DTN Network Based Available Bandwidth Estimation Algorithm For Space Links

Space information network is a network system based on space platforms as the carrier,which can acquire,transmit and process spatial information in real time.It can provide services for important applications,such as ocean navigation,disaster relief,navigation and positioning,aerospace monitoring and control,and support real-time observation of the earth and deep space exploration.Space information network has the characteristics of long delay,high bit error rate,frequent link interruption and uplink/downlink asymmetry,which make the traditional TCP / IP protocol no longer feasible.Delay/Disruption Tolerant Networking(DTN)which proposed for the space information network is a good choice.In DTN,a bundle layer is introduced to be compatible with different underlying protocols,and to achieve heterogeneous network interconnection.In addition,BP protocol,the bundle layer's protocol,provides a custody-transport mechanism to solve the problem of frequent link interruptions and makes reliable transport of space information network possible.What's more,LTP protocol which is a convergence layer protocol,provides reliable retransmission-based communication to overcome the data transmission problem,under the condition of long delays and frequent interruptions of the link.DTN based on BP/LTP procotol solves the problem of data transmission under the conditions of frequent link interruption,uplink/downlink asymmetry and long delay etc.in space information network.However,the rapid development of space applications poses issues to space networks,and “How to use the limited resources effectively to improve the Qo S” has become a hotspot issue.That's,space network is facing the issue of Qo S guarantee.For network services,Qo S includes network bandwidth,transmission delay and packet loss rate etc.In network,Qo S can be improved through using network bandwidth reasonably,reducing data transmission delay,packet loss rate and delay jitter,and other measures.The available bandwidth is an important indicator of the Qo S,which can reflect the usage of bandwidth resources in the network and the data transmission status in the network.It provides an important reference for the Qo S guarantee.Therefore,this paper studyed the available bandwidth estimation in the space DTN network,and proposed a method to estimate the link available bandwidth for space DTN network.This paper analyzes the bundle transmission process in space environment,and the factors that affect the bundle delivery delay,introduces the M/D/1 queuing model to analyze the queuing process in the bundle transmission,and establishes the mathematical relationship between available bandwidth and related parameters using the maximum likelihood estimation method.Then,proposes an available bandwidth estimation algorithm for space link to estimate the available bandwidth of a link over a period of time.Simulation shows that,the algorithm can estimate the available bandwidth for a space link with a certain deviation.Note that,when the link state is more good and stable,the estimation deviation is more little.While,the space network is characterized by highly dynamic,and link status is time-varying.Therefore,this paper introduces the UKF model,and makes a deep analysis of the relationship between the available bandwidth and the related parameters.Then,we establish the mathematical model,considering the relationship of available bandwidth and transmission parameters.According to the mathematical model,an on-line avialable bandwidth estimation algorithm based on the UKF is proposed.Simulation results show that,the proposed algorithm can follow the change of the available bandwidth of the space link.Compared with the EKF-based algorithm,the proposed algorithm shows stronger tracking and higher estimated-accuracy.