Research And Implementation Of 5G Downlink Scheduling Mechanism

Although the fourth generation mobile communication system has brought profound impact and great improvement to human society,the diversification of user communication requirements and the emergence of new mobile services have driven mobile communication technology to the fifth generation mobile communication system(5G).5G supports three main application scenarios: Enhanced Mobile Broadband(eMBB),Ultra Reliable and Low Latency Communication(URLLC)and Massive Machine Type Communication(mMTC).Diversified application scenarios and quality requirements of different services pose great challenges to the existing scheduling algorithms.Therefore,there is an urgent need for more in-depth research on 5G scheduling algorithms.Based on that the new wireless frame structure proposed by 5G to support the coexistence of multiple services,this thesis studies the downlink scheduling mechanism when the URLLC service coexists with the eMBB service.This mechanism allows the URLLC service data to occupy some radio resource that should be occupied by eMBB data.This mechanism punctures the eMBB service transmission data so that the URLLC service data could be transmitted,thus the mechanism could be scheduled in time to meet the ultra-low latency requirement.Based on the analysis of the existing puncturing scheduling strategy,this thesis proposes an improved puncturing scheduling algorithm: the puncturing scheduling algorithm based on delay and fairness.The algorithm considers that the eMBB service data can be divided into real-time type and non-real-time type.To reduce the system packet loss rate,different puncturing strategies are adopted according to characteristics of the service.At the same time,in order to protect the fairness between eMBB users,the number of times the eMBB service is punctured by the URLLC service for a period of time is introduced as a fairness factor.Besides,the instantaneous bit transmission rate and the average bit transmission rate of the user are introduced.The simulation results show that the proposed algorithm performs better in terms of packet loss rate,fairness and edge cell throughput than the original puncturing scheduling algorithm.Based on the above algorithm,this thesis designs and implements the algorithm on the actual 5G protocol stack platform.The main contents include the construction of scheduling queue,new resource allocation,retransmission resource allocation,TTI thread design,HARQ Interface design.Finally,the punching scheduler is tested based on the protocol stack platform,and the results proves the feasibility of the mechanism.