In wireless sensor networks (WSNs), the present bunch based information accumulation procedure expends more vitality. Additionally, the secured information transmissions are essential for upgrading the information confirmation and secrecy. Keeping in mind the end goal to conquer these issues, in this review, In this paper, we provide detailed analysis on the relations between clustering and routing, and then propose a Low-energy adaptive clustering hierarchy (LEACH) protocol for reliable and efficient data collection in a large-scale wireless sensor network. LEACH adopts the back off timer and gradient routing to generate connected and efficient inter-cluster topology with the constraint of maximum transmission range. The relations between clustering and routing in LEACH are further exploited by theoretical and numerical analysis. The results show that the multi-hop routing in LEACH may lead to the unbalanced cluster head selection. Then the solution is provided to optimize the network lifetime by considering the gradient of one-hop neighbor nodes in the setting of back off timer. Theoretical analysis and simulation results prove the connectivity and efficiency of the network topology generated by LEACH.