The Anchor Location Service (ALS) protocol for large-scale wireless sensor networks

Location-based routing (LBR) is one of the most widely used routing strategies in large-scale wireless sensor networks. With LBR, small, cheap and resource-constrained nodes can perform the routing function without the need of complex computations and large amounts of memory space. Further, nodes do not need to send energy consuming periodic advertisements because routing tables, in the traditional sense, are not needed. One important assumption made by most LBR protocols is the availability of a location service or mechanism to find other nodes' positions. Although several mechanisms exist, most of them rely on some sort of flooding procedure unsuitable for large-scale wireless sensor networks, especially with multiple and moving sinks and sources. In this paper, we introduce the Anchor Location Service (ALS) protocol, a grid-based protocol that provides sink location information in a scalable and efficient manner and therefore supports location-based routing in large-scale wireless sensor networks. The location service is evaluated mathematically and by simulations and also compared with a well-known grid-based routing protocol. Our results demonstrate that ALS not only provides an efficient and scalable location service but also reduces the message overhead and the state complexity in scenarios with multiple and moving sinks and sources, which are not usually included in the literature.