Energy-centric routing in wireless sensor networks Jamal N. Al-Karaki * , Ghada A. Al-Mashaqbeh Computer Engineering Department, The Hashemite University, Zarqa 13115, Jordan Available online 27 February 2007 Abstract Since energy is a valuable resource in Wireless Sensor Networks (WSNs), it is important to continuously monitor the status of this valuable network resource after network deployment. The information about energy status can be used to early notify both sensor nodes and Network Deployers of resource depletion in some parts of the network. It can also be used to perform energy-efficient routing in WSNs. In this paper, we propose a scheme for monitoring residual energy distributions at different parts of the network through a mech- anism called Energy Centric scale (ECscale). ECscale is then used to perform optimal as well as approximate Energy-Centric Routing (ECR) in WSNs with the objective of maximizing the network lifetime. The proposed algorithms make use of a fixed virtual wireless backbone that is built on top of the physical topology. Simulation results show that our scheme is scalable and can provide many folds of energy savings when compared to conventional routing schemes. Ó 2007 Published by Elsevier B.V. Keywords: Sensor networks; Energy centric; Routing; Wireless networks; Resource monitoring; Aggregate views 1. Introduction Wireless Sensor Networks (WSNs) is a class of wireless ad hoc networks in which sensor nodes collect, process, and communicate data acquired from the physical environment to an external Base-Station (BS), hence allowing for moni- toring and control of various physical parameters [1]. How- ever, WSNs pose unique challenges for designers of such networks. Among these challenges, sensor nodes in WSNs are normally battery-powered, and hence energy has to be carefully used in order to avoid early termination of sensors’ lifetimes [7]. As such, the concept of continuous monitoring of network resources becomes a very important topic in WSNs. This same concept has been already investigated in many other environments, e.g., power plants [2], and in many distributed systems [4]. However, the ideas proposed for such environments seems not to be directly applicable to WSNs. This is mainly due to the unique properties of WSNs that dis- tinguish them from other environments. The importance of monitoring system resources stems from the fact that the reported resource status can be useful in many aspects. First, it can be used to early notify both sensors and deployers of resource depletion or node fail- ures in some parts of the network [9]. Second, deploying more sensors in the field can be guided by the monitoring tool and hence future deployment would target places that are going to die or their energy reserves are becoming low. Finally, routing decisions and network topology can be updated based on the reports of the monitoring tool. In particular, energy-efficient routing in WSNs can benefit from such abstraction by avoiding areas in the network with low energy reserves. In this paper, we address the issue of resource monitoring and energy-efficient routing in WSNs. These two related issues are tackled as one problem with the objective of max- imizing the network lifetime. First, we propose an efficient energy resource monitoring scheme for WSNs. Analogous to a topographic map, our scheme abstracts the geograph- ical distributions of network resources, namely, the energy concentrations in the sensor field into prescribed levels. Instead of providing a detailed information of residual energy at individual sensor nodes, our scheme depicts an aggregated picture (or abstracted view) of the remaining 0141-9331/$ - see front matter Ó 2007 Published by Elsevier B.V. doi:10.1016/j.micpro.2007.02.008 * Corresponding author. Tel.: +962 5 3903333x4872; fax: +962 5 3826613. E-mail addresses: jkaraki@hu.edu.jo (J.N. Al-Karaki), ghada.ayed@ gmail.com (G.A. Al-Mashaqbeh). www.elsevier.com/locate/micpro Microprocessors and Microsystems 31 (2007) 252–262