In an Agricultural Internet of Things (AIOT) system, there are a variety of wireless communication devices working simultaneously and producing interference due to using different protocols. In this paper, the problem on coexistence of ZigBee/ WiFi in AIOT is analyzed and a dynamic channel assignment method is proposed. ZigBee network defects interference and switches channel quickly to avoid the interference of the WiFi network while packet loss rate exceeds the critical value. In order to

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... ce energy consumption of nodes, this paper proposes power control technology based on communication distance. Experiments show that ZigBee can basicly avoid WiFi interference. At present, the ZigBee technology in AIOT mainly includes the following two problems[7][8]: A. Energy Consumption. In the AIOT system, the energy of coordinator is supplied by power, and the energy of enddevice is powered by battery which average life is six months. This paper This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). proposes that the transmit power is adjusted according to the communication distance of the equipments, which can solve the energy consumption of node well. B. Interference Problems. ZigBee/WiFi exist in the AIOT system and work in the ISM band of 2.4GHz, integrating the existing attenuation model, The distance R between ZigBee and WiFi can be divided into three categories (R1 = 35 m; R2 = 80 m): R1:dR2, the two data transmission can not be interfered with each other. ZigBe/WiFi are working in the 2.4GHz ISM band as shown in Fig. 2, ZigBee works on the IEEE 802.15.4 standard and WiFi works on the IEEE 802.11 standard, part of the parameter settings are shown in TABLE I. ZigBee's bandwidth is 2MHz, and WiFi's bandwidth is 22MHz. ZigBee has a low transmit rate, when WiFi and ZigBee coexist, WiFi will inevitably cause serious interference to ZigBee nodes[9], which may cause network communication failure or even collapse. From Fig.1, It can be seen that the channel 15, 20, 25 and 26 are out of the communication frequency range of the WiFi, so that these four channels are less likely to suffer from WiFi interference. And channel 11, 12, 13 and 14 are in a WiFi operating frequency range, so switching channel between the four channels is more likely to be interfered.