## 2 Literature Survey
This makes the cluster size bigger for a farther elected cluster head and smaller for a nearer elected cluster head. Each non-cluster-head node chooses the nearest cluster head and sends the Join_Msg which contains the id and residual energy of this node. The authors also modified this technique for heterogeneous networks by introducing an energy factor in the radio range competition radius in order to maximally exploit the higher energy nodes. A cluster member node senses the environmental physical quantity, and communicates it to its CH. The CH collects the data, aggregates it and transmits it to that node in its communication range which is closest to the BS in the case where the distance of the CH from the BS is less than the defined threshold distance. The inverse case results in direct communication of data if more than one node with the same \"distance to BS\" exists, then a higher precedence is given to the highest energy carrying node. Apart from the abovementioned, there is a long list of energy-aware routing protocols in WSNs. An updated survey of clustering routing protocols is WSN is given by [PERSON] in [19]. Table 1 gives an abstract view of a comparative analysis of clustering algorithms on various network design and operational parameters. A brief description of parameters used in this table is given below. * **Node Type**  
Type of deployed nodes according to their configuration. * _Homogeneous:_ all the network nodes have the same configuration (energy, processing power, _etc._)
* _Heterogeneous:_ Nodes in the network have different configurations (energy, transmission range, antenna gain, processing power, _etc._). * **Communication to Sink**  
On data collection at the CH, a communication style is chosen to let it reach the BS either through direct communication or through multi-hop communication. * _Multi Hop:_ CH communicates the data to BS through some transient node (CH, or gateway node). * _Direct Hop_: CH communicates the data to BS without using any transient node. * **Inter-Cluster Communication Style**  
Communication of data between adjacent clusters for further transmitting it to a BS. * _CH--CH_: CH communicates the data to its next CH. * \"-\": CH either transmits the data directly to BS or the authors do not mention this routing aspect in the paper at all. Another possibility exists, _i.e._, a CH does not communicate the data to the next CH but rather it is a gateway node that is selected to transmit the data directly to a BS. * **Intra-Cluster Communication Style**  
Cluster member node communicates the data to CH either directly or indirectly. * _Direct:_ a CM node communicates sensed or collected data to a CH without using any transient node. * _Multi Hop_: a CM node communicates sensed or collected data to a CH thorough some transient node. * \"-\": the authors don't discuss intra-cluster communication style in their paper. * **Cluster Size**  
Size of cluster in network with respect to number of CM nodes. * _Equal:_ No. of CM nodes in network clusters are almost same. * _Unequal_: No. of CM nodes in network clusters is variable enough to make their size very different from each other. * **Cluster Design**  
The process of grouping network nodes in clusters is based on some defined parameter. * _Centralized_: The process of cluster design is controlled directly from a BS. * _Distributed_: The process of cluster design is distributed. Nodes communicate with each other to do this process. * **Suitability to Network Size**  
Size of network with respect to deployment area for which the algorithm works efficiently. * _Small:_ Network nodes communicate directly to the BS without any transient node. * _Large_: Network nodes communicate indirectly to the BS through a number of transient nodes. * _Medium_: Network nodes communicate indirectly to a BS through one transient node. * **CH Election Criteria**  
A node elected to head the activities of a cluster is called CH. This election is based on some election parameter.