................... 4 Electromagnetic Communications ......................................................... 6 1.3 Architecture of Nanonetworks and Applications ........................................ 10 Internet of Nano-things ........................................................................ 10 Biomedical Applications ...................................................................... 12 Environmental Monitoring ................................................................... 13 1.4 Challenges Toward THz Nanonetworks Analysis ...................................... 15 1.5 Motivations .................................................................................................. 15 1.6 Objectives .................................................................................................... 16 1.7 Thesis Contributions .................................................................................... 17 1.8 Thesis Outline .............................................................................................. 18 ii Terahertz Communication Channel Model for Nanonetworks .. 21 2.1 Introduction ................................................................................................. 22 2.2 Graphene-based Nanoantenna ..................................................................... 23 2.3 Related Work ............................................................................................... 24 2.4 Channel Modelling of EM Propagation in the THz Band ........................... 31 Free Space Spreading Loss .................................................................. 32 Absorption Loss ................................................................................... 33 Wave Propagation ................................................................................ 35 Absorption Noise ................................................................................. 36 Channel Capacity ................................................................................. 37 2.5 Conclusions ................................................................................................. 42 Relay-Assisted Nanoscale Communication in the Terahertz Band .............................................................................................................. 44 3.1 Introduction and related work ..................................................................... 44 3.2 THz Propagation Channel Model ................................................................ 46 3.3 System Model .............................................................................................. 47 AF Relaying Protocol ........................................................................... 48 DF Relaying ......................................................................................... 55 3.4 Numerical results ......................................................................................... 57 3.5 Conclusions ................................................................................................. 63 Energy Harvesting for Body-Centric Nanonetworks in the THz Band Based on Nano-Rectennas ....................................................... 65 4.1 Motivations and Related Work .................................................................... 66 Body-Centric Nanonetworks ................................................................ 67 Piezoelectric Nanogenerator ................................................................ 69 Nano rectenna Systems ........................................................................ 70 4.2 State of Art of Rectennas ............................................................................. 72 Review of Rectennas ............................................................................ 72 Operation Principle of Rectennas......................................................... 74 iii Ultrafast Diodes for THz rectennas ..................................................... 76 4.3 Nanosensor Energy Harvesting ................................................................... 79 4.4 Performance Analysis and Comparisons ..................................................... 84 4.5 Conclusions ................................................................................................. 92 Simultaneous Wireless Information and Power Transfer for AF Relaying Nanonetworks in the Terahertz Band .............................. 94 5.1 Introduction and related works .................................................................... 95 5.2 Channel Model ............................................................................................ 99 5.3 System Model ............................................................................................ 100 Time Switching .................................................................................. 103 Power Splitting ............................................................................... 108 5.4 Comparison of results and discussion ....................................................... 112 5.5 Conclusions ............................................................................................... 117 Rate-Energy Trade-off Analysis of SWIPT System in the THz Band ............................................................................................................ 119 6.1 Introduction ............................................................................................... 119 6.2 System Model ............................................................................................ 120 The channel splitting protocol ............................................................ 122 Adaptive power allocation ................................................................. 125 6.3 Numerical results ....................................................................................... 129 6.4 Conclusions ............................................................................................... 132 Conclusions and Future Work ……………………………...134 7.1 Future work ............................................................................................... 137 Bibliography ........................................................................................................... 140 iv List of Figures Figure 1-1 The architecture of a biological cell as a nanosensor device (adapted from [23] ). ........................................................................................................................... 6 Figure 1-2 A conceptual architecture of an EM-based nanosensor device .................. 7 Figure 1-3 THz Band (0.1-10 THz) in the EM spectrum. .......................................... 10 Figure 1-4 The Conceptual Architecture of the Internet of Nano Things .................. 11 Figure 1-5 The Conceptual Architecture of the Internet of Bio-Nano Things [23]. .. 12 Figure 1-6 Wireless Nanonetworks for Healthcare Monitoring ................................ 13 Figure 1-7 Structure of a nanonetwork as the application of plant monitoring [63]. 14 Figure 2-1 The Free-Space Spreading Loss for a signal travels in the THz channel for a propagation distance of 0.01 m. .............................................................................. 32 Figure 2-2 Molecular absorption coefficient for water vapour as the function of the frequency [64]. ........................................................................................................... 35 Figure 2-3 Dividing the entire band into small sub-bands ........................................