ToA node distance estimation enhancement in MANET localization algorithm based on cooperative trilateration

INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 211 TOA NODE DISTANCE ESTIMATION ENHANCEMENT IN MANET LOCALIZATION ALGORITHM BASED ON COOPERATIVE TRILATERATION Vladimi CIPOV1, Lubomi DOBOS1, Jan PAPAJ1 1Depa men o Elec onics and Mul imedia Communica ions, Facul y o Elec ical Enginee ing and In o ma ics, Technical Uni e si y o Kosice, Le na 9, 042 00 Kosice, Slo ak Republic ladimi .cipo @ uke.sk, lubomi .dobos@ uke.sk, jan.papa[email p o ec ed] Abs ac . This pape p o ides a b ie su ey o he Time o A i al (ToA) anging me hod o en used in he Range- based localiza ion o node dis ance es ima ion. I is ocused especially on he Non Line-o -Sigh (NLoS) channel iden i ica ion – one o he dominan ac o s ha nega i e a ec he loca ion accu acy. I deals wi h he imp o emen o he ecei ed signal a i al ime de e mina ion in he case o NLoS communica ion wi h unde ec ed di ec pa h. The low complexi y NLoS mi iga ion me hod is p oposed in his pape ha es ima es he ime o a i al o he missing di ec pa h as a mean o he ime delays o e lec ed pa hs. This me hod is implemen ed in he coope a i e posi ioning algo i hm based on he ci cula ila e a ion. The IEEE 802.15.4a s a is ical channel model is used o simula e he mobile node communica ion. Keywo ds LoS/NLoS iden i ica ion, NLoS mi iga ion, posi ioning, ToA, ila e a ion. 1. In oduc ion In he ield o mobile communica ions, he wi eless nodes loca ion p oblem has gained inc easing in e es . Loca ion es ima ion is a complex p oblem. I has been in es iga ed ex ensi ely in he li e a u e in he las ew yea s, whe e au ho s sol ed a ious p oblems. I is gene ally ue ha he posi ion de e mina ion p oblem consis s o wo s eps. A i s , localiza ion pa ame e s mus be es ima ed. In acco d wi h his ac posi ioning sys ems a e di e en ia ed o he Range-based and Range- ee [13]. Finaly, ob ained pa ame e s a e used o posi ion calcula ion ia one o he localiza ion algo i hms, which a e classi ied as Ancho -based o Ancho - ee [12]. In his pape , we concen a e on Range-based localiza ion. A a ie y o me hods, which a e based on Recei ed Signal S engh (RSS), Time o A i al (ToA) o Angle o A i al (AoA), [2], a e a ailable o pe o m he ange measu emen s. We p e e he ToA anging echnique in combina ion wi h Ul a Wide-Band (UWB) communica ion echnology, which is one o he mos p omising app oaches o he mobile localiza ion and has a g ea po en ial o accu a e anging especially in he indoo en i onmen . Due o a e y wide bandwid h o he UWB sys ems, hese a e capable o esol e indi idual mul ipa h componen s in he ecei ed channel impulse esponse and o de e mine he ime o hei a i al e y p ecisely. Ka eh Pahla an and his eam o esea che s engage in he a ea o ToA es ima ion. The p oblem o ToA es ima ion in he case o unde ec ed di ec pa h and i s iden i ica ion can be ound in [6], [14]. The impac on he node dis ance es ima ion accu acy using a di e en sys em bandwid h is also analyzed. Mo e ela ed wo ks which deal wi h ToA can be ound in sec ion 2. We ha e p oposed he low complexi y me hod o ToA node dis ance es ima ion imp o emen and u ilized i in he p oposed coope a i e posi ioning algo i hm based on ci cula ila e a ion. 2. ToA Node Dis ance Es ima ion and LoS/NLoS Iden i ica ion Time o A i al is he echnique whe e he node dis ance can be es ima ed as he p oduc o he measu ed signal p opaga ion delay and he speed o ligh [1]: cd  , (1) whe e d ep esen s he node dis ance, c he speed o ligh and he es ima ed ime o a i al o he ecei ed signal. Le he Channel Impulse Response (CIR) o he ecei ed signal be ep esen ed as [5]:        L lll A h 1  , (2) INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE 212 © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING whe e L ep esen s he numbe o mul ipa h componen s, Al and τl a e he signal ampli ude and he ime delay o he l- h mul ipa h componen , espec i ely. In gene al, he ime o a i al o he i s a i ing pa h, he i s CIR componen , is conside ed as he ime o a i al o he ecei ed signal. The p oblem occu s when he di ec pa h is missing in he channel impulse esponse because i is blocked o a enua ed unde he de ec ion h eshold o he ecei e . Wi eless communica ion channel p o ile can be classi ied o [6]:  Line-o -Sigh (LoS) wi h Dominan -Di ec -Pa h (DDP). In his case, he di ec pa h is he s onges and he i s de ec ed pa h in he channel p o ile and i can be de ec ed by he ecei e . The e a e no conside able obs acles be ween he ansmi e and he ecei e .  Non Line-o -Sigh (NLoS) wi h Non Dominan - Di ec -Pa h (NDDP). Line-o -Sigh communica - ion be ween a ansmi e and a ecei e does no exis . In NDDP channel p o ile, he di ec pa h is no he s onges pa h o he CIR, howe e , i is s ill de ec able because i is ecei ed abo e he de ec ion h eshold o he ecei e .  Non Line-o -Sigh (NLoS) wi h Unde ec ed- Di ec -Pa h (UDP). In UDP channels, he di ec pa h goes below he de ec ion h eshold o he ecei e while o he pa hs a e s ill de ec able. The ecei e assumes he i s de ec ed peak as a di ec pa h which causes conside able dis ance es ima ion e o s. The pe o mance o he Range-based localiza ion sys ems based on ToA node dis ance es ima ion echniques mainly depends on he p esence o Line-o - Sigh communica ion be ween he ansmi e - ecei e pai s. NLoS adio p opaga ion is one o he mos dominan ac o s ha a ec he posi ioning accu acy [3]. The absence o a di ec pa h in he ecei ed signal esul s in an ex a-delay o he ToA because he signal a els an ex a dis ance ha leads o he inco ec loca ion [1]. Se e al LoS/NLoS iden i ica ion me hods ha e been p oposed [3], [5]. One o he mos basic LoS/NLoS iden i ica ion me hods a e based on he p io knowledge o s a is ics o he signal ecei ed in LoS condi ions. Du ing he eal- ime localiza ion, measu emen s a e aken and he s a is ics o hese measu emen s a e calcula ed. When he calcula ed s a is ics a e signi ican ly di e en om he e e ence s a is ics, he ecei ed signal is assumed o be co up ed by NLoS communica ion. Tha can be exp essed wi h simple bina y de ec ion scheme, whe e he de ec ion is pe o med by ex ac ing a ce ain numbe o ecei ed signal ea u es such as Ku osis, Mean Excess Delay o RMS Delay Sp ead o he Mul ipa h Channel and applying he classical decision heo y [1], [5]:         LoSp NLoSp Np pH0 LoS| LoS|    , (3)         LoSp NLoSp Np pH1 LoS| LoS|    , (4) whe e p(γ|LoS) and p(γ|NLoS) ep esen , he PDFs o he se o measu ed ecei ed signal ea u es γ = {γ1, γ2,…, γN} unde LoS and NLoS condi ions, p(LoS) and p(NLoS) a e he p io p obabili ies o he LoS and NLoS e en s, and Н0 and Н1 deno e he LoS and NLoS signal p opaga ion condi ions. 2.1. Dis ibu ion Tes s In he case o LoS condi ions he samples o he ecei ed signal en elope ha e dis ibu ions di e en om hose ecei ed in NLoS condi ions. I he dis ibu ion o he LoS is known, his ac can be used o iden i ica ion o he communica ion channel cha ac e is ics. The aim o he dis ibu ion es s is o es , whe he he samples o he ecei ed signal en elope belong o a speci ic dis ibu ion, so ha he LoS o NLoS condi ion can be iden i ied. A numbe o well-known es s o iden i y he communica - ion channel cha ac e is ics a e b ie ly desc ibed in [3]. In he ollowing ex , he mos commonly used es Kolmogo o -Smi no Tes is explained. The objec i e o he Kolmogo o -Smi no Tes is o iden i y whe he he ecei ed signal samples o igina e om he known dis ibu ion ela ed o he LoS condi ions. Suppose ha he e a e L measu emen s o de ed as 1, 2,… L. The empi ical cumula i e dis ibu ion unc ion o hese obse a ions (measu - emen s) is de ined as [3]:     Li L i iF ,...2,1; 0 , (5) whe e (i) is he numbe o obse a ion poin s. The ollowing hypo hesis can be o mula ed [9]:       iFiFiH exp00 ;:  , (6)       iFiFiH exp01 ;:  , (7) whe e Fexp(i) is he cumula i e dis ibu ion unc ion o he known expec ed p obabili y dis ibu ion ypical o he signal samples ecei ed in he LoS condi ions. The ask o he Kolmogo o -Smi no Tes is o ind he D-s a is ic, which is de ined as he g ea es disc epancy be ween he measu ed and he expec ed comula i e dis ibu ion unc ions as [3]:     iFiFD Li exp0 1 max   . (8) The compu ed D-s a is ic is compa ed agains he c i ical D´-s a is ic o he same sample size, which can be compu ed based on he gi en le el o signi icance. When he le el o signi icance equals 0,05 he c i ical D´- s a is ic is [3]: L 1,358 ´D . (9) I D ≤ D´, he hypo hesis is alida ed. The INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 213 dis ibu ion unc ion o he measu ed ecei ed signal samples co esponds wi h he expec ed dis ibu ion unc ion ela ed o he LoS condi ions. O he wise, i D > D´, he dis ibu ion unc ion o he measu ed samples is no conside ed as he expec ed dis ibu ion and, hus, hypo hesis is ejec ed. The ecei ed signal samples o igina e in NLoS communica ion [3], [9]. 2.2. Ku osis Pa ame e The ku osis is a s a is ical pa ame e ha indica es he a iance a ia ion o he signal ampli udes. I is de ined as he a io o he ou h o de momen o he da a o he squa e o he second o de momen [5]:                   4 4 2 2 4 h h h h hE hE hE           , (10) whe e μ/h/ and σ/h/ a e he mean and s anda d de ia ion o he ecei ed signal samples h( ), espec i ely. Ku osis is cha ac e ized by he high alue o he signal ecei ed in LoS condi ions [1], and by low alue o signal ecei ed in NLoS condi ion ( he signal id mo e noise-like),[8]. Two ways can be used o LoS/NLoS decision. Kolmogo o -Smi no goodness-o - i es can be used o analyze how well he measu ed da a cha ac e ize he p io dis ibu ion which ep esen s he LoS channel [5] o he decision is simply aken as [1]: NLoSi    , (11) LoSi    , (12) whe e λκ is he h eshold alue be ween he LoS and NLoS condi ions. I Ku osis akes he alues abo e he de ined h eshold i goes o LoS condi ion and ice e sa, i i akes he alues less han he de ined h eshold i goes o NLoS condi ion. The ad an age o Ku osis is ha i can be calcula ed di ec ly on he ecei ed signal, no es ima ion algo i hm is needed. This keeps easy and quick he iden i ica ion p ocess and i implies ha no es ima ion e o s o he es ima ion algo i hm a e in oduced [8]. The simila analysis as discussed in he p e ious pa can be pe o med using o he pa ame e s named Mean Excess Delay τm and RMS Delay Sp ead τ ms. While he Ku osis p o ides in o ma ion abou he ampli ude s a is ics o he ecei ed signal samples, hese wo pa ame e s p o ide he s a is ic ha cha ac e izes he delay in o ma ion o he mul ipa h channel ob ained om i s Powe Delay P o ile [5]. These pa ame e s a e exp essed as [10]:        kk kkk mP P    , (13)   2 2mm ms   , (14) whe e P(τk) is he powe o he k- h pa h o he Powe Delay P o ile wi h ime delay τk and        kk kk mP P    2 2 . (15) The comp ehensi e desc ip ion o he LoS/NLoS iden i ica ion me hods he eade can ound in [3]. To achie e sa is ac o y node dis ance es ima ion, i is desi able o de e mine whe he he communica ion pa h be ween a ansmi e - ecei e pai is LoS o NLoS. I i is iden i ied as NLoS, he impac on localiza ion accu acy can be supp essed ei he by he simple disca ding o he measu emen s iden i ied as NLoS o by using some o he NLoS mi iga ion echniques [4]. The i s men ioned app oach is possible only when he e a e enough measu emen s iden i ied as LoS, he e o e he app oach o using he NLoS mi iga ion echniques seems o be p e e able. 3. B ie O e iew o he Localiza ion Sys em Based on Coope a i e T ila e a ion Philosophy o he posi ioning sys em is based on he ila e a ion p inciple used as a undamen al localiza ion me hod o cellula mobile ne wo ks whe e each mobile node, which has he connec ion wi h minimum h ee e e ence nodes, ancho s, can be loca ed. Th ee ancho s wi h known posi ion a e su icien o wo-dimensional localiza ion. This me hod belongs o he Range-based posi ioning sys ems, whe e one o he localiza ion pa ame e s mus be de e mined in o de o calcula e he inal posi ion o he localized node. Cu en ly we use he measu emen o he Time o A i al pa ame e de e mined om he wi eless channel impulse esponse. The posi ioning sys em also belongs in o he Ancho - based sys ems he e o e i assumes he exis ence o a couple o eal e e ence nodes wi h known loca ion. The algo i hm consis s o mo e phases. Each node si ua ed in he icini y o minimum h ee e e ence nodes wi h known loca ion, is able o calcula e i s own posi ion. In he i s phase all mobile nodes which a e in he ange o a leas 3 s eady eal beacons a e localized. The second and e e y o he phase a e like he i s one. Di e ence is ha all mobile nodes al eady localized in he p e ious phase become i ual beacons. The algo i hm is inished when:  posi ions o all mobile nodes we e de e mined al eady,  i is no possible ano he mobile nodes posi ion de e mine (unde e mined nodes ha e no su icien numbe o ancho s in ange). INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE 214 © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING E e y phase o he p oposed algo i hm consis s o he ollowing ou s eps:  selec ion o a mobile node sui able o localiza ion p ocess,  he calcula ion o he dis ances be ween he mobile node which should be loca ed and all ancho s in i s ange,  selec ion o he app op ia e ancho s in o de o calcula e he unknown node loca ion,  ila e a ion and posi ion calcula ion o unknown mobile node. A he beginning o he each phase he nodes, which ha e no been al eady calcula ed he loca ion a e selec ed. Each o he nodes includes he da abase o i s neighbou s, he dis ances o hem acco ding o he measu ed ToA pa ame e and also he in o ma ion i hese neighbou s a e ancho s o no . F om his da abase o he a ailable e e ence nodes only one iple is selec ed using he ollowing p ocedu e:  e e y ancho iple ha is conside ed is c ea ed,  only hose iple s whe e all pai s o ci cles a e in e sec ed a e conside ed,  he iple which include he ancho s wi h s eady posi ion a e p e e ed,  his nea es iple (acco ding o ToA pa ame e ) is p e e ed om all. This iple c ea es he iple o ancho s sui able o calcula ion o he inal posi ion o unknown node by ila e a ion. I a sui able iple o ancho s in he ange o unknown node exis s, he localiza ion p ocess can be ca ied ou . As i is s a ed abo e, he p ocess o ila e a ion is used o calcula ion o he posi ion o unknown nodes whe e [x,y] ep esen he coo dina es o he unknown node (which should be calcula ed), [xi,j,k,yi,j,k] ep esen he loca ion o he e e ence nodes and i,j,k ep esen he es ima ed node dis ances be ween unknown node and he e e ence nodes sepa a ely:     2,, 2 ,, 2 ,, kjikjikji yyxx  . (16) Ideally, he inal posi ion is ep esen ed by he only common in e sec ion o h ee ci cles. The nega i e impac o wi eless communica ion channel causes inaccu a e calcula ion o dis ances be ween nodes. Hence he inal posi ion is calcula ed as a cen e o he a ea which is ep esen ed by a iple o sui able in e sec ions. 4. Simula ions and Resul s In ou simula ions we ha e used he exis ing model o he wi eless channel impulse esponse gene a ion o IEEE 802.15.4a ul a wideband echnology, which is desc ibed in mo e de ails in [11]. I is he esul o he esea ch ac i i y o he membe s o he Mi subishi Elec ic Resea ch Labo a o ies and p o ides he gene a ion o he channel impulse esponse o di e en ypes o he en i onmen such as esiden ial, o ice, open ou doo and indus ial. In ou simula ions we ha e used he CIR o “LoS and NLoS OFFICE” en i onmen . In mos cases he ime o a i al o he ecei ed signal is assumed as he ime o a i al o he i s de ec ed pa h. The p oblem occu s, when he di ec pa h is missing in he ecei ed signal channel impulse esponse. This ac causes conside able dis ance es ima ion e o s, which leads o he inco ec localiza ion. Fo NLoS mi iga ion p oblem, especially in case o NLoS communica ion wi h unde ec ed di ec pa h, we ha e p oposed he low complexi y NLoS mi iga ion echnique o ToA es ima ion desc ibed in he ollowing pa . In Fig. 1, he diag am o he ToA es ima ion o di e en ypes o communica ion channel is in oduced. Fig. 1: Diag am o he ToA es ima ion o di e en ypes o communica ion channel. In pa o LoS/NLoS iden i ica ion we ha e used he Ku osis pa ame e “KP” calcula ion wi h a de ec ion h eshold be ween he LoS and NLoS communica ion condi ions o 100. The desi ed h eshold alue o KP has been ob ained om he expe imen al obse a ions o se e al assumed h esholds om 60 o 220, whe e 100 has b ough he mos success ul esul s o LoS/NLoS iden i ica ion, Fig. 2. Than in he simula ions, acco ding o he calcula ed KP he algo i hm decided he communica ion condi ions. I KP ≥ 100 i iden i ied he “LoS OFFICE” en i onmen , else i KP < 100 he “NLoS OFFICE” en i onmen was iden i ied. Using 1000- imes andomly gene a ed CIR o “OFFICE” en i onmen he LoS/NLoS iden i ica ion by using Ku osis calcula ion was success ul in 84,7 %. The pa o IDENTIFICATION o di ec pa h p esence was no he aim o his pape . I will be he aim o ou esea ch ac i i y in he nex pe iod. In his pape we ha e ocused on LoS es ima ion p oblem in he case o NLoS channel wi h Unde ec ed Di ec Pa h (UDP). We p oposed he low complexi y UDP mi iga ion me hod in o de o imp o e he dis ance es ima ion, which is nex explained using he conc e e example o he ansmi e - ecei e pai 10 m dis an . The ecei e ecei ed he signal as is depic ed in Fig. 3 ( he ime componen s om 1 o 9). I can be seen ha in he ecei ed channel INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 215 impulse esponse he di ec pa h is missing. We need o es ima e he assumed ime o a i al o he blocked di ec pa h. The co ec ion ToA pa ame e can be ob ained using he ollowing p ocedu e: 1 )( 21       k C k iii LoS , (17) whe e i is he ime o a i al o he i- h pa h ecei ed abo e he le el o signi icance, which ep esen s he pa hs wi hin 10 dB om maximum peak, k is he numbe o signi ican pa hs and CLoS is he mean o he ime di e ences be ween pai s o hese neighbou ing pa hs, named as “ToA co ec ion pa ame e ”. Fig. 2: Dependence o he success ul a e on he KP h eshold. Fig. 3: LoS es ima ion explana ion. The assumed ime o a i al o he es ima ed LoS pa h is de i ed as: LoSLoSes ima ed C ToA  1 . (18) This example is explained using Tab. 1, which con ains he imes o a i al o he men ioned signi ican pa hs wi h he di e ences be ween hem. As i can be seen in he Tab. 2 and Tab. 3, he p oposed NLoS mi iga ion me hod p oduced be e esul s o he es ima ed ToA pa ame e and inal dis ance es ima ion o 1,414 m, which ep esen s he imp o emen o dis ance es ima ion e o o 41 %. This p ocedu e has been es ed on 1000- imes andomly gene a ed CIRs o ansmi e - ecei e pai s dis an a 10 m. Gene ally, he dis ance es ima ion e o has been educed by 22,6 %, Tab. 4. Tab.1: Time o a i al o he signi ican pa hs and he ime di e ences be ween hem. i i [ns] i- i-1 [ns] 1 41,3 --- 2 44,0 2,7 3 49,0 5,0 4 53,7 4,7 5 56,3 2,6 6 62,7 6,4 7 69,3 6,6 8 74,3 5,0 9 79,0 4,7 Tab.2: ToA and dis ance es ima ion by using he i s de ec ed peak. ToA 1 [ns] Es ima ed dis ance [m] 41,3 12,4 Tab.3: ToA and dis ance es ima ion by using he p oposed NLoS mi iga ion me hod o ToA es ima ion enhancemen . CLoS [ns] ToAes ima ed-LoS [ns] Es ima ed dis ance [ns] 4,71 36,62 10,986 Tab.4: The compa ison o he dis ance es ima ion e o using bo h ToA es ima ion echniques. ToA es ima ion Dis ance es ima ion e o [m] o nodes dis an a 10 m Fi s de ec ed pa h 1,541 NLoS mi iga ion me hod 1,193 Finally, he p oposed ToA es ima ion me hod has been es ed also in coope a i e ila e a ion based algo i hm desc ibed in he sec ion 3. We simula ed only he ha sh communica ion condi ions be ween pai s o mobile nodes – NLoS wi h UDP. We ha e s udied he impac o he p oposed NLoS mi iga ion me hod on he po en ial enhancemen o he dis ance es ima ion e o . Ou simula ions we e ca ied ou in MATLAB p og amming en i onmen and o s a is ical ele ance we e epea ed one hund ed imes. We ha e used he ne wo k which consis ed o he 40 mobile nodes deployed on he a ea o 30  30 m wi h all ecei e s’ adio ange o 10 m. Th ee s eady iangle-shaped beacon nodes we e loca ed in he middle o localiza ion a ea. We assumed p ecise ime synch oniza ion be ween nodes. I we used he i s algo i hm, whe e he ToA pa ame e is de e mined acco ding o he ime o a i al o he i s de ec ed peak, he localiza ion e o was 29,96 % in compa ison wi h he size o a ea side. By using he p oposed NLoS mi iga ion me hod he localiza ion e o was educed o 27,77 %. In bo h cases he beha iou o he algo i hm was success ul enough wi h a numbe o he localized nodes abo e 90 %, Tab. 5. INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE 216 © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING Tab.5: Posi ioning algo i hm e alua ion a e p oposed NLoS mi iga ion echnique implemen a ion. Used ToA es ima ion me hod Localiza ion e o [%] Numbe o success ully localized nodes [%] Fi s de ec ed pa h 29,96 91,65 NLoS mi iga ion me hod 27,77 93,30 5. Conclusion This pape p esen s he low complexi y NLoS mi iga ion echnique and i s applica ion in he p oposed coope a i e localiza ion algo i hm based on ci cula ila e a ion. In gene al, he p oposed me hod o ToA es ima ion enhancemen imp o es he ime o a i al accu acy, bu i has se e al d awbacks. In some cases, i he e a e less signi ican pa hs in he channel powe delay p o ile which a e mo e dis an om each o he , he ToA es ima ion can be inaccu a e. The me hod, how o imp o e he p oposed NLoS mi iga ion me hod will be he aim o he u u e esea ch ac i i y. Acknowledgemen s This wo k has been pe o med pa ially in he amewo k o he EU ICT P ojec INDECT (FP7-218086). Re e ences [1] DECARLI, N., D. DARDARI, S. GEIZICI and A. A. D'AMICO. LOS/NLOS De ec ion o UWB Signals: A Compa a i e S udy Using Expe imen al Da a. In: IEEE In e na ional Symposium on Wi eless Pe asi e Compu ing (ISWPC). Modena: IEEE, 2010. pp. 169–173. ISBN 978-1- 4244-6855-3. DOI: 10.1109/ISWPC.2010.5483704. [2] VOSSIEK, M., L. WIEBKING, P. GULDEN, J. WIEGHARDT, C. HOFFMANN and P. HEIDE. Wi eless local posi ioning. Mic owa e Magazine. 2003, ol. 4, iss. 4, pp. 77- 86. ISSN 1527-3342. DOI: 10.1109/MMW.2003.1266069. [3] YU, K., I. SHARP and J. GUO. G ound-Based Wi eless Posi ioning. Chiches e : John Wiley & Sons, 2009. ISBN 978- 0-470-74704-9. [4] GUVENC, I. and Ch.-Ch. CHONG. A Su ey on TOA Based Wi eless Localiza ion and NLOS Mi iga ion Techniques. Jou nal: IEEE Communica ions Su eys & Tu o ials. 2009, ol. 11, iss. 3, pp. 107-124. ISSN 1553-877X. DOI: 10.1109/SURV.2009.090308. [5] GUVENC, I., Ch.-Ch. CHONG and F. WATANABE. NLOS Iden i ica ion and Mi iga ion o UWB Localiza ion Sys ems. In: Wi eless Communica ions and Ne wo king Con e ence, 2007. WCNC 2007. 2007. IEEE. Kowloon: IEEE, 2007, pp. 1571-1576. ISSN 1525-3511. ISBN 1-4244-0658-7. DOI: 10.1109/WCNC.2007.296. [6] HATAMI, Ahmad. Applica ion o Channel Modeling o Indoo Localiza ion Using TOA and RSS. Wo ces e , 2006. Disse a ion Thesis. Wo ces e Poly echnic Ins i u e. [7] ALSINDI, Naye , C. DUAN, J. ZHANG and T. TSUBOI. NLOS Channel Iden i ica ion and Mi iga ion in Ul a Wideband ToA-based Wi eless Senso Ne wo ks. In: P oceedings o 6 h Wo kshop on Posi ioning, Na iga ion and Communica ion (WPNC). Hanno e : IEEE, 2009. pp. 59–66. ISBN 978-1-4244-3292-9. DOI: 10.1109/WPNC.2009.4907804. [8] MUCCHI, L. and P. MARCOCCI. A new UWB indoo channel iden i ica ion me hod. In: C ownCom 2007. 2nd In e na ional Con e ence on Cogni i e Radio O ien ed Wi eless Ne wo ks and Communica ions, 2007. O lando: IEEE, pp. 58–62. ISBN 978-1-4244-0814-6. DOI: 10.1109/CROWNCOM.2007.4549772. [9] TOMAN, Edua d. S a is icka in e e encia caso ych adoch. B a isla a, 2007. Diploma Thesis. Comenius Uni e si y in B a isla a. [10] DOBOS, L. and F. JAKAB. Mul imedia in mobile ne wo ks. Kosice: TU-FEI, 2005. ISBN 80-8086-000-9. [11] MOLISCH, And eas F., Kannan BALAKRISHNAN, Dajana CASSIOLI, Chia-Chin CHONG, Shah ia EMAMI, And ew FORT, Johan KAREDAL, Jue gen KUNISCH, Hans SCHANTZ, Ul ich SCHUSTER and Kai SIWIAK. IEEE 802.15.4a Channel Model – Final Repo . In: Documen IEEE 802.1504-0062-02-004a [online]. 2005. A ailable a : h p://g oupe .ieee.o g/g oups/802/15/pub/04/15-04-0662-02- 004a-channel-model- inal- epo - 1.pd . [12] POVENDRAN, R., C. WANG and R. SUMIT. Secu e Localiza ion and Time Synch oniza ion o Wi eless Senso and Ad hoc Ne wo ks. New Yo k: Sp inge Science+Business Media, 2007. ISBN 978-0-387-32721-1. [13] SRINIVASAN, A. and J. WU. A Su ey on Secu e Localiza ion in Wi eless Senso Ne wo ks. Boca Ra on: CRC P ess, Taylo and F ancis G oup, 2008. [14] HEIDARI, M., F. O. AKGUL and K. PAHLAVAN. Iden i ica ion o he Absence o Di ec Pa h in Indoo Localiza ion Sys ems. In: IEEE 18 h In e na ional Symposium on Pe sonal, Indoo and Mobile Radio Communica ions, 2007. PIMRC 2007. A hens: IEEE, 2007. pp. 1–6. ISBN 978-1-4244- 1144-3. DOI: 10.1109/PIMRC.2007.4394450. Abou Au ho s Vladimi CIPOV was bo n in Banska Bys ica, Slo ak epublic in 1985. He ecei ed his M.Sc. om Technical Uni e si y o Kosice, Facul y o Elec ical Enginee ing and In o ma ics in 2009. He g adua ed wi h majo in Elec onics and Telecommunica ions Enginee ing. Today, he is Ph.D. s uden and his scien i ic esea ch a ea is: Localiza ion in Wi eless Mobile Ad-hoc Ne wo ks. Lubomi DOBOS was bo n in V ano n/Toplou, Slo ak Republic in 1956. He ecei ed he Ing. (M.Sc) deg ee and Ph.D. deg ee in Radioelec onics om he Facul y o Elec ical Enginee ing, Technical Uni e si y o Kosice, in 1980 and 1989, espec i ely. He de ended his habili a ion wo k - B oadband Wi eless Ne wo ks o Mul imedia Se ices in 1999. His scien i ic esea ch a ea is: b oad- band in o ma ion and elecommunica ion echnologies, mul imedia sys ems, elecommunica ions ne wo ks and se ices, mobile ne wo ks, ou ing p o ocols. Jan PAPAJ was bo n in Lip o sky Mikulas, Slo ak Republic in 1977. He is g adua ed a he Depa men o Compu e s and In o ma ics in 2001, Facul y o Elec ical INFORMATION AND COMMUNICATION TECHNOLOGIES AND SERVICES VOLUME: 10 | NUMBER: 4 | 2012 | SPECIAL ISSUE © 2012 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 217 Enginee ing and In o ma ics a Technical Uni e si y in Kosice. He ob ained his Ph.D. deg ee in Telecommunica- ions om he Facul y o Elec ical Enginee ing, Techni- cal Uni e si y o Kosice in 2010. His esea ch in e es s co e he ields o MANETs, QoS and secu i y, ou ing p o ocols, oppo unis ic and senso ne wo ks.