DENVER -- Big 5G Event -- Heavy US reliance on millimeter wave spectrum could make the 5G coverage map look as spotty as a pimple-faced teen unless authorities can free up some of the mid-band airwaves that are spurring 5G deployments elsewhere.

Leading analysts have in recent weeks raised serious doubts about the 5G services now sold by Verizon, whose strategy is based almost entirely on the use of millimeter wave spectrum. Now, senior industry executives gathered at Light Reading's Big 5G Event here in Denver have suggested the lack of mid-band spectrum could hobble the US in the 5G race against China and other leading 5G nations.

But just what is millimeter wave spectrum, and why is there so much concern about it now?

The expression typically refers to any spectrum in very high frequency bands, usually at or above 26GHz (strictly speaking, millimeter wave means even higher bands). Because so much spectrum is available in these frequency ranges, they can support extremely fast mobile connections. Verizon touts speeds of up to 10 gigabits a second, many times faster than any 4G network can manage today.

The unfortunate trade-off is the poor coverage that millimeter wave delivers. If there were a superhero called 5G Man, he would be a lightning-fast weakling with millimeter wave spectrum, incapable of punching through the flimsiest of barriers. Walls, vehicles, foliage -- even an individual's hands -- can all block the millimeter wave signal.

Operators like Verizon are trying to overcome this problem though beamforming, a clever technique that steers the mobile signal toward a device. When millimeter wave spectrum is being used to support residential broadband services, some operators are also using a mixture of internal and external customer premises equipment to punch through those walls.

Yet some analysts remain unconvinced (as this Light Reading article attests), and Verizon does not seem for turning. "Spectrum for 5G is millimeter wave," said Nicki Palmer, Verizon's senior vice president of technology and product development. "We can talk about mid-band, and over time all spectrum becomes 5G, but for us the generational change of 5G is enabled by massive bandwidth and you don't get the speed and throughput without it."

You're invited to attend Light Reading's Big 5G Event! Formerly the Big Communications Event and 5G North America, Big 5G is where telecom's brightest minds deliver the critical insight needed to piece together the 5G puzzle. We'll see you May 6-8 in Denver -- communications service providers get in free!

It's not just the analysts who are now complaining, though. Chris Pearson, the president of the 5G Americas lobby group, urged the US to release mid-band spectrum to support 5G services during a keynote presentation Tuesday morning at Light Reading's Denver event. Without it, he said, the US 5G lead could be at risk.

"We need more licensed spectrum across all bands. We are the leader in millimeter wave but we need to continue to make progress on mid-band. Much of the world will deploy that and specifically target the mid-band for coverage and capacity," he told conference attendees.

Unfortunately, a lot of the mid-band spectrum in the US is currently hogged by other organizations, such as satellite companies, although the Federal Communications Commission, which regulates the telecom sector, is considering several mid-band spectrum proceedings, including a 3.5GHz auction in 2020.

But time, as they say, is of the essence. "We are at a critical juncture. There is a race to 5G and -- just like in a basketball game -- who is ahead at first might not determine who will win," said Pearson.

His remarks were echoed on a panel session later that day by Tom Sanwanobori, the senior vice president and chief technology officer for the CTIA, another US lobby group. "Where we are challenged is in mid-band spectrum," he said. "We need that to expand coverage and capacity."

Perhaps the most scathing assessment of the US 5G position came from an operator, albeit not one of the industry giants. Tom Simpson, the chief operating officer of Cincinnati Bell, is not overly impressed by what is happening today. "I see very fractured deployments. Mid-band is an issue. I wouldn't score it an 'A' just yet," he said when asked how he would rate the country's 5G performance so far.

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— Iain Morris, International Editor, Light Reading