Shortly after METIS put forth its recommended tools on how to use the above-6GHz bands for 5G, UK regulator Ofcom is identifying which high-frequency bands make the most sense for operators to use for their future 5G networks. (See Anite Puts Forth 5G Radio Channel Models .)

The regulator has released its preferred list of frequencies as a recommendation for 5G in the above-6GHz millimeter wave (mmW) bands, not as a mandate. Other options are expected to arise from the World Radio Communication Conference this fall, and operators will likely end up using a mix of above-6GHz and sub-6GHz bands for their networks -- a sentiment that was shared at Light Reading's "Building America's 5G Ecosystem" event in NYC last week as well. (See You Can't Spell 5G Without LTE.)

For its part, Ofcom says the following bands should be "considered for study under a focused agenda item on 5G mobile broadband for WRC-19": 10.125-10.225/10.475-10.575GHz, 31.8-33.4GHz; 40.5-43.5GHz; 45.5-48.9GHz and 66-71GHz.

For more on 5G, visit the dedicated 5G section here on Light Reading.

What spectrum is best suited for 5G has been a topic for debate, with the South Korean operators pushing for millimeter deployments and others believing the sub-6GHz bands that currently host LTE-Advanced make the most sense for the network evolution. There is a consensus emerging that both bands will end up being in use -- the above-6GHz frequencies for things like small cells and broadband enhancement and the sub-6GHz bands for traditional mobility and mission-critical services. (See 5G: Generation Gap.)

"It's clear that the 5G work will include operation above 6GHz and clear that some channel modeling effort will be required in the RAN," Satoshi Nagata, chairman of the 3rd Generation Partnership Project (3GPP) TSG-RAN WG1 and NTT DoCoMo Inc. (NYSE: DCM), said at Light Reading's event, while conceding that even DoCoMo may work in the sub-6GHz bands for initial deployments.

Executives from Alcatel-Lucent (NYSE: ALU) agreed that 5G will show up first in the low bands for coverage and to relieve congestion on the 4G network. Tod Sizer, VP of wireless research program for Alcatel-Lucent's Bell Labs, said that the below-6GHz bands will be needed to enable new apps that cannot wait for millimeter wave.

"I don't believe the timeline for getting this out is quick," Sizer said. "The requirements for enabling short packet opportunities lend itself [sic] to lower frequency solutions. We see that as solving a critical first problem quickly."

The millimeter wave spectrum bands have been less studied, which is why organizations like Ofcom and METIS, led by Anite plc , are putting out new recommendations on how to operate in them. Neither is drawing a line in the sand but rather aiming to ensure operators and vendors are prepared to explore any and all spectrum options. (See Spectrum Muddle at the 5G Huddle.)

Ofcom says it may further refine its preferred spectrum list as discussions continue on a domestic and international basis in the run-up to the WRC-15 event in November. Its ultimate goal is to identify bands that it believes can get global support to meet interoperability and roaming challenges in 5G.

"We think these bands may be relatively straightforward to make available in the UK compared to other options within the range 6-100GHz (although the 10GHz band is likely to be significantly more challenging than higher frequency bands) and could have potential for being harmonized and developed for future 5G use globally," Ofcom's report says of its selections. "However, this does not guarantee that these bands will be adopted in the future or preclude other bands being added."

— Sarah Thomas, , Editorial Operations Director, Light Reading