T-Mobile US claimed a new 5G standalone (SA) “first-ever” achievement that deftly countered a similarly sounding claim made two weeks ago by rival AT&T.

T-Mobile US stated it had managed to aggregate two different spectrum bands in support of an uplink speed in excess of 200 Mb/s running across its “live commercial” 5G SA network. That last part is what differentiated the first from what AT&T claimed.

A T-Mobile US spokesperson explained to SDxCentral that the test merged 20 megahertz of spectrum in the 1.9 GHz band and 100 megahertz in the 2.5 GHz band to produce an uplink speed of 207 Mb/s. The work was done with network partners Nokia and Qualcomm, with the carrier stating customers with compatible devices would be able to take advantage of the uplink enhancement beginning early next year.

The carrier has been layering in its 1.9 GHz spectrum resources that had been powering its 3G networks. Parts of that spectrum are still being used to power T-Mobile US’ 2G network that connects older IoT devices and its still running 4G LTE network.

T-Mobile US’ deep 2.5 GHz spectrum holdings are core to the speed and capacity of the carrier’s 5G network build. It boosted long-term access to that capacity last year through a $3.5 billion deal with spectrum license holders Channel 51 License Co and LB License Co, and late last year expanded its nationwide 5G SA core to run on that spectrum, providing the carrier with the ability to aggregate 5G SA spectrum to better support dynamic use cases like network slicing and private wireless.

T-Mobile US last month pleaded with the Federal Communications Commission (FCC) for access to more of that spectrum that the carrier spent $300 million to acquire during a recent spectrum auction. The FCC lost the ability to release access to those licenses on March 1, when Congress failed to extend that government entity’s authority to use the auction process to grant license rights.

AT&T last month said it managed an industry first when it completed an uplink data call running on its 5G SA network core that aggregated two different spectrum frequency bands. AT&T’s test used a combination of its low-band 850 MHz spectrum and mid-band 3.45 GHz C-band spectrum holdings, which generated uplink speeds up to 120 Mb/s.

“Think of this as adding more lanes in the network traffic highway,” Jason Sikes, AVP for device architecture at AT&T, explained in a blog post. “No one in the U.S market has successfully aggregated two carriers in 5G SA uplink – until now.”

AT&T’s test was conducted in its labs using Nokia’s 5G AirScale equipment running on MediaTek’s mobile test platform.

That “labs” part is the differentiation between the two tests as T-Mobile US touted its test as running on its commercial network.

T-Mobile US has been running a nationwide 5G SA network for several years, while AT&T has been more cautious in its 5G SA roll out. AT&T late last year said it had begun supporting commercial customers on its 5G SA network core, which aligned with more high-profile moves by its competitors.

AT&T did note it's planning to launch 5G New Radio Dual Connectivity (NR-DC) capabilities “in the coming months," which will allow for the aggregation of low- and mid-band spectrum with AT&T’s millimeter-wave (mmWave) spectrum using the 5G SA core.

“This technology gives customers high-speed mobile broadband for both downlink and uplink in stadiums, airports and other high-density venues,” Sikes wrote in his blog post, adding in an email to SDxCentral that “over time, private 5G and fixed wireless will benefit from these uplink and downlink enhancements.”

Regardless of the "first" claims, both T-Mobile US and AT&T noted increased uplink speeds allow for their networks to support larger file uploads, higher-definition two-way video streaming, cloud gaming, and extended reality (XR) applications.

Uplink speeds in wireless networks often trail that of downlink speeds. This is most often due to the power requirements needed to beam a spectrum-heavy connection between a device and base station. Most end-user devices obviously have a smaller form factor than a cell tower so they need more creative antenna technology to support the signal and those end-user devices often rely on an embedded battery, which can quickly heat up and drain trying to power that connection.

T-Mobile US’ latest spectrum aggregation trial follows on a test earlier this year where it aggregated four carrier channels of spectrum running across its 5G SA network that produced network speeds of more than 3.3 Gb/s. Specifically, this involved integrating two carrier channels of 2.5 GHz spectrum and two carrier channels of 1.9 GHz spectrum for a total of 225 megahertz of spectrum.

Verizon has also been busy with smashing together its spectrum holdings to boost network speeds.

The carrier last year plugged quasi-licensed Citizen Broadband Radio Service (CBRS) spectrum into a 5G data session trial with Ericsson that showed it was able to use both the shared and licensed versions of the CBRS spectrum to boost network capacity. Verizon said it plans to use that spectrum to supplement the current use of its licensed C-band and millimeter-wave (mmWave) spectrum for its 5G network.