The Implementation And Optimization Of MAC Protocols For Low-power WAN Based On Lora

Low-power wide-area technology is a new communication technology specifically proposed for the low-power long-distance scenarios that appear in the current Internet of Things.Low-power wide-area technology will provide a strong foundation for the interconnection of all things in the world,its emergence will inevitably lead to the transformation of traditional Internet of Things and provide direction for the development of a new generation of Internet of Things technology.LoRa is one of the rapidly-developing technologies for low-power wide-area technology.Due to its ultra-long-distance communication and ultra-low power consumption,LoRa has attracted worldwide attention.At present,LoRa technology has demonstrated its unique advantages and been deployed in the smart home,smart monitoring,industry,agriculture and other areas.First of all,the background and research status of low-power wide area network and LoRa technology is described in this thesis.The network architecture including basic concepts,network models,and communication principles of the low-power wide area network is summarized and the advantages,disadvantages,and application scenarios of the current mainstream low-power wide area technologies are analyzed.Then,the relevant MAC layer technology in the current low-power wide area network is summarized in this thesis,and part of the current MAC technologies are selected for analysis.Secondly,this thesis the LoRa and LoRaWAN technologies are introduced,analyzed,and summarized in detail,including technical features and communication principles.With reference to the LoRaWAN protocol,the frame structures required for the transmission process are designed,including access frames,data frames,MAC command frames and message confirmation frame.The mutual communication between nodes is realized,including the CAD mechanism,data transmission,and data receiving mechanism required for MAC layer transmission.Next,through the deep research of the LoRaWAN protocol,it is found that the multiple message transmission mechanism in the protocol has redundant control overhead,and the message transmission efficiency is low relatively.In order to solve the above problems,an adaptive multi-frame transmission mechanism(AMFT)is proposed.The new mechanism makes relevant modifications to the data types and ACK frame structure,and it adds the mapping field of the frame to map the reception status of multiple acknowledgement frames.At the same time,the transmission process of the message is modified to accommodate the transmission of multiple messages.Then,the hardware and software modules needed to implement MAC layer communication in LoRa-based low-power wide-area network are select.Based on the existing LoRa radio frequency module,the LoRaWAN protocol was implemented in combination with the STM8 L development board;and the QT & C++ development language are used to implement serial communication and coding analysis between the terminal and the computer.Next,the LoRa's communication performance is tested through the developed platform.Then,through tests on continuous transmission of multiple messages between the original mechanism and the new mechanism,it is verified that the new mechanism can reduce control overhead and energy consumption and improve data transmission efficiency.Finally,the full text is summarized,and the future work of LoRa network MAC layer transmission mechanism and low power consumption strategy is prospected.According to my own research and development experience,the next research direction is given.