Abstract-Wireless Sensor Networks (WSNs) consist of numerous sensors which send sensed data to base station. Energy conservation is an important issue for sensor nodes as they have limited power. Many routing protocols have been proposed earlier for energy efficiency of both homogeneous and heterogeneous environments. We can prolong our stability and network lifetime by reducing our energy consumption. In this research paper, we propose a protocol designed for the characteristics of a reactive homogeneous WSNs, HEER (Hybrid Energy Efficient Reactive) protocol. In HEER, Cluster Head(CH) selection is based on the ratio of residual energy of node and average energy of network. Moreover, to conserve more energy, we introduce Hard Threshold (HT) and Soft Threshold (ST). Finally, simulations show that our protocol has not only prolonged the network lifetime but also significantly increased stability period. Index Terms-Wireless, Sensor, Networks, Energy, Hybrid, Cluster, Reactive I. RELATED WORK Heinzelman et al. [1] , introduced the first hierarchical clustering algorithm for WSNs, called LEACH. It is one of the most popular protocols in WSNs. The main idea is to form clusters of the sensor nodes. LEACH outperforms classical clustering algorithm by using adaptive clustering and rotating CHs. This saves energy as transmission will only be performed on that specific CH rather than all the nodes. LEACH performs well in homogeneous environment however, it's performance deteriorates in heterogeneous environment. Threshold-sensitive Energy Efficient Network (TEEN) [2] is a reactive protocol for time critical applications. The CH selection and cluster formation of nodes is same as that of LEACH. In this scheme, CH broadcasts two threshold values i.e. Hard Threshold (HT) and Soft Threshold (ST). HT is the absolute value of an attribute to trigger a sensor node. HT allows nodes to transmit the event, if the event occurs in the range of interest. Therefore, this not only reduces transmission to significant numbers but also increases network lifetime. Georgios et al. [3] , proposed a two level heterogeneous aware protocol, consisting of normal and advance (high energy) nodes. It is based on the weighted election probabilities of each node according to their respective energy to become a CH. Intuitively, advance nodes have more probability to become a CH than normal nodes, which seems logical according to their energy consumption. Stable Election Protocol (SEP) does not require any global knowledge of the network. The drawback of SEP is that it does not consider the changing residual energy of the node hence, the probability of advanced nodes to become CH remains high irrespective of the residual energy left in the node. Moreover, SEP performs below par if the network is more than two levels. In [4] , authors proposed Distributed Energy Efficient Clustering (DEEC) protocol for WSNs. DEEC is a clustering protocol for two and multilevel heterogeneous networks. The probability for a node to become CH is based on residual energy of the nodes and average energy of network. The epoch for nodes to become CHs is set according to the residual energy of a node and average energy of the network. The node with higher initial and residual energy has more chances to become a CH than the low energy node. A number of routing protocols have been proposed in the area of WSNs. Most of them are based on CH selection. However, not much attention has been devoted towards time critical applications. Most of the routing protocols are for proactive networks. DEEC, being a proactive heterogeneous network protocol is not well suited for time critical applications. TEEN is a reactive protocol which guarantees that in homogeneous environment, unstable region will be short. After the death of the first node, all the remaining nodes are expected to die on average within a small number of rounds as a consequence of the uniform remaining energy due to the well distributed energy consumption. On the other hand TEEN in the presence of high energy nodes yields a large unstable region. The reason being, all high energy nodes are equipped with almost the same energy however, the CH selection process is unstable and as a result most of the time these nodes are idle, as there is no CH to transmit. Hence, in our research paper we focus on developing a protocol that gives us better results for time critical applications in both environments i.e. homogeneous and heterogeneous environment. We define following parameters which evaluate and compare the performance of clustering protocols.
HEER REF is a cluster based reactive routing protocol which uses residual energy of nodes and average energy of the network for the selection of CH.
HEER: Hybrid Energy Efficient Reactive Protocol for Wireless Sensor Networks
2013 Saudi International Electronics, Communications and Photonics Conference
2013 Saudi International Electronics, Communications and Photonics Conference
Computer Science