1. IEEE Vehicular Technology Conference Los Angeles, September 27-29 2004 Antenna Actuation for Radio Telemetry in Remote Sensor Networks University of California at Los Angeles David Browne, Vishwa Goudar, Henrik Borgstrom, Michael Fitz, William Kaiser

2. Slide 2 Remote Sensor Networks Three characteristics: 1.Nodes deployed sparsely over large geographic regions 2.Nodes gather local data on a natural phenomenon 3.Nodes need to communicate sensor data Example: UCLA Broadband Seismic Network Array (Thanks to Igor Stubailo and John Propst for graphics.)

3. Slide 3 Remote Sensor Networks Goal: Enable telemetry of sensor data between nodes Benefits: ad hoc deployment self assembling self healing Limitations: Poor range Low energy efficiency Known solution: Radio telemetry over omni-directional or sector antenna Better solution: Highly-directional antennas with rotational actuation

4. Slide 4 Benefits of Directional Antenna azimuth azimuth & elevation Measured Path Loss: 40dB/decade is typical Range improvement: Omnidirectional: 80dB loss @ 130m 15dBi Directional: 80dB loss @ 750m Efficiency improvement: A link over 15dBi antennas is 1000x more energy efficient

5. Slide 5 Actuated Network Assembly Initial antenna orientation Antenna orientation after articulation

6. Slide 6 The First Contact Problem Missing information: Direction to other nodes. Search coordination Energy Considerations: search depletes energy global vs. local maxima Q: How to shorten the first contact search? A: coordination & geolocation.

7. Slide 7 Wideband vs. Narrowband Radios 802.11b Radio: 2.44 GHz 20MHz Bandwidth 100m range (omni) UCLA Narrowband Radio: 220 MHz 4 kHz 2 mile urban range (omni)

8. Slide 8 Search Strategies

9. Slide 9 Field Test Results

10. Slide 10 Field Test Conclusions Blind vs. Geolocation and/or Coordination  reduced search duration from 1.5 hours to 15min Coordination only  search times are independent of range. Geolocation only  excellent short range (0m – 500m) search times (10s)  exponentially deteriorating performance after 500m Coordination & Geolocation  excellent range independent search times (10s)

11. Slide 11 Conclusions on Directional Antenna Actuation Benefits common with omni/sector solutions ad hoc deployment self assembly self healing Advantages over omni/sector solutions: range energy efficiency Disadvantage: latency due to actuation latency due to actuation  Importance of minimizing search time.

12. Slide 12 What’s Next

13. Slide 13 End of Presentation Questions and Comments

14. Slide 14 Search Algorithms A. Blind Search (baseline) 802.11b radios search for >threshold coordinate. Exhaustive search for the global maximum. Upper bounds all strategies. B. Coordinated Search Coordination via LR radios. Nodes begin 180º out of phase. Nodes complete one rotation. Link guaranteed within one rotation. Lower bound for coordination. C. Blind Search & Geolocation Random walk (speed & dwell). 802.11b radios search for >threshold coordinate. GPS coordinates exchanged over 802.11 radios for LOS alignment. D. Coordination & Geololation GPS coordinates exchanged over LR radios. Immediate LOS alignment.

15. Slide 15 (# Coordinates > Threshold) vs. Range

16. Slide 16 Strategy C Simulation

17. Slide 17 The Link Search Space Simulated Link Search SpaceMeasured Link Search Space