%0 Journal Article %T Energy Efficiency Adaptation for Multihop Routing in Wireless Sensor Networks %A Abdellah Chehri %A Hussein T. Mouftah %J Journal of Computer Networks and Communications %D 2012 %I Hindawi Publishing Corporation %R 10.1155/2012/767920 %X Wireless sensor networks (WSNs) are considered as a suitable solution for long-time and large-scale outdoor environmental monitoring. However, an important feature that distinguishes the WSNs from traditional monitoring systems is their energy constraints. In fact, these nodes have often a limited and usually nonreplenishable power source. Therefore managing these limited resources is a key challenge. In this paper we use an optimization scheme based on adaptive modulation and power control for a green routing protocol. The optimization mechanism is subject to certain QoS requirements in terms of total end-to-end delay time and bit error rate. The simulation results show that the proposed algorithm can, theoretically, reduce the consumed energy of the sensor nodes almost to half. 1. Introduction Wireless sensor networks (WSNs) are one of today¡¯s most interesting emerging technologies. WSN is made up of a large number of inexpensive devices that are networked via low-power wireless communications [1]. The development of this attractive network has open many doors for a several number of ¡°new and exciting¡± applications, in which flexibility, easy deployment, and configuration are important properties. Amongst a diverse set of applications where WSN can be used we can quote precision agriculture, environment monitoring, fire detection, smart home, intrusion detection, localization, medicine, and many others. In addition, the wireless sensor networks are working in ad hoc fashion. The self-configuring, self-healing characteristics make a WSN autonomous wireless network, and therefore allow them a great advantage in a large number of situations. A large number of WSN applications are composed of stationary nodes. These nodes transmit the collected data at relatively low rates, with a focus to route the data to a central base station. However, one important feature that distinguishes sensor networks from traditional monitoring systems is their nonreplenishable energy, where the sensor nodes are battery-power limited. It is commonly accepted that the main design goal in wireless sensor networks is the reduction of energy costs. In fact, energy efficiency is an important point emphasized in the vast majority of relevant publications, since energy reserves are usually considered to be finite. Energy consumption can be affected by all layers of the network, ranging from physical to application layer. Several energy management strategies have been investigated of a WSN [2¨C6]. The main works focus on efficient topology design (tier layer networks versus flat %U http://www.hindawi.com/journals/jcnc/2012/767920/