Constructions Of Almost Complementary Sequences Based On Non-standard Golay Complementary Sequences

Orthogonal frequency division multiplexing（OFDM）is a widely used multi-carrier com-munication technology.However,OFDM technology has a great defect,that is,its transmis-sion signal has a high peak-to-mean envelope power ratio（PMEPR）.High PMEPR will bring many disadvantages to the system,in order to stabilize the performance of OFDM system,the PMEPR of its transmission signal should be reduced as much as possible.The methods to reduce PMEPR include probability method,amplitude limiting method and coding method.The coding method to reduce PMEPR is to construct a codebook composed of low P-MEPR codewords,and then use it in OFDM system.At present,the coding method using Golay complementary sequence（GCS）as codebook is a very ideal method to reduce PMEPR,this method can make the PMEPR of the system at most 2.However,the number of Golay complementary sequences is limited after all,which is far from enough in practical appli-cation.Having correlation property very close to that of Golay complementary sequences,almost complementary sequences may be used as an alternative to Golay complementary se-quences in many applications.At the same time,scholars proposed QAM complementary sequences by combining complementary sequences with Quadrature Amplitude Modulation（QAM）.QAM complementary sequences can simultaneously transmit information using am-plitude and phase,which greatly improves the data transmission rate.Therefore,it is of great significance to study almost complementary sequences and QAM almost complementary se-quences.In this paper,we first proposed a construction of new quaternary almost complemen-tary sequences of length 2^m+2+2^m+1（m≥3）based on non-standard Golay complementary sequences.The research shows that the newly constructed quaternary almost complemen-tary sequence is different from the existing quaternary almost complementary sequence of the same length,thus enlarge the number of almost complementary sequences with length2^m+2+2^m+1（m≥3）.Secondly,based on the newly constructed quaternary almost complemen-tary sequences,new 16-QAM almost complementary sequences and 64-QAM almost comple-mentary sequences are constructed.Finally,the number of these new sequences and the upper bound of PMEPR are given.