Localizing Unknown Inter-Network Interference Sources In LTE Wireless Private Networks For Electric Power Systems

The LTE Power private wireless network for electric power systems is an extremely advantageous communication technology to meet the ever growing technical requirements of smart grids.State Grid Corp.of China has deployed LTE power wireless private networks in more and more domestic cities,however,network interference greatly degrades the network performance.Compared with LTE wireless public networks,LTE wireless private networks reserve enough protective frequency bands,making outside or inter-network interference becomes more crucial than intra-network one.Nowadays,in practical private networks,there exist various kinds of outside interference sources and the interference from the sources is propagated in complex radio environment.As a result,localization of outside interference heavily relies on experienced operator technicians to manually conduct on-site troubleshooting.The troubleshooting process is time-consuming,with low accuracy,and especially hampered by non-line-of-sight signal propagation in the dense urban environment.Therefore,the efficient methods of localizing unknown outside interference sources are urgently needed in operating and optimizing of the LTE wireless private networks.Learning from principles of Radio Direction Finder and the process of manual interference troubleshooting,we present a scheme of localizing outside interference sources by multi-step measuring and gradually approaching interference sources in LTE private networks,which consists of the following steps.Firstly,the search scope of interference sources is determined according to the positions of the disturbed cells,equipment terminals,measurement data and spots of customer complaining in networks.The second step is to model the 3D scenarios in the search scope,so as to support analysis of interference propagation trajectories.Thirdly,iterative searching is employed to gradually shrink the sear-ch area for the interference sources,including planning drive-testing paths and collecting the drive-testing data,analyzing the data characteristics,and using several heuristic rules to narrow the area in which the sources locate.Finally,when the search scope of interference sources is reduced to small enough,the candidates of sources positions are quickly evaluated by using the beam tracing based radio propagation model,and then the interference source positions are selected from these candidates.The ray tracing based radio propagation model takes into account the impact of the geographical environment,e.g.buildings,on the signal propagation,and is able to accurately track the direct transmission,reflection,diffraction and refraction of propagated interference s:ignals.However,it suffers from time-and resource-consuming trajectory pursuing.To this end,we develop a propagation model based on beam tracing.This model has the ability of simultaneously tracking a bunch of multiple rays,and thus reduces the time cost of signal trajectory analysis and speeds up localization of interference sources;this model is also applied in cell-and region-level coverage analysis,and intra-network interference identification.We present several case studies in dense urban environment to demonstrate the model's validity.Finally,we developed a software system for localizing unknown inter-network interference sources in LTE wireless private networks,and took it to identify inter-network interference in the practical LTE power wireless network in a southern city in China.And it is shown that the proposed localization scheme can improve the efficiency of interference troubleshooting in the dense urban areas with high positioning accuracy.Thus,the system is able to provide strong support for the operating and optimizing of LTE power wireless private networks.