1. Iterative Decoding for Redistributing Energy Consumption in Wireless Sensor Networks R. G. Maunder, A. S. Weddell, G. V. Merrett, B. M. Al-Hashimi and L. Hanzo 23 June 2008

2. 2 Overview Wireless sensor network scenario IEEE 802.15.4 physical layer –Standard –Proposed augmentation Practical considerations Error ratio performance Energy savings and complexity Conclusions

3. 3 Wireless sensor network scenario

4. 4 IEEE 802.15.4 physical layer Proposed augmentation to IEEE 802.15.4 PHY Standard IEEE 802.15.4 PHY

5. 5 Features of the proposed augmentation Increased error correction capability –Fewer retransmissions required Reduced transmit power Slightly increased transmitter complexity Significantly increased receiver complexity

6. 6 Wireless sensor network scenario

7. 7 Practical considerations Header conveys synchronisation sequence and payload length Both must be recovered before iterative decoding can commence. Header is transmitted at high power using standard PHY Payload is transmitted at low power using augmented PHY

8. 8 Payload error ratio performance

9. 9 Transmitter energy savings Augmented PHY performs additional processing Values conservatively estimated for Chipcon CC2430 20% reductions in energy consumption

10. 10 Receiver complexity costs

11. 11 Conclusions Physical layer design can be optimised in order to benefit particular wireless sensor network scenarios. Proposed design beneficially redistributes energy consumption from source to sink. –Reduces probability of transmission errors. –Facilitates reduced transmission power. Transforms large payloads (which have a low header overhead) from being undesirable to being desirable. Can interoperate with standard IEEE 802.15.4. Thank you!