Research On Dynamic Handover Decision Algorithm Based On Fuzzy Logic Control In FSO Network

Because of high bandwidth,large communication capacity,and strong security,free space optical communication(FSO)has become one of the hotspots in the field of communications.With the development of grid information network,point-to-point FSO systerm is not able to support continuing information transmission of the network,the research on FSO networking is more and more significant.Acquisition,Pointing,Tracking(APT)is indispensable for handover in FSO networking.With the increasing communication distance and speed of mobile nodes,the demands for establishing a communication link rapidly based on APT becomes more strict.In order to overcome the problems including long acquisition time and large uncertain region of APT,when the speed of mobile nodes is fast in FSO network,this paper proposes a fast acquisition technology based on the error correction extended Kalman filter(EC-EKF)algorithm.The EC-EKF algorithm is used to filter the initial location information from GPS,which improves accuracy of location information,and reduces the uncertain region.Then according to the filtered location information,APT adjusts the optical antenna to establish communication link by acquiring beacon of opposite node.When the communication link is interrupted,the EC-EKF algorithm predicts the upcoming motion of opposite node based on the opposite node's historical location information.APT conducts reacquisition according to the predicted result.Through the theoretical analysis and simulations,it is proved that the proposed technology can improve the accuracy of location information,and reduce error between the predicted result and actual trajectory,which achieves the purpose of optimizing acquisition.Moreover,when the node is moving in the FSO network,in order to maintain timely reliable communication,it is necessary to eliminate unnecessary handover and ping-pang effect.Although there are many research achievements of handover in mobile RF wireless network,the differences between RF and FSO communication make it impossible to apply existing handover algorithms of mobile RF wireless network to FSO network directly.After analyzing characteristics of optical link,this paper proposes a dynamic handover decision algorithm based on fuzzy logic control which is suitable for FSO network.In this algorithm,the predicted location information of mobile node is utilized to estimate intensities from various received optical signals rather than one optical signal.Then on the basis of fuzzy logic control system,the optimal access cluster head is chosen among candidate access cluster heads to build the new link with the mobile node according to the receiver power,relative movement,and access degree of cluster head.Through the theoretical analysis and simulations,it is proved that the proposed algorithm can significantly reduce the handover times in FSO network,and avoid the ping-pong effect.