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cross each other and they are better than one another
for various time intervals.
6 CONCLUSIONS
In this paper, we proposed an unequal cluster-
ing algorithm for wireless sensor network based on
HEED (Younis and Fahmy, 2004). A common prob-
lem in equal based cluster in sensor networks is the
hot spot problem. Our approach to provide a solution
was first to implement the HEED algorithm, show
that the hot spot problem really exists, and finally at-
tempt to mitigate it by creating UHEED. This algo-
rithm uses a competition radius formula which cre-
ates unequal clusters as they are further away from
the base station. This effectively allows more inter-
cluster or relay traffic and less intra-cluster commu-
nication for nodes nearer to the base station, hence
preventing their early death. Simulation performed
on the UHEED algorithm demonstrated that the life-
time of the network was increased in all test scenarios
compared to HEED, LEACH and Unequal LEACH.
An interesting study also conducted was regarding
the value of the constant c in the competition radius
formula. Simulation results showed that a value of
c = 0.8 achieved up to almost 250% improvement in
the network lifetime when compared to HEED and
almost 100% improvement when compared to un-
equal LEACH. During the course of this investiga-
tion, we found out that values like first node dead
(FND), half node alive (HNA) and last node dead
(LND) are somewhat affected by the density of the
network. Hence, our future work will be to investigate
the relationship between the network density and the
aforementioned parameters. A mathematical model
will also be developed in order to support the simula-
tion results presented in this paper.
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