  Clustering is a very popular network structuring technique which mainly
addresses the issue of scalability in large scale Wireless Sensor Networks.
Additionally, it has been shown to improve the energy efficiency and prolong
the life of the network. The suggested protocols mostly base their clustering
criteria on some grouping attribute(s) of the nodes. One important attribute
that is largely ignored by most of the existing multi-hop clustering protocols
is the reliability of the communication links between the nodes. In this paper,
we suggest an adaptive and completely distributed multi-hop clustering protocol
that incorporates different notions of reliability of the communication links,
among other things, into a composite metric and uses it in all phases of the
clustering process. The joining criteria for the nodes, which lie at one hop
from the elected cluster heads, to a particular cluster not only consider the
reliability of their communication link with their cluster head but also other
important attributes. The nodes that lie outside the communication range of
cluster heads become cluster members transitively through existing cluster
members utilizing the end-to-end notion of link reliability, between the nodes
and the cluster heads, along with other important attributes. Similarly,
inter-cluster communication paths are selected using a set of criteria that
includes the end-to-end communication link reliability with the sink node along
with other important node and network attributes. We believe that incorporating
link reliability in all phases of clustering process results in an efficient
multi-hop communication hierarchy that has the potential of bringing down the
total communication costs in the network.
