Design And Implementation Of RRC Layer Connected Mode In NB-IoT System

With the rapid development of mobile communication,the Internet of Everything will be an inevitable trend.As a part of mobile communications,Narrowband Internet of Things(NB-IoT)are greatly expanding the range of mobile communications services,extending communication from human-to-human to things-to-things and human-to-things.NB-IoT has a wide range of applications,such as smart homes,smart cities.Different application scenarios have different communication requirements,such as the mass connection of devices,the frequent transmission of data,the ultra-low power consumption of devices and so on.In order to satisfy the communication requirements of the Internet of Things,the reasonable design of the NB-IoT terminal system is particularly important.The design and development of this dissertation is supported by the industry-specific major theme “NB-IoT Terminal SOC Development and Application”.The function of the RRC sublayer connection mode of the NB-IoT system terminal and realized based on the 3GPP R14 version protocol and project requirement analysis.The main contents are as follows:1.The implementation of the entire protocol stack is divided into two different platforms: the functions of the RRC sublayer and non-access stratum are implemented in the PC,the layer 1 and layer 2 are implemented on the multi-core digital signal processing(DSP)chip TMS320C6670.In order to realize cross-platform communication,the communication mechanism between PC and DSP is designed,including dual-thread communication mechanism,socket communication,and the adaptation layer.2.The main processes in connected mode of RRC are studied in detail,and designed according to the project requirements.The main research contents include RRC connection establishment,RRC connection resume,and RRC connection release and suspend processes.In order to deal with delay messages effectively and realize modularization processing,the corresponding state and triggering events of state transition are designed for the RRC sublayer.Besides,the communication primitives are designed for RRC sublayer to realize the inter-layers communication.and a detailed communicate design is performed for RRC connection establishment,RRC connection resume,RRC connection release and suspend processes.In addition,Some exceptions that may occur in these processes is designed,which can timely handle the abnormal condition in the process to ensure the feasibility of the design.3.Under the premise of combining protocol specification and related design work,main function processes in connected mode of RRC are programmed and verified in C language.The test included the normal situation and the exceptional situation.Through dozens of tests for each process,the results show that the pass rate was 100%,which proven the feasibility of the design,and also proven that the implementation content meets the requirements of the project and conforms to the protocol consistency.