Research On Differential Chaos Shift Keying In Wireless Optical Communication

Contemporary society has entered the information society of all things,and people have increased the demand for communication rates and capacity.Since the original radio frequency spectrum resources are increasingly tight,in order to achieve resource complementation,it is necessary to find a reliable communication method complementary to radio communication.Wireless optical communication technology enters researcher experiments due to its environmental protection,low cost and rich spectrum resources.Indoor visible light communication and laser communication under free space are important parts of wireless optical communication technology.In this paper,in order to solve the poor performance in Non-sight link single-input single-output indoor visible light communication system and the communication security problem in the OAM multiplexed communication system,Application of DCSK modulation techniques in indoor visible optical communication systems and OAM multiplexing systems,and corresponding system performance are studied.Firstly,the modulation process of the DCSK modulation system is studied,analyzing the initial value of the DCSK time domain signal and the self-cross-correlation characteristics,providing the theoretical basis for the DCSK modulation system.Under the Gaussia White Noise Channel,the DCSK system error rate curve was completed and the choice of the most optimal spreading factor was selected.Secondly,in view of the communication security of the indoor visible light communication system and the weak signal at the receiving end,it is proposed to study the DCSK technology in the indoor visible light communication system,and two optimization methods for the system receiving detector are proposed.System communication process is analyzed in detail.The indoor visible light non-line-of-sight link channel is modeled,and the channel impulse response under different positions is obtained.In order to overcome the multipath channel fading,the single-input multiple-output angle diversity receiving method was introduced,and the channel models under different receiving methods were compared and analyzed.The performance of each system is measured by the bit error rate,and the angle diversity system is optimized for the problem of long delay and small peak of channel impulse response.The method of elevation angle optimization and optimal detector selection improves system performance and reduces the system's bit error rate by two orders of magnitude when the signal-to-noise ratio is 10d B.Finally,in order to improve the performance of the OAM beam multiplexing system,it is proposed to study the DCSK technology in the OAM beam multiplexing communication system.The common beams of OAM are introduced and the beam characteristics of LG beams in free space are analyzed.The system process is described in detail,and the basic theory of atmospheric turbulence is introduced.On this basis,the spectrum inversion method and the tilting screen compensation method are discussed.The latter is selected to generate a random phase screen and the atmospheric turbulence channel is modeled.The LG beam distribution characteristics under the atmospheric turbulence channel are given and compared with the ideal channel.Simulation and analysis of the bit error rate curve under different turbulence intensities and different spreading factor lengths when the system adopts the DCSK modulation technology.The results show that the bit error rate of the system can reach about 10^-6 at 0dB under Moderate and weak turbulence.