According to The NPD Group, more than one in five smartphones purchased in the second quarter (Q2) of 2011 were capable of running at 4G speeds. Sales of 4G smartphones reached 22 percent of overall smartphone sales, up from only 3 percent of smartphone sales a year ago.

"In the year since the debut of the EVO 4G, the number of 4G smartphone models has exploded," said Ross Rubin, executive director of industry analysis for NPD. "Carriers have great incentive to promote handsets that showcase their network investments and command premium data rates. 4G is ushering in the era of video on the go."

According to NPD?s monthly "Mobile Phone Track" service, following are the top four smartphone 4G manufacturers (OEMs), based on consumer sales in Q2 2011:

HTC: 62%
Samsung: 22%
Motorola: 11%
LG: 4%

HTC remains far and away the 4G-smartphone-share leader, comprising 62 percent of the 4G-smartphone market. In the second quarter (Q2) of 2011, the company also had the top three best-selling 4G-smartphone models on three different carriers: EVO 4G, Inspire 4G, and Thunderbolt. Sprint boasts the highest percentage of 4G smartphone sales; and is the only carrier for which 4G handsets comprised the majority of smartphone sales. NPD considers smartphones to be 4G if they support LTE, WiMAX or HSPA+ with downlink speeds of 14 Mbps/s or greater.

"Carriers have chosen to market 4G with different tradeoffs for handsets," said Rubin. "While HSPA+, for example, has not achieved the fastest wireless speeds in the market, it has allowed carriers to build portfolios quickly with benefits for form factors, battery life and price."