In its semi-annual State of Mobile Networks report this week, OpenSignal claims that both AT&T and Verizon have experienced a decline in 4G LTE speeds since each carrier reintroduced an unlimited data plan in February. OpenSignal blames the slowdown on an increase in data demand now that caps have been removed.

From April through June, AT&T's average LTE download speed was 12.92 Mbps, while Verizon averaged 14.91 Mbps, according to crowdsourced data from thousands of users with the OpenSignal app for iOS or Android.

By comparison, OpenSignal's last report measured average LTE speeds for AT&T and Verizon at 13.86 Mbps and 16.89 Mbps respectively, based on crowdsourced data collected from 169,683 users with the OpenSignal app for iOS or Android installed between October 1 and December 31, 2016.

August 2017 Report

AT&T: 12.92 Mbps
Verizon: 14.91 Mbps
Sprint: 9.76 Mbps
T-Mobile: 17.45 Mbps

February 2017 Report

AT&T: 13.86 Mbps
Verizon: 16.89 Mbps
Sprint: 8.99 Mbps
T-Mobile: 16.65 Mbps
T-Mobile was declared as the fastest network in the United States during the testing period. The carrier's average LTE speed was 17.45 Mbps, up from 16.65 Mbps in OpenSignal's last report. Sprint's average LTE speed also rose to 9.76 Mbps, up from 8.99 Mbps in the previous study.

AT&T or Verizon remained the fastest network in select U.S. cities, including Austin, Baltimore, Boston, Chicago, Denver, Houston, Indianapolis, Las Vegas, Los Angeles, Phoenix, Pittsburgh, San Diego, and San Francisco.

OpenSignal says its data is collected from regular consumer smartphones and recorded under conditions of normal usage, be it indoors, outdoors, in a city, or in the countryside. For this particular report, it said 5,073,211,200 data points were collected from 172,919 users between April 1 and June 30, 2017.

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