Spectrum Efficient Peak-to-Average Power Ratio Reduction for OFDM Systems

• Material Type: 博士論文
• Title: Spectrum Efficient Peak-to-Average Power Ratio Reduction for OFDM Systems
• Author/Editor: MD., SAKIR HOSSAIN
• Author Heading: MD., SAKIR HOSSAIN
• Publication Date: 2018
• Publication Date (W3CDTF): 2018
• Alternative Title: OFDMシステムのための周波数効率の良いピーク対平均電力比低減
• Periodical title: 博士論文（埼玉大学大学院理工学研究科（博士後期課程））
• Degree grantor/type: 埼玉大学
• Date Granted: 2018-03-23
• Date Granted (W3CDTF): 2018-03-23
• Dissertation Number: 乙第245号
• Degree Type: 博士(学術)
• Conferring No. (Dissertation): 乙第245号
• Text Language Code: eng
• Subject Heading: Wireless communications; mobile; cellular communications; multicarrier communications; OFDM; PAPR; channel; energy efficiency; spectrum efficiency; CCDF; BER; dummy sequence insertion; tone reservation; null subcarrier; pilot subcarrier; power saving; orthogonal pilot sequence; walsh-hadamard sequence; Zadoff-Chu sequence; maximum likelihood detection; in-band noise; out-of-band distortion; adjacent channel interference; 4G; 5G; Wi-Fi; WLAN; WiMAX; consumer electronics
• Target Audience: 一般
• Note (General): type:text; Wireless communications have witnessed an unprecedented growth in last two decades. This enables the explosive growth of multimedia communications in last decade, which demands high data rate. Since the spectrum is a limited resource, it is imperative to use it in the most efficient way to meet the demand. Orthogonal frequency division multiplexing (OFDM), the most spectrum efficient waveform to date, is regarded as the best tool to meet the data rate demand. Meeting the rate demand, OFDM, however, introduces new problems, such as low energy efficiency, adjacent channel interference (ACI) and in-band noise, because of its high peak-to-average power ratio (PAPR). The high PAPR reduces the power efficiency of a high power amplifier (HPA), thereby causing power wastage; this reduces battery life of portable devices. Furthermore, this escalates operating expenditure of the networks. The ACI badly affect quality of service of the network by degrading bit error rate (BER). The high PAPR problem is so serious issue that OFDM could not be included in the uplink of fourth generation cellular networks considering longer battery requirement of cell phones. In addition, since most of the candidate waveforms for the forthcoming fifth generation (5G) wireless systems are based on the OFDM and energy efficiency is an important requirement of the 5G, it is necessary to make OFDM as an energy efficient system by reducing the high PAPR.This thesis deals with the high PAPR issue. In contrast to the most of the traditional PAPR reduction techniques where spectrum efficiency of OFDM is partly compromised to attain the reduced PAPR by reserving a portion of the available bandwidth for either reducing PAPR or transmitting side information (SI), the aim of the thesis is to reduce PAPR maintaining 100% spectrum efficiency of an OFDM system. In this endeavor, we propose four different transmitter and receiver designs which attain significantly reduced PAPR without affecting the spectrum efficiency.We propose a novel PAPR reduction scheme by utilizing pilot subcarriers in addition to their conventional use for channel estimation. We iteratively change the positions (which implies frequencies) of the pilot subcarriers among the data subcarriers to check which positions of the pilots produce the lowest PAPR. Instead of sending SI about the positions of the pilots, we design the receiver in such a way that it can detect the pilots blindly utilizing their comparatively higher power and equidistant properties. This scheme can attain up to 2.5 dB PAPR reduction without sacrificing spectrum efficiency. Furthermore, the amount of power saving attained by it is also analyzed.Next, we improve the performance of an existing null subcarrier assisted PAPR reduction technique which suffers from extremely high computational complexity and BER. We propose a new transmitter by changing switching strategy between the data and null subcarriers incorporating a new feature of the switched null subcarriers: any two neighboring null subcarriers must be equidistant. Utilizing the equidistant and zero energy property of the null subcarriers, we propose a very efficient receiver design that can attain more than 5 dB signal-to-noise ratio (SNR) gain and 98% reduction of the computational complexity.The third proposed scheme modifies an existing PAPR reduction technique based on orthogonal pilot sequence (OPS). The OPS scheme suffers from very limited PAPR reduction capability. Instead of just changing pilot symbols’ phases according to a set of orthogonal sequences as is done in the OPS scheme, we propose to use the pilot symbols’ phases as the phase factors and multiply different groups of the data subcarriers by their respective phase factors produced from the corresponding pilot symbols’ phases. This scheme can attain about three-times more PAPR reduction compared to the original OPS technique and requires 90% less computations compared to the existing modified OPS scheme.Finally, we propose to improve dummy sequence insertion (DSI) and tone reservation techniques of PAPR reduction. These two techniques had been suffering from extremely low spectrum efficiency since their inception because of their requirement of the reservation of a certain number of subcarriers for the PAPR reduction. To overcome the shortcoming, we propose the notion of subcarrier group modulation which makes some data subcarriers free for the PAPR reduction by sending their corresponding data by some other means without any additional spectrum. This eliminates the rate loss caused by the PAPR reduction in the DSI scheme. In addition to the PAPR reduction application, it can be included for increasing spectrum efficiency of any unmodified OFDM system as well.; Abstract iDedication vAcknowledgement viContents viiList of Figures xList of Tables xiii1 Introduction 11.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3 Publications Arising From The Research . . . . . . . . . . . . . . 61.4 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Principles of OFDM 92.1 Overview of Wireless Channels . . . . . . . . . . . . . . . . . . . . 92.1.1 Path Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.1.2 Small-Scale Fading . . . . . . . . . . . . . . . . . . . . . . 102.2 History of OFDM . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.3 Multiplexing Techniques . . . . . . . . . . . . . . . . . . . . . . . 152.4 Principles of multi-carrier communications . . . . . . . . . . . . . 172.5 OFDM Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202.5.1 Orthogonality . . . . . . . . . . . . . . . . . . . . . . . . . 202.5.2 OFDM Architecture . . . . . . . . . . . . . . . . . . . . . 222.5.3 OFDM Transmission over Time Varying Channels . . . . . 272.5.4 Spectrum Efficiency . . . . . . . . . . . . . . . . . . . . . . 302.5.5 Impacts of Null Subcarriers on SNR . . . . . . . . . . . . . 322.5.6 Limitations of OFDM . . . . . . . . . . . . . . . . . . . . 353 Traditional PAPR Reduction Techniques 403.1 PAPR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.2 Conventional PAPR Reduction Techniques . . . . . . . . . . . . . 473.2.1 Signal distortion based PAPR reduction . . . . . . . . . . 483.2.2 Multiple Signalling . . . . . . . . . . . . . . . . . . . . . . 513.2.3 Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613.3 Scope of Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624 Enhanced OFDM Performance with Pilot-Aided Reduced Peak-to-Average Power Ratio 644.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674.3 Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . 674.3.1 Transmitter Design . . . . . . . . . . . . . . . . . . . . . . 684.3.2 Receiver design . . . . . . . . . . . . . . . . . . . . . . . . 704.3.3 Example of pilot detection . . . . . . . . . . . . . . . . . . 754.3.4 Features of the proposed system . . . . . . . . . . . . . . . 764.4 System Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 774.4.1 PAPR reduction . . . . . . . . . . . . . . . . . . . . . . . 784.4.2 BER improvement . . . . . . . . . . . . . . . . . . . . . . 814.4.3 Power Saving . . . . . . . . . . . . . . . . . . . . . . . . . 844.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875 Low Complex Null Subcarrier-Assisted OFDM PAPR Reduction with Improved BER 885.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.3 Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . 925.3.1 Transmitter Design . . . . . . . . . . . . . . . . . . . . . . 925.3.2 Receiver Design . . . . . . . . . . . . . . . . . . . . . . . . 945.4 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . 965.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026 PAPR reduction for OFDM systems using pilot derived phase factors 1036.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1066.3 Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076.4 Performance evaluation . . . . . . . . . . . . . . . . . . . . . . . . 1116.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137 Spectrum Efficient DSI-Based OFDM PAPR Reduction by Sub-carrier Group Modulation 1147.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1147.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177.3 Proposed Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . 1187.3.1 Subcarrier Group Modulation . . . . . . . . . . . . . . . . 1187.3.2 DSI with SGM PAPR reduction scheme . . . . . . . . . . 1217.4 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . 1247.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1278 Conclusions and Future work 1298.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131References 134; 指導教員 : 島村徹也
• DOI: 10.24561/00018493; https://doi.org/10.24561/00018493
• Persistent ID (NDL): info:ndljp/pid/11278514; https://dl.ndl.go.jp/pid/11278514
• Collection: 障害者向け資料
• Collection (Materials For Handicapped People:1): テキストデータ
• Collection (particular): 国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文; https://dl.ndl.go.jp/collections/A00014
• Acquisition Basis: 博士論文（自動収集）
• Date Accepted (W3CDTF): 2019-05-06T10:27:56+09:00
• Date Created (W3CDTF): 2019-02-08
• Format (IMT): application/pdf
• Access Restrictions: 国立国会図書館内限定公開
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• Periodical Title (URI): http://dx.doi.org/10.24561/00018493; http://id.nii.ac.jp/1586/00018493/
• Data Provider (Database): 国立国会図書館 : 国立国会図書館デジタルコレクション; https://dl.ndl.go.jp

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