T-Mobile US expanded its nationwide 5G standalone (SA) core to run on its extensive and deep 2.5 GHz spectrum holdings, providing the carrier with the ability to aggregate 5G SA spectrum to better support dynamic use cases like network slicing and private wireless.

The move boosts T-Mobile US’ 5G SA core with access to mid-band spectrum the carrier acquired when it purchased Sprint. That 2.5 GHz spectrum has been central to T-Mobile US’ “Ultra Capacity” 5G service that offers higher speeds than its regular 5G service.

T-Mobile US has access to more than 150 megahertz of 2.5 GHz spectrum across the country. It recently boosted long-term access to that capacity through a $3.5 billion deal with spectrum license holders Channel 51 License Co and LB License Co.

“The more that we can have this traffic living on a pure 5G lane with all of the spectral efficiency and capability that we can bring, the more that we can continue to grow and drive the experience to be much improved, be that from a capacity, speed perspective, 5G SA and mid-band is going to have material differences in terms of latency,” Neville Ray, president of technology at T-Mobile US, said this week during the NSR & BCG Innovation Conference.

T-Mobile US initially launched its 5G SA core in mid-2020. That network had been exclusive to the carrier’s 600 MHz spectrum, which allowed for its broad, nationwide coverage.

“We coupled those two things together to really extend and differentiate our coverage and performance, extending the reach of 2.5, using that 600 megahertz layer. We've been doing that for some time,” Ray added.

Ray did note that this initial 2.5 GHz support would be limited to data services and not include the carrier’s recently launched voice over new radio (VoNR) service, though he added that “we can come back to VoNR maybe later.”

T-Mobile US’ VoNR service is currently available in just a handful of markets. It allows devices to remain connected to the carrier’s 5G network for both voice and data sessions. The carrier said the service might provide for faster call set-up times, but the real benefit will be in now being able to include voice services as part of its network slicing abilities.

Ray said the carrier was looking to expand the reach of its VoNR service running on its 5G SA core nationwide early next year.

“Then, not just will data live in a pure 5G lane but so will voice and so your mobile phone never has to move between the respective layers, it can stay on the 5G experience,” Ray added.

A 5G SA core, which consists of the user plane, control plane, and shared data layer network functions, allows operators to deliver a more resilient core network and support highly-touted 5G services like network slicing, automation, orchestration, and mobile edge computing.

A recent report from LightCounting Market Research noted that ongoing “headwinds” have limited the deployment of 5G SA networks to just 20 at the end of last year. This was just 10% of the 200 5G non-standalone (NSA) commercial networks deployed worldwide.

The research firm explained those headwinds are led by “the lack of 5G business cases beyond enhanced mobile broadband combined with some network architecture issues” that continue “to inhibit 5GC SBA [5G core service-based architecture] rollouts.”