BARCELONA, Spain – Wireless technology innovators have their sights set on 5G-Advanced and 6G technologies, however interviews and panel discussions at the MWC Barcelona 2023 event showcased that the advanced services promised by those network upgrades are going to be challenged by real-world spectrum constraints.

Separate panel discussions at the event looked at what the industry could expect from upcoming 3GPP Releases, specifically with Release 18 (5G-Advanced) and 19 (6G). Both releases are expected to increase the data carrying capacity of a given amount of spectrum and allow operators to launch more data-intensive services.

Ari Kynäslahti, VP and CTO for strategy and technology at Nokia’s Mobile Networks division, explained during a 6G spectrum panel discussions that 6G technology should provide at least a five-times improvement in spectral efficiency compared to 5G. That is significant as it will allow operators to support more data-intensive use cases from their constrained spectrum resources.

The biggest capacity advantage for 6G should be in its ability to support broader spectrum bands into a single channel. This will allow operators to stitch together their increasingly diverse spectrum holdings to provide more capacity and speed to end-users.

The need for more spectrum, regardless of where it’s located on the spectrum chart, was mentioned by many at the event. “We definitely pound the table for more spectrum,” Chris Pearson, president of industry trade group 5G Americas, emphatically said during an interview.

Operators have tended to use the “layer-cake” analogy when describing their spectrum needs. This typically involves low-band spectrum below 1 GHz that provides significant propagation characteristics for coverage; a mid-band of spectrum between 1.5 GHz and 15 GHz that is a mix of capacity and modest coverage; and then high-band, millimeter-wave (mmWave) spectrum above 20 GHz that typically has a lot of capacity but struggles with coverage.

The challenge for 6G is that there is little new low-band spectrum that can be directed toward the mobile communications space. Some of those bands have already been allocated to mobile operators and will need to be re-farmed to support 6G, though there could be opportunities to free up resources that are currently held by television broadcasters.

There is a “need to look at low band,” Luciana Camargos, head of spectrum for industry trade group GSMA, explained during a 6G spectrum panel discussion. “That’s a really complicated conversation with the broadcasters but it is something that is always challenging that needs to be looked at.”

The Federal Communications Commission (FCC) went that route to free up spectrum in the 600 MHz band as part of a complex reverse-bidding process.

There is more of a focus on mid-band spectrum. Specifically, vendors cited spectrum in the 7 GHz to 15 GHz bands as being ripe for possible global federation to support 6G services. Nokia’s Kynäslahti labeled this spectrum as a “golden band,” and explained that setting aside a consistent band worldwide would allow for considerable economies of scale toward deployments.

“I think some of these other bands … there's clearly spectrum opportunity, and I think the industry is going to have to figure out how to make better use of some of those assets,” Neville Ray, president of technology at T-Mobile US and chairman of the 5G Americas Board of Governors, said of this mid-band opportunity.

MmWave spectrum is a higher risk-reward option as there is significant capacity available above 20 GHz, but deployments so far have proven challenging. Operators have spent billions of dollars on various mmWave spectrum bands but have so far only deployed those assets in limited locations.

“Millimeter wave has arguably gone down as one of the greatest failures in the wireless world in recent memory,” Dan Hays, partner at PwC, said in an interview. “There was a lot of wishful thinking. And to be fair, there have been advances in radio technology and massive [multiple-input/multiple-output] that cures a lot of things. But it only goes so far with the laws of physics.”

Those laws could prove even more challenging for the often-discussed sub-THz spectrum bands. These are largely untapped bands above 100 GHz that have very limited propagation characteristics that could play into better re-use opportunities for services like sensing.

This sensing capability was part of an announcement prior to the MWC event from Japanese telecom giant NTT, its mobile arm DoCoMo, and Nokia. The trio integrated artificial intelligence (AI), machine learning (ML), and sub-terahertz spectrum to power potential 6G services.

They explained one of those services was integrating AI and ML into the radio air interface, which they stated “effectively giving 6G radios the ability to learn.” Technically, the move allows the 6G radio to work through signal degradation issues, which reduced signaling overhead and supported a 30% improvement in signal throughput.

The companies also linked the integration to network slicing use cases, stating the 6G radios would gain “the flexibility to adapt to the type of connection demanded by an application, device, or user.”

“For instance, a network in a factory can be optimized for industrial sensors at one moment and then reconfigured for robotic systems or video surveillance,” the firms noted in a statement. “In the public network, an AI-enhanced network can provide an optimized connection for a pedestrian in an [extended reality] session as well as an emergency vehicle traveling at high speed.”

These use cases stir the mind, but analysts sense a growing disconnect between opportunities and the real world when it comes to 5G-Advanced and 6G.

“Not surprisingly, disconnects between vision and reality are common when new technologies are introduced,” Dell’Oro Group VP Stefan Pongratz wrote in a post-MWC blog. “Even if this is expected, we are sensing more frustration across the board this time around, in part because [radio access network] growth is slowing and 5G still has mostly only delivered on one out of the three usage scenarios outlined in the original 5G use case triangle. … Taking into consideration the vastly different technology lifecycles for humans and machines, there are more questions now about this logic of assuming they are the same and will move in tandem. If it is indeed preferred to under-promise and over-deliver, there might be some room to calibrate the expectations with 5G-Advanced/5.5G and 6G.”