Design And Implementation Of Transmission Protocol On L2 In LTE-Based Satellite Systems

Satellite communication system is the expansion and extension of terrestrial communication systems,and mutual integration for terrestrial and satellite communications has become a trend.Therefore,the integration task of satellite-ground is more urgent and realistic.At present,with the rapid evolution terrestrial mobile communication systems arrive at 4G-LTE stage.The world has started a research on satellite mobile communication systems based on LTE technology.With support of 863 major projects,this paper actively carries out a research and design of layer L2 transmission protocol in satellite LTE systems.The main work is as follows:1.Considering the characteristics of long transmission delay and limited resources in GEO satellite,with further study of real-time scheduling M-LWDF algorithm,we propose a cross-layer based resource scheduling algorithm for the adaptation of large delay environment.In the use of cross-layer design,the algorithm introduces delay judgment factor which thinks over the required delay on MAC layer.In addition,Q factor representing traffic priorities on application layer is introduced.Resource scheduling mechanism is optimized with the combination of delay judgment factor and Q factor,efficiently improving resource utilization for GEO satellite communication system.Simulation results show that compared with M-LWDF algorithm,the algorithm can reduce the communication delay and improve system throughput.2.Channel are of good quality in GEO satellite,therefore,this paper proposes a single-layer low delay retransmission mechanism(SL-HARQ)by simplifying double-layer retransmission in terrestrial mobile communication systems.The mechanism reduces feedback retransmission process in RLC layer from the original double-layer retransmission,and gives full consideration of correlation between the number of channels and RTD.Moreover,it sets a reasonable number of channels and threshold for numbers of transmission,maximizing channel utilization and improving system throughput.Simulation results show that compared with the double-layer retransmission mechanism,the method ensures the reliability of satellite communications with lower complexity and higher throughput.3.Considering the demand of high-throughput in satellite LTE communication systems,we expand the bandwidth delay product,and accordingly modify sequence number field of acknowledged mode protocol data unit(AM PDU)in RLC layer for terrestrial LTE system.Furthermore,RLC protocol in GEO satellite system is designed suitably.Finally,the designed AM PDU is used in GEO satellite communication systems.On the basis of experiment in satellite-ground simulation systems,this paper designs protocol analysis software,which coordinates the completeness of traffic presentation in the whole system,and analyzes the correctness of traffic signaling exchange mechanism and processes.