Comparative study of 5G waveform candidates for - Docbox

Comparative study of 5G waveform
candidates for below 6GHz air interface
Dimitri Kténas
R. Gerzaguet & D. Kténas & N. Cassiau & J-B. Doré
CEA-Leti
01/28/2016
Table of Contents
1. Context and issues
2. Waveforms
2.1 CP-OFDM & SC-FDMA
2.2 Filter bank multicarrier (FBMC)
2.3 Universal Filtered Multicarrier (UFMC)
2.4 Generalized Frequency Division Multiplexing
(GFDM)
3. Comparizon between waveforms
4. Multi-user access scenario
5. Conclusion
5G Context
I
4G massively rolled out but will soon reaches its limits
I
RAN 5G Workshop 09/15 : New non backward compatible Radio Access
Technology as part of 5G
I
Aggregation of non contiguous network is considered
I
I
Sporadic access & MTC
I
I
I
Spectrum agility : need to study alternative multicarrier waveforms
Strong traffic overhead (fast dormancy)
Massive number of devices : Use relaxed synchronism
Several candidates have been independently introduced in the past few years
I
I
Classic CP-OFDM shows its limits : Spectral efficiency, frequency leakage, need
of tight synchronisation
We propose a comparative study of 5G waveform candidates for below
6GHz air interface
ETSI presentation
Dimitri Kténas
01/28/2016
3 - 16
Context and objectives
Considering several candidates for 5G physical layer
I
Baseline for comparison : OFDM and SC-FDMA
I
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 comparison
I
Spectral Efficiency (SE)
I
Peak To Average Power Ratio (PAPR)
I
Power spectral Density (PSD)
Also consider the asynchronous multi-user scenario [1, 11]
ETSI presentation
Dimitri Kténas
01/28/2016
4 - 16
CP-OFDM & SC-FDMA
Modulated
data
stream
ak
Serial
to
parallel
DFT
& pilot
insertion
IFFT
Parallel
to
Serial
CP
Insertion
Baseband
to RF
Channel
x(n)
modulated
decoded
stream
Parallel
to
serial
IDFT
CHEST
&
Equa.
FFT
Serial
to
Parallel
CP
removal
RF to
baseband
OFDM & SC-FDMA (additional stages in dash) transceiver scheme
I
I
I
I
Multicarrier modulations, serves as physical layers for 3GPP-LTE or
802.11.a/g/n
Efficient implementation (IFFT/FFT), simple equalization schemes
Spectral efficiency loss due to Cyclic Prefix (CP) insertion to handle
multipath channel
For SC-FDMA : DFT/IDFT precoding stages to reduce PAPR (3GPP-LTE
uplink : DFT-spread OFDM)
ETSI presentation
Dimitri Kténas
01/28/2016
5 - 16
Filter bank multicarrier (FBMC)
I
Set of parallel data through bank of modulated filters
I
Good spectral location,
orthogonality and spectral
efficiency kept with OQAM
modulation
I
S
/
P
Modulated
data stream
Spreading –
Frequency
filtering
OQAM
modulation
IFFT
Overlap
and sum
FBMC Tx stage
Prototype filter in frequency
domain (FS) [2]
I
I
Overlapping factor K
Filter defined in frequency
domain (K=4)
H0 = 1
H1
=
H2
=
H3
=
ETSI presentation
H−1 = 0.971960
√
2
H−2 =
2
q
H−3 = 1 − H12
CP-OFDM (top) and FBMC
(bottom) frames
Dimitri Kténas
01/28/2016
6 - 16
Universal Filtered Multicarrier (UFMC)
I
I
I
I
Derivative of OFDM where
a group of subcarriers (RB)
is filtered with a
Dolph-Chebyshev filter with
length L and attenuation
factor [9]
B subbands are generated
and combined
Modulated
data
stream
Modulated
data
stream
Modulated
data
stream
a1k
a2k
aBk
Serial
to
parallel
Filter
F2k with
length L
IDFT
spreader
& PS
x2k
+
Serial
to
parallel
Frequency
Domain
processing
(subcarrier
equ.)
xk
Baseband
to RF
Filter
FBk with
length L
IDFT
spreader
& PS
xBk
··
·
Possibility to add a
windowing process on the
Rx side (asynchronous
multi-user scenario)
Filter
F1k with
length L
IDFT
spreader
& PS
x1k
··
·
On Rx side, Zero padding is
applied before a 2N FFT
ETSI presentation
Serial
to
parallel
··
·
2 NF F T
points
FFT
··
·
Channel
Windowing
& Serial
to parallel
RF to
baseband
Zero padding
UFMC transceiver
Dimitri Kténas
01/28/2016
7 - 16
Generalized Frequency Division Multiplexing (GFDM)
I
Based on time-frequency
filtering of data blocks of size
P ×M
I
Shaping filter : Root Raised
Cosine filter (RRC)
I
Non orthogonal waveform :
interference in time and
frequency domains
Modulated
data
stream
ak
Reshaping
in block
K×M
Time
Frequency
filtering
CP
Insertion
& windowing
Parallel
to
Serial
Baseband
to RF
x(n)
Channel
modulated
decoded
stream
Parallel
to
serial
Rx stage
ZF - MF
Serial
to
Parallel
CP
removal
RF to
baseband
ãk
GFDM transceiver
I
A CP is added at each
symbols (P subsymbols)
I
On Rx side, different architectures :
MF, ZF, MMSE [7]
I
Possibility to add a
windowing process to reduce
the ACL
I
With MF, need to add Interference
Cancellation (IC) scheme
I
I
Parametrized by P, M and
roll-off factor α
With ZF, no self-interference but
noise enhancement
ETSI presentation
Dimitri Kténas
01/28/2016
8 - 16
Simulation parameters & Spectral Efficiency
Overall parameters
FFT size
NF F T
1024
Bit per Symbol
m
2
Resource block size
NRB
12
1
NRe
3 for User 1
Number of active RBs
2
NRe
9 for User 2
Sampling frequency
Fe
15.36 MHz
OFDM and SC-FDMA parameters
Cyclic prefix
NCP
72 samples
UFMC parameters
Filter length
L
73
Stop band attenuation
40 dB
GFDM parameters
Number of subsymbols
P
15
FFT size
M
1024
Roll Off factor
α
0.1
FBMC parameters
Spreading factor
K
4
Asynchronous access parameters
Guard carriers
[0, 1, 2, 5]
Timing Offset
[-0.25 :0.25]
Carrier Frequency Offset
0 ; 10%
ETSI presentation
I
We consider 2 users for
asynchronous multi-user access
scheme [1]
I
I
3 RBs for user 1 (12 carriers)
9 RBs for user 2 (36 carriers)
I
Same FFT size for all users : 1024
I
Parameters are based on LTE
10MHz
I
Length of UFMC filter has been set
to have same Spectral Efficiency for
UFMC and OFDM : L = NCP + 1
Dimitri Kténas
01/28/2016
9 - 16
Power Spectral Density
0
Power Spectral Density of waveforms :
I
OFDM : high ACL due to
sinc in freq. domain
UFMC has lower ACL than
GFDM (circular convolution)
−20
Power Spectral density [dBc/Hz]
I
OFDM
UFMC
FBMC
wGFDM
GFDM
−10
−30
−40
−50
−60
I
I
GFDM with windowing :
Better OOB than GFDM and
comparable to UFMC
Best frequency location is
obtained with FBMC
ETSI presentation
−70
−80
−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
Frequency [MHz]
Power spectral density of waveforms
I
2 users of 3 RBs with 1 RB of guard
carriers to better stress ACL impact
Dimitri Kténas
01/28/2016
10 - 16
2
Spectral Efficiency
Spectral Efficiency for 5G candidates
Spectral Efficiency for each
waveform [bit/s/Hz]
I
I
ηOF DM =
ηU F M C =
ηGF DM =
m×NF F T
NF F T +NCP
m×NF F T
NF F T +L−1
m×P ×M
P ×M +NCP
1.8
Spectral efficiency [b/s/Hz] for m= 2
I
2
1.6
1.4
1.2
1
0.8
OFDM
FBMC
GFDM
UFMC
0.6
I
ηF BM C =
m×S
S+K− 12
UFMC and OFDM have same
SE
GFDM SE depends on size
block
ETSI presentation
0.4
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Duration of a burst [ms]
Comparaison between SE of waveforms
FBMC SE depends on burst duration : If burst
duration > 3ms, better SE than UFMC and
OFDM
Dimitri Kténas
01/28/2016
11 - 16
Peak to Average Ratio
PAPR computed on a 3ms burst :
PAPR for 5G waveforms : Burst = 3 ms
100
I
We compute
Complementary Cumulative
Density Probability
Function (CCDF)
I
Low PAPR only obtained
with SC-FDMA
I
All multicarrier modulations
have a comparable PAPR
(gap around ∼ 0.5 dB)
10−1
CCDF of PAPR
PAPR =
ETSI presentation
OFDM
UFMC
SC-FDMA
FBMC
GFDM
max[|y[k]|2 ]
E[|y[k]|2 ]
I
10−2
10−3
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
10.5
PAPR [dB]
PAPR measured on 3ms burst
Dimitri Kténas
01/28/2016
12 - 16
11
Multi-user access scenario
Comparison 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)
Frequency
PSD
User 2 : coarse
sync : CFO and
timing offset
User 1 : perfectly sync
User 1
GC
User 2
CFO
Timing Offset
Time
I
Frequency
Several 5G candidates with specific parametrisation (best case) :
1.
2.
3.
4.
CP-OFDM (SC-FDMA has the same MSE)
UFMC with windowing approach [10]
GFDM with windowing [8] ; with MF receiver and IC [4]
And FBMC
ETSI presentation
Dimitri Kténas
01/28/2016
13 - 16
Multi-user access scenario : No CFO
I
I
At least one GC inserted :
FBMC has the best
performance : no interference
(Phydyas filter + OQAM
[5]) !
ETSI presentation
−20
MSE [dB]
−20
−40
−40
−60
−60
No GC, Small delay value :
UFMC with windowing has
good performance
wGFDM > wUFMC if at
least one GC
Guard carrier = 1
−0.2 −0.1
0
0.1
−0.2 −0.1
0.2
Time delay error (n/nFFT)
0
0.1
0.2
Time delay error (n/nFFT)
Guard carrier = 2
Guard carrier = 5
−20
−20
MSE [dB]
I
No GC, GFDM with
windowing has better
performance
Guard carrier = 0
MSE [dB]
I
0 < Delay error NCP : no
interference for OFDM
MSE [dB]
I
−40
−60
−40
−60
−0.2 −0.1
0
0.1
0.2
Time delay error (n/nFFT)
−0.2 −0.1
0
0.1
0.2
Time delay error (n/nFFT)
OFDM
FBMC
wUFMC
wGFDM
Dimitri Kténas
01/28/2016
14 - 16
Multi-user access scenario : 10% CFO
I
I
Guard carrier = 0
−20
MSE [dB]
MSE [dB]
−20
No GC, wGFDM has same
performance as FBMC
−40
−60
At least one GC inserted :
FBMC has the best
performance : no interference
(Phydyas filter + OQAM) !
ETSI presentation
0
0.1
−0.2 −0.1
0.2
Time delay error (n/nFFT)
0
0.1
0.2
Time delay error (n/nFFT)
Guard carrier = 2
Guard carrier = 5
−20
−20
−40
−40
−60
−60
−0.2 −0.1
I
−40
−60
−0.2 −0.1
No GC, Small delay value :
UFMC with windowing has
the best performance
wGFDM > wUFMC if at
least one GC is inserted but
impact of CFO
Guard carrier = 1
MSE [dB]
I
CFO breaks OFDM
orthogonality and lowers
performance for all waveforms
MSE [dB]
I
0
0.1
0.2
Time delay error (n/nFFT)
−0.2 −0.1
0
0.1
0.2
Time delay error (n/nFFT)
OFDM
FBMC
wUFMC
wGFDM
Dimitri Kténas
01/28/2016
15 - 16
Conclusion
Fair comparison for several representative criteria :
CP-OFDM
I
Spectral Efficiency, PAPR,
PSD comparison
I
Mean Square Error in
multi-user access scenario
Comparison between 5G waveform candidates that outperform
CP-OFDM :
I
UFMC offers LTE backward
compatibility
I
GFDM and FBMC go
further
BUT still open questions :
short packet, MIMO, . . .
ETSI presentation
Complexity
SC-FDMA
UFMC
GFDM
Spectral Efficiency
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
FBMC
Spectral Efficiency Short
Packet
MUAC (1 GC)
ACLR
MUAC (no GC)
PAPR
Comparison between waveforms
Dimitri Kténas
01/28/2016
16 - 16
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 multicarrier
transmission. In 5th International Symposium on Communications Control and Signal
Processing (ISCCSP), pages 1–4, 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 for
flexible cognitive radio PHY design. In Proc. IEEE Vehicular Technology Conference (VTC
Fall), pages 1–5, Sept 2012.
[5]
J.-B. Dore, V. Berg, N. Cassiau, and D. Ktenas. FBMC receiver for multi-user asynchronous
transmission 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 division
multiplexing. In Proc. IEEE 69th Vehicular Technology Conference (VTC), pages 1–4, April
2009.
ETSI presentation
Dimitri Kténas
01/28/2016
17 - 16
References II
[7]
N. Michailow, S. Krone, M. Lentmaier, and G. Fettweis. Bit error rate performance of
generalized frequency division multiplexing. In Proc. IEEE Vehicular Technology Conference
(VTC Fall), pages 1–5, 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. IEEE
Transactions on communications,, 62(9) :3045–3061, Sept 2014.
[9]
V. Vakilian, T. Wild, F. Schaich, S. ten Brink, and J.-F. Frigon. Universal-filtered
multi-carrier technique for wireless systems beyond LTE. In Proc. IEEE Globecom
Workshops (GC Wkshps), pages 223–228, 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), pages
699–704, 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 for
future mobile applications. Communications Magazine, IEEE, 52(2) :97–105, February 2014.
ETSI presentation
Dimitri Kténas
01/28/2016
18 - 16