In their efforts to match T-Mobile's unlimited data plans, Verizon and AT&T are finding their own wireless networks squeezed. According to OpenSignal, which collects crowd-sourced measurements from millions of mobile network users, the Big Two carriers have experienced a marked decline in 4G speeds over the past six months, while speeds at T-Mobile and Sprint have accelerated, making T-Mo No. 1 in LTE speed and availability, OpenSignal said.
"Welcome to the new age of unlimited data in the U.S. In February, Verizon and AT&T brought back their unlimited plans, and the impact on their mobile data services was immediate."