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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Presentation Transcript
slide2
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
slide4

Background: Impacted area

  • How is Reception Range defined
    • the maximum separation between a sender and receiver for successful packet reception as RxR.
slide6

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.
slide7

Background

  • The safe distance between two senders is 2RxR+RID
slide8

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.

slide12

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.
slide15

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
slide17

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
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