Research And Implementation Of Data Link Layer Protocoi Of Satellite Co-Mmunication System Based On NB-IoT

In recent years,NB-IoT and satellite communication technologies have developed rapidly.The converged network has become a research hotspot.As an important part of the air interface protocol,the data link layer is responsible for important processes such as terminal access,resource scheduling and data transmission.But satellite networks are different from terrestrial networks in terms of communication distance and link conditions.The data link layer protocol of the ground NB-IoT cannot be directly applied to satellite scenarios.The NB-IoT satellite communication system supports massive terminal access.The terminals are usually battery-powered.The satellite-ground link attenuation is large,and the required transmission power is much larger than the ground.In order to solve the problem of large terminal energy consumption in converged network,we improve the existing PSM mechanism and propose an algorithm to calculate the optimal PSM duration.The load situation in the current network is introduced into our algorithm.The optimal solution is calculated iteratively by the genetic algorithm.Our algorithm effectively improves the power saving performance and the adaptability in different scenarios of the PSM mechanism.In order to solve the problem of high latency in satellite scenarios,we optimize the MAC,RLC and RRC sublayer protocols of the NB-IoT data link layer.We meet the delay requirements by modifying the signaling process and scheduling process,reducing the impact of satellite-ground round-trip delay and reconfiguring key parameters.Then we carry out a detailed architecture design of the modified protocol and build a software simulation platform based on OpenAirInterface platform.The MATLAB simulation results of the proposed algorithm show that our algorithm can significantly improve the power saving performance of the PSM mechanism while meeting the delay requirements.In addition,we test the simulation platform and the test results verify the correctness of the platform and the usability of the protocol.