Root causes of XT failure identified

Open access cellphone infrastructure mooted

Telecom and its infrastructure provider Alcatel-Lucent have got to the bottom of the causes of the four major problems in the early days of the XT network, members of TUANZ were assured at a meeting last Tuesday.

However, no absolute guarantee of failsafe operation could be given, the companies say.

LV Martin's slogan “it’s the putting it right that counts” was quoted several times during the meeting. TUANZ CEO Ernie Newman is positive about Telecom’s efforts, but several members clearly believe, in the words of one contributor from the floor, that “what really counts is not getting it wrong in the first place”.

Before and after the formal session the possibility of New Zealand’s three mobile phone companies sharing infrastructure, particularly backhaul and even cellphone transmission towers, was canvassed. It seems wasteful and a target for public protest to have three towers in close proximity when one will do, says TUANZ chairman Chris O’Connell. With less complexity, he suggests, resilience may well improve.

The XT breakdowns had no common underlying cause, say spokespeople for Telecom’s software arm Gen-i and Alcatel-Lucent; they were a sequence of hardware and software failures and a switch misconfiguration due to human error.

The most southern of the XT network’s two original radio network controllers (RNCs) was implicated in at least two of the failures. Measures against a recurrence of the problem include the addition of two more RNCs, already in operation, with a further two planned by mid-year, says Gen-i’s national mobile manager Joe Caccioppoli.

A map of the coverage area of each RNC shows significant overlap covering Auckland, Wellington and Christchurch. People in those centres should at least now have improved redundancy.

All the “rehoming” (the migration of phones) to the South Island RNC has been completed, he says. A total of 400 new tower-mounted amplifiers (TMAs) are being added to the network to improve signal strength and therefore coverage, as well as 50 new cell sites. Also, 2100 MHz transponders will be added to the current 850 MHz equipment in high-population areas.

When they have been installed “we are confident that XT coverage will match CDMA’s,” says Caccioppoli.

Alcatel-Lucent NZ chief technology officer Martin Sharrock emphasises that at no time was there an overload of traffic in the main speech and data channel of the network; it was the signalling channel where the flooding occurred. This carries network administration traffic as well as SMS messages.

Failures such as the collapse of a backhaul router on January 27th (the third of the four incidents) caused cellsites to lose connectivity and “spams” the RNC with signals attempting to reconnect. Alcatel-Lucent and Telecom are now “really focussed on looking at traffic volumes and profiles and making sure we’re not surprised,” Sharrock says.

Despite favourable comments on Telecom’s speed of reaction from senior TUANZ people and on remedial measures and communication around the failures, there were still views from the audience that more could have been done by way of advance testing and that Telecom had perhaps chosen the wrong supplier in Alcatel-Lucent, rather than Ericsson.

Sharrock says testing would not have eliminated human failings.

Caccioppoli pointed out that Alcatel has done sterling work in New Zealand’s fixed and mobile networks for 10 years. He says entrusting the company with XT’s smooth future interoperability in a world where the boundary between fixed and mobile networks is fast becoming invisible. Ericsson, he believes, had done no significant mobile work here.

Sharrock looked to seal the argument by playing an unexpected patriotism card: “If you want your network built by Aussies, choose Ericsson,” he said. “If you want your network built by Kiwis, choose Alcatel-Lucent.”