A NOMA-based Coordinated Transmission Scheduling Scheme For Distributed Wireless Camera Systems

As wireless camera sensing devices are widely used in environmental monitoring,traffic monitoring,security monitoring and other fields,distributed wireless camera systems are attracting more and more attentions.The actual scenes of many distributed wireless camera systems have the characteristics of dense deployment of camera nodes and high requirements for real-time transmission and image quality.Power Domain NonOrthogonal Multiple Access(PD-NOMA)technology supports multi-channel parallel transmission,which is beneficial for improving the real-time characteristics in dense transmission scenarios.So,applying PD-NOMA to wireless distributed camera systems is a promising method.This dissertation studies how to achieve high-quality multi-image fusion monitoring in a distributed wireless camera system on the requirement of real-time performances.First,a key term named "single-person informativeness" based on the location and angle relationship between the camera nodes and the person in the wireless camera system is defined,which indicates the probability of a single person in an image being identified.In order to improve the accuracy of the model,the security monitoring data set of Baidu is employed to train the environment parameter which is vital to the single-person informativeness model.Then,the information quantity of the fused image is defined based on the location relationship among the camera nodes.Aiming at maximizing the fused quantity of information,on the premise of satisfying the real-time performance and the requirement of identifying all targets in the wireless camera system,a real-time scheduling scheme based on PD-NOMA is formulated by making the nodes grouping policy,the resolution of the camera nodes and the wireless transmission power as control variables.The problem solving is as follows:(1)Under the requirement that all personnel can be identified,a solution which aiming at minimizing image resolution is first proposed;(2)With the above given image resolution,an optimal algorithm which joints nodes grouping and power allocation is designed;(3)By increasing the image resolution greedily and then evaluating the feasibility of the scheduling strategy,a heuristic algorithm is thus obtained for the primitive problem.The experiment evaluation shows that compared with the traditional transmission scheme,the transmission scheduling scheme based on PD-NOMA has better quantity of information and person identification accuracy in the transmitted image,and besides,the higher real-time requirement of the wireless camera systems,the superior of the scheduling scheme based on PD-NOMA.With some typical settings of wireless camera systems,the experimental results show that when the real-time upper bound of the wireless camera system is set as 0.4 second,the quantity of information by the PDNOMA-based transmission scheduling scheme increases by 46.4% compared with the traditional transmission scheme,and the probability of person identification in the image increases from 0.8549 to 0.8919.Besides,the increment rate of the identification probability decreases rapidly with the further relaxation of the upper bound.