Research On Low-Orbit Satellite Random Access Technology

With the increasing demand for communication and the continuous expansion of new services,as a supplement to terrestrial wireless communication systems,satellite communication systems have gradually become an important part of global personal communication.Low-orbit satellite communication systems have received wide attention since the 1990s because of their small path loss,short propagation delay,and global coverage.At present,the international competition for orbit and spectrum resources is becoming increasingly fierce.It is also urgent to establish China's independent global space-based information system.The Belt and Road Initiative is also promoting the development of the low-orbit satellite communication constellation system.As a key technology of the subscriber access network,the performance of a random access procedure affects the overall stability and LEO satellite system network user experience.LEO satellite as a forwarding node and a ground distance,the longer the delay between satellite-ground communications,and therefore can not be ground LTE random access technology directly to the LEO satellite communication system.In this paper,some researches are carried out on the above issues.The main work includes the following three aspects:Firstly,the characteristics of terrestrial mobile communication system,a random access frame structure applicability LEO satellite communication system,in conjunction with large delay spread LEO satellite systems,a wide range of beam coverage,the random access frame structure design.According to the characteristics of satellite beam arrangement,the random access frame structure design under the layered structure is proposed.Secondly,for the satellite system resources to a physical channel has been divided,in accordance with uplink and downlink transmission frame design,a reasonable allocation of frequency resources available for random access procedure.Analysis of two common backoff algorithm,by retracting the respective characteristics and merits of experimental analysis and simulation of the algorithm,the improved backoff algorithm is proposed to adapt to the complex network environment,and reasonable random access slots and the traffic beam coverage hierarchical structure time slot ratio.Finally,the typical scenario in a mobile satellite beam during the failure of a random access request,and make random access transfer model to reduce such random access performance loss.According to the model requirements,the backoff algorithm is modified to reduce the average access delay of users.The boundary parameters of the design model are determined by simulation,and the random access transfer model is improved.