Mobile Migraine: Carrier Aggregation RoamingMobile Migraine: Carrier Aggregation Roaming

With LTE deployments growing across the globe, the wireless operators are currently working through the headache of achieving LTE roaming, but that might pale in comparison to the migraine that roaming with carrier aggregation in LTE-Advanced networks will induce.

Peter Carson, senior director of marketing for Qualcomm Inc. (Nasdaq: QCOM)'s Gobi team, says the challenge is still a few years out, but it's one that's starting to become real as more operators begin implementing carrier aggregation (CA), a feature of the 3rd Generation Partnership Project (3GPP) 's Release 10 specs of LTE-Advanced that bonds two or more spectrum bands together to increase network capacity and speed. To do this, requires up-to-date technology on both the radio network and handset side.

While CA is just one of many features that makes up LTE-Advanced, it's the one that most operators are pursuing first, and Carson believes it will be the focus for the next few years. SK Telecom (Nasdaq: SKM) went live with CA in June; Telstra Corp. Ltd. (ASX: TLS; NZK: TLS) is trialing it; and AT&T Inc. (NYSE: T), Sprint Corp. (NYSE: S), and T-Mobile US Inc. have all promised deployments this year. (See SK Telecom Adds 300K LTE-Advanced Subs, T-Mobile to Debut LTE-A 'Features' in 2013, Sprint Plans LTE-Advanced Launch in 2013, and Carriers Are a Mixed Bag on LTE-Advanced.)

Qualcomm is powering SK Telecom's first two LTE-A handsets, the Samsung Corp. Galaxy S4 and LG Electronics Inc. (London: LGLD; Korea: 6657.KS) G2, as well as the Netgear Inc. (Nasdaq: NTGR) dongle used in Telstra's trials, with its Snapdragon 800 processor that supports CA. Carson says there are 30 spectrum band combinations being pursued by less than 30 operators globally, a number that will grow to more than 45 combinations and potentially to 60 when combos yet unknown emerge.

"It's complex from radio design perspective," he says. "It will keep the chip community busy for awhile."

Supporting all of these bands in a single phone design is the big challenge at the handset level. For the wireless operators it's working out the business deals to support roaming on all these band combos. CA doesn't change the nature of LTE roaming, but moving between different carriers' bonded bands does involve more handoff, frequency support issues, and complexity, in general. Operators may have to agree on one band of LTE to roam on, at least for the next few years.

Qualcomm claims to have solved the single-SKU problem for LTE with its RF 360 chipset, and Verizon has promised LTE-only smartphones in late 2014, but Carson says carrier aggregation roaming will probably be enabled in a future generation product. It will mainly be a carrier discussion, he adds, but the device makers that get out early will have influence as they sort through RF, performance, and efficiency issues, and the wireless operators hash out roaming agreements. (See Verizon Envisions Cheaper VoLTE Subsidies.)

"It's a multi-year process to have global carrier aggregation roaming capability," Carson says. "We've solved the tech problem, but the industry hasn't solved this single SKU roaming problem... Once they agree on the plans, you'll see spectrum acquisition and licensing of new spectrum follow roaming agreements."

— Sarah Reedy, Senior Editor, Light Reading