QoS Class Identifiers (QCIs) play a large role in the implementation of prioritization procedures on LTE networks. With the right tools, you can figure out the QCI your service is using. The approach I’ve taken requires the app Network Signal Guru (NSG) running on a rooted Android device with a Qualcomm chipset. Rooting devices presents some security threats, so I don’t recommend anyone root their device without doing some research first.
When NSG is running, users can scroll through a number of screens that display metrics related to network performance. If you’re connected to an LTE network, one of the screens will be titled “EUTRA Sessions.” The screenshot below comes from a test I ran using Google Fi’s service over T-Mobile’s network:
My Google Fi service had a QCI of 6 during regular data use. I also ran a test with service from Mint Mobile (an MVNO that uses T-Mobile’s network). During my test, Mint Mobile had a QCI of 7.
Making sense of networks’ prioritization procedures can be complicated. Network operators are usually not transparent about their policies. Disclosures and legal information published by the major networks provide some sense of each network’s policies, but the disclosures generally don’t shed as much light as I’d like. To get a better understanding of networks’ policies, I plan to collect QCI information from more carriers going forward. I’ll be sharing that information here. If you also use Network Signal Guru and would like to contribute your observations, let me know.