WIRELESS MESH NETWORKSWIRELESS MESH NETWORKS

Ian F. AKYILDIZ* and Xudong WANG**Ian F. AKYILDIZ* and Xudong WANG**

* Georgia Institute of Technology* Georgia Institute of Technology BWN (Broadband Wireless Networking) Lab BWN (Broadband Wireless Networking) Lab

** TeraNovi Tachnologies** TeraNovi Tachnologies

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1. INTRODUCTION1. INTRODUCTION

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WIRELESS NETWORKSWIRELESS NETWORKSWirelessNetworking

Multi-hop

Infrastructure-less(Ad Hoc) Hybrid Infrastructure-less

(MANETs)

SingleHop

CellularNetworks Wireless Sensor

NetworksWIRELESS MESH

NETWORKSVANETs

Infrastructure-based(APs)

802.11 802.16 Bluetooth802.11

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WMNs consist of two types of nodes: Mesh Routers and Mesh Clients

A wireless mesh router contains additional routing functions

to support mesh networking

Same coverage as a conventional router but with much lower

transmission power through multi-hop communication

ARCHITECTURE of WMNsARCHITECTURE of WMNs

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Mesh Routers

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Zigbee Mesh Router @ BWN Lab

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Mesh RoutersMesh Routers

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Mesh RoutersMesh Routers

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MESH CLIENTS

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Network Architecture ClassificationNetwork Architecture Classification

1. INFRASTRUCTURE MESHING1. INFRASTRUCTURE MESHING

2. CLIENT MESHING2. CLIENT MESHING

3. HYBRID MESHING3. HYBRID MESHING

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INFRASTRUCTURE MESHINGINFRASTRUCTURE MESHING

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CLIENT MESHINGCLIENT MESHING

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HYBRID MESHING

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IEEE 802.11 Based Mesh NetworkIEEE 802.11 Based Mesh Network

Wired Network

G1G2

R1

R2

R3

A1 A2 A3

Ri Mesh Point (MP)Gi Mesh Point Portal (MPP)Ai Mesh Access Point (MAP)

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CHARACTERISTICS (Required)CHARACTERISTICS (Required)

Multi-hop Wireless NetworkMulti-hop Wireless Network

Support for Ad Hoc NetworkingSupport for Ad Hoc Networking

Capability of Self-Forming, Self-Healing, and Self-Capability of Self-Forming, Self-Healing, and Self- OrganizationOrganization

Compatible and Interoperable with Existing Wireless Compatible and Interoperable with Existing Wireless NetworksNetworks

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CHARACTERISTICS (Typical)CHARACTERISTICS (Typical)

Multiple radios and multiple channel systemsMultiple radios and multiple channel systems

Advanced radio techniques: Advanced radio techniques: Directional and smart antennas, MIMO system, Directional and smart antennas, MIMO system, reconfigurable radios, frequency reconfigurable radios, frequency agile/cognitive agile/cognitive

radios, software radiosradios, software radios

Multiple Types of Network Access Multiple Types of Network Access (WiMAX, WiFis)(WiMAX, WiFis)

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WMNs vs Ad Hoc NetworksWMNs vs Ad Hoc Networks

Dedicated Routing and Configuration:

In ad-hoc networks, end-user devices also perform routing and In ad-hoc networks, end-user devices also perform routing and configuration functionalities for all other nodes. configuration functionalities for all other nodes.

However, WMNs contain However, WMNs contain mesh routersmesh routers for these functionalities. for these functionalities. the load on end-user devices is significantly decreased, the load on end-user devices is significantly decreased, lower energy consumption and high-end application lower energy consumption and high-end application capabilities capabilities

End-user requirements are limited End-user requirements are limited decreases the cost of devices in WMNs decreases the cost of devices in WMNs

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WMNs vs Ad Hoc NetworksWMNs vs Ad Hoc Networks

Multiple Radios: * Multiple radios perform routing and access functionalities

* Example:One radio routing between mesh routersAnother radio access to the network from end-users

significantly improves the capacity of the network

* These functionalities are performed in the same channel in ad-hoc networks performance affected !

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WMNs vs Ad Hoc NetworksWMNs vs Ad Hoc Networks

Mobility: Mobility: (in ad hoc networks)(in ad hoc networks)

Routing is realized by end-user devices Routing is realized by end-user devices

the network topology and connectivity depend on the movement the network topology and connectivity depend on the movement of users of users

Additional challenges on Additional challenges on * routing protocols * routing protocols * network configuration and * network configuration and * deployment* deployment

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WMNs vs Ad Hoc NetworksWMNs vs Ad Hoc Networks

Mobility: Mobility: (in WMNs)(in WMNs)

Since mesh routers provide the infrastructure, theSince mesh routers provide the infrastructure, the

coverage can be engineered easily. coverage can be engineered easily.

While providing continuous connectivity throughout While providing continuous connectivity throughout the the

network, the mobility of end-users is still network, the mobility of end-users is still supported, supported,

without compromising the performance of the network.without compromising the performance of the network.

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WMNs vs Ad-Hoc NetworksWMNs vs Ad-Hoc Networks

MultihopMultihop

Nodes are wireless, Nodes are wireless, possibly mobilepossibly mobile

May rely on infrastructureMay rely on infrastructure

Most traffic is userMost traffic is useruseruser

Ad-Hoc Networks Wireless Mesh Networks

MultihopMultihop

Nodes are wireless, Nodes are wireless,

some mobile, some fixedsome mobile, some fixed

It relies on infrastructureIt relies on infrastructure

Most traffic is Most traffic is userusergatewaygateway

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WMNs vs WIRELESS SENSOR NETWORKSWMNs vs WIRELESS SENSOR NETWORKS

Bandwidth is limited Bandwidth is limited (tens of kbps)(tens of kbps)

In most applications, fixed In most applications, fixed nodesnodes

Energy constraintsEnergy constraints

Resource constraintsResource constraints

Most traffic is user-to-gatewayMost traffic is user-to-gateway

Wireless Sensor Networks Wireless Mesh Networks

Bandwidth is high Bandwidth is high (>1Mbps)(>1Mbps)

Some nodes mobile, some fixedSome nodes mobile, some fixed

Not energy limitedNot energy limited

Resources are not an issueResources are not an issue

Most traffic is user-to-Most traffic is user-to-gatewaygateway

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* Low up-front costs

* Easy incremental deployment

* Easy maintenance

* Provide NLOS coverage

* Wireless AP backbone provides connectivity and robustness which is not always achieved with selfish and roaming users in ad-hoc networks

* Take load off of end-users

* Stationary APs provide consistent coverage

ADVANTAGES OF WIRELESS MESH NETWORKSADVANTAGES OF WIRELESS MESH NETWORKS

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Applications: Applications: Broadband Home NetworkingBroadband Home Networking

Current home network realized through IEEE 802.11 WLANsCurrent home network realized through IEEE 802.11 WLANs

– Problem Problem location of the access points location of the access points

– Homes have many dead zones without service coverageHomes have many dead zones without service coverage

– Site surveys are expensive and not practical Site surveys are expensive and not practical

– Installation of multiple access points is also expensive and not convenientInstallation of multiple access points is also expensive and not convenient

– Communications between nodes under two different access points have to go through the access Communications between nodes under two different access points have to go through the access hub, not an efficient solutionhub, not an efficient solution

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Applications: Applications: Broadband Home NetworkingBroadband Home Networking

WMN is the SOLUTION!

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Applications: Applications: Community and Neighborhood NetworkingCommunity and Neighborhood Networking

Community networks based on cable, DSL and last-hop wirelessCommunity networks based on cable, DSL and last-hop wireless

All traffic must flow through Internet All traffic must flow through Internet significantly significantly reduces reduces

network resource utilization. network resource utilization.

Large percentage of areas in between houses is not Large percentage of areas in between houses is not covered by wireless servicescovered by wireless services

Gateways may not be shared and wireless services must be Gateways may not be shared and wireless services must be set up individually, network service costs may increaseset up individually, network service costs may increase

Each home has single path to access InternetEach home has single path to access Internet

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Applications: Applications: Community and Neighborhood NetworkingCommunity and Neighborhood Networking

WMNs can mitigate these disadvantages and provide many applications such as distributed file storage, distributed file access, and video streaming.

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Applications:Applications: Enterprise Networking Enterprise Networking

IEEE 802.11 WLANs IEEE 802.11 WLANs

– Isolated islands, connections among them are Isolated islands, connections among them are achieved through wired Ethernet achieved through wired Ethernet

– Adding more backhaul access modems only Adding more backhaul access modems only increases capacity locallyincreases capacity locally

– Does not improve robustness to link failures, Does not improve robustness to link failures, network congestion and other problemsnetwork congestion and other problems

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Applications:Applications: Enterprise Enterprise NetworkingNetworking

WMNs SolutionsWMNs Solutions– Multiple backhaul access modems can be shared by all nodes in the Multiple backhaul access modems can be shared by all nodes in the

entire network entire network – ScalableScalable

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Applications:Applications: Metropolitan Area Networks Metropolitan Area Networks

WMNs provide higher transmission rate than cellular networksWMNs provide higher transmission rate than cellular networks

Communication between nodes does not rely on a wired backboneCommunication between nodes does not rely on a wired backbone An economic alternative to broadband networkingAn economic alternative to broadband networking

Covers larger area than home, enterprise, building, or Covers larger area than home, enterprise, building, or community networkscommunity networks

Higher scalabilityHigher scalability

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Applications:Applications: Metropolitan Area Networks Metropolitan Area Networks

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Applications:Applications: Transportation Systems Transportation Systems

WMNs can extend access from stations into WMNs can extend access from stations into buses, ferries, and trains.buses, ferries, and trains.

Convenient passenger information services, remote Convenient passenger information services, remote monitoring of in-vehicle security video, and driver monitoring of in-vehicle security video, and driver communications.communications.

Two key techniques are neededTwo key techniques are needed– High-speed mobile backhaul from a vehicle to the High-speed mobile backhaul from a vehicle to the Internet Internet

– Mobile mesh networks within the vehicle.Mobile mesh networks within the vehicle.

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Applications:Applications: Transportation Systems Transportation Systems

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Applications:Applications: Building Automation Building Automation

Various electrical devices need to be controlled and Various electrical devices need to be controlled and monitored. monitored.

Standard wired networks is very expensiveStandard wired networks is very expensive

Wi-Fi networks can reduce the cost of such networksWi-Fi networks can reduce the cost of such networks

However, Wi-Fis are still expensiveHowever, Wi-Fis are still expensive

Low deployment cost of BACnet (Building Automation and Low deployment cost of BACnet (Building Automation and Control Networks) with WMNsControl Networks) with WMNs

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Applications:Applications: Building Automation Building Automation

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Application:Application: Broadband Internet Access Broadband Internet Access

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Qualitative Comparisons for Broadband Internet Qualitative Comparisons for Broadband Internet AccessAccess

CableDSL

WMAN(802.16)

Cellular(2.5-3G)

WMNs

Bandwidth VeryGood

VeryGood

Limited Good

Upfront Investments

VeryHigh

High High Low

Total Investments

VeryHigh

High High Moderate

Market Coverage Good Good GoodModest

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Mobile Internet AccessMobile Internet Access

Direct competition with 3G cellular Direct competition with 3G cellular systemssystems

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Qualitative Comparisons for Mobile Internet Qualitative Comparisons for Mobile Internet AccessAccess

Cellular 3G WMNs

UpfrontInvestments

LowHigh

Geo-location Limited Good

Bandwidth GoodLimited

UpgradeCost

LowHigh

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Applications:Applications: Health and Medical Health and Medical SystemsSystems

Monitoring and diagnosis data need to be processed and Monitoring and diagnosis data need to be processed and transmitted across rooms for various purposestransmitted across rooms for various purposes

Large data volume by high resolution medical images, Large data volume by high resolution medical images, various periodical monitoring informationvarious periodical monitoring information

Wi-Fi based networks must rely on the existence of Wi-Fi based networks must rely on the existence of Ethernet connections, cause high system cost, Ethernet connections, cause high system cost, complexity and dead spotscomplexity and dead spots

However, these issues do not exist in WMNsHowever, these issues do not exist in WMNs

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Applications:Applications: Security and Surveillance Security and Surveillance SystemsSystems

Security surveillance systems are necessary for Security surveillance systems are necessary for enterprise buildings, shopping malls, grocery enterprise buildings, shopping malls, grocery stores, etc. stores, etc.

Still images and videos are the major traffic Still images and videos are the major traffic flowing in the networkflowing in the network

They demand much higher network capacity than They demand much higher network capacity than other applicationsother applications

WMNs are a good solution for these applicationsWMNs are a good solution for these applications

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More ApplicationsMore Applications

Disaster Relief and Emergency Networks

P2P Networking

43Project No.04-157: Communications Infrastructure for Electric System Automation

ANOTHER APPLICATION:Hybrid Network Architecture for Electrical System Automation

–Wireless Automatic Meter Reading (WAMR):

Energy consumption statistics

Effective billing management

Remote activation and deactivation of the customer services

44Project No.04-157: Communications Infrastructure for Electric System Automation

ANOTHER APPLICATION:Hybrid Network Architecture for Electrical System Automation

–Electric System Monitoring:Electric System Monitoring:

Equipment (e.g., distribution transformer, feeder, recloser/sectionalizer, capacitor, etc.) monitoring

Fast identification of service interruptions and incipient faults

Timely restoration of the electric utility services

45Project No.04-157: Communications Infrastructure for Electric System Automation

ANOTHER APPLICATION:Hybrid Network Architecture for Electrical System Automation

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Applications:Applications: Layer 2 Connectivity Layer 2 Connectivity

The entire wireless mesh cloud The entire wireless mesh cloud becomes one (giant) Ethernet becomes one (giant) Ethernet switchswitch

Simple, fast installationSimple, fast installation– Short-term events Short-term events (e.g., (e.g., conferences, conventions, shows)conferences, conventions, shows)

– Where wires are not desired Where wires are not desired (e.g., hotels, airports)(e.g., hotels, airports)

– Where wires are impossible Where wires are impossible (e.g., historic buildings)(e.g., historic buildings)

Internet Internet

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Qualitative Comparisons Layer 2 Qualitative Comparisons Layer 2 ConnectivityConnectivity

Ethernet WMN

Total Cost Moderate Low-Moderate

Mobile Users 802.11 needed support

Bandwidth GoodVeryGood

Speed/Ease of Deployment

Fast/EasySlow/Difficult

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Critical Factors influencing Network PerformanceCritical Factors influencing Network Performance

1. Advanced Radio Techniques1. Advanced Radio Techniques Typical Examples:Typical Examples:

* Directional and smart antennas* Directional and smart antennas * MIMO systems * MIMO systems (Key Technology for IEEE 802.11n) (Key Technology for IEEE 802.11n) * Multi-radio/multi-channel systems* Multi-radio/multi-channel systems * Reconfigurable radios* Reconfigurable radiosMore Advanced Technologies (not mature yet for commercialization)More Advanced Technologies (not mature yet for commercialization)::

* Frequency agile/cognitive radios and * Frequency agile/cognitive radios and * Software radios* Software radios

These advanced radio technologies require revolutionary design in These advanced radio technologies require revolutionary design in higher layer protocols, in particular, MAC and routing.higher layer protocols, in particular, MAC and routing.

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2. Scalability (NW performance degrades with increasing NW size)

e.g., throughput degrades with the number of hops. Max.

available bandwidth degrades at the rate of 1/2,1/4,1/8

depending on the number of hops; 4 hops away from the

sender the max BW becomes 1/16 of the total available BW.

Critical Factors Influencing Network PerformanceCritical Factors Influencing Network Performance

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3. Mesh Connectivity (for protocol design)

4. Broadband and QoS

(end-to-end delay, fairness, delay, jitter, aggregate and per-node throughput, packet loss ratios)

5. Compatibility and Inter-Operability (for mesh and conventional clients; mesh routers must be capable for inter-operation)

Critical Factors Influencing Network Critical Factors Influencing Network PerformancePerformance

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6. Security (new encryption algorithms, key distribution, secure MAC and

routing protocols, intrusion detection, monitoring)

7. Ease of Use (autonomic network, automatic power management, self

organization, dynamic topology control, robust to link failures,

fast network subscription/user authentication procedure)

Critical Factors Influencing Network Critical Factors Influencing Network PerformancePerformance