Telecom's CDMA network will take months to decommission

Customers switched off at midnight, but then the real work begins

Telecom will shutdown the CDMA core network at midnight, but it will be months before the mobile network is entirely decommissioned.

Senior product manager Gordon Hay, who is in charge of the CDMA shutdown, says the network will be closed at its core, preventing any remaining customers from calling, texting or using the data capability. Instead they will receive a message explaining the network is closed.

“There seems to be a common feeling that it’s just like turning on the Christmas lights. That Chris Quin [acting Telecom CEO] will stand there with a great big switch and turn it off and suddenly the CDMA network dissolves. It’s a lot more complicated then that,” Hay says.

“What we’re trying to do is de-risk the activities, so we’re closing the service to customers, but the reality is they will still be able to see coverage bars on their phones.”

The next step is to turn off the radio transmitters on each of the 900 cell sites around New Zealand that carry CDMA equipment, this is done remotely. Following that every cell site will be visited and the equipment powered down, and the backhaul (for most CDMA sites that’s a 2Mbps copper backhaul link) removed. In addition, the operating and provisioning systems and the alarms and support systems will be decommissioned. Hay says a decision on what to do with the redundant CDMA equipment has yet to be made.

While CDMA and the UMTS (or W-CDMA) network branded as the XT Network share some infrastructure (notably cell sites) they are architected differently.

Hay describes CDMA as a PSTN-type technology but says it is more centralised, with three Mobile Switching Centres located in Auckland, Wellington and Christchurch. The XT Network is served by 10 Radio Network Controllers which are located closer to the cell sites.

Hay says CDMA – which stands for Code Division Multiple Access – was a good technology that provided good spectrum-efficiencies in the 850MHz band when it launched in 2001. Telecom’s rival Vodafone built a GSM network which suited the 900MHz spectrum it was operating in.

However, over time the ecosystem – the devices and international roaming opportunities – diminished for CDMA and Telecom was forced to spend more than $500 million on a new UMTS network, which it branded XT and launched in 2009. Hays describes UMTS as the next evolution of technology on from GSM, which enables a roadmap to LTE (sometimes described as 4G services).

“I always make the parallel with video recorders and the whole Beta and VHS debate. VHS, from what I understand, isn’t such a good technology but it won the race and GSM has won the race.”

There are still CDMA networks in the US and Asia, Hay says.

The CDMA network replaced the TDMA (Time Division Mobile Access) network, whose customer’s had an 025 number, and was switched off in 2007.

See also So long CDMA and thanks for the memories

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