Overview

Information routing in wireless sensor networks can be made robust and energy-efficient by taking into account a number of pieces of state information available locally within the network.

1. Link quality: As we discussed in Chapter 5, link quality metrics (e.g. packet reception rates) obtained through periodic monitoring are very useful in making routing decisions.

2. Link distance: Particularly in case of highly dynamic rapidly fading environments, if link monitoring incurs too high an overhead, link distances can be useful indicators of link quality and energy consumption.

3. Residual energy: In order to extend network lifetimes it may be desirable to avoid routing through nodes with low residual energy.

4. Location information: If relative or absolute location information is available, geographic routing techniques may be used to minimize routing overhead.

5. Mobility information: Recorded information about the nearest static sensor node near a mobile node is also useful for routing.

We examine in this chapter several routing techniques that utilize such information to provide energy efficiency and robustness.

Metric-based approaches

Robustness can be provided by selecting routes that minimize end-to-end retransmissions or failure probabilities. This requires the selection of a suitable metric for each link.

The ETX metric

If all wireless links are considered to be ideal error-free links, then routing data through the network along shortest hop–count paths may be appropriate. However, the use of shortest hop–count paths would require the distances of the component links to be high.