DCSK Modulation In Optical Wireless Communication Study On ACO-OFDM-IM Technology

Contemporary society has entered the Internet era of the Internet of Everything.Speed,capacity,and security are the most important needs to be considered in the development of the communication industry.For mainstream radio frequency communication,it needs to occupy increasingly tight spectrum resources,and development is easy to encounter bottlenecks.Under this demand,the optical wireless communication technology（OWC）which is environmentally friendly and energy-saving,has abundant spectrum resources,and low cost,and the Chaos Communication technology with high communication accuracy and safety has entered the field of vision of researchers.At present,mainstream optical wireless communication systems are susceptible to the influence of the channel,which leads to system performance degradation,and cannot make good use of the advantages of optical communication.However,chaotic communication has excellent characteristics such as strong anti-interference ability of traditional spread spectrum communication.Therefore,chaotic communication is applied to optical communication.Wireless communication can optimize system bit error performance to meet communication needs.Differential Chaos Shift Keying（DCSK）is one of the technologies widely used in chaotic communication.It belongs to non-coherent communication.It not only has the advantages of chaotic communication,but also has a simple structure and high confidentiality.This paper first aims at the problems of bit error performance in optical wireless communication,introduces DCSK modulation into optical wireless communication system,combines with carrier index asymmetric clipping optical orthogonal frequency division multiplexing（ACO-OFDM）technology,utilizes low bit error rate and anti-multiplexing The chaotic modulation with superior path performance is used to make up for the shortcomings of optical wireless communication;secondly,the overall spectral efficiency and transmission rate of the system are optimized by using differential indexing technology and improving DCSK signals.The main research content of this paper is as follows:（1）Apply DCSK modulation in radio frequency to optical wireless communication multi-carrier indexing system to construct ACO-OFDM-IM-DCSK system,which can effectively solve the problem of the bit error performance of traditional optical communication system in small signal-to-noise ratio,complex channel,especially the turbulent channel is low.Through simulation analysis,the ACO-OFDM-IM-DCSK system is compared with the traditional ACO-OFDM-IM system in optical wireless communication.When the signal-to-noise ratio is small,the system bit error performance is better.Larger optimization,when the bit error rate is 10^-4,the channel of weak turbulence can be improved by about 2d B and the channel of strong turbulence can be improved by about 2.5d B;（2）Compared with the traditional ACO-OFDM-IM system,the ACO-OFDM-IM-DCSK system can effectively improve the bit error performance,but it cannot optimize the transmission rate and spectral efficiency of the optical wireless communication system.Therefore,this paper considers two aspects to improve.The first is to start with the position between sub-carriers,introduce carrier difference index technology,build an ACO-OFDM-DIM-DCSK system,increase the utilization rate of sub-carriers by reducing silent sub-carriers,and increase the system carrier utilization rate by 37.5%on average in an ideal state;secondly It starts with the signal,improves the DCSK signal,expands the signal from the real number domain to the complex number domain to construct an efficient DCSK signal,and applies it to the ACO-OFDM-IM-DCSK system,using the real number reference signal and real number information signal to carry additional complex numbers domain information signal,increase the amount of information in the unit carrier,and increase the original 1-bit DCSK signal to 3 bits.In the（4,1）carrier index mode,the overall transmission rate and spectral efficiency of the system can be increased by 66.7%,further optimizing the performance of optical wireless communication systems.