Adhoc Challenges and Future

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Proceedings of National Conference on Challenges & Opportunities in Information Technology (COIT-2007)RIMT-IET, Mandi Gobindgarh. March 23, 2007.

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Mobile Ad hoc Networks: Challenges and FutureKavita Taneja1 and R. B. Patel

2

1M.M. Instt. Of Computer Tech. & Business Management, Mullana, Haryana, India.2Deptt. Of Computer Engg. , M.M. Engineering College, Mullana, Haryana, India.

{[email protected], [email protected]

1. INTRODUCTION

Wireless networks have become increasingly popular in the

past few decades, particularly

within the 1990s when they are being adapted to enable

mobility and wireless devices became popular. As the

popularity of mobile devices (MDs) and wireless networks

significantly increased over the past years, wireless ad hoc

networks has now become one of the most vibrant and active

fields of communication and networking research. Given

many intriguing future applications of mobile ad hoc

networks (MANETs), there are still some critical challengesand open problems to be solved. Thus, broadly in this paper

we present an overview of the history of MANET, and their

routing protocols. Then we present several challenging issues

and the future work.

1. MANET:HISTORYThe whole life-cycle of ad-hoc networks could be categorized

into the first, second, and the third generation ad-hoc

networks systems. Present ad-hoc networks systems are

considered the third generation. The first generation goes

back to 1972. At that time, they were called PRNET (Packet

Radio Networks). The history of ad-hoc networks can be

dated back to the DoD1-sponsored Packet Radio Network(PRNET) research for military purpose in 1970s, which

evolved into the Survivable Adaptive Radio Networks

(SURAN) program in the early 1980s [1]. In conjunction

with ALOHA (Areal Locations of Hazardous Atmospheres)

and CSMA (Carrier Sense Medium Access), approaches for

medium access control and a kind of distance-vector routing

PRNET were used on a trial basis to provide different

networking capabilities in a combat environment. The second

generation of ad-hoc networks emerged in 1980s, when the

ad-hoc network systems were further enhanced and

implemented as a part of the SURAN (Survivable Adaptive

Radio Networks) program. This provided a packet-switched

network to the mobile battlefield in an environment without

infrastructure. This program proved to be beneficial inimproving the radios' performance by making them smaller,

cheaper, and resilient to electronic attacks. In the 1990s, the

concept of commercial ad-hoc networks arrived with

notebook computers and other viable communications

equipment. At the same time, the idea of a collection of

mobile nodes was proposed at several research conferences.

Since mid 1990s, a lot of work has been done on the ad hoc

standards. Within the IETF, the MANET working group was

born, and made effort to standardize routing protocols for ad

hoc networks. Meanwhile, the IEEE 802.11 subcommittee

standardized a medium access protocol that was based on

collision avoidance and tolerated hidden terminals, for

building mobile ad hoc network prototypes out of notebooks

and 802.11 PCMCIA cards. There are currently two kinds of

mobile wireless networks. The first is known as

infrastructured networks with fixed and wired gateways.

Typical applications of this type of one-hop wireless

network include wireless local area networks (WLANs). The

second type of mobile wireless network is theinfrastructureless mobile network, commonly known as the

MANET. MANET is usually a self-organizing and self-

configuring multi-hop network which does not require anyfixed infrastructure. In such network, all nodes are

dynamically and arbitrarily located, and are required to relay

packets for other nodes in order to deliver data across the

network.

2. ROUTING PROTOCOLSRouting is the most fundamental research issue in MANET

[2] and must deal with limitations such as high power

consumption, low bandwidth, high error rates and

unpredictable movements of nodes. Generally, current routingprotocols for MANET can be categorized as: (1) pro-active

(table-driven), (2) re-active (source-initiated on-demand

driven) and (3) hybrid. Popular proactive routing protocols

are Destination-Sequenced Distance Vector (DSDV) [3] and

Wireless Routing Protocol (WRP) [4].They attempt tomaintain consistent, up-to-date routing information of the

whole network. These keep track of routes for all destinations

and enjoy having the advantage of experiencing minimal

initial delay in communications with arbitrary destinations.

When the application starts, a route can be immediately

selected from the routing table. Such protocols are called

proactive because they store route information even before it

is needed. Re-active routing protocols try to eliminate the

conventional routing tables and consequently reduce the needfor updating these tables to track changes in the network

topology. In contrast to pro-active routing protocols which

maintain all up-to-date at every node, routes are created only

when desired by the source node in re-active protocols. When

a source requires to a destination, it has to establish a route by


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route discovery procedure, maintain it by some form of route

maintenance procedure until either the route is no longer

desired or it becomes inaccessible, and finally tear down it by

route deletion procedure. Some reactive protocols are Cluster

Based Routing Protocol (CBRP) [5], Ad Hoc On-Demand

Distance Vector (AODV) [6] and Dynamic Source Routing

(DSR) [7]. Hybrid routing protocols aggregates a set of nodes

into zones in the network topology. Then, the network is

partitioned into zones and proactive approach is used within

each zone to maintain routing information. To route packets

between different zones, the reactive approach is used.

Consequently, in hybrid schemes, a route to a destination that

is in the same zone is established without delay, while a route

discovery and a route maintenance procedure is required for

destinations that are in other zones. The zone routing

protocol (ZRP) [8] and zone-based hierarchical link

state (ZHLS) routing protocol provide a

compromise on scalability issue in relation to the

frequency of end-to-end connection, the total

number of nodes, and the frequency of topology

change. Furthermore, these protocols can provide abetter trade-off between communication overhead

and delay, but this trade-off is subjected to the size

of a zone and the dynamics of a zone. Thus, the

hybrid approach is an appropriate candidate for

routing in a large network.

3. MANET:CHALLENGESThe major challenges faced by the internet architecture can

be broadly classified as:

a) In incorporating emerging wireless network elements such

as MDs, ad-hoc routers and embedded sensors in the existing

protocol framework andb) To provide end-to-end service abstractions that facilitates

application development.

These challenges are posed by a broad range of environments

such as cellular data services, WiFi hot-spots, Info stations,

mobile peer-to-peer, Ad-hoc mesh networks for broadband

access, vehicular networks, sensor networks and pervasive

systems. These wireless application scenarios lead to a

diverse set of service requirements for the future Internet as

summarized below:

1. Naming and addressing flexibility.

2. Mobility support for dynamic migration of end-users and

network devices.

3. Location services that provide information on geographic

position.4. Self-organization and discovery for distributed control of

network topology.

5. Security and privacy considerations for mobile nodes and

open wireless channels.

6. Decentralized management for remote monitoring and

control.

7. Cross-layer support for optimization of protocol

performance.

8. Sensor network features such as aggregation, content

routing and in-network

Processing.

9. Cognitive radio support for networks with physical layer

adaptation.

10. Economic incentives to encourage efficient sharing of

resources.

Taken together, the above MANET requirements represent a

spectrum of network

challenges. During the last few years, almost every aspect of

MANET has been explored to some level of detail. Yet, more

questions have arisen than been answered [2]. The major open

problems are listed as:

A. Autonomous- No centralized administration entity isavailable to manage the operation of the different mobile

nodes.

B. Dynamic topology- Nodes are mobile and can beconnected dynamically in an arbitrary manner. Links of

the network vary timely andare based on the proximityof one node to another node.

C. Device discovery- Identifying relevant newly moved innodes and informing about their existence need dynamic

update to facilitate automatic optimal route selection.

D. Bandwidth optimization- Wireless links havesignificantly lower capacity than the wired links.

E. Limited resources -Mobile nodes rely on battery power,which is a scarce resource. Also storage capacity and

power are severely limited.

F. Scalability- Scalability can be broadly defined as whetherthe network is able to provide an acceptable level of

service even in the presence of a large number of nodes.

G. Limited physical security- Mobility implies highersecurity risks such as peer-to- peer network architecture

or a shared wireless medium accessible to both legitimate

network users and malicious attackers. Eavesdropping,spoofing and denial-of-service attacks should be

considered.

H. Infrastructure-less and self operated- Self healing featuredemands MANET should realign itself to blanket any

node moving out of its range.

I. Poor Transmission Quality- This is an inherent problemof wireless communication caused by several error

sources that result in degradation of the received signal.

J. Ad hoc addressing- Challenges in standard addressingscheme to be implemented.

K. Network configuration- The whole MANETinfrastructure is dynamic and is the reason for dynamic

connection and disconnection of the variable links.

L. Topology maintenance- Updating information ofdynamic links among nodes in MANETs is a major

challenge.

5. THE FUTURE


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Ad hoc networks, the most talked about term in wireless

technologies, approach to be the emperor of future airs

provided the vision of anytime, anywhere communications.

At present, the general trend is toward mesh architecture and

large scale. New applications call for both bandwidth and

capacity, which implies the need for a higher frequency and

better spatial spectral reuse. Propagation, spectral reuse, and

energy issues support a shift away from a single long wireless

link (as in cellular)to a mesh of short links (as in MANET).Research on multi-hop architecture showed it a promising

solution to the implementation of ad hoc networks. As the

evolvement goes on, especially the need of dense deployment

such as battlefield and sensor networks, the nodes in MANET

will be smaller, cheaper and capable.

REFERENCES

[1] Lecture Notes, Broadband Computer Networks, by

Prof. Zhisheng Niu, Tsinghua University, 2003.

[2] E. M. Royer and C-K Toh, A Review of Current

Routing Protocols for Ad-Hoc Mobile Wireless

Networks, IEEE Person. Commun., Vol. 6, no. 2, Apr.

1999.

[3] C.E.Perkins and P. Bhagwat, Highly dynamic

destination-sequenced distance vector routing for mobile

computers, Comp, Comm. Rev., Oct.1994, pp 234-44.

[4] S.Murthy & J.J Garcia-Luna-Aceves, An Efficient

Routing Protocol for Wireless Networks, App. J.

Special issue on Routing in mobile communication

networks, Vol. 1(3):183-97, Oct 1996.

[5] Mingliang Jiang, Jinyang Li, Y.C. Tay, Cluster Based

Routing Protocol, Aug.1999 IETF Draft, pp 1-27.

[6] Elizabeth Royer and Charles E. Perkins, Multicast

Operation of the Ad-hoc On-Demand Distance Vector

Routing Protocol, in Proceedings of MobiCom '99,

Seattle, WA, Aug. 1999, pp. 207-218.

[7] David B. Johnson, Davis A. Maltz, The Dynamic SourceRouting Protocol for MANETs, Oct. 1999, IETF Draft,

pp.1- 49.

[8] Wang, L. Olariu, S., A two-zone hybrid routing protocol

for mobile ad hoc networks, Parallel and Distributed

Systems, IEEE Transactions on Vol. 15(12):11051116,

Dec. 2004.

[9] P. Gupta and P. R. Kumar, The Capacity of Wireless

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Adhoc Challenges and Future