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Enhancing TCP Fairness in Ad Hoc Wireless Networks Using Neighborhood RED

Enhancing TCP Fairness in Ad Hoc Wireless Networks Using Neighborhood RED. 吳政恭. Outline. Unfair TCP Behaviors in Ad Hoc Wireless Network Random Early Detection TCP Unfairness in Ad Hoc Wireless Network Neighborhood RED Conclusions. Unfair TCP Behaviors in Ad Hoc Wireless Network.

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Enhancing TCP Fairness in Ad Hoc Wireless Networks Using Neighborhood RED

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  1. Enhancing TCP Fairness in Ad Hoc Wireless Networks Using Neighborhood RED 吳政恭

  2. Outline • Unfair TCP Behaviors in Ad Hoc Wireless Network • Random Early Detection • TCP Unfairness in Ad Hoc Wireless Network • Neighborhood RED • Conclusions

  3. Unfair TCP Behaviors in Ad Hoc Wireless Network • Spatial reuse constraint : TCP flows may interfere with each other because of shared space. • Location dependency : Getting correct feedback of the bottleneck is critical to the fairness of TCP congestion control, limited information of the bottleneck situation causes significant unfairness.

  4. Random Early Detection • Average queue size: • Drop probability If average queue size is larger than ,the drop probability is set to 1

  5. TCP Unfairness in Ad Hoc Wireless Network • RED don’t work in wireless network or ad hoc network. Figure 1 Figure 2

  6. TCP Unfairness in Ad Hoc Wireless Network • A TCP connection which is penalized in channel contention may experience a queue buildup. • Congestion does not happen in a single node, but in an entire area involving multiple nodes.

  7. Neighborhood • Neighborhood: A node’s neighborhood consists of the node itself and the nodes which can interfere with this node’s signals.

  8. Neighborhood Queue Model

  9. Neighborhood Random Early Detection • A RED-like scheme to the distributed neighborhood queue, which we call Neighborhood Random Early Detection (NRED). • To solve 3 problem: • How to detect the early congestion of a neighborhood? Neighborhood Congestion Detection (NCD)

  10. Neighborhood Random Early Detection • When and how does a node inform its neighbors about the congestion? Neighborhood Congestion Notification (NCN) • How do the neighbor nodes calculate their local drop probabilities so that they add up to the targeted overall drop probability? Distributed Neighborhood Packet Drop (DNPD)

  11. Neighborhood Congestion Detection • A node wii monitor five different radio state: Transmitting , Receiving , Carrier sensing busy , Virtual carrier sensing busy , Idle.

  12. Neighborhood Congestion Notification • Calculate Pb()

  13. Distributed Neighborhood Packet Drop • RandomDrop()

  14. Conclusion • TCP performance is critical to the broad acceptance of multi-hop wireless networks. • The major contributions of NRED are the concept of a distributed neighborhood queue and the design of a network layer solution that does not require MAC modification.

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