In other words the problem is not the Aruba AP, it's you're clients ability to comunicate back to the acces point, youre Laptop /Phone can be in range of the aruba AP, but the transmit antenas of youre Phone tablet may not be powerfull enough to link back to the aruba.
Thas why it's important the antena dbi power.. the weakest antenna is the one that determines the range of comunication.