Design and Implementation of a Cognitive Radio Baseband Transceiver using Discrete Wavelet Multi-Tone Modulation

本篇論文提出一個新的感知無線電系統架構，目標是透過對使用者目前所在之處，未被使用到的全球移動通訊系統（GSM）之頻譜進行再利用，來提供類似802.11 WLAN的無線區域網路之服務。我們將過去針對所謂的數位用戶迴路（DSL）系統所提出的離散小波多音調（discrete wavelet multi-tone）調變，用於感知無線電系統。相較於熱門的正交多頻分工（OFDM）調變，該調變可提供較高的旁葉衰減（sidelobe attenuation），故其產生的鄰近頻道洩漏（adjacent channel leakage）功率較低，且具備較佳的抗干擾能力。當感知無線電系統的可用頻帶是由零碎而不連續的小塊頻帶所構成，且其可用頻譜組態可能隨時間或地域而變化的情形下，離散小波多音調調變的特性使其優於正交多頻分工調變。 為了進行收發機設計，我們首先針對離散小波多音調調變推導其訊號模型，並分析其訊號與干擾的特性，就同步、通道估測、等化等工作的需求，決定合適的演算法。設計完成之後，我們採用0.18-In this thesis, design and implementation of a discrete wavelet multi-tone (DWMT) based baseband transceiver for cognitive radio applications are presented. The proposed system aims to provide wireless local-area network (WLAN service similar to IEEE 802.11 WLAN by exploiting the unused GSM spectrum. The DWMT modulation scheme originally proposed for wireline digital subscriber loop (DSL) applications is adopted as the modulation scheme. This modulation has stronger side-lobes attenuation than the popular OFDM modulation and thus generates much lower adjacent channel leakage, making it suitable for applications with dynamically-allocated spectrum. Signal and interference analysis of the adopted DWMT modulation is presented and signal processing techniques that tackle synchronization, equalization, and detection are developed. The entire DWMT-based baseband receiver is integrated and implemented in 0.18μm CMOS technology. Techniques such as hardware sharing, common term extraction, subcarrier constant multiplications removal, etc., are applied for hardware reduction. In addition, novel bi-directional SRAM-based delaylines are designed for memory saving. Measurement results of the fabricated receiver IC show that it functions well at 25.6 MHz operating frequency while drawing 165 mW from a 1.8 V supply voltage. When the whole 25.6 MHz bandwidth is available, this receiver IC can provide up to 153.6 Mbps of data transmission.1 Introduction 1 1.1 Next-Generation Radio Systems . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Motivation of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Organization of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 Cognitive Radio 13 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 PreviousWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 Regulatory Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.4 Physical Layer Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.4.1 Antenna and Front-end . . . . . . . . . . . . . . . . . . . . . . . . 27 2.4.2 CR SpectrumManagement . . . . . . . . . . . . . . . . . . . . . 29 2.4.3 SpectrumSensing Techniques . . . . . . . . . . . . . . . . . . . . 31 2.4.4 Control Channel Establishment . . . . . . . . . . . . . . . . . . . 36 2.4.5 Waveforms and modulation . . . . . . . . . . . . . . . . . . . . . 37 2.5 IEEE 802.22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3 Discrete Wavelet Multi-Tone (DWMT) Modulation 43 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.2 Wavelets and Filter Banks . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.3 Theory of Filter Banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.3.1 Two-Channel Filter Banks . . . . . . . . . . . . . . . . . . . . . . 47 3.3.2 M-ChannelMaximally Decimated Filter Banks . . . . . . . . . . 51 3.4 Modulated Filter Banks . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.5 Exponentially-Modulated Filter Bank (EMFB) . . . . . . . . . . . . . . . 57 3.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.5.2 Prototype Generation. . . . . . . . . . . . . . . . . . . . . . . . . 58 3.5.3 Structure of the Fast Algorithm . . . . . . . . . . . . . . . . . . . 61 3.5.4 Sub-carrier Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . 63 4 Baseband Channel Model and Signal Model 65 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.2 Transmitter Impairments . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.2.1 DAC Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.2.2 Power Amplifier Non-linearity . . . . . . . . . . . . . . . . . . . . 68 4.3 Radio Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.3.1 AdditiveWhite Gaussian Noise (AWGN) . . . . . . . . . . . . . . 71 4.3.2 Multipath Fading Channel . . . . . . . . . . . . . . . . . . . . . . 72 4.4 Receiver Impairments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.4.1 Carrier Frequency Offset (CFO) . . . . . . . . . . . . . . . . . . . 76 4.4.2 Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.4.3 I/QMismatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 4.4.4 DC Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 4.4.5 Sampling Clock Offset (SCO) . . . . . . . . . . . . . . . . . . . . 84 4.5 SignalModel of EMFB-Based DWMTModulation. . . . . . . . . . . . . 87 5 DWMT-Based Cognitive Radio System Design 91 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.2 System Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 5.3 System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.4 Packet Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 5.5 Transmitter Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.5.1 Punctured Convolutional Encoding . . . . . . . . . . . . . . . . . 98 5.5.2 Interleaving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 5.5.3 ConstellationMapping . . . . . . . . . . . . . . . . . . . . . . . . 100 5.5.4 Preamble Generation . . . . . . . . . . . . . . . . . . . . . . . . . 101 5.5.5 Training Symbol Generation . . . . . . . . . . . . . . . . . . . . . 102 5.5.6 Pilot Sub-carrier Insertion . . . . . . . . . . . . . . . . . . . . . . 103 5.5.7 Exponentially-Modulated Synthesis Bank . . . . . . . . . . . . . . 104 5.5.8 Transmitter Hardware Architecture . . . . . . . . . . . . . . . . . 105 5.6 Receiver Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 5.6.1 Carrier Frequency Offset Estimation . . . . . . . . . . . . . . . . 110 5.6.2 Carrier Frequency Offset Compensation . . . . . . . . . . . . . . . 112 5.6.3 Symbol Timing Detection . . . . . . . . . . . . . . . . . . . . . . 113 5.6.4 Frequency Error Detection . . . . . . . . . . . . . . . . . . . . . . 114 5.6.5 Sampling Clock Offset Compensation . . . . . . . . . . . . . . . . 115 5.6.6 Channel Estimation and Equalization . . . . . . . . . . . . . . . . 117 5.6.7 Exponentially-Modulated Analysis Bank . . . . . . . . . . . . . . 123 5.6.8 Soft-Output Demapper . . . . . . . . . . . . . . . . . . . . . . . . 124 5.6.9 De-Interleaving . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 5.6.10 Convolution Decoding . . . . . . . . . . . . . . . . . . . . . . . . 127 5.7 System Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 6 Receiver Hardware Implementation 135 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 6.2 Fixed-Point Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 6.3 Low-Complexity Architecture and Circuit Design . . . . . . . . . . . . . 142 6.3.1 Exponentially-Modulated Analysis Bank . . . . . . . . . . . . . . 142 6.3.2 Carrier Frequency Offset Estimation . . . . . . . . . . . . . . . . 154 6.3.3 Symbol Timing Detection . . . . . . . . . . . . . . . . . . . . . . 157 6.3.4 Channel Estimation and Equalization . . . . . . . . . . . . . . . . 158 6.3.5 Frequency Error Detection . . . . . . . . . . . . . . . . . . . . . . 159 6.3.6 Summary on Hardware Reduction . . . . . . . . . . . . . . . . . . 160 6.4 Design for Testability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 6.4.1 Memory Build-In-Self-Test . . . . . . . . . . . . . . . . . . . . . . 162 6.4.2 Scan Chain Insertion . . . . . . . . . . . . . . . . . . . . . . . . . 162 6.4.3 Ad-Hoc Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 6.5 Physical Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 6.6 Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 7 Conclusion 169 A Derivation and Analysis of Received DWMT Signal 187 B Fast Implementation of type-IV DCT and type-IV DST via FFT 19