Montecarlo Simulation Applied to Measurement of the Impact of the Smart Antenna Technology in Digital Cellular Systems

Transcription

1 Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl-juno 2015: ISSN FI-UNAM (artículo arbtrado) do: Montecarlo Smulaton Appled to Measurement of the Impact of the Smart Antenna Technology n Dgtal Cellular Systems Smulacón montecarlo aplcada a la medcón del mpacto de la tecnología de antenas ntelgentes en sstemas celulares dgtales Castañeda-Camacho Josefna E-mal: jcastane@ece.buap.mx Mno-Agular Gerardo E-mal: gmno44@eee.org Cortez Llana E-mal: lcortez@ece.buap.mx Gutérrez-Aras José Elgo Mosés E-mal: jmguterrez@ece.buap.mx Guerrero-Castellanos José Ferm E-mal: fguerrero@ece.buap.mx Muñóz-Hernández Germán Ardul E-mal: gmunoz64@yahoo.co.uk Informaton on the artcle: receved: October 2013, reevaluated: January 2014, accepted: May 2014 Abstract The smart antenna technology has receved ncreasng nterest due to ts capablty for mprovng the performance of wreless rado systems. In ths work, we studed the throughput maxmzaton n a dgtal cellular system when a smart antenna array s mplemented. We focus, n the study of the downlnk of a 3G cellular system and consder a packet data drect-sequence code dvson, multple access (DS-CDMA). Our methodology s based on the Montecarlo smulaton technque, and t s used to show that t s possble to obtan a beam smart antenna array. From our results we conclude that t s feasble to consder the applcaton of ths technology n 4G envronments. Keywords:

2 Montecarlo Smulaton Appled to Measurement of the Impact of the Smart Antenna Technology n Dgtal Cellular Systems Resumen La tecnología de antenas ntelgentes ha sdo de gran nterés debdo a su capacdad para mejorar el desempeño de los sstemas nalámbrcos. En este trabajo, estudamos la mejora del desempeño en el sstema dgtal celular cuando se utlza un arreglo de antenas ntelgentes. Nos enfocamos además, en el estudo del enlace de bajada de un sstema celular 3G y consderamos un esquema de acceso múltple de paquetes de datos de secuenca drecta (DS-CDMA). Nuestra metodología está basada en la técnca de smulacón Montecarlo y se usa para mostrar que es posble obtener un n- ntelgentes. De nuestros resultados conclumos que es posble consderar la aplcacón de esta tecnología en ambentes 4G. Descrptores: antenas Intelgentes smulacón Montecarlo sstema celular dgtal Introducton The adopton of smart antenna technques n future w- the cost of establshng new wreless networks, the optmzaton of servce qualty, and realzaton of transparent operaton across wreless networks. Adaptve antennas have been used for decades n areas such as radars, satellte communcatons, remote sensng, and tons s assocated wth ts own unque set of challenges, such as the channel n whch the system operates, the propagaton envronment, sources of nterference, and nose or jammng. In addton, the end goal for of the type of array, sze, adaptve algorthms, and ntegraton wth other system components (Alexou and Haardt, 2004; Lbert and Rapaport, 1999). Current moble communcatons systems employ sectorzaton to reduce nterference and ncrease capacty. Cells are broken nto three or sx sectors, wth dedcated antennas and RF paths. Increasng the amount of sectorzaton reduces the nterference seen by the desred sgnal. One drawback of current sectorzaton - overlap. Furthermore, ncreasng the number of sec- communcatons systems, through the use of narrow beams drected toward clusters of users, whle at the same tme steerng nulls toward nterferng users. Wth a narrow-beam drected toward a desred user, some nterferers that would have seen n the 120 sector antenna, wll be outsde of the beam-wdth of the array (Herscovc, 2001). dard n a real system remans very unlkely because t would requre an unloaded system servng a sngle user to be extremely close to the base staton. Ths leads to two questons: Why the ncreased nterest n the smart antennas?, and how are they beng consdered as a vable technology for applcatons such as moble telecommuncatons? As we know, operators are faced wth ncreasng capacty demands for both voce and hgher data rates and double voce capacty compared wth ther 2G counterparts, ther actual performance s stll susceptble to nterference, and adverse channel condtons created by multpath propagaton and system loadng. As such, smart antennas technques can complement 3G system and mprove ther performance by allevatng and reducng the degradaton caused by the aforementoned factors. In fact, because of ther na- ment n the SIR experenced by the users would drectly well as ncreased sector throughput that can support hgher capactes (Lbert and Rapaport, 1999; Herscovc, 2001; Bender et al., 2000) A new generaton of moble et al., 2006). Smart antennas technques can complement the new generaton systems by mprovng ther performance. the throughput of the data network or the maxmum achevable data transmsson rate; n a sense that any mprovement n the SIR experenced by the users vdual users as well as ncreased sector throughput that can support hgher capactes (Herscovc, 2001; Bender et al., 2000). 208 Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl juno 2015: ISSN FI-UNAM

3 Castañeda-Camacho Josefna, Mno-Agular Gerardo, Cortez Llana, Gutérrez-Aras José Elgo Mosés, Guerrero-Castellanos José Ferm, Muñóz-Hernández Germán Ardul We evaluate the throughput n the forward lnk of a The base statons are located n the center poston and the use of three sectored antennas s assumed. The moble users are unformly dstrbuted wthn the cells. The performance of the system has been measured n terms of a Monte Carlo smulaton mplemented n MATLAB. The Monte Carlo smulaton methodology s a type of smulaton that reles on repeated random samplng and statstcal analyss to compute the results method of smulaton s very closely related to random s not known n advance. In ths context, Monte Carlo smulaton can be consdered as a methodcal way of dong so-called what-f analyss where we use mathematcal models to descrbe the nteractons n a system usng mathematcal expressons. These models typcally depend on a number of nput parameters, whch when processed through the mathematcal formulas n the model, results n one or more outputs. Ths work s organzed as follows. In the next secton, we present the operaton of the CDMA2000 tem. The numercal results are presented n the fourth secton. The last secton provdes our conclusons and remarks. CDMA2000 1xEV-DO System transmsson speed whch an ndvdual user may ex- user experence). Data throughput on the other hand, s a far more mportant metrc for performance. Thus, the user throughput s the average data rate a user may ex- Rapaport, 1999). The CDMA2000 famly of standards s a wdeband spread spectrum rado nterface that uses CDMA technology to meet the objectves of 3G systems whle systems. Ths means that moble handsets desgned ac- of the CDMA2000 standard s called 1x rado transmsson technology (1xRTT) because t uses an RF carrer of also referred to as spreadng rate (SR) 1. The key bene- - and multmeda servces and mproved data servces support (Lbert and Rapaport, 1999). The current 3G operators n Japan and Korea as well as n the Unted States are already experencng great s optmzed for wreless hgh speed packet data serv- et al., 2003; Wonsuk et al., 2001);. Because of the typcal asymmetrc crtcal of the two lnks (Bender et alet al., 2003). Thus several technques were ntroduced n dvson-multplexed (TDM) waveform, power control and a varety of modulaton schemes, ncludng QPSK, 8 PSK and 16 QAM as well as codng rates that best monly called adaptve modulaton and codng techn- Forward Lnk Performance. son rate of user s R and the bandwdth s gven by W C, the energy to nterference rato requrement s gven by Eb WC SIR I (1) 0 R where SIR s the sgnal to nterference rato requrement. If we consder QPSK modulaton and the transmsson rate as a functon of the processng gan, the maxmum achevable transmsson rate for the user, tan, 2000). Technology Carrer Bandwdth (MHz) Downlnk Peak Data Rate(Kbps) Average User Throughput (Kbps) CDMA20001x CDMA2000 WCDMA HSDPA Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl-juno 2015: ISSN FI-UNAM 209

4 Montecarlo Smulaton Appled to Measurement of the Impact of the Smart Antenna Technology n Dgtal Cellular Systems WC SIR R 2W C SIR 2 SIR 2 terference rato s gven by (2) Numercal results A Monte Carlo smulaton of dscrete events was ca- evaluated the performance n terms of the throughput gven by the equaton (2), where the SIR s calculated n the scenaro proposed n Fgure 1. In addton we SIR NBS k1 G G 0, r 0, 0, k, r k, k, (3) where G( 0, ) s the antenna gan relatve to the -th user respect to the 0-th base staton, G( k, ) s the antenna gan relatve to the -th user wth respect to the k-th, 10 base staton 10 k r models the propagaton losses k, gven by the product of the -th power of the r k, dstan- the 0-th base staton and the k-th base staton, and a lognormal component whch represents the shadowng losses and whose characterstc Gaussan random va- k,, has zero mean and standard devaton. The, models the propagaton losses gven by the k j rkj, product of the -th power of the r k, j dstance between the j-th user and ts k-th power control base staton and a lognormal component whch represents the shadowng losses. N BS s the number of nterferng base statons. In the prevous equaton the antenna gan s approxmated by a parabolc functon n the man beam and by a constant average for the sde-lobe. Therefore, the antenna gan can be expressed as (Ramakrshna and 1q 2 1p 1 2 k, j k, j 1q Gk, j (4) 1p p k, j 1q where s the angle between the desred user and the drecton of the maxmum gan of the antenna, q represents the antenna gan level (normalzed to the max- sector crossover from the maxmum gan drecton and p represents the average normalzed gan level for the sde-lobe. The nomnal values chosen n our evaluatons for q and p were 4 cellular sector antenna wth 3-dB horzontal beam wdth around Start Desgn of cellular network wth sectorzed cells Random generaton of the unformly dstrbuted users Propagaton losses estmaton, consderng the μ-th power wth parameters μ = 4 and = 8dB, between the drecton of maxmum radaton of each antenna and the desred user n the 0-th cell Antenna gan estmaton, 1q k, j Gk, j p G k, j 1p k, j 1q 1p k, j 1q Where pq = 4dB SIR evaluaton Transmsson rate evaluaton W C SIR SIR 2 R 2W C SIR Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl juno 2015: ISSN FI-UNAM

5 Castañeda-Camacho Josefna, Mno-Agular Gerardo, Cortez Llana, Gutérrez-Aras José Elgo Mosés, Guerrero-Castellanos José Ferm, Muñóz-Hernández Germán Ardul 3.00E E+06 s] p [b 2.00E+06 te ra 1.50E+06 a ta d g e 1.00E+06 ra v e A 5.00E E+00 assumed that = 8dB, = 4, W C = MHz and the cell sze of 1 Km. In equaton (3) we are consderng that N BS nterferng cells as we can see n Fgure 1. The development of the Monte Carlo smulaton can Fnally, Fgure 3 shows the average data rate or maxmum achevable data transmsson rate of the values and, beam-wdth values. Compared wth the normal operaton, n whch the smart antennas, we can observe that the throughput ncreases as the beam wdth of the antenna array decreases. From the results, when we consder for example a proxmately equal to 100% n comparson wth the normal operaton. Concluson In ths paper we developed a Monte Carlo smulaton of dscrete events to prove that t s possble to obtan a tem due to the smart antenna array. Also, we can apply ths technology to 4G generaton systems to mprove ts mechansm to maxmze the throughput of a CDMA2000 smart antennas n a CDMA cellular system can provde a 100% of data rate ncrement compared wth the normal operaton of the system. We are also leavng the bass for the analyss of ths smart antenna technology n future wreless generatons. References Qualty of servce[db] Alexou A. and Haardt M. Smart antenna technologes for future wreless systems: Trends and Challenges. IEEE Communcatons Magazne Normal Operaton - less data servce for nomadc users. IEEE Communcatons Magazne lnk erlang capacty of multclass cdma cellular system consderng nondeal antenna sectorzaton. IEEE Transactons on Vehcular Technology of an overlad cdma and tdma systems wth cell coverage area restrcton. IEEE Transactons on Vehcular Technology, volume - Herscovc N. and Chrstodoulou C. Potentals of smart antennas n CDMA systems and uplnk mprovements. IEEE Antennas and Propagaton Magazne Lbert J.C. and Rapaport T.S. Smart antennas for wreless communcatons, Prentce Hall, Zhuang M. and Ln B. Performance analyss of receve antennas Internatonal Workshop on Ant-counterfetng, Securty and maxmzaton n a dual class CDMA system. IEEE Journal on Selected Areas n Communcaton, volume 16 (ssue 6), August 1998: Proceedngs of the 2008 Wnter Smulaton Conference, 2008, pp Sennor U. and Greenstan L.J. Throughput maxmzaton n CDMA uplnks usng adaptve spreadng and power control, - Sndhushayana N.T. and Black P.J. Forward lnk codng and mo- Symp. On Personal Indoor and Moble Rado Communcatons, volume 4, pp , September Sprng 2001, pp IEEE Communcatons Magazne rate wreless networks. IEEE Wreless Communcatons and Networkng - Wreless Personal Multmeda Communcatons, volume 2, Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl-juno 2015: ISSN FI-UNAM 211

6 Montecarlo Smulaton Appled to Measurement of the Impact of the Smart Antenna Technology n Dgtal Cellular Systems Ctaton for ths artcle: Chcago ctaton Ingenería Investgacón y Tecnología ISO 690 ctaton style Ingenería Investgacón y Tecnología About the authors Unversdad Autónoma de Puebla (BUAP) 1999, and M.Sc. and Ph.D. degrees n electrcal engneerng from Centro de - tem dmensonng, performance modelng and evaluaton of overlad systems, packet networks and dgtal systems. Gerardo Mno-Agular power electroncs at the Unversdad de las Amércas Puebla n 1999, and Ph.D. n electrcal machnes control at the Unverstat Poltècnca de Catalunya, Span, Currently head of the graduate department on electroncs engneerng master s program, and electroncs nstrumentaton at BUAP. Focused n dgtal systems, power electroncs, power qualty, power generaton, electrc drves and drvetran electrc vehcles. Cortez Llana the Polytechncal Insttute of Kev, Ukrane and a Ph.D n techncal scences at the Polytechncal State Unversty of Mexco. Focused n dgtal systems, power electroncs and power generaton. José Elgo Mosés Gutérrez-Aras matcal modelng and analyss of dynamc and dgtal systems. Currently he s researcher and professor at the Fa- José Ferm Guerrero-Castellanos. Born n Poza Rca, Méxco. Bachelor degree n electronc scence from BUAP, Méxco n 2002, and M.Sc and Ph.D n automatc control from Grenoble Insttute of Technology and Joseph Fourer Unversty, Grenoble, France, n 2004 and 2008, respectvely. Between January and June 2008, he was a Postdoctoral Researcher at GIPSALab Laboratory, Grenoble, France. Spent one year at the Unversty Polytechnc of Puebla, Mexco as an asss- Laboratory. Research nterests: modelng, estmaton and nonlnear control of cyber-physcal systems. Appled con- Germán Ardul Muñóz-Hernández - Currently at BUAP. Areas of nterest: dgtal systems, control systems applcatons and automaton. 212 Ingenería Investgacón y Tecnología, volumen XVI (número 2), abrl juno 2015: ISSN FI-UNAM