Wireless the key to saving Great Barrier Reef

The Great Barrier Reef (GBR) stretches for some 3000 km along the east coast of Queensland. However, scientists worry that if current climate changing effects continue, this iconic system may not survive. But as Dr Graham Woods discovered, wireless technology can lend a hand.

According to Dr Woods, from James Cook University, concerns over the GBR's long-term health have led to increased interest in measuring the cause and effect of phenomena like coral bleaching.

"Monitoring both the variation of physical variables (temperature, light levels) as well as chemical and video monitoring of reefs across wide geographic regions will be a critical data resource if we are to understand the extent of reef health and primary triggers of events that degrade reef systems," Dr Woods said.

The Great Barrier Reef Ocean Observing System (GBROOS) was set up to provide an observation network for oceanographic and ecosystem monitoring within the GBR. This system collects wind data on numerous climatic variables.

However, as Dr Woods points out, monitoring a marine system of 350,000 square km is no simple task. One potential approach to this problem is to use wireless sensor networks. However, broadcasting this mammoth amount of data to the Australian mainland - a distance of several kilometres - presents a problem.

The Australian Institute of Marine Science (AIMS) has taken steps to rectify this situation, by developing a high-capacity microwave link between its Townsville headquarters and a weather tower on Davies Reef.

"Amazingly, this link operates over a range of some 78 km using a frequency of 10.6 GHz and antennas positioned just 7 m above the sea surface," Dr Woods said.

This feat was accomplished through a technique developed by Dr Woods. By trapping the radio signal in the evaporation dust that forms just below the ocean surface, the signal can be propagated greater distances, beyond the horizon.

EM Solutions supplied their 10.6 GHz EtherMux for the microwave link between Townsville and Davies Reef. This equipment was suited to the task as it provided a close match to the optimum frequency needed to utilise Dr Woods' evaporation ducting technique. EM also tailored the link software to perform error correction in order to provide a receiver sensitivity approaching -90 dBm at a data rate of 10 Mbps.

This feature ensures the link achieves the best possible availability, even when weather conditions only produce a weak evaporation duct.

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