Study On Scattering Communication System Based On Pulse Laser

Compared with traditional communication,wireless optical communication has attracted more and more attention in recent years.Non-line-of-sight(NLOS)ultraviolet(UV)optical communication belongs to wireless optical communication technology.The optical signal at the transmitting end passes through the scattering effect of molecules and particles in the atmosphere.This kind of signal arrives at the receiving end through non line of sight transmission,so that the transmitting end and the receiving end do not need to be aligned.The longer distance NLOS UV communication can be realized by using pulse laser at the transmitter The contents of this paper mainly contain the design of pulse location algorithm,synchronization sequence and channel coding in the scattering communication system of pulse laser.We propose pulse laser-based ultra-violet(UV)communication over long distance,such that the pulse response signals can be detected at the receiver at the cost of low data transmission rate.We describe the long distance NLOS communication channel model,through Monte Carlo multiple scattering simulation pulse broadening,the results prove the feasibility of 5km scattering communication in theory,and we provide the communication system diagram.We adopt Z-channel model to characterize the received signal,which is validated by real experimental measurements.and analyze the performance for the pulse laser-based UV communication under consideration.Since the detection performance critically depends on the pulse response position estimation,we propose two approaches to estimate the pulse response positions,one based on counting the number of pulses in a window,and the other based on the correlation of pulse response shape and the number of detected photoelectrons.It is seen that the correlation-based pulse position estimation approach is more accurate compared with the counting-based one.We propose to optimize the frame synchronization sequence for the Z channel under consideration.For the optimization of synchronization sequence in Z-channel,by making the probability of bit 1 and bit 0 at the transmitter meet the optimal input distribution respectively,and the probability of bit 1 and bit 0 at the receiver after the channel is 1/2,It can be observed that the optimized frame synchronization sequence can lead to a higher correlation peak compared with the standard m-sequence.We also propose to optimize the codebook for the channel under consideration.we design a nonlinear code based on the upper bound of decoding error probability.Then the existing flip codes are described and simulated,the genetic algorithm is used to solve the nonlinear coding optimization problem.It is shown that the optimized codebook shows lower decoding error rate up to one order of magnitude compared with flip linear code.