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A virtual backbone plays an important role in routing packets in a Wireless Sensor
Network where a predefined infrastructure is absent. Some nodes of the network
takes on additional responsibilities in an algorithmic framework to form the virtual
backbone. A connected dominating set (CDS) can work as a virtual backbone in a
wireless network. A dominating set of a graph is a subset of its vertices such that
each node is either within that set or adjacent to one of the nodes present in that
set. If the nodes within the dominating set are connected, then the dominating set
is known as a connected dominating set. As the routing responsibilities lie only
on the CDS nodes, we are interested in minimizing the CDS size. However, the
construction of minimum CDS is an NP-Complete problem. In this dissertation,
we first designed a new centralized degree-based greedy approximation algorithm,
which constructs CDSs of smaller sizes in comparison with other existing algo-
rithms. The proposed algorithm retains the current best approximation ratio and
is also the most time efficient CDS construction algorithm. In our second work,
we developed a novel distributed greedy approximation algorithm for CDS con-
struction which reduces the CDS size effectively. Our simulation shows that this
is the most size optimal distributed CDS construction algorithm with linear mes-
sage complexity. The algorithm constructs the CDSs in lesser number of rounds
in comparison to other degree-based algorithms. In a CDS, a node may fail or
downgrade due to lack of its battery power or some other reason. In this situation,
it is advantageous to repair the current CDS rather than reconstructing a fresh
CDS. In our third work, we developed a distributed CDS maintenance algorithm
which repairs the CDS by changing the role of only a few nodes. The proposed
algorithm has linear time and message complexity. This CDS maintenance scheme
handles the failure of both CDS and non-CDS nodes. To use our distributed CDS
construction and maintenance algorithms each node needs its two-hop neighbours’
information.
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