of Service (QoS) a b s t r a c t
To support energy-efficient routing, accurate state information about energy levels should be available. But due to bandwidth constraints, communication costs, high loss rate and the dynamic topology of MANETs, collecting and maintaining up-to-date state information is a very complex task. In this work, we use Optimized Link State Routing (OLSR) as the underlying routing protocol and explore the accuracy of state information under different traffic rates. We are focusing on energy level as QoS metric, which has been used for routing decisions in many energy-efficient routing protocol proposals. First, we show that the accuracy of the available nodal energy level does impact the performance of energy-efficient variations of OLSR. If nodes learn other nodes' energy level through protocol messages, fewer packets tend to get delivered in an energy-constrained network, in particular under high traffic loads or in mobile networks. We analyzed the accuracy of the reported energy levels for the static scenarios and found that the propagated values are highly inaccurate, in particular under high traffic rates. Tuning the OLSR protocol parameters has no noticeable impact on accuracy levels. We then propose two additional techniques to increase accuracies and compare the different techniques against each other and against the basic OLSR protocol. One of the techniques, which we call smart prediction, achieves highly accurate perceived energy levels under all traffic loads. We finally show that the proposed smart prediction technique also works well for mobile networks and more heterogeneous wireless interfaces.