Routing and Scheduling in Wireless Grid Mesh Networks Abdullah-Al Mahmood Supervisor: Ehab Elmallah Graduate Students’ Workshop on Networks Research Department of Computing Science University of Alberta

Workshop, 17 Nov Outline Mesh networks Mesh networks Non-bifurcated routing Non-bifurcated routing Interference-free scheduling Interference-free scheduling Multi-flow routing & scheduling Multi-flow routing & scheduling Incremental routing & scheduling Incremental routing & scheduling Remarks Remarks

Workshop, 17 Nov Mesh Networks Static mesh routers (backbone) Static mesh routers (backbone) Clients connect to mesh routers Clients connect to mesh routers Can be an end-user or a network hotspot Can be an end-user or a network hotspot One or more gateways One or more gateways

Workshop, 17 Nov Mesh Networks

Workshop, 17 Nov Grid Mesh Network System System IEEE PHY IEEE PHY Temporally synchronized routers Temporally synchronized routers Time-slotted operation Time-slotted operation Topology is (almost) grid Topology is (almost) grid Assumptions Assumptions Single gateway Single gateway Client mobility within single router domain Client mobility within single router domain

Workshop, 17 Nov Non-bifurcated Routing Focus: Traffic in backbone network Focus: Traffic in backbone network Each flow on a non-bifurcated route Each flow on a non-bifurcated route 1,2,3,1,2,31,1 3,3 2,2 3,1 2,2 1,3 Single path routing Non-bifurcated routing Multi-path routing

Workshop, 17 Nov Interference-free Scheduling During any time slot, concurrent transmissions are pairwise non-interfering During any time slot, concurrent transmissions are pairwise non-interfering R I = Interference range R I = Interference range Distance between either end of one transmission more than R I distance away from both ends of the other transmission Distance between either end of one transmission more than R I distance away from both ends of the other transmission Preserves bi-directionality of routes Preserves bi-directionality of routes

Workshop, 17 Nov Multi-flow Routing & Scheduling Consider all flows at once Consider all flows at once Hard optimization problem Hard optimization problem Approximation (e.g., relax to linear program) Approximation (e.g., relax to linear program) Multi-path solution (e.g., Alicherry et al., ’06) Multi-path solution (e.g., Alicherry et al., ’06) Consider smaller number of flows (e.g., 2) Consider smaller number of flows (e.g., 2) Same scheduling heuristic Same scheduling heuristic Better throughput than single flow (BROADNETS ’09) Better throughput than single flow (BROADNETS ’09)

Workshop, 17 Nov Multi-flow Routing & Scheduling Pros Pros Computation is efficient for certain sets of routes (e.g., shortest path) Computation is efficient for certain sets of routes (e.g., shortest path) Cons Cons Search space grows rapidly for more than 2 routes Search space grows rapidly for more than 2 routes Exact scheduling algorithm is not known Exact scheduling algorithm is not known

Workshop, 17 Nov Incremental Routing & Scheduling Consider one flow at a time Consider one flow at a time Scheduling  coloring the conflict graph Scheduling  coloring the conflict graph Links are vertices Links are vertices Interference indicated by edges Interference indicated by edges For each candidate route of the flow For each candidate route of the flow List color the route portion of conflict graph List color the route portion of conflict graph

Workshop, 17 Nov Incremental Routing & Scheduling In grids, scheduling can be done efficiently for a large number of routes In grids, scheduling can be done efficiently for a large number of routes In case of shortest paths, and R I larger than the transmission range, exact algorithm for scheduling takes linear time (GLOBECOM 2009) In case of shortest paths, and R I larger than the transmission range, exact algorithm for scheduling takes linear time (GLOBECOM 2009)

Workshop, 17 Nov Remarks Incremental scheduling can be useful in non-grid topologies Incremental scheduling can be useful in non-grid topologies Interference model/constraints are being revisited Interference model/constraints are being revisited Distributed implementation/approximation with the newly released standard (2009) to be explored Distributed implementation/approximation with the newly released standard (2009) to be explored

Workshop, 17 Nov References M. Alicherry, R. Bhatia, and L. Li, “Joint channel assignment and routing for throughput optimization in multiradio wireless mesh networks,” IEEE Journal on Selected Areas in Comm., vol. 24, pp – 1971, November “IEEE IEEE standard for local and metropolitan area networks – part 16: Air interface for broadband wireless access systems,” May A. Mahmood and E. S. Elmallah. Joint non-bifurcated routing and scheduling in wireless grid mesh networks. In Proceedings of 6th International Conference on Broadband Communications, Networks, and Systems (BROADNETS), September, A. Mahmood and E. S. Elmallah, “Incremental routing and scheduling in wireless grids.” To appear in GLOBECOM 2009.

Thank you