A network expert who was associated with the initial stages of the national broadband network rollout has described the working paper issued by the Department of Communications and the Arts on network speeds as "seriously flawed".

Rod Tucker, Laureate Emeritus Professor at the University of Melbourne and a member of Labor's Expert Panel that advised on the NBN, said: "By itself, the figure of 49Mbps rings alarm bells, being just below the 50Mbps maximum bandwidth of the speed range that NBN Co is currently pushing. It looks awfully like a justification of the FttN network."

The paper claimed that the NBN rollout should provide enough bandwidth for Australian households through to 2026, adding that peak bandwidth demand for households with the highest usage was forecast to increase from between 11Mbps to 20Mbps in 2016 to between 20Mbps to 49Mbps in 2026.

Tucker (below, right) said the report appeared to have been written by "people who simply don’t understand the basics of telecommunication concepts such as bit rate and bandwidth".

He cited the following which was on the second page of the paper: "Bandwidth can be compared to the flow of traffic on a road, with the rate at which those cars travel dependent on the capacity of the road (the number of lanes) and the number of cars on the road at any given point in time. The more cars that use the road at the same time the slower will be the flow of traffic. In peak periods, it will take longer for any one vehicle to reach its destination."

To this Tucker responded: "This is an naive and downright misleading analogy. Bandwidth is not analogous to how fast an individual car travels. It is a measure of information flow in bit per second.

"The freeway analogy with bandwidth is the number of cars per second (or minute or hour) that the freeway can handle. The number of cars per minute on a freeway is sometimes higher in heavy traffic conditions than it is in light traffic conditions, regardless of the speed of the cars. The time a car takes to get to its destination is a completely different issue, known as latency."

He said the paper's author or authors had confused usage with demand. "The authors make predictions of usage, based on a number of factors, including current usage, but they fail to acknowledge that current usage is constrained by the available technology. What people want is not necessarily the same as what they get."

And, he added, a key problem was that the paper assumed there would be a 9% annual improvement in video compression technology.

This assumption resulted in three major errors, he claimed.

"The fact that video compression technology has improved in the past does not mean that it will improve in the future. Many experts feel that it will not improve much more in the future; "Video compression does not work will with fast-moving scenery such as sporting events. Sporting events need less compression, not more; and "Video compression involves delay (called latency). You can see this every night on the TV news when the interviewer asks a question and the interviewee stands there nodding their head for a few seconds before they reply. This latency is not acceptable in virtual reality and interactive video."

Tucker said if the errors he had pointed out were corrected, the predicted demand in 2026 would not be 49Mbps. "It is more like 150Mbps or 200Mbps. My conclusion is that the NBN needs to be upgraded from FttN to FttC or FttP."

The Australian Greens have also been critical of the working paper.