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Ix2415611565

  1. 1. B. Naga Nancharamma, L.Srinivas / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1561-1565 Implementation And Analysis Of PAPR Reduction In DHT & DFT-Precoded Wireless OFDM SYSTEM B. NAGA NANCHARAMMA L.SRINIVAS M.Tech Student Scholar, DECS, M.Tech, Asst Professor Dept of Electronics and Communication Dept of Electronics and Communication Engineering, Engineering, Nalanda Institute of Engineering and technology, Nalanda Institute of Engineering and technology, Sattenapalli (M); Guntur (Dt); A.P, India. Sattenapalli (M); Guntur (Dt); A.P, IndiaAbstract In this Correspondence, analyze High So The next generation wireless and wiredPeak to Average Power Ratio (PAPR) ,In line digital communication systems Because it hasorthogonal Frequency Division Multiplexing High speed data rates, high spectral efficiency, InPAPR is one of the major drawback. Analogue to frequency selective fading high quality service andDigital (A/D) and Digital to Analogue (D/A) robustness against narrowband interference.convertors increases the complexity in High PAPR Frequency selectivity moderates in Multipathand also reduces the efficiency of RF High Power channel and inter symbol interference by insertingAmplifier (HPA). In this paper we present a Guard interval by using Cyclic Prefix(CP) withanalysis of precoded OFDM systems of Discrete simple equalizer due to this implementationHartley Transform (DHT) using M-QAM (where Hardware implementation cheap and makes design ofM=16,32, 64,256). We compare the simulation the receiver simple to design.results with DFT precoded OFDM system, WalshHadamard Transform (WHT) precoded OFDM The various communication standards likesystem, Selected Mapping (SLM) based OFDM Digital Audio Broadcasting (DAB), Wirelesssystem and OFDM conventional. Simulation Metropolitan Area Networks (WMAN),Digital Videoresults show that the PAPR of WHT precoded Broadcasting (DVB), Digital Subscriber LinesOFDM system is greater than DHT precoded (xDSL), Wireless Local Area Networks (WLAN), ,OFDM system, SLM-OFDM system and OFDM Wireless Personal Area Networks (WPAN) and evenconventional. Lastly we concluded DFT precoded in the beyond 3G Wide Area Networks (WAN) etcOFDM system has Zero PAPR. are adapted in OFDM Systems. Additionally, In Wireless Asynchronous Transfer mode (WATM)Keywords- High Power Amplifier, DFT OFDM is the strong Candidate among others ,InPrecoder, DHT Precoder, WHT Precoder. transmitted OFDM signal Peak to average Ratio(PAPR) is one of the major drawback[2].I. INTRODUCTION Therefore, distortion of the OFDM signal is zero, the Orthogonal Frequency Division HPA must not only operate in its linear region but Multiplexing (OFDM) is a digital multi carrier also with sufficient back-off. Thus, the RF High modulation scheme, which uses a large number of Power Amplifier (HPA) with a large dynamic range closely spaced orthogonal sub-carriers. A single are required for OFDM system. The cost of These stream of data is split into parallel streams each of amplifiers are very expensive and are major cost which is coded and modulated on to a subcarrier, a component of the OFDM System. term commonly used in OFDM systems. Orthogonal Frequency Division Multiplexing (OFDM) is a digital Cost of the OFDM system reduces when if multi carrier modulation scheme, which uses a large we reduce the PAPR not only in the scene of cost also number of closely spaced orthogonal sub-carriers. A complexity of the Analogue to Digital (A/D) single stream of data is split into parallel streams each converters, but also increasing the transmit power of which is coded and modulated on to a subcarrier, a Signal to noise ratio improving same range, or for the term commonly used in OFDM Each sub-carrier is same SNR improving range ,Many reduction modulated with a conventional modulation scheme at techniques regarding PAPR proposed in the a low symbol rate, maintaining data rates similar to literature. PAPR reduction methods have been conventional single carrier modulation schemes in the studied for many years and significant number of same bandwidth. Thus the high bit rates seen before methods has been developed. These methods are on a single carrier is reduced to lower bit rates on the clipping and coding. Clipping naturally happens in subcarrier. the transmitter if power back-off is not enough. Clipping leads to a clipping noise and out-of-band radiation. methods include Golay complementary 1561 | P a g e
  2. 2. B. Naga Nancharamma, L.Srinivas / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1561-1565sequences [Error! Reference source not found.], numbers). The N real numbers x0, ...., xN-1 areblock coding scheme [Error! Reference source not transformed into the N real numbers H0, ..., HN-1 .found.], complementary block codes (CBC) [Error! Walsh-Hadamard transform is an efficient algorithmReference source not found.], modified to reduce the computational complexity ,it requirescomplementary block codes (MCBC) [Error! additions or subtractions. An RF power amplifier is aReference source not found.] etc. Among them The type of electronic amplifier used to convert a low-techniques like coding Schemes[4,5],phase power radio-frequency signal into a larger signal ofoptimization[6],nonlinear companding transform[7] significant power, typically for driving the antenna of,Tone Reservation(TR) and Tone Injection a transmitter. It is usually optimized to have high(TI)[8,9],clipping and filtering are popularly used efficiency, high output Power compression. The basicthese techniques. applications of the RF power amplifier include driving to another high power source, driving a A soft clipping techniques which preserves transmitting antenna, microwave heating, andthe phase only the amplitude proposed by Wang and exciting resonant cavity structures. Among theseTellambura[10].To discover some properties to applications, driving transmitter antennas is most wellsimplify the PAPR gain is only estimated and limited known.to specific class of modulation techniques and put a This paper analyses PAPR of the DHT-lot of effort to characterize the performance of PAPR. Precoding based OFDM system for PAPR reductionThe authors Han and Lee Proposed a PAPR reduction organized as follow sections: Section II describes thetechniques based on which they divide the frequency OFDM system basics and PAPR reduction, In Sectionbins into sub blocks and they multiply each sub block III presents our proposed technique ,Section IVwith a constant phase shift simply called as Partial presents simulation results and Section V concludesTransmit technique. PAPR Reduces when choosing the paper.the appropriate phase shift values. To find out theoptimal phase value is the most critical part of this II. OFDM SYSTEM & PAPR REDUCTIONtechnique, combination and in this regard they also The OFDM system transmitted low ratesproposed a simplified search method and evaluated data streams simultaneously over a number ofthe performance of the proposed work. orthogonal subcarriers, and these low data rates getting from splitting the high speed data stream into PSLM technique for PAPR developed a number of parallel low data rate streams.authors in[12],In this technique Zadoff–Chu basedprecoder is applied after the multiplication of phaserotation factor abd before the IFFT in OFDM system.The proposed technique PSLM is signal independentand it does not require any complex optimizationtechnique. Single Carrier Frequency DivisionMultiple Access(SCFDMA) is proposed Zero PAPRZadoff-Chu precoder based technique is efficient,signal independent, distortion less, it does not requireany optimization algorithm and PAPR is completelyeliminated. Figure 1: Block diagram of an OFDM system Discrete Fourier transform (DFT) is aspecific kind of discrete transform, used in Fourier Fig.1 shows the block diagram of an OFDManalysis. It transforms one function into another, system. Baseband modulated symbols are passedwhich is called the frequency domain representation, through serial to parallel converter which generatesor simply the DFT, of the original function. FFT complex vector of size N. We can write the complexalgorithms are so commonly employed to compute vector size as X=X0.The symbols passed throughDFTs that the term "FFT" is often used to mean IFFT block. the complex baseband OFDM signal"DFT" in colloquial settings. with N subcarriers can be written as A Discrete Hartley transform (DHT) is aFourier-related transform of discrete, periodic datasimilar to the discrete Fourier transform (DFT), withanalogous applications in signal processing and Here j= √(-1) and the PAPR of the OFDM of signalrelated fields. Its main distinction from the DFT is (1) can be written asthat it transforms real inputs to real outputs, with nointrinsic involvement of complex numbers. Formally,the discrete Hartley transform is a linear, invertible Where E[.] denotes complementary and thefunction H : Rn -> Rn (where R denotes the set of real exceptions Cumulative Distribution Function(CCDF) for an OFDM signal can be written as 1562 | P a g e
  3. 3. B. Naga Nancharamma, L.Srinivas / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1561-1565Where PAPR0 is the clipping level.this euation can (9)be read as the Probability that the PAPR of a symbolblock exceed some clip level PAPR0 Where m and n integers ranging from0 to N-1 and P is precoding matrix ofIII. ANALYSIS OF THE PROPOSED size N x N. CONCEPTA. The Precoding Based OFDM system C. The Discrete Hartley Transform (DHT) In Fig.2.shows the block diagram of PrecodingPrecoding Based OFDM System. To reducing PAPR The DHT is a linear transform. In DHT N, In Precoding matrix we implementing P of real numbers X0,X1,… X(N-1)are transformed in to Ndimension N x N before the IFFT. real numbers H0, H1,… H(N-1)According to [15] the _-point DHT can be defined as (10) Where cos(i)=cos i+sin i and k=0,01,.....N-1 (11) Where P is a precoding matrix of size N x N shown in equation (4),m and n integers from 0 to N-1.Fig .2. Block diagram of Pre IFFT based OFDMsystem IV. MATLAB/SIMULINK RESULTS OF THE PROPOSED CONCEPTThe Precoding matrix P can be written as To evaluate the performance of DHT Precoder based OFDM system is shown in simulation results. To show the PAPR analysis of DHT-precoded OFDM system, data is generated randomly then modulated by M-QAM(where M=16,32,64,256).we compared our simulation results with WHT-Precoder OFDM system, DFT Precoding system and Original where P is a Precoding Matrix of size _ × _ System. To show the overall performance of the DHTis shown in equation (4). The complex baseband precoder based OFDM system for PAPR reduction inOFDM signal with _ subcarriers can be written as MATLAB we considered M-QAM for N=16,also we considered results in M-QAM are N=32,64,256 ,then compare the results with different precoding systemsThe modulated OFDM vector can be express signal and show the output simulation results.with subcarriers N as. Figure.3 shows the CCDF comparisons of DHT-Precoder Based OFDM System with DFT(6) precoder based OFDM system, WHT-PrecoderThe PAPR of OFDM signal in (5) can be written as system and Original System for N=16.At clip rate 0.01.DHT precoding based OFDM system does not perform as well as DFT-Precoding based OFDM system, Which is better than DHT-Precoding based OFDM system. Thus PAPR gain to achieve the betterB. The Discrete Fourier Transform (DFT) results with DHT Precoded system with other Precoding precoding systems DFT,WHT . The sequence of DFT of length N can bedefined as(8)and IDFT can be written as 1563 | P a g e
  4. 4. B. Naga Nancharamma, L.Srinivas / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1561-1565 perform as well as DFT-Precoding based OFDM system, Which is better than DHT-Precoding based OFDM system. Thus PAPR gain to achieve the better results with DHT Precoded system with others.Fig.3. CCDF comparison of DHT-Precoder BasedOFDM System with DFT-Precoder Based OFDMsystem, WHT-Precoder Based OFDM System, andOFDM Original System for 16-QAM Fig.5. CCDF comparison of DHT-Precoder Based Figure.4 shows the CCDF comparisons of OFDM System with DFT-Precoder Based OFDMDHT-Precoder Based OFDM System with DFT- system, WHT-Precoder Based OFDM System, andPrecoder based OFDM system, WHT-Precoder OFDM Original System for 64-QAMsystem and Original System for N=16.At clip rate0.01.DHT precoding based OFDM system does not Figure.6 shows the CCDF comparisons ofperform as well as DFT-Precoding based OFDM DHT-Precede Based OFDM System with DFTsystem, Which is better than DHT-Precoding based precede based OFDM system, WHT-Precoder systemOFDM system. Thus PAPR gain to achieve the better and Original System for N=16.At cliprate 0.01.DHTresults with DHT Precoded system with others precoding based OFDM system does not perform as well as DFT-Precoding based OFDM system, Which is better than DHT-Precoding based OFDM system. Thus PAPR gain to achieve the better results with DHT Precoded system with others.Fig.4. CCDF comparison of DHT-Precoder BasedOFDM System with DFT-Precoder Based OFDMsystem, WHT-Precoder Based OFDM System, andOFDM Original System for 32-QAM Fig.6. CCDF comparison of DHT-Precoder Based OFDM System with DFT-Precoder Based OFDM Figure.5 shows the CCDF comparisons of system, WHT-Precoder Based OFDM System, andDHT-Precoder Based OFDM System with DFT OFDM Original System for 256-QAMprecoder based OFDM system, WHT-Precodersystem and Original System for N=16.At clip rate0.001.DHT precoding based OFDM system does not 1564 | P a g e
  5. 5. B. Naga Nancharamma, L.Srinivas / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1561-1565V CONCLUSION scheme for OFDM systems: Selective In this Paper ,PAPR of DHT-Precoded mapping of partial tones (SMOPT)”, IEEEOFDM system for M-QAM (Where Trans. Consumer Electronics, vol. 52, no. 1,M=16,32,64,256) analyzed. The simulation results pp.40–43, Feb. 2006.shows that DHT-Precoded OFDM System shows [10] Luqing Wang and Chintha Tellambura ,”Abetter PAPR gain as compared to OFDM-Original Simplified Clipping and Filtering Techniquesystem, WHT-Precoder Based OFDM system for PAR Reduction in OFDM Systems”,respectively. Thus, it is concluded that DHT Precoder Signal Processing Letters, IEEE , vol.12,Based OFDM System shows better PAPR reduction no.6, pp. 453-456, June 2005.then WHT-Precoder Based OFDM System, and [11] S.Hee Han and J.Hong Lee, "PAPROFDM-Original system for MQAM. Additionally, Reduction of OFDM Signals Using athe DHT-Precoded OFDM system does not require Reduced Complexity PTS Technique",any power increase, complex optimization and side Signal Processing Letters, IEEE, Vol.11,information to be sent for the receiver. Iss.11, Nov. 2004, Pages: 887- 890. [12] Varun Jeoti and Imran Baig, “A NovelReferences Zadoff-Chu Precoder Based SLM Technique [1] Yiyan Wu and Zou Y. William, “Orthogonal for PAPR Reduction in OFDM Systems”, frequency division multiplexing: A multi- invited paper, Proceedings of 2009 IEEE carrier modulation scheme”, IEEE Trans. International Conference on Antennas, Consumer Electronics, vol. 41, no. 3, pp. Propagation and Systems (I_AS 2009), 3-5 392–399, Aug. 1995. Dec. 2009, Johor, Malaysia. [2] R.van Nee and A. de Wild, “Reducing the Peak-To-Average Power Ratio of OFDM”, Vehicular Technology Conference, 1998. VTC98. 48th IEEE, Volume.3, 18-21 May 1998, pages: 2072-2076. [3] Yajun Kou, Wu-Sheng Lu and Andreas Antoniou, “A new peak-toaverage power- ratio reduction algorithm for OFDM systems via constellation extension”, IEEE Trans. Wireless Communications, vol. 6, no. 5, pp. 1823–1832, May 2007. [4] Tao Jiang and Guangxi Zhu, “Complement block coding for reduction in peak-to- average power ratio of OFDM signals” , IEEE Communications Magazine, vol. 43, no. 9, pp. S17–S22, Sept. 2005. [5] S.Ben Slimane, “Reducing the peak-to- average power ratio of OFDM signals through precoding”, IEEE Trans. Vehicular Technology, vol. 56, no. 2, pp. 686–695, Mar. 2007. [6] Homayoun Nikookar and K.Sverre Lidsheim, “Random phase updating algorithm for OFDM transmission with low PAPR”, IEEE Trans. Broadcasting, vol. 48, no. 2, pp. 123–128, Jun. 2002. [7] Tao Jiang, Wenbing Yao, Peng Guo, Yonghua Song and Daiming Qu, “Two novel nonlinear Companding schemes with iterative receiver to reduce PAPR in multicarrier modulation systems”, IEEE Trans. Broadcasting, vol. 52, no. 2, pp. 268– 273, Mar. 2006. [8] J.Tellado-Mourelo, “Peak to Average Power Ratio Reduction for Multicarrier Modulation”, PhD thesis, University of Stanford, 1999. [9] Seungsoo Yoo, Seokho Yoon, S.Yong Kim, and Iickho Song, “A novel PAPR reduction 1565 | P a g e

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