The Australian Communications and Media Authority (ACMA) said it used an "evidence-informed" approach in determining that 10MHz of the 800MHz spectrum band would be suitable for the dedicated networks of emergency service organisations.
The authority came under criticism earlier this month from the Police Foundation of Australia (PFA) over its decision to set aside 10MHz of the 800MHz spectrum band for emergency services, rather than the 20MHz of 700MHz spectrum that they had requested. The PFA described the ACMA as "arrogant" in its treatment of the needs of emergency service organisations.
At a hearing for the inquiry into public service broadband in Canberra today, ACMA member Chris Cheah defended the ACMA's handling of the spectrum allocation.
"The ACMA pays particular regard to arguments based on structured evidence, based on solid demand evidence and engineering analysis, and generally preferences such evidence over simplistic or emotive assertions," he said.
He said that an independent analysis undertaken as part of the review conducted by the government prior to the 800MHz found that 10MHz would have been sufficient for four out of the five emergency scenarios tested as part of the review, including major events and natural disasters.
"The fact is the [review] identified only one scenario about an extreme, hypothetical event, which, thank goodness, has never occurred in Australia, which the report concluded that more spectrum would be required," he said.
"In that event, even the communications needs were predicted of not being supported even by the 20MHz of spectrum that agencies are now arguing they need."
He said that valuable spectrum should not be left unused on standby, and agencies should have agreements in place with the mobile carriers so they can scale up their communications capacity as required.
Emergency service organisations have sought to compare the Australian situation to that in Canada, the US, and Europe, while Maureen Cahill, the ACMA's general manager of the communications infrastructure division, said Australia is very different.
"There is an issue of population density, [and] the number of first responders, which are unique to every country. So I actually do believe it is very difficult to draw those direct comparisons and have any faith that it is a natural comparison between Australia's volume of first responders, density of the city populations of either Canada, Europe, and the US," she said.
"Our approach is very different, the model that we have put in place has been a model that is specifically for Australia's conditions and what our public safety agencies have indicated is doable in terms of delivering the capability."
Today's hearing was the last hearing of the current parliament before the September election.
The hearing came as Communications Minister Stephen Conroy today issued draft ministerial directions for the remaining 700MHz spectrum that was not sold off in the digital dividend auction. The directions state that the ACMA must report to the government what price it should expect from the spectrum by September 2014, and that the spectrum must be sold for no less than the reserve price.
The drafts are open for public consultation until July 19.