Algorithm 2: MBPCA

1: Node Vx receives an Emergency message from Vs;

2: if ForwarderAddress == ID(x)      //preferred forwarder

3:       if duplicate (MsgID)

4:           if CurTransHop < MsgHop;

5:               if wait to retransmission

6:                   Cancel retransmission procedure;

7:               end if

8:               if wait Ack || wait to forward

9:                   Cancel Ack timeout timer or forwarding;

10:             end if

11:         end if

12:     else if within the region of interest

13:         CurTransHop = MsgHop;

14:         Calculate the forwarding CW according to Equation (11);

15:         Choose preferred forwarder according to Equation (10);

16:         Start the MAC layer forwarding procedure and start the Ack timeout timer after send successfully;

17:     end if

18: else                //candidate forwarder

19:     if duplicate (MsgID)

20:          Follow the procedures in lines 4–11;

21:     else if within the region of interest

22:          CurTransHop = MsgHop;

23:          Calculate the forwarding CW according to Equations (12) and (13);

24:          Follow the procedures in lines 15–16;

25:     end if

26: end if

27: procedure AckTimeout()

28:     if enable retransmission && less than the limit of retransmission times

29:          Start the retransmission procedure;

30:     else

31:          Drop the packet;

32: end procedure