ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com PAPR Reduction Analysis of OFDM signals in DVB-T system using SLM and PTS techniques Syed Gilani Pasha, Vinayadatt V Kohir 2 Research Scholar, Visvesvaraya Technological Univsity, Belagavi, Karnataka 2 Professor, Dept. ECE, P.D.A College of Engineing, Gulbarga Abstract: DVB-T uses vy popular multicarri modulation system such as OFDM and the OFDM signals in DVB-T has high Peak to Avage Pow Ratio (PAPR). One way to reduce the high PAPR is by using efficient techniques. In this research, we analyse the PAPR reduction of OFDM signals using SLM and PTS techniques. The input consided for DVB-T system is video signal taken from intnet. The simulations of these techniques are carried out using MATLAB. Keywords: OFDM, DVB-T, SLM, PTS, QAM, PAPR, Techniques I. INTRODUCTION Digital trestrial television (DTT) is also called as Digital Video Broadcasting-Trestrial (DVB- T) television is currently an efficient communication technology for broadcasting television (TV) signals[]. The European digital television ETSI EN 3 744, standard is DVB-T, for the trestrial transmission to fixed, portable, and mobile receivs[2]. The specification of framing structure, channel coding and modulation, for digital trestrial broadcasting is provided by DVB-T Standard. DVB-T system refs, to the source coding of data, audio signals and video signals, the channel coding and the technique for the transport of the DVB-T signals by means of all type of transmission media. In DVB-T, the OFDM is used to transmit 2k and 8k mode carris ov AWGN, Rician and Rayleigh Channel, the received signal at the receiv is corrupted. The corrupted received signal is manipulated in tms of SNR values (ranging from db to 6dB) and modulation techniques (4-QAM, 6-QAM 64-QAM and 28-QAM). OFDM modulation [3] is attractive technique for high data rate transmission, since it can cope with frequency selective fading channel. The Fig. gives the DVB-T System Physical Lay block diagram. In DVB-T the most sious problem of OFDM is high Peak to avage pow ratio (PAPR) which causes degradation of system pformance. So reduction of PAPR is vy much needed in ord to utilize the benefits of OFDM for DVB-T applications. Various PAPR reduction techniques are proposed in litature for OFDM system and in this research we have consided the most widely used techniques such SLM and PTS [4][5]. A. OFDM Model and PAPR Consid discrete time OFDM model having N subcarris then the discrete time OFDM signals is whe n = {,,...,N }. We will have x = {X}, whe X = [X(),...,X(N )] T, x = [x(),..., x(n )] T. Theoretically, the PAPR of OFDM signal is given as () (2) Whe E [ ] indicates the expectation opator, x(n) denotes the transmitted OFDM discrete signals which are obtained by applying (invse fast Fouri transform) opation on modulated input symbols X(k). 46
B. DVB-T System Physical Lay Intnational Journal for Research in Applied Science & Engineing Technology (IJRASET) ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com MPEG -2 Data, Audio & Video Signals Scramble r & Zo Padding Descrambl Encod (Reed Solomon ) Decode r (Reed Solomo Out Intleav Out Deintleav Convolutio nal Encod Vitbi Decod Inn Intleav Mapp (64, 28- QAM) OFDM 496- Point &F Fron t End Fig. Block diagram of the DVB-T System Physical Lay II. PROPOSED SLM AND PTS TECHNIQUES We propose SLM and PTS techniques for PAPR reduction of OFDM signals in DVB-T. A. Selective mapping (SLM) Technique B () X () Data Source Partition into Blocks & Sial to Parallel Convtor B (2) X () x X (2) X (2) Select One with Minimum PAPR x (Û) B (U) X (U) X (u) Fig.2 Block diagram of SLM technique The X(k) is the mapped sub symbol and X is the data block.whe k =,, 2,...N. The B (u) indicates the u th phase vector whe u =, 2,...U. Fig.2 shows, the block diagram of SLM technique. By using the set {±, ±j} phase sequences are genated randomly[6]. The X (u) is the u th candidate vector The equation (3) is used to obtain k th element of u th candidate vector. The U numb of altnative OFDM signals is genated using and it is obtained as (3) (4) The minimum PAPR value OFDM signal is selected for transmission. The selected OFDM signal is indicated as x ( u) (k). In SLM for genation of altnative OFDM symbols the independent phase vectors has to genated B (u) (k) is the k th value of u th phase vector and it is given by (5) Whe ϕ(k) or ϕ (u) (k) indicates the random phase value. The condition of mutual independence between b (m) (n) and b (l) (n) is 47
ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com ϕ must be uniformly distributed in [, 2π) to satisfy the above condition[7]. (6) B. Partial Transmit Sequence (PTS) Technique X Data Source Sial to Parallel Convto r& Partition into Blocks X 2 b b 2 X V b v Peak Pow Fig.3 Block diagram of PTS technique Fig.3 shows, the block diagram of PTS. The data information in frequency domain X is separated into V non-ovlapping sub blocks and the size N same for evy sub-block vectors [8] [9]. Assuming these sub-blocks has no gap between each oth; then the sub-block vector is (7) (8) φ v [,2π] and v = {,2..V}. Whe b v indicates the weighting factor utilized for phase rotation. On applying on Xv the time domain signal of X v. (9) Choose one suitable factor combination b = [b, b2,,bv] to achieve optimum result. The combination is given as () whe arg min ( ) is the decision condition that gives, the least value of function. By this way we can have the best b in ord to optimize the reduction of PAPR pformance. The additional cost, is required for extra V- times s opation[]. III. SIMULATION RESULTS AND DISCUSSIONS A. Simulation of SLM and PTS Techniques The simulation of SLM and PTS PAPR reduction techniques, are carried out using MATLAB tool. The input applied to OFDM DVB-T system model is Siblings, a bouncing ball animation_cut.avi video signals taken form intnet. The paramets varied in the simulations are given in Table I. simulation is carried out using 64-QAM and 28-QAM. 48
ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com ORIGINAL SIGNAL 2 4 6 8 c c d f.3.2 2 2 4 6 8 2. -2-2 3 4 5 6 7 8 PAPR(dB) Fig.4 Video frame of sibling, a bouncing ball animation_cut.avi Fig.5 PAPR of original signal for 64-QAM PTS technique SLM technique ccdf.3 cc df=pr(p APR>PAP R).3.2.2.. -6-4 -2 2 4 6 PAPR2(dB) Fig.6 PAPR using PTS technique for 64-QAM -4-2 2 4 6 8 PAPR3(dB) Fig.7 PAPR using SLM technique for 64-QAM ORIGINAL SLM PTS ccdf=pr(papr>papr).3.2. 5 5 2 25 PAPR(dB) Fig.8 comparison of PAPR using SLM and PTS techniques for 64-QAM with code rate is 3/4 49
ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com ORIGINAL SIGNAL PTS technique c c d f c c d f.3.3.2.2.. -4-2 2 4 6 8 PAPR(dB) -6-4 -2 2 4 6 PAPR2(dB) Fig.9 PAPR of original signal for 28-QAM Fig. PAPR using PTS for 28-QAM with code rate is 3/4 with code rate is 3/4 c c d f = p r( P A P R > P A P R ).3.2. SLM technique -6-4 -2 2 4 6 PAPR3(dB) Fig. PAPR using SLM techniques for 28-QAM Simulation Value Paramets No of sub carris N = 24 (N) numb of OFDM, 5, symbol No of sub blocks (M) M =2, 4, 8, 6, 32 sub-blocks Ovsampling factor L=4 (L) Phase factor (P) P=[ - j -j] Cyclic Prefix G = [/4,/8, /6, /32] Code rate /2, 2/3, 3/4 Modulation type 64-QAM and 28-QAM numb of OFDM C = 4 (for SLM) symbol candidate numb of OFDM C = 256 (for PTS) symbol candidate Table I Paramets used in MATLAB Simulation With code rate is 3/4 5
ISSN: 232-9653; IC Value: 45.98; SJ Impact Factor:6.887 Volume 5 Issue X, Novemb 27- Available at www.ijraset.com ORIGINAL SLM PTS ccdf=pr(papr>papr).3.2. 5 5 2 25 PAPR(dB) Fig. 2 comparison of PAPR using SLM and PTS techniques for 28 QAM with code rate is 3/4 The simulation results shown in Fig.5 through Fig.2 indicate that PTS technique achieves more PAPR reduction of OFDM signals than that of SLM technique for video signal input with 64-QAM and 28-QAM. IV. CONCLUSION AND FUTURE WORK In this research, we have successfully carried out the simulation of SLM and PTS techniques with input: video signal using MATLAB tool. PTS technique provides more PAPR reduction compared to SLM technique. In future work, SLM and PTS techniques are implemented on FPGA. REFERENCES [] Ladebusch UWE, C A. Liss Trestrial DVB-T: A Broadcast Tech. for Stationary Portable & Mobile Use Proc. of the IEEE, Volume-94, NO., pp. 83-93 Jan 26 [2] Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital trestrial TV, Final draft ETSI-EN 3 744 V.6. (28-9) European Standard (Telecommunications sies).[3] T.de. Couasnon. et al, OFDM for Digital Television Broadcasting, Signal Processing Vol. 39, pp.- 32, 994. [3] Nee, R. V. and R. Prasad, OFDM for Wireless Multimedia Communications, Artech House Publishs,, Jan 2 [4] S.G Pasha, V V Kohir, Pformance Analysis of PAPR Reduction Techniques for OFDM signals in DVB-T System, Intnational Journal of Emging Technologies & Innovative Research,ISSN-2349562, Vol No.4, issue:, Oct 27. [5] Tao Jiang, Yiyan Wu, An Ovview: Peak-to-Avage Pow Ratio Reduction Techniques for OFDM Signals IEEE Transactions on Broadcasting, VOL. 54, NO. 2, pp 257-268, june 28 [6] Bauml, R.W., Fisch, R.F.H., and Hub, J.B. Reducing the peak to avage pow ratio of multi carri modulation by selective mapping, IEEE Electronics Letts, Vol.32,Oct 996. [7] H. B. Jeon, J. S. No and D. J. Shin, A Low-Complexity SLM Scheme using Additive Mapping Sequences for PAPR Reduction of OFDM Signals, IEEE Transactions on Broadcasting, vol. 57, no. 4, (2), pp. 866-875. [8] S. H. Mull, J. B. Hub, OFDM with reduced peak-to-avage pow ratio by optimum combination of partial transmit sequence, IEEE Electronic Letts, Vol. 33, No. 5, Feb 997, pp. 368-369. [9] Leonard J. Cimini, Jr., Nelson R. Sollenbg, Peak-to-Avage pow ratio reduction of an OFDM signal using partial transmit sequences, IEEE Electronic Letts, vol. 4, no. 3, Mar 2, pp. 88-86. [] J. Hou, J. Ge, and J. Li, Peak-to-Avage Pow Ratio Reduction of OFDM Signals using PTS Scheme with Low Computational Complexity, IEEE Trans. Broadcast., vol. 57, no., (2), pp. 43 4 5
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