Mathematical model based software design for simulation of 4G wireless protocols

Transcription

1 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 Maheaical odel based sofware design for siulaion of 4G wireless proocols E. Kačerginskis, L. Narbuaiė Absrac Ipleenaion of new generaion wireless neworks is a challenging ask ha requires deail nework planning and proocol level siulaion in order o foresee possible probles and save invesen and operaion coss. Exising siulaion plafors are very coplex, expensive and vendor specific. I requires special knowledge for odifying and adoping proocols. This aricle presens Auhors designed aheaical odel and odel based sofware ha allows universal packe level siulaion of differen wireless proocols. Sofware provides graphical user inerface ha allows o describe siulaed proocol, conrol siulaion, analyze ie flow diagras and graphical QoS resuls for differen access and conneciviy nework nodes. In addiion o aricle presens obile WiMAX handover siulaion exaple and provides QoS calculaion resuls ha prove he iporance of nework siulaion prior o ipleening real nework in order o be able o foresee possible bolenecks and plan required overheads. Keywords 4G, handover, LTE, proocol siulaion, WiMAX. I. INTRODUCTION ew generaion broadband wireless echnologies are Nenering elecounicaion arke providing new opporuniies for service providers ha need o ee growing deand for obiliy daa hroughpu. Such echnologies like WiMAX or LTE are able o accep hese challenges, bu require very accurae nework planning and siulaion in order o be able o provide obile services wih expeced QoS and save ipleenaion ie and invesen. Siulaions us be perfored in as deail as possible anner, ensuring ha all proocol level paraeers are evaluaed and ha possible nework growh is esiaed, oherwise lack of planning ay lead o coninuous nework reconsrucion aciviies, loss of cusoers and revenue. Siulaion requires eiher very expensive or inflexible sofware eiher prograable environen which requires special knowledge and professional prograing service. For exaple such sofware as OPNET [] is very expensive for professional 4G siulaion usage and despie i has any feaures, i requires special knowledge in order o be able o adop required proocol. Oher siulaion sofware soluions eiher don provide convenien user inerface eiher don E. Kačerginskis is wih he Deparen of Telecounicaions, Kaunas Universiy of Technology, Sudenų sr , Kaunas, LT-5368 Lihuania (e-ail: eugenijus@nservice.eu L. Narbuaiė is wih he Deparen of Telecounicaions, Kaunas Universiy of Technology, Sudenų sr , Kaunas, LT-5368 Lihuania (e-ail: lina.narbuaie@ku.l allow o perfor deep proocol level siulaion [] [3]. Firs par of he paper covers aheaical odel, is srucure and working algorihs. Cuous fro foralized aheaical specificaion are provided. In addiion o, aricle describes sofware graphical inerface and funcionaliy, which allow service providers sealessly siulaing QoS characerisics for differen proocols in wireless channel and oher nework nodes and analyzing ie flow diagras for each daa exchange beween nework eleens. I allows evaluaing such characerisics as laency, generaed uplink and downlink daa hroughpus, essage exchange and processing ies, delays in nework nodes. Finally paper provides WiMAX handover proocol descripion exaple, QoS siulaion resuls and analysis. II. IMITATIVE MATHEMATICAL MODEL A. Model concep Siulaion sofware is ipleened on iiaive aheaical odel basis. Iiaive aheaical odeling allows siulaing real ie behavior of any environen consising fro separae eleens. In aheaical odels hese eleens are called aggregaes [4]. Fro elecounicaions poin of view hese aggregaes are nework nodes and counicaion channels. Each aggregae in aheaical odel perfors specified asks based on inforaion of inpu and oupu signals. Aggregae principal specificaion is provided in Fig.. xk Inpu signal Message (packe nuber yk Oupu signal Agregae - Processing ie of incoing essage evaluaion; - Message foraion ie calculaion; - Message forwarding o nex required eleen afer specified ie; - Saisics calculaion. Arrays of paraaers By essage nuber: - Packe loss (error probabiliy; - Repeaed essage no. if error; - Message (packe size in bis; - Message foraion and processing ies; - Oher paraeers; Fig. aggregae specificaion Oupu signal Inpu signal yk Message nuber Model requires specifying inernal and exernal signal flows and signal exchange beween syse aggregaes. Such srucure and aheaical foralizaion allows specifying xk 35

2 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 each syse node independenly and requires coon exernal signals o rigger each over. Aggregae approach based siulaion racks siulaion ie independenly fro syse clock and allows calculaing ie based paraeers such as daa hroughpu in bis per second. B. Aggregaive specificaion For 4h generaion wireless nework siulaion we use 5 aggregaes ha represen ajor nework eleens: Gen. represen user generaor, ha iniiaes siulaed procedure; MS obile saion; Channel wireless channel wih loss probabiliies; BS base saion, represening uliple base saions, paricipaing in essage exchange; ASN/CSN conneciviy nework, represening Operaor s core nework eleens. y x y x y x y x Gen. MS Channel BS CSN x y x y x y x y Fig. odel srucure Modeling ie sars afer iniial rigger, usually fro addiional aggregae called generaor. In wireless siulaion, his eleen serves as user generaor, siulaing sar of he packe exchange procedure. Tie flow exaple of essage exchange beween wireless nework eleens is provided in Fig. 3. Aggregae Generaor sends signal o MS and sars procedure siulaion. MS acceps essage and keeps essage arrival ie. MS fors and ransis essage o wireless channel wih packe loss probabiliy. Channel eiher ransis essage o BS aggregae (probabiliy -P eiher iiaes packe loss in wireless channel (P and adds addiional delay. In case of error, essage is ransferred back o obile saion for repeaing. Nuber 0 is ransferred as signal exchange paraeer insead of nex essage nuber. Generaor Tie signal While all N packes ransfered Packe exchange ie Transferred daa bis Mobile saion N 0, if P N or -, if P or N-X, if P4 N+ N+ N if P; N-X if P4 0, if P N+ or -, if P or N-X, if P4 Wireless channel N N+ N-x if P4 N+ Base saion N.K N.K + or N.K if P3 N.K N.K + or N.K if P3 or N-x, if P4 N.K N.K + N.K or N.K if P3 N+ N.K + N+ N-X if P4 or N-x, if P4 Fig. 3 essage exchange cycle ie flow diagra Conneciviy nework While all K packes ransferred While all K packes ransferred If here are no errors in wireless channel essage is ransferred o base saion aggregae. Respecively BS sars essage exchange cycle wih CSN ha is required by essages paraeers fro MS. CSN afer each essage provides answer essage ha includes nuber of nex essage which us be sen fro BS o CSN. There is probabiliy ha eiher essage is los in CSN eiher received negaive answer (P3. In such case essage is repeaed fro essage nuber ha is received in CSN answer essage. Afer successful cycle of essage exchange beween base saion and conneciviy nework, CSN wih las essage sends essage nuber ha us be sen nex fro MS. Wih probabiliy (-P4 higher nuber is ransferred o BS. I eans ha MS received posiive answer fro conneciviy nework and ay send nex essage of siulaed proocol. In case here is negaive answer (P4 fro CSN, i sends lower essage nuber o BS. I eans ha MS us repea previous essage exchange. BS saves corresponding essage nuber and afer receiving nex packe fro MS, will copare saved and new essage nuber paraeers. BS sends nex essage reques o wireless channel. In case of packe loss in channel (P i sends negaive essage nuber. Afer receiving nex essage nuber MS sars second ieraion of essage exchange cycle. In case negaive or zero essage nuber is received, MS repeas corresponding essage. When all essage exchange cycles are copleed successfully, MS sends signal o generaor for calculaing saisics such as cuulaive essage exchange cycle ie and ransferred daa bis. C. Foral aheaical specificaion Foral aheaical specificaion is widely used for siulaion of real ie syses. Siilar o algorih, aheaical specificaion allows anually racking siulaion logic. Despie i is less visual, his ype of specificaion provides abiliy o rack syse ie and calculae syse paraeers for each ie oen. I also is easily adopable o prograable environen. Specificaion requires aheaically foralize each aggregae describing inpu/oupu signal ses, inernal and exernal even ses, discree and coninues sae ses and ransiion operaors ses [4]. This paper provides coens and siplified exaples of foral aheaical specificaion for wo aggregaes obile saion and wireless channel. Two specificaions allow invesigaing signal exchange beween aggregaors in aheaical odel. Mobile saion. Inpu signal se. Inpu signal ses describe signals ha are received fro oher aggregaors and iniialize swiching operaors o perfor calculaions. X = { x, x} ( x sar signal is received fro generaor; x nuber of nex packe, ha us be sen fro MS.. Oupu signal se. Oupu signals ses describe signals ha are sen o oher generaors in order o ransfer inforaion or iniiae procedures. 36

3 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 Y = { y, y } y y = ( packe _ no = ( service _ ie, received _ daa packe_no packe nuber ha is sen beween MS and BS; service_ie packe aggregaion ie; received_daa received daa bis. 3. Exernal even se. Exernal evens se describes evens, ha are iniiaed by inpu signals. E ' = { e ', e '} (3 e received essage fro generaor; e received essage fro wireless channel. 4. Inernal even se. Inernal evens describe evens, ha are resul of aggregaor s inernal operaions and depends fro anageen flows. E " = { e"} (4 e - essage is fored and ready o be sen. 5. Transiion raes. Transiion raes beween he syse saes specify paraeers ha conrol inernal evens. e" { ξ j} (5 where ξ j essage sending fro MS o BS foraion ie; 6. Discree sae coponens. Discree sae coponens describe differen paraeers ha are calculaed for each ie oen. ν ( = { packe _ no. packe _ lengh(, ax(, (6 arrival _ ie(, las _ sen( } packe_no.pake_lengh( processed essage (packe_no lengh in bis; ax ( axial nuber of essages for curren procedure; arraival_ie ( oen, when MS iniaes essage sending; las_sen ( las sen essage nuber. 7. Coninuous sae coponens. Coninuous sae coponens describe ie oens of inernal evens. Zν ( = { ω( e", } (7 ω(e, oen when essage is ready o be sen o channel; 8. Iniiae sae. Iniiae sae describes iniiae sae paraeers no required for obile saion aggregae. ( 9. Saring sae. Saring sae paraeers described a ie 6 and 7. In his case, MS aggregae has no paraeers a zero ie oen. z ( 0 = {0,0,0,0; 0} (8 0. Transiion operaors. Transiion operaors perfor calculaions, define nex ie oens for oher operaors and define oupu signals for oher aggregaors. Transiion operaors are acive only if heir even ie is acive. H(e received signal o sar operaion: ax( + = MAX{ packe _ no} (9 ", + = packe _ no (0 arrival _ ie( + = ( H(e essages are ready o be sen o channel: ω ( ", + = ( las _ sen( + = packe _ no( (3 G(e : (essages are ready o be sen o channel y = packe _ ( (4 H(e received essage fro channel: If here are unsen essages (nex_packe ax ω ( ', + } = (5 packe _ no( + = nex _ packe (6 received _ daa( + = received _ daa( + (7 + packe _ no. packe. lengh( ", + = packe _ no (8 Else (all essages are sen successfully process _ ie( + = arrival _ ie( (9 packe _ no( + = (0 y = process _ ie, received _ daa ( Resul ha is given by ransiion operaors equaions: (9 oal nuber of essages ha us be sen; (0 ie, when essage foring is finished, in his case i defines ie oen for swiching operaor H(e ; ( saves essages arrival ie; ( ie oen, when essage will be sen o channel in oher ieraion, is no defined; (3 saves nuber of las sen packe; (4 signal wih paraeers are sen o channel; (5 ie oen when nex essage will be received fro channel is no defined; (6 nex essage nuber (his aricle presen only siplified exaple, when here are no errors in wireless channels, oherwise i should be specified o repea sae essage nuber as described in aggregaive specificaion (7 received daa calculaion for siulaion resuls; (8 ie oen when nex essage will be sen o channel 37

4 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 (9 processing ie calculaion for siulaion resuls; (0 reses packe nuber for nex ieraion (all curren ieraion packes are already sen ( reurns signal o generaor abou finished essage exchange Wireless channel. Inpu signal se: X = { x, x} x = ( packe _ no ( x = ( nex _ packe packe_nr nuber of packe ha is received fro MS; nex_packe nuber of nex packe, ha us be sen fro MS o BS, nuber is received fro BS;. Oupu signal se: Y = { y, y} y = ( packe _ no (3 y = ( service _ ie, received _ daa packe_no packe nuber ha is sen o BS; nex_packe nuber of nex packe, ha us be sen fro MS o BS, nuber is received fro BS. 3. Exernal even se: E ' = { e ', e '} (4 e received essage fro MS; e received essage fro BS. 4. Inernal even se: E " = { e", e", e3", e4"} (5 e - essage is ready (fored o be sen o BS; e - essage is ready (foraed o MS; e 3 - error siulaion is ended for essage ha was sen fro MS; e 4 - error siulaion is ended for essage ha was sen fro MS. 5. Transiion raes. e" { ξ 3 j} e" { ξ 4 j} e3" { ξ 5 j} e4" { ξ 6 j} ξ 3j essage o BS foraion ie; ξ 3j essage o MS foraion ie; ξ 3j error siulaion ie (MS side error; (6 ξ 3j error siulaion ie (BS side error. 6. Discree sae coponens. Wireless channel doesn include discree sae coponens, because wireless channel aggregae conrols iing and doesn perfor calculaions. ν ( = {} (7 7. Coninuous sae coponens. Zν ( = { ω( e",, ω( e",, ω( e3",, ω( e4", } (8 ω(e, ie when essage is ready o be sen o BS; ω(e, ie when essage is ready o be sen o MS; ω(e, end oen of error siulaion fro MS side; ω(e, end oen of error siulaion fro BS side; 8. Iniiae sae paraeers. P error fro MS side probabiliy; P error fro BS side probabiliy. 9. Saring sae. z ( 0 = {0,0,0,0} (9 0. Transiion operaors. H(e received essage fro MS: If no error fro MS (no P ", = ( packe _ no Else (P 3 ", = (3 + 5 packe _ no H(e received essage fro BS: If no error fro MS (no P ", + = 4 nex _ packe Else (P 4 ", + = 6 nex _ packe H(e essage are ready o be sen BS: ", + = (3 G(e signal o BS aggregaor: y = packe _ no ( (34 H(e essage is ready o be sen o MS ", + = (35 G(e signal o MS aggregaor: y = nex _ packe ( H(e 3 error siulaion fro MS side is finished: ", = ( packe _ no H(e 4 error siulaion fro BS side is finished: ", = ( nex _ packe 38

5 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 Siilar specificaion is required for every aggregae in he aheaical odel. For coplex syses aheaical foralizaion can be quie difficul process ha requires special knowledge, bu such foralizaion provides flexibiliy and eases siulaion auoaion process when ipleened in prograable environen. III. SIMULATION SOFTWARE Using described aheaical odel, auhors designed sofware for 4h generaion wireless nework siulaion for Windows plafor. Delphi 7 plafor was used as prograing environen. Iniially sofware was inended o siulae regisraion and handover procedures of obile WiMAX. Flexible aheaical odel and designed graphical inerface allowed uilizing sofware for siulaion of alos any wireless proocol (WiFi, UMTS, LTE, ec based on hand-shaking algorihs. Sofware does no require any special aheaical knowledge. All inpu paraeers of siulaed proocol can be enered using graphical inerface. Because of ipleened aheaical odel, he accuracy of he sofware depends only on he reliabiliy of enered paraeers. A. Designed sofware GUI descripion Graphical user inerface (GUI of designed sofware is provided in Fig selec how any ies siulae proocol before final resul; - selec axial nuber of even allowed in siulaion; - onior siulaion cycles (odeling virual ie, nuber of siulaed cycles, nuber of oal evens; - Load or save configuraions; - Conrol viewing opions of he resuls (enable labels, swich beween D and 3D; - Selec siulaion progress visualizaion ype ie flow diagra for sep by sep siulaion and analysis; progress bar for rapid siulaion; - Quick swich beween displayed resuls. Fig. 5 siulaion conrol secion C. Paraeer inpu secion This secion allows sofware users o describe proocol paraeers if here is no available predefined profile or if i requires addiional cusoizaion. Paraeer inpu secion is designed as wo configurable arixes. User can ener he nuber of essages/packes ha are used in for soe proocol or par of i. Sofware fors able for each packe where users can ener paraeers, such as packe lengh, laency of nework nodes, error probabiliies in wireless channel, packe processing or foraion ie, ec. For each MS-BS essage syse allows o selec a nuber of BS- CSN essages, and o describe paraeers for each. This flexible and liiaion free approach allows users easy cusoizing heir invesigaion o achieve os deail resuls. Fig. 4 sofware graphical inerface Fro funcionaliy poin of view inerface can be divided ino 4 ajor secions: siulaion conrol secion; paraeer inpu secion; siulaion ie flow secion; secion of graphical resuls. B. Siulaion conrol secion Siulaion conrol secion (Fig. 5 is designed for easy siulaion anageen. I provides saus window, where users can see siulaion sae and where can find addiional explanaions or required correcions for enered paraeers. Window can be cleared any ie in order o have acual inforaion. This secion allows: - sar, resar or run siulaion sep by sep; Fig. 6 paraeer inpu secion D. Siulaion ie flow secion Siulaion ie flow diagra secion provides graphical view of siulaed proocol in ie doain. This is one of he 39

6 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 os iporan designed sofware s funcion, because allows users o onior siulaion in real ie and analyze each essage or packe. I allows verifying siulaion accuracy. neighbor secors offer higher signal level han serving base saion. This is ipleened in order o achieve sealess conneciviy for obile nework users as illusraed in Fig. 9. Fig. 9 handover beween base saions [8] Fig. 7 siulaion ie flow diagra In addiion o, syse allows disabling ie flow diagras for bes perforance when rapid calculaions are necessary. In such case users can onior siulaion progress in progress bar view. E. Secion of graphical resuls This secion provides graphical resuls of siulaion. There are any saisical resuls ha can be analyzed in and 3 diensional views. Despie ain purpose of he handover was o serve obile users, handover also effecs all users ha are in overlapping areas of wo adjacen base saion secors, where signal srengh of few base saions has siilar levels. Fig. 0 illusraes siplified exaple of overlapping coverage of wo base saions. Secor coverage Coninues handover zone Fig. 0 overlapping coverage of wo base saions Fig. 8 view of graphical resuls Sofware provides following saisics: coplee essage exchange ie for each siulaed cycle; average essage exchange ie; average uplink and downlink hroughpu (real ie; average processing ie in BS/MS; average delay in BS/CSN connecion; average uplink and downlink hroughpu (full cycle. IV. WIMAX HANDOVER QOS SIMULATION This paper secion provides obile WiMAX handover procedure descripion and siulaion exaple. The objecive of siulaion is o evaluae wha raffic is generaed by obile saions when perforing handover procedure and wha laency can be expeced. A. Handover procedure descripion Handover procedures are perfored when obile saion is in coverage of ore han one base saion secor and when This obiliy anageen logic leads o coninues handover procedures generaed y obile saions ha are in he area of secor edges. Overlapping secors are coon in wireless nework ipleenaion and coninues handovers can be observed in earlier generaion neworks, such as GSM and UMTS. In opposiion o GSM/UMTS, where signaling channels are used for obiliy anageen, 4 h generaion echnologies share sae channels for daa and for signaling inforaion. This can lead o decreased nework capaciy in uliple user environens. Mobile WiMAX handover procedure consiss of a nuber of essages ha us be ransferred beween MS, BS and core nework. These essages are ransferred in air inerface as defined in air inerface specificaion [5]: RNG-REQ (368 bis range reques; RNG-RSP range response (04bis; MOB_MSHO-REQ (47 bis ( neighbor BS, 584 bis ( BS; 688 bis (3 BS MS handover reques; MOB_BSHO-RSP (464 bis ( BS, 5 bis ( BS, 568 (3 BS BS handover response; MOB_HO-IND (39 bis handover indicaion; 40

7 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 Fas_Ranging_IE (7 bis exchange of radio paraaers. MS BS ASN / CSN BS BS 3 Tie MOB_MSHO_REQ MOB_BSHO_RSP MOB_HO_IND Fas_IE_Rangin RNG_REQ RNG_RSP Regisraion procedure sar Announce possible handover Receive he answer Announce possible handover Receive he answer BS selecion Announce handover sar Synchronize wih base saion MS info reques MS info response Announceen ha MS is regisered MS service erinaion and ransfer Regisraion procedure end Resued daa session Fig. handover ie flow diagra [5] B. Handover QoS siulaion WiMAX sandard described paraeers were used for siulaion. I was assued following iing paraeers: essage processing ie in nework nodes is s; wireless channel laency 5 s; channel laency in packe loss case 50 s; packe loss probabiliies 0,,5,0 perc. respecively for each siulaion. Throughpu, bps Packe loss: 0% % 5% 0% BS 3 BS 4 BS Nuber of base saions Fig. Handover downlink hroughpu Each siulaion cycle (wih differen error probabiliies was perfored 000 ies. Accuulaed siulaion resuls are provided in Fig. -3. Handover procedure of one user can creae fro 3 o 9.5 kbps daa hroughpu for downlink and fro.5 o 7 kbps for uplink. [6] This is no significan load fro perspecive of one user, bu i can cause secor capaciy decrease in uliple user environens. For evaluaion of handover ipac in uliple user neworks i s required o perfor basic nework planning. Firs sep is o esiae coverage (radius of one base saion and o calculae secor capaciy. These asks were auoaed using Auhors designed sofware package ha includes sandard radio propagaion aheaical odels and ools for calculaing WiMAX daa hroughpu dependencies fro odulaion schees. Following paraeers were used for calculaion: Table I. Base saion air inerface paraeers Paraeer Value Model SUI-A (Urban environen Tx power 3 db BS anenna gain 8 dbi MS anenna gain 9 dbi Frequency 3500 MHz Channel size 0 MHz Downlink/uplink raio 80/0% Fig. 4 illusraes signal srengh dependence fro disance fro base saion. In addiion o i shows odulaion raes ha can be used and cerain disances Packe loss: 0% % 5% 0% Throughpu, bps BS 3 BS 4 BS Nuber of base saions Fig. 3 Handover uplink hroughpu Fig. 4 signal level and odulaions The higher is he disance fro base saion he lower rae odulaion can be uilized for counicaions aenuaion in wireless pah decreases signal o noise raio. Assuing Sanford Universiy Ineri (SUI radio propagaion aheaical odel, in urban nework environen highes rae odulaion can be used only in radius of 600 o 800 4

8 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 eers. Lowes rae odulaion (QPSK/ operaional disance is abou 800 eers. Daa hroughpu dependencies fro odulaion and odulaion dependencies fro signal level are provided in Fig perc. of obile saions perfors handover a secor edges; 5 o 75 obile saions in secor; 5 perc. overlap of adjacen secors. Fig. 5 signal level and odulaions Second sep for handover ipac evaluaion in uliple user environens is esiaion of area beween overlapping secors. These asks can be perfored using Auhors designed coverage calculaor (ou of scope of his aricle. I perfors auoaic geoery analysis, calculaes nuber of users ha share overlapping areas and allows auoaic uliplicaion for esiaing oal generaed daa loads. Fig. 6 illusraes base saion disribuion when opial nework coverage is ipleened (no gaps in coverage, sandard frequency planning. There are four wireless secor ypes in such base saion disribuion: no overlapping areas; overlapping wih one base saion; 3 overlapping wih wo base saions; 4 overlapping wih hree base saions. Fig. 7 Handover hroughpu for uliple MS (downlink In uliple user environen handover in ype 4 secor can creae daa load fro 50 o 30 kbps for downlink and fro 40 o 0 kbps for uplink. Fig. 8 Handover hroughpu for uliple MS (uplink Fig. 6 base saion disribuion These daa loads are no significan alking abou overal nework capaciy of 4 generaion neworks, bu when lowes rae odulaion QPSK/ is used, wha is os probably a secor edges, handover can decrease secor capaciy by 0% for downlink and 40% for uplink. Calculaion illusraes handover procedure ipac when opial nework coverage is ipleened. In real world environen opial nework planning is hardly achievable. Nework providers can face siuaions where whole areas of few base saions overlap. This siuaion is possible in areas where addiional base saions are ipleened for higher nework capaciy. Such pracice is widely used in any wireless neworks, i.e. GSM/UMTS. -3 secor ypes can be found a nework edges. Secor ype 4 is os probable in ajor area of nework coverage. Fig. 7-8 provides handover generaed daa hroughpu resuls for differen ypes of secors (differen nuber of overlapping secors and differen nuber of users, assuing: perc. packe loss probabiliy; 4

9 INTERNATIONAL JOURNAL OF COMPUTERS AND COMMUNICATIONS Issue, Volue 7, 03 REFERENCES Fig. 9 base saion disribuion in high densiy neworks In such case, i s necessary o plan addiional overhead when ipleening obile WiMAX nework in order o copensae handover overhead ipac and avoid inconsisences a secor edges. Handover ie (laency siulaion resuls are provided in Fig. 0. Handover ie differs fro 9 o 89 s [6]. Such laency can cause insabiliy or inerrupion in real ie service such as VoIP. [7] Accurae obiliy anageen soluion selecion or addiional signaling ipleenaion can be uilized in order o ipleen successful services [9]-[0]. [] OPNET Technologies, Inc [online]. Available: hp:// [] B. Shah, Y. V. Rao, S. Eldhose, R. Vardarajan., WiSi A Sofware diulaion esbed for obile WiMAX, Proceedings of he 7h WSEAS Inernaional Conference on Siulaion, Modelling and Opiizaion, Beijing, China, Sepeber 5-7, 007. [3] Baber Asla, a all., IEEE 80. wireless nework siulaor using Verilog, h WSEAS Inernaional Conference on counicaions, Agios Nikolaos, Cree Island, Greece, July 6-8, 007 [4] H.Pranevičius, Foral specificaion and analysis of copuer nework proocols: aggregae ehod, "Technologija", 004. [5] IEEE, IEEE Sandard for local and eropolian area neworks / Par 6: Air inerface for broadband wireless access Syses, New York, 009. [6] E.Kacerginskis, L.Narbuaie, Capaciy and handover analysis in obile WiMAX, Elecronics and Elecrical Engineering, Vol. 3(9, 0, pp [7] Nokia Sieens Neworks, Laency The ipac of laency on applicaion perforance, Finland, 009. [8] G. Soian, Iproveen of Handoff in MobileWiMAX Neworks Using Mobile Agens, Laes rends on copuers (volue I, 00, pp [9] F. Andreoi, N. Ciulli, M. Curado, G. Landi, C. Nardini, Signalling exensions for QoS suppor in a IEEE 80.6d/e doain, 7h WSEAS In. Conf. on Elecronics, Hardware, Wireless and Opical Counicaions, Cabridge, UK, February 0-, 008, pp [0] Z. Bojkovic, D. Milovanovic, Coexisence goals of VoIP and TCP raffic in obile WiMAX neworks: perforance of fla archiecure, Proceedings of he 9h WSEAS Inernaional Conference on applied inforaics and counicaions,009, pp Regisraion ie, s Packe loss: 0% % 5% 0% 80 BS 3 BS 4 BS Nuber of base saions Fig. 9 Handover hroughpu for uliple MS CONCLUSION Ipleenaion of new generaion wireless neworks is a coplex ask, which requires evaluaion of any facors in order o be able o provide planned services. Nework siulaion allows ipleenaion ea o foresee possible issues and accordingly plan soluions. Maheaical iiaive odel based siulaion allows o perfor hese asks in os deail proocol level anner. Auhors designed sofware ipleens aheaical odel and provides graphical user inerface for easy and flexible operaion ha requires no special knowledge. Mobile WiMAX siulaion shows ha even such regular procedure as handover can cause significan ipac on secor capaciy and real ie service. Advanced siulaion allows nework providers o foresee possible bolenecks and plan required overhead in order o avoid possible QoS disadvanages. 43