You can see the carrier signal from the tower. Pretty well too, it seems.
Unfortunately, the tower doesn’t see you so well. Either because of obstructions, a weak LTE transmitter, or both.
The problem with downlink is that your phone has to send constant acknowledgement of receipt back to the tower (Basically, “Got that, send more”). When the tower can’t see the, “Okay, send more”, it times out and begins pinging your phone. In that moment, the behavior of your phone is dependent on whoever manufactured or distributed it.
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