A new software is heading towards several of Google's Nexus mobile devices released in the past few years. T-Mobile is currently distributing security updates to their subscribers who own the LG Nexus 4, LG Nexus 5, Motorola Nexus 6, Asus Nexus 7, and HTC Nexus 9.

The magenta carrier has posted dedicated support pages for the update in its website. Other major U.S. carriers are expected to issue their own software upgrades soon.

On Tuesday, the update has begun to roll out on the abovementioned Nexus models in stages. It can only be downloaded over-the-air (OTA) via Wi-Fi as of now. T-Mobile noted that installation of the new security upgrade over cellular network will come at a later date.

The company's support pages also mentioned that these updates are mandatory for the Nexus line. Aside from Android security improvements, all of the listed Nexus handsets will also get minor bug fixes.

Early last month, Google announced that it will notify all manufacturers that produce Android devices, including LG, about security issues in a monthly security bulletin. The search giant also said that it will begin sending out security-focused OTA updates every month for their Google co-branded Nexus models. The announcement comes in the aftermath of the much hyped revelation of the Android security vulnerability called Stagefright.

The T-Mobile update will bring Android 5.1.1 Lollipop with build number LMY48M. It will be similar to all the mobile devices mentioned except for the Nexus 6, which is apparently tied to build number LYZ28K.

Since there will be no new features inside the new software, these updates' file size are small. For instance, the security patch for the Nexus 6 is just 28.9MB and less than 20MB for the other Nexus handsets, so it will not take long for the entire upgrade to be downloaded and installed.

However, it might be a while before some T-Mobile subscribers receive the Android 5.1.1 security update. Similar to previous roll outs, the company is releasing the new software in phases so it might take a few days until it reaches all devices.

Security upgrades do not exactly fuel excitement among users but it is always a good sign to see Google following through with its promised monthly software enhancements. These Lollipop updates come ahead of the Android 6.0 Marshmallow's reported arrival via the new LG Nexus 5X and Huawei Nexus 6 announcement, which should be later this month.