1. Comparative Analysis -Full

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COMPARATIVE ANALYSIS OF AOMDV, AODV, DSR AND DSDV ROUTING

PROTOCOLS FOR COGNITIVE RADIO

SHRUTI SINGHROY, P. L. ZADE & NILIMA BODHYA

Department of Electronics Engineering, YCCE, Nagpur, Maharashtra, India

ABSTRACTCognitive radio (CR) technology is the most juvenile technology that promises to allow devices to share the

wireless spectrum with other users that have a license for operation in these spectrum bands, thereby solving the problem

of spectrum scarcity in the unlicensed bands. This improves the inefficient spectrum utilization in the bands reserved for

the licensed users. However, the opportunistic use of the available spectrum by the CR users must not affect the licensed

users. To achieve these features of CR networks an efficient routing algorithm is required. In this papers a survey of

routing protocols for CR wireless networks is discussed and a comparison between AOMDV, AODV, DSR and DSDV

Routing Protocols is presented.

KEYWORDS: Cognitive Radio (CR), Routing, Spectrum Handoff, AODV, DSR, AOMDV, DSDV

INTRODUCTION

The increase in wireless technology in the last few decades has led to an increased use of devices and services in

the unlicensed band. Thus unlicensed spectrum bands in the 2.4GHz and 5.8GHz range are being more and more used bywireless mesh networks, Wi-Fi hotspots, wireless sensor networks and mobile ad-hoc networks for a variety of military,

scientific research, environmental, educational and commercial applications. This has led to spectrum scarcity in the

unlicensed band, which is further affected by the interfering radiation caused by commercial microwave ovens and

electrical machinery. At the same time, the frequencies reserved for licensed use, for example television broadcast, are not

always occupied, leading to inefficient utilization of the resource. The newly up-and-coming CR paradigm has promised to

address these issues by allowing the CR users to opportunistically transmit in the vacant portions of the licensed spectrum

[1]. These radios may decide transmission parameters such as channel, power, modulation type, and transmission rate

through local coordination based on their perception of the state of the network and the physical environment. The Federal

Communications Commission (FCC) has encouraged work in spectrum sharing issues by initiating steps to free up

bandwidth in the 54 72MHz, 76 88MHz, 174 216MHz, and 470 806MHz bands [2]. These completely vacated

bands are referred to as primary bands and the licensed operators in them as primary users (PUs).

Figure 1: The Cognitive Radio Cycle

International Journal of Electronics, Communication &

Instrumentation Engineering Research and

Development (IJECIERD)

ISSN 2249-684X

Vol. 3, Issue 2, Jun 2013, 1-6

TJPRC Pvt. Ltd.


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2 Shruti Singhroy, P. L. Zade & Nilima Bodhya

Figure 1 above shows the steps of the cognitive cycle consist of four spectrum management functions: spectrum

sensing, spectrum decision, spectrum sharing, and spectrum mobility. The followings are the main features of spectrum

management functions:

Spectrum Sensing: A CR user should monitor the available spectrum bands, capture their information, and thendetect spectrum holes. Spectrum sensing is a basic functionality in CR networks, and hence closely related to

other spectrum management functions as well as layering protocols to provide information

Spectrum Decision: Once the available spectrums are identified, it is essential that the CR users select the bestavailable band according to their QoS requirements. Especially in CR ad-hoc networked, spectrum decision

involves in jointly undertaking spectrum selection and the route formation.

Spectrum Sharing: The transmissions of CR users should be coordinated by spectrum sharing functionality toprevent multiple users from colliding in overlapping portions of the spectrum. Spectrum sharing includes channel

and power allocations to avoid interference caused to the primary network and an intelligent packet scheduling

scheme enabled by a spectrum-aware link layer along with spectrum sensing.

Spectrum Mobility: If the specific portion of the spectrum in use is required by a PU, the communication mustbe switched to another vacant portion of the spectrum. This requires spectrum handoff and reliable end-to-end

connection management schemes, such as protocols at the transport layer that closely coupled with the lower level

spectrum sensing, neighbour discovery in a link layer, and routing protocols.

The above spectrum management-related challenges necessitate novel design techniques spanning several layers

of the protocol stack on a single device, in addition to the interaction between several nodes. Thus much of the research

work today is focused on the physical, link, network and transport layer protocol requirements for cognitive radio ad hoc

networks which should meet to optimally exploit available radio resources and simultaneously provide all the

communication services required.

It is already known that physical and link layer protocols designed for standard fixed bandwidth ad hoc networks

must be changed and adapted to cognitive radio environment to effectively utilize spectrum information [3]. The role of

those modified layers of the protocol stack is to manage radio resources in the way appropriate for the nodes in the whole

cognitive radio networks. The remaining layers might be adapted explicitly to cognitive radio networks. Indeed in [4]

authors claim that higher layers [above link layer] will implement standard protocols not specific to cognitive radios.

The rest of the paper is organized as follows: Section II describes the related work. Different routing protocols

namely AODV, DSDV, AOMDV and DSR are briefly discussed in section III. We present the performance evaluation of

these four routing protocols with reference to CR in section IV, and finally in section V we conclude the paper.

LITERATURESURVEY

Routing protocols for CR networks should be such that they exploit the characteristic flexibility of CRs. A

number of routing protocols for CR networks are available in the literature. The routing protocols for the CR networks can

be categorized according to the number and the usage of radios. In [5] routing algorithms for CRN are broadly categorized

into two main classes depending on the issue of spectrum-awareness and setting up of efficient routes as:

Full Spectrum Knowledge - In this case, a spectrum occupancy map is available to the network nodes, or to acentral control entity, which could be represented by the centrally-maintained spectrum data bases


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Comparative Analysis of AOMDV, AODV, DSR and DSDV Routing Protocols for Cognitive Radio 3

Local Spectrum Knowledge - Routing schemes based on local spectrum knowledge include all those solutionswhere information on spectrum availability is locally constructed at each secondary user through distributed

protocols. So here the routing module is tightly coupled to the spectrum management functionalities.

In [6] the unique features of CRN are better characterized by using new routing metrics, including Routing for

CRNs using IEEE 802.11 which are the official standards for wireless communication. Numerous simulations of routing

protocols have been made using different simulators, such as ns-2.The impact of sensing time, route path and mobility in

Ad- Hoc networks on connectivity and throughput tested.

In [7] a spectrum and energy aware on-demand protocol for routing and channel-timeslot assignment in multihop

CRANs. This protocol balances the traffic load among different CR users according to their nodal residual battery energy

and prolongs the lifetime of individual CR user and the overall networks. Simulation results in [6] show that the proposed

SER protocol can provide a lower end-to-end packet delay and routing overhead but ensure the higher throughput and

longer network lifetime.

In [8] a survey of routing protocols for mobile Cognitive Radio Ad Hoc Networks (MCRAHNs) is presented.

They propose the use of GYMKHANA Protocol based on Connectivity and Spectrum and Energy Aware Routing Protocol

based on Spectrum Awareness. Though most of the protocols of Mobile Cognitive Radio Ad hoc networks are found

common in wireless networks, there is a need to design new metrics to show the uniqueness of Cognitive radio ad hoc

networks.

ROUTINGPROTOCOLS

Ad-Hoc on-Demand Distance Vector (AODV)

AODV is an on Demand routing protocol which is confluence of DSDV and DSR. Route is calculated on

demand, just as it is in DSR via route discovery process. AODV is a relative of the Bellmann-Ford distant vector

algorithm, but is adapted to work in a mobile environment.

Each AODV router is essentially a state machine that processes incoming requests from the network entity.

AODV determines a route to a destination only when a node wants to send a packet to that destination. Routes are

maintained as long as they are needed by the source. Sequence numbers ensure the freshness of routes and guarantee the

loop-free routing. Whenever an AODV router receives a request to send a message, it checks its routing table to see if a

route exists. Each routing table entry consists of the following fields:

Destination address Next hop address Destination sequence number Hop count

If a route exists, the router simply forwards the message to the next hop. Otherwise, it saves the message in a

message queue, and then it initiates a route request to determine a route. AODV nodes use four types of messages to

communicate among each other.

Route Request (RREQ) and Route Reply (RREP) messages are used for route discovery. Route Error (RERR)

messages and HELLO messages are used for route maintenance. The following flow chart illustrates this process:


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Figure 2: AODV Routing Process [8]

Dynamic Source Routing (DSR)

The Dynamic Source Routing (DSR) protocol is an on-demand routing protocol based on source routing. In the

source routing technique, a sender determines the exact sequence of nodes through which to propagate a packet. The list of

intermediate nodes for routing is explicitly contained in the packets header. In DSR, every mobile node in the network

needs to maintain a route cache where it caches source routes that it has learned. When a host wants to send a packet to

some other host, it first checks its route cache for a source route to the destination. In the case a route is found, the send er

uses this route to propagate the packet. Otherwise the source node initiates the route discovery process. Route discovery

and route maintenance are the two major parts of the DSR protocol.

Destination Sequenced Distance Vector (DSDV)

DSDV is adapted from the conventional Routing Information Protocol (RIP) to ad hoc networks routing. It adds a

new attribute, sequence number, to each route table entry of the conventional RIP. Using the newly added sequence

number, the mobile nodes can distinguish stale route information from the new and thus prevent the formation of routing

loops.

In DSDV, each mobile node of an ad hoc network maintains a routing table, which lists all available destinations,

the metric and next hop to each destination and a sequence number generated by the destination node.

Each node of the ad hoc network updates the routing table with advertisement periodically or when significant

new information is available to maintain the consistency of the routing table with the dynamically changing topology of the

ad hoc network.

Periodically or immediately when network topology changes are detected, each mobile node advertises routing

information using broadcasting or multicasting a routing table update packet. The update packet starts out with a metric of

one to direct connected nodes. This indicates that each receiving neighbor is one metric (hop) away from the node. It is

different from that of the conventional routing algorithms. After receiving the update packet, the neighbors update their

routing table with incrementing the metric by one and retransmit the update packet to the corresponding neighbors of each


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of them. The process will be repeated until all the nodes in the ad hoc network have received a copy of the update packet

with a corresponding metric.

If a node receives multiple update packets for a same destination during the waiting time period, the routes with

more recent sequence numbers are always preferred as the basis for packet forwarding decisions. If the update packets have

the same sequence number with the same node, the update packet with the smallest metric will be used and the existing

route will be discarded or stored as a less preferable route. In this case, the update packet will be propagated with the

sequence number to all mobile nodes in the ad hoc network.

Delaying the advertisement of possibly unstable route can damp the fluctuations of the routing table and reduce

the number of rebroadcasts of possible route entries that arrive with the same sequence number.

Ad-Hoc on-Demand Multipath Distance Vector (AOMDV)

AOMDV routing protocol is an extension to the AODV protocol for computing multiple loop-free and link

disjoint paths [9]. The routing entries for each destination contain a list of the next-hops along with the corresponding hop

counts. All the next hops have the same sequence number. This helps in keeping track of a route. For each destination, a

node maintains the advertised hop count, which is defined as the maximum hop count for all the paths, which is used for

sending route advertisements of the destination. Each duplicate route advertisement received by a node defines an alternate

path to the destination. Loop freedom is assured for a node by accepting alternate paths to destination if it has a less hop

count than the advertised hop count for that destination. Because the maximum hop count is used, the advertised hop count

therefore does not change for the same sequence number [11]. When a route advertisement is received for a destination

with a greater sequence number, the next-hop list and the advertised hop count are reinitialized. AOMDV can be used to

find node-disjoint or link-disjoint routes. To find node-disjoint routes, each node does not immediately reject duplicate

RREQs. Each RREQs arriving via a different neighbor of the source defines a node-disjoint path. This is because nodes

cannot be broadcast duplicate RREQs, so any two RREQs arriving at an intermediate node via a different neighbor of the

source could not have traversed the same node. In an attempt to get multiple link-disjoint routes, the destination replies to

duplicate RREQs, the destination only replies to RREQs arriving via unique neighbors. After the first hop, the RREPs

follow the reverse paths, which are node disjoint and thus link-disjoint. The trajectories of each RREP may intersect at an

intermediate node, but each takes a different reverse path to the source to ensure link disjointness [9]. The advantage of

using AOMDV is that it allows intermediate nodes to reply to RREQs, while still selecting disjoint paths. But, AOMDV

has more message overheads during route discovery due to increased flooding and since it is a multipath routing protocol,

the destination replies to the multiple RREQs those results are in longer overhead

PROPOSED SCHEDULING SYSTEM

We have reviewed various protocols for cognitive ad-hoc network and the comparison of four chosen algorithms

is presented in the table below in order to try to find out the best protocol for a given QoS requirement:

Table 1: Comparison of Protocols

ProtocolRoute

Recovery

Spectrum

Sensing

Channel

Assignment

Delivery

Rate

Packet

Delay

AODV Yes Yes Yes Good Medium

DSDV Yes Yes Yes Very Good Less

AOMDV Yes Yes Yes Excellent Less

DSR No No Yes Poor More

CPR No Yes Yes Good Medium


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CONCLUSIONS

In this paper, we have proposed various routing techniques for cognitive radios. Moreover, our research work

would be mainly focused on improving routing techniques for Cognitive radios via multipath, cluster based, secure, and

low latency routing techniques. This would include, but not limited to using AOMDV, LEACH, SPAN and other

protocols, while for security we would be using AES, DES, RSA, ECC, and for reducing the delay we would be opting for

compression techniques like LZW, Zipping, and more.

This would help us to identify the best routing technique combination for a given application when using

cognitive radios, which is the main objective of our research

REFERENCES

1. Akyildiz, I. F., Lee, W. Y., and Chowdhury, K. R., CRAHNs: Cognitive Radio Ad Hoc Networks, Ad HocNetworks (Elsevier) Journal, to appear, vol. 7, July 2009.

2. Force, F. S. P. T., Report of spectrum efficiency working group. Avaiable: First note and Order, FederalCommunications Commission, ET-Docket 98-153, Adopted February 14, 2002, released April 22, 2002.

3. F. Brouwer, M. de Graaf, H. Nikookar, F. Hoeksema, "Adaptive Ad-hoc Free Band Wireless Communications",Project plan for AAF, Twente, 19 May 2004.

4. R. W. Brodersen, A. Wolisz, D. Cabric, S. M. Mishra, D. Willkomm, CORVUS: A Cognitive Radio Approachfor Usage of Virtual Unlicensed Spectrum, University of California, Berkley, 2004.

5. Matteo Cesana, Francesca Cuomo and Eylem Ekici, "Routing in cognitive radio networks: Challenges andsolutions", Ad Hoc Networks 2010, www.elsevier.com/locate/adhoc.S

6. Prof.Shubhangi Mahamuni, Dr.Vivekanand Mishra and Dr.Vijay M.Wadhai,"Performance Evaluation of AODVRouting Protocol in Cognitive Radio Ad-hoc Network", International Journal of Wireless & Mobile Networks

(IJWMN) Vol. 3, No. 5, October 2011.

7. S. M. Kamruzzaman, Eunhee Kim, Dong Geun Jeong, "Spectrum and Energy Aware Routing Protocol forCognitive Radio Ad Hoc Networks", IEEE ICC 2011.

8. S. Selvakanmani and Dr. M. Sumathi, Overview and literature survey on routing protocols for mobile cognitiveradio ad hoc networks, Computer Science & Information Technology, CS & IT-CSCP 2012

9. Royer E.M. Perkins C.E. Ad-hoc on-demand distance vector routing. Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications, p.90, 1999.

10. H.D.Trung, W.Benjapolakul, P.M.Duc, "Performance evaluation and comparison of different ad hoc routingprotocols", Department of Electrical Engineering, Chulalongkorn University, Bangkok, Thailand, May 2007

11. Z. J. Haas and M. R. Pearlman, "The Performance of Query Control Schemes for the Zone Routing Protocol",ACM/IEEE Trans. Net. 9 (August 2001).

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1. Comparative Analysis -Full