The speed boost is expected to be felt most downtown, along the beach areas, San Diego State University and UC San Diego, the company reported.

"We have invested significantly in our network in the San Diego area, so that residents can experience more consistent 4G speeds on a variety of 4G devices," said Darrin Silveria, Southern California vice president and general manager of T-Mobile USA.

The company said it has spent more than $30 million in network upgrades and improvements in San Diego since the beginning of 2010, and now has more than 600 cell sites operating 4G service in the western part of the county.