Research On Communication Link Quality For Low-power Long-range WSNs

LoRa(Long Range)-based wireless sensor networks can provide high-reliability and large-scale sensor networks coverage for a wide area with their low power consumption and long range.However,the complex and changeable deployed environment and collisions between nodes lead to unreliable communication link quality.As a result,the communication performances of the wireless sensor networks are deteriorated.Aiming at the above problems,a communication system based on LoRa is designed.Based on experimental tests,the distribution characteristics of link quality in complex scenarios are studied,and the effects of LoRa physical layer parameters on communication performance are analyzed.The communication link performance is improved through optimized parameter configuration and multiple access protocols,the specific research contents include:On the one hand,in this thesis,the distribution characteristics of unreliable links and the effects of physical layer parameters on communication performance are analyzed.First of all,a LoRa-based wireless sensor networks communication system is designed,including the software and hardware design of sensor nodes and sink nodes.Secondly,based on the system,a link quality analysis method combining hardware parameters and probability statistics is used to study the characteristics of link quality distribution in both land and sea scenarios.Finally,based on test data,the effects of physical layer parameters such as spreading factor(SF),bandwidth(BW),and forward error correction coding rate(CR)on the quality of the communication link are analyzed.The experimental results show that in the maritime scene,the communication sensitivity can be improved by 12 d Bm by optimizing the settings of LoRa physical layer parameters.On the other hand,a hybrid multiple access method with multi-domain collaboration is proposed.First of all,according to the methods of space division multiple access(SDMA)and frequency division multiple access(FDMA),sensor nodes are grouped according to location,and each group of nodes uses independent channels to prevent co-channel interference between different groups of nodes.Secondly,the same group of sensor nodes is layered according to the link quality,and each layer of sensor nodes is assigned different spreading factors to suppress interference.Finally,a carrier sense multiple access(CSMA)method based on the channel occupancy detection mechanism is used between nodes in the same group and layer to avoid communication collisions.Experimental results show that compared with the random multiple access method,the above hybrid multiple access method can effectively alleviate communication interference between nodes,reduce communication packet loss rate and packet error rate,and improve the link performance of wireless sensor networks.