Single user gated system R D R D R D R D R D Customer i arrives @X, X-2 Xi-3 亚 W R W,=R+∑X,+V Weigiang Sun Communication Networks 5Weiqiang Sun Communication Networks Single user gated system 5 R D R D R D R D R D  Xi Xi-2 Vi Xi-3 Customer i arrives Wi Vi-1 Ri W R X V i i i i    