Research On The Delay And Routing Characteristic Of Dynamic Optical Satellite Network

In the field of satellite communications, satellite communications capabilities based on microwave transmission gradually cannot satisfy the huge amount of data transmission produced by such as earthquake forecast, Marine, military reconnaissance, observation, environmental protection and explorations. As a high speed and quick information channel, optical intersatellite links(ISLs) based on laser communication technology is an application extension for free space optical communications in the field of satellite communications, and is an importance research branch in the field of modern satellite communications with high capacity demand. The optical satellite network based on wavelength routing(WR) technology through can greatly improve the communication capacity and meet the increasing satellite communications capacity requirements. It is the creation trend of the future satellite constellation network.In optical satellite network based on low earth orbit(LEO) constellation, the insufficient of onboard optical communication terminals would reduce the network connection numbers at the same time which would cause queuing delay and blocking. To address the problem, effective traffic control and high-efficiency routing and wavelength assignment(RWA) method is needed in order to decrease queuing delay and blocking probability. Besides, the Doppler Effect performance at different routing should be analyzed as different routing in the LEO optical satellite network leading to different Doppler Effect performance result in dif ferent interference of network signals.In order to improve the communication resources utilization of the optical satellite network, reduce the network delay and blocking, improve the communication performance of multiple hops link. The paper carried out research in the following aspects.(1) A network capacity model based on the number of intersatellite links was established. Relationship between the number of intersatellite links, available wavelengths and network traffic level was fully considered in this model which also integrating the characteristics of satellite optical networking.The delay tolerance analysis model of LEO optical satellite network was built based on the network capacity model. The problem of network traffic control was resolved by analyzing the performances of network queuing delay and blocking in call-waiting, call-loss and mixing system network through the model.(2) Calculation method of blocking probability in call-loss network was built by theoretical analysis. This new method which considering both the blocking performance of the whole network and the correlation between adjacent links was different from existing methods. The theory of overflow and hierarchical network was employed in this mothod which made the blocking proble m clear and simplified.(3) An ISL Table Informed RWA(IT-RWA) method is proposed to solve the blocking and wavelengths conflict problems. IT-RWA method made the network ISL utilization status available for every satellite network node. Thus the RWA computation effectiveness improves at every satellite, which leading to a lower blocking probability.Result through the simulation of satellite optical network shows that IT-RWA method had a 5%-20% superiority in blocking probability by contrasting with traditional RWA methods and had a 25%-60% less blocking probability increase at the situation of link failure.(4) The theoretical model of Doppler wavelength shift in multi-hop ISLs was established with the assumption that the optical signal from its source satellite to its destination satellite remain in the optical domain. Simulation results show that the model is correct. With this model, Doppler wavelength shift at different routing was analyzed. Then the signal to noise ratio(SNR) caused by Doppler wavelen gth shift in multi-hop ISLs was analyzed. Effect of Doppler wavelength shift depending on the route choice was given. The signal attenuation caused by Doppler wavelength drift accumulated in the communication hop count.The work in this dissertation establishes a preliminary theoretical basis and analysis gist for the design of LEO optical satellite network. And the proposed RWA method which providing efficient resource assignment improves the progress of LEO optical networking. Some work of the dissertation had benefit to other kinds of optical space network.