###### Abstract  
In this paper, we investigate alternative distributed clustering techniques for wireless sensor node tracking in an industrial environment. The research builds on extant work on wireless sensor node clustering by reporting on: (1) the development of a novel distributed management approach for tracking mobile nodes in an industrial wireless sensor network; and (2) an objective comparison of alternative cluster management approaches for wireless sensor networks. To perform this comparison, we focus on two main clustering approaches proposed in the literature: pre-defined clusters and _ad hoc_ clusters. These approaches are compared in the context of their reconfigurability: more specifically, we investigate the trade-off between the cost and the effectiveness of competing strategies aimed at adapting to changes in the sensing environment. To support this work, we introduce three new metrics: a cost/efficiency measure, a performance measure, and a resource consumption measure. The results of our experiments show that _ad hoc_ clusters adapt more readily to changes in the sensing environment, but this higher level of adaptability is at the cost of overall efficiency. wireless sensor networks; clustering; distributed adaptive systems; reconfigurability +
Footnote †: journal: Sensors  
environments. Given the distributed nature of many of these systems, management and coordination are key challenges. Reliability and robustness given harsh industrial conditions, which can arguably require higher reliability requirements than other commercial systems, is another key implementation issue. Given the harsh, uncertain, and dynamic conditions present on the factory floor, WSNs applied in this domain must be capable of rapidly adapting to change in order to support the flexibility and responsiveness required of the system as a whole. More specifically, the WSN should be capable of allowing sensor nodes to be added and/or removed from the system on-the-fly to support changes in the configuration of the shop floor, and also be capable of handling signal loss that occurs during the tracking process as a result of blockage and/or noise from machinery. As a result, the wireless sensor network must be dynamically reconfigurable: _i.e._, it should have \"... the ability to repeatedly change and rearrange (its components) in a cost effective way\" [3]. Given the limited battery life of wireless sensor nodes, \"cost effective\" in this context relates to reducing the amount of communication and the corresponding energy consumption of the system. This paper addresses this set of challenges with the following contributions. First, we develop a novel distributed management approach for tracking mobile nodes in a 400-676 node network subject to harsh industrial conditions presented by signal blockage and noise. Although Mobile Node tracking can be accomplished using a centralized WSN management approach, we propose a distributed, agent-based approach to achieve the flexibility and responsiveness required of factory automation systems. As illustrated in Figure 1, we propose dividing the factory environment into sensor zones, consisting of groups of static Anchor Nodes that are clustered around fixed Sink Nodes. Each cluster zone is managed by the Sink Node and is responsible for tracking Mobile Nodes that pass through its geographic area. Secondly, we provide an objective comparison of alternative distributed cluster formation techniques for wireless sensor node tracking. Our focus here is to quantify the trade-offs associated with competing reconfigurable systems approaches: although various reconfigurable system designs have been proposed in the literature [3], the trade-offs associated with these alternative designs is still an open issue. To accomplish this, we focus on two main approaches proposed in the literature: (1) pre-defined clusters based on efficient geographical partitioning of sensor nodes around cluster heads; and (2) _ad hoc_ clusters that are formed \"on the fly\" during tracking.