## 5 Analysis of Prominent Clustering Routing Protocols in WSNs
### Cluster-Construction Based Clustering Routing Protocols
#### 5.1.8 Eeuc  
Energy-Efficient Uneven Clustering (EEUC) algorithm, proposed by [PERSON] _et al_. [23], is a clustering and distributed competitive algorithm, where CHs are elected by localized competition, which is unlike LEACH. Every node has a pre-assigned competitive range, which is smaller as it gets close to the BS.  
This makes EEUC an unequal clustering approach for the purpose of balancing energy consumption among CHs and solving the hot spots problem. During the process of CH election in EEUC, each node generates a random number, and only the node whose number is greater than a threshold will be activated for CH election by broadcasting compete message within a competition radius which is determined by its distance to the BS. The competition radius of node \(s_{i}\) is given by:  
\[s_{i}.R_{comp}=\biggr{[}1-c\,\frac{d_{max}-d(s_{i},BS)}{d_{max}-d_{min}}\biggr{]} R_{comp}^{0} \tag{10}\]  
where \(R_{comp}^{0}\) is the maximum competition radius which is predefined, \(d_{max}\) and \(d_{min}\) denote the maximum and minimum distance between sensor nodes and the BS, \(d(s_{i},\,BS)\) is the distance between node \(s_{i}\) and the BS, \(c\) is a constant coefficient between 0 and 1. According to Equation (10), the node's competition range decreases as its distance to the BS decreasing. Accordingly clusters closer to the BS have smaller cluster sizes, thus they will consume lower energy during the intra-cluster data processing, and can preserve more energy for the inter-cluster relay traffic. If a sensor node decides to participate to the competition, which is based on the residual energy of each tentative CH, it becomes a tentative CH. Then, tentative CHs in local regions compete in order to become a real CH.  
In EEUC, multi-hop routing is used for inter-cluster communication. The CHs choose relay nodes for data transmission according to the nodes' residual energy and distance to the BS. In other words, a CH would choose the one with more residual energy as its relay node from the two whose communication cost are the least among all of its neighbor CHs.  
According to above discussion, the disadvantages of EEUC are as follows: (1) To address the hot spots problem, EEUC introduces an unequal clustering mechanism to balance the energy consumption among CHs. Accordingly, the unequal clustering mechanism in EEUC improves the network lifetime over LEACH and HEED; (2) Based on communication cost, this protocol can save more energy via inter-cluster multi-hop routing mechanism in steady state phase, because a CH would choose its relay node from the two whose communication cost are the least among all of its neighbor CHs.  
However, there are several drawbacks in EEUC as follows: (1) Performing of clustering in each round imposes significant overhead, because each node must broadcast and receive a large amount of competition message for CH election, even though most of them cannot win and most of the elected nodes are not suitable to be as CHs; (2) The extra global data aggregation can result in much overhead for all nodes and deteriorate the network performance; (3) The routing scheme can result in new hot spots, in that only one of the two nodes whose communication costs are the least among the neighbor CHs can be relay nodes, even though both of them have little residual energy.