I can use my Ipad Retina (4th Gen, iOS 9.3.1) when plugged in via USB to tether the 3G connection.
After it is plugged into USB, then I can see it shareable via wifi from other devices. (My Mac which is it plugged into via USB, and my iPhone 6S).
After I unplug the USB from the Macbook, the devices that connected to the iPad via wifi can still maintain the connection, but it is no longer discoverable on wifi. (And if I restart the iPhone it remains paired).
My question is: How do I make my iPad Retina wifi hotspot discoverable (tethering 3G) when off and unplugged like my iPhone 6S?