ACQUISITION SCHEMES FOR BURST MODE DIRECT SEQUENCE SPREAD SPECTRUM PACKET RADIO Desmond Wai Ming Yan B.A.Sc. Simon Fraser University, 1992 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTEROF APPLIEDSCIENCE in the School of Engineering Science @ Desmond Wai Ming Yan 1994 SIMON FRASER UNIVERSITY September 1994 All rights i.eserved. This work may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author. APPROVAL Name: Desmond Wai Ming Yan Degree: Master of Applied Science Title of thesis : Acquisition Schemes for Burst Mode Direct Sequence Spread Spectrum Packet Radio ,A. J. Cavers Direrctor, School of Engineering Sci- ence, SFU Examining Committee: Dr. P. Ho Associate Professor, Engineering Sci- ence, SFU Senior Supervisor Gcavers Professor, Engineering Science, SFU Internal Supervisor - - Dr. J. Vaisey Assistant Professor, Engineering Sci- ence, SFU Examiner Date Approved: September 21, 1994 PARTIAL COPYRIGHT LICENSE I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission. Title of Thesis/Project/Extended Essay "Acauisition Schemes for Burst Mode Direct Seauence Spread Spectrum Packet Radio" Author: Desmond YAN (name) August 24.1994 (date) Abstract Code Division Multiple Access (CDMA) is a promising technology for future digital cellular and personal communicatio~~s.Some of the nice features in CDMA include (1) anti-multipath, (2) higher system capacity than TDMA and FDMA, and (3) its flexibility in providing bandwidth on demand. To despread the pseudo noise (PN) code and thus understand the message sent, PN code synchronization is necessary a priori. As a matter of fact, the throughput of a packet mode CDMA system is directly related to the performance of its synchro~lizationalgorithm. PN code synchronization is usually performed in two stages: acquisition and tracking. The former aims to find a coarse alignment between the incoming signal and the local PN code replica, while the latter fine adjusts the phase. In this thesis, we will consider the PN code acquisition problem. Particularly, we propose two new acquisition algorithms: the On-Off Keying Assisted Acquisition Scheme and the Differentially Encoded Barker Sequence Acquisition Scheme. The preamble in the first method follows an on-off pattern and the algorithm performs a Markov search. The second method, on the other hand, uses DPSK to encode a Barker sequence as the preamble. The algorithm looks for the Barker sequence to declare acquisition. We have also introduced a windowing technique in both methods which we found effective in overcoming the partial correlation effect. The two proposed schexnes are compared with some existing ones in the literature like the coincidence detector or simple Markov search, and we find that our algorithms outperform the others both under AWGN and frequency selective fading channels. Acknowledgements I would like to thank my supervisor, Dr. Paul Ho, for his guidance throughout my study, and also Dr. J. Cavers for his invaluable ideas. Besides, I would like to thank Dr. J. Vaisey who have spent his precious time in reading and revising my thesis. Last, I would like to thank Dr. J. Mark for his generosity and kindness during my stay at the University of Waterloo. Many thanks is also directed to the National Science and Engixieerillg Research Council of Canada and Canadian Institute for Telecomrnu~~icationsResearch for their financial support. Contents ... Abstract ................................................................... 111 Acknowledgements ........................................................ iv ... LIST OF TABLES ........................................................ vill LIST OF FIGURES ...................................................... xi List of Abbreviations ..................................................... xii 1 Introduction ........................................................... 1 1.1 Spread Spectrum Colnmu~lications ............................... 2 1.1.1 Direct Sequence Spread Spectrum Systems ................. 2 1.1.2 Pseudorandonl Noise Sequence ............................ 5 1.2 Mobile Communication Environment ............................. 8 1.3 Code Division Multiple Access .................................. 11 1.3.1 Soft HandOff ........................................... 12 1.3.2 Increased Capacity compared with FDMA and TDMA ....... 13 1.3.3 Soft Capacity Limit ..................................... 14 1.3.4 StatisticalMultiplexing .................................. 15 1.3.5 Frequency Diversity ..................................... 15 1.3.6 Privacy ................................................ 15 1.4 Acquisition Problem ........................................ 16 1.5 Outline of the Thesis ........................................... 16 2 Literature Overview ................................................... 18 2.1 Serial Search with Active Intvgrator .............................. 19 2.2 Parallel Search with Active (lorrelator ............................ 21 2.3 Sequential Detection ........................................... 22 2.4 Matched Filter ................................................ 23 2.4.1 Verification Algorithnl ................................... 24 2.5 Estimation Based Acquisition Schemes ........................... 26 2.6 Performance Analysis .......................................... 27 2.7 Research Objective ............................................ 30 3 On-Off Keying Assisted Acquisition Scheme ........................ 31 3.1 Packet Format ................................................ 32 3.2 Flat Fading Channel Model ..................................... 33 3.3 On-Off Keying Assisted DS/SS Acquisition System ................. 37 3.3.1 Probability of False Alarm ................................ 39 3.3.2 Blocking Probability ..................................... 40 3.4 Other Techniques for Conlparison ................................ 42 3.4.1 Coincidence Detector .................................... 43 3.4.2 Other Searches .......................................... 43 3.5 Frequency Selective Fading Channel .............................. 45 3.5.1 RAKE Receiver Structure ................................ 46 3.5.2 RAKE Receiver Algorithm ............................... 48 3.6 Problenl of Partial Correlation with PN Sequence .................. 51 3.6.1 Windowing Technique ................................... 52 3.7 Simulation Results on Flat Fadiug Channel ....................... 53 3.8 Simulation Results for the Frequency Selective Channel ............. 55 3.8.1 Simulations Results on a 3-Ray Frequency Selective Channel . 57 3.9 Upper Bound Analysis ......................................... 58 3.10 Conclusions ................................................... 63 4 Barker Sequence Acquisition Scheme ................................ 65 4.1 Differential Coherent Phase Shift Keying .......................... 66 4.1.1 Binary DPSK ........................................... 67 Barker Sequence ............................................... 67 Acquisition Scheme using Llifferentially Encoded Barker Sequence .... 68 4.3.1 Receiver Hardware Inlplementatio~l ........................ 70 Two Steps Algorithm .......................................... 72 False Alarm Rate and Blocking Probability ....................... 73 Partial Correlation ............................................. 74 Windowing Technique .......................................... 76 Simulations 011 a Frequency Selective Fading Channel ............... 76 4.8.1 Results on a 3-ray Frequency Selective Channel ............. 79 Conclusions ................................................... 80 5 Power Control in Acquisition ......................................... 81 5.1 Open and Close Loop Power Control ............................. 82 5.1.1 Open-Loop Power Control ................................ 82 5.12 Closed-Loop Power (:ontrol ............................... 83 5.2 Power Control in PN Code Acquisition ........................... 84 5.3 Power Update period T, ........................................ 85 5.4 Simulation Results of Acquisition Schemes on a AWGN channel ...... 89 5.5 Conclusions ................................................... 91 6 Conclusions and Future Research .................................... 92 6.1 Discussion .................................................... 95 6.2 Future Research ................................................ 96 A Expected Busy Time Expression ..................................... 98 REFERENCES ........................................................... 100 vii List of Tables 1.1 Connection Coefficients for Maximal-Length Shift Register Generators. 7 4.1 Differential Encoding and Decoding . 67 5.1 Sinlulation Results of Various Acquisition Schetnes in a AWGN Channel. 90 5.2 Simulation Results of Various Acquisition Schemes in a Frequency Se- lective Fading Channel. 90 List of Figures