i-pad drops internet

We are having the very same issue. It happen several times a day with my wife's ipad, and maybe once or twice a day with mine. But it seems not to be the T-Mobile cellular signal, but its built in wifi router. I.e., I added another router to the T-Mobile cellular device and connected both ipads to that router and not the T-Mobile wifi signal. Lo and behold, the problem has gone away. So it appears it's the T-Mobile wifi signal that is the problem, and not the T-Mobile cellular internet connection. BTW, before I switched to a new wifi router we got around the problem by turning wifi off then on again on the ipad.