Understanding the mobile experience on T-Mobile’s standalone 5G network

Many different kinds of 5G service are now available. Most carriers have launched an early version of 5G technology that continues to rely on the availability of 4G service and access to the legacy 4G core network. This is called non-standalone access (NSA). But for most of the planned benefits of 5G — beyond speed alone — carriers need to offer standalone access (SA) where a smartphone connects exclusively to 5G signals and uses a modern 5G core network.

Standalone 5G is the future of the 5G experience and so it’s important to understand whether the real-world experience matches vendor claims. But globally, there are very few commercially available 5G SA networks. T-Mobile US is one of the first live 5G SA deployments and in Opensignal’s data is by far the largest. In our latest U.S. 5G country report we found that T-Mobile’s mobile experience — including 5G Availability and 5G Download Speed — improved significantly compared to six months before. So, we analyzed our users’ experience on T-Mobile’s 5G network before and after T-Mobile launched its nationwide standalone access (SA) 5G network on August 4, 2020, to investigate how SA technology can make a difference.

In Opensignal’s analysis of this early T-Mobile SA 5G mobile experience, we found that:

  • 5G Availability: Our users’ time connected to 5G significantly increased after the SA 5G network launched, and there was a larger jump in rural areas compared with urban.

  • 5G Latency: The responsiveness of the 5G experience improved with SA over NSA 5G as latencies fell. 

  • 5G Download Speed: However, our users did not experience faster speeds on SA 5G, because of the way T-Mobile has focused its use of SA on extending 5G Availability using its 600 MHz band. This is likely to change in 2021, as newer smartphones arrive that are able to connect simultaneously to both T-Mobile’s 600 MHz and 2.5 GHz 5G bands.

On August 4, 2020, T-Mobile announced the commercial launch of its nationwide standalone 5G network, claiming that the switch increased its 5G coverage by 30 percent, reaching 250 million people across the country. The operator argued that the SA network allowed it to “unleash its entire 600 MHz footprint for 5G”, while its NSA service depended on the use of higher frequency mid-band 4G/LTE which limited the reach of the 5G service. This is because lower frequencies tend to propagate further than higher frequencies; with NSA a smartphone must always connect to a 4G signal — as well as a 5G connection — and 600 MHz is the lowest frequency band T-Mobile is able to deploy.

To evaluate the impact of such an important network change, Opensignal analyzed our T-mobile users’ average 5G Availability — which represents the proportion of time Opensignal users with a 5G device and subscription have a 5G connection — across four points in time.

  • t-1 month: the average 5G Availability on the 30 days ending a month before the SA 5G launch. 

  • SA 5G launch: the average 5G Availability on the 30 days leading up to the SA 5G launch.

  • t+1 month: the average 5G Availability on the 30 days following the SA 5G launch.

  • t+5 months: the average 5G Availability on the 30 days ending five months after the SA 5G launch.

Opensignal data shows that, in the two months leading up to the SA 5G launch, T-Mobile’s 5G Availability growth was slowing. In urban areas, we saw an increase from 26% to 26.9% across these two months, while we observed no significant change in rural areas.

After T-Mobile launched its SA 5G network, we observed a sharp increase in 5G Availability across both urban and rural areas. In fact, 5G Availability in urban areas increased from 26.9% to 30% in the month following the network switch, while 5G Availability in rural areas grew by 3.6 percentage points and reached 28.1%.

We then calculated T-Mobile’s average 5G Availability five months after the SA network switch. T-Mobile’s 5G Availability in urban areas was then 31.5%, which represented a further increase of 1.4 percentage points. In rural areas there was a greater increase. 5G Availability in rural areas reached 33.3%, 5.2 percentage points higher than the month following the SA 5G launch, and 8.9 percentage points above the 5G Availability users experienced just before the launch.

Interestingly, by deep-diving into the 5G Availability, we observed how the difference in 5G Availability between urban and rural areas was the result of the different amount of time that urban and rural users spent connected to SA 5G. In fact, in the most recent 30-day period that we analyzed, urban and rural users spent 27.8% and 27.4% of their time, respectively, connected to NSA 5G, while they spent 3.7% and 5.9% of their time, respectively, connected to SA 5G.

Similarly, we observed a difference in the proportion of 5G measurements that we collected on either NSA and SA 5G networks across urban and rural areas. While the vast majority of our readings were collected in both cases on NSA 5G networks, the remaining SA 5G readings accounted for 14.7% of our 5G readings in urban areas, and reached 26.6% in rural areas. Our data therefore shows that T-Mobile’s standalone 5G network has significantly increased its average 5G Availability across both urban and rural areas, but actually benefited rural areas the most, as that is where T-Mobile users were now spending the largest proportion of their time connected to 5G, thanks to SA.

Improved latency — or network responsiveness — is one of the great goals of the designers of 5G. But these latency enhancements rely on using a 5G core network which isn’t part of initial 5G deployments that use NSA.

Latency is extremely important for multiplayer mobile gaming which carriers are using to market 5G services. Improved latencies also help real-time communications and they’re even important for web browsing where small latency delays requesting a file can add up due to the numerous files that together comprise a web page. 

Opensignal’s data shows users saw an improvement in their latency on T-Mobile’s SA 5G network compared to the NSA network. In urban areas, T-Mobile users, on average, experience a 23.8% improvement in latency compared to NSA, with a similar 21.6% improvement in rural areas.

But because T-Mobile has apparently focused on improving 5G reach in rural areas — where its fast 2.5 GHz 5G band was present less often — our data showed slower user speeds on standalone than on non-standalone 5G. Both in urban and rural areas, our T-Mobile users experienced faster average 5G Download Speed on NSA compared to SA, reaching 64.4 Mbps in urban areas and 53.4 Mbps in rural areas. By contrast, the average 5G Download Speeds we observed for users connecting with SA across urban and rural areas were 28.6 Mbps and 30 Mbps, respectively.

This difference in download speeds experienced on SA and NSA networks was likely due to the fact that the NSA connection used additional bandwidth from mid-band 4G/LTE, while the SA connection only used the 600 MHz band.

In fact, only the latest smartphone models released starting in 2021 — including the Samsung Galaxy S21 — have a chipset that supports aggregation of Frequency Division (FD) and Time Division (TD) spectrum, like T-Mobile’s 600 MHz and 2.5 GHz bands. Also, SA 5G user speeds cannot benefit from the use of existing aggregated 4G bands which NSA 5G users can tap into.


NSA 5G is still the default 5G network for T-Mobile users, but that will likely change soon

Opensignal data shows that T-Mobile significantly increased its 5G Availability due, for the most part, to the launch of its standalone 5G network. We also observed that the responsiveness of the 5G experience improved with SA over NSA 5G as latencies fell. Finally, the average 5G Download Speed experience on SA was slower than what our users experienced when connected to the NSA 5G network — which is likely explained by T-Mobile’s focus on increasing network reach and limitations in existing smartphone 5G chipsets. 

In fact, T-Mobile appears to have initially targeted its use of SA 5G to boost the reach of its 5G network, and therefore used its 600 MHz band for SA 5G — a low band that generally propagates further compared to higher bands like its 2.5 GHz band, but doesn’t allow for the same speeds. The challenge T-Mobile faced in late 2020 was that most 5G smartphones lacked the capability to connect to both a TD 5G frequency band like T-Mobile’s 2.5 GHz and a FD 5G band like its 600 MHz at the same time. Smartphones arriving from January 2021 fix this limitation and this will make it easier for T-Mobile to offer its SA service more widely. 

As T-Mobile users adopt the latest smartphone models that support 5G carrier aggregation of its low-band and mid-band spectrum (i.e., both FD and TD bands), we expect T-Mobile will expand the use of SA and its users’ average SA download speeds will likely rise as a result. 

SA is the future of 5G and the future of the mobile network experience. This early look at one of the largest SA 5G deployments provides real-world evidence about what that means for 5G users and for operators that are in the process of deploying SA or considering when to launch it.