Research On Code Index Modulation Techniques In Direct Sequence Spread Spectrum Communication

Index modulation is a kind of new wireless communication modulation technology proposed in recent years and it has a wide prospect in the future.The current study of the results of index modulation is mainly focused on antenna index modulation(spatial modulation)and subcarrier index modulation,and code index modulation based on direct sequence spreading spectrum(DSSS)has just begun to be studied by academies.Spread spectrum communication is an important communication system that has been widely used in many fields.Researches on code index modulation(CIM)has great practical significance on accelerating the development of index modulation theory and enhancing the application value of spread spectrum technology.Traditional spread spectrum modulation technology has some disadvantages,such as low transmission rate and the decrease of spectrum efficiency that hinders the antijamming performance.To a certain extent,the CIM alleviates this situation,but it has to consume a large number of index resource at the expense and transmit few information bits.In order to solve the above problems,this paper proposes two different schemes of code index modulation.To solve the problem of using a lot of pseudo noise(PN)codes,this paper puts forward a scheme of block mapping code index modulation.This scheme sets multiple modulation sub-blocks in parallel to modulate independently,at the same time,it picks up PN codes that are needed in modulation block intensively,and then spread the modulation symbol after being sequenced by the index value.The result indicates that the scheme uses less PN codes than the former CIM scheme at the same transmission information bits.In order to solve the problem that the number of transmission bits via invisible method is less in CIM,a two-dimensional space code orthogonal index modulation scheme is proposed.The scheme increases the number of recessive transmission information bits with two-dimensional index,and makes the antenna index resource and the PN code index resource reused via orthogonal mapping method while its bit error rate performance is not lower than other traditional index modulation schemes.This paper solves the problem of consuming a lot of index resource and few transmission information bits by introducing block mapping mode and increasing the number of index resources in CIM.It relieves the contradiction between the anti-jamming performance and spectral efficiency in spread spectrum system,and provides theoretical reference and technical support for further study of direct sequence spread spectrum code index modulation.