Simulation Design And Performance Analysis Of Satellite Communication System Based On OPNET

According to orbit altitude,satellite communication system can be divided into the geostationary(GEO)satellite system,the medium earth orbit satellite system(MEO)and the low earth orbit(LEO)satellite system.The main advantages of LEO are seamless global coverage,capability to reuse frequency more effectively and small propagation delay.Based on a practical project,i.e.A LEO satellite communication system project,this paper does research on design and development of OPNET based system level simulation platform and meanwhile verifies the communication protocol.By analyzing the basic communication scenario and the design of key parameters of the physical layer of A LEO satellite communication system,the network structure and the mechanism of communication and synchronization between nodes in the simulation platform are designed according to constraint conditions.Furthermore,the model of satellite,subscriber station(SS)and gateway station(GS)are designed,and a basic communication scenario is adopted to verify and analyze the performance of the platform.Specifically,the main innovations of this paper can be included as follows.Firstly,a design scheme of satellite communication simulation platform based on OPNET is proposed.The operational principle and modeling process of OPNET are discussed at first,then this paper introduces the detailed functions and constraints of A LEO satellite communication protocol stack.Later we talk about the structure of the simulation platform and the starting up process of the simulation platform,and a time-slot driven mechanism is proposed to synchronize nodes in the platform at the same time.divides simulation time into continuous time slots,and allocates slot number for each time slot.A method to generate orbit files based on STK is also worthy to be discussed.Secondly,specific node models and a process models are implemented based on the designed platform.After discussing the protocol function,we designed the nodes of this platform,they are subscriber station nodes,gateway station nodes,satellite nodes and network configuration nodes,different state transition models are allocated for them respectively.Finally,in order to verify the reliability of the simulation platform,a strategy of dynamic resource allocation is proposed and implemented.In the test communication scenario,resource allocation success rate,throughput and packet delay under different profile intensities are analyzed.Results prove that the simulation platform has good versatility and flexibility,and it can evaluate the performance of satellite communication protocol in an all-round way.