## 3 System Model and Framework
### Research Problem Foundation  
From the literature survey discussed above in Section 2, we found that a routing protocol in WSN/IoT may face the problems: (1) due to long path communication; (2) due to failure of some nodes; (3) due to latency in the delivery of data; (4) protocols developed for small scale applications break down when the number of nodes is increased; (5) due to load imbalance over the CHs; (6) due to single hop communication, _etc_. To deal with these problems, many protocols have been proposed in the recent past. With LEACH [28], election of the optimum cluster heads reveals that it can improve the network lifetime, but direct communication of the nodes with the CHs poses a problem, so many other protocols have been proposed to date to improve the clustering scheme as proposed by LEACH. SEP [29] improved the network lifetime as compared to LEACH by exploiting the benefits of heterogeneity. TDEEC [39] also tried to increase the stability period of the network by using multi-level heterogeneity and by considering the threshold value of energy during the election of CHs. EESAA [40] has taken into account one more parameter in addition to residual energy and that is switching between sleep and active modes to save energy. By using the dual power mode that is low power for intra-cluster communication and high power for inter-cluster communication, MODELACH makes an attempt to minimize the energy usage of the nodes.  
Clustering-based genetic protocols such as genetic HCR [46], ERP [45] improve the stability period for the working of the WSN as compared to SEP and LEACH by the election of new CHs based on mutation, but these protocols take a lot of time in the election of the best breed for the CHs.  
From these protocols it is concluded that clustering is the best topology to maximize the energy efficiency, which is the stringent requirement of IoT applications and clustering facilitates the scalability feature for the IoT which is required due to its increased network size. Less processing of the nodes can also further enhance the energy level. As in the above protocols CHs are elected in every round based on different strategies such as the optimum number of CHs, based on residual energy and based on mutation. This gave us the idea that instead of the election of CHs again and again in each round, the role of CHs can be exchanged with the high energy nodes only when it is found in some round that the energy of some CHs has fallen below some threshold level. The disadvantages of direct communication of the nodes with BS gave us the idea to use multi-hop communication which is made possible by the chain method as used in [53] and it also assures the connectivity of the nodes (although only a fully connected network is assumed). A routing protocol, which works well even when the number of nodes and area is increased is the most suitable for an energy efficient IoT. Problems (1-6) discussed above motivated us to develop a new protocol which could cater to the needs of an efficient IoT. Development of the energy efficient IoT is the challenging issue and its complexity is increased as protocols already developed for WSN a cannot be applied directly to it. The main contributions of this paper include: (1) a hierarchical framework for the IoT; (2) a model for an optimized solution on the basis of the proposed framework for the IoT; (3) a minimum energy consumption algorithm for the optimized model.