Dft-spread Ofdm

Initial Performance Evaluation of DFT-SpreadOFDM Based SC-FDMA for UTRA LTE Uplink

Basuki E. Priyanto, Humbert Codina, Sergi Rene, Troels B. Sørensen, Preben MogensenDepartment of Electronic Systems, Aalborg UniversityNiels Jernes Vej 12, DK-9220 Aalborg East, Denmark

Email: {bep, humbert, srene, tbs, pm}@es.aau.dk

Abstract—In this paper we present an initial performanceevaluation of the 3GPP UTRA Long Term Evolution (UTRALTE) uplink with baseline settings. The performance resultsare obtained from a detailed UTRA LTE uplink link levelsimulator supporting OFDMA and SC-FDMA schemes. The basictransmission scheme for uplink direction is based on single-carrier transmission in the form of DFT Spread OFDM withan MMSE receiver. Two antenna configurations, SISO and 1x2SIMO are considered in the analysis of spectral efficiency inaddition to Adaptive Modulation and Coding (AMC) and L1-HARQ. For assessment purposes, the performance results ofSC-FDMA are compared with OFDMA. It is shown that 1x2SIMO greatly increases the spectral efficiency of SC-FDMAmaking it comparable to OFDMA, especially for high codingrate. Furthermore, SC-FDMA has a flexibility to increase BLERperformance by exploiting frequency diversity.

Index Terms - OFDM, SC-FDMA, Uplink, UTRA LTE

I. INTRODUCTION

UTRA Long Term Evolution (LTE) is the next generationof wireless cellular communication systems, which is designedas a step towards the 4G systems. The 3GPP has initiateda study item on UTRA LTE [1] targeting release 8 of theUTRA specifications. The objective of this study item is todevelop a framework for the evolution of the 3GPP radio-access technology towards a high data rate, low-latency, andpacket optimized radio access technology [2]. UTRA LTEsupports scalable bandwidth from 1.25 MHz to 20 MHz inorder to meet the future mobile services requirements. Uplinkdirection of UTRA LTE has the target to increase 2 to 3 timesthe user throughput of Release 6 High-Speed Uplink PacketAccess (HSUPA) and thus achieve a maximum data rate of 50Mbits/s by using the full 20 MHz bandwith. User mobility upto 350 km/h and coverage up to 30 km are also targeted [2],[3].

Orthogonal Frequency Division Multiple-Access (OFDMA)has been selected as the multiple access scheme for downlinkin the UTRA LTE and Single-Carrier Frequency DivisionMultiple-Access (SC-FDMA) for uplink. OFDM is recognizedas an attractive modulation technique in a cellular environ-ment, because of its capability to enable low-complexitymultipath channel mitigation. Nevertheless, OFDM requiresan expensive and inefficient power amplifier in the transmitterbecause of the high Peak-to-Average Power Ratio (PAPR)of the multi-carrier signal. Single Carrier transmission withCyclic Prefix (SC-CP) is a closely related transmission scheme

with the same attractive multipath interference mitigationproperty as OFDM [4], [5], [6]. Therefore, SC-CP can achievea performance comparable to OFDM for the same complexity,but at reduced PAPR. In addition, the performance of SC-FDMA can be further improved by using a turbo equalizationreceiver [7]. The choice of single carrier transmission in aDFT-Spread OFDM form allows for a relatively high degreeof commonality with the downlink OFDM scheme and thepossibility to use the same system parameters [1].

Multiple antennas are essential for UTRA LTE in order toreach the targeted peak data rates. In particular, with the aimof improving the performance at the lower SNR operatingrange. In this paper we study the combination of SC-FDMAwith single-input single-output (SISO) and the single-inputmultiple-output (SIMO) antenna configurations; in LTE, thebaseline for uplink is to use one transmit antenna at the UE [2],[3] and two receive antennas with Maximal Ratio Combining(MRC) at the base station. Overall, we aim at presentingan initial performance evaluation of SC-FDMA with MMSEreceiver, and at comparing the single-carrier performance tothat provided by the multi-carrier OFDMA transmission.

The paper starts with an introduction of the basic principlesof DFT spread OFDM single-carrier transmission in SectionII. We then describe shortly, in Section III, the link level toolused for performance investigation. The tool has been a naturaldevelopment of an earlier LTE downlink link level simulator[8], since there are many common components between uplinkand downlink. In Section IV we present and analyse the SC-FDMA link level results in comparison with similarly obtainedresults for OFDMA. Particularly, we discuss the effect of L1-HARQ and sub-carrier allocation in SC-FDMA. Finally, theconclusions are presented in Section V.

II. DFT-SPREAD OFDM

The basic uplink transmission technique is single-carriertransmission (SC-FDMA) with cyclic prefix to achieve uplinkinter-user orthogonality and to enable efficient frequency-domain equalization at the receiver side. DFT-Spread OFDM(DFT-S OFDM) is a form of the single-carrier transmissiontechnique where the signal is generated in frequency-domain.

The mth transmitted symbol in a DFT-S OFDM systemwithout cyclic prefix in SISO case can be expressed as a vectorof length Ng samples, defined by:

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sm = Fm · Tm · Dm · xm (1)

where xm is a vector with M QAM or PSK modulatedsymbols, Dm is a matrix which performs an M points DiscreteFourier Transform (DFT) operation, Tm is the N × Mmapping matrix for subcarrier assignment, and Fm performsan N points Inverse Fast Fourier Transform (IFFT) operation.

After the multipath channel and adding the additive whitegaussian noise (AWGN), removing the cyclic prefix and goingthrough the N points FFT, the received signal vector in thefrequency domain can be expressed as:

zm = Hm · Tm · Dm · xm + wm (2)

where Hm is the diagonal matrix of channel response, andwm is the noise vector. Note that the maximum excess delay ofthe channel is assumed shorter than the cyclic prefix durationand, therefore, the inter-symbol interference (ISI) can easilybe eliminated by removing the cyclic prefix.

The amplitude and phase distortion in the received signaldue to the multipath channel is compensated by a frequencydomain equalizer (FDE), and the signal in the FDE output is:

Vm = Cm · zm (3)

where Cm is the matrix diagonal of FDE coefficients Cm =diag(Cm,1, Cm,2, . . . , Cm,N ). The FDE complex coefficient,Cm,k can be obtained under the minimum mean-square error(MMSE) criterion. It is given by [13]:

Cm,k =H∗

m,k

|Hm,k|2 + σ2n

σ2s

(4)

where k denotes the subcarrier index, σ2n the variance of

the additive noise, and σ2s is the variance of the transmitted

pilot symbol. After performing the sub-carrier demappingand IDFT despreading, x̂m, a vector with M QAM or PSKmodulated symbols can be obtained at the receiver. The IDFTdespreading block in the receiver averages the noise in eachsubcarrier. A particular subcarrier may experience deep fadingin a frequency selective fading channel. IDFT despreadingaverages and spreads the deep fading effect, which results in anoise enhancement to all the QAM symbols. Hence, the IDFTdespreading makes DFT-S OFDM more sensitive to the noise.

III. UTRA LTE UPLINK SIMULATOR

A detailed DFT-S OFDM transmitter and receiver blockdiagram is depicted in Fig.1. As shown, the left side isthe transmitter, corresponding to the user equipment (UE),and the right side is the receiver, corresponding to the basestation (BS). UTRA LTE uplink uses link adaptation, and themechanism is as follows: It selects a transport format andresource combination (TFRC) for transmission on the basis ofchannel quality indication (CQI) measurement from the BS.The TFRC decision is passed to the Transport Block Generatorwhich generates a packet of the requested size. Then followedby cyclic redundancy check (CRC) encoding. According to

Transport block generator

CRC attachment

Code block segmentation

Channel Coding

L1-HARQ & Rate Matching

Interleaver

QAM/PSKConstellation

Mapping

DFT-Spreading

Sub-carrier Mapping

IFFT & CP Insertion

BER & BLERMeasurement

CRC verifications

Code block desegmentation

Channel Decoding

L1-HARQ & de-Rate Matching

Deinterleaver

QAM/PSKConstellationDemapping

IDFT-Despreading

FFT & CP removal

MultipathChannel

UE Base stationInput

from LA

MMSEEqualizer

Sub-carrierDemapping

Fig. 1. L1 UTRA LTE uplink link level simulator.

the packet size and the maximum code block size, the packetis divided into several blocks before being fed to the channelencoder. The coding used for this study is the turbo codingdefined in the UTRA Release 6. Next, the rate matching blockadjusts the output bit rate according to the requirements bypuncturing or repeating the coded bits. The output bits areinterleaved in order to break its correlation and are passed tothe modulator. The implemented modulator works with QAMand PSK constellations used in the UTRA LTE uplink: pi/2BPSK, QPSK, 8PSK and 16QAM [1]. For QAM modulation,a QAM remapping is performed to put the systematic bits atmore reliable constellation points as this improves the decoderperformance.

The DFT spreading responsible for generating the singlecarrier transmission, is applied after the QAM/PSK modulator.The DFT spreading block spreads the data symbols betweenall the available subcarriers. Afterwards, data symbols arecombined with pilot symbols in a time division multiplexing(TDM) fashion and mapped to the proper subcarriers. Thecurrent implementation allows both localized and distributedallocation mapping. Distributed case is used to gain frequencydiversity, whereas the localized SC-FDMA can be used tosimplify subcarrier allocation and the scheduling. Finally,

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the basic OFDM processing is performed. The data symbolsare placed on orthogonal subcarriers by the IFFT and theaddition of cyclic prefix. At the receiver side, the BS basicallyperforms the reverse operations with a linear MMSE receiver.The MMSE receiver is selected in order to minimize noiseenhancement on frequency selective fading channel.

The generated signal is transmitted over a multipath channelbased on the implementation in [10]. It uses the correlation-based stochastic MIMO model. To ensure that the correlationproperties in the frequency domain are realistic, the typicalurban with power delay profile (PDP) six paths is assumed [1].For the SIMO case, antennas are assumed to be uncorrelated.The path loss, shadowing, and other cell noise is modeled asAWGN noise.

Several throughput enhancement mechanisms are imple-mented, including adaptive modulation coding (AMC) basedon link adaptation (LA) and Hybrid ARQ (HARQ) basedon fast L1 retransmissions. The HARQ is based on chasecombining (CC) and incremental redundancy (IR). LA withvarious modulation and channel coding sets (MCS) is appliedto the shared data channel. Here, a simple LA is assumedin which the MCS selection is based on averaged SNR. Wedo not expect the throughput performance to differ a lotfrom the instantaneous LA case since the bandwidth assumedfor our studies is very large, and the channel profile ishighly frequency selective. This approach is validated in thelater section. No errors are assumed in the transmission ofACK/NACK messages. The channel estimation is assumed tobe ideal. Due to the short retransmission delays, it is possibleto operate at a 1st transmission block error rate (BLER) valuesof around 10-30%. A retransmission scheme based on the stopand wait (SAW) principle with several independent HARQprocesses per user is assumed [12].

IV. SIMULATION RESULTS

The simulation results are obtained through the Monte-Carlo simulation using the predescribed simulator. The mainparameter settings are listed in Table I. Most of the simulationsare using 10 MHz system bandwidth with 600 useful subcar-riers. In the study of subcarrier allocation for SC-FDMA, 150useful subcarriers are used in 10 MHz system bandwidth tomultiplex 4 users. The idea is to allow subcarrier spreadingin the distributed case with a repetition factor of 4. Onesub-frame in uplink consists of 6 long blocks (LBs) and 2short blocks (SBs) [1]. LBs are used for data transmission,whereas SBs are used for reference signals for coherentdemodulation and/or control/data transmission. In this sub-frame structure, the SBs introduce an overhead of around14%. The OFDMA scheme is also evaluated by disabling thespreading/despreading components, and the main parametersare listed in Table I.

Fig. 2 shows the CDF of the measured instantaneous SNRfor both SISO and SIMO at different average input SNRvalues: 0 dB, 10 dB, and 20 dB. The instantaneous SNRis measured after the equalization and IDFT despreadingprocess. It can be seen that for all cases, the dynamic range of

TABLE IUTRA LTE UPLINK SIMULATION PARAMETERS.

Parameter Value

Carrier Frequency 2 GHzTransmission BW 10 MHzSub-frame duration 0.5 msSub-carrier spacing 15 kHzSC-FDM symbolsper sub-frame 6 LBs, 2 SBsCP duration 4.1 µsFFT size/Useful subcarriers 1024/600MCS settings pi/2 BPSK: 1/6, 1/3

QPSK: 1/2, 2/3, 3/48PSK: 1/3, 1/2, 2/3, 3/416QAM: 1/2, 2/3, 3/4, 4/5

Channel code 3GPP Rel. 6 compliant Turbo codewith basic rate 1/3

Rate Matching, Interleaver 3GPP Rel. 6 compliantChannel Estimation IdealAntenna schemes SISO, SIMOChannel model Typical Urban 6 paths [1]Speed 3 kmphHARQ Chase Combining,

Incremental RedundancyHARQ SAW channels 6HARQ Max No. of transmission 4

−5 0 5 10 15 20 25 300

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Instantaneous SNR (dB)

CD

F

SISO, 0 dBSIMO, 0 dBSISO, 10 dBSIMO, 10 dBSISO, 20 dBSIMO, 20 dB

Fig. 2. CDF of measured instantaneous SNR of SC-FDMA.

instantaneous SNR is very limited due to a large bandwidthand a given channel profile. It implies that the selectionof modulation and coding is almost constant for a givenaverage SNR, and the simple LA model used here is valid.The dynamic range for low SNR is further reduced becauseof the advantage of using MMSE receiver. At high SNR,the instantaneous SNR dynamic range increases because ata high SNR, the MMSE receiver becomes identical to thezero forcing (ZF) receiver. The results are also shown that thenoise enhancement loss increases with the average input SNR,especially for SISO case[4].

The spectral efficiency of different modulation and codingsets (MCS) in 1x2 SIMO case without HARQ is plotted versusaverage SNR and shown in Fig. 3. Variable-rate turbo encodingand modulation from pi/2 BPSK to 16QAM provide peak data

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TABLE IIPEAK DATA RATE FOR 10 MHZ SYSTEM

MCS Data Rate

pi/2 BPSK 1/6 1.2 Mbps

pi/2 BPSK 1/3 2.4 Mbps

QPSK 1/2 8PSK 1/3 7.2 Mbps

QPSK 2/3, 9.6 Mbps

QPSK 3/4, 8PSK 1/2 10.8 Mbps

16QAM 1/2, 8PSK 2/3 14.4 Mbps

8PSK 3/4 16.2 Mbps

16QAM 2/3 19.2 Mbps

16QAM 3/4 21.6 Mbps

16QAM 4/5 23 Mbps

−10 −5 0 5 10 15 200

0.5

1

1.5

2

2.5

Average SNR (dB)

Spe

ctra

l effi

cien

cy (

b/se

c/H

z)

pi/2 BPSK 1/6pi/2 BPSK 1/3QPSK 1/2QPSK 2/3QPSK 3/48PSK 1/38PSK 1/28PSK 2/38PSK 3/416QAM 1/216QAM 2/316QAM 3/416QAM 4/5LA w/o HARQLA HARQ

Fig. 3. Spectral Efficiency of 1x2 SIMO SC-FDMA with and without HARQ.

rates from 1.2 Mbps up to 23 Mbps for the system with 10MHz bandwidth. Note that the 14% pilot overhead has beentaken into account. Selected MCS formats and correspondingdata rate values are summarized in Table II. It can be observedthat 8PSK does not contribute to the link adaptation (LA)curve.

The effect of HARQ can be observed in Fig.3 where HARQChase Combining is used for coding rates equal to or smallerthan 1/2, and HARQ Incremental Redundancy is used forcoding rates higher than 1/2. The combining gain of HARQcan be observed in the smoothning out of the LA curve. Theusage of pi/2 BPSK and HARQ enhances the UE throughputat the cell edge.

In Fig. 4, the spectral efficiency for both SISO and SIMOantenna schemes is presented. The spectral efficiency ofOFDMA is also presented for comparison purposes. For theSISO case, OFDMA outperforms SC-FDMA with an MMSEreceiver. The demodulation for OFDMA is performed infrequency domain, whereas for SC-FDMA, demodulation isperformed in time domain, and its signal is an average ofthese before IDFT despreading. A deep fading may affect the

−10 −5 0 5 10 15 20 25 300

0.5

1

1.5

2

2.5

Average SNR (dB)

Spe

ctra

l effi

cien

cy (

b/se

c/H

z)

LA SISO−SCFDMALA SISO−OFDMALA SIMO−SCFDMALA SIMO−OFDMA

Fig. 4. Spectral Efficiency for SC-FDMA and OFDMA with two antennaconfigurations (SISO and SIMO).

whole data symbol in SC-FDMA. Thus, the performance ofSC-FDMA is worse for frequency-selective fading channel.For the SIMO case, the SC-FDMA and OFDMA performancecan be improved due to the 3dB array and diversity gain.The spectral efficiency gap between OFDMA and SC-FDMAis unnoticeable for the SIMO case. The MMSE receiver inSIMO with maximum ratio combining (MRC) further reducesthe noise compared to the SISO case. The result also impliesthat using SIMO antenna scheme greatly increases the spectralefficiency of SC-FDMA.

Fig. 5 presents the block error rate (BLER) performance forSC-FDMA and OFDMA with HARQ in the SIMO case. Thepurpose is to provide detailed performance analysis for eachMCS scheme in SC-FDMA and OFDMA. It can be observedthat the performance of OFDMA is generally better than thatof SC-FDMA with the MMSE receiver. It can be noticed thatincreasing the coding rate reduces the OFDMA performance.With 16QAM rate 1/2, OFDMA has up to 0.6 dB gain overSC-FDMA. For the same 16QAM modulation, it can be seenthat at a code rate of 4/5, OFDMA and SC-FDMA have equalBLER performance. For QPSK rate 3/4, SC-FDMA has 0.5dB gain over OFDMA. Hence, the performance of OFDMA infrequency selective fading channel is more sensitive to codingthan SC-FDMA.

Fig. 5 also shows the HARQ effect. HARQ IncrementalRedundancy increases the performance for both OFDMA andSC-FDMA, especially for high BLER (≥ 50%). It can beobserved that 16QAM rate 2/3 and 4/5 perform better than16QAM rate 1/2 with HARQ Chase Combining. This isdue to the slower decay of the BLER curves when HARQIncremental Redundancy is selected.

The BLER performance of distributed and localized casein SC-FDMA with HARQ is presented in Fig. 6. The SIMOcase is assumed, and the channel bandwidth is 10 MHz. Only2.5 MHz bandwidth is allocated for the transmission. Fordistributed case, this configuration will allow a repetition factor

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−10 −8 −6 −4 −2 0 2 4 6 8 10 12 1410

−2

10−1

100

Average SNR (dB)

Blo

ck E

rror

Rat

e

QPSK 1/2,CC SCFDMAQPSK 1/2,CC OFDMAQPSK 3/4,IR SCFDMAQPSK 3/4,IR OFDMA16QAM 1/2,CC SCFDMA16QAM 1/2,CC OFDMA16QAM 2/3,IR SCFDMA16QAM 2/3,IR OFDMA16QAM 4/5,IR SCFDMA16QAM 4/5,IR OFDMA

Fig. 5. SC-FDMA versus OFDMA for various modulation and coding sets.

−4 −2 0 2 4 6 8 10 12 14 16 18

10−2

10−1

Average SNR (dB)

Blo

ck E

rror

Rat

e

QPSK 1/2 CC DistQPSK 1/2 CC LocQPSK 3/4 IR DistQPSK 3/4 IR Loc16QAM 1/2 CC Dist16QAM 1/2 CC Loc16QAM 2/3 IR Dist16QAM 2/3 IR Loc16QAM 4/5 IR Dist16QAM 4/5 IR Loc

Fig. 6. BLER performance of Distributed versus Localized in SC-FDMA.

of 4 since all of the subcarrier carrying data are distributed overthe full 10 MHz channel. It is shown that distributed performsbetter than localized in most cases. For BLER 1%, it is clearthat the distributed case is superior to localized. It has around1 dB gain over localized in 16QAM rate 4/5. The distributedcase can maximize the frequency diversity by distributing thedata in the whole bandwidth. In the real situation, when realchannel estimation is taken into account, localized is expectedto perform better than distributed. The reason is that thedistributed has to estimate the channel transfer function inthe full bandwidth, whereas localized estimates the channeltransfer function only in the allocated channel bandwidth. Thelocalized case with frequency hopping can also be consideredinstead of distributed case because it can exploit frequencydiversity gain.

V. CONCLUSION

In this paper, we have demonstrated the benefits for SC-FDMA as the multiple access scheme in UTRA LTE up-

link. The performance results are obtained from a detailedUTRA LTE uplink link level simulator. Most of the UTRALTE features are considered in the simulator, including turbocoding, rate matching, interleaving, adaptive modulation andcoding, and fast L1 HARQ retransmissions. Two antennaconfigurations, SISO and 1x2 SIMO, are also studied. Thepeak spectral efficiency considering 14% pilot overhead is2.3 bps/Hz. Thus, a peak data rate of 23 Mbps can beachieved in 10 MHz system. Simulation results show that 1x2SIMO greatly increases the spectral efficiency of SC-FDMAmaking the performance of SC-FDMA with MMSE receivercomparable to OFDMA, especially for high coding rate. DFT-S OFDMA allows a flexible subcarrier allocation. In the idealchannel estimation case, the results indicate that distributedallocation is superior to localized due to link level frequencydiversity gain. For the future work, a turbo equalizer for DFT-S OFDMA is expected to enhance the overall performanceand making SC-FDMA superior to OFDMA in UTRA LTEuplink.

ACKNOWLEDGMENT

The authors wish to thank Akhilesh Pokhariyal and Na Weifor their helpful comments and fruitful discussions.

REFERENCES

[1] 3GPP TR 25.814 V1.4.0 (2006-05), ”Physical Layer Aspects for EvolvedUTRA”.

[2] 3GPP TR 25.913 V7.3.0 (2006-03), ”Requirements for Evolved UTRA(E-UTRA) and Evolved UTRAN (E-UTRAN)”.

[3] H. Holma and A. Toskala, Eds., HSDPA/HSUPA for UMTS, Radio Ac-cess For Third Generation Mobile Communications, Wiley, Chichester,UK, second edition, 2006.

[4] D. Falconer, S.L. Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson,”Frequency domain equalization for single-carrier broadband wirelesssystems,” IEEE Commun. Mag., vol. 40, no. 4, pp. 5866, Apr. 2002.

[5] H. Sari, G. Karam, and I. Jeanclaude, ”Transmission Techniques forDigital Terrestrial TV broadcasting,” IEEE Commun. Mag., vol. 33, no.2, pp. 100109, Feb. 1995.

[6] A. Czylwik, ”Comparison between adaptive OFDM and single carriermodulation with frequency domain equalization,” in Proc. VTC’97Phoenix, AZ, vol. 2, May 1997, pp. 865-869.

[7] K. Kansanen, ”Wireless Broadband Single-Carrier Systems with MMSETurbo Equalization Receivers,” PhD Thesis, University of Oulu, Oulu,Finland, 2005.

[8] N. Wei, A. Pokhariyal, C. Rom, B.E. Priyanto, F. Frederiksen, C.Rosa, T.B. Srensen, T.E. Kolding, P.E. Mogensen, ”Baseline E-UTRADownlink Spectral Efficiency Evaluation,” in Proc. IEEE VTC Fall 2006,Sept. 2006.

[9] A. Toskala, P. Mogensen, ”UTRAN Long Term Evolution in 3GPP,” inProc Eigth Intl. Symp. on Wireless Personal Multimedia Communica-tions (WPMC), Aalborg, Denmark, 2005.

[10] L. Schumacher, J. P. Kermoal, F. Frederiksen, K. I. Pedersen, A. Algansand P. E. Mogensen, ”MIMO Channel Characterisation,” IST ProjectIST- 1999-11729 METRA Deliverable 2, Feb. 2001.

[11] 3GPP TR 25.943, ”Deployment aspects”.[12] T. E. Kolding, F. Frederiksen, P. E. Mogensen, ”Performance aspects of

WCDMA systems with High Speed Downlink Packet Access (HSDPA),”in Proc. VTC Fall 2002, July, 2002.

[13] H. Sari, G. Karam, and I. Jeanclaude, ”Frequency-domain equalizationof mobile radio and terrestrial broadcast channels,” in Proc. IEEE GlobalTelecommun. Conf., vol. 1, Nov. 1994.

[14] H. Witschnig, R. Weigel, ”Decision feedback equalization in the contextof enhanced high rate mobile communications systems - based on theconcept of SC/FDE,” In 15th IEEE Int. Symposium on PIMRC 2004,vol.1, no.pp. 479-483, Sept. 2004.

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Dft-spread Ofdm