This paper is a review on the critical problem of network lifetime of WSNs. Due to limited battery of sensor nodes, so energy efficiency found to be main constraint of limited life of WSNs. Therefore the main focus of the present work is to find the ways to minimize the energy consumption problem and how one can enhance the network stability period and life time. Many researchers have proposed different kind of the protocols to enhance the network lifetime but still much improvement can be done

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... further to enhance the network lifetime further. The overall objective of this paper is to evaluate the gaps in existing clustering techniques of WSNs. This paper has evaluated the issues which have been neglected in the field of the WSNs.