POLITECNICO DI MILANO Facolt`adi Ingegneria Industriale Laurea Magistrale in Ingegneria Spaziale Wireless technology for space applications: effects of Antenna Diversity radio transceiver selection Relatore: Prof. Mich`eleLAVAGNA Co-relatore: Ing. Jean-Fran¸coisDUFOUR Tesi di Laurea di: Vincenzo TAUMATURGO Matr. 735141 Anno Accademico 2010-2011 Sed omnia praeclara tam difficilia, quam rara sunt (Baruch Spinoza) Abstract The impact of the harness on a spacecraft mass budget can be around 5% of the total dry mass, moreover it leads to a further complexity in the design phase to think about an appropriate path for electric cables and data wired and to longer time spent for Assembly, Integration and Testing (AIT) activi- ties. An alternative is offered by wireless technologies, developed for commer- cial usage in the latest 1990s and introduced in the space application technol- ogy development since few years only. Moreover always more Commercial- Off-The-Shelf components satisfy the aerospace applications strict require- ments and they have been successfully used both in testing activities than in critical in-flight operations, however not a big amount of data is actually available about the behavior of these components under when exposed to radiation, even if this is one of the main requirements of a space applica- tion. In this thesis I evaluated the performances of a wireless IEEE 802.15.4 compliant radiotransceiver, designing a test sequence which aims to evalu- ate the possibility to use this component in an AIT activity, for instance as the communication block of a temperature sensor network. I tested the radiotransceiver in several scenarios representative for a space oriented ap- plication, like the Venus-Express mock-up. In particular the benefit of the Antenna Diversity mechanism is evaluated to assess its benefit on the link budget in multipath affected scenarios, as like as a metallic closed structure divided in cavities. Then I performed a Total Ionizing Dose test, evalu- ating the behavior of the device in terms of electrical and communication parameters. Then a practical example of a space oriented application of the tested device is provided, through the implementation of a wireless smart temperature sensor. Keywords: wireless, Antenna Diversity, Commercial-off-the-shelf, smart sensor, IEEE 802.15.4. Sommario L'impatto dei cablaggi sul mass budget di un veicolo spaziale rappresen- ta circa il 5% della massa totale (carburante escluso). Inoltre porta a non poche complessit`asia in fase di progetto, nel prevedere opportuni percorsi per i cavi che rispettino i requisiti di compatibilit`aelettromagnetica, sia in fase di assemblaggio, integrazione e test, a causa dei chilometri di cavi im- piegati per sensori e apparati, da posare e verificare ad ogni utilizzo. Una valida alternativa `erappresentata dalla tecnologia wireless, nata nel mondo commerciale nella seconda met`adegli anni '90 e da qualche anno utilizzata per lo sviluppo di tecnologie in campo aerospaziale. Inoltre i severi requisi- ti delle applicazioni spaziali vengono spesso soddisfatti oggigiorno da com- ponenti commerciali, utilizzati sia per attivit`adi test non critiche, sia per applicazioni in volo. In questa tesi ho valutato le prestazioni di un radio- trasmettitore che segue lo standard IEEE 802.15.4, progettando una serie di test per valutare la possibilit`adi impiegare questo componente nell'ambito di un’attivit`adi integrazione e test, ad esempio come il terminale di un rete di sensori di temperatura. Ho testato il radiotrasmettitore in situazioni rappre- sentative di una applicazione orientata all'utilizzo in ambito aerospaziale, ad esempio all'interno della struttura principale del satellite Venus-Express. In particolare ho valutato il guadagno sul link budget garantito dal meccanis- mo di Antenna Diversity, per contrastare l’effetto del cosiddetto multipath fading, fortemente presente in ambienti caratterizzati da numerose rifles- sioni, come la struttura metallica del satellite, suddivisa in cavit`a. Inoltre ho effettuato un test di esposizione a radiazioni, valutando il comportamento del componente durante e dopo l'esposizione, in termini di quantit`aelet- triche e di parametri di comunicazione. Infine presento un esempio pratico di applicazione spaziale per questo componente: un sensore intelligente di temperatura, wireless e alimentato da una piccola batteria. Parole chiave: wireless, Antenna Diversity, componente commerciale, sen- sore intelligente, IEEE 802.15.4. Acknowledgements I would like to express my gratitude to those people which made me able to write this thesis with their moral support and their valuable contribution, also giving me the possibility to complete my studies doing a very instructive experience at the European Space Research and Technology Centre. I'm grateful to Professor Mich`eleand to my external supervisor, Jean-Fran¸cois Dufour, for their patience and availability, then I thank Giorgio Magistrati, Head of On-Board Computers & Data Handling section and all the TEC- EDD section members because they enabled me to work in the best possible conditions. Thanks to Maria, Farid, Gianluca, Max and Marco for the time they always found for me and I have to thank also Alberto, Javier, Michele, Alfonso and all the people who have been more than work mates for me. Then I can't forget who supported and encouraged me throughout my life and especially during these last five years: my Mother and my Sister, who stood by me even though I was annoying and obnoxious because I was under stress and my girlfriend who treated my kindly even if I had my head in the clouds. In the end I would like to thank my \brothers in arms" Fulvio, Davide, Marzio, Gi`o,Edo, Alex, Ste, Debby and Stefania who shared with me a lot of troubles and who helped me to ride over and to appreciate finally all the challenges handled with excitement and strength of will at the University. I II Contents Acknowledgements I List of Figures VII List of Tables XI 1 Introduction 1 2 Basic networks and communication theory 11 2.1 RF Propagation . 11 2.1.1 Multipath fading . 12 2.1.2 Multi-mode cavity theory . 14 2.1.3 Antenna diversity . 16 2.2 Node Topologies . 17 2.3 Network Topologies . 18 2.4 Communication System Models . 19 2.4.1 OSI Model . 20 2.5 IEEE 802.15.4 . 22 2.5.1 Supported devices . 24 2.5.2 Supported networks . 24 2.5.3 Layers Features . 24 3 GP500C device 33 3.1 Power consumption . 35 3.2 Event Scheduling . 36 3.3 Hardware integrated MAC layer . 37 3.4 Antenna Diversity . 38 3.5 Packet-in-Packet resynchronisation . 38 III 4 Test sequence 39 4.1 Test sequence tasks and purposes . 39 4.2 Functional Test . 41 4.2.1 Description . 41 4.2.2 Setup . 42 4.2.3 Test . 42 4.2.4 Software Development . 42 4.3 Physical parameters Test . 52 4.3.1 Description . 52 4.3.2 Setup . 53 4.3.3 Test . 53 4.4 Communication parameters test . 54 4.4.1 Description . 54 4.4.2 Setup . 57 4.4.3 Test . 58 4.5 V-Ex test . 59 4.5.1 Description . 59 4.5.2 Setup . 62 4.5.3 Test . 63 4.6 Radiation Test . 64 4.6.1 Description . 64 4.6.2 Setup . 66 4.6.3 Test . 67 5 Results 69 5.1 Functional Test . 69 5.2 Physical Parameters Test . 71 5.3 Communication parameters test . 72 5.4 V-Ex Mockup Test . 84 5.5 Radiation test . 102 6 Temperature sensor example design 111 6.1 Temperature sensor . 112 6.2 Amplification stage . 115 6.3 Micro-controller . 115 6.4 SPI interface . 116 6.5 Radio transceiver and Antenna . 117 6.6 Power supply . 117 7 Conclusions 121 Appendices 125 A Test environments 125 A.1 Avionics Laboratory . 125 A.2 Anechoic chamber . 126 A.3 Co-60 facility . 127 A.4 V-Ex mock-up . 129 Nomenclature 131 Bibliography 133 List of Figures 2.1 Network topologies . 19 2.2 OSI model . 20 2.3 PPDU and Data MPDU format . 27 2.4 MPDU general format . 29 3.1 GP500C vs traditional system block scheme . 34 3.2 GP500C SPI module device . 34 4.1 802.15.4 devices joining sequence . 43 4.2 802.15.4 devices data exchange sequence . 43 4.3 Front panel of a developed LabView software . 49 4.4 Block diagram of a developed LabView software . 51 4.5 SNR(LQI,RSSI) 3D curve . 55 4.6 SNR(LQI,RSSI) curves . 55 4.7 Gain and penalty definition . 61 4.8 Cavities and devices position inside them . 62 4.9 PER confidence level curves . 65 4.10 Radiation test setup . 66 5.1 Remote control answer packet . 69 5.2 Avionics Lab packet logging . 70 5.3 Radiation test, right received packet . 70 5.4 Radiation test, wrong received packet . 70 5.5 16 MHz crystal output . 71 5.6 RSSI vs distance, horizontal polarization . 72 5.7 LQI vs distance, horizontal polarization . 73 5.8 RSSI vs distance, vertical polarization, emitter antenna 0 . 73 5.9 LQI vs distance, vertical polarization, emitter antenna 0 . 73 5.10 RSSI vs distance, vertical polarization, emitter antenna 1 . 74 5.11 LQI vs distance, vertical polarization, emitter antenna 1 . 74 VII 5.12 RSSI vs distance, horizontal polarization . 75 5.13 LQI vs distance, horizontal polarization . 75 5.14 RSSI vs distance, vertical polarization, emitter antenna 0 . 76 5.15 LQI vs distance, vertical polarization, emitter antenna 0 . 76 5.16 RSSI vs distance, vertical polarization, emitter antenna 1 . 76 5.17 LQI vs distance, vertical polarization, emitter antenna 1 . 77 5.18 ED scan results for all the channels . 78 5.19 Effect of the noise on the exchanged packets RSSI .