QCI and QoS: What does ‘unlimited’ actually mean on cellular data plans.

Before we delve into today’s unlimited plans, we have to go back a bit in history to understand today’s plans better. Prior to 2010, a majority of data plans were simply unlimited and added as a feature to calling plans. The prominent cellular data available at this time was 3G and data usage equated to unusable ‘mobile friendly‘ websites. When 4G launched it offered mobile data that could actualize true web browsing along with music and video streaming capabilities. Because of 4G, we changed how we used our cell phones, and carriers changed how they billed our cellular plans. In 2010, AT&T discontinued unlimited data plans and Verizon followed suit in 2011. Calling plans become unlimited, and data was now usage billed. Carriers pivoted from offering rollover minutes to rollover data. The one carrier to maintain unlimited data throughout this time was: T-Mobile. T-Mobile continued to offer unlimited data on their ‘contract’ plans; but following their un-carrier rebranding in 2013, T-Mobile began offering the first contract-free unlimited plans in 2014.

Even though ‘unlimited’ plans were discontinued by Verizon and AT&T, multiple customers still held onto those grandfathered plans. In 2011 AT&T instituted a new network management policy capping the unlimited data rate to 500kbps for ‘heavy data users’ (heavy data users turned out to be: those that used 5GB of data). Verizon was going to pursue a similar plan in 2014, but took a u-turn when the FCC stated: “Reasonable network management’ concerns the technical management of your network; it is not a loophole designed to enhance your revenue streams,”. In 2015 the FCC ultimately proposed a $100M fine against AT&T for modifying the terms of its grandfathered unlimited data plans after purchase. AT&T settled that fine with the FTC for $60M in 2019. The FCC clarified in 2014, that “unlimited means unlimited” and that network management practices must be disclosed to the customer at the time of purchase.

Following T-Mobile’s head start on offering unlimited plans again, AT&T brought back unlimited data plans in 2016, and a year later, Verizon joined everyone else by offering an unlimited plan again.

That brings us to today, because of the FCC’s intervention, unlimited plans now disclose the variety of network management practices used and how ‘unlimited’ the data actually is. Initially the concept at the start was simple: after “x” GBs the customer might experience slower data speeds or be deprioritized behind other traffic on the network.

Data prioritization is possible as data on the cellular networks are tagged with what type of QCI (QoS Class Identifier) level it has. The lower the QCI identification number, the higher the priority it has to complete its network request over other the higher tagged QCI traffic. On most cellular data plans, QCI has data prioritization ranging from QCI-6 to QCI-9. This means that data tagged QCI-6 has the highest level of priority while data tagged QCI-9 has the lowest level of priority. QCI-9 tagged data would be completed after any other higher prioritized data request being handled by the carrier at that time. This means that QCI-6, QCI-7, and QCI-8 network requests would be completed before any QCI-9 request.

When it comes to being deprioritized, unlimited plans today are a little bit more complicated: there are plans that are always deprioritized (QCI-9), plans that have an allotment of priority data before being deprioritized (QCI-8 or QCI-7), and plans that offer an allotment of ‘higher priority’ data access above standard plans (QCI-6). Along with the different types of data prioritization, plans may also include a hotspot subject to its own de-prioritization level.

An upcoming followup post will compare the current cellular plans available from carriers and their MVNOs as well as comparing the prioritization level of each plan: The next post is now available!

Let us know in the comments below if this article was helpful, or there are areas that we should elaborate on


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