Apple will introduce a new version of the iPhone at an October 4 event, the first upgrade of its best-selling product since Steve Jobs resigned as chief executive officer. \"Let\'s talk iPhone,\" Apple said in an invitation to the gathering at its headquarters in California. The new iPhone will include a better camera and faster processor, people familiar with the matter said earlier this year. Introduced in 2007, the iPhone accounts for about half of Apple\'s revenue. Demand for the touch-screen gadget has helped catapult Apple ahead of ExxonMobil as the world\'s most valuable company. Jobs, who resigned as CEO and turned leadership of the company over to Tim Cook on August 24., is now Apple\'s chairman. \"The iPhone is the most important product line in the company,\" said Shaw Wu, an analyst at Sterne Agee & Leach. \"Cook will be heavily watched,\" because he didn\'t typically participate in major product introductions in his former role, Wu said. Revamped system Apple showed off new features of the iPhone\'s revamped operating system during Jobs\' last major Apple event, a developers conference in June. The new software, called iOS 5, includes new notification and text messaging systems. The company also said in June that it will debut iCloud, which lets users to wirelessly access music, pictures and other files across different Apple devices. The new iPhone could be Apple\'s best-selling product yet. Apple may sell 110 million iPhones in 2012, a faster pace than this year, when nearly 40 million were sold during the first half of the calendar year, according to Mike Abramsky, an analyst at RBC Capital Markets. Pent-up demand may help sales, said Maynard Um, an analyst at UBS Securities. Apple is unveiling a new model 16 months after the iPhone 4 debuted, compared with the 12 months between previous model updates. In addition to the stronger processor and improved camera, the new iPhone may have faster networking technology, improved graphics performance and potentially be thinner and lighter, Um said. This may be the last time Apple can wait so long between new iPhones as rivals including Samsung and HTC introduce competing smartphones using Google\'s Android operating system. \"A year and a half, especially in the smartphone product cycle, is many lifetimes,\" said Ashok Kumar, an analyst at Rodman & Renshaw in New York. Apple is set to expand the number of wireless carriers for the iPhone. Sprint Nextel will begin offering Apple\'s phone in the United States with unlimited data services plan this month, people familiar with the matter said. AT&T and Verizon Wireless now are the only two US carriers with the iPhone. The new iPhone probably won\'t be less expensive than the current model, which is sold to wireless carries for $600 (Dh2,203), said Gene Munster, an analyst at Piper Jaffray, in a research report. Service providers generally subsidise the price for customers. Instead of making the phone cheaper, Apple is likely to drop the price of the current model iPhone to give consumers a more affordable alternative, Munster said.