Research On Differential Chaos Shift Keying Communication Systems With Code Index Modulation

Chaotic communications have been extensively investigated in wireless communication applications due to their excellent anti-fading and anti-intercept capabilities.Differential chaos shift keying(DCSK)is one of the chaotic communication schemes,which has been extensively researched in various communication scenarios,such as wireless personal area networks(WPANs),cooperative communications,coexisting communication systems and so on.However,DCSK has drawbacks of low spectrum efficiency and energy efficiency,which can't satisfy the demands of modern communications for high data rate and low power consumption.This article studies the DCSK communication systems with code index modulation(CIM)for improving the spectrum efficiency and energy efficiengcy of DCSK.The main works are described as follows:(1)By combining code index modulation with multilevel code shifted DCSK(MCS-DCSK),we propose a new scheme named CIM-MCS-DCSK.Using the indices of Walsh codes as a new transmitted dimension,CIM-MCS-DCSK has transmitted extra information bits as compared to MCS-DCSK,thus the data rate of proposed sytem is improved.Via analyzing the data rate and complexity of CIM-MCS-DCSK,the superiority of the proposed system is proved.We have also derived the theoretical bit error rate(BER)of proposed system and verified them by simulations.(2)A code index modulation short reference quadrature chaos shift keying(CIM-SR-QCSK)is proposed,which combines code index modulation(CIM),short reference(SR)with quadrature chaos shift keying(QCSK).The proposed system employs the indices of Walsh codes to transmit information bits.Compared to QCSK,the data rate of proposed system is enhanced.For better BER performance,we apply the power ecofficients allocation method to CIM-SR-QCSK.In the process of deriving the analytical BER performace,we have got the optimal reference signal-information bearing signal power ecofficent ratio by using convex optimization principle.Finally,the simulations have verified the correctness of theory and proved the effecefficiency tive of optimization method.(3)Ultilizing the orthogonality of Walsh codes,we propose M-ary DCSK based on Walsh codes.By applying the code index modulation into M-ary DCSK,we propose a new scheme named M-ary DCSK with code index modulation(CIM-MDCSK).Using the indices of Walsh codes as information bearing units,the spectrum efficiency of original system is improved.By analyzing the spectrum efficiency and energy efficiency of proposed systems,the superiority of CIM-MDCSK is proved.For optimizing the BER performace of proposed system,we apply the noise reduction(NR)method to CIM-MDCSK.Finally,the simulations verify the performance advantages of the CIM-MDCSK system.