Data Aggregation Tree Construction: Algorithms and Challenges
Zahra Eskandari, Fatemeh Ayughi · InTech eBooks · 2011
Wireless Sensor Networks (WSNs) are a set of communication networks which consist of sensor nodes. These nodes sense the events occurred in their own area and transmit the data related to these events to the sink node. The sink node is considered as the gateway. The sink is in relation with the end user and disseminates the queries requested by the user (Akyildiz et al, 2002) in the network. Receiving the query, the nodes of the network should sense the query’s required data from the environment and send them to the sink. The first advantage of wireless technology is easy deployment of sensors, so that outdoor environments like forests, deserts and the wildness in general can be covered. The second advantage is the possibility of networking mobile nodes. The application scenarios are various, ranging from the obvious military applications, such as distributed battlefield sensing or frontier control, to peaceful and civilian uses. Examples are: habitat monitoring (birds, whales), home intelligence (e.g. local climate control and smart appliances), biomedical, patient tracking, disaster relief, surveillance, fire control, agricultural, and industrial control (Cantoni et al, 2006). WSNs have specific characteristics. In these networks, the nodes are randomly deployed in the environment, i.e. the geographical locations of these nodes are undetermined (Eskandari et al a, 2008) and these nodes are inaccessible. Furthermore, the nodes are deployed in the environment densely. These nodes have generally low capability for processing and storing. So the tasks that the nodes perform should not be computationally complex. Furthermore, one of the main constraints in these networks is energy resource due to size and cost limitation in their nodes (Lee & Wong c, 2006), so, the tasks should be energy efficient. Up to now, many attempts have been made to minimize energy consumption (Chlamtac & Kutten, 1987; Chlamtac & Weinstein, 1991; Heinzelman et al, 2000; Min & Chandrakasan, 2001; Upadhyayula et al, 2003; Krishnamachari et al, 2002; Intanagonwiwat et al, 2004). In monitoring application, the sensor nodes sense data from the environment periodically and transmit these data to the sink node. The nodes in the network are densely developed,