Severe game lag (Battlefield 3)

Hello.

I have problems that make battle unplayable. Namely - a time delay up to a second (!). Although the ping is shown as 50 ms, the lag is just that.
When there are few players on the map, and there are no extraneous sounds, then this delay can be detected. On the minimap I see that the enemy is nearby, I am waiting for him from the passage. And then: I hear a shot, the animation of death begins, the enemy runs out of the door, I die. Exactly in this sequence.

If the delay is caused by the CPU, then why is my picture smooth, without lags and FPS drawdowns?
Perhaps this is affecting the router. Then how to set it up so that it does not interfere with the game?