Design And Performance Analysis Of DCSK Communication System Based On Carrier Index Modulation

Chaos-based digital modulation replaces the sinusoidal carrier in traditional digital modulation with the non-periodic broadband chaotic signal,and thus shows superiorities in anti-interference,anti-multipath fading,high communication security,low power consumption and low hardware cost.In view of low energy and spectral efficiencies in existing carrier index differential chaos shift keying systems,three multi-channel carrier index differential chaos shift keying systems are proposed.The main work of this thesis is as follows:(1)Based on the existing carrier index differential chaos shift keying system,a two-channel carrier index differential chaos shift keying modulation system without polarity modulation is proposed,which performs index modulation twice on the same carriers to reuse the carrier resources,resulting in improved system spectral efficiency and higher bit transmission rate.In order to avoid interferences between two carrier index modulation signals,orthogonal signals(i.e.,chaotic signals and their Hilbert transform signals)are used as references in the first and second index modulations.The bit error rate performance,energy efficiency,spectral efficiency and system complexity are analyzed.Monte Carlo simulations are performed to verify the accuracy of our theoretical performance analysis.Results show that the new system shows lower system complexity,better bit error rate performance and higher energy and spectral efficiencies in comparison with the existing carrier index differential chaos shift keying system.(2)To further improve the bit transmission rate of the system proposed in(1),polar modulation is introduced into the system in(1),then,a new two-channel carrier index differential chaos shift keying system is proposed,the data of each channel is transmitted not only through the index of the carrier,but also through the polarity of the signal.The bit error rate performance,energy efficiency,spectral efficiency and system complexity are analyzed.Monte Carlo simulations are performed to verify the accuracy of our theoretical performance analysis.Compared to the system in(1),the system shows higher spectral efficiency and lower system complexity with the same energy efficiency.Simulation results show that the new system has better bit error rate performance.(3)In order to further improve the energy and spectral efficiencies of the systems in(1)and(2),a three-channel carrier index differential chaos shift keying modulation system is proposed,where signals in two layers are transmitted in three carrier index modulation channel and the reference for one layer can be found in the other layer..Unlike systems proposed in(1)and(2),three-channel carrier index differential chaos shift keying system eliminates the traditional reference signal(i.e.,signals transmitted in each layer not only carry the information bits but also serves as the reference signal of the other layer),resulting in greatly improved energy efficiency.The bit error rate performance,energy efficiency,spectral efficiency and system complexity are analyzed.Monte Carlo simulations are performed to verify the accuracy of our theoretical performance analysis.Compared with systems in(1)and(2),this new system has higher energy and spectral efficiencies.Simulation results show that the system has better bit error rate performance.Carrier index modulation can not only simplify the hardware structure of the system,but also demonstrates incomparable advantages in energy efficiency,spectral efficiency and bit error rate performance.Therefore,it is of great theoretical and practical significance to study the chaotic digital modulation system based on carrier index modulation.