Carrier signal is oscillating

My iphone 5 was jailbroken at version 7.0.6, so q pangu jailbreak came out, I restored to 7.1.1 version, even without having done the jaibreak, the carrier signal is falling and turning. Before restoring is 9 dots in tower operator, now is at most 3 and drops to 2 and the end is unsigned, is seeking and then back to 3 balls, and then drops the signal again, what should I do?

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