Design And Implementation Of A Gateway Between WSN And WLAN

Wireless sensor networks(WSN) based on the IEEE 802.15.4 standard has been widely used in many fields because of its wide coverage, low-cost, low-power, self-configuration, real-time data access, ect. Meanwhile, the IEEE 802.11 Wireless local area network(WLAN) namely Wireless-Fidelity(Wi-Fi) has been applied more and more widely in the field of Internet due to its characteristics such as high transmission speed, low cabling cost and extended geographic coverage. So far, it is an important demand in Internet application to interconnect the WSN and WLAN. However, WSN and WLAN namely Wi-Fi can’t communicate directly because they follow different network protocols, a gateway is needed to interconnect the nodes of these two heterogeneous networks. This is the main motivation of this article.Firstly, this paper introduces related technologies about the WSN and the Wi-Fi network. Then it designs a gateway to make these two networks communicate with each other from both hardware and software aspects. Finally, it simply designs the environmental data acquisition system based on TelosB nodes, a MySQL database, a Web server and a client, applies the gateway to the real agricultural greenhouse, so that farmers can monitor the temperature and humidity of the greenhouse with browser in real time at any time and any place.The WSN and the Wi-Fi network share the same frequency band, when they are deployed in the same environment, the Wi-Fi network owns larger power which will have a impact on the communication between WSN nodes, increase the bit error and packet loss rate. In view of this situation, this paper designs a algorithm called DAPLA in the gateway that can dynamically adjust the length of the sending packet according to the current environmental noise and packet loss rate at the same time. Experiments show that the algorithm results in a 47.6% increase in throughput than the program that uses a fixed 30 bytes payload in sending packets, and results in a 8% reduction in dropout rate than the program that uses a fixed 90 bytes payload.The scheme in this paper can be applied to Internet of things including WSN and WLAN.