Design And Implementation Of Narrowband Internet Of Things Radio Link Control Layer Protocol

Owing to the rapid development of technologies of Internet of Things(IoT)and the increasing number of applications of intelligent terminals,the current transmission protocol can no longer meet the needs of Internet of Things.Narrow Band Internet of Things(NB-IoT)is a new technology proposed by the International Mobile Telecommunications Standards Organization(3GPP)for strong coverage,low power consumption,low cost and multi-connection in the IoT requirements.At the same time,as far as the application of Internet of Things is concerned,it is mainly used in the occasions of organizing production,managing mobile office,intelligent public transportation,automobile,environmental protection,logistics,etc.,which have high requirements on data transmission accuracy,stability and time delay.Therefore,in order to ensure the smooth,fast and real-time performance of NB-IoT in IoT applications,it is necessary to study the wireless link sublayer of the narrowband IoT protocol stack to reduce latency,improve throughput and stability.In this thesis,the protocol framework of NB-IoT is expounded firstly.The transmission mode,retransmission mechanism,wireless link layer sliding window and congestion control algorithm in the wireless link layer are introduced.And then,in order to improve the throughput rate and reduce the delay,the sliding window mechanism in the wireless link layer is studied.The slow-start congestion control algorithm and the congestion avoidance algorithm are implemented to implement the congestion control of the sliding window.The automatic retransmission mechanism and state feedback mechanism in the RLC layer and the TCPW congestion control algorithm are studied.Based on the fusion,the sliding window optimization algorithm based on Polling-TCPW is designed to improve the performance of the system.During the RLC standard protocol is studied,the protocol data packet generation and parsing algorithm in RLC is designed to realize the function of RLC layer data packet adaptation to the underlying resources.Then,based on the Polling-TCPW core algorithm,the RLC layer protocol stack packet processing,automatic retransmission,and status packet processing are designed and implemented.Finally,this paper relies on the ARM development platform to build a test environment and test the RLC protocol stack and related mechanisms for functional testing and throughput,latency,and system stability.The test environment of the RLC layer protocol stack is realized by building an ARM hardware test platform and a MATLAB software analog channel.Write test code for the RLC layer and the functionality and performance of the RLC layer protocol stack are tested.The test results show that the RLC layer protocol stack designed and implemented in this paper has the functions of packet adaptation of the underlying resources,state message processing,packet segmentation and sliding window transmission.The performance of the system is greatly improved compared with the standard protocol.The throughput rate increased by 10% and the delay decreased by30%.The research results improve the efficiency of the system and have certain engineering practical value for the Internet of Things application system.