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Presented By:
Mankiran Kaur
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Standardization Activities
Wireless Mesh Networks
The term 'wireless mesh networks' describes wireless networks in which each node can communicate directly with one or more peer nodes.
The term 'mesh' originally used to suggest that all nodes were connected to all other nodes, but most modern meshes connect only a sub-set of nodes to each other.
Still, this is quite different than traditional wireless networks, which require centralized access points to mediate the wireless connection.
It is dynamically self-organized and self-configured, nodes can automatically establishing and maintaining mesh connectivity among nodes
Wireless Mesh Networks
Nodes are comprised of mesh routers and mesh clients.
Extend the range and page link robustness of existing Wi-Fi’s by allowing mesh-style multi-hopping
A user finds a nearby user and hops through it - or possibly multiple users - to get to the destination
Every user becomes a relay point or router for network traffic
Mesh networks consist of multiple wireless devices equipped with COTS802.11 a/b/g cards that work in ad-hoc fashion.
802.11 capable antennas placed on rooftops allow a large area coverage
Network Architecture
WMNs consist of two types of nodes: Mesh Routers and Mesh Clients
Mesh router
Additional routing functions to support mesh networking.
Multiple wireless interfaces with same or different wireless access technologies.
The gateway/bridge functionalities enable the integration of WMNs with existing wireless networks(cellular, sensornet, Wi-Fi, WiMAX).
Mesh Clients
Conventional nodes (e.g., desktops, laptops, PDAs, PocketPCs, phones, etc.) equipped with wireless network interface cards (NICs), and can connect directly to wireless mesh routers.
Customers without wireless NICs can access WMNs by connecting to wireless mesh routers through, e.g., Ethernet.
WMN Routers
WMN Clients
WMN COMPONENTS
WMN Architecture Classifications
Infrastructure Meshing
Client Mesh Networking
Hybrid Mesh Networking
Infrastructure Meshing
Mesh routers form an mesh infrastructure among themselves.
Provides backbone for clients and enables integration of WMNs with existing wireless networks and Internet through gateway/bridge functionalities.
Clients connect to mesh router with wireless page link or Ethernet
Client WMNs
Client nodes constitute peer-to-peer network, and perform routing and configuration functionalities as well as provide end-user applications to customers, mesh routers are not required.
Multi-hop routing.
Client nodes have to perform additional functions such as routing and self-configuration
Hybrid WMNs
A combination of infrastructure and client meshing.
Infrastructure provides connectivity to other networks such as the Internet, Wi-Fi, WiMAX, cellular, and sensor networks;
Mesh clients can access the network through mesh routers as well as directly meshing with other mesh clients.
The routing capabilities of clients provide better connectivity and coverage
CHARACTERISTICS
Multi-hop Wireless Network
Support for Ad Hoc Networking, and Capability of Self-Forming, Self-Healing, and Self-Organization
Mobility Dependence on the Type of Mesh Nodes
Multiple Types of Network Access
Dependence of Power-Consumption Constraints on the
Type of Mesh Nodes
Compatibility and Interoperability with Existing
Wireless Networks
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.
Hence, the load on end-user devices is significantly decreased, which provides lower energy consumption and high-end application capabilities to possibly mobile and energy constrained end-users.
Moreover, the end-user requirements are limited which decreases the cost of devices that can be used in WMNs.
WMNs vs AD HOC Networks
Compatibility:
WMNs contain many differences when compared to ad hoc
networks.
Ad hoc networks can be considered as a subset of WMNs.
More specifically, the existing techniques developed for ad-hoc
networks are already applicable to WMNs.
As an example, through the use of mesh routers and routing-
capable end-users, multiple ad hoc networks can be supported
in WMNs, but with further integration of these networks.
Application Scenarios
Broadband Home Networking
Community and Neighborhood Networking
Enterprising Networking
Transportation Systems
Health and Medical Systems
Security and Surveillance Systems
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 survey 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.
Community and Neighborhood Networking
Community networks based on cable, DSL and last-hop wireless
All traffic must flow through Internet, this 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
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, but does not improve robustness to page link failures, network congestion and other problems of the entire enterprise network.
WMNs Solutions
Multiple backhaul access modems can be shared by all nodes in the entire network
Scalable
Transportation Systems
WMNs can extend access from stations and stops 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.
Health and Medical Systems
In a hospital or medical center, monitoring and diagnosis data need to be processed and transmitted from one room to another for various purposes.
Data transmission is usually broadband, since high resolution medical images and
various periodical monitoring information can easily produce a constant and large
volume of data.
Traditional wired networks can only provide limited network access to certain
fixed medical devices.
Wi-Fi based networks must rely on the existence of Ethernet connections, which
may cause high system cost and complexity but without the abilities to eliminate
dead spots.
However, these issues do not exist in WMNs.
Security Surveillance Systems
As security is turning out to be a very high concern, security surveillance systems become a necessity for enterprise buildings, shopping malls, grocery stores, etc.
In order to deploy such systems at locations as needed, WMNs are a much more viable solution than wired networks
to connect all devices.
Since still images and videos are the major traffic flowing in the network, this application demands much higher network capacity
than other applications
Routing Protocols
Routing Protocols used in wireless mesh network can be classified into two main categories:
Proactive or table driven routing protocols.
Destination-Sequenced Distance Vector Routing Protocol.
Optimized Link State Routing.
Reactive or on-demand routing protocols
Dynamic Source Routing Protocol.
Ad hoc On-Demand Distance Vector Routing Protocol.
Destination-Sequenced Distance Vector
DSDV is a proactive table-driven routing protocol based on the classical Bellman-Ford algorithm. A routing table is maintained in every mobile node in the network.
The routing table records all of the possible destinations within the network and the number of hops to each destination.
In DSDV, each route is tagged with a sequence number, indicating how old the route is.
Optimized Link State Routing
OLSR is a proactive link-state routing protocol which uses Hello and Topology Control (TC) messages to discover and then disseminate page link state information throughout the mobile ad-hoc network.
Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths.
Dynamic Source Routing Protocol
DSR is a reactive (On demand) source routing protocol. The protocol consists of two major phases: route discovery and route maintenance.
Route Discovery process is based on flooding the network with route request (RREQ) packets.
Destination replies to the RREQ with a route reply (RREP) packet that is routed back to the original source.
Ad hoc On-Demand Distance Vector
AODV has two important phases, route discovery and route maintenance. It combines DSR and DSDV mechanisms for routing.
AODV minimizes the number of required broadcasts, making it suitable for large MANETs
Working Environment
Ad-hoc Network : A ad-hoc network is a decentralized wireless network
In Ad-hoc network each node participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity.
Security
WMNs lack efficient and scalable security solutions
Distributed network architecture
Vulnerability of channels and nodes in the shared wireless medium
Dynamic change of network topology.
Two strategies
Embedding security mechanism into network protocols
Developing security monitoring response systems
How to design and implement a practical security system, including cross-layer secure network protocols and various intrusion detection algorithms, is a challenging research topic.
Security
For a security monitoring system, a cross-layer framework also needs to be developed.
However, AAA is performed through a centralized server
such as RADIUS (remote authentication dial-in user service).
Such a centralized scheme is not applicable in WMNs.
Moreover, security key management in WMNs is much more difficult
thanin wireless LANs, because there is no central authority,
trusted third party or server to manage security keys.
Key management in WMNs need to be performed in a distributed but
secure way.
Therefore, a distributed authentication and authorization
scheme with secure key management needs to be proposed for
WMNs.
