Poster Abstract: A Lifetime-Efficient Forwarding Strategy for Wireless Sensor Networks

1. MOTIVATION Sensor Networks are mainly designed for habitat and environmental monitoring where many sensor nodes gather data that is then sent towards one or more sink nodes. Since all nodes are scattered over a wide area in most cases, they cannot communicate with the sink directly. Instead, intermediate nodes are used for message forwarding. For such many-to-one communication, some routing algorithms use distance-based forwarding where the number of hops serves as a distance metrics. However, simple hop-based approaches achieve poor results concerning data delivery and energy consumptions [1, 4]. In [1], we proposed another forwarding strategy called Single-Link Energy-Efficient Forwarding (SEEF) that uses an energy efficiency metric. The energy efficiency is defined as the ratio between the delivery rate and the energy required for the message to reach the sink. Furthermore, we introduced the concept of multi-link forwarding. In general, nodes that are not addressed in the packet header as the destination may temporarily turn their radio unit off to save energy. However, it might be more efficient if some nodes stay awake and overhear the packet. In case of packet loss, that might prevent retransmissions of the entire packet. If the actual receiver does not acknowledge the packet, another node may do so instead. The decision which nodes should operate in such a backup mode is due to the MultiLink Energy-Efficient Forwarding (MEEF) strategy. As shown in [1], MEEF performed best among a comprehensive framework of different forwarding strategies. However, one problem that occurs during the lifetime of the network is that some paths are used more frequently than others. Nodes along these paths will spent more energy and die pretty soon. This problem is also known as the Maximum Lifetime Problem [3]. In the following sections, we will tackle this problem and present a new Lifetime-Efficient Forwarding strategy that incorporates the amount of a node’s remaining energy into the forwarding metrics to prevent the early “burn out” of specific paths.