SRG detects ‘problematic’ interoperability issues around T-Mobile’s Minneapolis network


By: Monica Alleven

Signals Research Group (SRG) set out to conduct a benchmark study of T-Mobile’s 5G New Radio (NR) network in and around the Minneapolis-St. Paul market and uncovered some problematic interoperability issues along the way.

It appears to be literally along the way because SRG founder Mike Thelander said he started noticing the problem in the more rural areas while traveling from Independence, Minnesota, on the way to Minneapolis, where it became less pronounced.

Specifically, the interoperability issue appeared to occur between a Qualcomm chipset and the infrastructure, which in this case was supplied by Nokia. SRG used test equipment from Accuver America and Spirent Communications in its study, along with the OnePlus McLaren and the Samsung Galaxy Note 10 Plus.

Fierce reached out to T-Mobile and Qualcomm for this story and did not hear back with comment or explanation.

Nokia provided the following statement: “Nokia has not received any customer complaints about network issues in Minneapolis/St. Paul, nor in any additional areas where we provide T-Mobile’s 5G network. Additionally, the alleged issue has not been reported in any of our other customer networks. With the information at hand, we are led to believe this is likely an issue on the devices that were utilized for the test.”

Exacerbating the problem?

Thelander described receiving error messages while testing and depending on the severity of the occurrence, the network either limited the number of LTE and/or 5G NR network resources, known as resource blocks, it assigned to the smartphone, or the network severely limited the number of allocated resource blocks for both radio bearers.

“The first scenario led to reduced data speeds for one or both radio bearers. In some cases, the resultant data speeds were still reasonably good so a typical consumer would never know. In the second scenario, the smartphone’s data speed was at or near 0 Mbps. In some of our initial testing, we even had to reboot the phone to resolve the problem,” Thelander wrote in a report last week summarizing the study.

While his tests typically put extraordinary stress on a network, it stands to reason that some consumers with 5G phones would notice it, but it’s unknown how many people are using 5G phones on T-Mobile’s network in a given market today. Plus, if they’re just syncing email, it might not be noticeable.

“I may have exacerbated the problem by the types of testing I’m doing” while moving around from cell to cell, Thelander told Fierce. But if a consumer were downloading a movie from Netflix or a big app from Google Play, “that’s very similar to what I do,” he said.

“It’s not as obvious as a dropped call, but if you all of a sudden aren’t getting any data … the consumer should notice that,” he said. “When you’re getting no throughput, it doesn’t take a rocket scientist to know that something’s not working right.”

T-Mobile uses infrastructure from both Nokia and Ericsson for its LTE and 5G deployments.

In the report, SRG wrote that the interoperability issue appears to be a somewhat recent occurrence, perhaps coinciding with the introduction of new vendor software releases. It is also an issue that could include Ericsson infrastructure, although “we do not believe the problem is nearly as dramatic as we observed in our Minnesota testing.”

Thelander said it’s his understanding that there is a fix being tested and it potentially could be pushed out to smartphones and/or infrastructure. “Additionally, we were able to work around these performance issues to provide analysis which helped us exclude the impact of the degraded performance,” he wrote.

SRG’s clients include the likes of T-Mobile, Qualcomm and Nokia, as well as handset makers and other wireless vendors and service providers.