Copper network dulls DSL performance

Almost one quarter of Telecom customers don't get the speed they pay for

The legacy copper network is being fingered by Telecom as the culprit behind almost a quarter of broadband customers not getting the speeds expected.

A network monitoring system announced by Telecom's general manager of technology investments Stephen Crombie this year and implemented by Alcatel, shows that 87,000 customers could not get the higher speeds of the new plans introduced recently.

Some five percent or just over 16,000 of all customers actually experienced a reduction in speed before they were upgraded to the 2Mbit/s and 3.5Mbit/s download plans, according to the Alcatel report.

The report says that unconstrained line rates will hit service quality hard. An estimated 170,000 customers will not get the 2Mbit/s and 3.5Mbit/s download speeds.

Ominously for Telecom's business customers, high-cost services such as OneOffice and Frame Relay look likely to suffer once the load on the copper network increases. These services are delivered over the same copper as residential ADSL, together with 2Mbit/s Synchronous Digital Hierarchy E-carrier system 1 links. The Alcatel report say the signal modulation techniques for these are "unfriendly" and cause connection instability for other network users.

Warming up its wholesale partners and the regulator to its suggested spectrum management plan, Telecom points out that the existing copper network was only designed to transport frequencies up to 4KHz, or the top-end of the voice range. DSL however, utilises frequencies in the 1MHz range and 2.2MHz for the second generation of the service.

To get the promised 8Mbit/s performance of ADSL1 and 24Mbit/s of ADSL2+, customers need to have very short lines — less than one kilometre. Ideally, the copper in the lines should also be of heavier gauge, and the area should have few DSL and other broadband customers. Good modems are key too, but Telecom's current standards are deemed inadequate for evaluating how well they interact with the network. A new testing regime is suggested for DSL modems.

The Alcatel report also stresses that the cables in question should be in "an excellent state of repair" for best performance. Telecom has been accused of scrimping with the maintenance of its copper network, and having a policy of inserting joints rather than new lengths of cable despite the degradation of electrical characteristics this brings.

Telecom says that a corollary of introducing unconstrained DSL on its copper network is that the rollout of ADSL2+ will be delayed until March next year. CEO Theresa Gattung originally promised that ADSL2+ would be deployed from June this year, but now Telecom will instead focus on unconstrained first generation DSL.

Although ADSL2+ is capable of 24Mbit/s, Telecom estimates only four percent of customers would hit that download speed. Just over half would get between 10Mbit/s to 20Mbit/s. Telecom's estimates are that three-quarters would get more than 6Mbit/s and two-thirds over 8Mbit/s, but it stresses that it doesn't yet know for sure as extensive tests are needed to verify the performance.

Customers who find themselves unable to reach the performance of their chose plan, will be offered lower-speed ones instead to match their maximum achievable line rates.

Conservative figures from Alcatel, the network manager for Telecom, show how far the incumbent is from meeting customer expectations on broadband speed. By the end of this year, Alcatel says the figure is 10Mbit/s for so-called power users, and 1Mbit/s for novices. Telecom currently has no way of reaching these modest targets, already exceeded in many OECD countries.

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