init[n] = 1;            // Node is on the current backoff
            nodebusy[n] = 1;    // Node busy

            if (node[n].BackoffPeriod == 1)
            {
                node[n].State = 3;                          // Switch to carrier sensing in the next slot
                node[n].BackoffPeriod--;
            }
            else
            {
                node[n].State = 2;                          // Stay in the backoff state
                node[n].BackoffPeriod--;                    // Decrease Backoff
            }

            break;

if (node[n].carrier_sensing == 1 && chbusy == 0) // If channel is idle AND doing carrier sensing
            {
                node[n].carrier_sensing--;
                node[n].State = 4;  // Switch to Tx state in the next slot
                chbusy_cnt++;       // make channel busy
            }
            else    // Channel is BUSY
            {
                ` // -----------------------------------------------`

                 node[n].k++;
                if (node[n].k <= 5) {
                    node[n] = Node_init(node[n], node[n].k);
                    init[n] = 0;
                }
                else {  //k is over limited
                    node[n]= Node_init(node[n], min_k); //drop data
                    init[n] = 0;
                    tx_failure++;
                    total_pkt++;

                }

            }

            break;

            // ******************** Tx state *************************
        case 4:
            if (tx_cnt[n] == TxCntInit)
            {
                tx_cnt[n]--;        // Stay same state in the next slot
            }
            else if (tx_cnt[n] == 1)
            {
                //--------------------------------------------------
                if (chbusy > 1) {   //collision 둘 이상의 채널이 사용 중
                    chbusy_cnt--;
                    tx_cnt[n] = TxCntInit;  //initialize
                    tx_failure++;
                    total_pkt++;
                    node[n].State = 6;

                }
                else if (chbusy == 1) { //오직 한 노드만이 채널을 사용 중
                    tx_cnt[n] = TxCntInit;  //initialize
                    node[n].State = 5;
                    chbusy_cnt--;

                }
                else {
                    chbusy_cnt = 0;
                    printf("error alaramn");
                    exit(1);
                }

            }
            else
            {
                tx_cnt[n]--;    // Stay same state in the next slot
            }

            break;

            // ******************** Rx state *************************
        case 5:

            if (chbusy == 0)
            {
                chbusy_cnt++;   // Make CHANNEL BUSY for ACK transmission in the next slot
            }
            else
            {
                //------------------------ ----------------------------
                //if (chbusy == 1)
                //{
                    if (rx_cnt[n] == RxCntInit && idle == 0) {  //make an idle before sending ACK
                        idle = 1;
                    }
                    else if (rx_cnt[n] == 1) {  //successful
                        rx_cnt[n]=RxCntInit;
                        total_pkt++;
                        nodebusy[n] = 0;
                        node[n] = Node_init(node[n], min_k);    //reinitialize
                        init[n] = 0;
                        idle = 0;
                        chbusy_cnt--;
                    }
                    else {
                        rx_cnt[n]--;
                    }
                //}
                //else if (chbusy > 1) {
                //  chbusy_cnt--;
                /// rx_cnt[n] = RxCntInit;  //initialize
                //  tx_failure++;
                //  total_pkt++;
                //  node[n].State = 6;

                //}
                //else {
                //  chbusy_cnt = 0;
                //  printf("errror alarm2n");
                //  exit(1);
                //}


            }
            break;

            // ******************** Time OUT state *************************
        case 6:

            if (node[n].TimeOut == 1)
            {
                // -------------------------------------------------
                init[n] = 0;
                node[n] = Node_init(node[n], min_k);    //reinitialize
            }
            else
            {
                node[n].TimeOut--;
            }
            break;
        } // END: (( switch (node[n].State) ))
    } // END: Node loop

    chbusy = chbusy_cnt;
}   // END: simulation time