Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

111/10/2010

Architecture and Algorithms for an

IEEE 802.11-Based Multi-Channel

Wireless Mesh Network

Ramon Kahane

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

211/10/2010

Content

• Introduction

• System Architecture

• Problems

• Solutions

• Evaluation

• Conclusion

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

311/10/2010

Introduction

• Most IEEE 802.11-based multi-hop ad hoc networks use only a single channel

o Not used as wireless last-mile access network

o Or wireless enterprise backbone network

• Hyacinth: WMN using multiple NICs on each node

• Central design issues: channel assignment and routing

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

411/10/2010

Introduction

• Intelligent channel assignment is critical

o Distributed algorithms

o Centralized algorithms

• Even 2 NICs on each node lead to a

throughput improvement of the factor 6 to 7

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

511/10/2010

System Architecture

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

611/10/2010

Channel Assignment Problem

• Bind each NIC to a channel

• Neighbor-to-interface binding

• Interface-to-channel binding

• 4 main constraintso Number of distinct channels � number of NICs

o Two nodes communicating directly share one common channel

o Raw capacity of channel is limited

o Number of non-overlapped channels is fixed

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

711/10/2010

Load-Balance Routing Problem

• Links should use radio channels that are not

used so often

• Most WMN nodes communicate with wired

network (internet, enterprise servers)

• Helps to avoid bottleneck links

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

811/10/2010

Evaluation Metric

• Maximize overall network goodput

• � = ∑ min(∑ (, � ) , �())�

o Device

o Gateway node �

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

911/10/2010

Load-Balancing Routing Algorithm

• Each wired gateway is the root of a spanning

tree

• The spanning trees are connected through the

wired network

• Each node is associated with only one tree

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1011/10/2010

Load-Balancing Routing Algorithm

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1111/10/2010

Routing Tree Construction

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1211/10/2010

Routing Metrics

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1311/10/2010

Neighbor-Interface Binding

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1411/10/2010

Elimination of Channel Dependency

Problem

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1511/10/2010

Channel Assignment Algorithm

• Estimate usage status to assign channels to

the DOWN-NICs

o Periodically exchange of channel usage

information with each node in the interference

range

• Nodes higher up in the tree need more

bandwidth

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1611/10/2010

Virtual Control Network

• Simple Option: Using a CONTROL-NIC

• To save the additional hardware interface: Use

a virtual Control Network

o Scan all channels for broadcasting HELLO

messages during neighborhood discovery phase

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1711/10/2010

Failure Recovery

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1811/10/2010

Evaluation

• 2 NICs per node

• 12 channels (IEEE 802.11a)

• Channel Load Balancing = 1 minute

• 10 scenarios with 60 nodes on 9x9 square grid

network

• Random traffic = 0-3 Mbps

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

1911/10/2010

Goodput improvement

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2011/10/2010

HTTP Response Time

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2111/10/2010

Different number of NICs per node

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2211/10/2010

Number of gateway nodes

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2311/10/2010

Placement of gateway nodes

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2411/10/2010

Failure Recovery Time

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2511/10/2010

Conclusion

• Bandwidth problem more serious for multi-

hop WMNs

• Single-channel WMNs cannot adequately

support the bandwidth

• Channel assignment

• Load balance routing

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2611/10/2010

Future work

• Nodes in the trees are associated to more

than one tree

Architecture and Algorithms for an IEEE 802.11-Based

Multi-Channel Wireless Mesh Network

Ramon Kahane

2711/10/2010

QUESTIONS?

Thank you!