顧孟愷臺灣大學：資訊工程學研究所范君霖Fan, Chun-LinChun-LinFan2007-11-262018-07-052007-11-262018-07-052006http://ntur.lib.ntu.edu.tw//handle/246246/53645Orthogonal Frequency Division Multiplexing (OFDM) is popular modulation scheme for wireless system. Because OFDM has advantages of multipath-delay-spread tolerance, immunity to frequency selective fading channel and high spectral efficiency, many wireless systems have adopted the OFDM technique as a choice. However, Peak-to-average ratio (PAPR) is a main drawback of OFDM. PAPR problem is caused by Inverse Discrete Fourier Transform (IDFT). IDFT makes the OFDM symbols with high PAPR. High PAPR increases the complexity and the cost of an OFDM system. So far, many various PAPR reduction schemes have been published. Most of them have high online computation complexity and must modify the architecture of OFDM system. We advocate an idea to solve PAPR problem in this thesis. The idea satisfies to use offline computation to replace online computation without modifying the architecture. We want to reduce the PAPR by finding out low PAPR codes. However, the solution space is too large, so exhaustive search is not efficient. We want to search low PAPR codes with search algorithm, so an efficient criterion is needed. We explain the criterion in our thesis. The target code of the thesis is the Low-Density Parity-Check (LDPC) code. The LDPC codes have received a lot of attention recently because of there excellent performance and low decoding complexity. Finally, some simulated result is presented in the thesis.ABSTRACT III TABLE OF CONTENTS IV LIST OF FIGURES V CHAPTER 1 : INTRODUCTION 1 1.1 OVERVIEW OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM 2 1.2 DEFINITION OF PEAK-TO-AVERAGE POWER RATIO FOR OFDM SYSTEM 6 1.3 THESIS ORGANIZATION 12 CHAPTER 2 : RELATED WORK 13 2.1 SELECTED MAPPING 13 2.2 PARTIAL TRANSMIT SEQUENCE 15 2.3 ACTIVE CONSTELLATION EXTENSION 17 2.4 TONE RESERVATION 18 2.5 PAPR REDUCTION WITH CHANNEL CODING 21 CHAPTER 3 : PAPR ESTIMATION ALGORITHM FOR BLOCK CODE 23 3.1 PRINCIPLE OF PAPR ESTIMATION ALGORITHM 25 3.2 IMPLEMENTATION OF PAPR ESTIMATION ALGORITHM 31 3.4 ESTIMATION FOR CONVOLTIONAL CODES 33 3.4.1 Encoding of Convolutional Codes 33 3.4.2 Decoding of Convolutional Codes 34 3.5 ESTIMATION FOR LOW-DENSITY PARITY-CHECK CODES 36 3.5.1 Tanner Graph Description for LDPC Code Structure 37 3.5.2 Encoding of LDPC Codes 38 3.5.3 Decoding of LDPC Codes 38 CHAPTER 4 : EXPERIMENTAL RESULTS 40 4.1 SIMULATION RESULTS OF CONVOLUTIONAL CODES 40 4.2 SIMULATION RESULTS OF LDPC CODES 42 4.3 DISCUSSION OF SIMULATION RESULTS 44 CHAPTER 5 : CONCLUSION AND FUTURE WORK 48 REFERENCE 501166862 bytesapplication/pdfen-US低峰均值奇偶校驗碼LDPC codePAPRPARCrest factorthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53645/1/ntu-95-R93922086-1.pdf