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1 Ctaton: Nguyen, H. Q., Cho, Joon-Ho, Kang, Moonsoo, Ghassemlooy, Zabh, Km, D. H., Lm, S., Kang, T. an Lee, Chung Ghu (010) A MATLAB base smulaton program for noor vsble lght ommunaton system. In: 7th Internatonal Symposum on Communaton Systems Networks an Dgtal Sgnal proessng (CSNDS), 1-3 July 010, Northumbra Unversty, Newastle upon Tyne. URL: < Ths verson was ownloae from Northumbra Researh Lnk: Northumbra Unversty has evelope Northumbra Researh Lnk (NRL) to enable users to aess the Unversty s researh output. Copyrght an moral rghts for tems on NRL are retane by the nvual author(s) an/or other opyrght owners. Sngle opes of full tems an be reproue, splaye or performe, an gven to thr partes n any format or meum for personal researh or stuy, euatonal, or not-for-proft purposes wthout pror permsson or harge, prove the authors, ttle an full bblograph etals are gven, as well as a hyperlnk an/or URL to the orgnal metaata page. The ontent must not be hange n any way. Full tems must not be sol ommerally n any format or meum wthout formal permsson of the opyrght holer. The full poly s avalable onlne: Ths oument may ffer from the fnal, publshe verson of the researh an has been mae avalable onlne n aorane wth publsher poles. To rea an/or te from the publshe verson of the researh, please vst the publsher s webste (a subsrpton may be requre.)

2 A MATLAB-base smulaton program for noor vsble lght ommunaton system H.Q. Nguyen 1, J.-H. Cho 1, M. Kang, Z. Ghassemlooy 3, D. H. Km 4, S.-K. Lm 4, T.-G. Kang 4, an C. G. Lee 1,* 1 Department of Eletron Engneerng, Chosun Unversty, South Korea Shool of Computer Engneerng, Chosun Unversty, South Korea 3 Shool of Computng, Engneerng an Informaton Senes. Northumbra Unversty, Unte Kngom 4 LED Communaton Researh Team, ETRI, South Korea *E-mal: lee@hosun.a.kr Abstrat We report a smulaton program for noor vsble lght ommunaton envronment base on MATLAB an Smulnk. The program onsers the postons of the transmtters an the refletons at eah wall. For vsble lght ommunaton envronment, the llumnaton lght-emttng oe s use not only as a lghtng eve, but also as a ommunaton eve. Usng the smulaton program, the strbutons of llumnane an root-mean-square elay sprea are analyze at bottom surfae. I. INTRODUCTION Due to fast-growng eman of hgh-spee ata transport an moblty, wreless ommunaton s very mportant tehnology n our lves. Reently, the noor wreless ommunaton tehnology usng lght-emttng oes (LEDs) s a new researh fel [1-3]. Usng LEDs, there are a lot of avantages n vewponts of lghtng an wreless ommunaton: The lghtng equpment wth LEDs s easy to nstall, ne lookng an safe for human eye. The LED lghtng an be equppe wth varous shapes whh were ffult wth tratonal lghtngs suh as nanesent bulbs an fluoresent lamps. The low ost, low eletr power onsumpton an long lfe expetany are the onserable avantages. The possblty of hgh-spee ata ommunaton s the nspensable haraterst for usng LED nfrastruture for lghtng as ommunaton eves. From these avantages, t s expete that the noor optal wreless ommunaton usng LEDs wll be use wely n the near future. The funamental physal haratersts an problems of wreless ommunaton usng LEDs are stue an researhe by many labs, for example, mpulse response [3,4], optal power strbuton [5,6], bt error rato (BER), sgnal-to-nose rato (SNR), an shaowng [8], refleton [9], feasblty of ommunaton lnk [10-1], the way to enhane ate rate [13,14], moelng a luster of LEDs as a retonal pont soure aorng to the LED raaton pattern, arrangement of LEDs, an the number of LEDs, the far-fel onton an the prese optal moel of LED raaton have been reporte n [15]. In ths paper, we report a smulaton program evelope base on MATLAB an Smulnk whh alulates the llumnaton strbuton, RMS elay sprea, an reeve sgnal waveform onserng the postons of the transmtters an the refletons on walls. Ths paper s organze as follows. In Seton II, the moelng of physal struture s esrbe. Seton III esrbes the llumnane performane an Seton IV esrbes the root mean square (RMS) elay sprea for our system moel. Fnally, our onluson s gven n the seton V. II. MODELING OF OTICAL CHANEL We assume the physal parameters for evelopng the snmulaton program. The sze of the offe room sze s 5m x 5m x 3m an the LEDs are nstalle on the elng; the heght of esk s 0.85 m an the reever s plae on the workng plane (the bottom surfae n the room moel shown n Fg. 1). The other smulaton parameters are lste n Table 1. TABLE I. SIMULATION ARAMETERS. Sem-angle at half power 30 [eg] Center lumnous ntensty 0.73 [] Number of LED eah group 3600 (60x60) Fel of vew 50 [eg] Refleton oeffent 0.8 Fg. 1. Inoor vsble lght ommunaton envronment. The strbuton of llumnane at a workng plane s susse. It s assume that the soure of emsson an

3 the reflete ponts on wall have a Lambertan raaton pattern [1, 6, 7]. The lambertan emsson means that the lght ntensty emtte from the soure has a osne epenene on the angle of emsson wth respet to the surfae normal. Followng the funton for an optal lnk [1, 5-10], the lumnous ntensty n angle s gven by: shows the strbuton for 4 transmtters wth the semangle of 30 egree. The performane of LEDs wth narrow fel of vew s shown n here. It opens a hane for mprovement LEDs wth the we fel for llumnane. The value s n the range from 6.80 to lx. The average value s lx. m I ( ) I(0) os ( ) (1) Where I(0) s the enter lumnous ntensty of the group LEDs, s the angle of rraane, m s the orer of Lambertan emsson an s gven by the sem-angle at half llumnane of the LED 1/ as: m ln / ln(os ) () 1/ A horzontal llumnane E hor at a pont (x,y,z) on the workng plane s gven by : m I(0) os ( ) E hor ( x, y, z) (3) D os( ) Fg. 3. Dstrbuton of llumnane n ase of one transmtter. Maxmum value= lx. Where D s the stane between transmtter an reever, s the angle of nene. To survey the llumnane strbuton of LEDs system, we assume two onfguratons for LED poston on the elng. In ase of one transmtter, the poston s the enter of the elng, an for four transmtters the transmtters are loate at the poston lke Fg.. Fg. 4. Illumnane strbuton nase of 4 transmtters wth the LED semangle of 30 egree. Max= lx; Mn= 6.80 lx; Avarage= lx. Fg.. The poston of transmtters on the elng. We use MATLAB007R program to evelop the smulaton program. Frst, the program alulates the ret llumnaton, an the reflete llumnaton for one or plural transmtters wth Lambertan raaton pattern (the results are gven by many prevous researhes [6, 7]). Also, the program alulates the RMS elay sprea for ths effet. III. ILLUMINANCE ERFORMANCE The strbuton of llumnane of our system s shown n fgure below: Fg. 3 shows the llumnane wth 1 transmtter, the semangle at half power s 30 egree. The maxmum value of lumnous flux n the enter s lx. Fg. 4 below

4 Fg. 5. Dstrbuton of llumnane wth 4 transmtters wth the LED semangle of 70 egree. Max= lx; Mn= lx; Average= lx. Fg. 5 s gven for omparng our stuy wth prevous researhes [6, 7]; the numeral alulaton n llumnane strbuton of our system at the semangle of 70 egree s shown n here. All of parameters are same. Aorng to the stanarze by Internatonal Organzaton for Stanarzaton (ISO), the llumnane of ths system s from 300 to 1500 (lx), t s suffent for offe work. In our ase, we assume that the refletons at the reflete pont have Lambertan patterns. After alulaton (nlung reton, refleton wth Lambertan pattern) an omparng wth the llumnane wthout Lambertan pattern at reflete ponts, the value s larger than 10.8 % (n the same ontons) n ase of four transmtters. IV. ROOT MEAN SQUARE DELAY SREAD The term of RMS elay sprea s the stanar evaton (or root-mean-square) value of the elay of refletons. Conserng both the ret path an the frst orer reflete path, the reeve optal power at a pont an be alulate by vng the refleton walls nto ponts of refletons as follows: LEDs refletons r t H ( 0) t H ref (0) (4) t s the optal power transmtte from an LED, H (0) s the hannel DC gan on rete paths, whh s gven n [5-9] as ( m1) A m os ( ) T ( ) ( )os( ), 0 s g H (0) D 0 (5) Ts ( ) s the gan of an optal flter, an g( ) s the gan of optal onentrator. s the angle of nene. enotes the wth of a fel of vson at a reever. The optal onentrator g( ) an be gven as n g( ) sn ( ) 0 0 n enotes the refratve nex. H ref (0) s the hannel DC gan on refleton ponts [5-9] an s gven as: (6) ( m 1) A m os ( )os( )... A wall D1 D Href (0) os( ) Ts ( ) g( ) os( ), 0 0 (7) Where D 1 s the stane between an LED an a refletve pont, D s the stane between a refletve pont an a reever, s the refletane fator, A s a wall refletve area of small regon, s the angle of nene to a refletve pont, s the angle of rraane to the reever. Wth M ret paths from transmtters to a spef reever an N refleton paths to the same reever, the total power of the reeve optal sgnals s alulate as Where, lght at the th pont an M N T r, j j, (8) s the reeve optal power of a ret r, j means the reeve optal power of a reflete lght at the j th pont. M enotes the number of omponents for ret lght an N enotes the number of omponents for reflete lght. The RMS elay sprea proves an estmate for a kn of normalze elay tme ue to multple refletons. Therefore, the RMS elay sprea wll be a rtal performane rteron for the upper boun of the ata transmsson rate. The mean exess elay s efne [16] to be M N t r jt r j. (9),,,, T j t, s the propagaton tme for the th ret lght, t an r, j,. r j s the propagaton tme of the j th reflete lght The RMS elay sprea where RMS RMS s gven by: ( ), (10) M N t r jt r j. (11),,,, T j It s note that the RMS elay sprea epens on the relatve levels of optal power omponents wthn T. Fg. 6 shows the strbuton of RMS for one transmtter. The maxmum value s 3. ns (nanoseon), the mnmum s 0.86 ps. Fg. 7 shows the strbuton of

5 RMS for one transmtter. The maxmum value s 3.57 ns the mnmum s 0.17 ns. It s aepte that the maxmum bt rate that an be transmtte through the hannel wthout neeng an equalzer wll be lmte as follows [11, 16] Rb 1/(10 RMS ). (1) Therefore, t s estmate that the maxmum ata rate from Eq. (9) wll be lmte to 8 Mb/s onserng whole bottom surfae. TABLE II. SAMLE OINTS, FOLLOWING THE CUTTING LANE (.5, Y, Z) ON THE CARTESIAN S COORDINATE. pont Co-ornate 1 (.5,0.5) (.5,1.0) 3 (.5,1.5) 4 (.5,.0) 5(entre) (.5,.5) 6 (.5,3.0) 7 (.5,3.5) 8 (.5,4.0) 9 (.5,4.5) Fg. 8. RMS elay sprea at several sample reever postons. Fg. 6. Dstrbuton of RMS elay sprea for one transmtter. The poston of the transmtter s (.5,.5) wth the LED semangle of 30 egree. Fg.7. Dstrbuton of RMS elay sprea for four transmtters. The postons of the transmtters are (1.5, 1.5), (1.5, 3.75), (3.75, 1.5), (3.75, 3.75) wth the LED semangle of 30 egree. Fg. 8 shows the RMS elay sprea performane at some sample ponts. The RMS elay sprea of system at some spef ponts n ase 4 transmtters usually larger than the value n ase 1 transmtter. The man reason s the multpaths of lght for four transmtters. Fg. 9. Waveforms from the smulaton usng MATLAB/Smulnk. The transmtte sgnal s n the NRZ-OOK moulaton format. The bt rate s set to be 0Mbps. Fg. 9 shows the smulaton for NRZ-OOK moulaton format usng MATLAB/Smulnk. The nose omponents from ambent lght soures are mplemente base on the

6 measurements n [17]. The waveform alulaton onserng refletons wth Lambertan pattern at the refleton ponts are splaye. The smulaton program nees to be upgrae by mplementng the varous physal parameters nlung the sze of atve area, the responsvty, the nose omponents n the photoetetors, the asymmetr refletons on walls, an varous avane moulaton formats. V. CONCLUSION In ths paper, we have reporte the smulaton program for noor vsble lght ommunaton envronment base on MATLAB an Smulnk. The program onsere frst-orer refletons at eah wall. Usng the smulaton program, the strbutons of llumnane an RMS elay sprea were analyze at bottom surfae. Also, the waveforms for NRZ-OOK have been emonstrate. It s expete to be upgrae wth more realst physal parameters an varous avane moulaton formats. [1] C. G. Lee, C. S. ark, J.-H. Km, an D.-H. Km, Expermental verfaton of optal wreless ommunaton lnk usng hghbrghtness llumnaton lght-emttng oes, Opt. Eng. 46, (007). [13] D. C. O'Bren, Hgh-spee ntegrate transevers for optal wreless, IEEE Commun. Mag. 41, 58-6 (003). [14] H. L. Mnh, D. C. O Bren, G. Faulkner, L. Zeng, K. Lee, D. Jung, Y. Oh, Hgh-Spee Vsble Lght Communatons Usng Multple-Resonant Equalzaton, IEEE hoton. Tehnol. Lett. 0, (008). [15] I. Moreno, C.-C. Sun, R. Ivanov, Far-fel onton for lghtemttng oe arrays, Appl. Opt.. 48, (009). [16] T. S. Rappaport, Wreless Communatons (rente-hall, 00). [17] A.J.C. Morera, R.T.Valaas, A.M. e Olvera Duarte, Optal nterferene proue by artfal lght, Wreless Net., vol. 3, pp , ACKNOWLEDGEMENT Ths work was supporte by the IT R&D program of MKE/KEIT [KI001930, Researh of nanometer vsble lght RGB wreless ommunatons for IT llumnaton ommunaton fuson]. REFERENCES [1] J. M. Kahn an J. R. Barry, Wreless Infrare Communatons, ro. IEEE 85 (), (1997). [] D. O'Bren an M. Katz, "Optal wreless ommunatons wthn fourth-generaton wreless systems," J. Opt. Network 4, 31-3 (005). [3] M. Kavehra an S. Jvkova, Inoor broaban optal wreless ommunatons: optal subsystems esgns an ther mpat on hannel haratersts, IEEE Wreless Commun. 10, (003). [4] J. B. Carruthers, S. M. Carroll, Statstal mpulse response moels for noor optal wreless hannels, Int. J. Commun. Syst. 18, (005). [5] A. Svabalan an J. John, "Improve power strbuton n ffuse Inoor Optal Wreless systems employng multple transmtter onfguratons," Opt. Quantum Eletron. 38, (006). [6] T. Komne, M. Nakagawa Funamental Analyss for Vsble Lght ommunaton system usng LED lght, IEEE Trans. Consum. Eletron. 50, (004). [7] T. Komne an M. Nakagawa, erformane evaluaton of Vsble- Lght Wreless Communaton System usng Whte LED Lghtng, n roeengs of the Nnth IEEE Symposum on Computers an Communatons, pp (004). [8] T. Komne, S. Haruyama an M. Nakagawa, A Stuy of Shaowng on Inoor Vsble-Lght Wreless Communaton Utlzng lural Whte LED Lghtngs, Wreless ers. Commun. 34, 11-5 (005). [9] K. Fan, T. Komne, Y. Tanaka, M. Nakagawa, The Effet of Refleton on Inoor Vsble-Lght Communaton System utlzng Whte LEDs, n roeengs of the 5 th Int. Symposum on Wreless ersonal Multmea Communatons (WMC00), pp (00). [10] T. Komne an M. Nakagawa, Integrate system of whte LED vsble lght ommunaton an power-lne ommunaton, IEEE Trans. Consum. Eletron. 49, (003). [11] Y. Tanaka, T. Komne, S. Haruyama an M. Nakagawa, Inoor Vsble Lght Data Transmsson System Utlzng Whte LED Lghts, IEICE Trans. Commun. E86-B, (003).