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Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network

Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network. Ashish Raniwala, Tzi-cker Chiueh Stony Brook University Infocom2005. Outline. Introduction Hyacinth Architecture Approach Load-balancing Routing Traffic-aware Channel Assignment Simulation

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Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network

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  1. Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network Ashish Raniwala, Tzi-cker Chiueh Stony Brook University Infocom2005

  2. Outline • Introduction • Hyacinth Architecture • Approach • Load-balancing Routing • Traffic-aware Channel Assignment • Simulation • Conclusions

  3. Introduction • Wireless Mesh Network (WMN) • Definition: A network of static routers inter-connected by wireless links. • Examples: Enterprise backbone network, campus network, ISP last-mile network

  4. Wireless Mesh Network Characteristics - • Wireless backbone • Single channel • Low capacity Applications - • Last-mile ISP connectivity • Wireless campus backbone Hyacinth Architecture Goal - • High-capacity wireless mesh network • Using Multiple channels • No MAC modifications (off-the-shelf hardware) 802.11 Deployment Characteristics- • Wireless last-hop (AP-to-Mobile) • Wired backbone Wires

  5. Introduction Capacity Issues • 802.11: MAC contention, PLCP header, ACK, bit errors • Ad-hoc: Single-channel across the network => Inter-path and Intra-path interference Increasing Capacity • Frequency: Multiple channels • Spatial: Directional antennas, Transmit power control

  6. Introduction • Channel Assignment • Channel assignment => Bandwidth of virtual links • Connectivity vs. radio spectrum utilization efficiency • Workload awareness Connectivity Optimal Capacity • Routing • Routing => Traffic load on virtual links and gateways • Network-wide load balance • Interaction between routing and channel assignment

  7. Internet ERP NFS Enterprise Resources Multi-channel Wireless Mesh Backbone (2 NICs/node) Standard 802.11 Access Network Hyacinth Architecture =>5-channel network

  8. Load-balancing Routing 30 20 40 10 30 10 40 50 20

  9. Load-balancing Routing • Gateway Discovery Protocol • Each node joins one (or more) gateways • Messages: ADVERTISE/JOIN/ACCEPT/LEAVE • Structure: Forest of trees rooted at gateway nodes. • Cache extra advertisements for failure recovery • Metrics • Hop-count • + stable because mostly static • - load-imbalance • Gateway residual capacity • + load balanced, adapts to traffic • - route flaps because dynamic • Path residual capacity • + handles non-gateway bottlenecks (1) (2) (3)

  10. Traffic-aware Channel Assignment 70 60 110 30 40 40 30 40 30 20

  11. Channel load imbalance 10 40 30 Channel load balanced 10 40 30 Traffic-aware Channel Assignment • Workload-Awareness • Why ? • Need to distribute load uniformly across channels. • How ? • 1. Periodically construct a neighborhood channel-usage map • 2. Re-assign channels to balance traffic load across channels • 3. Coordinate withdirectneighbors 10 40 30

  12. SOLUTION Traffic-aware Channel Assignment • Channel Dependency Issue • Each node has a limited number of interfaces. Hence each interface is used to communicate with multiple neighbors. E C D B A

  13. Simulation • 60 nodes with 4 gateway nodes • 2 or 3 NICs/node, 12 channels • 30 random flows to wired network

  14. Simulation

  15. Simulation

  16. Conclusions • IEEE 802.11 beyond AP—mobile communication • Multi-channel wireless mesh backbone • Multiple commodity cards per node • Workload-aware channel assignment • Load-balancing routing • Applicable to IEEE 802.16a • Ongoing Mesh Networking Research:- • Station-transparent mobility management • Secure routing protocol • Self-diagnosing and self-healing network management • Directional antenna: Spatial Diversity

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