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Abstract—Recent years have witnessed an increasing availability of heterogeneous sensor networks that consist of a large number of resource constrained nodes (sensors) and a small number of powerful resource rich nodes (actors). Such heterogeneous Wireless Sensor Actor Network (WSANs) offer improvement of sensor networks' capacity/coverage, energy conservation and network lifetime. This paper investigates the case where sensors are organized into clusters and mobile actors are used for maintaining an energy efficient topology by periodically manipulating their geographical position. We present an elegant technique that allows actor nodes to find an optimal geographical location with respect to their associated cluster heads such that the overall energy consumed is minimized. The proposed technique includes a weighted cost function based on the residual energy levels of cluster heads that allows the mobile actor to optimally fine-tune its geographical location. We present simulation results that demonstrate a significant increase of network lifetime over the traditional cluster based WSN deployments. Index Terms—wireless sensor actor networks, mobile actors, clustering, energy efficiency, network lifetime. I.

Geographic routing has received an increasing attention in the context of Wireless Sensor Networks since it frees the network from the energy-demanding task of building and maintaining a structure. It requires however each node to know its position, which may be a prohibitive assumption for many applications. To this end, some prior work has focused on inferring a node’s location from a set of location-aware anchor nodes. In this work, we free ourselves from positioning techniques and anchor nodes altogether, and introduce and analyze the concept of virtual coordinates. These coordinates are chosen randomly when a node is switched on, and are updated each time the node relays a packet. As this process goes on, the virtual coordinates of the nodes converge to a near-optimal state. When using a greedy geographic approach on top of these coordinates, we show that the number of hops to reach the destination exceeds the shortest path by a few percent only. Moreover, our approach guarantees delivery even when nodes appear/disappear in the network, and under realistic transmission models. We analytically prove the correctness of our protocol. Moreover, extensive simulations are used to show that our position-free solution outperforms existing geographic protocols−such as Greedy-Face-Greedy (GFG) or Greedy Perimeter Stateless Routing (GPSR)−in terms of energy-efficiency, path length and robustness.

Preserving the consumed energy of each node for increasing the network lifetime is an important goal that must be considered when developing a routing protocol for wireless sensor networks. The main objective of cluster-based routing protocol is to efficiently maintain the energy consumption of sensor nodes by involving them in multi-hop communication within a cluster and by performing data aggregation and fusion in order to reduce the number of transmitted messages to the base station (sink) and transmission distance of sensor nodes. In this paper we propose a new approach called (DB-SEP) which cluster heads are selected on the basis of their initial energy and their distances between them and the sink. Experimental results show that our approach performs better than the other distributed clustering protocols such as SEP in terms of energy efficiency and lifetime of the network.

Wireless sensor network is a large number of small battery powered sensors, where the failures of sensor nodes and the loss of connectivity are common phenomena. Therefore, energy consumption is an important issue to achieve a longer network lifetime. Several clustering protocols have been aimed to provide balancing of the residual energy particularly between the clusterheads and minimizing the number of clusterheads. This paper presents a novel clustering algorithm named EDED (Enhanced distributed, energy-efficient, and dual homed clustering) which provides robustness, a distributed cluster formation and reduces the number of clusters (clusterhead) in the WSN. Simulation results confirm that EDED is effective in prolonging the network lifetime and it can further efficiently relay the cluster data.

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