Android 5.1 was just officially announced earlier this week and already several flagship devices are getting the update as we speak, but T-Mobile users will be happy to hear that the U.S. carrier is the first to roll out the new software in the United States.

"Today we are rolling out Android 5.1 - an update to Lollipop that improves stability and performance and offers a few new features like support for multiple SIM cards, Device Protection and high definition (HD) voice on compatible phones," Android's VP, Dave Burke, said in a blog post on March 9.

For Google's own Nexus devices, several models are getting the update right now, including the Nexus 4, Nexus 5, and Nexus 7 on the T-Mobile network. The build number for this software is LMY47D, so look for that ni automatic notifications or manually in your device's settings.

T-Mobile is calling the update mandatory, but it is currently only available over wi-fi with a cellular update to be provided at a later date.

To check your own T-Mobile Nexus device for the update, head to All Apps, tap System, then scroll down to System and tap About Phone. The updated software will be called LMY47D, but all other software versions will be either LRX22C, LRX21O, KTU84P, KTU84M, KOT49H, or KRT16M.

In order to properly update your phone, you'll need 50% or more battery life, a data connection via Wi-fi, and 22 MB of available memory.

Android 5.1 Lollipop features full support for multiple SIM cards for those who want better control over their mobile costs. "With Device Protection, your lost or stolen device will remain locked until you sign in with your Google account - even if someone resets your device to factory settings," according to the 5.1 announcement blog. The feature will be available on phones and tablets that will ship with 5.1 installed, and also for the Nexus 6 and the Nexus 9.

High definition voice calling is another feature of 5.1 that allows "crystal clear" calling with HD Voice between other compatible devices loaded with Android 5.1. The blog post says that both T-Mobile and Verizon's networks will have the feature for the Nexus 6, as an example.

Android 5.1 Lollipop also allows for better control over wi-fi network and Bluetooth switching directly from Quick Settings.

Android Police is reporting that the Nexus 7 2012 (wi-fi version) and the Nexus 10 tablet have also been seen with Android 5.1 installed, so it looks like Google's complete Nexus line may be set up from day one.

While T-Mobile is the first U.S. carrier to present Android 5.1, Verizon has confirmed that it will be launching the operating system update on March 12 with the Nexus 6. Other U.S. carriers have not yet been confirmed.