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Cross-layer Design & Optimization for Wireless Sensor Networks

Cross-layer Design & Optimization for Wireless Sensor Networks. Weilian Su and Tat L. Lim Department of Electrical and Computer Engineering Naval Postgraduate School. Outline. Objectives Framework Approach Results & Findings Conclusions. Objectives.

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Cross-layer Design & Optimization for Wireless Sensor Networks

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  1. Cross-layer Design & Optimization for Wireless Sensor Networks Weilian Su and Tat L. Lim Department of Electrical and Computer Engineering Naval Postgraduate School

  2. Outline • Objectives • Framework • Approach • Results & Findings • Conclusions

  3. Objectives • Develop a framework for the cross-layer design and optimization study • Investigate & explore the various areas where performance gains can be achieved in the context of WSNs

  4. OSI Stack Application Top-down feedback Optimization Agent (OA) Presentation Session Transport Bottom-up feedback Network OA Data Link (MAC/Link) Physical Intra-layer interactions Inter-layer interactions Cross-layer Design Framework

  5. Approach -> Approach: Study the effects of the wireless channel and performance at PHY to develop insights that can be used to design the optimization agent (OA) • Tapped delay line implementation for wireless channel modeling • Performance measurements using the micaz motes from Crossbow, Inc.

  6. Tap Delay Line (TDL) Implementation • 2-TDL channel model • 12-taps TDL channel model from GSM REC.05-05 model to validate the results

  7. x(t) Transmitted signal τ1 τ1- τ2 Doppler Filter (Jakes) Doppler Filter (Jakes) AWGN y(t) : Received signal TDL implementation • 2-TDL Model Delay

  8. Results & Findings (1): TDL implementation (a) BER of 2-TDL model (b) BER of 12-TDL model (GSM REC.05-05)

  9. Performance measurements of WSN using Micaz Motes • Interference / Co-existence problems • Transmission range & power transmit levels

  10. IEEE 802.15.4 channels Overlap Overlap Overlap IEEE 802.11b channels Interference Measurements:Frequency Spectrum Overlapping of frequency bands between IEEE802.15.4 and IEEE802.11b channels within 2.4 GHz ISM band

  11. IEEE802.11b Ad-hoc Network channel 1 5 m Laptop 1 Laptop 2 Micaz mote Node 2 Micaz mote Node 0 (Base) 5 m 3 m MIB600 Micaz mote Node 1 IEEE802.15.4 Channel 11 Laptop 3 10 m Micaz mote Node 3 Experimental Setup for Interference Measurements • Setup 2 networks: • IEEE802.15.4 network (using 4 micaz motes) • IEEE802.11b (via 2 laptops) – interference source

  12. Results & Findings (2): Interference Measurements 73% 100% (b) Interference turned off • Interference turned on

  13. Results & Findings (2): Interference Measurements Node 1 & 2 (@ <5 m) unaffected by interference Interference Period Node 3 (@ 10 m) more affected by interference Packets received rate

  14. Results & Findings (3): Transmission range and power levels • Maximum transmission range of 55-60m Transmission range for micaz motes set at max power of 0 dBm

  15. Conclusions • Increasing BER under mobility conditions • Possible interference within ISM bands and can affect the performance of WSN (especially for long links/hops) • Max range for micaz motes is around 60m and recommended operating range < 30m • Many factors need to be considered in the design of WSN • Insights gained can be used to design and develop the optimization agent, to enhance the performance of wireless sensor networks

  16. Q & A Thank You

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