Research On Code Index Modulation Scheme Based On Direct Sequence Spread Spectrum

Index modulation is a kind of wireless communication technology that has emerged in recent years and has a good development prospect in the future.At present,the research of index modulation mainly focuses on spatial modulation and index modulation of subcarriers,but there is relatively little research on code index modulation of direct sequence spread spectrum.As an important communication technology,spread spectrum communication has been widely used in many fields.The research of code index modulation scheme based on direct sequence spread spectrum has certain reference value for the theoretical development and practical application of push code index modulation and spread spectrum communication.Traditional spread spectrum modulation techniques have some disadvantages such as excessively large frequency bandwidth and low spectral efficiency,but code index modulation technology can effectively improve the system's spectral efficiency and energy efficiency.The disadvantage is that code index modulation is based on the need to consume a large number of index resources,and the bit error rate performance will decline.In order to solve the above problems,this thesis proposes two different solutions.To deal with the problem that code index modulation should consume a lot of pseudo noise?PN?code resources when it increases the information transmission rate by increasing the number of mapping bits.This thesis proposes a novel generalized code index modulation?GCIM?.What's more,by increasing the number of the activate PN code of per transmission slot,which can increase the number of mapped bits and improve the spectral efficiency and energy efficiency of the system.The simulation and analysis results show that it is not better than CIM about 2dB in the additive white Gaussian noise channel and about 1dB in the Rayleigh fading channel at the same spectral efficiency.Nevertheless,compared with CIM,GCIM consumes significantly less PN code resources.To deal with the problem that the bit error rate reduced obviously when using the code index modulation to improve spectrum utilization compared with the direct sequence spread spectrum,a novel non-orthogonal-code index modulation?N-CIM?was proposed.The bit stream of the transmitter is divided into mapping block of pseudo noise code and informational block of modulation,which are mapped into the index of the PN code and modulation symbol respectively.The real part and imaginary part of the modulation symbol spread spectrum by selecting the identical activate PN code respectively.Simulation and analysis results show that,compared with CIM,the bit error rate of N-CIM has improved about 2-3 dB in additive white Gaussian noise channel when the bit error rate is 10^-5,and the bit error rate of N-CIM has improved about 2 dB in Rayleigh fading channels when the bit error rate is 10^-2 at the same spectral efficiency.In this thesis,the idea of parallel combination spread spectrum was introduced in code index modulation to alleviate the shortage of excessive PN code resources was spent on code index modulation and further improves the system's spectral efficiency.To introduce the idea of spatial modulation alleviates the poor BER performance of code index modulation and simplifies the structure of the entire modulation and demodulation system.In addition,this research has a certain reference value for the further study of code index modulation based on direct sequence spread spectrum.