A Two-Tiered Architecture for Real-Time Communications in Large-Scale Wireless Sensor Networks: Research Challenges

In wireless sensor networks (WSN), individual sensor nodes are inherently unreliable and have very limited capabilities to ensure real-time guarantees. In fact, one of the most predominant limitations in wireless sensor networks is energy consumption, which hinders the capacity of the network to provide real-time guarantees (e.g. low duty-cycles, low transmission range). Many approaches have been proposed to deal with energy/latency trade-offs, but they are likely to be insufficient for the applications where reduced delay guarantee is the main concern. This paper investigates the potential application of a decentralized two-tiered architecture, in large-scale wireless sensor networks, where an upper layer Wireless Local Area Network (WLAN), serves as a backbone to a wireless sensor network. Doing so, we target to provide more reliable services with reduced end-toend delays, and lower energy consumption in the underlying sensor network. We are also assessing candidate technologies for implementing this architectural approach, namely to use the IEEE 802.11 WLAN protocol on the top of the IEEE 802.15.4 protocol designed for low-rate wireless private area networks (LR-WPAN).