Once considered an impossibility, CSIRO Telecommunications and Industrial Physics (CTIP), with funding support from the Australian Coal Research Program (ACARP), has developed two-way wireless through-rock communications technology which does not require an underground contiguous physical infrastructure.

Research leader, Colin Jacka said the technology has the potential to significantly improve productivity and safety in underground mines.

This effectively continues the work of the late 1980s which saw the development by CTIP of an initial system consisting of a one-way link from the surface to miners underground, subsequently marketed by Mine Site Technologies as the PED (Personal Emergency Device).

The 1994 Moura disaster in which 11 people died had highlighted the need for an effective communication system in place at a mine to enable personnel to assess all of the vital pieces of information available. CSIRO's brief was to establish a system to facilitate bi-directional low bit-rate data communications between the surface control room and personnel underground. The system had to be robust enough to remain intact after other communications systems or mine infrastructure had failed. It was to be a permanent, disaster-resistant, two-way, multiple connectivity between the mine and the surface.

Where the PED system has been successful is in allowing a mine to get messages to underground staff under normal operating conditions and in emergency situations where existing communication infrastructure has been damaged or disabled.

"However, the coal industry has placed high importance on being able to obtain information from trapped miners, ie communications from any part of the mine underground to the surface," Jacka said. "This is a much more difficult problem than communications from the surface to the underground miners."

Jacka said lthough it seemed logical to look to wireless-based solutions, radio propagation in confined underground spaces is complex, and portable equipment suffers from power limitations.

The solution was to be found in sophisticated digital communications and coding techniques used in the telecommunications industry and further developed at CSIRO, along with the availability of new Digital Signal Processing (DSP) technology.

The CSIRO system concept consists of a surface station, a number of fixed links underground and a collection of portable units to be carried by the miners. All communications between the miners and the surface is through-the-rock wireless. Demonstration of the integrated proof-of-concept system took place at Dartbrook Colliery in March 1999.

CSIRO's work since then has further developed the technology to become more appropriate as a multi-user demonstrator in preparation for commercialisation by an industry partner.

"However, even though the concept has been proven in field trials, considerable investment will yet be required to develop and market a product suitable for the coal mining industry," said Jacka. "The object of the project has been to demonstrate the feasibility of an emergency mine communications system, not to produce a prototype system that could rapidly proceed to an operational system  there is much to be done between these two milestones. Off-the-shelf hardware has been used whenever possible, and very little attention at this stage has been paid to energy, size and cost constraints necessary for later development."

The field trials have demonstrated that messages between a fixed surface station and a portable unit underground can be compiled, edited, transmitted and read. The present concept demonstrator consists of a surface unit, a base-station, and two portable units. Jacka said considerable thought has been put into issues related to reliability and cost effectiveness of a potential commercial product. A patented system architecture which addresses these issues has been outlined.

CSIRO is currently negotiating with Australian industry for the further commercial development of the technology.

Dr Jacka was recently the recipient of the ACARP Occupation Health & Safety award at the 2000 Australian Coal Conference and Trade Exhibition held at the Gold Coast on 9 May.