Prior to the underground garage open the phone, did not always network signal, on / off flight mode, turn off / on the network are also over a period of time before there is a network.
Two days ago when I saw a mobile phone signal, there are a choice, whether to open automatically select the operator to cancel automatic selection, the search for some time operators, pop manually select Mobile, China Unicom, Telecom's option, because the phone card is on telecommunications select Telecom. Then turn back several times in the underground garage phones, also have 4G signal properly solve the problem of mobile phones in the underground garage of the old no signal.
Internet looked at the reasons, to the effect that if the option is turned on automatically operators, handset through a bad signal area network signals to be networked lose again, it will automatically enter the election process operators in the mobile, networking, telecommunications, select, and if to manually select, you choose the network operator when again, the speed will be faster.
So if it is determined that he has been using a certain type of card, or turn off the automatic selection is better, there is no signal passes through the signal area network faster. Re-selection to operators in changing the card.
In fact, life in many automation are also a price to pay, the real master in this field are often manual operation.