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1. www.studymafia.org
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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