AT&T said Friday it recently completed more than $375 million in improvements to bolster its wireless and wired network infrastructure in the Baltimore area.

Last year the company made 76 network upgrades including expanded 4G LTE coverage in Baltimore County through upgraded cell sites in Catonsville, Fork and Sparks, the company said. It also added a 4G LTE cell site near Baltimore's downtown sports complexes.

AT&T does not release details about upcoming network upgrades, spokewoman Elyssa Rae said. But she said the investments are part of a three-year plan called Project Velocity IP that runs through 2015. AT&T plans to spend $14 billion nationwide.

Rootmetrics — an independent research firm — recently ranked AT&T as the top cellular carrier in the Baltimore area for speed and reliability. Rival carrier Verzion, however, ranked first nationally in the same survey. Verzion also garnered high marks for the reliability in the Baltimore Rootmetrics survey.

timswift@baltsun.com