林茂昭臺灣大學：電信工程學研究所楊宗杰Yang, Tsung-ChiehTsung-ChiehYang2007-11-272018-07-052007-11-272018-07-052004http://ntur.lib.ntu.edu.tw//handle/246246/58628正交分頻多工系統(OFDM)是一種使用多重載波調變的技術並且被使用在許多無線和有線的通訊中。然而，正交分頻多工技術有一個主要的缺點。那就是，正交分頻多工的訊號可能有大的峰均值功率比(peak-to-average power ratio)。 本論文中之設計目的是擁有高峰均值削減能力的同時不損失位元錯誤率的表現。因此我們使用錯誤更正碼的方式來降低峰均值功率比。考慮在不同的選擇性映射(Selective mapping)的架構下，研究其中有些不需使用附帶消息位元(Side-information)或使用少許消息位元之方式。 首先，使用渦輪編碼之低峰均值正交分頻多工系統。我們以數種不同的打亂機制(scramble)以提供多個擁有不同峰均值但帶有相同消息之傳送符號，並選擇最小之峰均值傳送。在接收端，我們可以在疉代解碼的過程中偵測出傳送之符號而不需使用附帶消息位元。為了使設計更加彈性而使用少許附帶消息位元，更進一步增進峰均值之削減能力。接著在相同的設計理念下，改採用廣義低密度碼編碼之低峰均值正交分頻多工系統，以達到在不需使用附帶消息位元而同時擁有較佳的錯誤更正能力及低峰均值。 此外我們亦探討有關利用籬柵整型(Trellis shaping)以降低峰均值的可行性。Orthogonal frequency division multiplexing (OFDM) system is a technique of multicarrier modulation and is popular in many wired and wireless communications. However, OFDM system has a major drawback. OFDM signals are likely to have large values of peak-to-average power ratio (PAPR). In this thesis, our main object is to achieve high PAPR reduction capability and low bit error rate. We present two classes PAPR reduction techniques by using error correcting code. All of them are based on the selective mapping. In some occasions, side information is not needed for the receiver. The first class is the turbo coded OFDM system with PAPR reduction techniques. We use several scrambling methods to provide several distinct OFDM symbols according to the same message and different PAPR values. At the receiver we can detect the transmission symbol without side information through the process of iterative decoding. The second class is the GLD coded OFDM system with the possibility of designing better PAPR reduction. In addition, we also study the technique of trellis shaping to see the effect of PAPR reduction.1 Introduction 1 2 Orthogonal Frequency Division Multiplexing (OFDM) Basics 5 2.1 Basis Concept of OFDM 5 2.2 Guard time, Cyclic Extension and Windowing 7 2.3 OFDM Signals 11 2.3.1 Discrete-time representation of OFDM signals 12 2.4 OFDM System simulation Environment 14 3 Peak-to-Average Power Ratio in OFDM Signals 16 3.1 Properties of the Peak-to-Average Power Ratio (PAPR) in OFDM 17 3.2 Redundancy Based PAPR Reduction Techniques 21 3.2.1 Adaptive Symbol Selection (Selective Mapping) 23 3.3 Distortion Based PAPR Reduction Techniques 25 3.3.1 PAPR Reduction Technique by Deliberate Clipping 25 3.3.2 Soft Envelope Limiter 25 4 Techniques for PAPR Reduction in Turbo Coded OFDM Systems 27 4.1 Coded Orthogonal Frequency Division Multiplexing Systems 28 4.2 Turbo Code Encoder and its Iterative MAP Decoder 30 4.2.1 A Turbo Encoder 30 4.2.2 The Interleaver Design 32 4.2.3 The Turbo Decoder 35 4.2.4 Pragmatic Binary Turbo Coded Modulation 42 4.3 Side Information Free Method for PAPR Reduction 44 4.3.1 Main Idea of the Side Information Free Method 45 4.4 System A: Turbo Coded OFDM System Using m-sequence with Side Information 49 4.5 System B: Using m-sequence to Reduce PAPR without Side Information in Turbo coded OFDM Systems 53 4.6 System C: Using Bit Interleaver to Reduce PAPR without Side information in Turbo Coded OFDM Systems 58 4.7 System D: Trubo COdedOFDM System Using Distinct Interleavers in Turbo Encoder 62 4.8 Compare Systems A, B, C, D and Their Combination 65 5 Techniques for PAPR Reduction in GLD Coded OFDM Systems 73 5.1 Basics of Generalized Low Density Codes 74 5.2 Decoding Scheme 75 5.3 GLD coded OFDM Systems 76 6 Performance Analysis of Clipped OFDM Signal 81 6.1 The Clipping Channel Model 81 6.2 Signal-to-Distortion Ratio 84 6.3 Clipped Signal Analysis of Coded OFDM System 87 7 Using Trellis Shaping to Reduction PAPR in OFDM Systems 90 7.1 Trellis Shaping 90 7.2 Sign-Bit Shaping 92 7.3 Metric Computation in Shaping Decoder 94 7.4 Simulation Result 97 8 Conclusion and Future Work 1011885579 bytesapplication/pdfen-US峰均值功率比正交分頻多工系統渦輪碼PAPROFDMTurbo codethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58628/1/ntu-93-R91942083-1.pdf