1. 1 Wireless Networks Lecture 31 Wireless Mesh Networks Dr. Ghalib A. Shah

2. 2 Outlines  Introduction to WMN  Characteristics  WMN vs MANET  Architecture  Applications  Critical factors influencing performance ►Radio techniques, scalability, QoS, security, Ease of Use, Mesh connectivity

3. 3 Last Lecture  Limitations of QoS in IEEE 802.11  Overview of 802.11e  Traffic Categories  EDCF  HCF  Mobile IP ►Care-of-address, ►MIP Protocol (Discovery, Registration, Tunneling) ►Routing ►Inefficiencies ►MIPv6

4. 4 Introduction  Wireless mesh networks (WMNs) comprised of mesh routers and clients  Mesh clients not only work as host but also perform routing for multi-hop destinations  Mesh routers support bridge/gateway functionalities enabling integration of WMNs with existing wireless networks such as cellular, WSN, WiMAX etc  WMN is dynamically self-organized and self-configured

5. 5  Conventional nodes e.g. PC, PDA, PocketPC, phones, equipped with wireless NIC can connect directly to mesh routers.  Without Wireless NIC, Ethernet connection is also possible  Thus WMN will allow always-on-line anywhere anytime.  Gaining interest as a possible way of ISPs  Can be deployed incrementally as needed

6. 6 Source: NC State university, dept. of computer engineering

7. 7  Deploying WMN is not difficult because most of the components/protocols are readily available to some extent e.g. IEEE 802.11, WEP etc.  However scalability in existing protocol is a great concern.

8. 8 Characteristics  Multi-hop ►To extend the coverage range of wireless networks without sacrificing the channel capacity and non line- of-sight.  Support for ad hoc networking ►Due to flexible architecture, easy deployment and configuration, fault tolerance and mesh connectivity is possible. ►Low up-front investment requirements

9. 9  Mobility dependence on type of mesh nodes ►Mesh routers usually have minimal mobility ►Mesh clients can be stationary or mobile  Multiple type of network access ►Both backhaul access to internet and P2P communication are supported ►Integration of WMN with other wireless networks allow end- users access to WMN

10. 10  Dependence of power-consumption constraints on the type of mesh nodes.  Compatibility and interoperability with existing wireless networks. ►WMN based on IEEE 802.11 should support both mesh clients as well as Wi-Fi clients. ►It should also be interoperable with other networks.

11. 11 WMNs vs MANET  WMNs are considered ad hoc due to lack of infrastructure (AP/BS). ►although ad hoc techniques like MANET are required but WMNs require more sophisticated algorithms and design principles WMN diversifies the capabilities of ad hoc that makes MANET subset of WMNs ►Following differences will illustrate it more

12. 12  Wireless Backbone  Integration  Dedicated routing and configuration  Mesh routers as wireless backbone providing more coverage, connectivity and robustness. Individual nodes are routers in MANET making unreliable.  Supports client that use the same radio technology. Which is accomplished through host- routing function available in mesh router  Users of one network can enjoy services of other network  In MANET, each host perform routing and configurations which is done by mesh routers in WMNs. Hence decreasing load on end-user

13. 13  Multiple radios  Mobility  Two radios; one for routing and configuration functionalities between mesh routers. Second radio for network access by end users. These are performed on same channel in MANET  This significantly improves the performance.  Hosts also working as router in MANET make it more challenging, where the mobility of mesh routers is very limited

14. 14 Architecture  Mesh router ►support routing functions for mesh networking in addition to conventional gateway/repeater functions. ►Furthermore, equipped with multiple interfaces built on either same or different wireless access technologies. ►achieves the same coverage as the other wireless routers with less energy consumption through multi-hop routing. ►MAC protocols are enhanced with better scalability in multi-hop mesh environment.

15. 15 WMN Routers Examples of mesh routers based on different embedded systems: (a) PowerPC and (b) Advanced Risc Machines (ARM)

16. 16  Mesh clients ►Also have necessary functions for routing in mesh networking. ►However gateway or bridge functions do not exist. ►Usually single interface

17. 17 WMN Clients Examples of mesh clients: (a) Laptop, (b) PDA, (c) Wi-Fi IP Phone and (d) Wi-Fi RFID Reader.

18. 18 Infrastructure/backbone WMNs  Built using various wireless technologies in addition 802.11  With gateway functions, mesh router can connect to internet

19. 19  Infrastructure meshing allowing integration of different networks.  If client has different technology then it can connect through BS and BS through Ethernet.  The most common type. For example, community and neighborhood networks can be built. ►Mesh routers can be placed on the roof of houses ►Serve as access point for users inside the house and along the roads. ►Two types of radio; one for backbone and other for users ►Backbone communication can be established using long range and end-user using short range

20. 20 Clients WMNs  Client meshing provides P2P network among client devices  No mesh router required.  Clients in this arch. require more functionalities for configuration and routing  Formed using single radio.

21. 21 Hybrid WMNs  Combination of infrastructure and client meshing  Most applicable/practical scenario

22. 22 Application scenario  Research and development in WMNs is motivated by several applications which can be supported on cellular, WiMAX etc.

23. 23 Broadband home networking  WLAN is not practical because AP leave dead zones and multiple APs require backbone network or access hub.  Dead zones can be eliminated with multiple routers and adjusting their transmission power.

24. 24 Community and neighborhood networking

25. 25  The common architecture is to use cable or DSL through internet.  It has drawbacks ►All traffic must flow through internet ►Dead zones ►Services between end-users can not be shared. ►Single path for internet and neighborhood user

26. 26 Enterprise networking  Scalable with enterprise growth

27. 27 Other applications  Transportation system ►Instead of limiting access to stations, WMNs can extend access into buses, trains, ferries. ►Remote monitoring of in-vehicle security video and passenger information system  Building automation  Health and medical system  Security surveillance system

28. 28 Critical factors influencing network performance  Radio techniques ►Directional and smart antennas ►MIMO systems ►Multi-radio chipsets ►More advanced techniques such as reconfigurable radios, cognitive radios ►These require revolutionary design changes in higher layers

29. 29  Scalability ►Multihop routing is common in WMN, which degrades performance. ►IEEE 802.11 MAC is not scalable and throughput significantly reduces as number of hops increases to 4 or higher  Mesh connectivity ►Network self-organization and topology control algorithms are needed

30. 30  Broadband and QoS ►Different from ad hoc networks, most applications of WMN are broadband services with various QoS requirements.  Compatibility and inter-operability ►Network access to both conventional and mesh clients  Security ►No centralized control  Ease of use

31. 31 Summary  Introduction to WMN  Characteristics  WMN vs MANET  Architecture  Applications  Critical factors influencing performance ►Radio techniques, scalability, QoS, security, Ease of Use, Mesh connectivity