OPTIMAL CONFIGURATION FOR NODES IN MIXED CELLULAR AND MOBILE AD HOC NETWORK FOR INET

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1 OPTIMAL CONFIGURATION FOR NODE IN MIED CELLULAR AND MOBILE AD HOC NETWORK FOR INET Olusola Babalola D.E. Department of Electrcal and Computer Engneerng Morgan tate Unversty Dr. Rchard Dean Faculty Advsor ABTRACT As part of Morgans NET development, the Mxed Cellular and Moble Ad hoc Networ (MCMN) archtecture has been proposed to provde coverage to over-the horzon test artcles. Nodes n MCMN are assgned to one of three possble modes- Ad hoc, Cellular or Gateway. We present archtecture for the proposed MCMN and some performance analyss to characterze the networ. The problem of organzng nodes n ths mxed networ wth optmal confguraton s sgnfcant. Ths confguraton gves nodes ablty to now the best mode to operate and communcate wth other nodes. Node organzaton s crtcal to the performance of the mxed networ and to mprove communcaton. The confguraton of nodes requred to optmally organze nodes n MCMN s demonstrated. The problem of evaluatng confguraton parameters for nodes n a mxed networ s a nonlnear and complex one. Ths s due to the varous components le the number of nodes, geographcal locaton, sgnal strength, moblty, connectvty and others that are nvolved. Clusterng technques and algorthms have been used n lterature to partton networs nto clusters to support routng and networ management. A clusterng technque s employed to dynamcally partton the aggregate networ nto Cluster Cells (CCs). A gateway node s selected for each CC whch relays traffc from the cellular to the Ad hoc and vce versa. A trade-off analyss of the cellular boundary s presented usng the maxmum of the mnmum data rate n the networ. Numercal analyss and experments are provded to show that the coverage can be extended to test artcles n over-the-horzon regon. It s also shown that, when the networ s well organzed, performance s mproved. KEYWORD MANET, cellular, coverage, throughput capacty, Ad Hoc, NET The choce of a cellular/ad hoc structure precedes INETs choce of an IEEE8. model. Ths wor stll apples wth the assumpton that the WLAN Access Pont substtutes for the cellular base staton.

2 INTRODUCTION MCMN was proposed after a comparson study of ad hoc and cellular networs []. In mxed or hybrd networs concept, the cellular networs and moble ad-hoc networs nteroperate to form an aggregate networ. Advancements n technology have revealed the feasblty of the proposed soluton by usng the emergng dual-mode nterface to equp nodes. Ths allows nodes to communcate n one of the three possble modes. These modes are ad hoc mode (AHM), cellular mode (CM) and gateway mode (GM). Ths concept provdes moble nodes more flexblty and system performance enhancement by provdng seamless roamng between cellular networs and ad hoc networs. Ths research focuses on an effcent way of computng the confguraton for each node n a mxed networ. Ths ncludes ther CC dentty, gateway node to relay ther traffc, and nformaton about other nodes n the networ. As routng schemes are mportant to effectvely route traffc n the networ, ths wor wll nclude technques for routng wthn each cluster and routng between the cellular and MANETs. The CC to whch a node belongs s evaluated based on the nformaton sent to the Base taton (B) by the node. The focus n ths wor s the aeronautcal envronment where nodes have hgh moblty, reduced path loss due to free space or lne of sght communcaton, and hgh coverage areas. The frst secton presents the MCMN archtecture; the next secton presents performance analyss n terms of throughput and coverage. The last secton presents node organzaton scheme usng a -stage clusterng technque. Numercal analyss s presented to valdate the performance of the networ and a concluson s gven. MCMN ARCHITECTURE The MCMN s a pure hybrd networ when compared wth most of the other proposed hybrd networs [, 3]. In MCMN, both cellular and ad hoc communcatons are possble. Ths means that both cellular and ad hoc nodes can orgnate and receve data. MCMN also ncludes the ad hoc mode (AHM) nodes, these nodes communcate n mult-hop mode and they dynamcally route ther own traffc usng standard routng protocols le AODV, DR, and DDV. For Nodes operatng n CM to contnue communcaton n the networ they swtch to AHM (mult-hop) when ther sgnal strength drops to a certan threshold. Ths s smlar to the hand-over process n a conventonal cellular system. The dfference s that, whle a node searches for another B to connect to n cellular networs, nodes n MCMN search for an alternate mode or route usng ther other nterface (ad hoc nterface). A thrd category of nodes n MCMN s the gateway node (GN). These nodes are capable of communcatng n both cellular and ad hoc mode smultaneously and they relay cellular traffc to ad hoc and vce versa. The NET scenaro s llustrated n fgure where Test Artcles (TA) collect data and send them to ground systems for further processng. The words nodes and TAs are used nterchangeably for the rest of ths paper to refer to wreless termnals. The fgure shows TAs communcatng n AHM as well as CM usng both the ad hoc and cellular technologes for communcaton. TAs are grouped nto K MANETs CCs. Each CC has ts own GN to relay traffc between the cellular and MANET nodes n the CC. The B s located at the center of the cellular networ (sngle cell cellular system), and K CCs are located around t as shown n fgure. The GNs can be a

3 bottlenec n the networ so the choce of GNs s crtcal to the performance of MCMN. Every node can become a GN dependng on ts confguraton. It s also assumed that each node s aware of ts geographcal locaton through GP or other postonng mechansm. Ad-hoc Node Cluster cells Gateway node Gateway node Base taton Cellular Nodes Fgure MCMN Archtecture Ad hoc Networ Cluster Cells Gateway Nodes Base taton Cellular Nodes Fgure MCMN Layout The archtecture and protocol stac for a node n MCMN s presented n fgure 3 below. The two nterfaces use the same upper layers applcaton, transport, and networ. The networ layer plays the role of nterfacng between the lower layers and upper layers. The networ layer s also responsble for the complex tas of routng between the two dfferent nterfaces wth consderaton of moblty and connecton management. Every node n the networ s equpped wth dual nterface as shown n fgure 3. Any node n the networ can become a gateway at any tme dependng on ts geographcal locaton, sgnal strength and proxmty to both the B and ad hoc nodes. GNs communcate usng the two nterfaces smultaneously as shown n fgure 4. Ths s a more complex tas because t ntegrates the two technologes and also deals wth the routng problems. Every CC can have one or more GNs, but for ths analyss and smplcty, t s assumed that every CC has one GN for relayng traffc. 3

4 Applcaton Transport Networ CM Ln CM MAC CM-PHY AHM Ln AHM-MAC AHM-PHY Cellular Interface Ad hoc Interface Fgure 3 Archtecture of MCMN Node Cellular Node Gateway Node Ad hoc Node Applcaton Applcaton Transport Networ Transport Networ Ln Control MAC PHY CM-LLC CM-MAC CM-PHY AHM-LLC AHM-MAC AHM-PHY Networ Ln Control MAC PHY Cellular Interface Ad hoc Interface Fgure 4 Archtecture of MCMN Gateway Node Based on the node organzaton and groupng (next secton), the B develops a confguraton table for all nodes n the networ. The B bulds up a routng table and sends the routng nformaton of every node n each CC to the GNs respectvely; every node n the networ s attached to GN for ts CC. GNs eep and mantan the routng nformaton, and share t among other GNs. In addton, each GN forwards the routng nformaton of all nodes n ts CC to every member of the cell. Usng ths nformaton every node n the same CC can communcate wth one another wthout necessarly passng through GN. To communcate wth the nodes outsde the CC or CM node, a node wll have to transmt through the GN. Even though a node cannot communcate wth nodes outsde ts CC, every node can receve where do I belong (WDIB) message from other nodes. Ths message s meant for the B and contans node parameters that wll be used to compute ts confguraton; every node can receve and forward the WDIB message untl t arrves at the destnaton whch s the B. PERFORMANCE ANALYI Two common networ performance metrcs are coverage and throughput. These have been extensvely covered n lterature for the cellular and ad hoc networs separately. Coverage s defned as the geographcal area n whch successful communcaton can be provded. For 4

5 MCMN, the coverage provded by the of MCMN. Estmaton for the overall coverage s gven as: K Cov Cov Cov Where s a constant reflectng the border effect whch s due to the fact that CCs are nonoverlappng [4]. The CCs wth MCMN th CC results n a cumulatve effect on the total coverage cellular NCC Cov cellular s the cellular coverage, Cov N CC s the coverage provded by nodes n each CC. Throughput s defned as the aggregate amount of data that can be successfully transported n a networ over tme. The GN s assumed to be a super user and can have more tme slots from the B to accommodate demand. The B montors the demand on the GN and ncreases ts tme slots dynamcally. The overall throughput for MCMN s gven as: MCMN CM CM K CC K Where GN s the throughput of a GN, ( N GN CC CC ) f f Cellmax Cellmax N CC GN CC CC GN () () s the expected throughput n a CC wth NCC K CM s the throughput of the cellular networ. Detals of these analyses are provded n [5]. nodes, NODE ORGANIZATION IN MCMN The technque for groupng nodes n MCMN nto CCs (CCs) for optmum performance s developed n ths secton. Ths groupng of nodes s the ey to the overall performance of a MCMN networ. A method s presented to ntellgently form CCs, select nodes to be gateway nodes (GNs) for each of the CCs, and develop a scheme to evaluate the optmal number of CCs that wll be requred for the networ parttonng. Nodes are presented as ponts n a - dmensonal Eucldean space ( ) and nformaton about nodes n ths space s contaned n ther statstcs. Clusterng procedures use a crteron functon, such as the Eucldean dstance and sum of squared dstances from the cluster centers, and see the groupng that optmze the crteron functon [6]. A -stage clusterng scheme s used n MCMN to organze nodes n the networ; ths s shown n fgure 5a and 5b. The clusterng s done by the B after collectng the requred nformaton from nodes n the networ. In ths analyss, only dstnct clusters are consdered wth each node n a CC havng a GN to connect to the cellular nodes as well as nodes n other CCs. The use of clusterng for organzng nodes n MCMN offers several advantages. It mproves manageablty, ncreases throughput, reduces overhead and mnmzes networ congeston among other advantages. Every node s assumed to have the nowledge of ts geographcal locaton. Every node transmts ts Y geographcal locaton to the B where centralzed coordnaton and management of the networ taes place. 5

6 Ad hoc Nodes tart tart cale Parameters Geographcal Locaton Parameters Radus, Angle Compute NR Intal Centrod Number of Clusters Compute Dstance from Centrod Thresh old > Cellular Nodes Group nodes usng mnmum dstance No < Compute new centrod Ad hoc Nodes End Compute Error Conv erge? Yes End Fgure 5a tage One Fgure 5b tage Two To organze nodes n MCMN, two heterogeneous parameters are defned for every node the radus and angle. Radus measures the dstance of each node from the B (Centre of networ) whle the angle measures the spatal locaton of each node. It has been assumed that the radus and angle are unformly dstrbuted. The radus R and angle of node are gven as: R Y Y (3) Y Y tan (4) Where Y represent the geographcal locaton of B whch s assumed to be the center of the networ. Usng the heterogeneous parameters defned above, clusterng parameter CPar s computed for each node n the networ. CPar R, N AHM (5) Where N AHM s the total number of ad hoc nodes n the networ. The clusterng parameter, CPar, can nclude as many parameters as possble and has been lmted to R and for smplcty. The frst stage nvolves usng the locaton nformaton and the path loss model of equaton (6) and (7) to compute the NR of every node from the B. Ths s a functon of the dstance from the B whch s the radus gven n equaton (3) above. The NR decreases as a functon of R where s the path loss exponent. A threshold s set for the NR and any node wth NR greater than the threshold s consdered a CM node and those wth NR less than the 6

7 threshold are consdered as AHM node. Ths procedure parttons the aggregate networ nto the two man components of MCMN- Cellular networ and ad hoc networ. Where P ( d ) r PG G t t r 4 d L P r d P r d and the NR, d d d d (6) n wreless communcatons s gven as P r or Pr L (7) L P are the receve and transmt powers respectvely. The Where Pr and t and transmt antenna gans, and L s the path loss Gven a parttonng of CCs, nto, the centrod, CC K, for each CC s defned as: The clusterng problem s defned as Where CPar s the clusterng parameter, cluster cell. G r and G t are receve, K beng the total number of CCs to partton the networ. R,,, (8) CC arg mn D CPar, (9) CPar CC CC s the th cluster cell, and s the centrod for NUMERICAL ANALYI AND REULT Ths secton presents some numercal analyses and experments usng MATLAB program. A MATLAB vsualzaton program s developed to vew the node organzaton. In addton, analyss s presented for gateway locaton and trade-off n the cellular boundary when the ad hoc component s dependent on the cellular component. A total of 4 nodes are randomly placed n a crcular regon wth the B located at the center of ths networ. The frst tas s to classfy the aggregate networ nto ether CM nodes or AHM nodes. Fgure 6 shows the randomly placed nodes n a gven area. Fgure 7 shows the parttoned networ after applyng the threshold for NR. It s seen that the whole networ s separated nto CM nodes and AHM nodes. A valdty measure s developed to obtan an estmaton for the optmal number of CCs, K, that the ad hoc nodes are dvded nto. Ths s gven as: wcler Valdty measure arg mn () excler Where wcler s the wthn cluster error, t measures the average of all dstances between a node and the centrod of ts CC, and t can be used to determne whether the CC s compact or not. The external error, excler, measures the relatonshp between the CCs that mae up a gven parttonng and s computed as the mnmum dstance between the centrods n parttonng. The 7

8 goal s to mnmze the valdty measure, the values of valdty measure for each K s plotted and the parttonng wth the mnmum value of valdty measure gves the optmum parttonng. The value of K for ths parttonng s the optmum number of CCs to partton the AHM nodes. The result s shown n fgure 8 and for the networ scenaro consdered n ths analyss, the value of valdty measure s mnmum at K = Fgure 6 Randomly Placed Nodes n MCMN -3 CM nodes AHM nodes Fgure 7 Parttoned Cellular and MANET To effectvely choose GNs n MCMN, smlar parameters used n parttonng the networ must be consdered n selectng approprate GNs. The B, n addton to performng the clusterng, computes the GNs selecton metrc, ngmetrc, for all actve nodes n a CC. Ths s gven as: w* NR j ngmetrc j N N CC CC () D node, node j D node, B N CC where D node, node j s the dstance between node and node j n the same CC, and D node, B s the dstance between node and the B. In addton to the dstances, the sgnalto-nose rato, NR, of nodes n the CC wth reference to one another s computed. Fgure 9 represents the complete MCMN system wth every node nowng the CCs they belong to n the networ and ther GN ID. Usng ths organzed networ, the B has detaled nformaton about all the nodes n the networ. The mnmum networ rate, R mn, s computed as the mnmum rate of cellular nodes, gateway node, and ad hoc node. Ths s represented as R mn arg mn RCM, RGM, RAHM () Where R CM, R GM, R AHM are the rates for cellular mode, gateway mode, and ad hoc mode. And fnally, the maxmum of the mnmum rate s used to defne the boundary for cellular and ad hoc 8

9 networ n MCMN. Ths represents the optmal locaton for the GNs and also the optmal boundary for cellular and ad hoc networs. Ths analyss has taen nto consderaton the dependency of the ad hoc networ on the capacty of cellular networ Number of clusters Fgure 8 Optmal Number of Cluster to Partton MCMN Fgure 9 Gateway Nodes for CCs Fgure shows the trade-off between rates and dstance from base staton for the dfferent components of MCMN. The fgure also shows the cellular and gateway throughput decreasng as the dstance from the B ncreases untl the optmum pont s reached and contnues to decrease at the mnmum rate. But because the networ s well organzed, the cellular node changes nto ad hoc mode and ts throughput begns to rse. x 4 ad hoc rate gateway rate cellular rate mnmum rate Gateway dstance from Base taton (dg) x 4 Fgure Trade-off for Boundary and Gateway Locaton 9

10 CONCLUION AND FUTURE WORK A soluton to the problem of coverage of nodes usng a mxed cellular and ad hoc networ has been presented. It has been shown that when combnng the features of tradtonal nfrastructurebased cellular networs wth that of ad hoc networs an mproved mxed networ can be formed. We have desgned a novel archtecture for our proposed MCMN. We presented both theoretcal and numercal analyss to evaluate the performance mprovement that MCMN can provde to a networ. It has been shown that coverage can be extended beyond the lmtaton of a cellular base staton. It has also been shown that throughput can be enhanced whle extendng the networ coverage. A soluton to the problem of organzng nodes n MCMN has been presented through a -stage clusterng scheme. The modfed K-means scheme ncorporates the nonhomogenety of networ nodes nto the networ parttonng. A soluton for choosng the optmum number of CCs to partton the ad hoc nodes nto was developed. A scheme for selectng gateway nodes to relay traffc from one cluster to another was developed. And fnally, the trade-off analyss n selectng the GN locaton and cellular boundary has been presented. The soluton easly adapts to NET system by ncorporatng NET chosen technologes to operate n multhop and sngle hop to form the MCMN. Ths wll enhance throughput and extend coverage to OTH TAs n NET. Fnally, t s mportant to acnowledge the support provded by NAVAIR wthout whch ths wor could not have happened. REFERENCE. Babalola, O. A., Performance Issues n Mxng Cellular and Ad hoc Networs for NET, ITC 5 Conference, Las Vegas, October 5.. H. Luo, R. Ramjee, P. nha, L. L, and. Lu, UCAN: A unfed cellular and ad-hoc networ archtecture, n Proc. MobCom, ept. 3, pp Hongy Wu; Chunmng Qao; De,.; Tonguz, O.; Integrated cellular and ad hoc relayng systems: CAR, IEEE Journal on elected Areas n Communcatons, Vol. 9, Oct., pp E. Wessten, Crcle-Crcle Intersecton From MathWorld A Wolfram Web Resource, June 4, /Crcle-CrcleIntersecton.html. 5. Babalola, O. A. Optmal Confguraton for Nodes n a Mxed Cellular and Moble Ad hoc Networs, Dssertaton, Dept. of Electrcal Engneerng, Morgan tate Unversty, Baltmore, Maryland, May R. Duda, P. Hart, D. tor, Pattern Classfcaton, nd Edton, New Yor, John Wley and ons,.