1. CS541 Advanced Networking 1 Static Channel Assignment and Routing in Multi-Radio Wireless Mesh Networks Neil Tang 3/9/2009

2. CS541 Advanced Networking 2 Outline  References  End-to-End Bandwidth  Problem Definition  Channel Assignment Algorithm  Bandwidth Aware Routing Algorithms  Simulation Results  Conclusions

3. CS541 Advanced Networking 3 References Tang-MobiHoc’2005: J. Tang, G. Xue and W. Zhang, Interference- aware topology control and QoS routing in multi-channel wireless mesh networks, ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc), 2005 (Acceptance Ratio:14%, Cited by 105 according to Google Scholar), pp. 68-77.

4. CS541 Advanced Networking 4 Wireless Mesh Networks (WMNs) Mesh Client Mesh Router Mesh Router/Gateway WLANWireless Sensor Network Cellular Network Internet Mesh Router/Gateway Mesh Router Wireless Mesh Backbone Mesh Router

5. CS541 Advanced Networking 5 End-to-End Bandwidth Instance: Link CAP = 1Mbps, single channel and single radio Connection 1 (A,D) Connection 2 (E,G) Wireless Mesh Backbone B D A C F E G 1/3Mbps

6. CS541 Advanced Networking 6 End-to-End Bandwidth Instance: Link CAP = 1Mbps, single channel and single radio Connection 1 (A,D) Connection 2 (E,G) Wireless Mesh Backbone B D A C F E G0.5Mbps 1Mbps 0.5Mbps 1Mbps 0.5Mbps

7. CS541 Advanced Networking 7 End-to-End Bandwidth Instance: Link CAP = 1Mbps, 3 channels {1,2,3} and 2 radios Connection 1 (A,D) Connection 2 (E,G) Wireless Mesh Backbone B D A C F E G 1Mbps 1 23

8. CS541 Advanced Networking 8 Assumptions  A stationary wireless mesh backbone network  Multiple radios in each node and multiple channels  The same fixed transmission power  Half-duplex and unicast communications  Static channel assignment  MAC layer: 802.11 DCF and scheduling-based

9. CS541 Advanced Networking 9 Connectivity Graph A D C F E G B G(V,E)

10. CS541 Advanced Networking 10 Network Topology (Communication Graph) A D C F E G B Network topology G A (V,E A ) determined by a channel assignment A {2, {1,3} {2,3} {1,2} {1, 2 1 1 3 2 3 2 1 3 3 (B,D;3) 3} 3 (A,C;2) (A,C;1)

11. CS541 Advanced Networking 11 Link/Topology Interference A D C F E G B Network topology G A (V,E A ) determined by a channel assignment A {2,3} {1,3} {2,3} {1,2} {1,3} 2,3 1,2 3,4 2,3 3,5 2,3 3,5 3,4 3,5 Link Interference: e.g., I(B,D;3) = 4 Topology Interference: e.g., I(G A ) = 5 1,1

12. CS541 Advanced Networking 12 Channel Assignment Problem Input: a network G and an integer K minimum INterference Survivable Topology Control (INSTC) problem: seeks a channel assignment A s.t. its corresponding network topology G A is K-connected and has the minimum topology interference.

13. CS541 Advanced Networking 13 QoS Routing Problem QoS Routing Problem: seeks a source to destination route and a channel assignment s.t. the end-to-end bandwidth requirement is satisfied. Connection 1 (A,D,0.5Mbps) Wireless Mesh Backbone B D A C F E G

14. CS541 Advanced Networking 14 Bandwidth-Aware Routing (BAR) Problem Link Load L(e) Link Available Bandwidth A(e) = CAP(e) - ∑ e’  IEe L(e’) Input: a network topology G A, ρ(s, t, B) Bandwidth-Aware Routing (BAR) problem: seeks a flow allocation F, s.t. the total s-t flow is B and that ∑ e’  IEe f(e’,ρ) ≤ A(e), for  e  G A. Remark: IE e – the set of links interfering with link e. f(e’,ρ) – the flow added to link e’ for establishing ρ.

15. CS541 Advanced Networking 15 A Complete QoS Routing Solution BAR Algorithm Feasible solution? End Output the solution and update N Y Block the request Static Channel Assignment Algorithm Network Topology

16. CS541 Advanced Networking 16 Channel Assignment Algorithm A D C F E G B 9 9 98 7 7 8 6 8 Link Potential Interference (LPI)

17. CS541 Advanced Networking 17 Channel Assignment Algorithm Theorem. The algorithm correctly computes a channel assignment whose corresponding network topology is K-connected in O(Kn 3 logm + m 2 ) time Binary search to find I min and k-connected G’(V,E’), s.t. LPI(e)  I min,  e  E’ Assign the “least” used channel to the link in G’ one by one based on 4 rules All Radios assigned? End Assign nodes having unassigned radios with the “least” used channels Y N

18. CS541 Advanced Networking 18 Channel Assignment Algorithm (Example) Instance: Q=2, Channel = {1,2,3}, K=2 A D C F E G B 3 1 1 3 2 3 3 2 {1,3} {1,2} 1 {1,3} {2,3} 2 1 Topology Interference I(G A ) = 4 2

19. CS541 Advanced Networking 19 Auxiliary Graph Construction A D C F E G B 3 1 1 3 2 3 3 2 {1,3} {1,2} 1 {1,3} {2,3} 2 1 2 C1C1 C2C2 E1E1 E2E2

20. CS541 Advanced Networking 20 Auxiliary Graph Construction C1C1 C2C2 E1E1 E2E2 D3D3 D1D1 F3F3 F1F1 G B2B2 B3B3 A2A2 A3A3

21. CS541 Advanced Networking 21 BAR LP Minimize Interference Impact : Flow Conservation: Variables: Interference: Bandwidth Requirement:

22. CS541 Advanced Networking 22 BAR Algorithm Theorem. The algorithm correctly solves the BAR problem in polynomial time. Solve the BAR LP Feasible solution? End Output the solution and update N Y Block the request Construct G A ’ Weakness?

23. CS541 Advanced Networking 23 Bottleneck Capacity The Link Bottleneck Capacity of link e, denoted by BC(e) is BC(e) = min e ∈ IEe A(e)/B. The Path Bottleneck Capacity of a single path P, denoted by BC(P), is BC(P) = min e ∈ P BC(e).

24. CS541 Advanced Networking 24 Maximum Bottleneck Capacity Path (MBCP) Heuristic (Single Path)

25. CS541 Advanced Networking 25 Maximum Bottleneck Capacity Path (MBCP) Heuristic (Single Path)

26. CS541 Advanced Networking 26 QoS Routing (n = 25, C = 3, Q = 2, c = 10.9)(n = 40, C = 3, Q = 2, c = 10.9)

27. CS541 Advanced Networking 27 QoS Routing (n = 40, C = 12, Q = 3, c = 53.9)(n = 40, C = 12, Q = 2, c = 53.9)

28. CS541 Advanced Networking 28 Conclusions  Simulation results show that compared with the CSP scheme, the BAR scheme improves the system performance by 57% on average.