This makes directed
diffusion highly reliable in error-prone sensor network communication. When the
event is received by the sink, the sink can decide only to receive reports from a
334 Kai-Wei Fan, Sha Liu, and Prasun Sinha
Fig. 1. Steps in Directed Diffusion.
single path or a few paths with higher quality of data, which reduces the network
traffic load by avoiding packets being flooded throughout the network. Therefore
directed diffusion is suited for highly dynamic sensor networks that require reliable
and also energy efficient communication.
Chapter 13 Data Aggregation in Wireless Sensor Networks 335
3 Low-Energy Adaptive Clustering Hierarchy
Low-Energy Adaptive Clustering Hierarchy (LEACH) [2, 3] is a distributed clustering
protocol that utilizes randomized rotation of local clusterheads to evenly distribute
energy consumption among sensors in the network. The basic idea is that
nodes elect themselves as clusterheads according to some probability. Nodes that
are not clusterheads join the cluster of the closest clusterhead, as shown in Figure
2. After the clusters are formed, nodes send their packets to their clusterheads, the
clusterhead aggregates their packets and sends the aggregated data to the sink directly.
The clusterhead selection process is performed once every round, and nodes
that have been selected as clusterheads will not become clusterheads again in the
following rounds before all nodes in the network have been selected as clusterheads.
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