Research On Failed Node Access Technology In LoRa Networ

The Internet of things(IoT)makes the interconnection of all things possible by creating ubiquitous connections.It is estimated that more than 40 billion devices will be connected to the network by 2025,in which there contains numerious M2 M communications.As a low power wide area networks(LPWAN)technology,LoRa has attracted extensive attentions thanks to its excellent anti-interference ability and long transmission distance.The LoRa WAN protocol adopts star network topology,and all terminal nodes communicate directly with the gateway.However,some terminal nodes called the failure nodes are always unable to access the network due to the influence of the surrounding environment.Therefore,to address the issue,this thesis investigates the protocol for the failure node access the gateway through the surrounding ordinary nodes as relays.The main work of this paper is as follows:Firstly,LoRa WAN network model is set up,in which the network simulation model,link model,statistical model and traffic model are built.The LoRa WAN protocol is simulated on the discrete event simulation platform ns-3(Network Simulator 3),and its performance is verified and evaluated.Secondly,to solve the issue of the failure nodes in the LoRa network,a failure node access protocol based on LoRa WAN is proposed.The failure node broadcasts the information.The ordinary nodes that receive the information of the failure node become the relay nodes and forward the information to the gateway.In the process of receiving the information of the failed node,the collision rate of the relay node is analyzed.The link model of the proposed protocol is built and simulated.The simulation results show that the protocol effectively makes the failure nodes access to the network,and the impact on the whole network is small after accessing the network.The access protocol can also realize load balancing at the relay nodes.Finally,the collision rate of the access method using LoRa WAN is large resulting in the small throughput of the network.To this end,a hybrid access protocol is proposed,where the ordinary nodes and relay nodes adopt slotted Aloha,and the failure node adopts the pure Aloha.The hybrid access protocol also improves the reception success rate of the relay node by reducing the emission power of the failure node and setting the emission probability for the failure node.The analysis and simulation results show that the hybrid access protocol has lower the average access delay of the protocol,and the twice throughput.