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 Introduction Hyacinth Architecture Hyacinth Architecture Approach Approach Load-balancing Routing Load-balancing Routing Traffic-aware Channel Assignment Traffic-aware Channel Assignment Simulation Simulation Conclusions Conclusions

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

4. 802.11 Deployment Characteristics- Wireless last-hop (AP-to-Mobile) Wired backbone 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) Wires

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

6. Introduction Channel Assignment Channel Assignment Channel assignment => Bandwidth of virtual links Channel assignment => Bandwidth of virtual links Connectivity vs. radio spectrum utilization efficiency Connectivity vs. radio spectrum utilization efficiency Workload awareness 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. Hyacinth Architecture InternetNFSERP Standard 802.11 Access Network Multi-channel Wireless Mesh Backbone (2 NICs/node) Enterprise Resources =>5-channel network

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

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 1.Hop-count + stable because mostly static - load-imbalance 2.Gateway residual capacity + load balanced, adapts to traffic - route flaps because dynamic 3.Path residual capacity + handles non-gateway bottlenecks (1) (2) (3)

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

11. Traffic-aware Channel Assignment Workload-Awareness Workload-Awareness Why ? Why ? Need to distribute load uniformly across channels. Need to distribute load uniformly across channels. How ? How ? 1. Periodically construct a neighborhood channel-usage map 1. Periodically construct a neighborhood channel-usage map 2. Re-assign channels to balance traffic load across channels 2. Re-assign channels to balance traffic load across channels 3. Coordinate with direct neighbors 3. Coordinate with direct neighbors 104030 104030 Channel load imbalance 104030 Channel load balanced

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

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