Performance study of RSS-based location estimation techniques for wireless sensor networks

Most sensors are event-driven and wireless sensor networks are mostly used for monitoring purposes in environmental monitoring, structural monitoring, and military battleground and public safety applications. As a result, there is a need to quickly and accurately pin-point a sensor's location when it detects an emergent event. Since sensor networks are severely resource-constrained due to various physical and environmental constraints, including miniature size, limited battery power, and limited communicational and computational capacity, a low-complexity location estimation technique is needed. Several received-signal-strength (RSS) based techniques have been proposed as a low-cost, low-complexity solution for location estimation in wireless sensor networks, including the basic RSS location estimator and the RSS-UDPG location estimator in our earlier study, which jointly estimates location coordinates and the parameter of channel model, i.e., the distance-power gradient. In this paper we present a comparative study of these two location estimators based on computer simulations. It is shown that when the channel model is assumed known a priori, the two estimators have comparable performance, but RSS-UDPG is strongly preferred when the prior estimate of the channel model is inaccurate or when the channel characteristics tend to change, either accidentally or seasonally