29-11-2012, 06:29 PM
Delay Analysis of IEEE 802.11 in Single-Hop Networks
delay-analysis ppt.ppt (Size: 844 KB / Downloads: 38)
The Distributed coordination function(DCF) backoff
DCF describes two techniques for packet transmissiom
Basic access mechanism
RTS/CTS access mechanism
The backoff time counter is decremented if the channel is sensed idle
Otherwise it is frozen in its current state until the channel is sensed idle more than a DIFS
Model Validation
Ns-2 simulator
Network size from 8 to 56 nodes
Packet size 1500 bytes
Nodes randomly distributed
Network area 20*20 m
No mobility
Performance metrics: service time and jitter
Conclusion
DSSS performs better than FHSS in term of delay and jitter
The higher the initial contention window size, the smaller the average service time and jitter are, especially for large networks
The binary exponential backoff algorithm has negative impact if both the maximum backoff stage and the number of nodes in the network are large