Design And Implementation Of Core Modules For L3 Layer Of Special Small Base Stations

The LTE technology continues the 3GPP's GSM and UMTS technologies.Compared with the second-generation and third-generation communication systems,the LTE technology has greater bandwidth,higher uplink\downlink rates,and more flexible resource allocation,and its application area is gradually expanding to public security,smart city construction and so on.This paper is based on the needs of the public security department for real-time video transmission.It applies LTE technology to the development of small base stations and builds a private network for high-definition video transmission.The LTE protocol includes a physical layer,a data link layer,and a network layer(L3).The network layer is responsible for the entire network control signaling transmission,including Radio Resource Control(RRC)connection and S1 connection.This paper completes the design and implementation of the L3 layer protocol core module according to the 3GPP related standard protocols.The main contents of the dissertation study are as follows:1.L3 layer protocol implementation scheme designAccording to the overall function assumed by the dedicated small base station L3 layer,the L3 layer is decomposed into multiple modules.The RRC protocol and the S1 protocol are jointly assumed by the decomposed modules.On this basis,further analysis and evaluation of the feasibility of the specific implementation of each module.2.Design and implementation of low-layer interface managerIn the case of completing the overall design of the L3 layer,the lower-layer interface manager is further decomposed,the internal sub-modules of the lower-layer interface manager are designed,the various physical units of the sub-module are introduced,and then the two main sub-modules of the interface manager are The cell message management and UE message management entities perform state design and implementation.State transition diagrams and specific implementation procedures are given.The interface manager that interacts with the L3 layer and the lower layer will become the center of the unified external interaction of the L3 layer.3.Design and implementation of UE call control moduleFor the connection function of the construction of the small base station private network in the public security department,UE call control is introduced in detail from aspects of theoretical analysis,internal entity division,state machine design and code logic.Combining with 3GPP protocol,the difficulties in the design process are analyzed.From the call control function,the specific bearer entity of the function is designed,the finite state machine of the main entity is implemented,and the implementation of each sub-process is given for the RRC connection.Finally,this paper integrates the L1,L2 layers and perform functional tests.