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Joint Scheduling and Channel Allocation in Wireless Mesh Networks

Joint Scheduling and Channel Allocation in Wireless Mesh Networks. Nguyen H. Tran and Choong Seon Hong. Consumer Communications and Networking Conference (CCNC), 2008. Outline. Introduction System model Fair scheduling and Channel allocation algorithm Performance evaluation Conclusion.

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Joint Scheduling and Channel Allocation in Wireless Mesh Networks

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  1. Joint Scheduling and Channel Allocation in Wireless Mesh Networks Nguyen H. Tran and Choong Seon Hong Consumer Communications and Networking Conference (CCNC), 2008.

  2. Outline • Introduction • System model • Fair scheduling and Channel allocation algorithm • Performance evaluation • Conclusion

  3. Introduction • Wireless Mesh Networks (WMSs) • Routing • Scheduling • Channel allocation • Interference • Multiple radios, simultaneously • Limited number of channels available • Signal noise interference rate (SNR)

  4. System model • Network model • Network graphG(V, E) • V: the set of nodes (mesh routers) • E: the set of links • Qe(t): number of packets waiting to be transmitted on link e by the end of time slot; as queue length of e • K orthogonal channels (each node has one or more than one wireless interface cards)

  5. Interference model - physical interference model • packets along link (i, j) are correctly received when • RSSij: signal strength of node j when node i transmits to node j • ISSij: interfered signal strength from another node k also transmitting • N: white noise • Vs: the subset of nodes in V that are transmitting concurrently threshold

  6. Interference model - interference graph

  7. Conditions channel 1 channel 1 A B C • G’T = {e1, …, ek} E: certain edge set of transmissions on the same channel • A necessary condition: two links incident on the same node can not be activated simultaneously on the same channel • A sufficient condition: SNIR is above the desired threshold α • COROLLARY 1. • G’T in G(V, E) is feasible if every vertex of the corresponding interference graph G’(V’, E’) satisfies:

  8. Example of correspondinginterference graph 0.2 0.3 0.4

  9. Fair scheduling algorithm

  10. Channel allocation algorithm

  11. Example of fair scheduling and channel allocation capacity rank gateway channel 1 2 1 1-hop level channel 2 a b 2 3 channel 3 3 1 2-hop level channel 4 c f d e 1 2 4 3 4 g i j k 3 2 h 2 3 l m p 1 n o

  12. Example of fair scheduling and channel allocation transform interference queue length rank gateway e (n, o) = 0.3 e (n, o) 2 1 e (f, j) = 0.2 e (f, j) a b e (b, e) = 0.4 2 3 e (b, e) 3 1 e (gw, a) = 0.3 e (gw, a) c f d e 1 2 4 3 4 g i j k 3 2 h 2 3 l m p 1 n o

  13. Performance evaluation • Comparing with 802.11 CSMA/CA access scheme • Implemented in ns-2 • Transmission range of each node is 150m • Carrier sense range of 300m • Simulations are in the 800x800m2 area which 50 nodes are placed randomly

  14. Throughput Improvement Evaluation

  15. Fairness Evaluation

  16. Conclusion • Proposed fair scheduling and channel allocation algorithms to solve the interference problem • Improved system throughput and guarantees the fairness for all nodes

  17. Thank you

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