Microsoft is preparing a significant update to its Windows Phone 8 operating system. While the company has been pushing out smaller General Distribution Releases (GDR), the biggest change to Windows Phone 8 is expected to be released in early 2014. Windows Phone 8.1 will likely include a notification center, changes to multitasking, and even a "Cortana" personal assistant. Check out all the news below as we follow Windows Phone 8.1's progress.