Design And Implementation Of Radio Link Control Layer Protocol Of Narrow Band Internet Of Things

With the rapid development of big data and the Internet of things,the Narrow-Band Internet of Things(NBIo T)has gradually become one of the main technologies of the low-power wide-area Internet of things.The radio link control(RLC)layer is a sub-layer of the NB-Io T protocol stack.The performance of the RLC layer has an important influence on the NB-Io T system.When the RLC layer changes in the network environment,it’s sliding window’s parameters cannot be effectively adjusted according to the network environment,so network congestion will occur,resulting in the decrease of transmission rate or the waste of system resources.Therefore,the sliding window mechanism can be further optimized to reduce the impact of network congestion on data transmission and improve the transmission rate.In this thesis,the RLC layer protocol stack of NB-Io T terminal devices is designed and implemented by using improved Bottleneck Bandwidth and Round-trip propagation time(BBR)congestion control algorithm.In the acknowledged mode,firstly,the BBR algorithm are added to the data transmission process of the RLC layer.Then the calculation method of detecting the minimum round-trip time of the BBR algorithm is improved.Different calculation methods are adopted under different congestion levels.Finally,the parameters of the sliding window are adjusted according to the congestion control algorithm.The above improvements jointly completed the congestion control design under the confirmation mode to effectively reduce the impact of network congestion on the terminal equipment.In the unacknowledged mode,the sliding window of the receiving end is improved by adding new decision parameters.Firstly,this thesis to BBR based on MATLAB algorithm is validated the simulation,the simulation results prove that the improved BBR algorithm throughput increased by 14% compared with the protocol stack.Then,based on the STM32 microprocessor implementation and test environment is constructed.The test results show that the function test of the RLC conforms to the function of the protocol.In terms of performance,compared with the protocol,the average transmission rate of the design increased by 14% and the delay decreased by 20%,which reached the expected design index.The research results have value for the application of RLC layer of NB-Io T.