Investigations in Bandpass Sampling for Wireless Communications and Software Defined Radio Milan Patel A thesis submitted for the degree of Doctor of Philosophy September 2004 Department of Electronic and Electrical Engineering University College London ProQuest Number: U642596 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest U642596 Published by ProQuest LLC(2015). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Abstract This thesis presents modelling, limitations and simulation based performance assessment of bandpass sampling receivers. An overview of software radio and fourth generation wireless systems is presented, as well as theoretical and practical aspects of bandpass sampling for such systems. An investigation to determine the effects of various front-end bandpass filters on the BER performance of a bandpass sampling receiver in noise and adjacent channel interference is undertaken, since this filtering process is essential to bandpass sampling. Both narrowband and wideband front-end implementations are considered. The research concludes that great care has to be taken when choosing the receive filters in accordance with specific system parameters. Consideration of aperture jitter becomes increasingly important when sampling at IF and RF and its effect is regarded as an amplitude error on the sampled signal. The hypothesis that oversampling improves system performance is tested by developing analytical expressions verified by computer simulation. Results indicate that oversampling causes performance degradation due to jitter effects. The effect of aperture jitter on the performance of multicarrier bandpass sampling receivers is investigated, using OFDM. The effect of aperture jitter is assessed via BER measurements and by varying a number of key system parameters. Results indicate that aperture jitter causes a random frequency deviation in the centre frequency of the sampled signal, thus resulting in ICI and loss of orthogonality between subcarriers. The performance of a multimode bandpass sampling receiver for the simultaneous reception of an OFDM and a single carrier signal is investigated by varying system parameters. For optimum BER performance it is necessary to examine carefully the interactions between the signals and their spectral copies that occur due to the sampling process. Finally, design trade-offs are identified for receiver architecture simplicity and BER performance. Overall, the thesis addresses different design and optimisation issues of bandpass sampling for the use in future software radio receivers. Acknowledgements I would like to express my sincere thanks to Dr. Izzat Darwazeh for supervising this research from October 2001 up until the completion of this thesis. His encouragement, motivation, friendship and entertaining conversations have been invaluable to the success of this work. I would like to thank my former supervisors. Professor Phil Lane and Professor John O’Reilly and also my second supervisor. Dr. John Mitchell, for their valuable support and input into the research in this thesis, especially at the initial stages of the work. The support of the computer systems support staff is also greatly appreciated. In addition, I would like to thank my colleagues, past and present, in the Department of Electronic and Electrical Engineering at UCL for their support, assistance and for making my postgraduate studies enjoyable. I am extremely grateful to my friends for their support. Thank you all for being patient and for all the encouragement and great times over the many years. I’d like to thank sincerely my girlfriend, Hardika, for her love, invaluable support and patience and especially for helping me stay positive and in high spirits. I would like to express my sincere gratitude to my dear parents for their constant and loving support throughout my education and postgraduate studies. Their encouragement is no doubt a fundamental factor in my success thus far. My deepest gratitude and respect is expressed towards my late grandfather for being a positive role model throughout my life. I would also like to thank my brother, Sanjay, for his support and wish him every success in the completion of his PhD. Finally, I would like to thank the EPSRC for their financial backing and the Royal Academy of Engineering for their assistance in funding towards attending conferences where some of this work was presented. Additional financial support from my department at UCL is also gratefully acknowledged. Contents ABSTRACT......................................................................................................................................................2 ACKNOWLEDGEMENTS...........................................................................................................................3 CONTENTS......................................................................................................................................................4 LIST OF FIGURES.................................................... 7 LIST OF ABBREVIATIONS......................................................................................................................11 CHAPTER 1 INTRODUCTION.........................................................................................................14 1.1 T hesis Str u c tu r e ....................................................................................................................................... 15 1.2 C ontributions ............................................................................................................................................. 18 CHAPTER 2 SOFTWARE RADIO AND FOURTH GENERATION WIRELESS COMMUNICATIONS................................................................................................................................. 20 2.1 Introduction .............................................................................................................................................20 2.2 Softw a re R a d io ......................................................................................................................................... 21 2.2.1 The Future o f Software Radio .............................................................................................................. 23 2.3 T echnical C h a l l e n g e s ...........................................................................................................................24 2.3.1 RF-Front End ............................................................................................................................................24 2.3.2 ADC Issues.................................................................................................................................................27 2.4 So ftw a re R adio P r o je c t s ..................................................................................................................... 31 2.4.1 Overview of the SPEAKeasy - Military Software Radio Program ........................................... 31 2.4.2 SDR Forum .............................................................................................................................................33 2.4.3 IST-TRUST..............................................................................................................................................34 2.5 O th er A spects o f Reconfigurable R a d io .....................................................................................34 2.5.1 Reconfigurable Baseband ..................................................................................................................... 35 2.5.2 Software Download. ................................................................................................................................ 36 2.5.3 Security.......................................................................................................................................................39 2.6 F ourth G e n er a tio n ..................................................................................................................................41 2.6.1 Introduction .............................................................................................................................................41 2.6.2 4G-Anytime, Anywhere........................................................................................................................41 2.6.3 User Expectations ....................................................................................................................................43 2.6.4 Reconfigurability......................................................................................................................................44 2.6.5 Flexible Frequency Allocation.............................................................................................................45 2.7 C o m m on R eceiv er A rchitectures ....................................................................................................46