T-Mobile took another step in getting more out of its low- and mid-band spectrum for 5G, completing a successful standalone (SA) 5G carrier aggregation test on the LG Velvet 5G smartphone.
5G New Radio carrier aggregation (NR CA) combines different channels of spectrum (in this case T-Mobile’s 600 MHz and 2.5 GHz) for more capacity. While T-Mobile isn’t the only operator that’s tested NR CA, it said this is the first completed in standalone mode on a commercial 5G device.
MediaTek was involved, as its Dimensity 1000C 5G chipset powers the LG Velvet 5G smartphone. Ericsson provided 5G radio access network gear for the test, including hardware and software.
As it stands, the LG Velvet is the only 5G device from T-Mobile that’s capable of NR CA, but T-Mobile declined to share a timeline for when it plans to roll out the capability in its network. Ericsson, for its part, confirmed earlier that it will offer a commercial release of 5G NR carrier aggregation in the fourth quarter of 2020.
For the recent test, NR CA brought together (or aggregated) 100 megahertz of T-Mobile’s 2.5 GHz spectrum and 20 megahertz of low-band 600 MHz spectrum, a spokesperson confirmed. This helped boost speeds thanks to increased capacity, and extended the reach of the key mid-band frequencies.
T-Mobile saw on average a 20% boost in download speeds on 2.5 GHz, versus not using CA to combine the 600 MHz channel. It said that figure will improve down the line. A video shows speed tests in the upper 800 Mbps range, as well as hitting above 1 Gbps. That compares to the average of 300 Mbps that T-Mobile has said users can typically expect on 2.5 GHz.
Carrier aggregation also expanded the coverage of its 2.5 GHz spectrum, which still has better signal reach and penetration than millimeter wave but can’t travel as far as low-band spectrum.
T-Mobile attributed the improvement to using a low-band uplink together with a mid-band downlink.
“By combining a mid-band downlink with a low-band uplink, the 2.5 GHz 5G signal will travel as far as the base station allows without being limited by the mid-band uplink. Instead, the uplink will travel back to the tower on low-band 5G, which travels farther,” T-Mobile said in the announcement.
T-Mobile is the only U.S. operator that has a nationwide 5G standalone network, which launched in August and means it no longer relies on an LTE core.
AT&T’s Igal Elbaz recently called out carrier aggregation as a specific feature when talking about the need for widespread ecosystem support in order to support SA scale and capabilities.
Operators and vendors have been testing out the technology. Verizon, for example, hit 4.2 Gbps 5G speeds by aggregating eight channels of millimeter wave spectrum in February tests with Samsung and Qualcomm. Ericsson and Qualcomm, meanwhile, reached peak speeds of 2.5 Gbps in the 2.5 GHz band during standalone NR carrier aggregation tests over the summer.
As for T-Mobile, the operator’s also been testing other technologies, like multi-user MIMO (MU-MIMO), to increase spectral efficiency and reach more people with 2.5 GHz. T-Mobile’s been moving quickly to turn on the new spectrum acquired through its Sprint merger. It just activated 2.5 GHz in 121 new locations, bringing the tally 210.
T-Mobile’s nationwide 5G network that largely uses 600 MHz currently covers more than 250 million people across 1.3 square miles.