Research On Access Technologies Of Dynamic Users In Space-based Network On Account Of Traffic Priority

With the rapid development of communication technology,most activities of human is not only based on earth,but also involves satellite,or combines with all kinds of application systems of satellite,which is associated with the concept of “Integration of Space and Terrestrial”,in which the space-based network is made up of aircraft,spacecraft and all kinds of satellites in different orbits,which is hierarchical and tridimensional.The characteristics of space-based network including power limitation,short communication time,enormous traffic data and intact data communication require that the space-based nerwork must offer reliable and guaranteed access,therefore,how to utilize space ommunication resources effectively to insure the QoS of different terminal users becomes the key problems to be solved in access algorithm of MAC layer.Consequently,we need to design reasonable access schemes aimed at the features of space-based system to improve the throughput,decrease the energy comsuption,reduce the collision probability and delay and realize excellent communication of users.This paper analyzes the background and the significance of the application of access technologies in the space-based network.It also analyzes the current development and future research directions of the space-terrestrial communication system,space-based network and access protocol.Then,the framework of the space-terrestrial communication system is studied,including access scenario,business type,access priority and common access protocol.And then,there are mainly two aspects of research.Firstly,aimed at the future demand of the construction of space-based network in our country,a structure model is designed that is a GEO/LEO double-layer network by appliying the “backbone/access” model,which is simple and efficient and provides background and an application platform for the research of specific access schame in the context.Secondly,in order to save energy consumption,we propose an adaptive energy access scheme based on traffic priorities,which improved the traditional satellite cluster scheme named LEACH,at the same time,we improved the satellite cluster scheme further,which is depending on the type of traffic and the length of transmission link to allow or deny the establishment of transmission link to reduce energy consumption and increase the sevice life of satellite.At last,in view of the long-distance communication in spacebased network and in order to maintain the flexibility and extensibility of the communication,an improved MF-TDMA hybrid access scheme in space-based system is raised,which adopts the combination if frequency division and time division,in the frequency domain,we utilize OFDMA technology,and in the time domain,we make use of the improved CSMA/TDMA hybrid multiple access protocol with considering different traffic priorities to meet the transport needs.Simulation results show that,the hybrid access protocol in frequency-time-division multiple access regime can realize dynamic adjustment of channel resources and hige utilization of bandwidth,whih can also offer better performance in networking and integrated business transmission compared with the traditional access protocol,because that the novel access scheme proposed can improve throughput,decrease delay and collision probability.In a word,the two access schemes proposed in this paper can improve the transmission performance of the network according to the characteristics of the space-based network.