Research On Cache Placement Strategy And Transmission Mechanism Of Satellite-terrestrial Communication Network

With the development of terminal technologies such as wireless communication and mobile Internet,mobile traffic has exploded and users have enjoyed higher quality Internet access services.However,there are still some users in the world who cannot access the Internet.Most of these users are in remote areas,so it is less economical to deploy ground infrastructure for them or it is difficult to deploy due to the harsh terrain.In addition,the ground network has poor survivability,and communication equipment is easily damaged when a disaster occurs,which increases the difficulty of rescue and reconstruction in the disaster area.With the advantages of satellite wide area coverage and unaffected by terrain,low-orbit satellite communication is an effective means to solve the above problems and can provide users in remote areas and disaster areas with effectiv e Internet access services.However,the high dynamics of low-orbit satellites lead to rapid changes in network topology,and long communication distances lead to long transmission delays.Therefore,when transmitting large capacity multimedia files,the traditional host-centric communication method has poor performance.To solve this problem,this dissertation combines network caching technology to optimize the performance of low-orbit satellites when transmitting multimedia files.This dissertation studies the cache placement and cache content transmission in low-orbit satellite networks.In the traditional low-orbit satellite network combined with the high-speed cache technology of the information center network to provide services for ground users.In this scenario,how to place popular files in the satellite so that users can access the required files faster is a key issue.With the help of inter-satellite links,this dissertation proposes a multi-slot low-orbit satellite network cache content placement problem,and uses an improved simulated annealing algorithm to solve the problem.The simulation proves that the proposed scheme is effective compared to the no-cache scheme.The communication transmission distance required to access files is reduced by 30%,and the proposed scheme is better than some existing classic cache placement strategies.In response to the recent trend of dense networking of low-orbit satellites,a research scenario for dense low-orbit satellite networks is proposed.In order to ensure the efficiency of users when downloading the required files,combined with edge caching technology,consider establishing an optimization problem in this scenario to maximize system energy efficiency,and three variables of user satellite association,satellite sub-channel and power allocation are jointly optimized.Finally,a matching algorithm and an iterative algorithm based on Lagrangian duality are used to solve the problem and perform simulation verification.The results show that the o n-board caching function can improve system energy efficiency by 30%.Compared with other algorithms,the algorithm proposed in this dissertation has performance advantage.In summary,this dissertation studies the cache content placement and cache content transmission issues in cache-based low-orbit satellite networks,and proposes practical solutions,which promote the research on cache issues in low-orbit satellite communications,which has certain practical value.