Comcast has announced it is selling its 600 MHz 5G spectrum to T-Mobile, a move that will help the magenta carrier improve its nationwide 5G network.

Comcast purchased mid and low-band spectrum several years ago to build out its own 5G service. The company has started rolling out the mid-band spectrum and is offloading its low-band 600 MHz spectrum to T-Mobile.

Low-band spectrum offers superior range and building penetration, but is slower than mid and high-band spectrum. T-Mobile currently relies on low-band 600 MHz spectrum for its nationwide 5G, providing coverage in areas that are out of range for the other bands.

Comcast says T-Mobile will initially lease its 600 MHz spectrum and eventually purchase it altogether for roughly $3.3 billion.

Our 5G network field tests with CBRS spectrum have exceeded our expectations and we’ve found the band to be highly efficient and a significant part of a 5G network. This strong CBRS spectrum performance has made us realize that we are unlikely to need the 600 MHz spectrum licenses that we currently hold to support our wireless customers. As a result, we recently entered into an agreement with T-Mobile in which it will lease and eventually purchase our licenses in the 600 MHz band.

T-Mobile is already a user of 600 MHz spectrum, so it makes sense for us to enter into this “lease to purchase” arrangement so that they can put this spectrum to use in short order. We’ll continue to test with 600 MHz in our Philadelphia market and if our perspective changes, we’ve secured the option to reclaim the 600 MHz spectrum within our markets, giving us excellent optionality if we need it in the future.

The 600 MHz we are providing to T-Mobile includes a single 10 MHz license in most markets, so we don’t expect any material impact to our business. Under our agreement, Comcast will receive quarterly lease payments followed by a final payment of roughly $3.3 billion for the license purchase, which we expect to occur in 2028.