Energy Issues and Energy aware Routing in Wireless Ad-hoc Networks

The problem of energy efficiency in MANETs can be addressed at different layers. In recent years, many researchers have focused on the optimization of energy consumption of mobile nodes, from different points of view. Some of the proposed solutions try to adjust the transmission power of wireless nodes, other proposals tend to efficiently manage a sleep state for the nodes (these solutions range from pure MAC-layer solutions (as the power management of 802.11) to solutions combining MAC and routing functionality). Finally, there are many proposals which try to define an energy efficient routing protocol, capable of routing data over the network and of saving the battery power of mobile nodes. Such proposals are often completely new, while others aim to add energy-aware functionalities to existing protocols (like AODV, DSR and OLSR). The aim of energy-aware routing protocols is to reduce energy consumption in transmission of packets between a source and a destination, to avoid routing of packets through nodes with low residual energy, to optimize flooding of routing information over the network and to avoid interference and medium collisions. Many energy efficient routing protocol proposals were originally studied for sensor networks, where the limited energy of nodes is a strong constraint; in MANET, however, the requirements are different: a node has generally more hardware resources (capable of better performance, but consuming more energy) and the protocol must preserve the resources of every node in the network (not only a subset of them, because each node can be, at any time, source or destination of data). A single node failure in sensor networks is usually unimportant if it does not lead to a loss of sensing and communication coverage; ad-hoc networks, instead, are oriented towards personal communication and the loss of connectivity to any node is significant. In the routing protocol design of mobile nodes, many issues need to be considered in order to offer many important properties such as scalability, QoS support, security, low power consumption and so on. In this chapter we focus on the energy issues facing some important aspects going from the energy model definition for the computation of the energy consumption to energy-aware metrics definition and routing protocol design. If a network composed of mobile nodes communicatiing using a wireless radio and where each node can communicate with each other using the other mobile nodes as relay nodes is applied in a communication system, many challenging design issues need to be addressed. MANET technology became, in the last years, more commercial in comparison with the past where it was used for military purpose and this implies more additional features to offer to the end-