dB =10log P1 P2
dB =10log P1 P2
dB =10log P1 P2
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! All users are synchronised to time slots<br />
! Vulnerable period is now t p<br />
! p 0 =e -G which leads to<br />
! S=Ge -G<br />
! Maximum throughput is where G=1 so<br />
! S=1/e=0.368 twice that of pure aloha<br />
! Three possibilities when channel is sensed idle<br />
CSMA Protocol Characteristics<br />
Nonpersistent<br />
1-Persistent<br />
p-Persistent<br />
If medium is idle - transmit<br />
If busy, wait a random time and re-sense channel<br />
If medium is idle - transmit<br />
If busy-continue listening, transmit once idle<br />
If medium is idle - transmit with probability p<br />
Listen until channel idle, transmit with probability p<br />
101 102<br />
103<br />
! S is expressed in terms of G and a<br />
! “a” is a Non dimensional parameter<br />
a =<br />
propagation _ delay<br />
packet _ transmission _ time<br />
This equates to the vulnerable period!<br />
104
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