A Novel Decision Scheme for Vertical Handoff in 4G Wireless Networks

Transcription

1 a g e 28 Vol. 10 Issue 5 Ver. 1.0 July 2010 Global Journal of Computer Sene and Tehnology A Novel Deson Sheme for Vertal Handoff n 4G Wreless Networks Abstrat-Future wreless networks wll onsst of multple heterogeneous aess tehnologes suh as UMTS, WLAN, and W-Max. These tehnologes dffer greatly regardng network apaty, data rates, and oer varous parameters suh as power onsumpton, Reeved Sgnal Streng, and overage areas. Ths paper presents two Handoff Deson shemes for heterogeneous networks. A good handoff deson ould avod e redundant handoffs and redue e paket lose. Frst sheme makes use of a sore funton to fnd e best network at best tme from a set of neghborng networks. Sore funton uses bandwd, Reeved Sgnal Streng (RSS) and aess fee as ts parameters. Seond sheme makes use of lass trangle problem to fnd e best network from a set of neghborng networks. Ths problem onsders ree parameters bandwd, Reeved Sgnal Streng (RSS) and aess fee as e ree sdes of a trangle. If an equlateral trangle s obtaned w ese parameters of a network en at network wll be e best among e set of networks. The best deson model meets e ndvdual user needs but also mprove e whole system performane by redung e unneessary handoffs. Keywords-MIHF, Reeved Sgnal Streng, Moblty Management, vertal handoff, C I. INTRODUCTION urrently, ere are varous wreless networks deployed around e world. Examples nlude seond and rd generaton (3G) of ellular networks (e.g., GSM/GRS, UMTS, CDMA2000), wreless loal area networks WLANs (e.g., IEEE a/b/g), and personal area networks (e.g., Bluetoo). All ese wreless networks are heterogeneous n sense of e dfferent rado aess tehnologes. From s fat, t follows at no aess tehnology or serve provder an offer ubqutous overage expeted by users requrng onnetvty anytme and anywhere. The atual trend s to ntegrate omplementary wreless tehnologes w overlappng overage, to provde e expeted ubqutous overage and to aheve e Always Best Conneted (ABC) onept The ABC onept allows e user to use e best avalable aess network. In order to aomplsh e ntegraton and nter-workng between heterogeneous wreless networks and e ABC onept, many hallengng researh problems have to be solved, takng nto aount. About- 1 Assstant rofessor, Dept of Computer Sene & Engneerng, Noorul Islam Unversty, Thukalay, Taml Nadu, Inda (e-mal;arunsedly@yahoo.om) About- 2 Senor rofessor, Dept of Eletrons &Communaton Engneerng, Noorul Islam Unversty, Thukalay, Taml Nadu, Inda (e-mal;mon2006_r.s@yahoo.o.n) E. Arun 1 R.S Mon 2 GJCST Computng Classfaton C.2.1, F.4.2 at all ese new wreless tehnologes were desgned wout onsderng any nterworkng among em In heterogeneous wreless networks, moble deves or moble statons wll be equpped w multple network nterfaes to aess dfferent wreless networks. Users wll expet to ontnue er onnetons wout any dsrupton when ey move from one network to anoer. Ths mportant proess n wreless networks s referred to as handoff or handover. Handoff proess among networks usng dfferent aess tehnologes s defned as vertal handoff (VHO) [1]. Suh a proess of hangng e onnetons among dfferent types of wreless and moble networks s alled e vertal handoff. Obvously, e network seleton and e vertal handoff deson are two mportant proesses n an ntegrated wreless and moble network. Handoff proess s ntated by hange n dfferent fators lke Reeved Sgnal Streng (RSS), Sgnal to Nose Rato (SNR) et. When ese fators fall bellow e reshold value e Moble Node (MN) has to searh for anoer A havng RSS greater an reshold value [2, 3]. Wang et al. ntrodue e poly enabled handoff n [4], whh was followed by several papers on smlar approahes. oly enabled handoff systems separates e deson makng (.e. whh s e best network and when to handoff) from e handoff mehansm. Smart Deson Model [5] smartly performs vertal handoff among avalable network nterfaes. Usng a well-defned sore funton, e proposed model an properly handoff to e best network nterfae at e best moment aordng to e propertes of avalable network nterfaes, system onfguratons / nformaton, and user preferenes. A handoff deson sheme w guaranteed QoS [6] for heterogeneous networks make e deson aordng to e user s ommunatng types and e performane of e networks. A gener vertal handoff deson funton [7] proposed onsderng e dfferent fators and metr qualtes at gve an ndaton of wheer or not a handoff s needed. The deson funton enables deves to assgn weghts to dfferent network fators suh as monetary ost, qualty of serve, power requrements, personal preferenes et. A deson strategy [8] onsders e performane of e whole system whle takng VHO desons by meetng ndvdual needs. Ths deson strategy selet e best network based on e hghest reeved sgnal streng (RSS) and lowest Varaton of Reeved Sgnal Streng (VRSS). Thus t ensures e hgh system performane by redung e unneessary handoffs. Nasser et al. [9] proposed a VHO deson (VHD) meod at smply estmates e serve qualty for

2 Global Journal of Computer Sene and Tehnology Vol. 10 Issue 5 Ver. 1.0 July 2010 a g e 29 avalable networks and selets e network w e best qualty. However, ere stll le ahead many hallenges n ntegratng ellular networks and WLANs. Ths paper s organzed as follows. In Seton II, we ntrodue our proposed system model for an ntegrated wreless and moble network. In Seton III, dfferent handoff deson strateges are presented. In Seton IV, we analyze e performane of e proposed strategy. Fnally, we onlude s paper n Seton V. II. SYSTEM MODEL Fg 1 Vertal handoff n heterogeneous networks As shown n e above fgure an MN an be exstng at a gven tme n e overage area of an UMTS alone. However, due to moblty, t an move nto e regons overed by more an one aess network,.e., smultaneously wn e overage areas of, for example, an UMTS BS and an IEEE A. Multple IEEE WLAN overage areas are usually ontaned wn an UMTS overage area. A Worldwde Interoperablty for Mrowave Aess (WMAX) overage area an overlap w WLAN and/or UMTS overage areas. In dense urban areas, even e overage areas of multple UMTS BSs an overlap. Thus, at any gven tme, e hoe of an approprate attahment pont (BS or A) for eah MN needs to be made. These aess tehnologes have dfferent bandwd, power onsumpton, RSS reshold, data rate, jtter, delay et. So durng handoff t s requred to fnd e best network aordng to user preferenes. At e hotspots As are made avalable. When e Reeved Sgnal Streng of an A goes low below some reshold value e Moble Host has to fnd anoer best network onsderng bandwd, RSS, aess fee as parameters. Eah of ese parameters s gven a weght aordng to preferenes. If any of e best A s are not avalable handoff has to be performed to Base Staton of UMTS. Thus, multple aess tehnologes and multple operators are typally nvolved n Network Seleton Deson. The Network Seleton deson makng algorm s mplemented n Network seleton deson Controllers loated n aess networks. Deson nput for NSDCs wll be obtanable va e MIHF. The MIHF of NSDC faltates standard based message exhanges between varous aess networks or attahment ponts to share nformaton about e traff load, bandwd avalable, RSS and oer network apabltes of eah A. NSDC obtans LLT s from MN va MIHF. LLT regardng MN ndates two possbltes a) RSS for an MN dropped below some spef reshold whle MN n serve at an A b) RSS for one or more As exeeded to a spef reshold whle MN n serve at BS. Usually A s preferred attahment pont an BS sne A s assoated w hgher bandwd ost and hgher data rate. When NSDC obtans LLT t exeutes Network seleton deson algorm and fnd e best A, f no oer best As are found for handoff selet ellular network as e best avalable network. III. NETWORK SELECTION DECISION MAKING ALGORITHMS Most exstng network seleton strateges only foused on e ndvdual user s needs. Motvaton of s paper s to desgn a network-seleton strategy from a system s perspetve, and e network-seleton strategy an also meet a ertan ndvdual user s needs. In e followng, we dsuss how our proposed network-seleton strategy works. A. Algorm 1) Handoff Intaton: MN an be n serve w A or BS. When e RSS streng goes low below some reshold value or when e RSS streng n any of e A goes above some reshold value when e MN s n serve w BS, e MN has to fnd a best network to whh t has to perform handoff.when RSS goes low MN gves Lnk layer trgger to Network Seleton Deson Controller n e network n whh e MN urrently onnets to. Thus e handoff proess s ntated. 2) Handoff Deson: When handoff proess s ntated, e Network Seleton deson ontroller ollets e ondton of eah neghborng network va Meda Independent Handover Funton (MIHF) and exeutes Network Seleton Deson Controller (NSDC) algorm. The algorm frst alulates e sore of e urrent network and ompares e sore w eah of e neghborng network s sore. The sore of e neghborng networks s alulated only f all e parameters have satsfyng value to aept a Moble Host. Our proposed network-seleton strategy prefers a all to be aepted by a network w lower traff load and stronger reeved sgnal streng, whh an aheve better traff balane among dfferent types of networks and good serve qualty. Consequently, we defne a sore funton to ombne ese two fators-e traff load and e reeved sgnal streng. Therefore, e sore to use a network N for a all s defned as e sore funton used s e followng: Sore k j 1 W j Norm j (1) k s e number of parameters. Wj s e weght assgned to e parameter j. Normj s e normalzed value of e parameter j. If any of e network w hgher sore s avalable handoff to at partular network or f any of e network w optmum sore s not avalable handoff to BS. Sore wg. G ws. S wf. F (2)

3 a g e 30 Vol. 10 Issue 5 Ver. 1.0 July 2010 Global Journal of Computer Sene and Tehnology where G s e omplementary of e normalzed utlzaton of network N, R s e relatve reeved sgnal streng from network N, F s e normalzed aess fee of network N and wg (0 wg 1) ws (0 ws 1),wf (0 wf 1), are e weghts at provde preferenes to G, S, F respetvely. The larger e weght of a spef fator, e more mportant at fator s to e user and ve versa The onstrant between wg,ws and wf s gven by wg + ws+wf = 1 (3) Even ough we ould add e dfferent fators n e VHDF to obtan network sore, eah network parameter has a dfferent unt, whh leads to e neessty of normalzaton. The omplementary of normalzed utlzaton G s defned by Bf G B where Bf s e number of avalable bandwd unts n network N, B s e total number of bandwd unts n network N. In general, stronger reeved sgnal streng ndates better sgnal qualty. Therefore, an orgnatng all prefers to be aepted by a network at has hgher reeved sgnal streng. However, t s dffult to ompare e reeved sgnal streng among dfferent types of wreless and moble networks beause ey have dfferent mum transmsson power and reever resholds. As a result, we propose to use relatve reeved sgnal streng to ompare dfferent types of wreless and moble networks. S n (2) s defned by (4) 10 log( R ) (7) The relatve reeved sgnal streng from network N s rewrtten as log( r ) S 1 log( R ) (8) R s e radus of ell of network Aess fee Φ s gven by (1 ) (9) where φ s e hghest aess fee at e moble user lkes to pay, and φ s e aess fee to use network N. The moble user does not onnet to a network at harges more an φ. If an orgnatng all has more an one onneton opton, e sore of all anddate networks are alulated by usng e sore funton n (2). The orgnatng all s aepted by a network at has e largest sore, whh ndates e best network. If ere s more an one best network, e orgnatng all s randomly aepted by any one of ese best networks. Flow hart S (5) where network N, s e urrent reeved sgnal streng from s e reever reshold n network N, and s e mum transmtted sgnal streng n network N. It s to note at we only onsder e pa loss n e rado propagaton model. Consequently, e reeved sgnal streng (n debels) n network N s gven by 10 log( r ) where r s e dstane between e moble user and e BS (or A) of network N, and γ s e fadng fator. Therefore, e reever reshold n network N s gven by (6) Fg 2: Handoff deson Algorm 1 Here s algorm heks only f bandwd s avalable and not hekng t greater an reshold. As e avalable bandwd dereases.e. e load nreases ere s more hane for e RSS to go low. Thus e all droppng probablty nreases and holdng tme dereases. In s algorm f any of e parameters have greater value e sore nreases even f oers have less value.

4 Global Journal of Computer Sene and Tehnology Vol. 10 Issue 5 Ver. 1.0 July 2010 a g e 31 B. Algorm 2 1) Handoff Intaton MN an be n serve w A or BS. When e RSS streng goes low below some reshold value or when e RSS streng n any of e A goes above some reshold value when e MN s n serve w BS, e MN has to fnd a best network to whh t has to perform handoff.when RSS goes low MN gves Lnk layer trgger to Network Seleton deson ontroller n e network n whh e MN urrently onnets to. Thus e handoff proess s ntated. 2) Handoff Exeuton: Handoff exeuton s based on lass trangular problem. Aordng to trangular problem we onsder trangles representng e ondtons of networks. Eah sde of e trangle orresponds to eah parameter. The parameters s problem onsders n s paper are Reeved Sgnal Streng, Bandwd and Aess ost. If all e parameters have desred value (value MN expets) en e resultant trangle wll be equlateral (S1=S2=S3=a, ree sdes equal) and f two of e parameters have desred value e trangle wll be soseles (S1 S2=S3 or S1=S2 S3, two sdes equal). If S1 S2 S3 en e trangle s salene. The networks at gve equlateral trangle and soseles wll be n anddate lst 1 and anddate lst 2 respetvely. Selet one network from lst1 as best network and f lst1 s empty selet best network from lst2. Then perform handoff to e seleted best network. If bo lsts are empty handoff to BS. Flow hart RSS an be measured as 10 log( r ) (10) where s e urrent reeved sgnal streng from network N, r s e dstane between e moble user and e BS (or A) of network. s e mum Fg 3: Handoff deson Algorm 2 transmtted sgnal streng n network N γ s e fadng fator

5 Holdng tme(se) all droppng probablty a g e 32 Vol. 10 Issue 5 Ver. 1.0 July 2010 Global Journal of Computer Sene and Tehnology Bandwd s gven by Avalable Bandwd of e network = Bandwd of e network sum of Bandwd used by all MNs Attahed to e network Aess Fee s e fee at s assgned to eah network usage. It may vary from network to network. User usually prefers e low network fee. IV. ERFORMANCE ANALYSIS Smulatons have been performed for e 3G ell overlay struture. In s senaro ree networks of dfferent data rates o-exst n e same wreless serve area. Network 1 and Network 2 represent b wreless LANs, w bandwds of 2Mbps and 1Mbps, respetvely. Network 3 s modeled as a UMTS network, whh supports multple users smultaneously. The expeted graphs are shown below RSS(dBm) algorm 1 algorm 2 Bandwd Fg 6: Call droppng probablty Vs RSS Holdng Tme V. CONCLUSION algorm Thus s paper desrbes two dfferent handoff deson algorms. 7 Frst algorm uses a sore funton to fnd e Holdng best network at best tme from a set of neghborng Tme networks. Seond algorm uses lass trangle problem to algorm fnd e best network from a set of neghborng networks. If an 9.5 equlateral trangle s obtaned w ree parameters of a network en at network wll be e best among e set of networks. Sne e seond algorm performs handoff only f e onstrants are above e reshold value. The all 18 droppng probablty s redued and holdng tme s nreased Bandwd(Mbps) Fg 4: Holdng tme Vs RSS algorm 2 algorm 1 RSS algorm 2 all droppng probablty algorm 1 all droppng probablty VI. REFERENCES 1) Enrque Stevens-Navarro, Ulses neda-ro, and Jesus Aosta-Elas Vertal Handover n beyond Thrd Generaton (B3G) Wreless Networks Internatonal Journal of Future Generaton Communaton and Networkng, pp , ) K.Ayyappan and.dananjayan RSS measurement for vertal handoff n heterogeneous network, Journal of Theoretal and Appled Informaton Tehnology, pp , ) Kemeng Yang, Iqbal Gondal, Bn Qu and Laurene S. Dooley Combned SINR Based Vertal Handoff Algorm for Next Generaton Heterogeneous Wreless Networks Global Teleommunatons Conferene, GLOBECOM '07, pp , Nov 2007, Dgtal Objet Identfer /GLOCOM

6 Global Journal of Computer Sene and Tehnology Vol. 10 Issue 5 Ver. 1.0 July 2010 a g e 33 4) Wang, R. Katz, and J. Gese, "oly-enabled handoffs aross heterogeneous wreless networks", WMCSA 99, Feb1999, pp , Dgtal Objet Identfer /MCSA ) L-J. Chen, T. Sun, B. Chen, V. Rajendran, and M. Gerla. "A Smart Deson Model for Vertal Handoff." The 4 ANWIRE Internatonal Workshop on Wreless Internet and Reonfgurablty (ANWIRE 2004). May ) Yng-Hong Wang, Chh-eng Hsu, Kuo-Feng Huang, We-Cha Huang Handoff deson sheme w guaranteed QoS n heterogeneous network pp ,2008Dgtal Objet Identfer /UMEDIA ) Ahmed Hasswa, Ndal Nasser, Hossam Hassanen Gener Vertal Handoff Deson Funton for Heterogeneous Wreless Networks Wreless and Optal Communatons Networks, WOCN 2005, pp ,Mar 2005, Dgtal Objet Identfer /WOCN ) Shen,W.;Zeng,Q.-A. A Novel Deson Strategy of Vertal Handoff n Overlay Wreless Networks Ff IEEE Internatonal Symposum on Network Computng and Applatons, 2006,pp Dgtal Objet Identfer /NCA ) Summary: In an overlay wreless network, a moble user an onnet to dfferent rado aess networks f t s equpped w approprate network nterfaes. When e moble user hanges ts onneton between dfferent rado aess networks, a vertal handof...n. Nasser, A. Hasswa, and H. Hassanen, Handoffs n four generaton heterogeneous networks, IEEE Commun. Mag., vol. 44, no. 10, pp , Ot. 2006, Dgtal Objet Identfer /MCOM ) Olga Orrnond, hlp erry and John Murphy Network Seleton Deson n Wreless Heterogeneous Networks 2005 IEEE 16 Internatonal Symposum on ersonal, Indoor and Moble Rado Communatons Volume 4,pp Sept 2005, Dgtal Objet Identfer /IMRC ) We Shen, and Qng-An Zeng, Cost-Funton- Based Network Seleton Strategy n Integrated Wreless and Moble Networks, IEEE Trans. Veh. Tehnol., vol. 57, no. 6, pp , Nov Dgtal Objet Identfer /TVT