Filter Bank Multi-Carrier (FBMC) for Future Wireless Systems CD Laboratory Workshop Ronald Nissel November 15, 2016
Filter Bank Multi-Carrier (FBMC)for Future Wireless Systems
CD Laboratory Workshop
Ronald NisselNovember 15, 2016
Dependable Wireless Connectivity for the Society in Motion
Motivation
Slide 2 / 27
Dependable Wireless Connectivity for the Society in Motion
Multicarrier Modulation
xl,k...Transmitted data symbol
00
13
17
Time index, k
Freq
uenc
yin
dex,
l
−2 −1 0 1 2
0
0.5
1
1.5
p(t)
tT0
−5 0 5
−50
0
P(f
)
f
F0= f T0
FBMCOFDM(LTE,WLAN)
Current generation of wireless systems use OFDM.Can we do better?
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Dependable Wireless Connectivity for the Society in Motion
5G Design Paradigm: Flexible Time-Frequency Allocation
Time
Freq
uenc
y
Robust communcation(reduced spectral efficiency)
Low latency, high velocity(high efficiency if L >> K)
Large area(high efficiency if K >> L)
Required time-frequencyresources for one symbol
L ... Number of subcarriers per blockK ... Number of time-symbols per blockF ... Frequency-spacingT ... Time-spacing
F
T ∝ 1F
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Dependable Wireless Connectivity for the Society in Motion
How does FBMC work?
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Dependable Wireless Connectivity for the Society in Motion
FBMC: Time-Frequency Localized Prototype Filter
(Complex) orthogonal for TF = 2
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Dependable Wireless Connectivity for the Society in Motion
FBMC Offset-QAM: Transmit Real-Valued Symbols
Orthogonal only in the real domain: TF = 0.5
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Dependable Wireless Connectivity for the Society in Motion
Comparison of Multicarrier Schemes
MaximumSpectral
EfficiencyTF = 1
Time-Localization
Frequency-Localization
(Bi)-Orthogonal
IndependentTransmitSymbols
PureOFDM yes yes no yes yes
Windowed/FilteredOFDM
no yes yes yes yes
FBMC-OQAM yes yes yes realonly yes
CodedFBMC-OQAM yes yes yes
yes,after de-
spreadingno
Slide 8 / 27
Dependable Wireless Connectivity for the Society in Motion
Comparison of Multicarrier Schemes
−50 −40 −30 −20 −10 0 10 20 30 40 50
−100
−80
−60
−40
−20
0
Normalized Frequency, f/F
Power
SpectralDensity
(dB)
−50 −40 −30 −20 −10 0 10 20 30 40 50
−100
−80
−60
−40
−20
0
Normalized Frequency, f/F
Power
SpectralDensity
(dB)
LTE like:TF = 1.07
No OOBreduction
TF = 1.3
TF = 1.3
CP-OFDM
WindowedOFDM
FilteredOFDM
FBMCOQAMTF = 1(complex)
21 sub-carriers
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Dependable Wireless Connectivity for the Society in Motion
Real World Testbed Measurements
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Dependable Wireless Connectivity for the Society in Motion
Vienna Wireless Testbed
TX antenna
RX
Transmitter:
Receiver:
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Dependable Wireless Connectivity for the Society in Motion
Channel Estimation in FBMC1
1“On Pilot-Symbol Aided Channel Estimation in FBMC-OQAM”,R. Nissel,et.al.,2016Slide 12 / 27
Dependable Wireless Connectivity for the Society in Motion
Channel Estimation in FBMC
24
68
1012
14
24
68
1012
0
0.5
1
1.5
Channel
Time-positio
n k
Subcarrier-position l
Data symbolsPilot symbols
Time, t
Frequency, f LS estimation,
Interpolation
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Dependable Wireless Connectivity for the Society in Motion
Channel Estimation in FBMC
Cancel the imaginary interference at the pilot positions:
Time
Frequency
1 Auxiliary 2 Auxiliary Coding
Novel Contribution:I We suggest the usage of two auxiliary symbols.I We extended the coding approach to more than 8 symbolsI Downloadable MATLAB code: www.nt.tuwien.ac.at/downloads/I Validated by real world measurements
Slide 14 / 27
Dependable Wireless Connectivity for the Society in Motion
Achievable Rate Improvement: FBMC vs. OFDM (LTE)
−10 −5 0 5 10 15 20 25 30
0
5
10
15
20
25
30
SNROFDMD
(dB)
Achieva
bleRate
Improvem
ent(%
)
1 Auxiliary symbol(low complexity)
2 Auxiliary symbols(low complexity)
Coding(high complexity)
OFDM no cyclic prefix
Improvement due tobetter spectrum utilization
Improvement due tono cyclic prefix
FBMC
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Dependable Wireless Connectivity for the Society in Motion
Real World Throughput Measurements
−10 −5 0 5 10 15 20 25 30
0
5
10
15
20
25
30
SNROFDMD
(dB)
ThroughputIm
provem
ent(%
)
1 Auxiliary symbol(low complexity)
2 Auxiliary symbols(low complexity)
Coding(high complexity)
FBMC
95 % confidenceinterval obtainedby bootstrapping
mean
Slide 16 / 27
Dependable Wireless Connectivity for the Society in Motion
MIMO in FBMC2
2“Enabling Low-Complexity MIMO in FBMC-OQAM”, R. Nissel and M. Rupp, 2016Slide 17 / 27
Dependable Wireless Connectivity for the Society in Motion
Enabling MIMO in FBMC By Hadamard Spreading (+1,-1)
Coded FBMC-OQAM:
Time
Code
Frequency
Novel Contribution:I Matrix formulation: new analytical insightsI We investigate the block interference and the influence of time-varying channelsI Downloadable MATLAB code: www.nt.tuwien.ac.at/downloads/I Validated by real world measurements
Slide 18 / 27
Dependable Wireless Connectivity for the Society in Motion
Real World MIMO Measurements
−5 0 5 10 15 20 25 30
10−4
10−3
10−2
10−1
Estimated Signal-to-Noise Ratio for OFDM (dB)
BitErrorRatio
OFDMFBMC
−5 0 5 10 15 20 25 30
10−4
10−3
10−2
10−1
Estimated Signal-to-Noise Ratio for OFDM (dB)
BitErrorRatio
95 % confidenceinterval for FBMCobtained bybootstrapping 2×1 MIMO
Alamouti’s Space-TimeBlock Code
2×2 MIMOMaximum-LikelihoodDetection (2×bit rate)
2×2 MIMO (2×bit rate)Zero-Forcing Equalizer
16-QAM
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Dependable Wireless Connectivity for the Society in Motion
Bit Error Probability for FBMC in Doubly SelectiveChannels3
3“OFDM and FBMC-OQAM in Doubly-Selective Channels: Calculating the Bit ErrorProbability”, R. Nissel and M. Rupp, 2016, submitted
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Dependable Wireless Connectivity for the Society in Motion
Closed-Form BEP Expression
−5 0 5 10 15 20 25 30 35
10−3
10−2
10−1
100
BitErrorProbability,BitErrorRatio
TheoryGauss approx.Simulation
−5 0 5 10 15 20 25 30 35
10−3
10−2
10−1
100
SSiiggnnaall--ttoo--NoNoiissee RRaattiioo [[ddBB]],, sseeee ((1188))
BitErrorProbability,BitErrorRatio
OFDM (noCP)
CP-OFDM
FBMC
Vehicular A, 500km/h
OFDM (noCP)
CP-OFDM ≈FBMC
Doubly- flat
Pedestrian A, 10km/h64-QAM
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Dependable Wireless Connectivity for the Society in Motion
Outlook
Slide 22 / 27
Dependable Wireless Connectivity for the Society in Motion
Doubly-Selective Channels in FBMC
Questions:I Are one-tap equalizers good enough?I How good is FBMC compared to OFDM?I Which prototype filter
I HermiteI PHYDYAS
Fair comparison:
Sign
al-t
o-In
terf
eren
ceR
atio
Subcarrier Spacing
Optimal Subcarrier Spacing
Limiting factor:Doppler spread
(time-variant channel)
Limiting factor:delay spread
(multipath delays)
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Dependable Wireless Connectivity for the Society in Motion
Doubly-Selective Channels in FBMC
510
15
24
68
1012
0
0.5
1
1.5
OFDM Symbol
LS estimation of the piecewise mean channel
Subcarrier
|ˆ hLS
l,k|
510
15
24
68
1012
0
0.5
1
1.5
OFDM Symbol
LS estimation of the piecewise mean channel
Subcarrier
|ˆ hLS
l,k|
50100
150200
24
68
1012
0
0.5
1
1.5
time index
MMSE channel estimation
Subcarrier
|H[l,m]|
50100
150200
24
68
1012
0
0.5
1
1.5
time index
MMSE channel estimation
Subcarrier
|H[l,m]|AMMSE
I Channel estimation using time-frequency correlation
I Channel equalization
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Dependable Wireless Connectivity for the Society in Motion
Further Questions in FBMC
Bit error probability, including channel estimationI Similar to our submitted paper (which assumes perfect channel knowledge),I But now also include channel estimation.
mmWave transmissionsI TestbedI Jointly with Erich and Martin
Further investigate real world hardware effectsI QuantizationI Non-linear power amplifier
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Dependable Wireless Connectivity for the Society in Motion
Conclusions
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Dependable Wireless Connectivity for the Society in Motion
Conclusions
In contrast to most other research groups:I Downloadable MATLAB code: www.nt.tuwien.ac.at/downloads/I Theory is validated by real world testbed measurements
Main contribution in 2016:I Channel estimation in FBMCI MIMO in FBMCI Bit error probability for FBMC in doubly-selective channels
Outlook: A lot of open questions for the next years!
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Dependable Wireless Connectivity for the Society in Motion
Backup Slides
Slide 1 / 9
Dependable Wireless Connectivity for the Society in Motion
Ambiguity Function OFDM
Slide 2 / 9
Dependable Wireless Connectivity for the Society in Motion
Ambiguity Function CP-OFDM
Slide 3 / 9
Dependable Wireless Connectivity for the Society in Motion
Block InterferenceNo guard-symbols:
KT KT KT
Block 1 Block 2 Block 3
Time
Tran
smit
Pow
er
Guard time-slot:
KT T KT T KT
Block 1 Block 2 Block 3
Set time slotto zero
Time
Tran
smit
Pow
er
Slide 4 / 9
Dependable Wireless Connectivity for the Society in Motion
Block Interference
0 50 100 150 200 250
0
10
20
30
40
50
Spreading Length (Symbols)
Signal-to-InterferneceRatio(dB)
0 50 100 150 200 250
0
10
20
30
40
50
Spreading Length (Symbols)
Signal-to-InterferneceRatio(dB) One guard slot per block
(reduced efficiency)
No guard symbols(maximum spectral efficiency)
1 ms for 15 kHz subcarrier spacing, (125µs for 120 kHz)
Slide 5 / 9
Dependable Wireless Connectivity for the Society in Motion
Block Interference
0 50 100 150 200 250
0
5
10
15
20
Spreading Length (Symbols)
Efficiency
Loss
(%)
0 50 100 150 200 250
0
5
10
15
20
Spreading Length (Symbols)
Efficiency
Loss
(%)
One guard slot per block
LTE efficiency loss due to the CP
1ms for 15 kHz subcarrier spacing, (125µs for 120 kHz)
Slide 6 / 9
Dependable Wireless Connectivity for the Society in Motion
Time-Variant Channels
0 10 20 30 40 50
0
10
20
30
40
Signal-to-Interference
Ratio(dB)
Velocity (km/h) for F=15 kHz and fc=2.5 GHz
TheorySimulation
0 50 100 150 200 250 300 350 400
Velocity (km/h) for F=120 kHz and fc=2.5 GHz
0 1 2 3 4 5 6 7
x 10−3Normalized maximum Doppler shift νmax/F
0 10 20 30 40 50
0
10
20
30
40
Signal-to-Interference
Ratio(dB)
Velocity (km/h) for F=15 kHz and fc=2.5 GHz
Spreading Length K = 8
Spreading Length K = 32
One guard time slot per block
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Dependable Wireless Connectivity for the Society in Motion
Flexible Subcarrier Spacing, TF = 1 (no CP)
Channel Model: VehicularA, 250 km/h
5 10 15 20 25 30 35 40 45
0
5
10
15
20
25
30
35
Subcarrier Spacing (kHz)
Signal-to-Interference
Ratio(dB)
TheorySimulation
5 10 15 20 25 30 35 40 45
0
5
10
15
20
25
30
35
Subcarrier Spacing (kHz)
Signal-to-Interference
Ratio(dB)
OFDM
FBMC-OQAMHermite
FBMC-OQAMPhydyas
15 kHz(LTE)
Slide 8 / 9
Dependable Wireless Connectivity for the Society in Motion
Peak-To-Power Average Ratio and Signal Power Over Time
Pr(P
APR
≤PA
PR0)
6 8 10 12
10−4
10−3
10−2
10−1
100
PAPR0 (dB)0 0.1 0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Sign
alPo
wer
Time (ms)
1Aux.1Aux.flipped
2Aux.Cod.
6TFBMC
1Aux.
1Aux.flipped
2Aux.
Cod.
OFDM
Slide 9 / 9