Design And Detection Of SCMA Irregular Codebook

In the era of big data,communication technology is constantly undergoing rapid changes.From the primary communication stage in the 19 th century to the modern communication stage,every great change in communication technology promotes great changes in the whole society.After the replacement of four generations of mobile communication technology,5G communication has become a very important research topic at present,which bears the vision of promoting the Internet of Things society.Traditional communication technology can not meet the requirements of massive data connection and high-speed data transmission,so sparse code multiple access(SCMA)technology came into being.SCMA technology is a non-orthogonal multiple access technology for the 5th generation mobile communication system,which has high system spectrum efficiency,high forming gain and other characteristics.Its characteristics benefit from the sparse mapping method of SCMA technology.SCMA technology obtains multidimensional constellation shaping gain in codebook design by mapping user data bits directly into multi-dimensional complex code words,and superimposing and transmitting the information of multiple users at the sending end.However,the limitation of SCMA system in the number of accessed users and the sacrifice of bit error performance follow.In this thesis,an irregular SCMA mapping method is designed to solve the problem that the traditional SCMA system can only transmit the number of users satisfying the uniform allocation condition.By constructing factor matrix and mapping matrix,this method establishes constellation matrix which is suitable for various access users,so as to map user information.At the same time,based on the theoretical framework of Star Quadrature Amplitude Modulation,a design method of Rotating Interleaving Irregular(RII)is proposed in this thesis.This method reconstructs the basic constellation based on the rotary interleaved codebook,and optimizes the rotary interleaved codebook by traversing the rotation angle of the basic constellation,so as to obtain better codebook performance.Finally,based on the irregular SCMA mapping method,this thesis improves the traditional SCMA detection algorithm and proposes an Irregular Log-MPA(IR-LogMPA)algorithm.This algorithm uses different methods to calculate the probability of user information with different resource blocks,which complements some invalid operations of traditional Log-MPA algorithm and increases the error performance of irregular SCMA mapping method without increasing the complexity.The results show that the three methods proposed in this thesis effectively improve the applicability of SCMA system and reduce the bit error rate of multiuser detection.