Channel Modeling Technology For Scattering Non-Line-of-Sight Underwater Wireless Optical Communications

Scattering non-line-of-sight(NLOS)underwater wireless optical communications(UWOC)realizes information transmission by using the forward scattering effect of randomly distributed particles.It is extremely valuable in the fields of underwater internet of things(IOT),concealed anti-jamming tactical communications and networking.Setting up an accurate,simple and suitable channel modeling scheme for underwater scattering communication scenes is the key to obtain the channel characteristics,as well as the premise of building underwater scattering communication system.On the one hard,the existing single scattering channel modeling schemes are not easy to simultaneously satisfy the requirements of high accuracy,low complexity and universality at the same time.Thus it is necessary to build a new modeling scheme.On the other hand,because of the time-varying caused by the movement of the transceiver and the randomness caused by the flow of water,the channel characteristics of multiple scattering are greatly affected.Therefore,the modeling scheme and channel characteristics of multiple scattering stochastic time-varying channel need to be studied.A modeling scheme based on the idea of micro-element is proposed for the underwater NLOS single scattering channel.In the scheme,the irregular effective scattering volume is divided into several unrelated regular volume elements.Then,the contribution of each volume element to the receiver power is accumulated to achieve the channel characteristics.The numerical results show that the proposed scheme achieves the comparable performance to the triple integration modeling scheme,which accurately describes the boundary of the effective scattering volume.The error is within 0.5 dB.Also,it shows higher accuracy compared with the approximated modeling scheme which utilizes a single regular scattering volume to model the effective scattering volume.Compared with the triple integration modeling scheme,the proposed scheme has a simple modeling process,which does not need to calculate the complex upper and lower bounds of the integration.It is suitable for the configuration of various transceiver parameters,and can unify the coplanar and non-coplanar scenarios of the transceiver pointing.Aiming at the underwater NLOS multiple scattering channel,monte-carlo simulation(MCS)algorithm based on probability statistics is analyzed in this thesis,and a multiple scattering stochastic time-varying channel modeling scheme is proposed.This method uses random numbers drawn from a uniform distribution to simulate the motion trajectories of photons,and solves the channel characteristics through the statistical average of multiple test results.The simulation results show that the time-varying increases the path loss,but hardly causes the delay broadening.The randomness of the receiving pointing will affect the path loss and the time delay width simultaneously.Compared with the channel characteristics that does not consider the randomness of receiver pointing,the randomness of receiver pointing will cause the path loss value to increase by more than 10dB.At the same time,the delay broadening will increase to 1.5 times.This thesis also studies the stochastic time-varying channel characteristics under different field-of-view(FOV),and the simulation results can provide some guidance for the design of underwater scattering communication system.