Design And Implementation Of Multi-PDN Connect On Narrow-band Internet Of Things For A Small Range Of Mobile IoT Devices

With the rapid development of big data and the Internet of Things,nb-iot(Narrow Band Internet of Things)has gradually become one of the main technologies of the Internet of Things.As a sub-layer of NAS layer of nb-iot protocol stack,ESM layer initiates the PDN connection process,which has an important impact on nb-iot system.When the device moves,the ESM layer will update the tracking area and establish a new PDN connection.However,network congestion and long connection time will occur in the area with dense device nodes.Therefore,the PDN connection mechanism can be optimized to reduce network congestion and improve the connection rate.According to the movement frequency of mobile devices in the tracking area,this research optimized the current PDN connecting by maintaining multiple PDN connections locally.First of all,the system in this research needs to create a corresponding PDN connection thread for each PDN connection,and store the PDN connection thread adaptively in the local;Then,when the device is moved,the system will switch the PDN connection thread to replace the update process of the tracking area,so as to reduce the connection time of PDN and avoid the repeated establishment of the PDN connection.For the problem of network resource occupation caused by local adaptive storage of PDN connection threads,this research dynamically deleted idle PDN connection threads through the dynamic management mechanism of multiple PDN connections.Those two mechanisms work together successfully ensuring the deduction of network congestion meanwhile reducing the occupation of network resources.In this research,the designing of a multi-pdn connection was tested on an embedded system with STM32F103RCT6 as the MCU,and the tracking area update during the device movement was simulated by interrupting the input.The test contents include PDN connection function test,multi-pdn connection system test and multi-pdn dynamic management test.The test results show that the average connection time of the multi-pdn connection mechanism can be reduced by more than 25% compared with the tracking zone update process of3 GPP R14 version.At the same time,the network resource consumption is reduced by more than 25% compared with that before dynamic management.Therefore,the research results of this research have certain value for the Internet of things application system.