Despite its major presence in the United States' wireless carrier market, AT&T has earned some user criticism for the problematic performance of some of its services. However, a recent study has partially vindicated the company's performance in data speed for Apple iPhone 4S units running on its network, according to TG Daily.

The news source reports that research firm Metrico came to this conclusion in a new study that analyzed 4S data speeds on all three of the device's U.S. wireless carriers: AT&T, Verizon Wireless and Sprint Nextel. AT&T devices had higher download speeds than devices on fellow carriers - five times the speed of Sprint and double that of Verizon.

This study does not mean that AT&T provides the "best" service for iPhone 4S users, however. The Metrico study also found that other aspects of the provider's wireless service faltered by comparison to Sprint and Verizon. Its voice quality, stability and rate of dropped calls ranked below both competing carriers. Sprint led in this category, making Verizon the middle-of-the-road carrier.

According to Business Insider, iPhone sales may have accounted for 40 percent of all smartphone sales during 2011's third quarter, as opposed to previous estimates placing the devices at a 30 percent smartphone and smartphone accessories market share.