Abstract: In some wireless sensor networks(WSNs) applications, gateway nodes use WiFi to access upper layer network. However, due to the instability of wireless link quality, it has a lot of work to find a stable and reliable gateway disposition by using fixed gateways in traditional WSNs structure. In this paper, we propose a novel method for dynamic WiFi link access and adaptive networking called EasiARS, which is applicable to the scenarios where WiFi link quality is instable and all devices including gateways and nodes are energy constrained. EasiARS is based on WiFi and ZigBee multi-mode communication. It contains a low-overhead real-time WiFi coverage detection method, a roles switching method and a clustering and neworking method in WiFi coverage area. EasiARS makes it feasible to rapidly deploy WSNs systems in dynamic WiFi link environment. While system is working, nodes adjust their roles and transmission strategy according to the WiFi link quality, which ensures WSNs upload data stably and balance the energy consumption in WiFi coverage area. Experiments verify that, EasiARS achieves the purpose that nodes can switch to suitable roles and transmit stably in dynamic WiFi link environment. Compared with single fixed gateway method, EasiARS leads to a reduction up to 90% in packet loss rate under different WiFi link quality, and an improvement of 67% in network lifetime compared with fixed multi-gateway method, meanwhile reduces the burden of WiFi link quality testing and evaluation before deployment.

Key words: wireless sensor networks(WSNs), multi-mode communication, WiFi detection, adaptive networking, energy balance, roles switching