1/2
100%
+
K=0
Station has
a frame to send
Wait TB
Send the
frame
Choose
R
????
[false]
K > Kmax
K=K+1
ACK
received?
[true]
[false]
[true]
Abort
Success
where all notations are referring to the following legend:
Legend
K: Number of attempts
T: Maximum propagation time
T: Average transmission time
TB: (Back-off time): R × T, or R × Tfr
P
R: (Random number): 0 to 2K-1
(a) Referring to the above flow diagram, summarize how the ALOHA protocol works.
(b) Fill in the blank (with question marks) in the diagram
(c) In the Aloha protocol, a term, vulnerable time, is defined as the length of time in which
there is a possibility of collision. Find the vulnerable time for the ALOHA protocol in
terms of Tfr