A Study on PAPR of OFDM Systems

We propose RCFBD scheme, imposing bounded distortion~(BD) mechanism over recursive clipping and filtering~(RCF), to achieve effective peak-to-average power ratio~(PAPR) reduction for orthogonal frequency division multiplexing~(OFDM) systems while simultaneously keeping distortion under control to reduce the penalty to error performance. We generalize RCFBD for OFDM systems consisting of various types of tones. Making use of reserved tones can get effective PAPR reduction at smaller distortion bound. We propose hybrid RCFBD scheme combining ACESGP, active constellation extension~(ACE) with smart gradient projection~(SGP), and RCFBD so that low PAPR can be obtained within 3 recursions and BD constraint remains intact. We investigate the mechanism of ACESGP in more detail and expose the feasibility for ACE to use the fixed step size which costs less complexity than ACESGP and presents PAPR reduction comparable to ACESGP.We propose RPSxACE scheme to exploit the available region of ACE for BPSK/OFDM. RPSxACE imposes random phase sequence over the BPSK data so that the input data to OFDM modulator is complex-valued to get further PAPR reduction. We propose a new time-domain inter-block method, called UniTS, to involve multiple OFDM blocks together to reduce PAPR. UniTS combines unitary transform and SLM on time-shift candidates to reduce PAPR. UniTS can save almost 80 percent of the complexity of SLM in some cases. We propose a way to get a good estimate of the distribution of IPAR for OFDM using SLM/UniTS. We also apply the derived distribution of IPAR to compute the post-clip average output power to demonstrate the effectiveness of our derivation.口試委員會審定書 i 志謝 iii 中文摘要 v {chapter}{Abstract}{vii} {chapter}{Contents}{viii} {chapter}{List of Figures}{xiii} {chapter}{List of Tables}{xvii} {chapter}{ {1}Introduction}{1} {section}{ {1.1}Classifications of PAPR reduction methods}{2} {section}{ {1.2}Outline of Thesis}{3} {chapter}{ {2}Notations}{7} {section}{ {2.1}PAPR}{7} {section}{ {2.2}CDF and CCDF}{9} {section}{ {2.3}Complexity and Tradeoff}{10} {section}{ {2.4}System model}{12} {chapter}{ {3}RCFBD scheme}{15} {section}{ {3.1}Introduction}{15} {section}{ {3.2}OCF and RCF}{16} {section}{ {3.3}RCF with Bounded Distortion}{18} {section}{ {3.4}Complexity Evaluation}{22} {section}{ {3.5} PAPR Reduction and Distortion}{23} {subsection}{ {3.5.1} PAPR Reduction Capability}{23} {subsection}{ {3.5.2} Constellation shrinkage and Average Distortion}{25} {section}{ {3.6}Error Performances }{29} {section}{ {3.7}Concluding Remarks}{32} {chapter}{ {4}Generalization and Speedup of RCFBD}{35} {section}{ {4.1}Introduction}{35} {section}{ {4.2}Zero-Insertion(ZI) Oversampling}{36} {section}{ {4.3}Generalized RCFBD for various kinds of tones}{37} {section}{ {4.4}Speedup of RCFBD }{40} {section}{ {4.5}Hybrid RCFBD}{45} {section}{ {4.6}Simulation Results and Discussions}{46} {section}{ {4.7}Convergence of RCFBD}{53} {section}{ {4.8}Conclusions}{55} {chapter}{ {5}ACE Investigation}{57} {section}{ {5.1}Introduction}{57} {section}{ {5.2}ACE with modified SGP}{58} {section}{ {5.3}Fixed step size for ACE}{61} {section}{ {5.4}Distribution of step size by SGP}{62} {section}{ {5.5}ACE considering bounded extension constraint and reserved tones}{64} {section}{ {5.6}Simulation Results for ACE using uFix and BE constraint }{67} {section}{ {5.7}RPSxACE: Combination of RPS and ACE for OFDM}{71} {section}{ {5.8}Simulation Results for RPSxACE}{74} {section}{ {5.9}Conclusions}{76} {chapter}{ {6}UniTS scheme for PAPR reduction}{77} {section}{ {6.1}Introduction}{77} {section}{ {6.2}Linear transform of Multiple OFDM Blocks }{78} {section}{ {6.3}UniTS scheme}{81} {subsection}{ {6.3.1}Embedding side information}{81} {subsection}{ {6.3.2}Extension to multiple blocks}{83} {subsection}{ {6.3.3}Embedding pilot tones}{85} {subsection}{ {6.3.4}Receiver Structure}{86} {section}{ {6.4}Complexity Analysis}{86} {section}{ {6.5}Simulation Results}{92} {section}{ {6.6}Conclusions}{95} {section}{ {6.7}Appendix}{97} {chapter}{ {7}Probability distribution for SLM and UniTS}{101} {section}{ {7.1}Introduction}{101} {section}{ {7.2}PDF, CDF, and CCDF for SLM}{102} {section}{ {7.3}Computation Issues and Solutions}{107} {section}{ {7.4}PDF, CDF, and CCDF for UniTS}{112} {section}{ {7.5} Post-Clip Average Output Power $P_{AV}$}{116} {section}{ {7.6}Computation and Simulation Results}{117} {subsection}{ {7.6.1}Results for SLM}{117} {subsection}{ {7.6.2}Results for UniTS}{121} {section}{ {7.7}Conclusions}{123} {chapter}{ {8}Thesis Conclusions and Remarks}{125} {chapter}{References}{127