U.S.Patent Dec.8,2020 Sheet 4 of 9 US10,862,817B2 X Y RTT, RTT. RTT, 2 T 2 T+ RTT 2 2 FIG.5U.S. Patent Dec. 8 , 2 2020 Sheet 4 of 9 US 10,862,817 B2 X Y RTT RTT . T RTT , 2 T 2 . T + RTT 2 2 FIG . 5