NBN Co has 'under 500' congested fixed wireless cells

NBN Co has confirmed the number of fixed wireless cells that it classifies as congested is somewhere “less than 500” nationwide.

The network builder last month said that “around six percent of fixed wireless cells” are congested enough in the evening peak to cause average speeds to fall under 6Mbps per user.

With “about 7000 cells in the network”, the number of those impacted by congestion is somewhere less than 500, chief network engineering officer Peter Ryan told a senate estimates committee last week.

Based on an updated percentage range given by NBN Co at the hearing of “about 6-7 percent” of cells being impacted, the number of cells experiencing issues would be between 420 and 490.

“We’re working very hard to pull that number below one percent,” Ryan said.

Fixed wireless congestion is firmly on the radar after the company explained its two thresholds for flagging problems in the network back in February.

The company said it generally aims to trigger upgrades to sites so they do not drop below 6Mbps per user at peak times.

The 6Mbps level is judged by measuring the average throughput of all end-users in a cell in the busiest hour averaged over a month.

However, due to long lead times involved in deploying upgrades, a small number of sites see per-user performance degrade to 3Mbps or below, and those are then classed as unacceptably congested and given further attention.

There are currently between 20 and 30 cells that have hit this unacceptable congestion level.

“Typically the reason why these sites take longer to deploy the capacity is because we need to undertake significant structural upgrades to the towers,” Ryan said last week.

“If we don’t own the towers, we [have to] go through the owner of the tower to design it for upgrade and then do it.

“The complexity also comes in if you have live services on an existing tower on which you’re then doing significant structural upgrades. It just becomes quite a tricky piece of work to undertake.”

Ryan said that adding cells to a congested tower was a common way of alleviating performance issues.

However, the company could also increase the capacity of microwave backhaul into the site or put “additional electronics inside the cabinet at the tower”.

“There are a range of things that enable the additional capacity,” Ryan said.

Ryan said that users in congested cells typically saw performance impacts on their services of “about 2.5 hours per day”.

The fixed wireless performance issues have caught the eye of regulators, particularly around how many customers see only a percentage of the topline speeds they pay for.

NBN Co CEO Bill Morrow said last week that - technically - the service remained within the statement of expectations - though he indicated NBN Co would not use that to avoid necessary upgrades.

“The SOE refers to the minimum peak speed of 25Mbps so the majority of the time during the day if you bought a 25Mbps plan you would be able to achieve the minimum peak speed,” Morrow said.

“[But] I think there’s a degree of reasonableness [needed] on this, hence the reason we’ve decided to spend the extra money to account for the growth and the changes we’ve seen in consumer behaviour [by upgrading towers].”

Morrow also confirmed that while upgrades were being pursued, NBN Co had “suspended” examining higher-speed fixed wireless options that would take the network beyond 100Mbps.

The reason behind this is likely to be much the same as why most RSPs have stopped offering 50Mbps plans on the fixed wireless network.

“We want to be absolutely sure that we provide a minimum base experience that’s acceptable to end users in the busy hours [first],” Morrow said.