Tag: Network evolution

Grayscale phone

Let’s Retire The CDMA/GSM Distinction

Christian 2 Comments

Understanding cell phone compatibility across networks can be tough. A common understanding has emerged: some cell phones are CDMA devices while other phones are GSM devices. According to the common understanding, GSM phones work with GSM networks, and CDMA phones work with CDMA networks. The common understanding has never been entirely accurate. For many years, a CDMA phone sold by Sprint wouldn’t necessarily work on Verizon’s CDMA network. Similarly, a GSM phone sold by AT&T wouldn’t necessarily work with T-Mobile’s GSM network. Beyond that, plenty of phone models have supported both CDMA and GSM.

Although the common understanding of the CDMA/GSM dichotomy wasn’t ever entirely right, it was at least useful or directionally accurate for many years. Not anymore. Networks are phasing out 2G and 3G technologies. All of the major networks in the U.S. today are dominated by 4G LTE technology. LTE isn’t GSM or CDMA. LTE is its own thing.

MVNOs typically can’t explicitly name their host networks. As a result, MVNOs often use the CDMA and GSM acronyms to label their networks. An MVNO that offers service over AT&T and Verizon’s networks might refer to the AT&T service as “the GSM service” and the Verizon service “the CDMA service.”

Just this week, the carrier Tello launched service over T-Mobile’s network. Tello is calling the T-Mobile network the “New GSM Network.” While I understand Tello’s rationale, I worry Tello is continuing a trend that ultimately confuses consumers about cellular technologies and phone compatibility.

PCMag Releases 2020 Cellular Performance Report

Christian

PCMag just released its 2020 report on the performance of cellular networks.

  • Verizon took the top spot for overall performance.
  • AT&T came in a close second.
  • T-Mobile came in third place but led in 5G availability.

Differences from previous years’ tests

Due to logistical issues from the pandemic, PCMag altered its methodology:

Traditionally, we’d tour each city and then test rural areas between cities before moving on to the next one. But that involves flights, rental cars, and hotels, none of which we felt safe using this year. So we hired roughly two dozen drivers to each test their own cities, in their own cars, sleeping in their own beds, shipping the testing kits from place to place. The result is a nationwide, COVID-safe test, but without the rural data we usually provide.

PCMag also started placing more emphasis on 5G connections. I’m a big fan of how PCMag handled 5G performance in its scoring (emphasis mine):

We had separate sets of 4G and 5G phones running tests offset by 60 seconds from each other…We ended up choosing the best result from each of the two devices on the same network, no matter what G they were on…What people really want is a consistent broadband experience—they don’t care what the icon on their phone says.

Reservations

Most of my reservations last year still stand. Notably:

  • PCMag focuses on performance within cities, while the largest differences between networks’ performance tend to show up in less-populated areas.
  • Average speed metrics get more weight than I think is reasonable.
  • Scores on different metrics get aggregated in a problematic way.

Highlights

While my reservations are serious, they’re not relevant to the granular, city-specific results. If you live in a large metro area, PCMag’s scorecard for your city could be handy.

The 5G-availability data is interesting. Here’s each network’s overall score for 5G availability:

  • T-Mobile: 54%
  • AT&T: 38%
  • Verizon: 4%

I’m surprised how close AT&T came to T-Mobile. While Verizon’s 4% availability score isn’t impressive, it’s higher than I anticipated. Verizon has been getting berated for the horrible availability of its exclusively millimeter wave 5G. Since Verizon hasn’t rolled out any 5G in some cities, the overall result masks heterogeneity between cities. E.g., PCMag found 9% 5G availability for Verizon in Chicago.

Woman making a skeptical face

Opensignal Released a New Report – I’m Skeptical

Christian

Opensignal just released a new report on the performance of U.S. wireless networks. The report ranks major U.S. networks in five categories based on crowdsourced data:

  • 4G availability
  • Video experience
  • Download speed experience
  • Upload speed experience
  • Latency experience

Verizon took the top spot for 4G availability and video experience. T-Mobile came out on top for both of the speed metrics. T-Mobile and AT&T shared the top placement for the latency experience metric.

Selection bias

I’ve previously raised concerns about selection bias in Opensignal’s data collection methodology. Opensignal crowdsources data from typical users. Crowdsourcing introduces issues since there are systematic differences between the typical users of different networks. Imagine that Network A has far more extensive coverage in rural areas than Network B. It stands to reason that Network A likely has more subscribers in rural areas than Network B. Lots of attributes of subscribers vary in similar ways between networks. E.g., expensive networks likely have subscribers that are wealthier.

Analyses of crowdsourced data can capture both (a) genuine differences in network performance and (b) differences in how subscribers on each network use their devices. Opensignal’s national results shouldn’t be taken too seriously unless Opensignal can make a compelling argument that either (a) its methodology doesn’t lead to serious selection bias or (b) it’s able to adequately adjust for the bias.

Speed metrics

Opensignal ranks carriers based on average download and upload speeds. In my opinion, average speeds are overrated. The portion of time where speeds are good enough is much more important than the average speed a service offers.

Opensignal’s average download speed results are awfully similar between carriers:

  • Verizon – 22.9 Mbps
  • T-Mobile – 23.6 Mbps
  • AT&T – 22.5 Mbps
  • Sprint – 19.2 Mbps

Service at any of those speeds would be sufficient for almost any activities people typically use their phones for. Without information about how often speeds were especially low on each network, it’s hard to come to conclusions about differences in the actual experience on each network.

When Will 3G Be Phased Out?

Christian

Last updated: October 22, 2021

Major U.S. network operators are phasing out their 3G technologies. Below, I share my impressions about the status of the major networks’ 3G phase-outs. It’s possible some network operators won’t stick to their deadlines (plenty of early deadlines have already been pushed back).

Verizon

Verizon has twice set and then pushed back deadlines for retiring its 3G network. The date is now set at December 31, 2022. Verizon committed to not push the deadline back any further.

Verizon has stopped activating 3G-only phones and phones that don’t support HD Voice. More details about Verizon’s plans and policies can be found in an entry on Verizon’s knowledgebase.

AT&T

AT&T plans to retire its 3G network by February 2022.

T-Mobile

T-Mobile has mostly stopped activating 3G-only phones. The company plans to shut down its 3G network as of July 1, 2022.

T-Mobile plans to shut down the legacy Sprint 3G/CDMA network it acquired by March 31, 2022.