Reserach On Sequences With Low PMEPR

Accompany with the development of the wireless communication technology,especially the development of the mobile communication technology,the multi-carrier wireless communication technologies such as OFDM(Orthogonal Frequency Division Multiplexing)have achieved great success and it permeates every aspect of our lives.Now,the era of 5G has arrived.As one of the necessary technological schemes in 5G standards,OFDM system has aroused the attentions from both industrial community and academic community.Its high spectral efficiency and robustness to decline give it high potential for the development of wireless communication technology in the future.However,what should be noticed is that,until now,the high PMEPR(Peak-to-mean envelop power ratio)problem of OFDM system is still the main barrier of its development.How to solve the PMEPR control problem in OFDM system with a low cost,appears to be an urgent scientific research problem,which arouses great interests in academic community.Start from the principles of problem solving,we can divide the methods of this problem into two categories.One kind of methods in OFDM system focus on the code words themselves,hoping to control PMEPR by the selecting of code set.The other one is to control the PMEPR features of signal by secondary processing the transmission signal of OFDM system.The first kind of methods can solve this problem from the source.At the same time,there are problems such as low code rate leading by the insufficient code word set,low performance of code words and complex decoding and encoding.The main disadvantages of the second kind of solutions are the power consumption increases and system complexity increases.Therefore,to find a suitable solution for the PMEPR control problem of OFDM system still need a long way to go.To sum up,the technology of PMEPR control in OFDM system is great significant for the application and development of OFDM,and even the entire field of wireless communications.This thesis will focus on the research of solving PMEPR control problem in OFDM system by coding method,so that achieve the PMEPR control from source.Reduce the cost of OFDM system and improve the efficiency of OFDM system without reducing the transmission efficiency.Under this research motivation,we presented new constructions of sequences with low PMEPR.The new constructions in our paper have more powerful abilities for sequences generating.The main cores of this thesis are constructions of low PMEPR sequences for OFDM system.We attempt to solve the PMEPR control problem in OFDM system without influencing the transmission efficiency at the same time.For this topic,we study the sequences such as Golay complementary pair sequences,Golay complementary set sequences and nearcomplementary sequences.In this thesis,we will present new constructions of low PMEPR sequences and analysis the Boolean functions of these sequences,while review the previous constructions.The main contributions of this thesis can be concluded as follow:First of all,based on the structure of the Golay complementary sequence set,we propose a construction of Golay complementary sequence set based on Para-unitary matrices.Through this scheme,many new Golay complementary sequence sets can be constructed.And through the analyzation of the Boolean functions of sequences generated,we can find that the sequences generated by new construction have higher order Boolean functions than the sequences in previous constructions.Through this matrix construction,by applying matrices with particular properties in recursive computation,we can guarantee that the sequences generated have some important properties.We discuss the details in Section 5.The second,in this thesis,we will present a generalized permutation method for the new construction of Golay complementary set sequence.By this method,the sequence number that can be constructed with the same length will greatly increase.This number is equal to the previous constructions of Golay complementary sequences based on Boolean function with the same length.So that,this new generalized method gives a bridge between Boolean function based methods and matrices based methods.Furthermore,in this thesis,based on our new construction of Golay complementary sequence set based on Para-unitary matrices and previous constructions,we will present a new construction of Golay complementary set based on Boolean function.Through this method,we can associate the constructions based on Para-unitary matrices and constructions based on Boolean function.And greatly reduce the computation of generating Golay complementary sequences by our new construction.In the end,based on our new constructions of Golay complementary sequence set,we generalize the applications of these methods to the areas of near complementary sequences and Golay complementary sequences on QAM constellation.Through this way,we can greatly improve the size of sequence sets of low PMEPR sequence by slightly rise the upper bound of the PMEPR of code word sets.