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Soundings of the Ionospheric HF Radio Link Between Antarctica and Spain

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Soundings of the Ionospheric HF Radio Link Between Antarctica and Spain Thesis for the degree of Doctor of Philosophy Soundings of the ionospheric HF radio link between Antarctica and Spain Ahmed Gamal Ads Enginyeria i Arquitectura La Salle Electronics and Telecommunications Department Barcelona, October 2013 Soundings of the ionospheric HF radio link between Antarctica and Spain Ahmed Gamal Ads Research Group in Electromagnetism and Communications (GRECO) Enginyeria i Arquitectura La Salle Universitat Ramon Llull Quatre Camins, 30 08022 Barcelona, Spain E-mail: [email protected] Advisor: Joan Ramon Regu´eEnginyeria i Arquitectura La Salle, Universitat Ramon Llull, Barcelona, Spain. This work has been funded with grant number BES-2008-00948 by the FPI Scholarship from the ministry of Education and Science in the Spanish Government. This thesis has been prepared using LATEX. Abstract The HF electromagnetic waves with a frequency range from 2 MHz to 30 MHz can be reflected by means of the ionospheric layers for distances beyond 100 km. Even in some cases, they can reach the other side of the Earth. Along with the utilization of satellite communications, the ionosphere reserved its importance of being a very at- tractive transmission medium. The cost of the HF ionospheric transceiver is a way less expensive than using a satellite link. Also, it can be used for military and surveillances purposes overseas and in unapproachable lands. However, the main drawback of the HF ionospheric communications is that the characteristics of the transmission medium depend largely on parameters that are varying over time, such as the Smoother Sunspot Number (SSN), Solar Flux, hour of the day, season, etc. The Department of Electronics and Telecommunications at La Salle, Ramon Llull University has been cooperated with the Ebro Observatory in a scientific project called the Antarctica project. The main objective of this project is to connect the Spanish Antarctic Station Juan Carlos I (SAS) in Livingston, Antarctica and the Ebro Obser- vatory (OE) in Roquetes, Spain. That SAS-OE link has a length of 12700 km and it aimed to transmit measurements collected from geomagnetic and geophysics sensors located at the SAS towards the OE. The research work done in this thesis is part of this project. First, design and imple- mentation of the transmission platform called POTASIO using the Software Defined Radio (SDR) technique to perform the Oblique Incidence Sounding (OIS) of the SAS- OE ionospheric link is reviewed. All the updates that have taken place to the previous SDR platform (SODIO) are explained, including the components that raised the ac- curacy of both frequency and time synchronization between transmitter and receiver. The availability and the Frequency of Largest Availability (FLA) of the SAS-OE link has been obtained from the narrowband sounding technique throughout three consec- utive surveys from 2009 to 2012. Besides that, wideband sounding of the SAS-OE link has taken place to estimate the wideband Signal to Noise Ratio (SNR), the time dis- persion (composite multipath spread), frequency dispersion (composite Doppler spread and Doppler frequency shift), and the propagation time. Second, analyze the SAS-OE link availability, FLA, and the predicted Maximum Usable Frequency from the Rec533 model (MUFRec533) over the three surveys. Con- sequently, there has been an investigation of the day-to-day and inter-day varia- tions of various parameters (e.g., Total Electron Density (TEC), critical frequency of the F2 layer (foF2), and F2 layer Maximum Usable Frequency for ground dis- tance MUF(3000)) that have been measured at four Vertical Incidence Sounding (VIS) stations located over the SAS-OE link path throughout three consecutive surveys (2009/2010, 2010/2011, and 2011/2012). Finally, the correlation between the FLA of the SAS-OE ionospheric link and the MUF(3000) obtained from VIS stations located close to the reflection points of the same link has been studied. Therefore, the minimum propagated frequencies for the oblique SAS-OE link have been determined throughout the three survey. Keywords: Ionosphere, HF, communications, Oblique Incidence Sounding, Vertical Incidence Sounding, Ionospheric Channel Characterization. Acknowledgements My PhD is almost over but I can not finish it without looking back and thanking all the people that in one way or the other helped me to make it possible. It is not difficult to imagine that I would like to start by giving my deepest special thanks to Eman. For her infinite support, for being always there no matter how far I am and how long it takes me to come back, but specially for sharing all my dreams. Special thanks to my parents who always trusted me and encouraged me to go on. You know there are no words to thank you all you have done for me during the last 27 years. To my advisors Joan Llu´ısPijoan, Joan Ramon Regu´e,and Marc Deumal for be- lieving in me and for pushing me to go further and further. Thanks also for giving me always the freedom to draw new paths in our research activities. I am also very thankful to Juraj Gazda and Peter Drot´arfrom the Technical Univer- sity of Ko˘sice,Slovakia and Kaarti Salvan from the VIT, India for our joint cooperation. To all my colleagues from the Department of Telecommunications and Electronics, La Salle, Ramon Llull University, specially, Pau Bergad´a.And, thanks also to David Altadill from Ebro Observatory. My deepest thanks to my new family in Barcelona: Ahmed Helmi, Ahmed shokry, Ashraf Abdelfattah, and Eslam El Malkawy. This work has been funded by the Spanish Government under the projects CGL2006- 12437-C02-01, CTM2008-03536-E, CTM2009-13843-C02-02 and CTM2010-21312-C03- 03. The author has an FPI grant of BES-2008-00948 from the Spanish Government. vi Dedicated to Eman, Asia, Moaaz, and my family. vii Contents Abstract iv Acknowledgements vi List of Figures xiii List of Tables xix Abbreviations xxi Preface iii I Introduction3 1 The Ionosphere5 1.1 Introduction.................................5 1.2 The Sun...................................6 1.2.1 Smother sunspot number......................7 1.2.2 Disturbance Storm Time (Dst) index...............8 1.2.3 A- and K-index...........................9 1.2.4 Solar Flux.............................. 10 1.3 The structure of the ionosphere...................... 10 1.3.1 D Layer............................... 11 1.3.2 E Layer............................... 12 1.3.3 F Layer............................... 12 1.4 Solar disturbances and their effects on the ionosphere.......... 13 1.5 Ionospheric propagation.......................... 15 2 HF ionospheric communications 23 2.1 Introduction................................. 23 2.2 Ionospheric channel characterizations................... 24 2.2.1 Channel availability......................... 25 ix 2.2.2 Frequency dispersion........................ 25 2.2.3 Time dispersion........................... 26 2.2.4 Noise................................. 27 2.2.5 Interference............................. 28 2.3 Ionospheric channel study......................... 28 2.3.1 Modeling.............................. 29 2.3.1.1 Channel modeling.................... 29 2.3.1.2 Physical modeling.................... 30 2.3.2 Prediction.............................. 31 2.3.3 Sounding.............................. 32 2.3.3.1 Vertical Incidence Sounding............... 33 2.3.3.2 Oblique Incidence Sounding............... 35 2.3.4 Simulation.............................. 36 2.3.5 Noise and interference....................... 37 2.4 HF ionospheric modems.......................... 38 2.4.1 Automatic Link Establishment.................. 41 2.5 Applications................................. 42 3 An OIS system between Antarctica and Spain 47 3.1 Introduction................................. 47 3.2 Software defined radio ........................... 49 3.3 SAS-OE ionospheric link.......................... 50 3.4 The POTASIO platform.......................... 53 3.4.1 Introduction............................. 53 3.4.2 XTremeDSP-IV development board................ 59 3.4.3 The Cyanide board......................... 60 3.4.4 Hardware description of the transmitter............. 62 3.4.5 Hardware description of the receiver................ 66 II Contributions 71 4 Oblique sounding of the ionospheric HF radio link 73 4.1 Introduction................................. 73 4.2 Link description............................... 75 4.3 Wideband theoretical basics........................ 78 4.3.1 Characterizations of wideband channel.............. 80 4.3.2 Wideband sounding techniques.................. 84 4.3.2.1 Pulse compression techniques.............. 84 4.3.2.2 Periodic pulses sounding technique........... 88 4.4 Structure of the channel sounding..................... 88 4.5 Analysis algorithms of channel sounding................. 89 4.5.1 Algorithms of the narrowband sounding............. 90 4.5.1.1 First algorithm...................... 92 4.5.1.2 Second algorithm..................... 92 4.5.1.3 Third algorithm..................... 93 4.5.1.4 Fourth algorithm..................... 93 4.5.1.5 Windowing algorithm.................. 93 4.5.1.6 Time framing algorithm................. 97 4.5.2 Algorithms of the wideband sounding............... 100 4.6 Results.................................... 114 4.6.1 Narrowband sounding....................... 115 4.6.2 Wideband sounding......................... 119 4.6.2.1 Wideband SNR estimation................ 119 4.6.2.2 Composite multipath spread ............... 122 4.6.2.3 Composite Doppler spread ................ 127 4.6.3 Propagation Time.........................
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