Research On Chaos Carrier Index Modulation And Multicarrier DCSK Communication

As a new spread spectrum communication technology,chaotic digital modulation not only inherits the abilities of low interception probability and strong immunity to multi-path effect from traditional spread spectrum communication system,but also shows excellent advantages in other aspects.Considering that carrier index modulation helps to improve the bit transmission rate and spectrum efficiency,Differential Chaos Shift Keying based on orthogonal frequency division multiplexing(OFDM-DCSK)is further improved.The peak-to-average power ratio(PAPR)and bit error rate(BER)performances of the new system is continuously optimized.The main innovations and contributions are as follows:(1)Based on carrier index DCSK and OFDM-DCSK,hybrid DCSK(H-DCSK)system is proposed.The in-phase and orthogonal components of the information signals are used to transmit the data-bearing signals based on multi-carrier DCSK modulation and carrier index modulation,respectively.Theoretical BER expressions are derived under two different channels.The PAPR,bit transmission rate and spectrum efficiency of the proposed system are also analyzed.The validity of the theoretical analysis is verified by simulation.The theoretical and simulated results show that although HDCSK system can improve the bit transmission rate and spectrum efficiency effectively,it still has some deficiencies in the BER and PAPR performance.(2)In order to reduce the PAPR of the system in(1),carrier interferometry code is used to compensate the phase of the signals on different carriers.The PAPR comparisons between the proposed system and H-DCSK reveals that the carrier interferometry code can effectively reduce the PAPR of the transmitted signals.(3)On the basis of the system in(2),the power allocation method is introduced to improve the BER performance.At the same time,the BER of the proposed system is optimized by adjusting the powers of signals transmitted on the in-phase and orthogonal channels,respectively.Theoretical BER expressions are derived on different channels.The validity of the theoretical analysis is verified by computer simulation,and the optimal power allocation solution is investigated to make the BER performance of the system optimal.Results show that the BER performance of the system can be greatly improved with the help of the optimal power allocation solution.