Research On Cooperative Information Fusion Technology Of Mountain Search Based On Wireless Ad Hoc Networks

In recent years,fire,earthquake,aircraft crash and other emergencies occur frequently.Timely and accurate disaster detection and victim search are key issues of emergency missions.The complex geographical environment,low coverage of base stations and severe occlusion in mountains,combined with the damage nature of fire and earthquake,bring great challenges to manual or single UAV search.Compared with manual or single UAV search,multi-UAV cooperative mountain search can not only avoid casualties,but also detect the same area from different angles and make full use of the spatial diversity of observations to improve the accuracy of detection.The information obtained by different UAVs needs to be integrated by information fusion technology.The performance of information fusion directly affects the performance of emergency search.Wireless ad hoc network provides support for autonomous cooperative information fusion of multi-UAVs in mountain environment,but also brings constraints such as communication delay and error.Considering the characteristics and needs of emergency search in mountains,this paper studies cooperative information fusion technology based on wireless ad hoc networks,which provides information support for rescue decision-making.Main research contents of this thesis are as follows.1.Considering the amount of transmitted data,we analyze and compare the characteristics and performance of information fusion technology at different levels,which provides guidance on the choice of information fusion level for mountain emergency search.According to the level of information fusion,information fusion technology is further divided into data-level fusion,feature-level fusion and decisionlevel fusion.The characteristics and performance of different levels of fusion are different.The performance of information fusion based on digital communication system is affected by the amount of transmitted data.Based on the binary hypothesis test problem,we analyze and compare the characteristics and performance of information fusion technology at different levels under the constraint of limited transmission data.It is shown that when the amount of transmitted data is not less than 2bits,the performance of data-layer fusion is always better than that of feature-level and decision-level under different detection channel conditions.Based on the high demand of accuracy for emergency search,we choose the data-level fusion as the basis of further research.2.Considering the ideal communication environment first,we establish system model and performance models of distributed cooperative data-level fusion,to provide support for the selection of search network parameters for the demand of emergency search accuracy and real-time.In mountain areas,the obstacle occlusion is serious,which may cause some nodes to enter the communication blind area and unable to participate in the cooperation.For centralized fusion,if the fusion center is in the communication blind area,the whole system may be unusable.Distributed cooperative fusion is not limited by a single fusion center and is more suitable for mountain environment.This paper studies distributed cooperative data-level fusion.Considering the requirement for accuracy and real-time of emergency search,the closed performance model of fusion accuracy and time delay is established by assuming the ideal communication environment,and the relationship between parameters and performance is analyzed.It is shown that the network connectivity can be increased as much as possible to reduce the fusion delay in the ideal communication environment.3.Further analyze the influence of non-ideal communication factors on the performance of distributed cooperative fusion,such as packet loss and error,and design the distributed cooperative data-level fusion algorithm which is more suitable for nonideal communication environment.In mountain areas,the communication error and packet loss are serious,which directly affect the fusion performance.In this paper,the influence of non-ideal transmission environment on information fusion performance is studied.The information fusion algorithm based on the mixed-weight of detection channel and reporting channel quality is designed to mitigate the impact of non-ideal communication environment.It is shown that in the non-ideal communication network of 10 nodes,when the false alarm rate is 10%,the proposed algorithm can improve the fusion accuracy by more than 20%.