Analysis of SDR GNSS Using MATLAB

Transcription

1 Iteratioal Joural of Computer Techology ad Electroics Egieerig (IJCTEE) Volume 5, Issue 3, Jue 2015 Aalysis of SDR GNSS Usig MATLAB Abstract This paper explais a software defied radio global avigatio satellite system(sdr GNSS) usig MATLAB I the first istace, the existig performace of the system was aalyzed. Secodly, by varyig some vital parameters like atea diameter, oise temperature etc., the optimized result was foud with sigificat observatios. It also aalyses the mathematical model to provide clear visio of relatioship amog all compoets throughout the system. Keywords global avigatio satellite system (GNSS), software defied radio(sdr), PC(persoal computer), FPGA(field programmig gate array), DSP(digital sigal processig). BER(bit error rate) I. INTRODUCTION The cocept of software defied radio (SDR) ad recofigurable architectures developed back about twety years ago, with the work of J. Mitola s pioeerig effort[1], i 1999 special Joural issue o commuicatios[2] ad IEEE Persoal commuicatio magazie[3].sice that period SDR has gaied lots of attetio.hece it gradually developed more prototypig of ew architectures i low cost,short developmet time, ad far easier upgradability ad maitaiability as compared to hardware approaches. These aspects have made SDR extremely attractive i R&D which is cocetrated o wireless termials. Though the dedicated hardware is more accepted i the market volume, i some specific devices ad portable termials i which power cosumptio ad size matter, oetheless software defied radio techology popularity is still growig. Over last several years, the SDR GNSS has bee proposed; most of them are based o GNSS receiver architecture based o PC, FPGA, FPGA/DSP hybrid platforms. The part of efficiet data processig is ufocused till ow. The estimatio of efficiet performace of GNSS is equally ecessary as of its architectural part. This paper will itroduce the implemetatio of traditioal SDR global avigatio satellite system usig MATLAB as a Tool. I the first istace, the existig performace of the system was improved by reducig sigal oise ratio with varyig some parameters like atea diameter, oise temperature, I/Q imbalace factor etc. The optimized result was aalyzed with sigificat observatios. Secodly, the relatioship betwee bit error rate ad threshold of differet chael badwidths of the system were discussed ad plotted. Sagitarai Das 1, Dr. M. D. Kokate 2 K.K.W.I.E.E & R, Uiversity of Pue, Nashik, Idia 10 II. ARCHITECTURE OF SDR GNSS The traditioal software defied radio GNSS architecture is explaied i [4]. The implemeted SDR GNSS architecture is show below i the figure1. There are three major sectios such as trasmitter, dowlik path ad receiver [5]. The trasmitter sectio icludes blocks such as radom data geerator, rectagular QAM modulator, raised cosie trasmit filter, high power amplifier ad RF atea. The dowlik path sectio icludes dowlik path with free space path loss ad phase/frequecy offset block. The last but ot the least receiver sectio cotais blocks such as RF atea, system temperature, phase oise, I/Q imbalace, DC removal, magitude AGC, phase frequecy offset, raised cosie filter ad rectagular 16 QAM. There is also provisio of power spectrum estimatio, ed to ed costellatio, ad costellatio before agai after HPA, BER calculatios. Figure1- Implemeted Architecture of SDR GNSS The radom iteger geerator gives radom data stream, those are modulated by rectagular 16-QAM, the filtered by raised cosie trasmit filter, which up samples ad filters the iput sigal usig ormal or square root raised cosie FIR filter. The data stream is amplified usig Sahel model high power amplifier. Sahel model high power amplifier is used to add memory less oliearity to complex basebad sigal. The fially the stream of data is ready ad RF atea is used for trasmissio of same.

2 Iteratioal Joural of Computer Techology ad Electroics Egieerig (IJCTEE) Volume 5, Issue 3, Jue 2015 The dowlik data path has free space path loss about 196 db happes. It reduces the amplitude of the iput sigal by amout specified. Here it is possible to specify the loss directly usig distace ad frequecy mode. The reciprocal of the loss is applied as a gai. The sigal iherits its output data type from the iput sigal by phase/frequecy offset. Here the Doppler ad phase error will be determied. The sigal is received by RF atea at the receiver ed. Satellite receiver system adds receiver thermal oise to complex base bad sigal. Here the oise ca be i terms of oise temperature, oise figure or oise factor. here also the phase oise is added to complex basebad sigal. The phase oise is filtered accordig to the specified spectral mask. The I/Q imbalace creates complex basebad model of sigal impairmets caused by imbalaces betwee i phase ad quadrature receiver compoets. The sigal removes the DC offset ad compesate for the same i I/Q imbalace block. Automatic gai cotrol substitutes both the gai of quadrature compoets of the sigal ad gai of i phase, either joitly or idepedetly. The phase frequecy offset is applied. I the last part the sigal is filtered by raised cosie filter ad demodulated by rectagular 16-QAM. BER (bit error rate) block gives a scope to show the error rate. The model parameters ca be updated through the bock provided i above architecture. The above system gives a stadard error rate about 30 db as show i figure2 [4]. The simulatio of the system gives the differece of power level i trasmissio ad receptio of sigal, which deotes the presece of oise i system. It ca be improved by chagig some specific parameters to reduce the sigal oise ratio. Hece to achieve the same as a aim of the research, there is aother modified system is proposed. III. PROPOSED SYSTEM The proposed system has same architecture but parameters are updated i such a way that the system provides the optimum result with miimum oise. Whe the trasmit ad receive atea diameter chages to 7*7meters, oise temperature as 0k, HPA as usual, phase correctio set to HPA AM to PM, ad lastly I/Q imbalace to 3 db, it gives drastically optimum result with least amout of oise preset. The simulated model result is show i figure3. Figure3-Updated Simulatio of Noise Level I SDR GNSS Here as show i figure3[6], it ca be determied that the power spectral desity ad frequecy plot of the updated SDR GNSS system has oise level egligible, as there is almost o differece i power cosumptio of trasmittio ad receiptio.it deotes that correct data stream is detected at the receiver ed. The overlappig of trasmitter ad receiver s frequecy ad power relatioship plot provides optimum coditios of system s performace. IV. MATHEMATICAL MODEL The mathematical model is developed accordig to the implemeted model oly. I.Problem descriptio Let S be a SDR GNSS where where R represets receiver of the system; Ad T represets trasmitter of the system Ad D represets data stream to be trasmitted ad received; Figure2-Simulatio Of Noise Level I Stadard SDR GNSS N represets how may oise detected i the received sigals; 11

3 Iteratioal Joural of Computer Techology ad Electroics Egieerig (IJCTEE) Volume 5, Issue 3, Jue 2015 C represets chael of the trasmitter ad receiver; B represets badwidths used i trasmitter ad receiver chaels II. Activity 1 Let be the rule of R ito T such that seder will sed the data stream to the receiver Let be the rule of T ito D such that trasmitter trasmits data stream Let be the rule of D ito R such that data streams received by receiver Let be the rule of D ito N such that data streams cotai oise Let be the rule of C ito N such that each chael cotais some oise level Let be the rule of C ito T such that trasmitter is sigle chaeled Let be the rule of C ito R such that receiver is sigle chaeled Let be the rule of C ito B such that chael ca have multiple badwidth iii. Vei Diagram As described i activity1 followig vei diagram is draw IV (A) fuctios of the project Fuctio: Executio time: Trasmissio / receptio Filter ad amplificatio of iformatio Aalog to digital coversatio Digital to aalog coversatio Samplig Quatizatio 12

4 Data processig Noise detectio ISSN Iteratioal Joural of Computer Techology ad Electroics Egieerig (IJCTEE) Volume 5, Issue 3, Jue 2015 Frequecy maagemet IV(B) if Bit error rate is less tha threshold the decrease the frequecy of sigal up to threshold, whe above threshold it starts icreasig. V. Result through aalysis If the SNR value is less tha threshold frequecy, the allow the sigal to trasmit ad receive. If the SNR value is above the threshold the icrease the frequecy level ad cotiue. VI. State diagram V. ANALYSIS OF RESULT TABLE I ANALYSIS OF THE SYSTEMS PERFORMANCE,,,,,, VII. Fuctioal depedecy,,

5 Iteratioal Joural of Computer Techology ad Electroics Egieerig (IJCTEE) Volume 5, Issue 3, Jue 2015 Here as show i the TABLE I, which is made after various case observatios, all the parameters made varied, which are puttig impact o the system performace. Like atea diameter (meters) the values are i decimal like 0.4 deotes 4meters, oise temperature of the system (Kelvi), HPA back off level (db), phase correctio ad I/Q imbalace. Result is observed that whe the oise temperature ad I/Q imbalace factors are varied it put great effect i reductio of oise ratio as compared to other parameters variatio accordigly. The each ad every parameters effect o the performace with respect to other parameters is carefully observed. Such as the probability of atea diameter was checked with respect to other parameter s usual operatig values ad tabulated above. Agai i secod case the oise temperature was varied with its probable values ad remaiig parameters are kept costat, the relevat effect i result was oticed ad tabulated, So o. Hece the above observatio table was prepared with various probable case experimetatios. Agai the above table gives a clear visio about the parameters effect o performace. VI. CONCLUSION This paper elaborates SDR GNSS architecture i detail usig MATLAB. Here, differet parameters of the system are varied with respect to others ad optimized result is verified. I the ear future [7] the architecture will be modified to give better performace with respect to sigal to oise ratio. REFERENCES [1] J. Mitola, III, Software radios: Survey, critical evaluatio ad future directios, i IEEE Aerospace ad Electroic Systems Mag., vol. 8, pp , Apr [2] Special issue o software radios, IEEE Joural o Selected Areas i Comm., vol. 17, o. 4, Apr [3] Special issue software radio, IEEE Persoal Comm., vol. 6, o. 4, August [4] Hurskaie, Heikki, Jussi Raasakka, Tapai Ahoe, ad Jari Nurmi. "Multicore software-defied radio architecture for GNSS receiver sigal processig." EURASIP Joural o Embedded Systems 2009 (2009): 3. [5] J.Mitola, The software radio architecture, IEEECommu.Magazie., vol.33, pp , May [6] Abul Hasa, Effort-Reduced Calibratio of Six-Port Based Receivers for CR/SDR Applicatios, IEEE Joural o Emergig ad Selected Topics i Circuits ad Systems, vol. 3, o. 4, Dec [7] G. Hei, T. Pay, W.Stefa ad J.-H. Wo Platforms for a Future GNSS Receiver, IsideGNSS, pp 56-63, March