modeling of mobile adhoc networks using

P. Victer Paul et. al. / International Journal of Engineering Science and Technology Vol. 2(6), 2010, 2241-2247

MODELING OF MOBILE ADHOC NETWORKS USING DISTRIBUTED SPANNING TREE APPROACH P. VICTER PAUL

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T.VENGATTARAMAN

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P. DHAVACHELVAN

R. BASKARAN

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* Department of Computer Science, Pondicherry University, Puducherry, India. Department of Computer Science and Engineering, Anna University, Chennai, India.

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{victerpaul, vengat.mailbox, dhavachelvan, baskaran.ramachandran}@gmail.com Abstract Mobile ad hoc networks (MANETs) are a collection of distributed nodes which communicate using multi-hop wireless links with frequent node mobility. The frequent mobility of nodes leads network partition and futile communication. So, there need an interconnection technique that should guarantee network connectivity, efficient routing and maintain network performance in MANET. Distributed Spanning Tree (DST) is a well known interconnection technique in which nodes of MANET are made to form a forest of spanning trees in a distributed fashion which improves network connectivity and reduces the bottleneck. In this paper, we propose a distributed algorithm to formulate of DST in MANET with respective constraints. Analysis from simulation of our proposed work shows that DST technique improves network connectivity, routing and maintains network performance in MANET. Keywords: MANET, distributed spanning tree, communication, distributed algorithm, OMNeT++ 1.

Introduction

A "mobile ad hoc network" (MANET) is an autonomous system of mobile nodes connected by wireless links - the union of which forms an arbitrary graph. The nodes are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably [3]. These networks are advantageous in that, they have unique features of self-organized networks. They (MANETs) operate without fixed pre-configured infrastructure and have no central administration. Communication amongst nodes may go through consecutive multi-hop wireless links [2]. Each node in the network is a destination and a relay station for packets. MANETs have numerous applications such as sensor networks, disaster relief, military operations, business and home applications (Ramanathan and Rosales, 2000) [1]. MANET deploys nodes in a dynamic environment with unlimited abilities to span the wired and wireless Internet access. Thus a mechanism needed to manage the network due to the frequent topology changes to ensure effective communication in the network. LAN WANG [4] proposed that Clustering in large-scale MANET as a means of achieving scalability through a hierarchical approach in which every node in the cluster is one hop away from every other node, that is; each cluster is a diameter-1 graph. But static Cluster Head (CH) may easily become the traffic bottleneck and single point of failure of the cluster [5]. An important problem in a MANET is finding and maintaining efficient routes since host mobility can cause topology changes [6]. On considering routing in MANET, Factors such as variable wireless link quality, propagation path loss, fading, multi-user interference, power expended, and topological changes, become relevant issues. The network should be able to adaptively alter the routing paths to alleviate any of these effects [7]. From these perspectives, to alleviate various network connectivity and routing issues, Distribute Spanning Tree (DST) interconnection would be the better solution. DST structure is organized into a hierarchy of groups. The nodes are put together in groups and groups are gathered in groups of higher level, recursively. This organization, built on top of routing tables allows the instantaneous creation of spanning trees rooted by any nodes and keeps the load balanced between the nodes [8][9]. Thus we propose an efficient technique to formulate DST in MANET for effective routing and network performances and analyzed efficiency improved in node search application [12].

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Interconnection Structure Used

Distributed Spanning Tree (DST) [10,11] is the interconnection formation we follow which, improve the routing and reduce the number of message passes required for any communication in MANET. DST systematize MANEt into a hierarchy of groups of nodes. The nodes are put together in groups recursively. This systematization is built on top of routing tables allows effective routing in MANET. The DST is an overlay structure designed to be scalable [9]. The DST is a tree without bottlenecks which automatically balances the load between its nodes. So we virtually convert the MANET into DST and each tree should have its root node we call it as Head Node (HN) and others are Leaf Node (LN). Every LN will hold the details of its own HN. Likewise every HN will hold the complete details regarding its LNs and all other HNs in the network. The details stored in HNs and LNs in the DST is used to enhance the efficient routing with minimum message pass. During the formulation of DST in MANET, LNs and HNs are chosen randomly and dynamically with some requirement criteria which improve the Fault Tolerance of the system. 3.

Formulation of DST

3.1 DST formulation Algorithm In MANET network, formation of DST is complex. Fig. 2 shows a MANET and Fig. 3 shows the Peer Network representation of MANET in Fig.2 using which we will explain the DST formation on the network. In the network each node is indexed (id) i.e., 1, 2, 3…, n where n is the number of nodes in the network. The basic assumptions followed in the algorithm design,     

Each node has limited power (battery) transmission. Each node has a sense of direction of incoming signals from the neighborhood Each node has a unique id, which can be the MAC layer address. Each node broadcasts; each node was capable of hearing, receiving and replying with acknowledgment. Each node is a router. That is, each node is both a relay and a receiving station.

We propose a distributed algorithm as DST Algorithm for DST formation in MANET. The DST Algorithm is presented as in Fig. 1. This algorithm uses five procedures. Firstly DST_initialize() is a procedure which initializes DST by creating Head Node (HN) in MANET based on some test criteria. The criteria to be checked can be user approval, traffic on a particular region, etc., and the procedure creates an array on each HN to hold its LN details. If the criteria fail a variable on the node is created. Each HN is provided with unique Priority Number (PN) to provide write priority among the HNs. DST_initialize() also set HN id field of node as their own id and then it calls the procedure DST_probe(). The procedure DST_probe(), which is called by every HN creates probe message and set ‘id’ field of message as its own id and flood the message to all nodes it is connected. On receiving a message every node execute the procedure DST_receive(msg) where ‘msg’ is the received message. During DST formation it should be possible to get any one of the two types of messages, the probe message or reply message: If there is a probe message, any one of the following would be occurred: Case-1: If the message is received by a HN, then it is just discarded. Case-2a: If the message is received by a LN which is not under any HN, then LN stores the Head variable as the id which it read from pmsg. Then call the procedures DST_reply(N(id)) and DST_forward(pmsg). Case-2b: If the message is received by a LN which is under any HN then it just discard the message. If there is a reply message, any one of the following would be occurred: Case-1: If the message is received by a LN, then it just forwards it to the node bearing the id ‘id’. Case-2: If the message is received by a HN, then it reads ‘dest’ from ‘rmsg’, if ‘dest’ equals N(id) it shows required HN is reached. It read ‘id’ from ‘rmsg’ and add it to its array, otherwise it is forwarded to N(id).

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procedure DST_initialize () if (test criteria) N(i) is Head Node where i=1….n array a[n] // to hold its leaf node details N(i).setHead(N(i)) assign unique Priority for N(i) probeDST() else variable head end procedure

procedure DST_probe() for j = 1 to m // where m is no. of peers // within the range of N(i) create probe message pmsg set pmsg.id = N(i) send(pmsg, m) // flooding the probe end for end procedure

procedure DST_receive(msg) if(msg = = pmsg) cast msg to pmsg if(N(i) = = Head Node) delete(pmsg) else if(N(i) is under any Head Node) delete(pmsg) else id = pmsg.getId N(i) is under N(id) N(i).setHead(N(id)) probe_reply_DST(N(id)) probe_forward_DST(pmsg) end if end if else if(msg==reply) cast msg to rmsg if(N(i) != Head Node) send(rmsg,N(id)) else dest = rmsg.getDest if(dest==N(i)) id = rmsg.getId a.add(id) else send(rmsg,N(id)) end if end if end if end procedure

procedure DST_reply(N(id)) create reply message rmsg set rmsg.id = N(i) set rmsg.dest=N(id) send(rmsg, N(id)) end procedure

procedure DST_forward(pmsg) for j = 1 to m-1 // where m is no. of peers within the range of N(i) // except peer from where it received probe copy pmsg message send(pmsg, m) end for end procedure

Fig.1 Proposed DST Algorithm

Procedure DST_reply(N(id)) is called by LN to reply to its HN. The LN creates a reply message. The ‘id’ and ‘dest’ fields of the reply message is set to be, the ‘id’ of the LN and the ‘id’ of the HN respectively. After the reply message sent to HN, the LN calls the Procedure DST_forward(pmsg) to flood the probe message to all the nodes except the node from where it was received. After the completion of these five procedures the MANET will be in required DST structure.

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P. Victer Paul et. al. / International Journal of Engineering Science and Technology Vol. 2(6), 2010, 2241-2247 Definition 1: Let Gm be the Node Network graph based on the formation of HN and LNs. Then Gm can be represented as,

DST1 DST2 . DSTk

Gm =

HN1, LN1, LN2, LN3 …. LNj h HN2, LN1, LN2,LN3 …. LNj . . . . HNi, LN1, LN2,LN3 …. LNj

=

(1)

where,  ‘Gm’ is graph of MANET with ‘m’ nodes.  ‘HN’ is the Head Node (HN). ‘i’ is the number of HN formed in the MANET.  ‘LN’ is the Leaf Node (LN). ‘j’ is the number of LN formed under every HN in the MANET.  ‘DST’ is the Distributed spanning Tree formed in MANET. ‘k’ is the number of DSTs formed in MANET and ‘i’ equals ‘k’. Thus the graph of MANET (Gm) of ‘m’ nodes is organized into ‘k’ DSTs. Each DST consist of a HN and ‘j’ number of LNs corresponding to the HN. 3.2 Illustration for DST Formulation To elucidate the DST Algorithm in real time example, Fig. 2 shows a MANET in which a collection of nodes are connected in graph fashion. Each node has its identification number (id) which can be MAC or IP Addresses. Fig.3 shows the MANET after initialize_DST() procedure call, during which node 1, 6 and 18 satisfies the test condition and changed as HN. It then floods its probe message (pmsg).

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Fig. 3 Peer Network representation of MANET in Fig. 2

When nodes receive the probe message, it comes under the HN from which it was received and floods it out. Fig.4 shows nodes 8 and 12 get probe message from node 1. It saves their HN id as 1 and then acknowledge to its HN (node 1) and also floods the probe message to all the node it connected except to the sender (node 1).The same happens in nodes 4,5,9,7,17 and 15. The probe message from node 8 is received b y nodes 2 and 13 and acknowledged to node 1 and flooded. Likewise nodes 3 and 10 come under HN 6 and node 14 and 11 come under HN 18 as shown in Fig.5. The notable thing is that the node 15 forwards the probe message to 11 and 9, but node 9 is already under HN 6. So, it just deletes the probe instead of processing the message. Fig.6 shows the complete HN and LN formation in the MANET. Fig.7 shows the DST form of the MANET with HN and their corresponding LNs.

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Fig.4 DST form of MANET

Thus MANET in Fig.2 is virtually converted into hierarchical network in Fig.4 using DST Algorithm. We are going to use this DST interconnection to reduce the message passes required for communication in MANET. 4.

Simulation and Analysis

This section describes the simulation results obtained during the investigation phases. We used OMNeT++, an object-oriented modular discrete event network simulator. A MANET with 100 nodes (identified as comp1, comp2, comp3 …comp100 in simulation) interconnected randomly and spread in some distant geographical location as shown in Fig.5 is used to validate our proposed techniques. It is assumed that the medium have propagation delay of 100 ms.

Fig.5 Simulated MANET in OMNeT++ Simulator

In our simulation setup of MANET with one hundred systems, number of messages required to formulate DST is nearly equals 412 messages which takes nearly 6.39 seconds (with channel Propagation Delay as 100ms) for the formation of complete DST as in Fig.4. On reducing the delay by 10ms will reduce the time taken as 0.639 seconds. Fig. 6 and Fig. 7 shows number of messages required by each node to form DST. In simulated DST, the HNs are comp04, comp18, comp36, comp54 and com93, obviously other nodes act as LN for any of these HN. For our simulated DST, Eq. (1) can be rewritten as, DST1

comp04, comp01, comp02….. compj

DST2

comp18, comp11, comp32….. compj

DST 3

=

(2)

comp36, comp24, comp23….. compk

DST 4

comp54, comp61, comp62….. compl

DST5

comp93, comp93, comp97….. compm

where,  ‘i’,’j’,’k’,’l’ and ‘m’ are the number of nodes in DST1, DST2, DST3, DST4 and DST5 respectively.  column 2 and column 3 nodes are LNs for HN given in column 1.

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The exact values of i, j, k, l, m and n in our simulation are 20, 14, 35, 12 and 17 respectively and these values show that the LNs are not uniformly distributed among the HNs which means that the number of LNs under some HN depend on various criteria like distance between them, channel capacity, congestion on that area, user approval, number of LNs under a HN and so on. With this, formulation of DST in the MANET completes and network ready for user application in which throughput can be improved by the technique.

No of messages required to form DST 7 6 5 4 3 2 1 0

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From Table 1, it is clearly evident that the DST technique reduces the number of message passes required for communication and the route table entries. Thus simulation results shows the efficiency of various applications in MANET are improved nearly 14% to 21%. Table I. Comparison Table for various Factors between MANET and MANET with DST

 

S.No

Criteria to Measure

MANET

DST MANET

1

No. of Messages created to formulate the technique

N/A

412

2 3 4

Time taken to formulate the technique (in sec) Average routing table entries required by a node Efficiency of Node search application

N/A ‘N’ 67%

6.39 ‘N/M’ 81%

‘N’ is the number of nodes in MANET. ‘M’ is the number of DSTs formed in the MANET.

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Conclusion and Future work

The work presented in this paper has described an effective approach to guarantee network connectivity, efficient routing and maintain network performance in MANET using DST models. The proposed models are proved in terms of reduced routing table entries and number of message passes. From the simulation analysis, it is shown that time taken for formulation of DST in MANET using the proposed algorithm is very small and effective in routing and cost reduced communication. As part of future work, we plan to apply enhanced technique using Ant Colony Optimization (ACO) to optimize the DST formulated in MANET for better performance. References [1] Ramanathan, R. and Rosales - Hain R. (2000) Topology Control of Multi hop Wireless Networks Using Transmit Power Adjustment Proc. IEEE INFO. COMM. [2] OPIYO NOCKLINE (2005), “Distributed Topology Control For Mobile Ad Hoc Networks: Exploring The P/ NP Boundary”, A Dissertation Submitted to Makerere University School of Graduate Studies. [3] http://www.saching.com/Article/MANET---Mobile-Adhoc-NETwork--/334 [4] Lan Wang and Stephan Olariu, “Cluster Maintenance in Mobile Ad-hoc Networks”, Springer Science + Business Media, Inc. 2005. [5] P. Krishna, M. Chatterjee, N. Vaidya and D. Pradhan, A cluster-based approach for routing in ad-hoc networks, ACM SIGCOMM Computer Communication Review 27(2) (1997) 49–64. [6] Azzedine Boukerche, “Algorithms And Protocols For Wireless And Mobile Ad Hoc Networks”, Wiley Series On Parallel And Distributed Computing Copyright © 2009 by John Wiley & Sons, Inc. [7] Mobile Ad Hoc Networks (MANETs), http://w3.antd.nist.gov/wahn_mahn.shtml ,Web site owner: The National Institute of Standards and Technology . [8] Sylvain Dahan, Jean-Marc Nicod and Laurent Philippe, The Distributed Spanning Tree: A Scalable Interconnection Topology for Efficient and Equitable Traversal, International Symposium on Cluster Computing and the Grid, 2005 IEEE. [9] Sylvain Dahan, Distributed Spanning Tree Algorithms for Large Scale Traversals, 11th International Conference on Parallel and Distributed Systems (ICPADS'05), 2005 IEEE. [10] Sylvain Dahan, Jean-Marc Nicod and Laurent Philippe, The Distributed Spanning Tree ,IEEE transactions on parallel and distributed systems, vol. 20, no. 12, december 2009 [11] A. Rowstron and P. Druschel, “Pastry: Scalable, Decentralized Object Location, and Routing for Large-Scale Peer-to-Peer Systems,” Proc. IFIP/ACM Int’l Conf. Distributed Systems Platforms, vol. 2218, pp. 329-350, 2001. [12] Mengkun Yang Zongming Fei, Assigning Identifications to Nodes in Unstructured Peer-to-Peer Networks: A Novel Approach to Improving Search Efficiency, Global Telecommunications Conference, 2007.GLOBECOM '07.IEEE.

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