Microsoft Corp. (MSFT) on Wednesday disclosed plans to overhaul its struggling Windows Phone software, unifying the underlying technology with its new computer operating system and adding features for mobile payments.

The new Windows Phone 8 software, revealed at an event for developers in San Francisco, is expected to arrive on smartphones that go on sale this autumn. Microsoft declined to give a more-specific launch date.

Microsoft said there will be Windows Phone 8 devices from Nokia Corp. (NOK, NOK1V.HE), HTC Corp. (2498.TW), Samsung Electronics Co. (005930.SE) and Huawei Technologies Co., which have used the current Windows Phone 7 version on their handsets.

'We will have the best device lineup we've ever had before,' said Terry Myerson, head of the Windows Phone group.

The current version of Microsoft's phone software evolved from Windows CE, an operating system that the company has offered for more than 10 years for phones and other devices.

With the new version, Microsoft is shifting to a kernel of software that shares technology with Windows 8, a update of Microsoft's operating systems for personal computers that is being adapted to work on tablet computers, too.

Microsoft said the shift will make it easier for software developers to more easily create applications for both Windows-powered personal computers and Windows Phone, and help developers with applications for Apple Inc.'s (AAPL) iPhone or devices powered by Google Inc.'s (GOOG) Android software to make those work on Windows Phone devices.

Microsoft is also allowing developers to create what the industry calls 'native' applications, which will allow them to create more-advanced videogame software, among other things.

The support of developers--which have helped to propel the popularity of Android and iPhone--is essential for Windows Phone, which has miniscule market share and lacks many of the games or other popular software on Android and iPhone.

Microsoft on Wednesday also disclosed plans to add some popular apps, including Zynga Inc.'s (ZNGA) Words with Friends and Draw Something, a Pictionary-like game that Zynga recently acquired.

Handsets that use the new Windows Phone 8 operating system will come with built-in mapping technology from Nokia, Microsoft's key partner in the smartphone market, the company said.

Microsoft, with a nod to an iPhone feature called Siri--also showed off speech-recognition software that developers can harness to let users launch and control apps with their voice, 'something Siri just now is learning to do,' said Kevin Gallo, head of developer platform for Windows Phone.

The company also disclosed a new 'digital wallet' for Windows Phone--a mobile-payment option--that will store consumers' credit-card information and loyalty-card information.

Google's Android also has a similar service, Google Wallet, and Apple recently introduced a service to store loyalty-card information and coupons. Many people believed the service was a precursor to a mobile-payments service.

Such mobile-payments systems have been limited because a slew of wireless carriers, merchants and credit-card companies all have to agree to support such services.

Microsoft said it will allow apps to tap the mobile-payment options, which will work with technology called near-field communication, or NFC, which links short-range wireless data transfers between a phone and a base NFC reader.

Microsoft Corporate Vice President Joe Belfiore said France Telecom SA's (FTE, FTE.FR) Orange will be the first wireless carrier to support the new Windows Phone digital wallet this autumn. Mr. Belfiore said Microsoft is talking to U.S. carriers but they won't support the digital-wallet feature until next year at the earliest.

Mr. Belfiore said the Windows Phone offering will be 'the most complete wallet experience on any smartphone this fall.'

It's unclear whether the new operating system and other developments will help Microsoft make a dent in the smartphone category dominated by Apple and Google. Together, those two companies powered eight out of every 10 smartphones shipped globally in the first quarter, according to research firm IDC. Nearly two years after Windows Phone devices first went on sale, Microsoft's market share in smartphones is about 5%.

Microsoft also said it will add a feature many developers sought: a system to let Windows Phone users make purchases inside apps. Many developers have found success making videogame apps free and then selling add-ons--for extra characters or songs, for example--once those people are playing the game.

Microsoft has long said Windows Phone will support such in-app purchases, but it hadn't yet made it available. Microsoft also said there are now 100,000 apps available for Windows Phone, which compares to half a million or more apps for iPhone or Android.

Kevin Shields, a Nokia senior vice president, spoke at the event about new or updated apps the company is rolling out, starting next week, for Windows Phone devices. Among the new apps are 'PlayTo,' which moves photos, video and music from the phone to some connected TVs, and a 'Counter' app to keep tabs on data and minutes usage.

Mr. Shields said the software efforts, including an updated maps app, are 'proof points of Nokia's commitment' to Windows Phone.

Shira Ovide