NEW YORK (AP) — Facebook Inc.'s fourth-quarter results, set for release after the closing bell on Wednesday, could surpass Wall Street's average expectations thanks to ad revenue growth, especially on mobile devices.

After a difficult 2012 that capped a disappointing initial public offering in May, investors have sent Facebook's stock up more than 16 percent this year in hopes that new advertising formats, especially on mobile devices, will help grow revenue at a fast pace.

The company's third-quarter results, posted in October, offered some proof that the company can make money from mobile advertising — a big concern for investors because most of Facebook's users access it on mobile devices. The company had said that that some 14 percent of its ad revenue came from mobile advertising — the first time it disclosed such a figure. Its adjusted earnings and revenue had surpassed Wall Street's expectations.

The company hasn't given financial guidance. Analysts surveyed by FactSet expect, on average, earnings of 15 cents per share on revenue of $1.51 billion.

Raymond James analyst Aaron Kessler, who recently upgraded Facebook to "Outperform" from "Market Perform," expects the company to report higher-than-expected results thanks to mobile growth, new ad formats and international expansion.

Wedbush analyst Michael Pachter also thinks that the company will beat Wall Street's expectations, with solid revenue "from a slew of new products, mobile growth, and increasing user engagement."

Its shares rose 50 cents, or 1.6 percent, to $31.29 in premarket trading.