Wireless networks - Lecture 31: Wireless mesh networks

Wireless networks - Lecture 31: Wireless mesh networks (Part 1). The main topics covered in this chapter include: introduction to WMN; characteristics; WMN vs MANET; architecture; applications; critical factors influencing performance; dynamically self-organized and self-configured;...

Wireless Networks

Lecture 31 Wireless Mesh Networks

Dr Ghalib A Shah

 Critical factors influencing performance

► Radio techniques, scalability, QoS, security, Ease of

 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

 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

 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.

 Multi-hop

► To extend the coverage range of wireless networks

without sacrificing the channel capacity and non of-sight

line- 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

 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

 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

 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 routing function available in mesh router

host- Users of one network can enjoy services of other

network

In MANET, each host perform routing and

 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

 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.

WMN Routers

 Examples of mesh routers based on different embedded  

  systems: (a) PowerPC and (b) Advanced Risc Machines (ARM)

 Mesh clients

► Also have necessary functions for routing in mesh

networking

► However gateway or bridge functions do not exist

► Usually single interface

WMN Clients

 Examples of mesh clients: (a) Laptop, (b) PDA, 

(c) Wi­Fi IP Phone and (d) Wi­Fi RFID Reader.

Infrastructure/backbone WMNs

 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

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.

Hybrid WMNs

 Combination of infrastructure and client meshing

 Most applicable/practical scenario

Application scenario

 Research and development in WMNs is

motivated by several applications which can be supported on cellular, WiMAX etc.

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.

Community and neighborhood networking

► Services between end-users can not be shared.

► Single path for internet and neighborhood user

Enterprise networking

 Scalable with enterprise growth

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

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

 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

 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

 Critical factors influencing performance

► Radio techniques, scalability, QoS, security, Ease of

Use, Mesh connectivity