This document provides an overview of wireless mesh networks (WMNs). It discusses the types of nodes in WMNs including wireless mesh routers and mesh clients. It describes the different architectures of WMNs and characteristics such as low cost, integration capabilities, and applications like broadband networking. Key challenges are also addressed around developing high-capacity radio interfaces and resource management. The document serves as an introduction to WMNs covering topics from architecture and standards to research opportunities.

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Seminar
On
Wireless Mesh
Networks

2. Content
 Introduction
 Types of nodes in WMNs
 WMN Architecture
 Characteristics of WMNs
 Applications
 Standard
 Advantages of Mesh Networks
 Key Research Challenges
 Conclusion
 References

3. Introduction
 WMNs offer multiple redundant communications paths
throughout the network. Whenever a link fails, the network
automatically routes messages through alternate paths.
 Even in adverse conditions devices in WMNs co-operate with
each other in transmitting packets through the network.
 WMNs are believed to be self-configuring and self-healing
networks.
 Dramatic increase in link quality just by shortening the
distance between the nodes.

4. Types of nodes in WMNs
 Wireless Mesh Router
 contains additional routing functions to support mesh networking.
 usually equipped with multiple wireless interfaces built on either the
same or different wireless access technologies
 improves the flexibility of mesh networking
 Mesh Clients
 can also work as routers since they also have necessary functions for
mesh networking.
 gateway and bridge functions do not exist in these nodes.
 usually have only one wireless interface as in Laptop/desktop PC,
pocket PC, PDA, IP phone, RFID reader, etc.

5. WMN Architecture
 Based on the functionality of the nodes the architecture of
WMNs can be classified into:
 Infrastructure mesh Architecture,
 Client mesh Architecture and
 Hybrid mesh architecture

6. Infrastructure Mesh
 In infrastructure mesh architecture, the mesh routers
collectively provide a wireless backbone infrastructure. Client
node is passive in mesh infrastructure.

7. Client Mesh
 Client meshing provides peer-to-peer networks among client
devices. Here no such mesh router is required. Client will act
like a mesh router by relaying the packets.

8. Hybrid Mesh
 Mesh router provide the backbone of such network.
 With the help of network functionalities such as routing and forwarding
of data packets, clients can actively participate in the creation of the
mesh.

9. Characteristics of WMNs
 Low-Cost:
 The low cost of the hardware based on IEEE 802.11
standards is one of the prominent reasons in the increasing
interests in both research and product development.
 Integration and interoperability:
 Integration and interoperation with other networks, and
bridges to legacy networks can be easily accommodated due
to the fact that most WMNs are based on Internet Protocol
standards.

10. Applications
• Broadband home networking
• Community and neighborhood networking
• Enterprise networking
• Metropolitan area networks
• Transportation systems
• Building automation

11. Standard
 IEEE 802.11s is the most relevant emerging standards for
WMN technology
 Efforts are underway in several IEEE working groups, like
802.11, 802.15, 802.16, and 802.20, to define mesh standards.

12. Protocol Layers
 Some of the factors that affect the capacity and performance of WMNs
 network architecture,
 network topology,
 traffic pattern,
 network node density,
 number of channels used for each node,
 transmission power level, and
 node mobility.
 In order to develop the protocols we need to clearly understand the
relationship between the above factors and the capacity of WMNs.

13. Physical Layer
 The wireless radios of WMNs can support multiple transmission rates
by a combination of different modulation and coding rates.
 Adaptive error resilience can be provided through link adaptation.
 Orthogonal frequency multiple access (OFDM) and ultra-wide band
(UWB) techniques are the schemes that are being used to support
high-speed transmissions.
 If we desire to increase the capacity and mitigate the impairment by
fading, delay-spread, co-channel interference, fading, multi-antenna,
systems such as antenna diversity and smart antenna have been
proposed for wireless communications.
 It is more difficult to develop such techniques for WMNs although
these physical-layer techniques are also desired by other wireless
networks.

14. Physical Layer
 Frequency-agile or cognitive radios are being developed to
dynamically capture the unoccupied spectrum to achieve better
spectrum utilization and viable frequency planning for WMNs.
 Since all the components of a radio, such as RF bands, channel
access modes, and channel modulations, are programmable
implementing cognitive radios on a software radio platform is one
of the most powerful solutions.
 Although physical test-beds are currently available, the software
radio platform is not a mature technology yet. But as it can enable
the programmability of all advanced physical layer techniques, in
the future it seems to be a key technology for wireless
communications

15. MAC Layer
 There are differences between the MAC in WMNs and other
wireless networks:
 MAC for WMNs is concerned with more than one-hop communication.
 MAC is distributed, needs to be collaborative, and works for multipoint-to-
multipoint communication.
 Network self-organization is needed for better collaboration between
neighboring nodes and nodes in multi-hop distances.
 Mobility is low but still affects the performance of MAC
 For WMNs, a MAC protocol can be designed to work on a single channel
or multiple channels simultaneously.

16. Routing Layer
 The design of the routing protocols for WMNs is still an area of
research although there are many routing protocols that are
available for ad hoc networks.
 However, an optimal routing protocol for WMNs must possess
features like:
 multiple performance metrics
 scalability
 robustness and
 efficient routing with mesh infrastructure.
 The routing protocols for ad hoc networks is equipped with some
of these features, but non of them possesses all of the above.

17. Routing Protocols
 Multi Radio Routing
 In a multi-radio link quality source routing (MR-LQSR) a new performance
metric , weighted cumulative expected transmission time (WCETT) , is
incorporated.
 Both link quality metric and the minimum hop count are accounted for in
WCETT which provides a good tradeoff between delay and throughput.

18. Routing Protocols
 Multi-Path Routing:
 Better load balancing and providing high fault tolerance are the two main
objectives of using multi-path routing.
 Multiple paths are selected between source and the destination
 This provides better fault tolerance as when a link is broken another path
can be chosen.
 This enhances efficiency since without waiting to set up a new routing path,
the end-to-end delay, throughput, and fault tolerance can be improved.
 Complexity is the major hurdle of multi-path routing.
 Also, the availability of node disjoint routes between source and destination
determines the improvement, given an performance metric.

19. Routing Protocols
 Hierarchical Routing:
 The hierarchical routing protocols tend to achieve better
performance when the node density is high.
 This is because of less overhead, shorter average routing path,
and quicker set-up procedure of routing path etc.
 Maintaining hierarchy definitely adds to the complexity and
this may compromise the performance of the routing protocol.

20. Routing Protocols
 Geographical routing
 This kind of routing scheme forwards packets only by using the position
information of the nodes in the vicinity and in the destination node unlike
the topology based schemes.
 This suggests that there is less impact on the geographic routing due to a
topology change than the other routing protocols.
 The algorithm used in geographical routing (single-path greedy routings)
suffers from that a delivery is not guaranteed even if a path exists between a
source and the destination as the packet forwarding decision is made based
on the location information of the current forwarding node, its neighbors,
and the destination node.
 Planar-graph based geographic routing algorithms have been proposed
which guarantees the delivery. Theses algorithms suffer form a major
drawback: a higher communication overhead.

21. Transport Layer
 A large number of transport protocols are available for ad hoc
networks and WMNs depend on those transport layer
protocols
 Till date, there is no transport protocol that has been proposed
specifically for WMNs.
 We know that ad hoc network is also not mature. It also has
various unresolved issues. This suggests further research in
this area.

22. Application Layer
 There are numerous applications that are supported by
WMNs and they are categorized into various classes.
 Internet access
 Distributed Information Storage and Sharing
 Information Exchange across multiple wireless networks
 The areas of research in application areas include these
classes.
 Improving existing application layer protocols, proposing
new application-layer protocols for distributed information
sharing, and developing innovative applications for WMNs
are the areas of more research.

23. Advantages of Mesh Networks
 Reduction of installation costs
 Large-scale deployment
 Reliability
 Self-management

24. Key Research Challenges
 High-capacity and reliable radio interfaces for the wireless
backbone
 Designing scalable and opportunistic networking functions
 System-wide resource management

25. Conclusion
 The mesh network architecture addresses the emerging market
requirements for building wireless networks that are highly
scalable and cost effective, offering a solution for the easy
deployment of high-speed ubiquitous wireless Internet.
 In addition to802.11s, other IEEE Working Groups are
currently working to provide mesh-networking extensions to
their standards (e.g., 802.15.5,802.16a, and 802.20).

26. References
 www.google.com
 www.wikipedia.com
 www.studymafia.org

27. Thanks