NBN has demonstrated downstream bandwidth of 1.1 gigabit per second (Gbps) and 165 megabits per second (Mbps) upstream on its fixed wireless network, but says spectrum constraints make the chances of a commercial service very slim.

The demonstration – carried out in March simultaneous with NBN’s demonstration of and announcement of plans for a commercial 100/40Mbps fixed wireless service in Ballarat – required the aggregation of 11 20MHz carriers to achieve the downstream bandwidth.

For both demonstrations NBN used a spare sector on an NBN fixed wireless tower in Ballarat that had fibre backhaul into NBN’s network infrastructure.

NBN said it had no plans for a commercial 1Gbps service saying it would be “very challenging to contemplate getting 11 carriers across the entire network.”

“That is really in the hands of the [Australian Communications and Media Authority] and the industry,” a spokesperson said. “Those discussions will be had over the next few years with increasing heat.”

He noted that the ACMA has issued a consultation paper on what to do with presently unallocated 3.5GHz and 3.7GHz spectrum, saying, “there are a lot of interested parties.”

He added: “There are other technologies coming down the track such as beamforming antennas that make much better use of the spectrum. We will be looking at how we can use the spectrum assets we have to provide greater capacity more efficiently.”

However NBN CEO, Bill Morrow, in a press release detailing the trial, was more bullish about the prospects for a commercial service, saying: “Our ability to deliver gigabit speeds on fixed wireless demonstrates our continued focus on identifying and implementing tech advancements as and when they are needed, across all technologies.

"It's particularly exciting to be able to reaffirm our commitment to delivering a great experience to the 600,000 premises in regional Australia that will be served by the fixed wireless network.”

The demonstration used four 20MHz carriers in the 2.3GHz band (also known as Band 40) and seven 20MHz carriers in the 3.4GHz band (Band 42) and a modulation technique known as 256QAM to achieve the downstream bandwidth. The 165Mbps upstream bandwidth was achieve by aggregating three carriers and using 64QAM modulation.

However as the commercial Qualcomm chipsets used in the customer premises radio equipment, what NBN calls its network termination device (NTD), are capable of aggregating only four carriers, NBN had to deploy three NTDs and separately aggregate the signals from each of these to achieve the demonstrated throughput.