Sprint (NYSE:S) just reported fourth-quarter results, lifting share prices as much as 8.1% in early trading.

The third largest American telecom reported $9.1 billion in fourth-quarter revenue, a 1.5% year over year increase and ahead of Wall Street's $9.0 billion sales estimate. Sprint saw a $0.26 GAAP net loss per share, up from a $0.44 loss per share a year ago. Analysts were expecting a larger $0.34 loss per share.

Sprint added 682,000 subscribers in the quarter, including 58,000 postpaid customers on contract and 322,000 prepaid lines. Ninety-five percent of all postpaid phones sold in the fourth quarter were smartphones. The company reached a record high of 53.9 million total subscribers at the end of the quarter.

Looking ahead, Sprint expects adjusted EBITDA of roughly $6.6 billion in 2014, up from $2.4 billion in fiscal year 2013. Capital expenses will more than double, from $3.6 billion to approximately $8 billion.

This heavy infrastructure investment will mainly support the new Sprint Spark network, a triple-band LTE platform that promises network speeds of up to 150 megabits per second. Spark is available in 14 major markets today; Sprint hopes to cover more than 100 urban areas over the next three years.

"We are building a foundation for future success," said Sprint CEO Dan Hesse.