CAJ | 학술논문

针对以往农用无线传感器网络（wireless sensor network，WSN）能耗与成本较高、传输性能不理想等问题，该文选用无线射频芯片AT86RF212、单片机C8051F920等，设计了一种工作在780 MHz中国专用频段且与IEEE802.15.4c 标准兼容的无线传感器网络。该文简述了无线传感器网络节点结构，重点介绍了780 MHz 无线传感器网络的硬件设计，并选择北方典型的日光温室作为试验研究环境，通过改变无线收发距离，对780、433和2400 MHz频段的无线传感器网络节点的接收信号强度值（RSSI，received signal strength index）和平均丢包率（PLR， packet loss rate）进行了测试与分析。试验结果表明，3种不同频段的无线收发模块的接收信号强度值RSSI都随着收发距离的增大而减小。在温室内测试，收发距离小于20 m时，3种无线模块的RSSI值相近；收发距离为40～90 m时，7803 MHz模块比433 MHz模块的RSSI值略大，2.4 GHz的RSSI值最小。在温室内收发距离小于90 m的范围内，780 MHz模块和433 MHz模块的丢包率均为0，2.4 GHz模块的最高丢包率不超过5%。在温室间测试，收发距离为50～90 m时，780 MHz模块和433 MHz模块的RSSI值相近；收发距离大于90 m时，780 MHz模块比433 MHz模块的RSSI值大；2.4 GHz模块在温室间收发距离为50～140 m时的RSSI值均小于433、780 MHz。2.4 GHz模块在收发距离大于70 m时出现丢包现象，收发距离大于135 m时丢包率达到100%；温室间收发距离为140 m时，433 MHz模块的最大丢包率为11%，780 MHz的最大丢包率不超过6%。因此，在温室环境监测的应用中，780 MHz频段的无线传感器网络的传输性能表现最佳，且与433 MHz都明显优于2.4 GHz。
침대이왕농용무선전감기망락（wireless sensor network，WSN）능모여성본교고、전수성능불이상등문제，해문선용무선사빈심편AT86RF212、단편궤C8051F920등，설계료일충공작재780 MHz중국전용빈단차여IEEE802.15.4c 표준겸용적무선전감기망락。해문간술료무선전감기망락절점결구，중점개소료780 MHz 무선전감기망락적경건설계，병선택북방전형적일광온실작위시험연구배경，통과개변무선수발거리，대780、433화2400 MHz빈단적무선전감기망락절점적접수신호강도치（RSSI，received signal strength index）화평균주포솔（PLR， packet loss rate）진행료측시여분석。시험결과표명，3충불동빈단적무선수발모괴적접수신호강도치RSSI도수착수발거리적증대이감소。재온실내측시，수발거리소우20 m시，3충무선모괴적RSSI치상근；수발거리위40～90 m시，7803 MHz모괴비433 MHz모괴적RSSI치략대，2.4 GHz적RSSI치최소。재온실내수발거리소우90 m적범위내，780 MHz모괴화433 MHz모괴적주포솔균위0，2.4 GHz모괴적최고주포솔불초과5%。재온실간측시，수발거리위50～90 m시，780 MHz모괴화433 MHz모괴적RSSI치상근；수발거리대우90 m시，780 MHz모괴비433 MHz모괴적RSSI치대；2.4 GHz모괴재온실간수발거리위50～140 m시적RSSI치균소우433、780 MHz。2.4 GHz모괴재수발거리대우70 m시출현주포현상，수발거리대우135 m시주포솔체도100%；온실간수발거리위140 m시，433 MHz모괴적최대주포솔위11%，780 MHz적최대주포솔불초과6%。인차，재온실배경감측적응용중，780 MHz빈단적무선전감기망락적전수성능표현최가，차여433 MHz도명현우우2.4 GHz。
In recent years, a wireless sensor network (WSN) technique was widely applied in the field of agriculture, which detects, senses, and collects information of various environments or objectives in the network area, and at the same time sends and receives data through wireless and self-organizing multi-hop routing links. Due to the complexity of the agricultural environment and various factors like barriers, weather condition, structure, materials, and the layout of facility agriculture that all affect the WSN communication quality, wireless sensor networks adapt dissimilarly to agricultural environment. Therefore, how to achieve the best networking to different agricultural environment conditions, minimize the cost and energy consumption, and improve the performance of the network transmission turn out to be the key issue in the studying of agricultural wireless sensor networks. Aiming at the problems of previous agricultural wireless sensor networks, such as high cost, high-energy consumption, and non-ideal transmission performance, this paper designed, with chips of AT86RF212 and C8051F920 a new type of wireless sensor network which works on a Chinese dedicated band of 780MHz and is compatible with the IEEE802.15.4c standard for a greenhouse. This paper briefly described the structure of wireless sensor network node, mainly introduced the hardware design of a 780MHz wireless sensor network, and also tested and analyzed the received signal strength index (RSSI) and the average packet loss rate (PLR) of the wireless sensor network node in 433 MHz, 780 MHz, and 2.4 GHz bands by changing the wireless communication distance in a typical northern solar greenhouses working as the experimental environment. The experimental results showed that RSSI of wireless transceiver modules in the three different bands decreased with the increasing of the communication distance. The RSSI values of the three wireless transceiver modules were similar to each other when the communication distance in a greenhouse was less than 20m. When the distance reached 40-90m, the module in 780MHz showed a slightly larger RSSI value than the 433MHz module while the .4GHz module had the smallest RSSI. Within the 90m communication distance range in a greenhouse, packet loss rates (PLR) of both 780MHz and 433MHz modules were 0. For the 2.4GHz module, packet loss took place at a distance of 80m and when it went to 90m, the maximal PLR was 5%. When the communication distance was 50-90m between greenhouses, the RSSI of the 780MHz and 433MHz modules were close. The RSSI value of the 780MHz module was higher than that of the 433MHz module when the wireless communication distance exceeded 90m. For the 2.4GHz wireless module, the RSSI value was lower than both the 780MHzand 433MHz modules’ when communication distance between greenhouses was 50-140m. Packet loss occurred to the 433MHz module when the distance was over 100m, and when it went to 140 m, the maximal PLR was 11%. Packet loss took place to the 2.4GHz module if the communication distance between greenhouses exceeded 70m, and when it was over 135m, the PLR reached 100%. For the 780MHz band wireless module, packet loss took place when the communication distance between greenhouses was over 125m, and when the distance was 140m, the maximal PLR was smaller than 6%, which allows the reliable wireless transmission between greenhouses to proceed. Above all, the transmission characteristics of the wireless sensor networks in the 433MHz and 780MHz bands were obviously better than the WSN of a 2.4GHz band in the application of greenhouse environmental monitoring. The 780MHz band WSN was even superior as to transmission and communication quality performance.