Global support among operators for Long Term Evolution (LTE) is unprecedented, but it will be years before devices are capable of roaming internationally on LTE networks, because of the overwhelming number of frequency bands that they will have to support.

An LTE device that's capable of roaming anywhere in the world will have to support between 13 and 15 frequency bands, according to Nigel Wright, wireless VP at mobile test specialist Spirent Communications plc .

And that's a tall order for a new technology.

The LTE frequency band complexity could force device makers to compromise on the number of bands that are supported in early devices, which would lead to coverage and performance issues in some regions.

They could "perhaps optimize a device to work in North America and accept that it won't work as well in Europe," says Wright. "Those kinds of tradeoffs happen today and will increase by an order of magnitude when we get to LTE."

To roam internationally, LTE devices will have to support not only all the different frequency bands for LTE, but also the bands for legacy technologies CDMA, GSM, and UMTS, which creates an even bigger challenge. "A device has to wake up in any country and decide which is the best band to operate in," Wright says. (See AlcaLu, LG Boast LTE/CDMA Handoff.)

Just to give some idea of the complexity, the three earliest LTE deployments will use three different frequency bands: NTT DoCoMo Inc. (NYSE: DCM) will deploy in the 2.1GHz band; Telia Company uses 2.6GHz; and Verizon Wireless will use the 700MHz band.

For Verizon, an LTE device at a minimum is likely to support LTE at 700MHz and CDMA technologies at 850MHz and 1900MHz, for example.

But more important than getting an LTE device that can be used in multiple countries (and on what networks, by the way?) is perhaps getting any LTE device on the market. TeliaSonera uses an LTE modem from Samsung Corp. for its networks in Stockholm and Oslo. But the latest timeline on LTE device availability from Information Gatekeepers Inc. (IGI) is that modems and USB cards will be available this year; LTE-embedded notebooks, mobile Internet devices, and possibly data-only handsets will follow in 2011; and voice-centric LTE handsets are expected in 2012. (See 'Millions' of LTE Handsets by 2012?, An LTE iPhone? Think 2012 (or Later), and LTE Phones Will Lag Behind Networks .)

"At the moment, everyone is just trying to get LTE to work," says Spirent's Wright.

At the Mobile World Congress in Barcelona this month, LTE device sightings will be a priority for many show goers. NEC Corp. (Tokyo: 6701) will show off a mock-up of an LTE device for NTT DoCoMo. (See LTE Device Mock-Up at MWC.)

— Michelle Donegan, European Editor, Unstrung