Abstract a Software-Defined Radio Based on the Unified
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ABSTRACT A SOFTWARE-DEFINED RADIO BASED ON THE UNIFIED SMSE FRAMEWORK by Robert James Graessle The purpose of this research was to implement a software-defined radio based on a recently developed framework for constructing various spectrally-modulated, spectrally-encoded (SMSE) signals. Two candidate waveforms (MC-CDMA and TDCS) are selected to demonstrate the capabilities of the framework, and they are modulated using antipodal signaling. A transmitter and receiver are each implemented on separate digital signal processor starting kits (DSK). A channel simulator consisting of additive white Gaussian noise and narrowband BPSK interferers is implemented on an FPGA. Burst transmissions from transmitter to receiver through the channel simulator are conducted to evaluate the bit-error rate performance of the system. Results from floating point simulation, fixed point simulation and hardware implementation are presented. The bit-error results from the hardware implementation closely match theoretical results. Also, TDCS is shown to mitigate effects of narrowband interference compared to MC- CDMA. A SOFTWARE-DEFINED RADIO BASED ON THE UNIFIED SMSE FRAMEWORK A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science Department of Electrical & Computer Engineering by Robert James Graessle Miami University Oxford, Ohio 2010 Advisor________________________ Dr. Chi-Hao Cheng Reader_________________________ Dr. Dmitriy Garmatyuk Reader_________________________ Dr. Vasu Chakravarthy Table of Contents List of Tables .............................................................................................................................iv List of Figures ............................................................................................................................. v Acknowledgments.................................................................................................................... vii 1. Introduction............................................................................................................................ 1 1.1. Background ......................................................................................................................1 1.2. Problem Statement............................................................................................................1 1.3. Goals ................................................................................................................................2 1.4. Scope & Assumptions ......................................................................................................2 1.5. Methodology ....................................................................................................................3 1.6. Materials ..........................................................................................................................4 1.7. Overview ..........................................................................................................................4 2. Literature Review .................................................................................................................... 6 2.1. A Brief History of Software-Defined Radio and Cognitive Radio .....................................6 2.2. Spectrally-Modulated, Spectrally-Encoded Waveforms ....................................................7 2.2.1. Orthogonal Frequency-Division Multiplexing (OFDM) .............................................8 2.2.2. Code Division Multiple Access (CDMA) ................................................................. 10 2.2.3. Multicarrier Code-Division Multiple Access (MC-CDMA) ...................................... 11 2.2.4. Transform Domain Communications System (TDCS) .............................................. 12 2.2.5. Differences between OFDM, MC-CDMA and TDCS .............................................. 15 2.3. The Unified SMSE Framework....................................................................................... 17 2.4. DSP as Implementation Platform for Software-Defined Radio ........................................ 20 3. Design Flow .......................................................................................................................... 22 3.1. Floating Point Simulation ............................................................................................... 22 3.2. Fixed Point Simulation ................................................................................................... 24 3.2.1. Scaling and Quantization ......................................................................................... 25 3.2.2. Fixed Point Fast Fourier Transform and Cross-Correlation ...................................... 26 3.2.3. Vectorization ........................................................................................................... 27 3.3. Hardware Implementation .............................................................................................. 27 4. Transmitter Implementation .................................................................................................. 28 4.1. System Overview ........................................................................................................... 28 4.2. Transmitter ..................................................................................................................... 29 4.2.1. Message Generation ................................................................................................. 30 ii 4.2.2. Spectrum Estimation ................................................................................................ 30 4.2.3. SMSE Vector Generation ......................................................................................... 32 4.2.3.1. Coding Vector ................................................................................................... 33 4.2.3.2. Frequency Usage Vector ................................................................................... 36 4.2.4. Hadamard Multiplication ......................................................................................... 36 4.2.5. Inverse Fourier Transform and Modulation .............................................................. 37 4.2.6. Concatenation, Buffering & Transmission ............................................................... 39 5. Channel Model Implementation ............................................................................................ 41 5.1. Nallatech XtremeDSP Development Kit ......................................................................... 41 5.2. System Generator Environment ...................................................................................... 41 5.3. Additive White Gaussian Noise Channel ........................................................................ 42 5.3.1. Hardware Implementation of AWGN ....................................................................... 43 5.4. Narrowband Interference ................................................................................................ 43 5.4.1. Hardware Implementation of BPSK Interferers ........................................................ 45 6. Receiver Implementation....................................................................................................... 48 6.1. Receiver Operation ......................................................................................................... 48 6.2. Reference Waveform Generation .................................................................................... 49 6.3. Acquisition and Synchronization of Received SMSE Signals.......................................... 49 6.4. Correlation Receiver ....................................................................................................... 51 6.5. Symbol Timing Recovery ............................................................................................... 52 6.6. Bit Error Rate Calculation .............................................................................................. 54 7. Results .................................................................................................................................. 55 7.1. Floating Point Simulation Results ................................................................................... 56 7.2. Fixed Point Simulation Results ....................................................................................... 59 7.3. Hardware Implementation Results .................................................................................. 62 7.4. Discussion ...................................................................................................................... 66 8. Conclusion ............................................................................................................................ 69 8.1. Recommendations for Future Work ................................................................................ 69 References ................................................................................................................................ 71 iii List of Tables Table 2.1 – Overview of the SMSE framework variable instantiations for TDCS and MC-CDMA ................................................................................................................................................. 19 Table 4.1 – Phase Values Used for TDCS ................................................................................