T-Mobile Buying Low-Band Spectrum from Comcast, as Comcast Launches its own 5G Network

T-Mobile has reached an agreement to lease and then purchase radio spectrum licenses from Comcast worth $3.3 billion. The licenses are for 10 MHz of bandwidth around 600 MHz (band 71). T-Mobile already uses band 71 to provide blanket coverage. As one of the lowest frequencies in use for cellular networks, 600 MHz reaches long distances and well into buildings, with tradeoff of not providing the best high-speed data rates. This additional spectrum should help T-Mobile improve the baseline capacity of its network in areas where higher-frequency bands don't reach, improving network coverage and reliability. Comcast is preparing to launch its own 5G network starting this month in Philadelphia. The company has been testing its own 5G network in both the 600 MHz and CBRS (band 48) bands. Performance in the unlicensed band 48 has "exceeded our expectations", leading to the conclusion that Comcast is "unlikely to need the 600 MHz spectrum licenses that we currently hold to support our wireless customers." But the spectrum is valuable, especially to T-Mobile. Comcast has offered Xfinity Mobile wireless service to its home internet customers for several years using the Verizon network. Launching its own network in select markets will reduce traffic from Xfinity Mobile customers on the Verizon network, and presumably save money for Comcast. Verizon also uses band 48, so most of Xfinity's lineup of (Verizon-compatible) phones already support band 48, while not all support band 71.