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Back to shore – delivering a robust communications system from sea

Company:

Wood & Douglas’ client was a large mining multinational company based in Southern Africa. The client has mining operation both on-shore and offshore. The offshore operation uses a fleet of five large drilling vessels, processing product in situ at sea.

The fleet had been using Satellite communications to carry voice and data traffic from the ships, which are mining up to 80 kilometres from the shoreline, to the company’s headquarters some 1000 kilometres in land.

 Issue:

The satellite link had a relatively low data capacity. It was also an expensive means by which to communicate from ship to shore. Mechanical and electrical problems in the equipment on board the ships had led to issues of reliability – a critical concern for a business that depends on effective communication in a challenging and uncompromising environment.

Wood & Douglas were asked to scope a potential alternative solution that would be more reliable and effective, as well as enabling a significant increase in data capacity to allow CCTV security monitoring to be transmitted to headquarters as well as general internet traffic.

The assignment was challenging for a number of reasons: the ships operated within a mining area that extended 200 kilometres along the coast and up to 80 kilometres out to sea; ruling out any form of Wi-Fi solution. Yet line of sight communications with five vessels anywhere within a 16,000 square kilometre ocean would provide a significant radio challenge.

 Solution:

Initially trialled on one vessel, Wood & Douglas devised a system that would use line of sight radio to communicate securely from the ships to a base station on shore where the communications would then be routed to headquarters via the internet.

Wood & Douglas provided a transmitter and receiver combination at both the vessel and the shore station. This duplex communications enabled IP traffic to be transmitted across the link as well as the CCTV video images. The link in each direction operated on a different radio frequency and careful engineering ensured the two links did not cause each other interference.

One of the particular challenges of working at sea is the constant movement can make the transmission and receipt of wireless signals difficult. Wood & Douglas overcame this by combining several different wireless techniques. COFDM technology enables data to be spread right across a radio transmission meaning that if part of the transmission is lost, there is enough error correction from the balance of signal received to make good.

Combined with an antenna technique called diversity, whereby the receiver stations consist of two receivers both listening for the transmission on different antenna and dynamically choosing the strongest transmission, Wood & Douglas were able to provide an incredibly robust solution.

Finally, panel antennas were deployed at the base station to provide the breadth of transmission to cover the whole sea mining area. On board the vessel, yagi antennas were deployed, mounted on a mast with a rotator on the base. The rotator constantly monitors the location of the ship to ensure the antenna is always pointing to shore.

Once the trial system was deployed the mining company experienced a data throughput rate of around 5 Mbps, enough to transmit standard definition CCTV images and IP traffic. The success of the trial has led to a roll out of the solution to all five ships and the creation of a new shore station including a 60 metre antenna. Since the on-going cost of transmission from ship to shore has fallen to zero, the mining company is saving considerable cost against the previous satellite system.

  • Highly robust ship to shore communications system
  • Reliable data and video communications in challenging environment
  • Costs reduced and data throughput drastically increased

It is our aim to never promise what we cannot deliver.