Research And Implementation Of Networking Protocol For Low Power Sensor Networks Based On LoRa

With the rapid development of economy and society,the application of wireless sensor networks has become increasingly widespread.From the traditional military and industrial applications to the current smart home,human health,environmental monitoring and other fields,all show its significant application value.But the development of wireless sensor networks has also encountered some problems,such as the problem that the signal transmission distance and power consumption are difficult to balance.However,owning to the development of Low Power Wide Area Network technology,this problem has also been solved.LoRa is an emerging low-power wide-area network technology.At the same time,this technology also has the feature of working-frequency license-free.In recent years,it has been widely used around the world.This thesis first introduces the research background of networking protocol for low power sensor networks based on LoRa and the current research status of low-power sensor network and LoRa.And then it also introduces the system architecture,characteristics,application scenarios and Low-power strategy of wireless sensor networks.Then the things followed next are a description of LoRa technology features,LoRaWAN network architecture and software hierarchy.Through research and practical tests,it is found that the LoRaWAN network architecture has insufficient coverage of a single gateway under certain scenarios and the problem of low data transmission success rate due to pure Aloha protocol.In this thesis,aiming at the existing mechanism fails to solve the problem of random access of two-hop nodes and the excessive delay of two-hop nodes joining network and data packet transmission,a new mechanism of node joining network and a new mechanism of two-hop TDMA time slot allocation are proposed.And then based on these two new mechanisms the thesis designs a two-hop TDMA networking protocol based on LoRa,and elaborates on the operation of the gateway node,the operation of the relay node and the operation of terminal node.After that,the protocol is implemented in a remote automatic meter reading system based on LoRa.The implementation is mainly performed on the LoRa terminal development board and personal computer of Rime Communication,and the system was developed based on the Contiki system platform development.Finally,through testing the node networking,data transmission,gateway throughput and node power consumption of the system,it is verified that the two-hop TDMA networking protocol based on LoRa can solve the problems existing in practical application of LoRa and achieve the expected results.In addition,the two proposed new mechanisms and old mechanisms are tested and analyzed in terms of node network access delay and data packet transmission delay respectively.The results show that the new mechanism has obvious advantages in these two aspects.With the number of nodes in the network increasing,this advantage is more obvious.Finally,the whole thesis is summarized and the future work of the two-hop TDMA networking protocol based on LoRa is prospected.