Nokia Siemens wants to shut off 2G one frequency at a time

Usually wireless equipment makers like to talk about networks they’re building, but at CTIA Wireless in New Orleans this week Nokia Siemens Networks(s nok)(s si) is talking about shutting them down. NSN is showing off a technology at the show that will help operators repurpose their old 2G spectrum for mobile broadband by allowing them to gradually shut off small increments of their GSM networks and add that capacity to HSPA.

Clearing, or refarming, spectrum for HSPA is no easy task because operators need a lot of unencumbered frequencies to launch the most bare-bones network  — 5 MHz on the downlink and 5 MHz on the uplink. Meanwhile GSM networks use tiny 200 kHz channels. That means an operator would normally have to shut down a whole bunch of GSM before they can turn up a new HSPA network.

The German-Finnish equipment maker is solving that problem by creating smaller HSPA channels — as small as 3.8 MHz — and it’s making those channels flexible so that operators can add capacity to the network in 200 kHz increments. The end result is that an operator can start out small, shutting down a portion of its 2G capacity in order to deploy more an initial modest HSPA system. And as customers gravitate from 2G to more efficient 3G voice, it can gradually shift that capacity from GSM to HSPA.

This kind of configurable bandwidth technology is widely supported in LTE, which uses frequency swaths as small as 1.4 MHz and as large as 20 MHz, but it hasn’t been an option on HSPA. Instead vendors have been trying to find ways to make HSPA transmissions bigger, not smaller, as in the dual-carrier technology used by T-Mobile USA and other global operators.

T-Mobile is probably exactly the company NSN is trying to court by unveiling the enhancement to its Liquid Radio base stations at CTIA, North America’s biggest wireless industry trade show. T-Mobile plans to sunset big portions of GSM network in order to make room for more HSPA+ and its eventual LTE network. NSN is one of T-Mobile’s primary network vendors, along with Ericsson(s eric), so it’s probably no coincidence that this configurable bandwidth upgrade will be available in the second half of 2012, right when T-Mobile will begin turning on its HSPA networks in the PCS band (and hopefully get the iPhone(s aapl) in the process).

NSN is also coupling the configurable bandwidth software with new GSM enhancements that can double the voice capacity over a 2G network, which would in turn clear more spectrum for HSPA. But T-Mobile and other developed-world carriers are probably less interested in such super-GSM technology. Rather than invest money in making 2G more powerful, they would rather just ride out their usefulness and spend the money for mobile broadband.

This post was updated Monday evening to clarify a point on HSPA channels. The configurable bandwidth technology doesn’t create smaller HSPA+ carriers. Rather, they allow an operator to incrementally increase the size of a single normal sized HSPA+ carrier, allowing it to grow beyond the confines of its guard band.

Image courtesy of Flickr user fsse8info