How do tablet OTA updates work? I'm thinking of buying the NVIDIA SHIELD K1 tablet. I was very impressed by the specs, especially as it's only $299. I noticed however, that it only shipped with 5.1 Lollipop. Of course, for a 2017 tablet this is appalling, especially with the recent release of Android Oreo. NVIDIA say they provide an OTA update to Marshmallow, although in South Africa, where I live, OTA updates are useless because cellular providers don't care about them. But then I realized something. The tablet doesn't have a SIM card, so it can't rely on cellular providers to send out the OTA updates, so how does it get them? And does it rely on cellular providers to give it to you?
What is OTA?
On mobile field such as smartphones, an over-the-air update may refer to a software update that is distributed over Wi-Fi or mobile broadband using a function built into the operating system, with the &quot;Over The Air&quot; aspect referring to its use of wireless internet instead of requiring the user to connect the device to a computer via USB to perform the update.
(Over The Air) Update procedure for Nvidia K1 with Wi-Fi:

Go to “System Upgrade” screen (Settings-&gt;About tablet-&gt;System upgrade) to enable full update image download.
From “System Upgrade” screen press the dots on the upper right corner and select “Advanced”. In the new menu screen tick the option “Check full upgrade”. Go back to the previous screen.
Now the “System Upgrade” will download the latest ROM image (Size of the update may vary).
When OTA download is finished, press Reboot/Install.

Saving OTA Update.zip for later usage from System Recovery:

If you don't tend to install your OTA now, then don't press Reboot/Install from Step 4, your downloaded update files are found the system.
Open your file manager (Ex: ES File Explorer File Manager) and navigate to “/data/data/com.nvidia.ota/app_download”. you will find OTA Update.zip file.
Move Update.zip to a known location, (Ex: Downloads folder “/storage/emulated/0/download”.
For later usage, reboot your tablet into recovery mode and flash your Update.zip stored on your choosen folder previously.

EDIT1:
How it works?
TLDR, There is an Update.zip file which will be sent through internet to your WiFi tablet, no cellular network is needed for your Wi-Fi Tablet.