Exactly how much the level of fixed wireless congestion has been under-reported was still being investigated, NBN Co CEO Stephen Rue told a senate estimates hearing on Tuesday.
“That’s being determined,” Rue said.
To date, NBN Co has said the proportion of congested cells on its network peaked at between six and seven percent; it aims to reduce that to under one percent by September this year.
NBN Co considers a cell to be officially congested when its “30 day … average busy hour download throughput [falls] below ... 6Mbps" per user.
The first clue that these numbers did not capture all congestion occurring on the fixed wireless network came on NBN Co’s latest monthly progress report.
“The calculation of busy hour cell performance accounts for throughput at the radio interface, which is one segment of the fixed wireless access network, and does not account for impacts on throughput in other parts of the NBN fixed wireless network,” according to the note.
Labor Senator Anne Urquhart latched onto the note and extracted confirmation from NBN Co that the congestion figures reported to date are likely to be understated.
“In effect, congestion on the fixed wireless network can occur in several places,” Rue said.
“It can occur, as we’ve been reporting, on the cells. It can also occur in the transmission network … and in the transit network.
Chief network engineering officer Peter Ryan said NBN Co measured packet loss at various points in the end-to-end fixed wireless network.
“We watch that and as it triggers through certain thresholds we trigger work to deploy more capacity to uplift the performance to make sure we don’t get that congestion,” he said.
Ryan said that congestion on the microwave or fibre backhaul transmission links would be noticed as slow speeds by end users.
“It impacts the customer at an application level, therefore the impact of congestion is very much dependent on the application the end user is using,” Ryan said.
“User applications that are in need of very low latency like gaming or very high data throughput would be impacted by packet drops, which they would see as a slowing down of their speed.
“We’re working extremely hard at the moment to accelerate the activity to alleviate that congestion by deploying more capacity,” he said.
The company had successfully added capacity to around 13 links as of today.
Of the outstanding congested links, NBN Co said there are 66 in NSW, 65 in Victoria, 58 in Queensland, 20 in South Australia, 16 in Tasmania and 13 in Western Australia.
Ryan said that engineering and deployment resources were being tipped into the upgrades as a matter of priority.
He said the upgrades could take a number of different forms.
“A lot of them are being fixed by some remote configuration changes we can make, which changes the modulation used across that microwave link,” Ryan said.