NBN Co says about two percent of all premises - up to 238,000 - are still incapable of minimum 25Mbps peak download speeds, though it claims “the vast majority” of those see speeds over 20Mbps.
The whole-of-footprint number is made calculable by figures in a lengthy report [pdf] from NBN Co to the government in support of the network being declared “built and fully operational”, a stepping stone to the eventual sale of the company.
The government made the declaration on the basis that the NBN “is supporting 50Mbps to more than 90 percent of the fixed line footprint and 25Mbps to approximately 98 percent of all premises, with ongoing proactive and reactive programs in place to resolve the remaining lines.”
With approximately 98 percent of all premises able to hit the 25Mbps minimum peak speeds mandated in the 2016 statement of expectations, that leaves two percent or less that can’t.
Based on a total footprint of 11.9 million premises, the number of impacted premises is up to 238,000.
This number has only been sporadically released throughout the build, and often only partially; the most recent release was for the fibre-to-the-node (FTTN) footprint only, though this is where the issue is most prevalent.
Under the statement of expectations, “the government expects the network will provide peak wholesale download data rates (and proportionate upload rates) of at least 25 megabits per second to all premises, and at least 50 megabits per second to 90 percent of fixed line premises as soon as possible.”
Importantly, NBN Co’s report notes that it is likely to face ongoing problems with copper lines falling below the 25Mbps minimum, meaning the number of premises missing the minimum speed may remain reasonably constant for an extended period of time.
“Due to the ongoing impacts to network performance due to environmental and operational factors there are services that previously achieved 25Mbps which fall below that threshold,” NBN Co said.
“Ongoing proactive and reactive programs to address these issues ... subsequently restore services above 25 Mbps.
“The effect of services moving into then out of the group of services below 25Mbps causes the volume of lines that do not meet 25Mbps to remain consistent; however, the composition of the lines that make up that volume is continuously changing.”
NBN Co said that “this is normal practice for network operation globally” and said its performance on remediating problem lines is “in-line with, or better than, other global copper network operators.”
The company also said that services that dipped below the 25Mbps mark often did not underperform by a great deal.
“It is important to note that the vast majority of premises that can not currently obtain 25Mbps, can access more than 20Mbps,” it said.
Specifically on the copper-based part of the network, NBN Co said it had sought to meet the statement of expectations “by engineering design standards that set a maximum electrical signal loss budget and subsequent length of the copper wires between the equipment in the FTTN street cabinet (node) and the customer premises.”
“The overall signal-loss is affected by the length of the entire copper path, as well as the quality or the presence of impairments and interference,” it said.
“This loss budget figure also assumes that the entire copper path, including the copper path within the customer premises, is of good quality and is impairment free.
“For most typical line copper conditions with standard gauge cable this loss budget translates to a node to modem copper loop length of ~1100 metres.”
The company produced a graph that shows how the attainable download speed degrades up to 1100 metres.
Connections beyond 1100 metres are designated to be “long copper lines” and are subject to a specific “serviceability” program of work, which NBN Co said is “on track to be completed in FY21.”
NBN Co had relied on Telstra’s records to identify lines subject to this program of work.
It also has a pair of copper “rehabilitation” programs that seek to address the broader issue of services falling under the 25Mbps minimum.
Services that move above and below the 25Mbps minimum are typically from the FTTN/B and fixed wireless footprints, NBN Co said.
The company has separate remediation and upgrade programs for the wireless footprint.