This 3G handset will have a high-resolution WVGA touch screen and incorporate a slide-out QWERTY keyboard. It will be available in select markets from October for 500 Euros.

Traditionally, all Nokia handsets have used the Symbian operating system, which is now fully controlled by Nokia. However, the Symbian system has lost charm for mobile phone users and become outdated compared to open source operating systems like Linux, Google Inc.’s (GOOG) Android and the licensed system of Microsoft Corp.’s (MSFT) Windows Mobile. A wireless handset based on the Maeme 5 operating system will allow users to run more than a dozen application windows at the same time.

N900 will have multitasking feature for applications together with web browsing (Mozilla-based Internet browser) that will support Adobe System Inc.’s (ADBE) flash software. This smart-phone will have ARM Cortex-A8 processor and 1GB of application memory. N900 also contains a 5-megapixel camera and 32GB of storage facility. Storage capacity will be expandable up to 48GB through a microSD memory card.

Nokia is the world leader in the high-end smartphone market but the company has been losing ground to fierce competition in recent times. According to Gartner Inc, Nokia’s share fell to 45% in the second quarter from 47.5% in the year-ago period. Meanwhile, Research In Motion (RIMM) grew its market share to 18.7% from 17.3% in the year-ago quarter and Apple Inc. (AAPL) gained 13.3% from a mere 2.8% in the prior-year quarter.

Nokia’s adoption of the Linux-based operating system is aimed to protect its leadership position in the smartphone market. Earlier this month, the company signed a deal with its former arch rival Microsoft Corp., to incorporate the mobile version of MS-Office software suite in Nokia handsets.