One of the biggest challenges to international LTE services is the fragmentation of the spectrum bands used for the networks, and consequent problems for roaming.
Operators and vendors are seeking to mitigate the effects, with Qualcomm developing a chipset which supports no fewer than seven bands. Meanwhile NTT DoCoMo, always an influential carrier on standards developments, believes the best way is to rely heavily on existing frequencies.
Qualcomm's plan was revealed in a filing it made to the US regulator, the FCC, opposing proposals that operators should be mandated to support roaming between LTE services located in different parts of the US 700MHz band plan.
This issue highlights the interoperability and roaming challenges which LTE's host of frequencies create, since there are four band classes within 700MHz. Small operators run their 4G services in Band Class 12 of the spectrum, while AT&T is in Band Class 17 and Verizon mainly in Band Class 13.
Devices for these different sections are not interoperable and the smaller cellcos claim that, if the big names are not forced to roam, their business models will be weakened because they will have limited power to acquire high impact devices, or offer their subscribers national roaming coverage. AT&T retorts that a mandate would increase its device development costs and slow time to market, as well as risking interference to its users' signals.
Qualcomm says the market is moving quickly and it would be premature for the FCC to issue mandates at this stage. It said it has accelerated development of its next generation RF chip, the WTR1605L, which will support a total of seven bands, three below 1GHz, three higher bands, and one very high band (presumably 2.5/2.6GHz). The chip giant, which tends to set the bar for the whole industry in terms of modem frequency support, said it was just starting to transition towards a chipset based on the new RF offering, the MSM8960.
This will be made in the new 28nm process and despite issues with securing sufficient capacity in its foundries, Qualcomm expects the first MSM8960s to ship to OEMs this July, in time for holiday season devices.