摘要
该文针对近海渔业和大面积水产养殖环境监测应用周期长,覆盖面积大等特点,设计了基于LoRa技术的长距离低功耗无线传感网络系统。该系统设计了低成本的双信道LoRa网关,并在此基础之上提出了一种新颖的速率自适应的双信道同步调度无线通信策略。该策略充分利用LoRa技术多扩频因子多数据率的特点,对网关不同距离范围内的终端节点自动分配不同的扩频因子以确保网络连通性,并通过MAC层同步调度,在保证监测网络大面积覆盖的同时,大大降低了无线信道碰撞的概率,提高了异常数据上传的实时性和终端节点的平均网络寿命。通过仿真和现场试验验证了本方案的有效性,系统可有效覆盖半径3 km的监测区域,100个终端节点的网络规模;对于视距通信,该策略的投递率从单一扩频因子的0.8提升到0.99,对于数据上传周期为10 s的快速通信,投递率从单一扩频因子的0.4提升到0.95以上;如采用3 600 mA·h锂电池,数据上传周期为10 min,终端节点寿命可达1 a。
The design of wireless monitoring system for fishery environment based on Internet of Things technology has become a research hotspot at present.Aiming at the characteristics of long monitoring period and large coverage area in applications of inshore fishery and large area aquaculture environment monitoring,-the long range low power sensor networks was designed based on LoRa technology-.Due to the expensive price and technology closedness of commercial LoRa gateway SX1301,a low cost open dual-channel gateway was designed,based on two LoRa SX1278 transceivers.Based on the hardware design of dual-channel gateway,a dual-channel synchronous communication scheme with adaptive data rate was proposed.Two LoRa SX1278 transceivers corresponded to two independent channels,namely periodic data channel 1 and special function channel 2.The periodic data channel was used to upload regular packets,data collecting cycle of which was divided into several periods using different spreading factor(SF).Each period was equally split into several slots to the nodes within the same distance range in which the spreading factor was the same.The special function channel 2 was used to upload urgent packets,join in network,and synchronize time.For urgent packets,the terminal nodes could directly upload by switching channel 2 without waiting for the allocated slot arriving,to improve the real-time response of the network system.The scheme fully took the advantage of the characteristics of multiple spreading factors based on LoRa.Different spreading factors was assigned to terminal nodes according to the distances to gateway automatically with the different received signal strength indication and signal noise ratio of the received packets to ensure network connectivity.The scheme was built into a custom Matlab simulator to evaluate the data collision ratio,communication delay and energy cost performance varying with the network size(number of terminal node).With the terminal nodes increasing to 100,the performance of proposed scheme was nearly constant;but the collision ratio with single channel and single spreading factor was nearly linearly increasing to 1,and energy cost increased much more.The field experiment was carried out to test the effectiveness and reliability in Dishui Lake in Shanghai.An application program(App)for Android mobile phone was developed for monitoring field data.Four terminal nodes with dissolved oxygen sensor and pH value sensor were deployed in different distance to gateway.To line-of-sight communication,the average delivery ratio of proposed scheme increased from 0.8 to 0.99 compared with single spreading factor.To the rapid communication with 10 s uploading interval,the average delivery ratio increased from 0.4 to 0.95 compared with single spreading factor of 12.The proposed scheme largely reduced the wireless channel collision probability,improving the real-time performance for urgent data and the average lifetime of terminals,while ensuring large coverage area of monitoring network by the MAC layer synchronization scheduling.The simulation and experiment results showed the effectiveness of the proposed scheme.The designed sensor network system could cover a monitoring region with radius of 3 km,with the capacity of 100 terminal nodes and terminal node with 3600 mA·h lithium battery could work for 1 a with the 10 min data uploading interval.
作者
张铮
曹守启
朱建平
陈佳品
Zhang Zheng;Cao Shouqi;Zhu Jianping;Chen Jiapin(College of Engineering Science and Technology,Shanghai Ocean University,Shanghai 201306,China;School of Electronics Information and Electrical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2019年第1期164-171,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(61362017)
上海市科委2017年度"创新行动计划"(17050502000)
上海海洋大学科技专项基金(A2-0203-17-100209)
2017年上海市(临港)产学研合作项目(沪临地管委经[2017]56号)
