Nokia and Microsoft's Sept. 5 event is expected to unveil new Nokia Windows Phone 8 devices and perhaps offer another look at Microsoft's new mobile operating system. Technology website The Verge reports that two Nokia devices will be unveiled at the event.

Codenamed "Arrow" and "Phi," the devices could be in the Lumia range, according to The Verge's sources, who note that the aforementioned names are not final. Nokia CEO Stephen Elop confirmed to reporters recently that the company will release Windows Phone 8 devices, but he did not elaborate, The sources claim that the final design will arrive next month.

Microsoft's introduction of the Windows NT Kernel in Windows Phone 8 means Windows Phone 7 devices, including Nokia's existing Lumia devices, will not support the operating system. Microsoft offers Windows Phone 7.8 instead, bringing the new start screen to older devices.

Phi will apparently be a successor to the Lumia 800 and 900, featuring a "large curved glass display" and a polycarbonate body. AT&T will stock the device as an exclusive "hero" handset. Arrow, on the other hand, is to be stocked at AT&T and T-Mobile and will be a mid-range phone. The latter will also have a Verizon variant codenamed "Atlas," due for an announcement later. The Verge did not specify a timeframe.

Windows Phone 8 will bring improvements including a start screen with 3 tiles sizes, improved Xbox Live integration, and the ability to co-develop Windows Phone 8 and Windows 8 apps simultaneously. Recent reports revealed that the mobile platform's app store is lagging behind competitors, with under 200 apps submitted per day compared to over 700 on iOS.

Parts of an apparent upcoming Nokia Windows Phone device leaked recently, along with images of a prototype device. The latter sports the old Windows Phone start home icon, while featuring the claimed curved glass display and Lumia-esque form factor.

Despite Nokia's Lumia range selling 4 million devices, the number pales in comparison to the sales Apple and Google see with iOS and Android, respectively. Earlier in 2012 Nokia was knocked off the number-1 spot as smartphone manufacturer, with Samsung taking its place.

The Microsoft-Nokia conference takes place Sept. 5.