New Technique giving Priority to Emergency Calls in Wireless Cellular Security Networks

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Candice Wiggins
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1 roceedigs of te 5t WSEAS It. of. o ALIED INFOMATIS ad OMMUNIATIONS, Malta, September 5-7, 25 (pp6-65 New Tecique givig riority to Emergecy alls i Wireless ellular Security Networs K. IOANNOU, E. DIMITIADOU, A. IOANNOU 2, I. ANOUTSOOULOS, A. GAMIS 3 ad S. KOTSOOULOS Wireless Telecommuicatio Laboratory, Departmet of Electrical ad omputer Egieerig, Uiversity of atras, io 265, atras GEE 2 OTE S.A, Messologi, 32 GEE 3 Departmet of Applied Ifortics i Maagemet & Ecoomy, Tecological Educatioal Istitutio of Messologi, Messologi, 32 GEE Abstract: - I tis paper is preseted a ew tecique tat gives priority to Emergecy alls i Wireless ellular Security Networs. Te ew tecique uses a cael agemet sceme ad it is based o a twolayer cellular arcitecture Te lower layer of te proposed arcitecture is based o a crocellular solutio, for absorbig te traffic loads of bot te adoff ad ew calls of Emergecy alls (. Te iger layer is based o a cro-cell umbrella solutio, for absorbig te traffic load of te adoff ad ew calls of te No Emergecy alls (. Te results sow tat usig te optimum umber of caels i eac layer, te QoS of i a cogested area were a extreme evet was appeed is optized, avig te imum egative effect o te QoS of te. Key-Words: - Wireless commuicatio, Security Networs, ael Assigmet Sceme Itroductio ublic Safety ad Security orgaisatios require te igest levels of reliability ad availability i teir commuicatios. Wireless ellular Security Networs etwors provide commuicatios i extreme situatios tat y cause oter commuicatios etwors to fail. For example, tuderstorms or eartquaes ofte cause wide area or eve atiowide blacouts i electricity productio ad distributio ad restorig power y tae days or eve wees. I suc coditios, public services are typically bloced by eavy traffic or are totally out of operatio. Wireless ellular Security Networs systems are desiged to esure operatios i tese situatios. All critical etwor elemets are duplicated to esure cotiuous operatio. User ad call priorities are desiged to give priority to critical commuicatio. eliability is a ey criterio i te desig of Wireless ellular Security Networs radios. Tese ca be used i ars evirometal coditios ad are muc more rugged ta cellular adsets. Te most serious problem tat arises i tese systems uder extreme situatios is tat services are bloced. Tis appes because i te area te evet appes y users are cocetratig tere. A great effort as bee spet i order to study te cael agemet scemes i order to ize te ivolved blocig probability [2]. Te adoff blocig probability is cosidered to be more importat ta te blocig probability of ew calls because te call is already active ad te QoS is more sesitive for te adoff calls. Te proposed tecique will be compared wit two models. Te first adopts a traffic aalysis for wireless cellular security etwor wit o-

2 roceedigs of te 5t WSEAS It. of. o ALIED INFOMATIS ad OMMUNIATIONS, Malta, September 5-7, 25 (pp6-65 prioritized adoff procedure. All caels are available to all calls (Erlag- model Te secod adopts a traffic aalysis for cellular mobile etwors wit prioritized adoff procedure. y taig ito accout tat are te available caels i every crocell ad te priority tecique for adoff calls is realized by assigig guard caels ( exclusively for adoff calls, te reiig (- caels are sared bot by ew ad adoff calls. Te followig assumptios, witout affectig te results, are cosidered: a te terals are caracterized as or accordig to te emergecy. b omogeous traffic, same capacity ad same mea oldig time T are cosidered i all crocells. New ad adoff calls of are geerated i te area of crocell accordig to a oisso poit process, wit mea rates of, respectively, wile ew calls ad adoff calls of are geerated wit mea rates of, per cell. Te relative mobilities are defied as: for : a ( for : a (2 also it is defied a coefficiet for : (3 ad for (4 Te offered load per cell is Toff (5 were /T ad T is te cael oldig time. 2 New roposed Tecique Let be te umber of crocells i te crocellular area. Te total offered load i te system is: tot Toff Toff (6 ad te total umber of caels i te system is s (7 Te steady state probabilities tat caels are busy i every crocell, ca be derived from [3] (! ( ( ( for,2,...,! (8 for,..., were: (9!! ( Te blocig probability ( for a ew call (eiter or per crocell is te sum of probabilities tat te state umber ( of te crocell is (-. ece: ( Te probability of adoff attempt failure is te probability tat te state umber of te crocell is equal to. Tus: ( Te of is: (2 Te mea call blocig probability ( l for te crocellular layer ( crocells, cosiderig ew ad adoff calls of ad, is defied as: l L m L ( ( i ( i ( i ( i ( i ( i L L ( i ( i ( i ( i (3 Te ew proposed tecique uses a cael agemet sceme. It is based o a two-layer arcitecture ad it is itroduced i order to dedicate differet layers to differet types of subscribers, accordig to te emergecy of call (Emergecy alls ad No Emergecy alls. Te implemetatio of te differet layers does t require ay special ardware settig but oly ew radio parameters i te existig software. Tis approxitio itroduces a two-layer arcitecture, te lower crocellular layer ad te iger, te Umbrella layer, wic is implemeted by a crocell [4],[5]. Figure sows te proposed

3 roceedigs of te 5t WSEAS It. of. o ALIED INFOMATIS ad OMMUNIATIONS, Malta, September 5-7, 25 (pp6-65 arcitecture. I additio, te crocell cell layer services adoff calls of ad ew calls of, te umbrella layer services ew ad adoff calls of, omogeeous traffic is cosidered i all crocells ad umbrella cell, ad te T is te same for te crocells ad te umbrella cell. Let be te umber of crocells tat cosist te crocellular layer ad te umber of caels tat assiged to every crocell. Let S be te total umber of caels i te system ad te caels assiged to crocell to serve bot adoff calls of ad ew calls of. ece: te sllest egative effect o te QoS of. Eac time a cael must be allocated i te crocell, te existig coditios of offered load i te system are ceced. Te suitable umber of caels tat ca be assiged i te cro-cell is detered depedig o te preseted traffic. Te algoritm cotiues te process for differet values of / S. Te results are compared wit tose of a simple model i wic te iger level of umbrellacell does ot exist. Te steady state probabilities tat caels are busy i a crocell ca be derived from figure 2 [2],[3] (! m m ( m m! (5,2,...,,..., Figure : roposed two-layer arcitecture S (4 Te adoff blocig probability is cosidered to be more importat ta te blocig probability of ew calls because te call is already active ad te QoS is more sesitive for te adoff calls. So i te crocellular layer, priority is give to adoff attempts by assigig guard caels ( exclusively for adoff calls of amog te caels i a cell. Te reiig ( - caels are sared by bot ew calls of ad adoff calls of [3]. Silarly, i te iger layer (crocell, priority is give to adoff attempts of by assigig guard caels exclusively for adoff calls of amog te caels i umbrella. Te reiig ( - caels are sared by bot ew calls of ad adoff calls of. Te mea rate of geeratio of adoff calls of is per cell ad te mea rate of geeratio of ew calls of is. So te mea rate geerated i te umbrella is. I te ew proposed tecique, a ratio / S is tot assiged accordig to α, α,, ad T off, cotributig to te improvemet of QoS of wit were m! ( (! (6 Te blocig probability for a ew call of per crocell is te sum of probabilities tat te state umber of te crocell is -. ece: (7 Te probability of adoff attempt failure is te probability tat te state umber of te crocell is equal to. Tus: (8 For te umbrella cell, te steady state probabilities tat caels are busy ca be derived from figure 2 [2],[3]: (! (!,2,...,,..., (9

4 roceedigs of te 5t WSEAS It. of. o ALIED INFOMATIS ad OMMUNIATIONS, Malta, September 5-7, 25 (pp ( ( 2 2 ( ( 2 Figure 2: State Trasitio diagram for: (a every crocell ad (b umbrella cell of proposed arcitecture were! ( (2! Te blocig probability for a ew call of per cell is te sum of probabilities tat te state umber of te umbrella cell is -.ece: u (2 Te probability tat a adoff call will be bloced i te umbrella cell is ad is te probability tat state umber of te cell is equal to. Tus: Te probability tat a adoff call will be bloced i te umbrella cell is ad is te probability tat state umber of te cell is equal to. Tus: (22 Te QoS te crocellular layer ( crocells, is defied as: QoS L L ( ( i ( i ( i ( i L L ( i ( i (23 For te umbrella layer te QoS of is defied as: QoS ( ( i ( i ( i ( i ( i ( i (24 Terefore, te QoS for adoff calls especially for must be guarateed wile allowig ig utilizatio of caels. Te obective of te proposed arcitecture is to guaratee te required adoff blocig probability for. 3 esults Te above tecique was simulated. I te performed simulatio, te umber of crocells is cosidered to be 3, witout affectig te geerality of te model. Te followig parameters are also cosidered:.2,. T 75s, α ΝΕ.2, α.4,.8 ad.2 ad S 2 ad 4. Figure 3 ad 4 preset te perforce of call

5 roceedigs of te 5t WSEAS It. of. o ALIED INFOMATIS ad OMMUNIATIONS, Malta, September 5-7, 25 (pp6-65 blocig probability for ew ad adoff calls of respectively. Figure 5 presets te QoS of. I all figures, curve (i represets te perforce of a typical cellular security wireless etwor accordig to a traffic model aalysis based o erlag b model (OLA-E. urve (ii represets te perforce of a typical cellular security wireless etwor accordig to a traffic model aalysis wit prioritized adoff procedure (OLA- G. I tese cases, tere is o umbrella layer ad all te ivolved calls are served by crocells. urve (iii sows te perforce of a cellular security wireless etwor wic uses te roposed Tecique tat gives riority to Emergecy alls (Tg ad it is based o te two layer arcitecture, were ew ad adoff calls of are served by te umbrella layer ad te ew ad adoff calls of by te crocellular layer. I curve (iii: / S 48/2, / S 24/2. urves sow a great improvemet i te QoS of ad i all locig robability of adoff alls of as a result of usig te proposed tecique wit te a egative effect i all locig robability of New alls of. 4 oclusio A ew proposed tecique tat gives priority to Emergecy alls i Wireless ellular Security Networs i order to acieve better QoS for i areas tat a extreme evet was appeed. I tis arcitecture, te umbrella cell pilosopy as bee itroduced to serve ew ad adoff calls of. Moreover, accordig to te obtaied results, te all locig robability of adoff alls of as bee optized avig egative effect o te all locig robability of New alls of. locig robability Traffic (Erlags Figure 3: all locig robability of New alls of locig robability locig robability Traffic (Erlag Figure 4: all locig robability of adoff alls of Traffic (Erlag Figure 5: QoS of efereces: [] K. Ioaou, S. Louvros, I. aoutsopoulos, S. Kotsopoulos ad G. K. Karagiaidis, Member IEEE, Optizig te adover all locig robability i ellular Networs wit ig Speed Movig Terals, IEEE ommuicatios Letters, Vol 6, No., October 22. [2] T. S. appaport, Wireless ommuicatios, July 999, ISN [3] D.og ad S.S. appaport: Traffic model ad perforce aalysis for cellular mobile radio telepoe systems wit prioritized ad o prioritized adoff procedures, IEEE Tras., 986, VT-35, pp [4] D.erreti, Default set of SS arameters for osmote Networ ad set of SS parameters for umbrella cells, Noia roductivity Services, Tec. ep, Noia Telecommuicatios, , pp 2-6. [5] J. Zader, S-L Kim, adio esource Maagemet for Wireless Networs, 2, ISN

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