novel precoding based papr reduction schemes for localized ofdm uplink of lte-a

7/27/2019 Novel Precoding Based PAPR Reduction Schemes for Localized OFDM Uplink of LTE-A

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ISSN: 2180 - 1843 Vol. 2 No. 1 January - June 2010

Novel Precoding Based PAPR Reduction Schemes for Localized OFDMA Uplink of LTE-A

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Abstract

High Peak to Average Power Ratio (PAPR)reduction is still a major challenge in OrthogonalFrequency Division Multiple Access (OFDMA)systems. The subcarrier mapping in OFDMAcan be done in two modes, Localized mode andDistributed mode. The Localized mode is moresuitable for the practical implementations thanthe Distributed mode due to its low sensitivityagainst the imperfect power control, phasenoise and Inter Carrier Interference (ICI). Inthis paper, we propose two novel precodingbased Multi-Carrier (MC) Multiple Access(MA) techniques for PAPR reduction, Zado-Chu precoding based Localized-OFDMA(L-OFDMA) technique and GeneralizedChirp Like (GCL) precoding based L-OFDMAtechnique for L-OFDMA uplink systems of upcoming Long Term Evaluation-Advanced(LTE-A) system. These techniques are basedon precoding the constellation symbols withZado-Chu precoder and GCL precoder. The proposed techniques can reduce PAPR up to6.5dB for L-OFDMA. It is noticeable from thecomputer simulation results, that the PAPRof our proposed precoding based MC systemshave approximately equal PAPR as comparedto the PAPR of competing technology called

Localized Single Carrier Frequency Division Multiple Access SC-FDMA (LFDMA) system.LFDMA is implemented in release 8 of LongTerm Evaluation (LTE). Additionally, these precoding based PAPR reduction techniquesalso takes the advantage of the frequencyvariations of the communication channel andcan also oer substantial performance gain in fading multipath channels.

Keywords: PAPR, OFDMA, L-OFDMA,LTE-A, LFDMA, Zado-Chu Precoder, GCL

Precoder

Novel PrecodiNg Based PaPr reductioN schemes forlocalized ofdma uPliNk of lte-a

in B n vn J

Electrical and Electronic Engineering Department,Universiti Teknologi PETRONAS, Bandar Seri Iskandar,

31750 Tronoh, Perak, Malaysia.

[email protected], [email protected]

i. iNtroductioN

OFDMA is a multiple access versionof Orthogonal Frequency Division

Multiplexing (OFDM). OFDMA has been adopted as MA scheme by themost of the upcoming wireless andwireline digital communication systems

because of its high speed data rates, highspectral eciency, high quality serviceand robustness against narrow bandinterference and frequency selectivefading. The key dierence among OFDMand OFDMA is that instead of beingallocated all of the available subcarriers,

the base station assigns a subset of carriersto each user in order to accommodateseveral transmissions at the same time.

There are two dierent approaches to dosubcarrier mapping for uplink OFDMA,localized subcarrier mapping of OFDMAalso known as L-OFDMA where thesubcarrier mapping is done in adjacentand distributed subcarrier mapping ofOFDMA. Distributed subcarrier mapping

can be further divided in to two modesinterleaved OFDMA also known asI-OFDMA, where the subcarrier aremapped equidistant to each other’sand pure distributed OFDMA calledD-OFDMA, where subcarriers aredistributed randomly. To avoid the InterCarrier Interference (ICI) in the uplink dueto Doppler frequency shi, L-OFDMA ispreferred for practical implementationsthan that of I-OFDMA and D-OFDMA.

OFDMA thwarts Inter Symbol Interference(ISI) by inserting a Guard Interval (GI)using a Cyclic Prex (CP) and moderates




Journal of Telecommunication, Electronic and Computer Engineering

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the frequency selectivity of the Multi Path(MP) channel with a simple equalizer. Thisleads to cheap hardware implementationand makes simpler the design of thereceiver. OFDMA is widely adopted in

various communication standards likeWorldwide Interoperability for MicrowaveAccess (WiMAX), Mobile BroadbandWireless Access (MBWA), Evolved UMTSTerrestrial Radio Access (E-UTRA), UltraMobile Broadband (UMB), OFDMA isalso a strong candidate for the WirelessRegional Area Networks (WRAN) andLayered OFDMA of LTE-A [1]-[2] etc.

However OFDMA has some drawbacks,

among others, PAPR is still one of the majordrawbacks in the transmied OFDMAsignal. Therefore, for zero distortion ofthe OFDM signal, the HPA must notonly operate in its linear region but alsowith sucient back-o. Thus, HPA witha large dynamic range are required forOFDM systems. These ampliers are veryexpensive and are major cost componentof the OFDM system. Thus, if we reducethe PAPR it not only means that we are

reducing the cost of OFDM system andreducing the complexity of A/D andD/A converters, but also increasing thetransmit power, thus, for same rangeimproving received SNR, or for the sameSNR improving range.

A large number of PAPR reductiontechniques have been proposed in theliterature. Among them, schemes likeconstellation shaping [3], coding schemes

[4], nonlinear Companding transforms[5], Tone Reservation (TR) and ToneInjection (TI) [6, 7], clipping and ltering[8], Partial Transmit Sequence (PTS) [9],Selective Mapping (SLM) [10], precoding

based techniques [11, 12] and Precoding based Selective Mapping (SLM) [13, 14]are popular.

In [11] Authors proposed a Zado-Chuprecoding based single carrier system

with zero PAPR. It is shown that, bysuitably converting Zado-Chu sequenceinto a precoding matrix, it is possible todesign zero PAPR OFDM system. In [15]

H.G.Myung et.al, presented an excellentPAPR analysis of the SC-FDMA signalswith pulse shaping. They implementedraised cosine pulse shaping lter, throughcomputer simulations they concluded

that pulse shaping increases the PAPR.They compared their results with theOFDMA conventional and found thatSC-FDMA has lower PAPR because ofits single carrier structure than OFDMAconventional. They also compare thePAPR of Interleaved FDMA (IFDMA)and Localised FDMA (LFDMA) withand without pulse shaping. At the end,they conclude that IFDMA has lowerPAPR then LFDMA. In [16] Cristina et.al

presented an analysis of PAPR and BitError Rate (BER) of the OFDMA, WHTprecoding based OFDMA and SC-FDMAfor uplink communications. They showedthrough computer simulations, that 2dBPAPR gain is achieved when employedSC-FDMA against OFDMA, but nosignicant PAPR gain is achieved whenWHT precoded OFDMA is used againstOFDMA for uplink transmissions. Theyalso showed that, in the existence of

robust channel coding OFDMA shows beer BER performance, on the otherhand in the presence of less powerfulcoding both precoded OFDMA and SC-FDMA outperforms. At the end, theyalso concluded that SC-FDMA and WHTprecoding based OFDMA system hassimilar performance to on frequencyselective channels because their spreadingproperties recover frequency diversity.In [17] LTE-A requirements were agreed

but radio interface schemes are stilldebatable.

In this paper, we proposed two precoding based PAPR reduction schemes forL-OFDMA uplink system of LTE-A,Zado-Chu precoding based L-OFDMAuplink system and GCL precoding basedL-OFDMA. Extensive MATLAB(R)simulations have been performed forthe PAPR analysis of our both systems.

Additionally, we also compare ourMATLAB(R) simulation results withL-OFDMA, I-OFDMA, WHT Precoding

based L-OFDMA and SC-FDMA (LFDMA)





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iv. simulatioN results

Extensive simulations in MATLAB(R) have been performed in order to evaluate theperformance of our proposed systems,Zado-Chu precoding based L-OFDMAuplink system and GCL precoding basedL-OFDMA uplink system for LTE-A.

We also compared our computersimulation results with Interleaved-OFDMA original, Localized-OFDMAoriginal, SLM conventional, WHTprecoder based OFDMA system andLocalized SC-FDMA (without pulseshaping) for M=16 & 256 and N =64 & 1024for QPSK, 16-QAM and 64-QAM.

Figure.4 shows the CCDF comparisonsof Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-OFDMA System and GCL Precoder BasedLocalized-OFDMA System for M=16 andN=64 with QPSK modulation. At cliprate of 10-2 , the PAPR is reduced to 8.9dB,

8.3dB, 7.6dB, 7.0dB, 6.5dB and 6.5dB forL-OFDMA, I-OFDMA, WHT-PrecoderBased OFDMA System, Zado-ChuPrecoder Based Localized-OFDMA, GCL-Precoder Based Localized-OFDMA andSC-FDMA (LFDMA), respectively.

Figure 4. CCDF of L-OFDMA conventional,I-OFDMA conventional, WHT Precoder

Based OFDMA, Zado-Chu Precoder BasedL-OFDMA, GCL Precoder Based L-OFDMAand SC-FDMA (LFDMA) for QPSK.


Based OFDMA, Zado-Chu Precoder Based

L-OFDMA, GCL Precoder Based L-OFDMAand SC-FDMA (LFDMA) for 16-QAM.


Based OFDMA, Zado-Chu Precoder BasedL-OFDMA, GCL Precoder Based L-OFDMA

and SC-FDMA (LFDMA) for 64-QAM.

Figure.5 shows the CCDF comparisonsof Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-OFDMA System and GCL Precoder BasedLocalized-OFDMA System for M=16 andN=64 with 16-QAM modulation. At cliprate of 10-2 , the PAPR is reduced to 8.6dB,8.1dB, 7.8dB, 7.5dB, 7.1dB and 7.1dB forL-OFDMA, I-OFDMA, WHT-Precoder

Based OFDMA System, Zado-ChuPrecoder Based Localized-OFDMA, GCL-Precoder Based Localized-OFDMA andSC-FDMA (LFDMA), respectively.





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Figure.6 shows the CCDF comparisonsof Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-

OFDMA System and GCL Precoder BasedLocalized-OFDMA System for M=16 andN =64 with 64-QAM modulation. At cliprate of 10-2 , the PAPR is reduced to 8.5dB,8.0dB, 7.9dB, 7.7dB, 7.2dB and 7.2dB forL-OFDMA, I-OFDMA, WHT-PrecoderBased OFDMA System, Zado-ChuPrecoder Based Localized-OFDMA, GCL-Precoder Based Localized-OFDMA andSC-FDMA (LFDMA), respectively.

Figure.7 shows the CCDF comparisonsof Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-OFDMA System and GCL Precoder BasedLocalized-OFDMA System for M=256and N =1024 with QPSK modulation. Atclip rate of 10-2 , the PAPR is reduced to10.3dB, 9.9dB, 9.9dB, 8.0dB, 7.2dB and7.2dB for L-OFDMA, I-OFDMA, WHT-

Precoder Based OFDMA System, Zado-Chu Precoder Based Localized-OFDMA,GCL-Precoder Based Localized-OFDMAand SC-FDMA (LFDMA), respectively.

Figure.8 shows the CCDF comparisonsof Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-OFDMA System and GCL Precoder Based

Localized-OFDMA System for M=256 andN =1024 with 16-QAM modulation. Atclip rate of 10-2 , the PAPR is reduced to10.4dB, 10.0dB, 10.0dB, 8.8dB, 8.2dB and8.2dB for L-OFDMA, I-OFDMA, WHT-Precoder Based OFDMA System, Zado-Chu Precoder Based Localized-OFDMA,GCL-Precoder Based Localized-OFDMAand SC-FDMA (LFDMA), respectively.

Figure.9 shows the CCDF comparisons

of Localized-OFDMA, Interleaved-OFDMA, WHT Precoder Based OFDMASystem, SC-FDMA (Localized-FDMA),Zado-Chu Precoder Based Localized-

OFDMA System and GCL Precoder BasedLocalized-OFDMA System for M=256 andN=1024 with 64-QAM modulation. Atclip rate of 10-2 , the PAPR is reduced to10.4dB, 10.0dB, 10.0dB, 8.9dB, 8.3dB and

8.3dB for L-OFDMA, I-OFDMA, WHT-Precoder Based OFDMA System, Zado-Chu Precoder Based Localized-OFDMA,GCL-Precoder Based Localized-OFDMAand SC-FDMA (LFDMA), respectively.

The Table 1 & Table 2 summarizes thePAPR analysis of our proposed precoding

based L-OFDMA uplink system for theupcoming LTE-A 4G-cellular system. It isobvious from the tables that our proposed

Zado-Chu precoding based L-OFDMAuplink system and GCL precoding basedL-OFDMA uplink system have lowerPAPR then L-OFDMA original, I-OFDMAoriginal and WHT precoding basedL-OFDMA at clip rate of 10-2.



and SC-FDMA (LFDMA) for QPSK





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Based OFDMA, Zado-Chu Precoder Based

L-OFDMA, GCL Precoder Based L-OFDMAand SC-FDMA (LFDMA) for 16-QAM.



and SC-FDMA (LFDMA) for 64-QAM.

Table.1. At Ccdf Of 10-2 , PAPR Comparisons

Of LOFDMA, IOFDMA, SC-FDMA (LFDMA),ZADOFF-CHU LOFDMA And GCL-LOFDMAFor M=16 (User Subcarriers) & N =64 (System

Subcarriers)

Table.2. At Ccdf Of 10-2 , PAPR ComparisonsOf LOFDMA, IOFDMA, SC-FDMA (LFDMA),ZADOFF-CHU LOFDMA and GCL-LOFDMA

FOR M=256 (User Subcarriers) & N =1024(System Subcarriers)

It is also noticeable from the tables,that the PAPR of GCL precoding basedL-OFDMA uplink system has almost equalPAPR when we compare with SC-FDMA(LFDMA) system. Additionally, it is also

concluded from tables that PAPR gainof our both proposed precoding basedL-OFDMA uplink systems increases withincrease in the number of subcarriers.

v. coNclusioN

In this paper, we proposed two novelprecoding based PAPR reductiontechniques for L-OFDMA uplinksystem of LTE-A. These L-OFDMAMA techniques can be used as a MultiCarrier (MC) part of layered-OFDMA ofLTE-A. Tables shows that our proposedprecoding based schemes for L-OFDMAuplink system have lower PAPR ascompared to L-OFDMA, I-OFDMA andWHT precoder based L-OFDMA uplinksystems. It is also obvious from thetables that the both uplink systems, theGCL precoding based L-OFDMA uplink

system and the SC-FDMA (LFDMA)system has almost equal PAPR. Ourproposed precoding based techniquesare ecient, signal independent,distortionless and do not require anycomplex optimizations. Hence it isconcluded, that our proposed precoding

based PAPR reduction techniques forL-OFDMA uplink system can take benetsfrom the side, multicarrier system andsingle carrier system. It is also concluded

that our proposed precoding based PAPRreduction techniques for L-OFDMAuplink system can be considered as a bestchoice for the uplink communications ofthe upcoming LTE-A standard.





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refereNces

[1] 3GPP, TS36.201 (V8.1.0), “LTE physicallayer – general description (Release8),” Nov. 2007.

[2] Motohiro Tanno, Yoshihisa Kishiyama,Hidekazu Taoka, Nobuhiko Miki,Kenichi Higuchi, Mamoru Sawahashi,” Layered OFDMA Radio Access forIMT-Advanced”, In Proceedings of the68th IEEE VTC, 21-24 September 2008,Calgary, Alberta, Canada.

[3] Yajun Kou, Wu-Sheng Lu and AndreasAntoniou, “A new peak-to-averagepower-ratio reduction algorithmfor OFDM systems via constellationextension”, IEEE Trans. Wireless

Communications, vol. 6, no. 5, pp.1823–1832, May 2007.

[4] S.Ben Slimane, “Reducing the peak-to-average power ratio of OFDM signalsthrough precoding”, IEEE Trans.Vehicular Technology, vol. 56, no. 2, pp.686–695, Mar. 2007.

[5] Tao Jiang, Wenbing Yao, Peng Guo,Yonghua Song and Daiming Qu, “Twonovel nonlinear Companding schemeswith iterative receiver to reduce PAPRin multicarrier odulation systems”,IEEE Trans. Broadcasting, vol. 52, no. 2,pp. 268–273, Mar. 2006.

[6] J.Tellado-Mourelo, “Peak to AveragePower Ratio Reduction for MulticarrierModulation”, PhD thesis, University ofStanford, Stanford, 1999.

[7] Seungsoo Yoo, Seokho Yoon, S.YongKim, and Iickho Song, “A novel PAPRreduction scheme for OFDM systems:

Selective mapping of partial tones(SMOPT)”, IEEE Trans. ConsumerElectronics, vol. 52, no. 1, pp.40–43,Feb. 2006.

[8] Luqing Wang and Chintha Tellambura ,”A Simplied Clipping and FilteringTechnique for PAR Reduction in OFDMSystems”, Signal Processing Leers,IEEE , vol.12, no.6, pp. 453-456, June2005.

[9] S.Hee Han and J.Hong Lee, “PAPR

Reduction of OFDM Signals Using aReduced Complexity PTS Technique”,Signal Processing Leers, IEEE, Vol.11,Iss.11, Nov. 2004, Pages: 887- 890.

[10] Robert Bäuml, Robert F. H. Fischerand Johannes B. Huber, “Reducingthe Peak-to-Average Power Ratio ofMulticarrier Modulation by SelectedMapping,” Elect. Leers. vol. 32, no.22, Oct. 1996.

[11] Varun Jeoti and Imran Baig, “ZeroPAPR Zado-Chu Precoder BasedTechnique for SC-FDMA”, invitedpaper, Proceedings of 2009 IEEEInternational Conference on Antennas,Propagation and Systems (INAS 2009),3-5 Dec. 2009, Johor, Malaysia.

[12] Imran Baig and Varun Jeoti, “PAPRAnalysis of DHT-Precoded OFDMSystem for M-QAM”, The 3rdInternational Conference on Intelligent

& Advanced Systems (ICIAS2010) June 15 to June 17, 2010, Kuala lumpur,Malaysia.

[13] Varun Jeoti and Imran Baig, “A NovelZado-Chu Precoder Based SLMTechnique for PAPR Reduction inOFDM Systems ”, invited paper,Proceedings of 2009 IEEE InternationalConference on Antennas, Propagationand Systems (INAS 2009), 3-5 Dec.2009, Johor, Malaysia.

[14] Imran Baig and Varun Jeoti, “DCTPrecoded SLM Technique for PAPRReduction in OFDM Systems”, The 3rdInternational Conference on Intelligent& Advanced Systems (ICIAS2010) June 15 to June 17, 2010, Kuala lumpur,Malaysia.

[15] Hyung. G. Myung, Junsung Limand David J. Goodman, “Peak-To-Average Power Ratio of Single CarrierFDMA Signals with Pulse Shaping,”

Personal, Indoor and Mobile RadioCommunications, 2006 IEEE 17thInternational Symposium on , vol., no.,pp.1-5, 11-14 Sept. 2006.

[16] Cristina. C, David.M and Hikmet.S,“An Analysis of OFDMA, PrecodedOfdma and SC-FDMA for the Uplinkin Cellular Systems”, 6th InternationalWorkshop on Multi-Carrier SpreadSpectrum, May 2007, Herrsching,Germany.

[17] 3GPP, TR36.913 (V8.0.0), ”Requirementsfor further advancements forE-UTRA(LTE-Advanced)”, June 2008





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[18] D.C. Chu, “Polyphase codes with goodperiodic correlation properties”, IEEETrans. Inform. Theory, vol. IT-18, pp.531-532, July 1972.

[19] Branislav M. Popovid, “Generalized

chirp-like polyphase sequences withoptimum correlation properties”, IEEETransactions on Information Theory 38(4) (1992), pp. 1406–1409.

novel precoding based papr reduction schemes for localized ofdm uplink of lte-a

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