by Graham Woods School of Engineering, James Cook University

Contents Why do we need communications on the GBR? How do we implement communications on the GBR? Results from first EVER link. Conclusion

Introduction What is the problem? –The GBR is a large, remote and complex system. Would like to monitor; Coastal Runoff (fresh water, silt, fertilizer) Coral Bleaching (temperatures, light) Human Impact (fishing, shipping, security) Pests (Crown of thorns) Science (24-7 video footage) LOTS OF DATA eg 260Gb for 1month of video!

Introduction cont. How do we monitor now? –Fixed weather stations (HF radio links) BOM Link –Data loggers How will we monitor in the future? AIMS Automatic Weather Station (AWS) at Myrmidon Reef approximately 120km NNE of the City of Townsville, North Queensland (Australian Institute of Marine Science)

Proposed Network Short Range Sensor Networks on Individual Reefs communicating with each other and the mainland via high speed links. X X X X X X X X X X X X X X X X X X

Base Node Central “hub” for sensor monitoring system Sensor nodes deployed around hub Nodes form wireless ad-hoc network.

How do we get data to mainland? ?

Communication Options OptionsSpeed (bps) Max. Range (km) Running Cost ($/day) Purchase Cost ($) Availability (%) Comments HF Radio s<1<10,00095+Slow G3 phone4k (up)200<2<1,00099+Slowish Satellite s<3,00099+Speed/ cost Microwave Link 10M+?200?<1<50,00090+?Purchase Cost

Microwave Link ? Would provide high speed data transfer needed. BUT how could we achieve a range of 100km plus! Novel method “communications via the evaporation duct”

Conventional radio link – Standard Atmosphere Need 100m high towers!

Evaporation Duct Recall: Decreasing moisture content above the ocean surface  trapping layer. “Evaporation duct height” – reflects the strength of the duct.

Ray Path Over Ocean Note : Signal trapping above ocean

Field predictions 2.5GHz5.5GHz 10.5GHz

Optimum Frequency and Antenna Height Optimum point: Freq = 10.5 GHz Height = 3.7 m

Proposed Microwave Link Location : Davies Reef to Australian Institute of Marine Science (AIMS) Operating Frequency : 10.5GHz ! Power : 1/2 W ! Range : 78 km! Height ASL : 5 m! Data rate : 10Mbps!

Predicted Link Operation Commercial System : emSolutions Ethermux F=10.6GHz, Pt = 27dBm, Gt=Gr=40dB, Estimated Path Loss 140dB, Signal Power: Bw = 20MHz, Ta = 300 kelvin. Noise Power: Signal to Noise Ratio = 77dB Link: Pr(dBm) = Pt(dBm) +Gt(dB) – PathLoss(dB) + Gr(dB) Pr(dBm) = = -33dBm Noise = k × Ta × Bw = -110dBm Pr

Trial Davies to AIMS Link Avg 170dB path loss, 15dB diurnal variation Tx Rx

Actual Link Davies Reef AIMS pump house

Measured Performance 20/21 th August :30 to 16:30 30/31 st August, :30 to 16:30 Min Path Loss = 167dB

Real Demonstration Web Camera on Davies Reef Realtime video feed, 10 frames/second. Web Cam

Practical Considerations

Fouling from sea birds is a major problem. Practical Considerations

Conclusion ☺ Worlds first high speed over ocean link to Great Barrier Reef. ☺ Enabling technology for reef monitoring.  Path Loss more than predicted.  Availability less than predicted

Questions? See