Optimization Of Routing And Measurement Of Available Key Rate In Quantum Cryptography Communication Network

Quantum communication has entered the stage of large-scale networking with the rapid development of quantum communication technology.Therefore,optimizing the performance of quantum cryptography communication network is meaningful for both the expansion of network and rational use of network resources.Routing algorithm is one of the important research contents in network scale expansion.The key utilization can be improved and the network resources can be optimized by the reasonable routing algorithm.As quantum key is an important resource in quantum network,the utilization and rate of it are also important parameters of network performance optimization.In this thesis,we focus on the optimization of random routing algorithm of quantum cryptography communication network,and the measurement method of end-to-end available key rate.Firstly,the current research status of quantum communication and the significance of the work are summarized.Secondly,we introduce the architecture of quantum cryptography communication system and the basic theoretical knowledge used in this research.Thirdly,we research on the quantum cryptography communication network based on trusted relays,and the main contributes are as follows:1.The random routing algorithm of quantum cryptography communication network based on trusted relays is improved.In addition to adding all the shortest paths to the routing table,the improved algorithm can increase the backup paths of different hops according to the network topology size,and solve the problem of data loop between two nodes.The performance of different algorithms is simulated and the results show that the improved algorithm can further balance the load of the whole network,optimize the network resource,and improve the network security to a certain extent.2.Two methods are proposed for measuring the end-to-end available key rate.In the current measurement method based on one-way-delay,if there is an error occured during the judgment of the delay trend,it will cause a large error of measurement results.In order to make up for the shortcomings of traditional methods,we put forward an measuring method based on readjusting convergence range.This method determines whether to adjust the convergence range and sending rate according to the relationship between delay trend and convergence interval size.The readjusting process improves the accuracy,but increases the convergence time.In order to shorten the convergence time,we further improve the method.At the beginning of measurement,it sends the variable rate packet group in order to determine the approximate range of available key rate,then it determines whether to adjust the sending rate combined with the rules of reajusting the convergence interval for making up for the possible error of delay judgment.The simulation results show that the new method of accelerating convergence can not only measure the available key rate effectively,but also reduce the error and shorten the measurement time compared with other methods.At the end of the thesis,we summarize the works and put forward the prospect of the following work.