survey of WMN

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ISSN: 2277-3754ISO 9001:2008 Certified

International Journal of Engineering and Innovative Technology (IJEIT)

Volume 2, Issue 6, December 2012

338

Abstract ----Wi reless mesh networks (WMNs) have emerged as

a key technology for next-generation wireless networking.

Because of their advantages over oth er wir eless networks, WMNs

are undergoing rapid progress and inspiring numerous

applications. Wireless mesh networks (WMNs) consist of mesh

routers and mesh clients, where mesh routers have minimal

mobili ty and form the backbone of WMNs. They provide network

access for both mesh and conventi onal cl ients. The integrati on of

WMNs with other networks such as the Internet, cell ular , I EEE

802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be

accomplished through the gateway and bridging functions in the

mesh routers WMNs will deliver wir eless services for a large

variety of applications in personal, local, campus, and

metropoli tan areas. However, many technical issues stil l exist in

this fi eld. I n order to provide a better understanding of the

research chall enges of WMNs, this art icle presents a detail ed

investigation of current state-of-the-art protocols and algori thms

for WMNs. Open r esearch issues in all protocol layers are also

discussed, with an objective to spark new research in terests in thi s

field.

I ndex TermsWireless Mesh Network, Mesh Client, Mesh

Router.

I. INTRODUCTIONWireless networks go forward into the next generation to

provide better services, in which wireless mesh networks

(WMNs), has emerged recently. There are currently two form

of wireless networks. The first is known as the

infrastructured network. It is a network which has fixed and

wired gateways. The bridges for these networks are known as

base stations. Typical applications of this type of networks

include office wireless local area networks (WLANs).

The second type is infrastructure less and these types of

networks are known as self-organized networks. They

consist of mobile radio nodes which do not need existing

network infrastructure or central system management. They

are suitable for situations that need an immediate

infrastructure.

In contrast to traditional wireless networks, WMNs are not

built on a fixed infrastructure. Instead of this, hosts rely on

each other to keep the connection. WMNs provide low-cost

broadband internet access, wireless LAN coverage and

network connection to fixed or mobile hosts for both network

operators and users. The reason of preferring WMNs is easy,

fast and deployment of the technology. In WMNs, nodes are

comprised of mesh routers and mesh clients. Each node

operates not only as a host but also as a router, forwarding

packets on behalf of other nodes that may not be within direct

wireless transmission range of their destinations.

Conventional nodes (e.g., desktops, laptops, PDAs,

PocketPCs, phones, etc.) equipped with wireless network

interface cards (NICs) can connect directly to wireless mesh

routers. Customers without wireless NICs can access WMNs

by connecting to wireless mesh routers through, for example,

Ethernet. Thus, WMNs will greatly help the users to be

always-on-line anywhere anytime. Moreover, the

gateway/bridge functionalities in mesh routers enable the

integration of WMNs with various existing wireless networks

such as cellular, wireless sensor, wireless fidelity (Wi-Fi),worldwide inter-operability for microwave Access

(WiMAX), WiMedia networks.

WMNs are undergoing rapid commercialization in many

other application sectors such as broadband home

networking, community networking, building automation,

high speed metropolitan area networks, and enterprise

networking. With the capability of self-organization and self

configuration, WMNs can be deployed incrementally, one

node at a time, as needed. As more nodes are installed, the

reliability and connectivity for the users increase accordingly.

Nowadays, several companies have already realized the

potential of this technology and offer wireless meshnetworking products. A few test beds have been established in

university research labs. However, for a WMN to be all it can

be, considerable research efforts are still needed. For

example, the available MAC and routing protocols are not

scalable; throughput drops significantly as the number of

nodes or hops in WMNs increases.

In this article we present a survey of recent advances in

protocols and algorithms for WMNs. Our aim is to provide a

better understanding of research challenges of this emerging

technology. The rest of this article is organized as follows.

The network architectures of WMNs are first presented, with

an objective to highlight the characteristics of WMNs and thecritical factors influencing protocol design.

II. WIRELESS MESH NETWORKARCHITECTUREWireless interfaces built on either the same or different

wireless access technologies. Compared with a conventional

wireless router, a wireless mesh router can achieve the same

coverage with much lower transmission power through

multi-hop communications. Optionally, the medium access

control (MAC) protocol in a mesh router is enhanced with

better scalability in a multi-hop mesh environment. The

architecture of WMNs can be classified into three main

groups based on the functionality of the nodes [1]:

A. I nfr astructure/Backbone WMNsThis type of WMNs includes mesh routers forming an

Survey of Wireless Mesh NetworkA.Valarmozhi, M.Subala, V.Muthu

Assistant Professors, Department of Information Technology

Veltech Hightech Dr.Rangarajan Dr.Sakunthala Engineering College, Avadi.


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infrastructure for clients that connect to them. The WMN

infrastructure/ backbone can be built using various types of

radio technologies, in addition to the mostly used IEEE

802.11 technologies. The architecture is shown in Fig 1,

where dash and solid lines indicate wireless and wired links,

respectively. The mesh routers form a mesh of

self-configuring, self-healing links among themselves. With

gateway functionality, mesh routers can be connected to the

Internet. This approach, also referred to as infrastructure

meshing, provides backbone for conventional clients and

enables integration of WMNs with existing wireless

networks, through gateway/bridge functionalities in mesh

routers

Fig.1. Infrastructure/Backbone WMNs

B. Client WMNsClient meshing provides peer-to peer networks among client

devices. In this type of architecture, client nodes constitute the

actual network to perform routing and configuration

functionalities as well as providing end user applications to

customers. Hence, a mesh router is not required for these

types of networks. In this case, highest level of data

transmission occurs. A packet is sent to reach a destination

through multi nodes. All traffic crosses over single nodes in

the network. Moreover, the requirements on end-user devices

is increased when compared to infrastructure meshing, since,in Client WMNs, the end-users must perform additional

functions such as routing and self-configuration .The Client

WMNs architechtecture is shown in fig 2.

Fig.2.Client WMNs

C. Hybrid WMNsThe combination of infrastructure and client meshing is

referred as Hybrid WMNs.Mesh clients can access the

network through mesh routers as well as directly meshing with

other mesh clients. While the infrastructure provides

connectivity to other networks such as the Internet, Wi-Fi,

WiMAX, cellular, and sensor networks; the routing

capabilities of clients provide improved connectivity and

coverage inside the WMN. The hybrid architecture will be the

most applicable case in the near future. The hybrid

architecture is shown in fig 3.

Fig.3. Hybrid WMNs

D. Characteri stic of WMNs: The main goal of WMNs is to increase the

coverage range of current wireless network in

order to solve Line-of-Sight (LoS) problem

especially on central

wireless networks the WMNs is designed as amesh-style multi-hopping which achieves higher

Throughput.

Addition or subtraction to network can be madeeasily after network deployment. Network can be

enlarged or narrowed. Coverage and interactivity

are uncontrolled.

WMNs have the functionality of P2P network aswell as accessibility to different network

environments and technologies smoothly.

WMNs do not have energy consumptionconstraints unlike existing protocols. Energy

efficiency is not placed on the top in terms of

priority on WMNs.

They conform with current wireless networktechnologies. As WMNs use IEEE 802.11

technology, other communicated networks should

predicate this technology on.

Ensuring and carriage of functionality areprovided with mesh. Accomplishment of these

issues includes routing, security, management and

power control.


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Nodes are free on their movement. They canchange their networks and move between cells.

Thus, WMNs have a very dynamic structure.

Wireless operation is necessary for supportingmobility. So, signals and optical hardware can be

used to provide wireless operation.

All nodes must join a routing process on thenetwork

Therefore, WMNs diversify the capabilities of ad-hoc

networks instead of simply being another type of ad hoc

network. These additional capabilities necessitate new

algorithms and design principles for the realization of WMNs

III. DESGINFACTORSINFLUENCINGTHE

PERFORMANCEOFWMNS

A. Radio Techni ques.

Many approaches have been proposed to increase capacity

and flexibility of wireless systems in recent years. Typical

examples include directional and smart antennas, multiple

input multiple output (MIMO) systems, and

multi-radio/multi-channel systems. To further improve the

performance of a wireless radio and control by higher layer

protocols, more advanced radio technologies, such as

reconfigurable radios, frequency agile/cognitive radios, and

even software radios, have been used for wireless

communication. Although these radio technologies are still in

their infancy, they are expected to be the future platform for

wireless networks due to their dynamic control capability.These advanced wireless radio technologies all require a

revolutionary design in higher-layer protocols, especially

MAC and routing protocols.

B. Scalability

Scalability is a critical requirement of WMNs. Without

support of this feature, the network performance degrades

significantly as the network size increases. For example,

routing protocols may not be able to find a reliable routing

path, transport protocols may loose connections, and MAC

protocols may experience significant throughput reduction.

To ensure the scalability in WMNs, all protocols from the

MAC layer to the application layer need to be scalable.

C. Mesh Connectivity

Many advantages of WMNs originate from mesh

connectivity. To ensure reliable mesh connectivity, network

self-organization and topology control algorithms are needed.

Topology-aware MAC and routing protocols can significantly

improve the performance of WMNs.

D. Broadband and QoS.

Different from classical ad hoc networks, most applications

of WMNs are broadband services with heterogeneous QoS

requirements. Thus, in addition to end-to-end transmission

delay and fairness, more performance metrics, such as delay

jitter, aggregate and per-node through-put, and packet loss

ratios, must be considered by communication protocols.

E. SecurityAlthough many security schemes have been proposed for

wireless LANs in recent years, they are still not fully

applicable for WMNs. For instance, there is no centralized

trusted authority to distribute a public key in a WMN due to

the distributed system architecture. The existing security

schemes proposed for ad hoc networks can be adopted for

WMNs. However, most of the security solutions for ad hoc

networks are still not mature enough to be implemented

practically. Moreover, the different network architectures

between WMNs and ad hoc networks usually render a

solution for ad hoc networks ineffective in WMNs.

F. Ease of UseProtocols must be designed to enable the network to be as

autonomous as possible. In addition, network management

tools need to be developed to efficiently maintain theoperation, monitor the performance, and configure the

parameters of WMNs. These tools, together with the

autonomous mechanisms in networking protocols, enable

rapid deployment of WMNs.

G. Compatibili ty and I nter-operabil ityIn WMNs it is a default requirement to support network

access for both conventional and mesh clients. Therefore,

WMNs need to be backward compatible with conventional

client nodes. This demands that mesh routers need to be

capable of integrating heterogeneous wireless networks.

IV. APPLICATIONSOFWMNS

A. Broadband Wi reless Access

Currently, Broadband access has an important role in

information economy. It provides services for real time

applications such as: video telephony, online-gaming, video

on demand, and telecommunications. Each new application

has a significant impact on quality of life. For example,

Telecommuting can reduce daily traveling of individuals. It

leads to increased productivity for the time saving. It also

reduces traffic on the streets, thus it has a positive impact on

the environment. In urban and sub-urban areas, wired access

(Cable and DSL) is the first choice if the population densitybe reasonably high. Rural areas have limited coverage using

wireless technologies like satellite and cellular networks.

Satellite access has two drawbacks: expensive technology and

high latency due to the distance between the end client and the

satellite. In the case of cellular networks the towers are

expensive to install and operate. Lack of service providers

and the higher cost of the service itself makes lower usage of

broadband access. In order to wider adoption of Internet

access, WMNs offer an easy-to-deploy and cost effective

alternative in areas where cable TV or DSL lines are not

available. WMNs can be deployed quickly without expensive

equipment and the service provider can see a quick return oninvestment. Besides, because of the low cost deployment and

operations of WMNs, free broadband access to city residents

is also become possible. Many such networks already exist,


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and more are on the way.

B. I ndustrial Appli cations

In a building, there are many devices need to be monitored

and controlled like electrical devices including power, light,air conditioner, elevator, etc. Today, the wired networks are

taking care of such environment. This is very expensive due to

the complexity in deployment and maintenance of a wired

network. Currently, Wi-Fi networks are another option to

reduce the cost of such networks. But, this solution has not

achieved satisfactory performance yet for expensive wiring of

Ethernet which is needed for Wi-Fi Access Points (APs).

Replacing APs by mesh routers will solve the problem. The

deployment process will be much simpler and also the

deployment cost will be significantly reduced.

C. Healthcare

In a hospital or medical center, monitoring and updating

patient information like medical history, test results,

insurance information, etc., need to be processed and

transmitted from room to room. The ability to connect to the

network is crucial to ensure data access in every operating

room, office, and lab. In many hospitals data transmission is

usually broadband due to large amount of data, for instance:

high resolution medical images and periodical monitoring

information. WMN provides unlimited network access to any

fixed medical devices. It does not need to use existed Ethernet

connections, so that, it will eliminate dead spots and it also

cause low system cost and simplicity which cannot be find intraditional wired networks.

D. Tr ansportation systems

Internet access is limited to stations and stops using IEEE

802.11 and IEEE 802.16. To extend access into buses, plains,

ferries, and trains, WMN technology can help. Thus,

passengers on-board can access to the net while traveling

from one place to another. Other services such as remote

monitoring in-vehicle, driver communications and security

cameras can be supported too.

E. Hospitality

In hotels and resorts, one of their services is high-speedInternet connectivity which is free. Wireless mesh networks

are easy to set-up, lower in cost, and without having to change

the existing structures or disrupt business for both indoor and

outdoor.

F. Warehouses

One way to keep track of stock in warehouses is using

handheld scanners. It needs connectivity throughout the area.

Wireless mesh networks can ensure connectivity in modern

warehouses and shipping logistics with little cost and effort.

G. Temporary Venues

Construction sites can enjoy the easy set-up and removal of

wireless mesh networks. Architects and engineers can stay

connected and using camera to communicate and talk to each

other on spot. It provides them to see the real picture of the

project progresses. Other temporary venues such as: political

rallies, street fairs, and outdoor concerts can set-up and

remove wireless mesh networks in minutes.

V. CONCLUSION

Although WMNs can be built up based on existing

technologies, field trials and experiments with existing

WMNs prove that the performance of WMNs is still far below

expectations. As explained throughout this article, there still

remain many research problems. Among them, the most

important and urgent ones are the scalability and the security.

A. Scalability

Based on existing MAC, routing, and transport protocols,

network performance is not scalable with either the number of

nodes or the number of hops in the network. This problem can

be alleviated by increasing the network capacity through

using multiple channels/radios per node or developing

wireless radios with higher transmission speed. However,

these approaches do not truly enhance the scalability of

WMNs, because resource utilization is not actually improved.

Therefore, in order to achieve scalability, it is essential to

develop new MAC, routing, and transport protocols for

WMNs.

B. Security

WMNs are vulnerable to security attacks in various

protocol layers. Current security approaches may be effective

to a particular attack in a specific protocol layer. However,there still exists a need for a comprehensive mechanism to

prevent or counter attacks in all protocol layers. Moreover,

self-organization and self-configuration capability is a desired

feature in WMNs. It requires protocols in WMNs to be

distributive and collaborative. However, current WMNs can

only partially realize this objective. Furthermore, current

WMNs still have very limited capabilities of integrating

heterogeneous wireless networks, due to the difficulty in

building multiple wireless interfaces and the corresponding

gateway/bridge functions in the same mesh router.

In spite of these open research problems, we believe that

WMNs will be one of the most gifted technologies for nextgeneration wireless networking. For any commercial wireless

product, however, security should be one of the first problems

to be solved. For WMNs, there are several security issues to

be considered.Inorder to enhance the WMNs, more research

is needed in future.

REFERENCES[1] Ian F. Akyildiz , Xudong Wang , Weilin Wang , Wireless

mesh networks: a survey, I.F. Akyildiz et al. / Computer

Networks 47 (2005) 445487.

[2] A.A. Abouzeid, S. Roy, Stochastic modelling of TCP innetworks with abrupt delay variations, ACM/KluwerWireless Networks 9 (2003) 509524.


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[3] S. Waharte, B. Ishibashi, R. Boutaba, Performance Study ofWireless Mesh Networks Routing Metrics, Computer Systems

and Applications, April, 2008.

[4] Safak DURUKAN ODABASI1, A. Halim ZAIM2 ASURVEY on WIRELESS MESH NETWORKS, ROUTING

METRICS and PROTOCOLS, International Journal of

Electronics, Mechanical and Mechatronics Engineering Vol.2

Num.1 Pp.(92-104).

AUTHOR BIOGRAPHY

Ms.A.Valarmozhi received B.E Degree in Electrical

& Electronics Engineering from Kamaraj University,

Madurai in 2002 and M.E Degree in Computer

Science & Engineering from Anna University,

Chennai in 2008. Currently she is working as

Assistant Professor in the Department of Information

Technology, Veltech Hightech Dr.Rangarajan

Dr.Sakunthala Engineering College, Avadi. She will

do part time research in Wireless Networks at AnnaUniversity, Chennai. She has published research paper in peer reviewed

Journal. Her current research focuses on Wireless Networks and Adhoc

networks. She is a member of IAENG.

Mrs.M.Subala received B.Tech Degree in Information

Technology from Anna University, Chennai in 2005

and M.E Degree in Networking from Anna

University, Chennai in 2007. Currently she is working

as Assistant Professor in the Department of

Information Technology, Veltech Hightech

Dr.Rangarajan Dr.Sakunthala Engineering College,

Avadi. She will do part time research in Networks at

Anna University, Chennai.

Mr.V.Muthu received B.E Degree in ComputerScience & Engineering from M.S University,

Tirunelveli in 2001 and M.Tech Degree in

Information Technology from Satyabama University,

Chennai in 2009. Currently he is working as

Assistant Professor in the Department of Information

Technology, Veltech Hightech Dr.Rangarajan

Dr.Sakunthala Engineering College, Avadi. He will

do part time research in Data mining at Anna University, Chennai.

survey of WMN

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