International Journal of Scientific & Engineering Research, Volume 7, Issue 12, December-2016 ISSN

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1 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS Ehacemet of SDR through FBMC Commuicatio THIAKARA Dr D Kumar Dea ao ad Prof, Dept of ECE, Periyar Maiammai Uiversity, Vallam, Thajavur, Tamiladu, Idia headao@pmu.edu Research Scholar, Dept of ECE, Periyar Maiammai Uiversity, Vallam, Thajavur, Tamiladu, Idia thia_kara65@rediffmail.com Abstract As the fourth geeratio telecommuicatio is eterig ext geeratio, all the Radio commuicatios are becomig software orieted. Software Defied Radio (SDR) is iitially addressed followed by the techology of Orthogoal Frequecy Divisio Multiplexig (OFDM). OFDM which is i the verge of replacemet, is aalysed ad a alterate commuicatio techology amely Filter Bak Multicarrier Commuicatio (FBMC) is suggested. The techology ad types of FBMC are discussed. OFDM ad FBMC are compared. I this paper simple FBMC is implemeted ad the results are give. Key Words SDR, OFDM, FBMC, ISI, ICI, Equalisatio. I ITRODUCTIO As the moder telecommuicatio is improvig over each decade, two treds cotiue to persist. They are data rate ad ability to sed iformatio idepedet of locatio ad time. The software based radio commuicatio eables the latest ICT devices a recofigurable oe. Data rate demad is icreasig beyod Gbps. The preset 4G LTE [] techology uses OFDM commuicatio techiques. This has iheret problem of spectrum leakage ad maiteace of Orthogoality amog all sub-carriers. There is eed for high data rate ad low latecy, as the world moves towards fifth geeratio Commuicatio. Filter Bak Multicarrier Commuicatio (FBMC) is very old FDM techology ad due to complexity i implemetatio, this could ot see the stadards. With the advet of ew fast processors, FBMC is suggested as ext geeratio Commuicatio layer. I order to implemet the FBMC, i Sectio-II cocept of Software Defied Radio (SDR), workig of OFDM is described. The Sectio-III deals with the cocept of FBMC ad its implemetatio. I Sectio IV a compariso is brought out with OFDM ad FBMC. Sectio-V gives the coclusio ad future research work. II Radio is a device which trasmits ad / or receives sigals i the Electro-magetic Spectrum to trasfer iformatio such as voice, music, ad data. Scietifically the frequecies are grouped from 3 KHz to 300 GHz as Extremely Low Frequecy (ELF) to Extremely High Frequecy (EHF) uder the various frequecy bads. I SDR-Trasmitter the iformatio is formatted ito Digital iput, mi, i the form of message symbols. The these symbols could be coverted ito bit stream, uj, by source ecodig, ecryptig(for secrecy), chael ecodig ad multiplexig(for multi sigals) process. Depedig upo the source codig ad multiplexig, the date rate of streams ca be cotrolled. After that desired Pulse codig could be udertake usig modulatio such as PAM, QAM, PSK, FSK, OFDM or its variats to form Electromagetic waves suitable to atea characteristics. After it travels thru media, the sigal is received at the receiver. I SDR-Receiver, the received sigal from Atea is demodulated after carrier sychroizatio ad automatic Gai cotrol, usig appropriate Demodulatio techiques such as OFDM, QAM, FSK, PSK ad its variats, to make the bit stream. From Bit Stream, after symbol sychroizatio ad frame sychroizatio, the message is recostructed successfully. The SDR Tx-Rx is give i the figue. below. COCEPTS OF SDR AD OFDM A. SDR[] The SDR Forum which is workig alogwith IEEE P900. group has defied SDR as Radio i which some or the etire physical layer fuctios are software defied. 06 Figure.. Block diagram of SDR Tx ad Rx.

2 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS Most of the above fuctios ca be executed i a Digital Sigal Processor (DSP) or Field Programmable Gate Array (FPGA) or Geeral Purpose processor (GPP) usig Algorithms, middleware, Rate Covertor software. The SDR Forum has characterized this SDR architecture with the data flow metioed i Figure.. give below. Figure. 3. OFDM Waveform. Parallel data streams are set. Data ecodig is based o Amplitude Modulatio. Multiple Carriers are combied through the Fourier series, which is computed by Iverse Fast Fourier Trasform (IFFT). Pictorially a example of 4-QAM Modulatio ca be represeted as below:- Figure.. SDR Forum s SDR Architecture with Data Flow. Pure Software Radio is yet a distat dream due to high architectural Complexity ad high Flexibility. Software Defied Radio (SDR) is the oe which has medium architectural Complexity ad more tha medium Flexibility. These radios are recofigurable oe where i the software ca be upgraded or added with other modes of radio or frequecy of operatio. B. OFDM [3] [4] Digital Modulatio modulates fudametally three parameters viz., Amplitude (A), Phase (θk) ad Frequecy (fc) of siusoidal sigal. Mathematically, to represet ASK, PSK ad FSK, this ca be writte as, () s(t ) A cos( f t ) c k OFDM uses a combiatio of ASK ad PSK modulatio such as QAM ad PSK. By expadig ad assigig, we obtai, ak cos k, bk si k s (t ) Re[( ak jbk )e j fc t ] () e j fc t idicates carrier siusoidal ad (ak jbk ) idicates Digital Modulatio, by a complex umber. OFDM is a multi-carrier amplitude modulatio scheme where each carrier s amplitude is modulated. It uses DFT/FFT. Si X / X spectra is used for sub-carriers. Available badwidth is divided ito may arrow-bads. Data is trasmitted i parallel o these bads. The typical OFDM is show as follows:- Figure QAM Modulatio. Total Power spectrum of OFDM is almost like a rectagular pulse shape. Orthogoality i Frequecy ad Time domai is maitaied. Overlap of frequecy respose is possible as agaist FDM where iter-carrier spacig is a must. Frequecy resposes of the carriers overlap at Zero Crossigs avoidig Iter-Carrier-Iterferece (ICI). Frequecy-Time Represetatio of a OFDM Sigal ca be depicted as follows:- Figure. 5. OFDM Modulator-Demodulator is desiged as follows with Trasmitter ad Receiver:- 06

3 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS The BER curve Vs SR implemeted i SciLab software is give i figure.6b. Figure. 6a. OFDM Modulator-Demodulator. Defiig the complex base-bad sigal u( i the followig way for covertig the OFDM sigal ito digital domai, B u( s ( Re u( d e 0 j f t, d a jb (3) 0 After performig Times samplig i period T, we get, k 0 0 k j f k j f u d e d e f0 0 0 k j Figure. 6b. OFDM with AWG Chael BER Curve Vs SR d (4) e ( k 0,,,, ) 0 u(k) = IFFT(d ) = IFFT(a + jb ) (5) II COCEPTS OF FBMC Filter Bak Multi Carrier (FBMC) [5] [6] At Receiver mathematically followig ca be performed to get commuicatio systems are a subclass of Multi-carrier back the data symbol, d. Systems. This techique was first developed i the mid-960s. s( a Chag [7] ad Saltzberg [8] have itroduced PAM Symbol cos ( fc f0) t b si ( fc f0) t 0 trasmissios ad QAM symbol Trasmissios parallelly with filter-baks theory for efficiet Badwidth maagemet. LPF[ s( cos( fc] a cos(f0 b si(f0 si ( 0 There are three major types of FBMC. They are suggested by differet authors [6]. They are as follows:- LPF[ s( si( fc ] a si(f0 b cos(f0 sq ( FMT. Filtered Multi Toe FBMC uses subcarrier bads 0 with o overlap. Data symbols are QAM. CMT. Cosie Modulated multi toe-fbmc uses subcarrier with maximum overlap. j f0t u( si ( jsq ( d e (6) SMT. Staggered Modulated Multi toe-fbmc uses 0 subcarrier bads with maximum overlap. Data Symbols use d = FFT(u(k)) (7) PAM with VSB Modulatio. It is also kow as Offset QAM (OQAM). The IEEE OFDM Stadards, IEEE 80.a is briefly listed below:- FMT based FBMC is built o the covetioal method kow as Frequecy Divisio Multiplexig (FDM). FMT-FBMC System is a filter bak modulatio techique i which, brach filters are frequecy-shifted-basebad filters, called prototype filter, that achieves high level of spectral cotaimet. ICI is resolved through use of well-desiged filters with high stop-bad atteuatio. ISI may be 06

4 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS compesated for by adoptig the covetioal method of square-root yquist filterig. FBMC Techology FBMC Commuicatio uses Sample Rate Coverters (UP ad DOW), Prototype Filter ad Filter Baks as backboe elemet. The iput-output relatio of Up Coverter is give as yk[] = x[/l], = ml, m is a iteger 0, otherwise () The best prototype filter, p[], desiged as part of PHYDYAS Filter[9] at Europe is give below:the impulse respose is give as (8) The iput-output relatio of Dow Coverter is give as yd[] = x[m], M is a iteger (9) Prototype Filter is desiged to match the time ad frequecy spread of chael which is give below:- () The frequecy respose is give as Choose h( so that H(f) = h(lf), for a costat scalig factor l. The oe may fid that (T/ ) = (F/ ) = =l (0) Or T/F = The above is pictorially give as follows:- Let p( be a prototype filter ad with sample poits i the filter legth +, where is a iteger greater tha. The parameters are to be foud for optimal desig of prototype filter. p[] is give as Figure. 7. Frequecy Respose 06 (3)

5 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS shifted versios of Low Pass Prototype. It is achieved by multiplyig the prototype with a modulatio fuctio. FMT- FBMC-Tx is implemeted as follows with umber of Sub carriers, s k [] data symol o the k th subcarrier FMT Symbol, L= K, symbol period, K oversamplig factor ad x[] is the trasmitted FMT- FBMC sigal. Figure. 8. Impulse Respose The same was simulated through MATLAB ad the results are depicted below:- Figure. 0a. FBMC FMT Trasmitter Block Diagram. FMT-FBMC-Receiver is implemeted as follows:- Figure. 9. PHYDYAS Filter Impulse Respose (4) Filter Baks Filter Bak is a system that comprises of a Group of Filters which processes a commo iput or result ito a commo output. Filter baks either break dow a iput sigal to form sub-bad compoet sigals or combie the sub-bad sigals to form the output sigal. There are two major types of Filter baks viz., Aalysis Filter Bak (AFB) ad Sythesis Filter Bak (SFB). AFB is used for aalyzig the iput sigal accordig to characteristics of each filter. SFB is used to filter the idividual sigals ad added to get combied ew composite sigal. For haressig the real power of filter baks, it has to be used i pairs, either AFB-SFB combiatio as Sub-bad Systems or as SFB-AFB pair as Trasmultiplexers. SFB-AFB combiatio is used i multicarrier commuicatio as Tx-Rx pair. Decimatio, i.e dow coversio takes place at AFB ad it cosists of the filterig of the iput sigal (ati-aliasig Filterig) ad subsequet dow-samplig. Iterpolatio, i.e., takes place at SFB ad it cosists of a up-sampler ad a iterpolatio filter (Atiimagig filterig). Modulated Filter Baks are frequecy Figure. 0b. FBMC FMT Receiver Block Diagram. 06

6 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS (5) (6) With Polyphase etwork, FMT-FBMC system ca be implemeted with least complexity [4] [6]. Simplified FBMC Implemetatio ad Results Figure.3. Costellatio Diagram of 4-QAM- FBMC with AWG Chael The FBMC Trasmitted pulse power is depicted at figure.4. A simple FBMC Tx-Rx is implemeted by us usig MATLAB. The block diagram of FBMC system is give i Figure.. Figure.4. Trasmitted Pulse of 4-QAM- FBMC. Figure.. Block diagram of Simple FBMC System. The costellatio diagram of above FBMC with 4 QAM symbols, 64 Subcarriers, 4 Frames ad AWG Chael is give i figure.. IV COMPARISIOS OF OFDM Vs FBMC The OFDM ad FBMC are aalysed ad discussed. The results are compared i the followig Tables ad figures. Figure.. Costellatio Diagram of 4-QAM- FBMC with AWG Chael both trasmitted ad received symbols. The Bit-Error-Rate for the above FBMC system i AWG Chael is give at figure Table.. OFDM Vs FBMC Compariso

7 Iteratioal Joural of Scietific & Egieerig Research, Volume 7, Issue, December-06 ISS Errors, Time Offset ad Frequecy Offset. Though ICI (Iterferece of Symbols from other subcarriers i the same idex) ad ISI (Iterferece of Symbols i differet time idex from all subcarriers) depeds upo Pulse-shape, Chael ad Data, it ca be mitigated through Chael Equalisatio, Chael Estimatio ad Sychroisatio techiques i the future. VI REFERECE [] [] Figure. 5. Compariso of Power Spectral Desity. [3] [4] [5] Sueel Kumar et al., Ja. 06, A Future Commuicatio Techology: 5G, Iteratioal Joural of Future Geeratio Commuicatio ad etworkig, Vol. 9, o. (06), pp Jeffrey. Reed, May 99, Software Radio: A Moder Approach to Radio Egieerig, Pretice Hall Commuicatios Egieerig ad Emergig Techologies Series, ew Jersey 07458, ISB Fire Tom Wada, "Itroductio to OFDM," accessed i April 05. Proakias, J, Digital Commuicatios, d Editio, Iteratioal Series i Electrical Egieerig (Commuicatio ad Sigal Processig), McGraw-Hill Book Compay, ew York, 989, ISB: Behrouz Farhag-Boroujey, OFDM Versus Filter Bak Multicarrier, IEEE Sigal Processig Magazie, May 0, pp-9. Behrouz Farhag-Boroujey, Filter Bak Multicarrier Modulatio: A waveform Cadidate for 5G ad Beyod, Advaces i Electrical Egieerig, Hidawi Publishig Corporatio, Volume 04, Review Article ID 48805, pp--5. Chag, R et al, Theoretical Study of Performace of a Orthogoal Multiplexig Data Trasmissio Scheme, IEEE Tras. Comm, Vol. 6(4), Aug 968, pp Saltzerg, B.R, Performace of efficiet parallel data trasmissio, IEEE Tras. Comm, Vol. COM-5(6), Dec 967, pp M.Bellager et al, Jue 00, FBMC physical Layer : a Primer, pp-3 [6] [7] Figure.6. BER Vs Eb/o of OFDM Type umber of X umber of + OFDM USIG (/)LOG LOG FFT OF LEGH =K FBMC OF + ORDER SYMMETRICAL POLYPHASE /L REP WITH L UPSAMPLIG FACTOR Table.. OFDM Vs FBMC Computatio Compariso [8] [9] With the above comparisos i Bit Error Rate, Spectrum Efficiecy, Computatios, FBMC is the best cadidate i compariso with OFDM for 5G Commuicatio. V COCLUSIO AD FUTURE WORKS The preset 4 G Commuicatio Techology based o OFDM is proe to spectrum leakage, strict Orthogoality coditios amog etire sub-carriers. Its rectagular pulseshape icreases susceptibility to sychroisatio errors. I order to mitigate the major drawbacks, ew Commuicatio techology based o FBMC techiques are suggested for future SDR. It has more spectrum efficiecy, more flexibility to use differet pulse shape ad efficiet power cotrol. This FBMC Systems ca also be susceptible to Sychroisatio 06