Whilst there was no mention of the codename “Tango” at Mobile World Congress, details about the upcoming update to Windows Phone 7.5 has been hinted in the various official blog posts from Microsoft and Nokia. Instead of having you to dig through the posts to find these details, we’ve summarised this all into a few points. See below:

1. Windows Phone “Tango” will still be branded Windows Phone 7.5. According to all the official blog posts and from Nokia. It is simply referred to as a “new software release that enhances Windows Phone 7.5 platform”. The updated Windows Phone SDK however, will be numbered as version 7.1.1, with support for emulation for devices with 256 MB of RAM.
2. Windows Phone “Tango” will be released in April 2012. According to the Nokia press release, the new software release for will be made “available from April”, at the same time the new Lumia devices are confirmed to launch in China.
3. Reduced minimum memory and processor requirements. Thanks to improved paging support to enable apps to automatically take advantage of more memory than is physically on the device, Windows Phone “Tango” will support devices with Qualcomm 7x27a processors as well as 256 MB of RAM while still enabling 95% of existing apps to run properly on these new phones.

   The developers for the remaining 5% of apps have been contacted to advise them to make their app compatible with the new 256 MB devices. Those apps incompatible with 256 MB devices will not be able to be installed on these devices. Built-in features such as Bing Local Scout and automatic photo upload to SkyDrive is also disabled on these 256 MB devices, and certain background tasks such as third-party app Live Tiles updating won’t be supported (however Fast App Switching and background audio is said to be still supported).

4. Support for China’s network and language requirements. This includes supporting China’s CDMA and WCDMA technologies, as well as working with local partners to provide up to six times as many preloaded apps.

In addition, the Windows Phone marketplace is also set to expand to 23 additional markets, including; Bahrain, Bulgaria, China, Costa Rica, Croatia, Estonia, Iceland, Iraq, Israel, Kazakhstan, Latvia, Lithuania, Qatar, Romania, Saudi Arabia, Slovakia, Slovenia, Thailand, Turkey, UAE, Ukraine, Venezuela and Vietnam. This brings the total number of markets to 63, and is said to bring 60% increase in the total addressable market for Windows Phone.

The Nokia Lumia 610 will come pre-loaded with Windows Phone “Tango”, and the new update is expected to be made available on all devices (depending on your carrier). Whilst Microsoft mentioned that the optimization work done on “Tango will be “largely invisible” to users, we expect more details will be revealed closer to release.