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A Channel Assignment Algorithm for Multi-Radio Wireless Mesh Networks

A Channel Assignment Algorithm for Multi-Radio Wireless Mesh Networks. Stefano Avallone, Ian F. Akyildiz. Computer Communication, Jan. 2008. Outline. Introduction Problem Definition A Flow Rate Computation Method The MCAR Algorithm Performance Evaluation Conclusions. Introduction.

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A Channel Assignment Algorithm for Multi-Radio Wireless Mesh Networks

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  1. A Channel Assignment Algorithm for Multi-Radio Wireless Mesh Networks Stefano Avallone, Ian F. Akyildiz Computer Communication, Jan. 2008

  2. Outline • Introduction • Problem Definition • A Flow Rate Computation Method • The MCAR Algorithm • Performance Evaluation • Conclusions

  3. Introduction • Wireless mesh networks consist of a backbone with mesh routers • Mesh Router • Low mobility • Multi-radio • Transmission through wireless media

  4. Introduction • IEEE standards define multiple channels • IEEE 802.11a have 12 non-overlapping channels • IEEE 802.11b/g have 3 non-overlapping channels • Using multiple channels in multi-radio WMN greatly improve the network throughput

  5. Introduction • The channel assignment • The reuse of the same channel in a neighborhood • The bandwidth available on the network link • The channel assignment has to preserve the network connectivity

  6. Introduction • The static cannel assignment problem • Interference aware • To minimize the interference • Traffic aware • To make a given set of flow rate schedulable

  7. Introduction Each node has two radios 6

  8. Introduction Each node has two radio

  9. Motivation • Existing channel assignment • Only base on information related to node within the interference range • This may break the radio constraint • Depend on particular traffic profile

  10. Problem Definition |C| available channel κ(R1) ≧1

  11. Problem Definition • Interference model ch1 rI ch1 u v rT ch1 X

  12. Problem Definition The conditions ensures that a set of flow rate are schedulable e0 flow rate f(e0) Capacity c(e0) Depend on channel assignment

  13. Problem Definition • Goals

  14. Flow Rate Computation • To compute the flow rates having the objective to maximal the achievable rate • At this time • Channel assignment is not decide • The knowledge of the expected traffic demand is unknown

  15. Flow Rate Computation • To maximal the throughput • Using network throughput instead of the demand traffic • To compute the maximal achievable throughput • Channel assignment is not decide • The interference is also unknown • In this, the interference is absented • The channel assignment is assume to handle the interference problem

  16. Flow Rate Computation • Maximum the multi-commodity flow problem • NP-complete • Translate into single-commodity flow problem

  17. Flow Rate Computation Virtual node Virtual node capacity= ∞ capacity= ∞ Mesh gateway Mesh aggregation devices Mesh Router

  18. MCAR Algorithm • Two stages • Links are grouped based on the flows they carry • First stage assure that the number of different groups assign to its link does not exceed the number of radio • Each group is assigned a channel

  19. Link-group Binding

  20. MCAR Algorithm g1 rt rt g1 rt g1 e rt g2 g3 rt rt g1 g2

  21. Link-group Binding Assume the node has three radio R(e) = 1.5 R(e) = 2.3 R(e) = 1.2 J’’ 3 4 1 3 R(e) = 1.1 R(e) = 2.0 2 j’ R(e) = 1.3

  22. Link-group Binding R(e) = 1.5 g1 g2 R(e) = 1.0 g1 R(e) = 1.3 g2 g1 R(e) = 1.2

  23. Group-Channel Assignment

  24. Group-Channel Assignment

  25. Group-Channel Assignment rt rt rt ri ri P(g) : the set of links potentially interference with the link assign to group g ri

  26. Group-Channel Assignment rt rt rt S(g,c) : all the link that are assigned channel c and potentially interference with links of g ri εc: all the link that are assigned channel c ri

  27. Group-Channel Assignment

  28. Performance Evaluation • Compare with • LACA (Load Aware) • BSCA (Balanced Static) • Metric

  29. Performance Evaluation Transmission range 90m Interference range180m • Scenario1 • 25 nodes • 300m* 300m • Two radio 60% Three Radio 40% • Scenario2 • 50 nodes • 400m* 400m • Two radio 20% Three Radio 40% Four Radio 40%

  30. Performance Evaluation Capacity fixed to 54Mbps 25 nodes

  31. Performance Evaluation Capacity fixed to 54Mbps 50 nodes

  32. Performance Evaluation Capacity from 6 to 54Mbps 25 nodes

  33. Performance Evaluation Capacity from 6 to 54Mbps 50 nodes

  34. Throughput 25 nodes

  35. Throughput 50 nodes

  36. Delay 25 nodes

  37. Delay 50 nodes

  38. Conclusions • This paper proposed • A Flow Rate Computation • Independent from the traffic demand • Maximal the network through • A channel assignment scheme • Attempt to make a given set of flow rate schedulable

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