Architecture and Algorithms for an IEEE 802.11-based Multi-channel Wireless Mesh Network
Ashish Raniwala, Tzi-cker ChiuehStony Brook University
Infocom2005
OutlineOutline
IntroductionIntroduction Hyacinth ArchitectureHyacinth Architecture ApproachApproach
Load-balancing RoutingLoad-balancing Routing Traffic-aware Channel AssignmentTraffic-aware Channel Assignment
SimulationSimulation ConclusionsConclusions
IntroductionIntroduction
Wireless Mesh Network (WMN)Wireless Mesh Network (WMN) Definition:Definition: A network of static routers inter- A network of static routers inter-
connected by wireless links.connected by wireless links. Examples:Examples: Enterprise backbone network, campus Enterprise backbone network, campus
network, ISP last-mile networknetwork, ISP last-mile network
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
IntroductionIntroduction
Capacity IssuesCapacity Issues 802.11: MAC contention, PLCP header, ACK, bit 802.11: MAC contention, PLCP header, ACK, bit
errorserrors Ad-hoc: Single-channel across the networkAd-hoc: Single-channel across the network
=> Inter-path and Intra-path interference=> Inter-path and Intra-path interference
Increasing CapacityIncreasing Capacity Frequency: Multiple channelsFrequency: Multiple channels Spatial: Directional antennas, Transmit power Spatial: Directional antennas, Transmit power
controlcontrol
IntroductionIntroduction
Channel AssignmentChannel Assignment Channel assignment => Bandwidth of Channel assignment => Bandwidth of
virtual linksvirtual links Connectivity vs. radio spectrum utilization Connectivity vs. radio spectrum utilization
efficiencyefficiency Workload awarenessWorkload awareness
Connectivity Optimal Capacity Routing
Routing => Traffic load on virtual links and gateways Network-wide load balance Interaction between routing and channel assignment
Hyacinth ArchitectureHyacinth Architecture
Internet NFSERP
Standard 802.11Access Network
Multi-channel Wireless Mesh Backbone (2 NICs/node)
Enterprise Resources
=>5-channel network
Load-balancing RoutingLoad-balancing Routing
4030
50
2030
10
20
40
10
Load-balancing RoutingLoad-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
• Metrics1. 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)
Traffic-aware Channel AssignmentTraffic-aware Channel Assignment
110
4030
30
20
60 70
4040 30
Traffic-aware Channel AssignmentTraffic-aware Channel Assignment Workload-AwarenessWorkload-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-1. Periodically construct a neighborhood channel-
usage mapusage map 2. Re-assign channels to balance traffic load across 2. Re-assign channels to balance traffic load across
channelschannels 3. Coordinate with3. Coordinate with directdirect neighborsneighbors
10 40 30
10 40 30 Channel loadimbalance
10 40 30Channel loadbalanced
Traffic-aware Channel AssignmentTraffic-aware Channel Assignment Channel Dependency IssueChannel Dependency Issue
Each node has a limited number of Each node has a limited number of interfaces. Hence each interface is interfaces. Hence each interface is used to communicate with multiple used to communicate with multiple neighbors.neighbors.
SOLUTION
A
B
CD
E
SimulationSimulation
60 nodes with 4 gateway nodes 2 or 3 NICs/node, 12 channels 30 random flows to wired network
SimulationSimulation
SimulationSimulation
ConclusionsConclusions IEEE 802.11 beyond AP—mobile communicationIEEE 802.11 beyond AP—mobile communication Multi-channel wireless mesh backboneMulti-channel wireless mesh backbone
Multiple commodity cards per nodeMultiple commodity cards per node Workload-aware channel assignmentWorkload-aware channel assignment Load-balancing routingLoad-balancing routing
Applicable to IEEE 802.16aApplicable to IEEE 802.16a Ongoing Mesh Networking Research:-Ongoing Mesh Networking Research:-
Station-transparent mobility managementStation-transparent mobility management Secure routing protocol Secure routing protocol Self-diagnosing and self-healing network managementSelf-diagnosing and self-healing network management Directional antenna: Spatial DiversityDirectional antenna: Spatial Diversity