Download wireless mesh networks

WIRELESS MESH NETWORKS
Ian F. AKYILDIZ* and Xudong WANG**
* Georgia Institute of Technology
BWN (Broadband Wireless Networking) Lab
** TeraNovi Tachnologies
1. INTRODUCTION
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WIRELESS NETWORKS
Wireless
Networking
Single
Hop
Infrastructure-based
(APs)
802.11
802.16
Cellular
Networks
Multi-hop
Infrastructure-less
(Ad Hoc)
802.11
Hybrid
Infrastructure-less
(MANETs)
Bluetooth
Wireless Sensor
Networks
WIRELESS MESH
NETWORKS
VANETs
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ARCHITECTURE of WMNs
 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
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Mesh Routers
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Zigbee Mesh Router @ BWN Lab
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Mesh Routers
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Mesh Routers
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MESH CLIENTS
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Network Architecture Classification
1. INFRASTRUCTURE MESHING
2. CLIENT MESHING
3. HYBRID MESHING
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INFRASTRUCTURE MESHING
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CLIENT MESHING
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HYBRID MESHING
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IEEE 802.11 Based Mesh Network
Wired Network
G2
G1
R2
R1
Ri
Gi
Ai
Mesh Point (MP)
Mesh Point Portal (MPP)
Mesh Access Point (MAP)
R3
A1
A2
A3
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CHARACTERISTICS (Required)
 Multi-hop Wireless Network
 Support for Ad Hoc Networking
 Capability of Self-Forming, Self-Healing, and SelfOrganization
 Compatible and Interoperable with Existing Wireless
Networks
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CHARACTERISTICS (Typical)
 Multiple radios and multiple channel systems
Advanced radio techniques:
Directional and smart antennas, MIMO system,
reconfigurable radios, frequency agile/cognitive
radios, software radios
Multiple Types of Network Access (WiMAX, WiFis)
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WMNs vs Ad Hoc Networks
Dedicated Routing and Configuration:
 In ad-hoc networks, end-user devices also perform routing and
configuration functionalities for all other nodes.
 However, WMNs contain mesh routers for these functionalities.
 the load on end-user devices is significantly decreased,
 lower energy consumption and high-end application capabilities
 End-user requirements are limited  decreases the cost of devices in WMNs
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WMNs vs Ad Hoc Networks
Multiple Radios:
* Multiple radios perform routing and access functionalities
* Example:
One radio  routing between mesh routers
Another 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 Networks
Mobility:
(in ad hoc networks)
 Routing is realized by end-user devices
 the network topology and connectivity depend on the movement of users
 Additional challenges on
* routing protocols
* network configuration and
* deployment
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WMNs vs Ad Hoc Networks
Mobility:
(in WMNs)
 Since mesh routers provide the infrastructure, the
coverage can be engineered easily.
 While providing continuous connectivity throughout the
network, the mobility of end-users is still supported,
without compromising the performance of the network.
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WMNs vs Ad-Hoc Networks
Ad-Hoc Networks
Wireless Mesh Networks
 Multihop
 Multihop
 Nodes are wireless,
possibly mobile
 Nodes are wireless,
some mobile, some fixed
 May rely on infrastructure
 It relies on infrastructure
 Most traffic is useruser
 Most traffic is usergateway
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WMNs vs WIRELESS SENSOR NETWORKS
Wireless Sensor Networks
 Bandwidth is limited
(tens of kbps)
Wireless Mesh Networks
 Bandwidth is high
(>1Mbps)
 In most applications, fixed nodes
 Some nodes mobile, some fixed
 Energy constraints
 Not energy limited
 Resource constraints
 Resources are not an issue
 Most traffic is user-to-gateway
 Most traffic is user-to-gateway
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ADVANTAGES OF WIRELESS MESH NETWORKS
* 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
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Applications: Broadband Home Networking
 Current home network realized through IEEE 802.11 WLANs
– Problem  location of the access points
– Homes have many dead zones without service coverage
– Site surveys are expensive and not practical
– Installation of multiple access points is also expensive and not
convenient
– Communications between nodes under two different access points
have to go through the access hub, not an efficient solution
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Applications: Broadband Home Networking
WMN is the SOLUTION!
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Applications: Community and Neighborhood Networking
Community networks based on cable, DSL and last-hop wireless
 All traffic must flow through Internet  significantly reduces
network resource utilization.
 Large percentage of areas in between houses is not covered by
wireless services
 Gateways may not be shared and wireless services must be set up
individually, network service costs may increase
 Each home has single path to access Internet
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Applications: Community 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: Enterprise Networking
IEEE 802.11 WLANs
– Isolated islands, connections among them are achieved
through wired Ethernet
– Adding more backhaul access modems only increases
capacity locally
– Does not improve robustness to link failures, network
congestion and other problems
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Applications: Enterprise Networking
 WMNs Solutions
– Multiple backhaul access modems can be shared by all nodes in the entire network
– Scalable
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Applications: Metropolitan Area Networks
 WMNs provide higher transmission rate than cellular networks
 Communication between nodes does not rely on a wired backbone
 An economic alternative to broadband networking
 Covers larger area than home, enterprise, building, or community
networks
 Higher scalability
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Applications: Metropolitan Area Networks
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Applications: Transportation Systems
 WMNs can extend access from stations into
buses, ferries, and trains.
 Convenient passenger information services, remote
monitoring of in-vehicle security video, and driver communications.
 Two key techniques are needed
– High-speed mobile backhaul from a vehicle to the Internet
– Mobile mesh networks within the vehicle.
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Applications: Transportation Systems
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Applications: Building Automation
 Various electrical devices need to be controlled and monitored.
 Standard wired networks is very expensive
 Wi-Fi networks can reduce the cost of such networks
 However, Wi-Fis are still expensive
 Low deployment cost of BACnet (Building Automation and Control
Networks) with WMNs
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Applications: Building Automation
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Application: Broadband Internet Access
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Qualitative Comparisons for Broadband Internet Access
Cellular
(2.5-3G)
Cable
DSL
WMAN
(802.16)
Bandwidth
Very
Good
Very
Good
Limited
Upfront
Investments
Total
Investments
Very
High
High
High
Low
Very
High
High
High
Moderate
Market Coverage
Good
Good
Good
Modest
WMNs
Good
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Mobile Internet Access
Direct competition with 3G cellular systems
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Qualitative Comparisons for Mobile Internet Access
Cellular 3G
WMNs
Upfront
Investments
High
Low
Bandwidth
Limited
Good
Geo-location
Limited
Good
Upgrade
Cost
High
Low
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Applications: Health and Medical Systems
 Monitoring and diagnosis data need to be processed and
transmitted across rooms for various purposes
 Large data volume by high resolution medical images, various
periodical monitoring information
 Wi-Fi based networks must rely on the existence of Ethernet
connections, cause high system cost, complexity and dead spots
 However, these issues do not exist in WMNs
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Applications: Security and Surveillance Systems
 Security surveillance systems are necessary for enterprise
buildings, shopping malls, grocery stores, etc.
 Still images and videos are the major traffic flowing in
the network
 They demand much higher network capacity than other
applications
 WMNs are a good solution for these applications
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More Applications
 Disaster Relief and Emergency Networks
 P2P Networking
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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
Project No.04-157: Communications Infrastructure for Electric System Automation
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ANOTHER APPLICATION:
Hybrid Network Architecture for Electrical System Automation
– 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
Project No.04-157: Communications Infrastructure for Electric System Automation
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ANOTHER APPLICATION:
Hybrid Network Architecture for Electrical System Automation
Project No.04-157: Communications Infrastructure for Electric System Automation
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Applications: Layer 2 Connectivity
 The entire wireless mesh cloud
becomes one (giant) Ethernet switch
 Simple, fast installation
– Short-term events (e.g.,
conferences, conventions, shows)
– Where wires are not desired
(e.g., hotels, airports)
– Where wires are impossible (e.g.,
historic buildings)
Internet
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Qualitative Comparisons Layer 2 Connectivity
Ethernet
WMN
Slow/Difficult
Fast/Easy
Bandwidth
Very
Good
Good
Mobile Users
802.11 needed
support
Total Cost
Moderate
Speed/Ease of
Deployment
Low-Moderate
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Critical Factors influencing Network Performance
1. Advanced Radio Techniques
Typical Examples:
* Directional and smart antennas
* MIMO systems  (Key Technology for IEEE 802.11n)
* Multi-radio/multi-channel systems
* Reconfigurable radios
More Advanced Technologies (not mature yet for commercialization):
* Frequency agile/cognitive radios and
* Software radios
These advanced radio technologies require revolutionary design in
higher layer protocols, in particular, MAC and routing.
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Critical Factors Influencing Network Performance
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.
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Critical Factors Influencing Network Performance
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)
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Critical Factors Influencing Network Performance
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)
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