Congestion control in wireless networks pac perceptive admission control protocol
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Congestion Control In wireless Networks [ PAC: Perceptive Admission Control Protocol]. Goal. Control the amount of traffic in the network Provide high quality service to all admitted traffic Ensure the network congestion point is not reached. Background: Impacted area.

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Congestion control in wireless networks pac perceptive admission control protocol
Congestion Control In wireless Networks[PAC: Perceptive Admission Control Protocol]


Goal

  • Control the amount of traffic in the network

  • Provide high quality service to all admitted traffic

  • Ensure the network congestion point is not reached



Background: Impacted area

  • How is Reception Range defined

    • the maximum separation between a sender and receiver for successful packet reception as RxR.


Background receiver interference distance rid
Background: Receiverinterference distance (RID)

  • CSR>RID>RxR


Background

  • The distance between two senders to ensure proper packet reception at a receiver is RxR + RID.

  • This distance holds for all possible network scenarios. At any distance smaller than RxR + RID, it is possible that the transmissions of two senders will interfere with a receivers ability to properly decode a packet.


Background

  • The safe distance between two senders is 2RxR+RID


Determining the Available Bandwidth

  • MAC Layer Congestion Window

  • Queue Length

  • Number of Collision

    These methods provide little or no information regarding network utilization if a node is not actively transmitting packets.


Determining the available bandwidth
Determining the Available Bandwidth

  • Channel Busy Time

    • Transmitting

    • Receiving

    • Busy

  • The total time within an interval that a node is transmitting packets,receiving packets or sensing packet transmissions.


Perceptive admission control
Perceptive Admission Control

New CSR

  • A sender can consider only the traffic within this new CSR before admitting a new traffic


Contention aware admission control protocol cacp
Contention-Aware Admission Control Protocol (CACP)

A query message must be sent to all nodes within carrier sensing range.

If all CSN detect enough available bandwidth

then the flow is admitted.


Query flooding may fail

  • S2 is an isolated node, but it does affected by the new traffic brought by S1

  • Solution: use high power packet transmission to send the query message



Perceptive admission control1
Perceptive Admission Control

  • To prevent the channel congestion, PAC ensures that the quantity of admitted traffic is below the network saturation point by reserving a small portion of the bandwidth.

  • This prevents the channel from becoming congested and allows all admitted traffic to receive high delivery rates and low delay.


Mobility

  • What would happen if two sender-receiver pairs move closer than the safe range

?

75%

75%


Mobility
Mobility

  • Each source monitors the available bandwidth

  • Senders check available bandwidth after a random time and before sending a packet

  • Random back-off time


Advantage

  • PAC does not send query message, thus reduce the query overhead.


Conclusion
Conclusion

  • PAC effectively limits the amount of data traffic to avoid congestion

  • Provides consistent throughput, low packet loss and delay

  • Useful in wireless application that requires high QoS such as multimedia applications


Questions..?


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