Research And Implementation Of Internet Of Things Communication Protocol Based On LoRa Network Technology

In recent years,the Internet of Things industry has always maintained rapid development,and its application scenarios are becoming more and more rich and diverse,covering industrial manufacturing,social management,people’s clothing,food,housing and transportation,and many other fields,so the research and development of Internet of Things technology is of great importance.Long Range Radio(LoRa)is a low-power WAN technology designed for the Internet of Things(IoT)that has received widespread attention for its performance advantages such as long range and low power consumption.When large-scale nodes are deployed in a LoRa network,channel conflicts increase and packet transmission collisions will lead to a significant reduction in the transmission efficiency of the network.It has been shown that the Carrier Sense Multiple Access(CSMA)protocol based on the channel activity detection(CAD)mechanism of LoRa devices can solve this channel conflict problem well,but the limitations of CAD itself are less studied.The research is carried out to address this issue,and the main research is as follows:(1)A detailed analysis of the listening range of the LoRa network service area and CAD was performed to obtain the relationship between the end node locations and the corresponding number of hidden nodes,and a CSMA-based communication model for LoRa networks was developed.The analysis shows that the CAD listening range of the nodes cannot cover the whole LoRa network due to the limitation of the device performance,and the nodes hidden in their blind areas negatively affect the CSMA operation,and this effect increases with the increase of the number of deployed nodes,and the network transmission efficiency keeps decreasing to p-ALOHA.(2)The time synchronization algorithm of LoRa network is improved based on the one-way broadcast synchronization mechanism and the two-way message exchange mechanism.When the terminal nodes are deployed in a wireless network on a large scale,the time synchronization of either the one-way broadcast mechanism or the two-way message exchange mechanism suffers from the problem of redundancy of time synchronization information.Unlike the traditional time synchronization algorithm,this time synchronization algorithm synchronizes the local time of the nodes by transmitting normal information to add time stamps.And by drawing on the one-way broadcast synchronization mechanism,the time synchronization information is broadcasted by the gateway at regular intervals to further improve the time synchronization accuracy in the wireless network.The algorithm provides time synchronization basis for the actual operation of communication protocols.(3)Proposing a CSMA channel access scheme(LT-CSMA)based on node location and communication time planning,which plans the communication time of nodes in different locations in the LoRa network,aiming to make the communication time of nodes within the CAD listening range of each node adjacent,while hidden nodes outside the listening range will be isolated from them in terms of communication time,thus avoiding hidden nodes caused by channel conflicts.Simulation experiments prove that LT-CSMA can make full use of the idle radio channels and has very good packet transmission in LoRa networks with small deployment size,and its packet success probability is much higher than that of channel access mechanisms such as CSMA,s-ALOHA and p-ALOHA.Moreover,as the number of deployed nodes increases,LT-CSMA always outperforms CSMA and p-ALOHA in terms of data transmission efficiency and shows good scalability.(4)Designing the IoT experiment platform,mainly including the software platform design and LoRa device hardware and software design.Among them,the software platform consists of My SQL database,Web server and We Chat applet design and development to realize the upload,storage and visualization of the experimental monitoring data.LoRa devices include hardware design of gateway and node as well as software program design.Finally,the experimental platform monitors environmental parameters such as temperature,humidity and noise in the school and the surrounding area.The experimental results show that the PSP(Packet Success Probability)of all nodes in the LoRa network is maintained above 95%,and the transmission efficiency is excellent,which verifies the feasibility and effectiveness of the time synchronization algorithm and communication protocol proposed in the thesis.