Research On Satellite Assisted Multi-group Multicast Technology And System Level Simulation

In order to realize the requirements of 5G Internet of Everything and the beautiful vision of 6G ubiquitous connection,satellite communication technology has been widely studied.The satellite network has an extremely wide coverage,and has the ability to exchange information with innovative equipment such as UAV.Besides,satellite can provide emergency communications.However,the current research on satellite communication,including the satellite channel propagation characteristics,the integration with terrestrial system,and the research on satellite resource management scheme,still have certain limitations.Therefore,this paper investigate the satellite communication system from two aspects of theory and practice.For the theoretical aspect,this paper analyzes the multi-group multicast performance of a satellite-assisted cell-free Multiple-Input Multiple-Output(MIMO)system,and explores the ability of satellites to relieve ground pressure and increase data transmission rates.From the practical aspect,this paper simulates the satellite communication system based on the Digital Video Broadcasting-Return Channel by Satellite second generation(DVB-RCS2)protocol,achieving deeply understand of the composition of the satellite system and realizing the full utilization of limited satellite resources.Firstly,this paper introduces cell-free massive MIMO system,comparing it with centralized and distributed massive MIMO.Then,we summarize the existing satellite communication systems.Meanwhile,the satellite channel characteristics,channel models and common communication protocols are investigated.Then this paper elaborates content in DVB-RCS2 protocol,with access technology,resource request scheme and traffic model,which lays the foundation for subsequent simulation research.Then,for the problem of excessive ground communication pressure,this paper use satellite-assisted and multi-group multicast mechanisms to relieve ground traffic pressure and improve data transmission efficiency of cell-free massive MIMO systems.Then we propose to estimate channel state information(CSI)by common pilot scheme.Given the estimated CSI,we derive the closed-form expressions of achievable rate with maximum ratio transmission(MRT)and zero-forcing(ZF)precoding.The correctness of the closed-form expressions is verified through simulations.The results show that with the help of satellite and multicast,the average system spectrum efficiency can be significantly improved.Finally,faced with the problem of limited satellite resources,in order to achieve full utilization of resources,this paper has established a transparent transmission satellite communication system based on the DVB-RCS2 protocol.By reasonably configuring the dynamic Multi Frequency-Time Division Multiple Acess(MF-TDMA)frame structure and the resource request mode,Demand Assignment Multiple Acess(DAMA)strategy is used to count and calculate the Return Channel Satellite Terminal(RCST)resource request amount,and the Network Control Center(NCC)performs frame selection,resource pre-allocation,symbol sharing,and time slot generation processes to reasonably allocate resources for RCSTs.Finally,we conduct the simulation of satellite communication system on the Satellite Network Simulator 3(SNS3)platform,realizing the full utilization of resources under the guarantee of fairness.