MIMO processing for highly efficient FBMC waveforms · New waveform designs. Key ingredients: Cyclic preﬁx Circular or linear convolution Time windowing Orthogonality Pulse shaping

MIMO processing for highly efficient FBMC

waveforms

Ana I. Pérez Neira

Universitat Politècnica de Catalunya (UPC)

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

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Introduction

Traffic Forecasts

Compound annual growth rate by region

(WSA 2015) 2 / 57

Introduction

Traffic Forecasts

Spectrum and traffic growth

Spectral efficiency and freq. reuse growth

Source: R. N. Clarke, "Expanding mobile wireless capacity: The challenges presented by technology and economics,"Telecommunications Policy, vol. 38, pp. 693-708, 2014

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Introduction

Motivation: Where will an increase in wireless capacitycome from?

Strategies to keep pace with the demands of users:

◮ Cell densification together with aggressivefrequency reuse schemes

◮ Utilize larger portions of radio spectrum, e.g. themillimeter wavelength regions and autorizedspectrum sharing

◮ New technologies

Requirements imposed on the air-interface:

◮ Allow a fine-grained control of the spectrum

◮ Exhibit a reduced out-of-band radiation

◮ Achieve robustness to synchronization errors◮ MIMO

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Introduction

Motivation

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Introduction

Motivation

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Introduction

Motivation

Tx Rx

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Introduction

Motivation

Tx Rx

.

.

.

.

.

.

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Air-interface candidates

Outline

1 Air-interface candidates

2 FBMC/OQAM overview

3 MIMO architectures with CSITMIMO processing in low frequency selective subchannelsMIMO processing in frequency selective subchannels

4 MIMO processing with no CSIT

5 MIMO processing in multi-user systems

6 Open topics

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OFDM vs. FBMC

−4 −2 0 2 4−100

−80

−60

−40

−20

0

f/∆f

PS

D (

dB

)

FBMC

OFDM

100 150 200 250 300 350 400 450−150

−100

−50

0

f/∆f

PS

D (

dB

)

FBMC

OFDM

OFDM exhibits a sinc-shaped spectrum

FBMC shapes subcarriers with localized pulses in the frequency domain

FBMC transmission does not necessarily need a cyclic prefix

FBMC modulation/demodulation can be efficiently realized with FFT andpolyphase filtering

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International projects

Experimental results: Spectral efficiency for downlink PUSC, Veh A 60 km/h, channelestimation

Source: PHYDYAS Deliverable 9.3

(PHYDYAS) http://www.ict-phydyas.org/

(EMPhAtiC) http://www.ict-emphatic.eu/

(5GNOW) http://www.5gnow.eu/

(METIS) https://www.metis2020.com/

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New waveform designs. Key ingredients:

◮ Cyclic prefix

◮ Circular or linear convolution

◮ Time windowing

◮ Orthogonality

◮ Pulse shaping

Efficiency, low-complexity and good localization in time and frequencydomains

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Windowed OFDM (W-OFDM)

(n-1)th Symbol CSCP

nth Symbol CSCP

+

nth Interval

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 0.2 0.4 0.6 0.8 1 1.2 1.40

0.2

0.4

0.6

0.8

1

1.2

t/T

Am

pli

tud

e

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Filtered Multitone - FMT

(n+1)th Symbol

(n+K)th Symbol

...

nth Interval

(n-1)th Symbol

nth Symbol

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 2 4 6 8 10−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

1.2

t/T

Am

pli

tud

e

G. Cherubini, E. Eleftheriou and S. Ölçer,"Filtered multitone modulation for very high-speed digital subscriber lines," IEEE Journalon Selected Areas in Communications, vol. 20, no. 5, pp. 1016-1028, 2002.

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Cyclic Block FMT - CB-FMT

2nd Symbol

(K-1)th Symbol

...

1th Interval

0th Symbol

1th Symbol

CP

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 5 10 15 20

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

t/T

Am

pli

tud

e

A. M. Tonello, "A novel multi-carrier scheme: cyclic block filtered multitone modulation," in Proceedings of ICC, June 2013.

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Generalized frequency division multiplexing - GFDM

2nd Symbol

(K-1)th Symbol

...

1th Interval

0th Symbol

1th Symbol

CP

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 5 10 15 20

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

t/T

Am

pli

tud

e

N. Michailow, M. Matthe, I. Gaspar, A. Caldevilla, L. Mendes, A. Festag, and G. Fettweis, "Generalized Frequency DivisionMultiplexing for 5th Generation Cellular Networks," IEEE Transactions on Communications, vol. 62, no. 9, pp. 3045-3061, 2014.

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Filter bank multicarrier/OQAM - FBMC/OQAM

(n+1)th Symbol

(n+K)th Symbol

...

nth Interval

(n-1)th Symbol

nth Symbol

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 1 2 3 4 5 6 7 8−0.2

0

0.2

0.4

0.6

0.8

1

1.2

t/T

Am

pli

tud

e

P. Siohan, C. Siclet, and N. Lacaille, "Analysis and design of OFDM/OQAM systems based on filterbank theory," IEEE Trans.Signal Process., vol. 50, no. 5, pp. 1170-1183, May 2002.

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Circular convolution in FBMC/OQAM

(n+1)th Symbol

(n+K)th Symbol

...

nth Interval

(n-1)th Symbol

nth Symbol

2 4 6 8 10 12 14 16 18−70

−60

−50

−40

−30

−20

−10

0

f/∆f

PS

D (

dB

)

0 5 10 15 20−0.2

0

0.2

0.4

0.6

0.8

1

1.2

t/T

Am

pli

tud

e

M. J. Abdoli, M. Jia, and J. Ma, "Weighted circularly convolved filtering in OFDM/OQAM", in Proceedings of PIMRC 2013, Sept.2013

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Comparison

Desired features: Maximum bandwidth efficiency, simple equalizationand good localization in the time domain

These three metrics may tradeoff with each other, and thus there maynot be a unified solution to solve all the issues and satisfy all therequirements

CP Orthogonal Equalization Block structure Continuity on edges η = 1T∆f

W-OFDM Yes Yes Simple Yes Yes <1FMT No Yes Complex No Yes <1

CB-FMT Yes Yes Simple Yes No <1GFDM Yes No Complex Yes No <1

FBMC/OQAM No Yes Complex No Yes =1CC FBMC/OQAM No Yes Complex Yes No =1

FBMC/OQAM is the most spectrally efficient contender

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FBMC/OQAM overview

Outline






6 Open topics

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FBMC/OQAM overview

Block diagram QAM

Multicarrier communication systems based on QAM

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FBMC/OQAM overview

OQPSK

Offset Quadrature Phase-Shift Keying (OQPSK)

0 1 1 1 0 1 0 0

I I I IQ Q Q Q

In-phase

Quadrature

T

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FBMC/OQAM overview

Block diagram OQAM

Multicarrier communication systems based on OQAM

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FBMC/OQAM overview

OQAM processor

The imaginary part is delayed half the symbol period on even subcarriersThe real part is delayed half the symbol period on odd subcarriers

QAM symbols → xR,m[l] + jxI,m[l]PAM symbols → dm[k]

Phase term → θm[k] =

{1 k + m evenj k + m odd

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FBMC/OQAM overview

Transmitter

Transmitted signal → s[n] =∑

k∈Z

M−1∑

m=0

dm[k]θm[k]fm

[

n − kM

2

]

Subband pulses → fm[n] = p [n] ej 2πM

m(n− L−12 )

PAM symbols → dm[k]

Phase term → θm[k] =

{1 k + m evenj k + m odd

B. Saltzberg, "Performance of an efficient parallel data transmission system," IEEE Trans. Commun. Techn., vol. 15, no. 6, pp.805-811, Dec. 1967.

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FBMC/OQAM overview

Transceiver

−4 −2 0 2 4−100

−80

−60

−40

−20

0

f/∆f

PS

D (

dB

)

0 2 4 6 8−0.2

0

0.2

0.4

0.6

0.8

1

1.2

t/T

Am

plitu

de

FBMC/OQAM

OFDM

Weak orthogonality

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FBMC/OQAM overview

Synthesis filter bank: efficient implementation

Subband pulses → fm[n] = p [n] ej 2πM

m(n− L−12 ) = p [n] ej 2π

Mmnβm

Prototype pulse → p[n], n ∈ {0, ..., L − 1} , L = KM

Polyphase decomposition → P(z) =∑

n∈Z

p[n]z−n =

M−1∑

m=0

z−m

Am

(z

M)

Complexity FBMC/OQAM: 2Mlog2(M)+4KMComplexity OFDM: Mlog2(M)

(WSA 2015) 24 / 57

FBMC/OQAM overview

Analysis filter bank: efficient implementation

Demodulated symbol → yq[k] =

⟨

r[n], f∗q

[

n − kM

2

]⟩

yq[k] =

q+1∑

m=q−1

gqm[k] ⋆ (dm[k]θm[k]) + wq[k]

Equivalent Channel → gqm[k] =(fm[n] ⋆ h[n] ⋆ f ∗q [−n]

)

↓ M2

Filtered Noise → wq[k] =(w[n] ⋆ f ∗q [−n]

)

↓ M2

(WSA 2015) 25 / 57

FBMC/OQAM overview

System model

yq[k] = gqq[0]dq[k]θq[k]︸︷︷︸

Desired

+∑

τ 6=0

gqq[τ ]dq[k − τ ]θq[k − τ ]

︸︷︷︸

self ISI

+∑

m 6=q

∑

τ

gqm[τ ]dm[k − τ ]θm[k − τ ]

︸︷︷︸

ISI+ICI

+wq[k]︸︷︷︸

Noise

Symbols {dq[k]} are non-circular. Second order moments:◮ Covariance: E

{yq[k]y

∗q [k]

}= CRR + CII + j (CRI − CIR)

◮ Pseudo-covariance: E {yq[k]yq[k]} = CRR − CII + j (CRI + CIR)

Real and imaginary parts have to be independently processed toretrieve all the information. Particular case of Widely Linear:

◮ E{([ℜ (yq[k]) ℑ (yq[k])])

T [ℜ (yq[k]) ℑ (yq[k])]}=

[CRR CRI

CIR CII

]

(WSA 2015) 26 / 57

FBMC/OQAM overview

Channel model

Model 1 → gqm[k] =(fm[n] ⋆ h[n] ⋆ f ∗q [−n]

)

↓ M2

Model 2 → gqm[k] = Hm

(fm[n] ⋆ f

∗q [−n]

)

↓ M2

︸︷︷︸

αqm[k]

Intrinsic interferenceαqm[k] =

(fm[n] ⋆ f ∗q [−n]

)

↓ M2

Channel frequency response

200 202 204 206 2080

0.5

1

1.5

2

Mag

nit

ud

e

Subchannel index

ITU Vehicular A

ITU Pedestrian A

ITU Vehicular B

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MIMO architectures with CSIT

Outline






6 Open topics

(WSA 2015) 28 / 57


General architecture0

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Input/Output relation → r(ω) = AH(ω)H(ω)B(ω)s(ω) + AHw(ω)

Design equations → AH(ω)H(ω)B(ω) = IS

B(ω) ∈ CNT×S,H(ω) ∈ C

NR×NT ,A(ω) ∈ CNR×S

The complexity required to achieve a diagonal structure in the generalarchitecture renders the solution impractical

X. Mestre and D. Gregoratti, "A parallel processing approach to filterbank multicarrier MIMO transmission under strong frequencyselectivity," IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp.8078-8082, 4-9 May 2014

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Low-complexity architecture for flat fadingsubchannels

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Response mth subcarrier → Fm(ω) = P(ω − 2πm

M

)

SFB+precoder → Fm(ω)B(ω) ≈ Fm(ω)B(

2πm

M

)= Fm(ω)Bm

If the channel frequency response is flat at the subcarrier level, thenB(ω) does not present strong variations around ω = 2πm

M

(WSA 2015) 30 / 57


Channel model

Model 1 → gjiqm[k] =

(fm[n] ⋆ hji[n] ⋆ f ∗q [−n]

)

↓ M2

, 1 ≤ j ≤ NR, 1 ≤ i ≤ NT

Gqm[k] =

g11qm[k] · · · g1NT

qm [k]...

...gNR1

qm [k] · · · gNRNTqm [k]

∈ C

NR×NT

Model 2 → gjiqm[k] = Hji(m)

(fm[n] ⋆ f

∗q [−n]

)

↓ M2

︸︷︷︸

αqm[k]

, 1 ≤ j ≤ NR, 1 ≤ i ≤ NT

Gqm[k] = αqm[k]Hm = αqm[k]

H11(m) · · · H1NT (m)...

...HNR1(m) · · · HNRNT (m)

∈ C

NR×NT

Gqm[k] → Impulse response from subcarrier m to subcarrier q

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The optimal joint transceiver design is too complex. Proposed approach:

◮ Choose the least complex architecture depending on the selectivityof the channel frequency response

◮ Play with the available DoF: spatial and temporal diversity

(WSA 2015) 32 / 57

MIMO architectures with CSIT MIMO processing in low frequency selective subchannels

Joint tx-rx beamforming for flat fading subchannels

Input/output relation when θq[k] = 1:

dq[k] = ℜ(AH

q HqBq

)dq[k] +

∑

(m,τ) 6=(q,0)

ℜ(αqm[τ ]θm[k − τ ]AH

q HmBm

)

︸︷︷︸

ISI+ICI ∝ ℑ(AHq HmBm)

dm[k − τ ]

+ℜ(AH

q wq[k])

Matrix pair {Aq,Bq} in OFDM → AHq HqBq becomes diagonal

MIMO techniques designed for OFDM yield ISI and ICI. Alternatives:◮ Zero Forcing [1]:

ℜ(AT

q HqBq

)becomes diagonal and ℑ

(AH

q HqBq

)= AT

q ℑ (HqBq)︸︷︷︸

=0

◮ Coordinated beamforming [2]:ℜ(AH

q HqBq

)becomes diagonal and 0 = ℑ

(AH

q HqBq

)= AT

qℑ (HqBq)

[1] M. Caus and A. I. Pérez-Neira, "Multi-stream transmission in MIMO-FBMC systems", 2013 IEEE International Conference onAcoustics, Speech and Signal Processing (ICASSP), pp.5041-5045, 26-31 May 2013[2] Y. Cheng, P. Li and M. Haardt, "Coordinated beamforming in MIMO FBMC/OQAM systems", 2014 IEEE InternationalConference on Acoustics, Speech and Signal Processing (ICASSP), pp.484-488, 4-9 May 2014[3] M. Caus, A. I. Pérez-Neira, Y. Cheng and M. Haardt, "Towards a non-error floor multi-stream beamforming design forFBMC/OQAM", in ICC, June 2015

(WSA 2015) 33 / 57


Linear vs. Widely linear processing

Linear processing (OFDM):◮ Aq,Bq complex-valued.◮ The channel is diagonalized with these spatial channel gains:

{β1

q > · · · > βNRq

}

Widely linear processing (FBMC/OQAM ZF):◮ Non-circular nature of the symbols is taken into account◮ Aq real-valued, Bq complex-valued.◮ Dimensionality constraint imposed by the ZF condition: 2NT > NR

◮ The channel is diagonalized with these spatial channel gains:{λ1

q > · · · > λNRq

}

Gains are less spread out in FBMC/OQAM than in OFDM:◮ β1

q ≥ λ1q

◮ βNRq ≤ λNR

q

FBMC/OQAM remains competitive with OFDM if S = NR ≤ NT

(WSA 2015) 34 / 57


Numerical results

Carriers M=1024

NT = 4,NR = 2, S = 2

Subcarrier spacing ∆f =15 KHz

Sampling frequency fs=15.36MHz

Extended Vehicular A channel.Delay spread: σ = 357 ns

Active carriers to comply with thespectral mask:

◮ 600 (OFDM)◮ 650 (FBMC/OQAM)

0 5 10 15 2010

−6

10−5

10−4

10−3

10−2

10−1

ES/N

0 (dB)

BE

R

OFDM

FBMC/OQAM ZF

FBMC/OQAM direct extension of OFDM

(WSA 2015) 35 / 57

MIMO architectures with CSIT MIMO processing in frequency selective subchannels

Low-complexity architecture for frequency selectivesubchannels

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To combat the channel frequency selectivity:◮ Multi-tap equalization

System model:

dq[k] =

q+1∑

m=q−1

ℜ(AH

q [k]⋆Gqm[k]⋆ (θm[k]Bmdm[k]))+ ℜ

(AH

q [k] ⋆ wq[k])

(WSA 2015) 36 / 57


Compact formulation

dq[k] =

q+1∑

m=q−1

AT

q

(Eqm[k]⋆Bmdm[k]

)+ A

T

q wq[k]

= AT

q Eqq[0]Bqdq[k] +∑

(m,τ) 6=(q,0)

AT

q Eqm[τ ]Bmdm[k − τ ] + AT

q wq[k]

Bq ∈ RNT×S → Precoder

Aq ∈ CLaNR×S, A

T

q =[ℜ(AT

q

)ℑ(AT

q

)]→ Equalizer with La taps

Eqm[k] ∈ CLaNR×NT , Eqm[k] =

[ℜ(ET

qm[k])ℑ(ET

qm[k])]T

→ Convolution matrix

(WSA 2015) 37 / 57


Zero forcing equalization

Zero-interference: (2-dimensions, Interference from 3 subcarriers)◮ A

T

q

(Eqm[k]⋆Bmdm[k]

)= 0, m 6= q

◮ AT

q

(Eqq[k]⋆Bqdq[k]

)= Iδ[k]

DoF are increasing:

(S: streams, NT : antennas tx, NR: antennas rx)

Processing on a per-subcarrier basis:

S ≤ NT , S < 23NR

(WSA 2015) 38 / 57




T

q

(Eqm[k]⋆Bmdm[k]

)= 0, m 6= q

◮ AT

q

(Eqq[k]⋆Bqdq[k]

)= Iδ[k]

DoF are increasing:(S: streams, NT : antennas tx, NR: antennas rx)

Joint processing of N multicarrier symbols on a per-subcarrier basis:

S ≤ NT , S ≤ 23NR

(WSA 2015) 38 / 57




T

q

(Eqm[k]⋆Bmdm[k]

)= 0, m 6= q

◮ AT

q

(Eqq[k]⋆Bqdq[k]

)= Iδ[k]


Joint processing of N multicarrier symbols and two consecutive subcarriers:

S ≤ NT , S ≤ NR

(WSA 2015) 38 / 57




T

q

(Eqm[k]⋆Bmdm[k]

)= 0, m 6= q

◮ AT

q

(Eqq[k]⋆Bqdq[k]

)= Iδ[k]


Processing on a per-subcarrier basis:

S ≤ NT , S < 23NR

Joint processing of N multicarrier symbols on a per-subcarrier basis:

S ≤ NT , S ≤ 23NR

Joint processing of N multicarrier symbols and two consecutive subcarriers:

S ≤ NT , S ≤ NR

A. I. Pérez-Neira and M. Caus "Dimensionality constraints imposed by highly frequency selective channels onMIMO-FBMC/OQAM systems," in ITG Workshop on Smart Antennas (WSA), 3-5 March 2015

(WSA 2015) 38 / 57


Existing joint transceiver design

For complexity reasons the zero-interference constraint is discarded

It is possible to draw an analogy between the partial subcarrieroverlapping and the inter-user interference in multi-user communicationsystems

(WSA 2015) 39 / 57


Iterative solutions

Transmit-receive processing is governed by the MSEMSEq = E

{(dq[k]− dq[k]

) (dq[k]− dq[k]

)T}

MSEq depends on Aq, Bq−1, Bq and Bq+1

Joint tx-rx design is challenging:◮ Subcarriers are coupled◮ MSEq convex in Aq or Bq, but not jointly convex in Aq and Bq

Alternating optimization algorithms:◮ Optimize

{Aq

}fixing {Bq}

◮ Optimize {Bq} fixing{

Aq

}

H. Shen, B. Li, M. Tao, and X. Wang "MSE-Based Transceiver Designs for the MIMO Interference Channel," IEEE Transactionson Wireless Communications, vol. 9, no.11, pp. 3480-3489, November 2010

(WSA 2015) 40 / 57


Closed-form solutions

ISI and ICI terms are upper bounded to get easy-to-handle expressions

∥∥∥A

T

q Eqm[τ ]Bm

∥∥∥

2

F≤ λ1

(BmBT

m

) ∥∥∥A

T

q Eqm[τ ]∥∥∥

2

F≤ bm

∥∥∥A

T

q Eqm[τ ]∥∥∥

2

F

◮ tr (BA) ≤ tr(B)λ1(A), λ1

(BT

mBm

)≤ bm

argmin

{Aq,Bq}f0 ({UBq})

s.t.M−1∑

q=0

tr(BqB

Tq

)≤ PT

λ1

(BT

mBm

)≤ bm, 0 ≤ m ≤ M − 1

The bound is tight if 1.25 PT

SM≤ bm ≤ 2 PT

MS

UBq =∑

(m,τ) 6=(q,0)

bmAT

q Ek

qm[τ ](

AT

q Ek

qm[τ ])T

+AT

q Rwq Aq + IS − 2AT

q Eqq[0]Bq + AT

q Eqq[0]Bq

(

AT

q Eqq[0]Bq

)T

(WSA 2015) 41 / 57


Numerical results

Carriers M=1024

NR > NT = S = 2

Subcarrier spacing ∆f =15 KHz

Sampling frequency fs=15.36MHz

Extended Typical Urban channel.Delay spread: σ = 991 ns

Active carriers to comply with thespectral mask:

◮ 600 (OFDM)◮ 650 (FBMC/OQAM)

0 5 10 15 2010

−7

10−6

10−5

10−4

10−3

10−2

10−1

SNR (dB)

BE

R

OFDM

FBMC/OQAM

FBMC/OQAM direct extension of OFDM

(WSA 2015) 42 / 57

MIMO processing with no CSIT

Outline






6 Open topics

(WSA 2015) 43 / 57


No CSIT: Multiplexing

Input/output relation when θq[k] = 1:

yq[k] =∑

(m,τ)

αqm[τ ]θm[k − τ ]Hqdm[k − τ ] + wq[k]

2-D Viterbi achieves the optimal performance: Alternatives:◮ MMSE equalizer: dq[k] = ℜ

(AH

q yq[k])

◮ Partial interference cancellation:

MM=E

equalizer

yq[k] Tentative

decissions ICI

cancellationrq[k]

1-D Viterbi

rq[k] =∑

τ

αqq[τ ]θq[k − τ ]Hqdq[k − τ ] + wq[k]

R. Zakaria and D. Le Ruyet "Partial ISI cancellation with viterbi detection in MIMO filter-bank multicarrier modulation", 8thInternational Symposium on Wireless Communication Systems (ISWCS), pp.322-326, 6-9 Nov. 2011.

(WSA 2015) 44 / 57


No CSIT: Diversity

Alamouti scheme relies on a complex orthogonality whereasFBMC/OQAM has only a real orthogonality

The Alamouti coding is performed in a block-wise manner inserting gapsin order to isolate the blocks

◮ This solution is feasible when the FBMC/OQAM impulse response isconjugate symmetric, i.e. αqm[τ ] = α∗

qm[−τ ]

d1[>] d1[N]???@ntenna 1 -dC[N] -dC[>]???

dC[D] dC[E]GGGHntenna I d1[E] d1[D]GGGJI

KI

Llock 1 Llock I

M. Renfors, T. Ihalainen, and T. Stitz, "A block-Alamouti scheme for filter bank based multicarrier transmission," in EuropeanWireless Conference (EW), apr 2010, pp. 1031-1037

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MIMO processing in multi-user systems

Outline






6 Open topics

(WSA 2015) 46 / 57

MIMO processing in multi-user systems

Multi-user communication systems

A centralized transmitter serves NU decentralized receivers

. . .

AMO

AMO

Alq

. . .

. . .

PMO

PMO

. . .

BNUq

. . .. . .

. . .

. . .. . .

. . .. . .

Centralized Transmitter lth User

d1q[k]

dNUq[k]

θq[k]

θq[k]

B1q

The block diagonalization concept is used to eliminate inter-userinterference. Remaining ICI and ISI can be dealt with the ZF [1]

Inter-user interference, ISI and ICI are mitigated using an iterativealgorithm [2]

[1] M. Caus, A. I. Pérez-Neira and M. Moretti, "SDMA for FBMC with block diagonalization", IEEE 14th Workshop on SignalProcessing Advances in Wireless Communications (SPAWC), pp.709-713, 16-19 June 2013[2] Y. Cheng, P. Li, and M. Haardt, "Intrinsic interference mitigating coordinated beamforming for the FBMC/OQAM baseddownlink", EURASIP Journal on Advances in Signal Processing, May 2014.

(WSA 2015) 47 / 57

Open topics

Outline






6 Open topics

(WSA 2015) 48 / 57

Open topics

Open problems:

Optimal joint tx-rx design that takes into account:◮ ISI, ICI and the non-circular nature of the data

DoF study in multi-user communication systems

IA techniques

MISO/SIMO/MIMO MSE-duality for FBMC/OQAM systems

Take advantage of FDSS [1]

Low-complexity design that perform close to the ML detector when CSITis not available

Conclusion:

The application of MIMO to FBMC/OQAM is proven to be spectrallyefficient

Signal processing is crucial in FBMC/OQAM to manage interference

[1] M. A. Lagunas, A. I. Pérez-Neira, M. G. Amin and J. Vidal, "Spatial processing for frequency diversity schemes," IEEETransactions on Signal Processing, vol.48, no.2, pp.353,362, Feb 2000

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Open topics

References

[1] R. N. Clarke, "Expanding mobile wireless capacity: The challenges presented by technology and economics,"Telecommunications Policy, vol. 38, pp. 693-708, 2014

[2] G. Cherubini, E. Eleftheriou and S. Ölçer,"Filtered multitone modulation for very high-speed digital subscriber lines", IEEEJournal on Selected Areas in Communications, vol. 20, no. 5, pp. 1016-1028, 2002.

[3] N. Michailow, M. Matthe, I. Gaspar, A. Caldevilla, L. Mendes, A. Festag, and G. Fettweis, "Generalized Frequency DivisionMultiplexing for 5th Generation Cellular Networks", IEEE Transactions on Communications, vol. 62, no. 9, pp. 3045-3061, 2014.

[4] A. M. Tonello, "A novel multi-carrier scheme: cyclic block filtered multitone modulation", in Proceedings of ICC, June 2013.

[5] P. Siohan, C. Siclet, and N. Lacaille, "Analysis and design of OFDM/OQAM systems based on filterbank theory", IEEE Trans.Signal Process., vol. 50, no. 5, pp. 1170-1183, May 2002.

[6] M. J. Abdoli, M. Jia, and J. Ma, "Weighted circularly convolved filtering in OFDM/OQAM", in Proceedings of PIMRC 2013,Sept. 2013

[7] B. Saltzberg, "Performance of an efficient parallel data transmission system," IEEE Trans. Commun. Techn., vol. 15, no. 6, pp.805-811, Dec. 1967.

[8] X. Mestre and D. Gregoratti, "A parallel processing approach to filterbank multicarrier MIMO transmission under strongfrequency selectivity," IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pp.8078-8082, 4-9May 2014

[9] M. Caus and A. I. Pérez-Neira, "Multi-stream transmission in MIMO-FBMC systems", 2013 IEEE International Conference onAcoustics, Speech and Signal Processing (ICASSP), pp.5041-5045, 26-31 May 2013

(WSA 2015) 50 / 57

Open topics

References

[10] Y. Cheng, P. Li and M. Haardt, "Coordinated beamforming in MIMO FBMC/OQAM systems", 2014 IEEE InternationalConference on Acoustics, Speech and Signal Processing (ICASSP), pp.484-488, 4-9 May 2014

[11] M. Caus, A. I. Pérez-Neira, Y. Cheng and M. Haardt, "Towards a non-error floor multi-stream beamforming design forFBMC/OQAM", in ICC, June 2015

[12] A. I. Pérez-Neira and M. Caus "Dimensionality constraints imposed by highly frequency selective channels onMIMO-FBMC/OQAM systems," in ITG Workshop on Smart Antennas (WSA), 3-5 March 2015

[13] H. Shen, B. Li, M. Tao, and X. Wang "MSE-Based Transceiver Designs for the MIMO Interference Channel," IEEETransactions on Wireless Communications, vol. 9, no.11, pp. 3480-3489, November 2010

[14] R. Zakaria and D. Le Ruyet "Partial ISI cancellation with viterbi detection in MIMO filter-bank multicarrier modulation", 8thInternational Symposium on Wireless Communication Systems (ISWCS), pp.322-326, 6-9 Nov. 2011.

[15] M. Renfors, T. Ihalainen, and T. Stitz, "A block-Alamouti scheme for filter bank based multicarrier transmission," in EuropeanWireless Conference (EW), apr 2010, pp. 1031-1037

[16] M. Caus, A. I. Pérez-Neira and M. Moretti, "SDMA for FBMC with block diagonalization", IEEE 14th Workshop on SignalProcessing Advances in Wireless Communications (SPAWC), pp.709-713, 16-19 June 2013

[17] Y. Cheng, P. Li, and M. Haardt, "Intrinsic interference mitigating coordinated beamforming for the FBMC/OQAM baseddownlink", EURASIP Journal on Advances in Signal Processing, May 2014.

[18] M. A. Lagunas, A. I. Pérez-Neira, M. G. Amin and J. Vidal, "Spatial processing for frequency diversity schemes," IEEETransactions on Signal Processing, vol.48, no.2, pp.353,362, Feb 2000

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Open topics

THANK YOU FOR YOUR

ATTENTION

[email protected]://www.cttc.es/people/aperez/

(WSA 2015) 52 / 57

Back up

Enhanced OFDM

Side lobe suppression techniques [1]:◮ Time domain windowing:

redundancy increased wrt OFDM◮ Cancellation carriers: nonlinear

optimization with quadratic inequality◮ Polynomial cancellation coding:

spectral efficiency is reduced by thefactor of 2

◮ Subcarrier weighting: nonlinearoptimization with quadratic equalityand linear inequality

Data symbol density: 1T∆f

= TT+TCP

[1] A. Loulou and M. Renfors,"Enhanced OFDM for fragmented spectrum use in 5G systems", Transactions on EmergingTelecommunications Technologies, vol. 21, pp. 31-45, 2015.

(WSA 2015) 53 / 57

Back up

Filtered Multitone - FMT

Originally conceived for DSL [1]

Pros:◮ pulses satisfy the Nyquist constraint for

transmission without ISI

◮ pulses are not allowed to overlap in thefrequency domain

Cons:◮ Channel destroys orthogonality

◮ Overhead in burst transmission◮ Maximum bandwidth efficiency is not

achieved


= T(1+α)T

[1] G. Cherubini, E. Eleftheriou and S. Ölçer,"Filtered multitone modulation for very high-speed digital subscriber lines", IEEEJournal on Selected Areas in Communications, vol. 20, no. 5, pp. 1016-1028, 2002.

(WSA 2015) 54 / 57

Back up

Generalized frequency division multiplexing - GFDM

Transmission in blocks with oneCP shared by L symbols [1]

Pros:◮ Low overhead in burst

transmission by replacing linearfiltering with circular filtering

Cons:◮ GFDM is not an orthogonal

system

◮ Maximum bandwidth efficiencyis not achieved

Data symbol density:1

T∆f= T

T+TCP

L

[1] N. Michailow, M. Matthe, I. Gaspar, A. Caldevilla, L. Mendes, A. Festag, and G. Fettweis, "Generalized Frequency DivisionMultiplexing for 5th Generation Cellular Networks", IEEE Transactions on Communications, vol. 62, no. 9, pp. 3045-3061, 2014.

(WSA 2015) 55 / 57

Back up

Cyclic Block FMT - CB-FMT

Circular filtering concept is furtheradopted for the FMT [1]

Pros:◮ The kernel remains FMT, so

orthogonality can be achieved

◮ CP can be optionally used to simplifyequalization

◮ Low overhead in burst transmission

Cons:◮ Maximum bandwidth efficiency is not

achieved

Data symbol density:1

T∆f= T

(1+α)(T+TCP

L )

[1] A. M. Tonello, "A novel multi-carrier scheme: cyclic block filtered multitone modulation", in Proceedings of ICC, June 2013.

(WSA 2015) 56 / 57

Back up

Filter bank multicarrier/OQAM - FBMC/OQAM

Real and imaginary parts aredelayed half the symbol period [1]

Pros:◮ Maximum bandwidth efficiency is

achieved◮ Orthogonality is satisfied in the real

field

Cons:◮ Channel destroys the orthogonality◮ Overhead in burst transmission

Circular convolution can be adoptedto remove edge transitions [2]


= 1

[1] P. Siohan, C. Siclet, and N. Lacaille, "Analysis and design of OFDM/OQAM systems based on filterbank theory", IEEE Trans.Signal Process., vol. 50, no. 5, pp. 1170-1183, May 2002.[2] M. J. Abdoli, M. Jia, and J. Ma, "Weighted circularly convolved filtering in OFDM/OQAM", in Proceedings of PIMRC 2013,Sept. 2013

(WSA 2015) 57 / 57

Documents

MIMO processing for highly efficient FBMC waveforms · New waveform designs. Key ingredients: Cyclic preﬁx Circular or linear convolution Time windowing Orthogonality Pulse shaping