COMPARATIVE ANALYSIS OF ULTRA WIDEBAND (UWB) IEEE A CHANNEL MODELS FOR nlos PROPAGATION ENVIRONMENTS

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1 COMPARATIVE ANALYSIS OF ULTRA WIDEBAND (UWB) IEEE A CHANNEL MODELS FOR nlos PROPAGATION ENVIRONMENTS Ms. Jina H. She PG Student C.C.E.T, Wadhwan, Gujarat, Dr. K. H. Wandra Director (Academics) C.C.E.T, Wadhwan, Gujarat Abstract- As per high speed demand grows, Utra Wide Band (UWB) technoogy is gaining popuarity among researchers and companies due to its wireess ink wi high data rate. Federa Communications Commission aocated 7500 MHz of spectrum for unicensed use of commercia utra-wideband (UWB) communication devices. Wireess experts are now consider is spectrum to be utiized wi a variety of techniques, and not just reated wi generation and detection of RF puses. There are many differences between narrow-band and UWB systems. A e wireess systems must be abe to dea wi e chaenges in mutipa environment which can cause refections at e receiver. For narrow band systems it wi not be possibe to resove refections by receiver as narrow-band system bandwid is ess an coherence bandwid of e channe. Instead, e arge bandwid of UWB is abe to capture refections in e channe. This paper gives an introduction about indoor wireess channe modes ike Poisson mode, Δ-k mode, and IEEE mode. Finay wi reference to indoor channe mutipa arrives in custer, modified S-V mode is described and is used to simuate e UWB channe mode. This introduces UWB channe characteristics and focuses on e mode for high-data rate UWB appications Simuation resuts of e channe mode in nlos environments for 0-4m and 4-10m ranges are presented and compared. I. INTRODUCTION In 00, e United States Federa Communication Commission (FCC) aocated 7.5 GHz spectrum from 3.1 GHz to 10.6 GHz for utra-wideband (UWB) devices. In recent years, utra wideband (UWB) communications has received great interest from bo e research community and industry. The potentia streng of e UWB radio technique ies in its use of extremey wide transmission bandwids, which resuts in desirabe capabiities incuding accurate position ocation and ranging, ack of significant fading, high mutipe access capabiity, covert communications, and possibe easier materia penetration. Because of e restrictions on e transmit power, UWB communications are best suited for short-range communications: sensor networks and persona area networks (PANs). IEEE has estabished new standard IEEE a and goa of is new standard are data rates of up to 110 Mb/s at 10 m distance, 00 Mb/s at 4 m distance, and higher data rates at smaer distances. UWB communication invoves transmitting data using very short puses us occupying very arge bandwid. The energy of e UWB signas is spread over a arge spectrum us having e inherent property of being overaid over existing systems in at frequency range. The advantage of using short puses is fine timing resoution us more channe mutipa can be resoved. The IEEE a channe mode encompasses e main features of e Saeh- Vaenzuea channe mode, where mutipa rays arrive in custers and eir ampitudes foow doube-exponentia decay. Nevereess, is channe mode differs from Saeh- Vaenzuea in terms of mutipa-attenuation-factor ampitude distribution to be og-norma. Large bandwid can give rise to new effects. For exampe, ony few mutipa components overap wiin each resovabe deay bin (resovabe run eng is 3 cm), so e centra imit eorem is no onger appicabe, and e ampitude fading statistics are no onger Rayeigh. Aso, ere can be deay bins into which no MPCs fa, and us are empty. It en becomes necessary to characterize e ikeihood at is happens, and at an empty bin is foowed by fu one. II. UWB MULTIPATH INDOOR CHANNEL MODEL The testing and modeing of UWB system propagation channe has become a foca research in recent years. A mass of experiments data showed at e UWB channe mutipas arriving in custers, so e UWB channe mode shoud incarnate is new pecuiarity in e mutipa mode. The custering of e mutipa arrivas is e direct resut of dispersion bodies teem togeer in actua physics environment. This characteristic can aso be observed in UWB channe, and at time-of-arriva of distinguished pa distributing asymmetricay. In e UWB mutipa mode, e main

2 parameters are excess deay, RMS deay spread, power decay profie, number of mutipa components. A. The Poisson mode Poisson mode is e pioneer UWB channe mode. Suppose ere is ony one custer of mutipas in impuse response, e arrived mutipa components are regarded as a Poisson process. The arriving rate of e process is λ, and e pa fading exponentiay, e time attenuation constant is γ, e pa ampitude obeys og-norma distribution and e standard variance is σ. B. Δ-k mode The Poisson distribution is e statistica mode used to determine e timing of random events at. If L denotes e number of pas occurring in a given interva of time duration T, e Poisson distribution requires e prob( L ) (1)! However comparison between e arriva times estimated by e Poisson distribution and e measurement has ceary demonstrated e inadequacy of e mode to describe e arriva times for wideband puses. This is mainy due to e fact at e scattering in an indoor channe is not competey random and e position of e scattering objects resuts in deviation from e standard Poison distribution. The Δ-K mode, a modified Poisson process, was proposed by Turin and Suzuki in 197. This mode takes into account e custering property of pas caused by e grouping properties of e scattering objects. The mode operates ike a state machine wi two states, in state 1 e mean is λ 0 (t) and in state e mean is Kλ 0 (t). The process starts out in state 1 and if a pa arrives at time t, a transition is made to state. If no furer pas arrive in e time interva (t, t+ Δ), a transition is made back to state 1. For K=1 and Δ =0 e process is a standard Poison distribution but for K>1, e arriva of a pa at time t increases e probabiity of receiving more pas in e time interva (t, t+ Δ). The Δ-K mode has shown a good fit to e empirica data coected in severa urban mobie environments. On e oer hand e mode is not best suited for UWB channes since two independent Poisson distributions provide more fexibiity in determining e custer and ray arriva times when compared to e Δ-K mode. C. S-V/IEEE a mode Saeh- Vaenzuea mode is e universa statistic mode of indoor dispersion channe impuse response. This mode describes e mutipas arriving in custers; at many cases can best fit e statistics of e measured data. In order to perfecty inoscuate wi e UWB measurement data, e IEEE workgroup made some modification on e S-V mode. Concretey, using og-norma distribution to express mutipa pus ampitude, and using anoer og-norma stochastic variabe to express genera mutipa pus fuctuation. Maematicay, e impuse response is described as L K i i i i ik, k, 0 k0 h ( t) X ( t T ) Where i are e mutipa gain coefficients, i k, T is e deay of custer, τ k, is e deay of e k mutipa component reative to e custer arriva time T, x i represents e og-norma shadowing. i refers to e i reaization. By definition, we have τ 0, = 0. The distribution of custer arriva time and e ray arriva time are given by p T / T 1 exp T / T 1, 0 p k, ( k1), k, ( k1), () (3) / exp /, k 0 (4) The channe coefficients are defined as a product of smascae and arge-scae fading coefficients, (5) k, k, k, The ampitude statistics of e measurements were found to best fit e og-norma distribution raer an e Rayeigh at was used in e origina S-V mode. In addition, e arge-scae fading is aso og-normay distributed. 0og10( ) Norma (, ) (6) Or Where And k, k, 1 k, 10 ( k, n1n) 0 (7) n1 Norma (0, ) (8) 1 n Norma (0, ) (9) The behaviour of e (averaged) power deay profie is / T/ k, E[ ] e e k, 0 (10) This refects e exponentia decay of each custer, as we as e decay of e tota custer power wi deay. In e above equations, p k, is equiprobabe ±1 to account for signa inversion due to refections. to account for signa inversion due to refections. The μ k, is given by

3 10n( 0 ) 10 T / 10 k, / ( 1 )n(10) k, (11) n(10) 0 III. SIMULATION AND COMPARATIVE ANALYSIS OF UWB CHANNEL MODELS D. UWB Channe Parameters Parameters are used to mode UWB channe. in statistica anaysis mode can be tuned to different propagation environment by adjusting appropriate vaues of parameters. Beow tabe shows vaues of parameters which came from e measurements were done in e nlos environments in e range of 0-4m and 4-10m. TABLE 1. CHANNEL MODEL COMPONENTS AND PARAMETERS Component/ Meaning Parameter T Deay of e k, 1 x Arriva time of e first pa of e k pa wiin e custer custer reative to e first pa arriva time, Custer arriva rate Ray arriva rate, i.e., e arriva rate of pa wiin each custer Custer decay factor Ray decay factor Standard deviation of custer og-norma fading term (db) Standard deviation of ray og-norma fading term (db) Standard deviation of og-norma shadowing term for mutipa reaization T typicay caed e "channe." In order to evauate and design wireess systems, we must create modes of e channe. A reiabe channe mode, which captures e important characteristics of e channe, is a vita prerequisite for system design. The goa of e channe mode is to capture e mutipa characteristics of typica environments where IEEE a devices are expected to operate. The mode shoud be reativey simpe to use in order to aow PHY proposers to use e mode and, in a timey manner, evauate e performance of eir PHY in typica operationa environments. In addition, it shoud be refective of actua channe measurements. Since it may be difficut for a singe mode to refect a of e possibe channe environments and characteristics, e group chose to try matching e foowing primary characteristics of e mutipa channe: RMS deay spread Power decay profie Number of mutipa components (defined as e number of mutipa arrivas at are wiin 10 db of e peak mutipa arriva) The actua channes resuting from e mode may have severa pas at are much weaker an 10 db from e peak, whie e above characteristic was simpy used to compare to measurement resuts. F. Simuation resuts and anaysis TABLE. VALUES OF CHANNEL PARAMETERS FOR DIFFERENT PROPAGATION ENVIRONMENT Channe Parameters CH 1 CH Sampe Time(nSec) Symbo Period Symbo Per Fade LAMBDA Lambda GAMMA Gamma sigma sigma std_shadow This mode is based on NLOS (0-4 m) channe measurements reported in [7]. This mode is based on NLOS (4-10 m) channe measurements reported in [7]. E. UWB Channe Characteristics to be modeed The received signa in any communications system is an attenuated, deayed, and possiby distorted version of e signa at was transmitted pus noise and (possiby) interference. The reationship between e received signa and e transmitted signa is Figure 1. NLOS channe (0-4m) Impuse response

4 Figure. NLOS channe (0-4m) Excess deay Figure 5. NLOS channe (0-4m) Average Power Decay Profie Figure 3. NLOS channe (0-4m) RMS deay Figure 6. NLOS channe (4-10m) Impuse response Figure 4. NLOS channe (0-4m) Number of significant pa wiin 10 db peak Figure 7. NLOS channe (4-10m) Excess deay

5 Figure 8. NLOS channe (4-10m) RMS deay Figure 9. NLOS channe (4-10m) Number of significant pa wiin 10 db peak Figure 10. NLOS channe (4-10m) Average Power Decay Profie For e actua comparison of proposas wiin IEEE a, 100 impuse responses are generated for each of e two mode environments. The CM1 scenario is defined for e 0-4m range, wi an nlos antenna configuration. The CM scenario is defined for a nlos antenna configuration and a greater transmission distance, i.e., 4 to 10 meters. Figure 1 and Figure 6 shows e custering of e mutipa arrivas is evidence observed. This vaidates e mutipas arriving in custers of UWB channe measurement data. In CM1 first strong mutipa component deayed by 5ns. Whie in CM first component deayed more an strong mutipa component of CM1 due to more refections in e way of mutipa components in CM. The custer and ray arriva rates of e NLOS channes are significanty very high because of scattering. This is consistent wi e tempora parameters from e measured data, which indicates e NLOS channes have many more significant MPCs. The average deay profie of CM shows at an increase in e distance between transmitters and receivers impies a reduction in e number of significant mutipa components, and a spreading of e CIR energy amongst a arger number of mutipa components compared to CM1. It shows at e power is decreasing exponentiay. The doube exponentia decay function means two exponentia decays, one for e custers and e oer for e rays. The excess deay and e RMS deay spread foow e norma distribution wi higher vaue of mean and variance for e case of our mode. IV. CONCLUSION The UWB channe mode was investigated. First, an overview e UWB propagation characteristics were discussed and en e most popuar channe mode for short-distance high-data rate UWB communications, i.e., e IEEE a channe mode, was presented. This channe can be modeed by two different scenarios according to e antenna configurations in nlos and e distance of transmission. and bo modes are compared. Using e definition of e channe mode, a eoretica meod was designed to obtain an equivaent ognorma RV, wi known mean and standard deviation, to any attenuation factor of its CIR. The resuts of is meod were compared against resuts obtained from simuations. They indicated at our meod is quite accurate if e custers of mutipa rays forming e channe CIR are disjointed. Simuated resuts show at e received UWB signa power decreases exponentiay foowing doube exponentia function. Initia anaysis and investigation of e data verified e exponentia mode and confirmed at our UWB channe does have a exponentia decay ampitude characteristics. The RMS deay spread, excess deay and MPCs foow norma distribution and ey have higher vaue of mean. ACKNOWLEDGEMENTS I am very ankfu to Dr. K. H. Wandra who has been my guide of M.E. dissertation he has aways encouraged me to do

6 new work. And I aso ank to my friend Asst. Prof. Gaurav joshi for his kind support. REFERENCES [1] Anuj Batra, Jaiganesh Baakrishnan, G. Roberto Aieo, Design of a Mutiband OFDM System for Reaistic UWB Channe Environments, /04$ IEEE. [] J. R. Foerster, S. Roy, S. Somayazuu, and D. Leeper, Utra wideband radio design: The promise of High-Speed, Short-Range Wireess Connectivity, Proceedings of The IEEE, Vo. 9, No., pp , Feb [3] M. Z. Win and R. A. Schotz, On e robustness of utra-wide bandwid signas in dense mutipa environments, IEEE Communications Letters, Vo., pp , Feb [4] IEEE a, Channe modeing sub-committee fina report, IEEE P /490r1-SG3a, Feb. 003, Date accessed Nov [5] A. A. Saeh and R. A Vaenzuea, A statistica mode for indoor mutipa propagation,ieee Journa on Seected Areas in Communications, Vo. 5, pp , [6] J. R. Foerster, The Effects of Mutipa Interference on e Performance of UWB Systems in an Indoor Wireess Channe, IEEE VTS 53rd, Vo., pp. [7] H. Hashemi, Impuse Response Modeing of Indoor Radio Propagation Channes, IEEE Journa on Seected Areas in Communications, Vo. 11, No. 7, pp , Sept [8] J. Foerster and et a., Channe modeing sub-committee report (fina), IEEE P80.15Wireess Persona Area Networks, Tech. Rep. P /490r1-SG3a, Feb [9] A. A. M. Saeh and R. A. Vaenzuea, A statistica mode for indoor mutipa propagation, IEEE J. Seect. Areas Commun., vo. 5, no., pp , Feb [10] Satis Kaza, Thesis, performance anaysis of utra-wideband transmitted reference system and enhancement techniques, Dec-004.