Delivering truly next-generation network speeds has been a challenge for U.S. cellular carriers, as their low, mid, and high band wireless towers have thus far required seriously awkward speed and distance compromises. Today, T-Mobile said it has successfully tested the next piece of its 5G strategy: Carrier Aggregation (CA) technology that will dedicate 2.5GHz mid band spectrum to downloads and 600MHz low band spectrum to uploads, simultaneously improving T-Mobile’s 5G speeds and reach across the United States.
In prior cellular generations, downloads and uploads generally shared a single radio frequency, equivalent to wired phone calls that put talking and listening through the same cable. Using carrier aggregation, T-Mobile is enabling a single phone to have separate inbound and outbound radio connections, spanning two radio frequencies that have been synchronized to seamlessly provide service together. This will let T-Mobile’s mid band towers handle outbound traffic at their best speed while slower but longer-reaching 600MHz low band towers take care of uploads, which don’t typically need to be as fast as downloads.
T-Mobile’s announcement has broader importance for businesses and end users, particularly in the United States, as it offers a clear path to widespread adoption of 5G cellular technology. Rival carriers Verizon and AT&T initially launched 5G exclusively using high band millimeter wave hardware that was extremely fast but barely covered individual city blocks, precluding large-scale rollouts. T-Mobile initially responded with a nationwide low band 600MHz 5G network that was roughly as slow as 4G in some places but faster in others. The carrier then augmented its service in some locations with a 2.5GHz mid band layer capable of much greater speeds. Combining those two layers in this fashion gives the carrier — and its rivals — a roadmap for effectively using existing “sub-6GHz” radio spectrum to deliver 5G service across