KT Corp. secured regulatory approval Wednesday to switch off its second-generation (2G) wireless service next month, allowing the telecom giant to finally join the fourth-generation (4G) race that is heating up between its rivals.After rejecting KT\'s two previous bids, the Korea Communications Commission (KCC) voted to approve the carrier\'s plan to end its 2G mobile service in the 1.8 gigahertz bandwidth, an official said.The regulator gave KT two weeks to notify the company\'s remaining 2G mobile phone customers of the decision before the company halts the service on Dec. 8.The approval enables the country\'s second-biggest mobile operator to begin long-term evolution (LTE) service on the band, about six months after its rivals began offering their own high-speed 4G wireless technology.KT plans to invest 1.3 trillion won (US$1.13 billion) through 2012 to prepare for the next-generation wireless service, it said in a statement released following the regulator\'s decision.The stakes were high for KT to win permission to halt service for its 2G handset users. The mobile carrier needed 20 MHz in the 1.8 GHz band to start LTE service as smartphone users hiked bandwidth demand.The commission rejected KT\'s previous requests in April and July, saying the company\'s number of 2G handset users was too large to force an end to the service.KCC chairman Choi See-joong said earlier this month that the commission would positively review KT\'s bid if the number of 2G service users dropped to less than 1 percent of its total mobile subscribers.KT, which had 1.1 million 2G mobile phone users in March and 340,000 users by August, waged aggressive marketing campaigns to woo 2G mobile phone users to upgrade to third-generation (3G) handsets.Though its dogged campaigns sometimes faced a backlash and complaints from 2G users, the number dropped to 150,000 this month, less than 1 percent of its wireless subscribers.The remaining 2G users can subscribe to 3G mobile services or switch mobile carriers.SK Telecom Co., South Korea\'s largest mobile carrier, and No. 3 player LG Uplus Corp. began offering LTE service in July to meet soaring wireless data demand from smartphone users.