Wondering which carrier has the best 4G LTE service in the US? You may want to pay close attention to the latest report by mobile analytics firm RootMetrics, which have conducted 4G LTE performance tests in 77 markets with 725,000 collected data samples in the second half of 2012. Here’s the result.

When it comes to raw 4G LTE speeds, the study said that AT&T manages to trump the competition. On average, the download and upload speeds on AT&T’s LTE network reached 18.6Mbps and 9Mbps, while the average numbers for Verizon were 14.3Mbps and 8.5Mbps, respectively.

Sprint is number three on the speed list, as it clocked an average download speed of 10.3Mbps and 4.4Mbps up. T-Mobile won’t officially roll out its LTE service until later in the year, but its HSPA+ network delivered an average of 7.3Mbps and 1.5Mbps speeds.

According to the report, Verizon — not surprisingly — has the most extensive LTE footprint, with RootMetrics finding no difficulty in accessing Big Red’s LTE network in all 77 markets. Meanwhile, AT&T’s LTE network was only present in 47 of them, and Sprint in 5 markets. But remember that the tests were done last year, so the landscape may have slightly changed.

In the markets where LTE has officially gone live, they were able to connect to Verizon’s LTE network 93.2% of the time and AT&T’s and Sprint’s 81.7% and 50.2%, respectively. Both AT&T and Verizon fared well in the speed consistency tests, but overall, Verizon has the lead thanks to its wider coverage.

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