Performance Evaluation of Maximum Ratio combining Scheme in WCDMA System for Different Modulations

Transcription

1 Intenational Jounal of Emeging Technologies in Engineeing Reseach (IJETER) Volume 4, Issue 5, ay (6) efomance Evaluation of aimum Ratio combining Scheme in WCDA System fo Diffeent odulations Rajkuma Gupta Assistant ofesso, Amity Univesity, Rajasthan, India. Abstact In this pape analyze the pefomance of single input single output antenna system (SISO) and single input multiple outputs antenna system (SIO) using maimum atio combining(rc) divesity technique with binay phase shift keying (BSK) and quadatue phase shift keying (QSK) modulation schemes in wide band code division multiple access (WCDA) system. The pefomance analysis esults showed that SIO system give bette pefomance compae to SISO system in vaious netwok conditions. Inde Tems WCDA, Antenna divesity, SISO, SIO, aimum atio combining (RC).. ITRODUCTIO Wieless communication is the fastest gowth peiod in the histoy of communication technologies. The 3d geneation patneship poject (3G) and 3d geneation patneship poject two (3G) had developed the wideband codedivision multiple access (WCDA) technologies and CDA espectively []. WCDA is consideed to be wideband technologies based on the diect sequence spead spectum tansmission scheme, whee use infomation bits ae spead ove a wide bandwidth by multiplying the use data with quasi-andom bits called chips deived fom CDA speading codes. In ode to suppot vey high bit ates (upto bps), the use of a vaiable speading facto and multicode connection is suppoted. The chip ate 3.84 cps leads a caie bandwidth of 5Hz []. When a is tansmitted fom souce to destination though the channel, thee ae some factos which degade the pefomance of and these degadation factos ae path loss, noise, fading and intefeence. One of the most poweful techniques to mitigate the effects of fading is to use divesity combining of independently fading paths. The concept behind divesity is: if one path undegoes a deep fade at a paticula point of time, anothe independent path may have a stong [3]. Hee eceive is povided with multiple copies of the same infomation which ae tansmitted ove two o moe eal o vitual communication channels. The wok in this pape evaluates the pefomance of WCDA system using divesity scheme with vaious modulations in pesence of vaying netwok conditions. The net section pesents the bief eview of the elated wok.. The section 3 pesents the methodology adopted to simulate the system. The maimum atio combining (RC) divesity scheme is pesented in Section 4. The simulation esults and discussion is pesented in the Section 5. The last section concludes the pape and pesents the futue wok.. RELATED WORK asud. et.al[4] analyzed BER fo WCDA using 6-QA and QSK modulation techniques and studied the pefomance of W-CDA system with QSK and 6-QA modulation technique in diffeent channel such as AWG, line of sight (LOS), Rayleigh fading channel Hoyong.L et.al [5] poposed a hybid switched eamine combining (SEC) SEC/RC divesity scheme and studied BER ove ayleigh fading channel using BSK modulation technique. Tepedelenliog et al [6] analyzed pefomance of diffeent divesity combining techniques ove fading channels with impulsive noise. Thomas et.al [7] studied compaison of diffeent divesity combining techniques fo Rayleigh fading channels and studied that combining the two o thee lagest s (SC o SC3) offes significant impovement ove the pefomance of just selecting the lagest (SC). Alamouti et. al [8] poposed a new tansmit divesity scheme using two tansmit antennas and one eceive antenna, the new scheme povides the same divesity ode as maimal atio eceive combining (RRC) with one tansmit and two eceive antennas. Hemalatha et.al [9] analyzed divesity in CDA based boadband wieless system and found that the divesity CDA system with multiple antennas at the tansmitte and eceive esults in the impovement in SR and eduction in the multipath fading and intefeence. ISS: EveScience ublications 4

2 Intenational Jounal of Emeging Technologies in Engineeing Reseach (IJETER) Volume 4, Issue 5, ay (6) Infomation Speaded Convolution encode odulation (BSK & QSK) Raised cosine filte sequence Geneato Channel Divesity Scheme (RC) Eo counte Despeaded Vitebi decode Demodulation (BSK & QSK) Raised cosine filte BER Calculation Figue : Block diagam fo poposed WCDA system 3. OROSED ODELLIG The in WCDA system is degaded with vaious factos such as path loss, noise, fading and intefeence. The wok in the pesent pape analyzed the pefomance of the maimum atio combining (RC) divesity scheme in WCDA system to impove the quality. The simulated WCDA system is designed in atlab and the pefomance is analyzed fo vaious modulations unde vaying netwok conditions. The bit eo ate (BER) pefomance is evaluated with vaying conditions of to noise (E b/ o). The block diagam of the simulated WCDA system with poposed divesity scheme is pesented in Fig.. 4. ATEA DIVERSITY TECHIQUES The divesity scheme is the solution to impove the pefomance of system in fading envionment is to ensue that the infomation symbols pass though multiple paths, each of which fades independently, making sue that eliable communication is possible as long as one of the paths is stong and it can impove the pefomance ove fading channels. Antenna divesity can be obtained by placing multiple antennas at the tansmitte and/o the eceive []. Antenna divesity techniques use some combining methods such as selection combining, maimum atio combining, and equal gain combining. The divesity schemes fo single input single output (SISO) and single input multiple outputs (SIO) ae pesented in Fig. and Fig AXIU RATIO COBIIG In maimum atio combining (RC) divesity scheme, all the banches ae used simultaneously. Each of the banch s is weighted with a gain facto which is popotional to its own SR. Afte that, co-phasing and summing is done fo adding up the weighted banch s in phase []. Fig.4 shows the configuation fo a two-banch divesity system. Both the banches ae weighted by thei espective -to-noise atios and the banches ae then co-phased pio to summing in ode to insue that all banches ae added in phase fo maimum divesity gain. The summed s ae then used as the eceived and connected to the demodulato []. In a Rayleigh fading channel RC pefomance is best followed by equal gain combining and then selection divesity. The pefomance of RC is the same as that of equal gain combining (EGC) if s fom each path ae of equal stength. T R Fig. Single Input Single Output Antenna System (SISO) ISS: EveScience ublications 4

3 Intenational Jounal of Emeging Technologies in Engineeing Reseach (IJETER) Volume 4, Issue 5, ay (6) Fig.3 Single Input ultiple Outputs Antenna System (SIO) SR SR T Fig.4 Block diagam of a two-banch maimal atio combine fo equal noise powes in both banches The inputs to the maimal atio combine (Fig.4) ae both ayleigh distibuted s (with envelopes and ) with additive independent noise voltage souces n and n. n and n ae zeo mean white gaussian andom vaiables with a vaiance of ; the input voltage -to-noise atios ae SR Signal cophasing,, SRV SR,,, The SR afte maimal atio combining (RC) equies the evaluation of the instantaneous powe and noise powe. The amplitude of the of inteest afte RC at a given time t, V S, t, can be evaluated by multiplying the eceived envelope and, at t, by thei instantaneous voltage to noise powe atios which when summed gives. R Demodu lato () () V S, t t t t t t t t t,, S t VS t V The noise component afte RC at t,, t, is also multiplied by the gains in both banches and evaluates afte co-phasing and banch addition to t n t t n t n t n V, The noise powe is given by,, t n n f n dn E (3) (4) (5) n t nn t t n t V t E, t n E t n n t t n t E E The middle tem evaluates to zeo since each noise souce is independent of all othe s and has a mean of zeo.,, SR t t SR n E t n E t t t t t t t E n owe owe t Signal oise t S,, E n t t V E V t S,, t t t ISS: EveScience ublications 4

4 Intenational Jounal of Emeging Technologies in Engineeing Reseach (IJETER) Volume 4, Issue 5, ay (6) SR V GC Output t SR SR t db SR SR t t t t (6) (7) The BER v/s Eb/o elationship fo the WCDA system with nr=, is shown in figue 6 with QSK modulation scheme and with convolution encoding using RC technique. As can be seen fom gaph, in case of nr=, initially the BER can be obtained aound.4938 and at highe value of Eb/o, the achievable BER deceases aound.4 fo db Eb/o. In case of nr=, initially the BER can be obtained aound.444 and at highe value of Eb/o, the achievable BER deceases aound. fo 4 db Eb/o. SR V (8) 5. RESULTS AD DISCUSSIOS The pefomance of WCDA system is analyzed fo the maimum ation combining divesity scheme with two antennas (nr and nr) at the eceive. The BER v/s Eb/o elationship fo the WCDA system with nr=, is shown in Fig. 5 with QSK modulation scheme using RC technique. As can be seen fom gaph, in case of nr=, initially the BER can be obtained aound.898 and at highe value of Eb/o, the achievable BER deceases aound.94 fo 9 db Eb/o. In case of nr=, initially the BER can be obtained aound.389 and at highe value of Eb/o, the achievable BER deceases aound. fo 9 db Eb/o. Fig.6 BER fo QSK with convolution encoding using RC The BER v/s Eb/o elationship fo the WCDA system with nr=, is shown in figue 7 with BSK modulation scheme using RC technique. In case of nr=, initially the BER can be obtained aound.3 and at highe value of Eb/o, the achievable BER deceases aound.35 fo db Eb/o. In case of nr=, initially the BER can be obtained aound.694 and at highe value of Eb/o, the achievable BER deceases aound. fo 5 db Eb/o. Fig.5 BER fo QSK using RC Fig.7 BER fo BSK using RC ISS: EveScience ublications 43

5 Intenational Jounal of Emeging Technologies in Engineeing Reseach (IJETER) Volume 4, Issue 5, ay (6) [7] Eng.T; Kong. et.al; Compaison of divesity combining techniques fo Rayleigh fading channels, IEEE Tansactions on communication vol. 44, no. 9, sep.996. [8] Alamouti S.., A Simple Tansmit Divesity Technique fo Wieless communications, IEEE jounal on select aeas in communications, Vol. 6, no. 8,998 pp ,. [9] Hemalata. et.al, Divesity analysis in CDA based boadband wieless system, Reseach Jounal of Applied Sciences, Engineeing and Technology 4(6): pp [] Sedani B.S;Kulkani G.R.; Implementation of quality based algoithm fo Wima simulation using SISO and IO techniques,global jounal of eseaches in engineeing,vol.,no.4, pp. 6-. [] Zhou h. and Okamoto k., Compaison of code combining and RC divesity eception in mobile communications, IEEE Wieless Communications and etwoking Confeence, 4, Atlanta, USA,Vol.,4 pp 98-93,. [] Godon S.L., inciple of mobile communication, Kluwe academic, boston, 996. Autho Fig.8 BER fo BSK with convolution encoding using RC The BER v/s Eb/o elationship fo the WCDA system with nr=, is shown in figue 8 with BSK modulation scheme and with convolution encoding using RC technique. As can be seen fom gaph, in case of nr=, initially the BER can be obtained aound.4869 and at highe value of Eb/o, the achievable BER deceases aound.9 fo db Eb/o. In case of nr=, initially the BER can be obtained aound.44 and at highe value of Eb/o, the achievable BER deceases aound. fo 9 db Eb/o. 6. COCLUSIO In this pape, we analyzed the BER pefomance fo SISO and SIO using RC with diffeent modulation techniques. Hence SIO give bette pefomance compae to SISO. Results with BSK modulation technique ae bette compae to QSK fo SISO and SIO. In futue wok the same analysis will be caied out fo IO system and implement on FGA vete po II. REFERECES [] Olavaieta L.D., Wieless communications education: A Guide to Impotant Topics, icowave Review, ovembe, 5. [] asad R. and Ojanpea T., An oveview of CDA evolution towads wideband CDA, IEEE communication suvey, Vol., fouth quate 998,pp.-9 [3] oakis J.G.: Digital Communications, cgaw-hill, 995. [4] asud..a; Samsuzzaman.; Rahman..A; Bit Eo Rate efomance Analysis on odulation Techniques of Wideband Code Division ultiple Access, jounal of telecommunications,vol.,no.,mach. [5] Lee.H; ak.s.k; Song.Y; efomance analysis of a hybid SEC/RC divesity scheme ove Rayleigh fading, Advanced Communication Technology (ICACT), 3th Intenational Confeence on, vol., no., 3-6 Feb. pp.5-8 [6] Tepedelenlioglu.C; Gao.; On divesity eception ove fading channels with impulsive noise, IEEE Tansactions on vechicula technology, vol. 54, O. 6, nov. 5. Rajkuma gupta eceived degee of.tech fom ITJalandha in. He is enthusiastic to wok in the field of communication and VLSI. His aea of inteest includes wieless communication and analog and digital system designs using CAD tools and Low powe VLSI domain in addition to analog and mied cicuit design. ISS: EveScience ublications 44