5g Waveform Comparative Study Below 6ghz Ktenas Cea Leti

Comparative study of 5G waveformcandidates for below 6GHz air interface

Dimitri Ktenas

R. Gerzaguet & D. Ktenas & N. Cassiau & J-B. Dore

CEA-Leti

01/28/2016

Table of Contents

1. Context and issues2. Waveforms2.1 CP-OFDM & SC-FDMA2.2 Filter bank multicarrier (FBMC)2.3 Universal Filtered Multicarrier (UFMC)2.4 Generalized Frequency Division Multiplexing

(GFDM)3. Comparizon between waveforms4. Multi-user access scenario5. Conclusion

5G ContextI 4G massively rolled out but will soon reaches its limits

I RAN 5G Workshop 09/15 : New non backward compatible Radio AccessTechnology as part of 5G

I Aggregation of non contiguous network is consideredI Spectrum agility : need to study alternative multicarrier waveforms

I Sporadic access & MTCI Strong traffic overhead (fast dormancy)I Massive number of devices : Use relaxed synchronism

I Several candidates have been independently introduced in the past few yearsI Classic CP-OFDM shows its limits : Spectral efficiency, frequency leakage, need

of tight synchronisationI We propose a comparative study of 5G waveform candidates for below

6GHz air interface

ETSI presentation Dimitri Ktenas 01/28/2016 3 - 16

Context and objectives

Considering several candidates for 5G physical layerI Baseline for comparison : OFDM and SC-FDMAI Filter bank multicarrier (FBMC) [3]I Universal Filtered Multicarrier : UFMC (or UF-OFDM) [9]I Generalized Frequency Division Multiplexing (GFDM) [6]

A fair comparison between waveforms in literature is lacking

Considering several metrics for comparisonI Spectral Efficiency (SE)I Peak To Average Power Ratio (PAPR)I Power spectral Density (PSD)

Also consider the asynchronous multi-user scenario [1, 11]


CP-OFDM & SC-FDMA

Modulateddata

stream

Serialto

parallel

DFT& pilot

insertionIFFT

Parallelto

Serial

CPInsertion

ak

x(n)

Basebandto RF Channel

RF tobaseband

CPremoval

Serialto

ParallelFFT

CHEST&

Equa.IDFT

Parallelto

serial

modulateddecodedstream

OFDM & SC-FDMA (additional stages in dash) transceiver scheme

I Multicarrier modulations, serves as physical layers for 3GPP-LTE or802.11.a/g/n

I Efficient implementation (IFFT/FFT), simple equalization schemesI Spectral efficiency loss due to Cyclic Prefix (CP) insertion to handle

multipath channelI For SC-FDMA : DFT/IDFT precoding stages to reduce PAPR (3GPP-LTE

uplink : DFT-spread OFDM)


Filter bank multicarrier (FBMC)I Set of parallel data through bank of modulated filters

I Good spectral location,orthogonality and spectralefficiency kept with OQAMmodulation

I Prototype filter in frequencydomain (FS) [2]

I Overlapping factor KI Filter defined in frequency

domain (K=4)H0 = 1H1 = H1 = 0.971960

H2 = H2 =22

H3 = H3 =1H21

Modulateddata stream

S/P

OQAMmodu-lation

Spreading Frequency

filteringIFFT Overlapand sum

FBMC Tx stage

CP-OFDM (top) and FBMC(bottom) frames


Universal Filtered Multicarrier (UFMC)

I Derivative of OFDM wherea group of subcarriers (RB)is filtered with aDolph-Chebyshev filter withlength L and attenuationfactor [9]

I B subbands are generatedand combined

I On Rx side, Zero padding isapplied before a 2N FFT

I Possibility to add awindowing process on theRx side (asynchronousmulti-user scenario)

+xk

Modulateddatastream

Serialto

parallel

IDFTspreader& PS

FilterF1k withlength L

a1kx1k

Modulateddatastream

Serialto

parallel

IDFTspreader& PS

FilterF2k withlength L

a2kx2k

Modulateddatastream

Serialto

parallel

IDFTspreader& PS

FilterFBk withlength L

aBkxBk

Basebandto RF

Channel

RF tobaseband

Windowing& Serialto parallel2 NFFT

pointsFFT

Zero padding

FrequencyDomainprocessing(subcarrier

equ.)

UFMC transceiver


Generalized Frequency Division Multiplexing (GFDM)I Based on time-frequency

filtering of data blocks of sizeP M

I Shaping filter : Root RaisedCosine filter (RRC)

I Non orthogonal waveform :interference in time andfrequency domains

I A CP is added at eachsymbols (P subsymbols)

I Possibility to add awindowing process to reducethe ACL

I Parametrized by P,M androll-off factor

Modulateddatastream

Reshapingin blockK M

TimeFrequencyfiltering

Parallelto

Serial

CPInsertion& win-dowingak

x(n)

Basebandto RF

Channel

RF tobaseband

CPremoval

Serialto

Parallel

Rx stageZF - MF

Parallelto

serial

modulateddecodedstream

ak

GFDM transceiver

I On Rx side, different architectures :MF, ZF, MMSE [7]

I With MF, need to add InterferenceCancellation (IC) scheme

I With ZF, no self-interference butnoise enhancement


Simulation parameters & Spectral EfficiencyOverall parameters

FFT size NFFT 1024Bit per Symbol m 2

Resource block size NRB 12

Number of active RBs N1Re 3 for User 1

N2Re 9 for User 2Sampling frequency Fe 15.36 MHz

OFDM and SC-FDMA parametersCyclic prefix NCP 72 samples

UFMC parametersFilter length L 73

Stop band attenuation 40 dBGFDM parameters

Number of subsymbols P 15FFT size M 1024

Roll Off factor 0.1FBMC parameters

Spreading factor K 4Asynchronous access parameters

Guard carriers [0, 1, 2, 5]Timing Offset [-0.25 :0.25]

Carrier Frequency Offset 0 ; 10%

I We consider 2 users forasynchronous multi-user accessscheme [1]

I 3 RBs for user 1 (12 carriers)I 9 RBs for user 2 (36 carriers)

I Same FFT size for all users : 1024

I Parameters are based on LTE10MHz

I Length of UFMC filter has been setto have same Spectral Efficiency forUFMC and OFDM : L = NCP + 1


Power Spectral Density

Power Spectral Density of wave-forms :

I OFDM : high ACL due tosinc in freq. domain

I UFMC has lower ACL thanGFDM (circular convolution)

I GFDM with windowing :Better OOB than GFDM andcomparable to UFMC

I Best frequency location isobtained with FBMC

1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 280

70

60

50

40

30

20

10

0

Frequency [MHz]

Power

Spectraldensity

[dBc/Hz]

OFDMUFMCFBMCwGFDMGFDM

Power spectral density of waveforms

I 2 users of 3 RBs with 1 RB of guardcarriers to better stress ACL impact


Spectral Efficiency

Spectral Efficiency for eachwaveform [bit/s/Hz]

I OFDM = mNFFTNFFT+NCP

I UFMC = mNFFTNFFT+L1

I GFDM = mPMPM+NCP

I FBMC = mSS+K 12

UFMC and OFDM have sameSEGFDM SE depends on sizeblock

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Duration of a burst [ms]

Spectral

efficiency

[b/s/H

z]form=

2

Spectral Efficiency for 5G candidates

OFDMFBMCGFDMUFMC

Comparaison between SE of waveforms

FBMC SE depends on burst duration : If burstduration > 3ms, better SE than UFMC andOFDM


Peak to Average Ratio

PAPR computed on a 3ms burst :

I PAPR = max[|y[k]|2]

E[|y[k]|2]

I We computeComplementary CumulativeDensity ProbabilityFunction (CCDF)

I Low PAPR only obtainedwith SC-FDMA

I All multicarrier modulationshave a comparable PAPR(gap around 0.5 dB)

3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11103

102

101

100

PAPR [dB]

CCDFof

PAPR

PAPR for 5G waveforms : Burst = 3 ms

OFDMUFMCSC-FDMAFBMCGFDM

PAPR measured on 3ms burst


Multi-user access scenarioComparison in a multi-user asynchronous access scenario between 2 users [1]I First user is perfectly synchronised and second user interferes with the first

one (due to time delay error and CFO)I Performance measured in terms of Mean Squared Error (MSE), with different

number of guard carriers (0, 1, 2 and 5)

Time

Frequency

User 1 : per-fectly sync

User 2 : coarsesync : CFO andtiming offset

Timing OffsetCFO

Frequency

PSD User 1 GC User 2

I Several 5G candidates with specific parametrisation (best case) :1. CP-OFDM (SC-FDMA has the same MSE)2. UFMC with windowing approach [10]3. GFDM with windowing [8] ; with MF receiver and IC [4]4. And FBMC


Multi-user access scenario : No CFOI 0 < Delay error NCP : no

interference for OFDMI No GC, GFDM with

windowing has betterperformance

I No GC, Small delay value :UFMC with windowing hasgood performance

I wGFDM > wUFMC if atleast one GC

I At least one GC inserted :FBMC has the bestperformance : no interference(Phydyas filter + OQAM[5]) !

0.2 0.1 0 0.1 0.2

60

40

20

Time delay error (n/nFFT)

MSE

[dB]

Guard carrier = 0

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 1

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 5

OFDMFBMCwUFMCwGFDM

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 2


Multi-user access scenario : 10% CFOI CFO breaks OFDM

orthogonality and lowersperformance for all waveforms

I No GC, wGFDM has sameperformance as FBMC

I No GC, Small delay value :UFMC with windowing hasthe best performance

I wGFDM > wUFMC if atleast one GC is inserted butimpact of CFO

I At least one GC inserted :FBMC has the bestperformance : no interference(Phydyas filter + OQAM) !

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 0

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 1

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 5

OFDMFBMCwUFMCwGFDM

0.2 0.1 0 0.1 0.2

60

40

20


MSE

[dB]

Guard carrier = 2


ConclusionFair comparison for several repre-sentative criteria :I Spectral Efficiency, PAPR,

PSD comparisonI Mean Square Error in

multi-user access scenario

Comparison between 5G wave-form candidates that outperformCP-OFDM :I UFMC offers LTE backward

compatibilityI GFDM and FBMC go

furtherBUT still open questions :short packet, MIMO, . . .

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

Spectral Efficiency

Spectral Efficiency ShortPacket

ACLR

PAPRMUAC (no GC)

MUAC (1 GC)

Complexity

CP-OFDM SC-FDMA UFMC GFDM FBMC

Comparison between waveforms


References I

[1] 5G-Now. Deliverable D3.2 : 5G waveform candidate selection. Technical report, 5G Now(5th Generation Non-Orthogonal Waveforms for Asynchronous Signalling), 2015.

[2] M. Bellanger. FS-FBMC : An alternative scheme for filter bank based multicarriertransmission. In 5th International Symposium on Communications Control and SignalProcessing (ISCCSP), pages 14, May 2012.

[3] M. Bellanger and al. FBMC physical layer : a primer, 06 2010.

[4] R. Datta, N. Michailow, M. Lentmaier, and G. Fettweis. GFDM interference cancellation forflexible cognitive radio PHY design. In Proc. IEEE Vehicular Technology Conference (VTCFall), pages 15, Sept 2012.

[5] J.-B. Dore, V. Berg, N. Cassiau, and D. Ktenas. FBMC receiver for multi-user asynchronoustransmission on fragmented spectrum. EURASIP Journal on Advances in Signal Processing,2014(1) :41, 2014.

[6] G. Fettweis, M. Krondorf, and S. Bittner. GFDM - generalized frequency divisionmultiplexing. In Proc. IEEE 69th Vehicular Technology Conference (VTC), pages 14, April2009.


References II

[7] N. Michailow, S. Krone, M. Lentmaier, and G. Fettweis. Bit error rate performance ofgeneralized frequency division multiplexing. In Proc. IEEE Vehicular Technology Conference(VTC Fall), pages 15, Sept 2012.

[8] N. Michailow, M. Matthe, I. Gaspar, A. Caldevilla, L. Mendes, A. Festag, and G. Fettweis.Generalized frequency division multiplexing for 5th generation cellular networks. IEEETransactions on communications,, 62(9) :30453061, Sept 2014.

[9] V. Vakilian, T. Wild, F. Schaich, S. ten Brink, and J.-F. Frigon. Universal-filteredmulti-carrier technique for wireless systems beyond LTE. In Proc. IEEE GlobecomWorkshops (GC Wkshps), pages 223228, Dec 2013.

[10] T. Wild, F. Schaich, and Y. Chen. 5G air interface design based on universal filtered(UF-)OFDM. In 19th International Conference on Digital Signal Processing (DSP), pages699704, Aug 2014.

[11] G. Wunder, P. Jung, M. Kasparick, T. Wild, F. Schaich, Y. Chen, S. Brink, I. Gaspar,N. Michailow, A. Festag, L. Mendes, N. Cassiau, D. Ktenas, M. Dryjanski, S. Pietrzyk,B. Eged, P. Vago, and F. Wiedmann. 5GNOW : non-orthogonal, asynchronous waveforms forfuture mobile applications. Communications Magazine, IEEE, 52(2) :97105, February 2014.


Context and issuesWaveformsCP-OFDM & SC-FDMAFilter bank multicarrier (FBMC)Universal Filtered Multicarrier (UFMC)Generalized Frequency Division Multiplexing (GFDM)

Comparizon between waveformsMulti-user access scenarioConclusion

Documents

5g Waveform Comparative Study Below 6ghz Ktenas Cea Leti