ssd 2015 presentation, pops-ofdm: ping-pong optimized pulse shaping ofdm for 5g cellular systems and...

1

POPS-OFDM:

Ping-Pong Optimized Pulse Shaping OFDM for

5G Cellular Systems and Beyond

Mohamed SIALA

Ecole Supérieure des Communications de Tunis (SUP’COM)

12th International Multi-Conference on Systems, Signals &

Devices (SSD’2015)

March 16 - 19, 2015 - Mahdia, Tunisia

Outline

Motivation of Research Activities on Pulse Shaping for OFDM

Background on Multi-Carrier Systems

5G Challenges and Requirements

POPS-OFDM

Conclusion and Perspectives

2

Motivation of Research Activities on Pulse

Shaping for OFDM

3

5G Challenges and Requirements 1/5

4

5GNOW


55GNOW


6

5GNOW


7

5GNOW


The main drivers for 5G are:

Tactile Internet: The human tactile sense distinguishes latencies in the order of 1ms 1ms round trip time requires a time budget on

PHY of maximum 100 µs.

Internet of Things (IoT): A scalability problem (>100k MTC nodes

in a cell) under cost, coverage, energy (life time) and privacy

constraints.

Gigabit Wireless Connectivity: Quick downloads (streaming content with data rates in the order of ~100 Mbit/s) Download

times in the order of ~ 10 Gbit/s.

Fragmented Spectrum and the Spectrum Paradox: Spectrum is

scarce and expensive but underutilized. With White Spaces

Communication, a 100x better localization is expected.

8

4G (LTE-A) Pitfalls

LTE is tailored to maximize performance by enforcing strict synchronism and orthogonality

Machine-type communication (MTC) communications requires

bulky procedures to ensure strict synchronism

Collaborative schemes (e.g. CoMP) use tremendous efforts to

collect gains under strict synchronism and orthogonality

Digital Agenda/Carrier aggregation forces systems to deal with

fragmented spectrum

9

Need for Non-Orthogonal Waveforms

Non-orthogonal waveforms on the physical layer will enable:

Asynchronous MTC traffic with drastically reduced signalling and

increased life time

The provision of asynchronous coordinated multi-point (CoMP) /

Heterogeneous Networking (HetNet)

Implementation of asynchronous carrier aggregation concepts with

well frequency localization

A (filtered) multicarrier approach will enable:

The mix of synchronous / asynchronous and orthogonal / non-

orthogonal traffic types

The aggregation of non-contiguous spectrum thanks to low out-of-

band emissions of the non-orthogonal waveforms

10

Workload of Current Mobiles

11

Outer receiver consists of channel decoder and de-interleaver

Projects on 5G

From 2007 to 2013, the European Union set aside €700 million of

funding (FP7) for research on future networks, half of which was

reserved for wireless technologies and the development of 4G and

beyond-4G technologies.

METIS, 5GNOW, iJOIN, TROPIC, Mobile Cloud Networking,

COMBO, MOTO and PHYLAWS are some of the latest EU research

projects that address the architecture and functionality needs of 5G

networks, representing some €50 million EU investment

European Union’s FP7 projects, PHYDYAS (Duration: 30 months,

Start: January 2008, End: October 2010, Total Cost: 4 093 483€),

investigated Filter Bank Multi-Carrier (FBMC) and corresponding

transceiver functionalities

12

5GNOW Candidate Waveforms

European Union’s FP7 projects, 5GNOW (5th Generation Non-

Orthogonal Waveforms for Asynchronous Signaling), (Start:

September 2012, End: February 2015, Total Cost: 3 526 991 €),

investigated 4 candidate waveforms:

Generalized frequency division multiplexing (GFDM)

Universal Filtered Multicarrier (UFMC): UFMC applies filtering

to subsets of the complete band instead of single subcarriers

(GFDM) or the complete band (Filtered OFDM)

Filter Bank MultiCarrier (FBMC)

Bi-orthogonal Frequency Division Multiplexing (BFDM)

13

GFDM: Generalized Frequency Division

Multiplexing

14

UFMC: Universal Filtered MultiCarrier

15

Spectral behavior within a single sub-band

Single PRB compared to OFDM

Background on Multi-Carrier Systems

16

17

History of OFDM

Late 50’s: Concept of multicarrier without overlapping in frequency

Late 60’s: Orthogonal multicarrier [Chang66, Salzberg67]

Early 70’s: Use of the Fast Fourier Transform (FFT) [Weinstein &

Ebert71] - Concept of Guard Interval (GI)

Early 80’s: Concept of Cyclic Prefix (CP) [Peled & Ruiz80]

Early 90’s: DAB standardization

Late 90’s: Standardization of ADSL, DBV-T and WIFI

18

Applications of OFDM

Wireless applications :

Broadcasting for digital terrestrial television (DVB- T, DVB- H)

Digital Audio Broadcasting (DAB) and Digital Radio Mondiale

(DRM)

802.11a wireless networks (WIFI5) , 802.16 (WiMAX) and

HiperLAN/2

New generation radio mobile networks (LTE, LTE-A)

Wireline applications:

ADSL

PLC (Power-Line Communications)

Classification of Multi-Carrier Systems

19

Multi-carrier systems

Filter Lattice Symbol

Ort

hogonal

Hex

agonal

Bio

rthogonal

Rec

tangula

r

Non-o

rthogonal

Sta

gger

ed

Com

ple

x

Rea

l

OF

DM

w/o

GI

OF

DM

w/

CP

OF

DM

/QA

M

OF

DM

/OQ

AM

OF

DM

w/

ZP

Pulse

Mono-p

uls

e

Mult

i-puls

eU

FM

C

OF

DM

OQAM: Offset Quadrature Amplitude Modulation

CP: Cyclic Prefix, ZP: Zero Padding, GI/ Guard Interval

TimeC

onti

nuous

Dis

cret

e

20

Pulse Shaping for OFDM without Guard Interval

Rectangular pulse shaping filter with duration T :

1/T

t

[0, [( ) rect ( ) /Tt t T

1

ˆ( ) sinc( )f fT

1/T

T

… …f

Fourier Transform

21

OFDM without Guard Interval

t

f

nT ( 1)n T0 0f

/mf m T

1 ( 1) /Nf N T

… …

0 ( )n t

1, ( )N n t

tnT ( 1)n T

… …

( 1)n T ( 2)n T

OFDM symbol between nT and (n+1)T

Modulated Signal ee(t)

Orthogonal

sinusoidal

functions

( )mn t

Time-Frequency Lattice Layout: OFDM without

Guard Interval (GI)

22

Frequency

Time

1/ uF T

uT TArea (1/ ) 1u uFT T T

Lattice density 1/ 1FT Critical density

0 & π/2 0 & π/20 & π/20 & π/2

0 & π/2 0 & π/20 & π/20 & π/2

0 & π/2 0 & π/20 & π/20 & π/2

0 & π/2 0 & π/20 & π/20 & π/2

Inphase and quadrature

components

23

Power Spectral Density of OFDM without Guard

Interval 1/2

Subcarrier spacing : f = 1/T

1/f T

f

Power Spectral Density of OFDM without Guard

Interval 2/2

24

16N

0gT

32N

64N 128N

25

Analog Transmitter for OFDM

Complex implementation: Use of a battery of N costly analog filters

ka

0na

mna

1,N na

S

/

P

( )t

( )t

( )t

0exp( 2 )j f t

exp( 2 )mj f t

1exp( 2 )Nj f t exp( 2 )cj f t

{} ( )ee t ( )e t

S/P : Serial-to-Parallel Converter

0m

mf f

T

0 0f in general

26

Vectorial Equivalent of the OFDM Transmitter

ka

0na

mna

1,N na

S

/

P

exp( 2 )cj f t

{} ( )ee t ( )e t

0 ( )n t

( )mn t

1, ( )N n t

27

Analog Receiver for OFDM

Complex implementation: Use of a battery of N costly analog filters

ˆkaP

/

S

( )t

0exp( 2 )j f t

exp( 2 )mj f t

1exp( 2 )Nj f t exp( 2 )cj f t

( )x t

P/S : Parallel to Serial Converter

0ˆ

na

ˆmna

1,ˆ

N na

( )t

( )t

*( ) ( )t T t

28

Vectorial Equivalent of the OFDM Receiver

ˆkaP

/

S

exp( 2 )cj f t

( )r t

0ˆ

na

ˆmna

1,ˆ

N na

*( ), ( ) ( ) ( )u t v t u t v t dt

0 ( ),n t

( ),mn t

1, ( ),N n t

29

No Interference in the Gaussian Channel –

Orthogonality Contraints

Modulated signal:

Symbol amn transported by function :

Absence of Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) equivalent to orthogonality conditions:

Functions {mn(t)} form un orthonormal base of the space of modulated signals

1

0( ) ( )

N

e mn mnn me t a t

( ) ( ) exp( 2 )mn mt t nT j f t

*( ), ( ) ( ) ( )kl mn kl mn km lnt t t t dt

Balian-Low Theorem for a Time-Frequency

Critical Lattice Density

30

( ) ( )exp( 2 )mn t t nT j mFt

2 22 2 ˆ( ) ( )t t dt or f f df

Fourier transform of ( )t

31

Behavior of an OFDM System without GI in the

Presence of Time Dispersive Channel

t

f

nT ( 1)n T0 0f

/mf m T

1 ( 1) /Nf N T

… …

tnT ( 1)n T

… …

( 1)n T ( 2)n T

Noiseless received

signal

( )c

Channel

Inter-Symbol Interference

(ISI)

Loss

of orthogonality!

mT0

0 ( )n t

1, ( )N n t

( )mn t

32

Interference Suppression: Guard Interval Insertion with

Zero Padding (ZP)

t

f

… …

tnT ( 1)n T

… …

( 1)n T

1, ( )N n t

( )mn t

0 ( )n t

T

gTuT

( )c Channel

mT0

g mT T

Guard Interval

Zero Padding

33


Zero Padding (ZP)

t

… …

No Inter-Symbol

Interference (ISI)

Persistent loss of

orthogonality!

t

f

… …

g mT TT

34


Cyclic Prefix (CP)

t

… …

tnT ( 1)n T

… …

( 1)n T

0 ( )n t

T

gT uT

( )c Channel

mT0

f

Cyclic Prefix

1, ( )N n t

( )mn t

nT ( 1)n T( 1)n T

Time-Frequency Lattice Layout: OFDM with

Cyclic Prefix (CP)

35

Time

1/ uF T

u gT T T Area (1/ )( ) 1 / 1u u g g uFT T T T T T

Lattice density 1/ 1FT

Frequency

uTgT

Cyclic Prefix Useful part

Power Spectrum Density of Conventional OFDM

36

16N

/ 4g uT T

32N

64N 128N

37


Cyclic Prefix (CP)

t

… …

tnT ( 1)n T

… …

( 1)n T

T

gT uT

f

Overlapping restricted

to the Guard Interval

0 ( )n t

1, ( )N n t

( )mn t

38


Cyclic Prefix (CP)

t

… …

t

… …

fRecovered

orthogonality

t

… …

( 1)n T( 1)n T

Cyclic Prefix Suppression

1, ( )N n t

( )mn t

0 ( )n t

nT

39

OFDM/OQAM with Square Lattice

The used shaping filter filtre is generally a root-raised cosine filter with

roll-off (typically equal to 1)

OFDM with Offset QAM (OQAM) alternately transmit phase and

quadrature

t

1/f T QAM

Symbol

f

T/ 2T

: In-phase component : Quadrature component

Time-Frequency Lattice Layout: OFDM/OQAM

with Square Lattice

40

Frequency

Time

1/ uF T

/ 2uT TSurface (1/ )( / 2) 1/ 2u uFT T T

Lattice density 1/ 2FT Critical density

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

π/2

Quadrature componentInphase component

Time-Frequency Lattice Layout: OFDM/OQAM

with Hexagonal Lattice

41

Frequency

Time

3π/4

π/2 0

π/4 3π/4

π/2 0

π/43π/4

π/2 0

π/4

3π/4

π/2 0

π/4 3π/4

π/2 0

π/43π/4

π/2 0

π/4

Lattice density 1 Critical density

[1] M. Siala, “Novel OFDM/OQAM system with hexagonal time-frequency lattice,” Third International Symposium on

Image/Video Communications over fixed and mobile networks (ISIVC’06), Hammamet, Tunisia, September 2006.

[2] M. Siala and A. Yongaçoglu, “Prototype waveform optimization for an OFDM/OQAM system with hexagonal

time-frequency lattice structure,” 9th International Symposium on Signal Processing and its Applications (ISSPA’07),

Sharjah, United Arab Emirates, February 2007.

Waveforms for OFDM/OQAM

42

Linear decreasing in the

logarithmic scale

Exponential decrease in

time and frequency

Gaussian waveform

Hexagonal lattice waveform

[1] M. Siala, “Novel OFDM/OQAM system with hexagonal time-frequency lattice,” Third International Symposium

on Image/Video Communications over fixed and mobile networks (ISIVC’06), Hammamet, Tunisia, September 2006.

Small-Scale Propagation: Multipath Rayleigh

Fading 1/2

43

Time

F

T

Frequency

Doppler shift

Time delay

minmin Df

max Df

max

: Doppler spread

DB

mT

: Delay spread

DB

mT

Scattering function

Small-Scale Propagation: Multipath Rayleigh

Fading 2/2

44

Time

F

T

Frequency

Doppler shift

Time delay

: Channel spread

DB

mT

D mB T

(Diffuse) Scattering function

ISIISI

ICI

ICI

ISI: Inter-Symbol Interference

ICI: Inter-Carrier Interference

Doppler Spread-Delay Spread Balancing 1/3

45

Time

F

T

Frequency

Doppler shift

Time delayDB

mT

Reduction in F & Increase in T

Substantial increase in ICI Global increase in ICI+ISI

ISIISI

ICI

ICI


46

Time

F

T

Frequency

Doppler shift

Time delayDB

mT

ISI

ICI

ICI

ISI

Reduction in T & Increase in F

Substantial increase in ISI Global increase in ICI+ISI


47

Time

F

T

Frequency

Doppler shift

Time delayDB

mT

ISIISI

ICI

ICI

Good balancing between T and F

Global reduction in ICI+ISI

mDTB

F T

5G Challenges and Requirements

48

Requirements for 5G: Coordinated MultiPoint

(CoMP)

Joint Processing (JP):

Coordination between multiple BSs

MSs are simultaneously transmitting or receiving to or from

multiple BSs

Coordinated Scheduling/Coordinated Beamforming (CS/CB):

Coordination between multiple BSs

MSs are transmitting or receiving to or from a single transmission

or reception BS

49


(CoMP) – Overlapping in Time

50

timeAt the BSs

MS2MS1

timetime

TDOA Overlapping in time

Artificial delay spread

Inter-Symbol Interference

At MS2At MS1

TDOA: Time Difference of Arrival

Applicable even for fully

time synchronous BSs


(CoMP) – Overlapping in Frequency

51

MS

frequency

Carrier Frequency Offset Overlapping in frequency Artificial Doppler spread

Inter-Carrier Interference (ICI)

At MS

From BS1

frequency

frequency

From BS2

From BS3Applicable only for not fully

frequency Synchronous BSs

Requirements for 4G, 5G and DVB-T: MBMS

and SFN

52

time

At the BSs/DVB-T TV Station

Overlapping replicas Artificial delay spread Interference

time

At the TV Set

(SFN)

At the MS

(MBMS)

SFN: Single Frequency

Network

MBMS: Multimedia Broadcast

Multicast Service

Requirements for 5G: Sporadic Traffic and Fast

Dormancy 1/4

2, 3 and 4G systems continuously transmit reference signals and

broadcast system information that is used by terminals as they move

across cells

The more signaling the cellular standard requires the more complex

and power-hungry will be the devices

With denser deployment and more network nodes (MTC), such

“always-on” transmissions are not attractive from an interference and

energy consumption perspective

Maximizing the devices’ sleep opportunities, through sporadic

access, can minimize energy consumption, leading to long battery life

53


Dormancy 2/4

Sporadic access poses a significant challenge to mobile access

networks due to fast dormancy:

Fast dormancy is used to save battery power: The mobile breaks

ties to the network as soon as a data piece is delivered

When the mobile has to deliver more pieces of data it will always

go through the complete synchronization procedure again

This can happen several hundred times a day, resulting in

significant control signaling growth and network congestion threat

It is desirable to achieve “zero-overhead” communications by

providing channel access with minimal signaling

54


Dormancy 3/4

Get rid of closed-loop timing control (which costs energy and

signaling overhead, being undesirable for MTC) and use open loop

timing control mechanisms: The device uses the downlink pilot signals

by the BS for a rough synchronization

55


Dormancy 4/4

56Nokia Siemens Networks, Understanding Smartphone Behavior in the Network,

White Paper, 2011, [Available: http://www.nokiasiemensnetworks.com/sites/default/files

Comparisons of Data and Signaling Traffic


Dormancy – Relaxed Frequency Synchronization

57

MS2

frequency

Reduced synchronization overhead Relaxed frequency synchronization

Carrier Frequency Offset Overlapping in frequency

Inter-user interference in frequency

From MS1

frequency

From MS2

MS1MS3

frequencyFrom MS3

At BS

frequency

Inter-user interference

Unaligned carrier frequencies


Dormancy – Relaxed Time Synchronization

58

MS2

time

Reduced synchronization overhead Relaxed time synchronization

Overlapping in time

Inter-user interference in time

From MS1

time

From MS2

MS1

At BS

time

Inter-user interference

Requirements for 5G: Asynchronous Signaling in

the Uplink – RACH 1/2

59

MS2MS1

RACH random access

Requirements for 5G: Asynchronous Signaling in

the Uplink – RACH 2/2

60

time

No synchronization overhead Strong overlapping in time

Inter-user interference in time

To/from BS

time

To/from MS1

To/from MS2

Inter-Burst interference

time

Synchronization

channel

RACH burst

from MS2

RACH burst

from MS1Propagation

delay to MS1

Propagation

delay to MS2

Requirements for 5G: Spectrum Agility and

Carrier Aggregation 1/2

TV White Spaces (TVWS) exploration can represent a new niche

markets if it overcome, with spectrum agility, the rigorous

implementation requirements of low out of band radiation for

protection of legacy systems

The LTE-A waveform imposes generous guard bands to satisfy

spectral mask requirements which either severely deteriorate spectral

efficiency or even prevent band usage at all

5G will address carrier aggregation by implementing non-orthogonal

waveform, with low out-of-band emissions, in order not to interfere

with other legacy systems and tight spectral masks

61

Requirements for 5G: Spectrum Agility and

Carrier Aggregation 2/2

62

OFDM+CP vs. ESM: Loss of efficient of traditional OFDM with CP to fit in

an ESM (Emission Spectrum Mask) due its non-negligible side lobes

Requirements for 5G: Low Latency 1/2

4G offers latencies of multiple 10 ms between terminal and BS that

originate from resource scheduling, frame processing, retransmission

procedures, and so on.

The access latency offered by LTE is not sufficient for latency-critical

applications, such as tactile internet (motivated by the tactile sense of

the human body, which can distinguish latencies on the order of 1 ms

accuracy), traffic safety and infrastructure protection.

To ensure support for such mission-critical MTC applications, next-

generation wireless access should allow for latencies on the order of 1

ms or less.

63

Requirements for 5G: Low Latency 2/2

A 1 ms round-trip time for a typical tactile interaction requires a time

budget of maximum 100 µs on the physical layer

Far shorter than LTE-A allow, missing the target by nearly two

orders of magnitude

Clear motivation for an innovative and disruptive redesign of

the PHY layer

Lower latency over the radio link can be achieved by reducing

transmission-time intervals and widening the bandwidth of radio

resource blocks in which a specific amount of data is transmitted

64

Requirements for 5G: Lower Latency vs Doppler

Spread-Delay Spread Balancing 1/2

65

Time

F

T

Frequency

Doppler shift

Time delayDB

mT

Reduced global ICI+ISI Good balancing between T and F

Increased Latency

ICI

ICI

ISIISI

Processing

Time at the Rx2

mTmin

Contribution of the PHY to the latency

Requirements for 5G: Lower Latency vs Doppler

Spread-Delay Spread Balancing 2/2

66

Time

F

T

Frequency

Doppler shift

Time

delayDB

mT

Decreased Latency

Bad balancing between

T and F

Increased global

ICI+ISI ISIISI

Processing

Time at the Rx2

mTmin

Contribution of the PHY to the latency

ICI

ICI

POPS-OFDM

67

POPS-OFDM Categories

68

POPS-OFDM

Continuous DiscreteTime

Optimum

exploration space2 ( ) 2 ( )

Practical

exploration space

1

0Vect({ ( )} )N

k kt

1

0Vect({ ( )} )N

k kt

2 ( )I

0{ ( )}k kt

0{ ( )}k kt

: Hermite functions

: Prolate Spheroidal Wave Functions (PSWF)

To be explored next

33φ32φ31φ30φ

23φ22φ21φ20φ

13φ12φ11φ10φ

OFDM Time-Frequency Lattice: Transmitter

Side

Time

Frequency

Signal

00 φ φ 01φ 02φ 03φ

Time Shift by TTime Shift by 2TTime Shift by 3T

Frequency

Shift by F

Frequency

Shift by 2F

Frequency

Shift by 3F

Symbol Period T

=

Symbol Spacing

Symbol Bandwidth F = Subcarrier Spacing

: Transmitter Prototype Waveform (Vector)φ

: (OFDM) Symbol PeriodT

: Subcarrier SpacingFmnφ

Subcarrier Index Symbol Index

Frequency shift of by mF Time shift of by nT69

30 30a φ

20 20a φ

10 10a φ

00 00a φ

1

0 0

0

Q

m m

m

a

φ

OFDM Transmitted Signal

Time

Frequency

Signal21 21a φ

11 11a φ

01 01a φ

31 31a φ

1

1 1

0

Q

m m

m

a

φ

1

0

: Sampled Version of the Transmitted OFDM SignalQ

mn mn

n m

a

e φ

1

2 2

0

Q

m m

m

a

φ

32 32a φ

22 22a φ

12 12a φ

02 02a φ

1

3 3

0

Q

m m

m

a

φ

33 33a φ

23 23a φ

13 13a φ

03 03a φ

SubcarriersQ

70

Propagation Channel Characteristics: Delay and

Doppler Spreads

Mobile speed

( , )S p

p

dB : Doppler spread

Doppler spread spectrum

: Discrete time delay

: Doppler frequency shift

( , )S p : Channel scattering function

: Discrete time delay spreadmT 71

30 30a φ

20 20a φ

10 10a φ

00 00a φ

1

0 0

0

Q

m m

m

a

φ

OFDM Received Signal

Time

Frequency

Signal

1

0

: Sampled Version of the Received OFDM SignalQ

mn mn

n m

a

r φ n

21 21a φ

11 11a φ

01 01a φ

31 31a φ

1

1 1

0

Q

m m

m

a

φ

: Additive White Gaussian Noisen

: Channel distorted version of mn mnφ φ

72

ISIICI

Decision variables

: Receiver Prototype Waveform (Vector)ψ

klψ

Subcarrier Index Symbol Index

Frequency shift of by kF Time shift of by lT

H

kl kl ψ r : Decision variable on kla

( , ) ( , )Noise TermUseful Term

Interference Term

H H H

kl kl kl kl mn kl mn kl

m n k l

a a

ψ φ ψ φ ψ n

73

Signal-to-Interference and Noise Ratio (SINR)

S

I N

PSINR

P P

: Average power of the Useful Term

: Average power of the Interference Term

: Average power of the Noise Term

S

I

N

P

P

P

( , )

( , )

1

H

S p

H

S p

SINR

SNR

φ

φ

ψ KS ψ

ψ KI I ψ

: Ratio of two definite positive quadratic

forms on for a given

( , )

( , )

1

H

S p

H

S p

SINR

SNR

ψ

ψ

φ KS φ

φ KI I φ

: Ratio of two definite positive quadratic

forms on for a given

0

: Signal to Noise RatioE

SNRN

74

Optimization Philosophy

Transmitter Side Receiver Side(0)φ

(0 )

(0)

( , )

( , )

Maximize 1

H

S p

H

S p

SINR

SNR

φ

φ

ψ KS ψ

ψ KI I ψ (0)ψ

(0 )

(0 )

( , )

( , )

Maximize 1

H

S p

H

S p

SINR

SNR

ψ

ψ

φ KS φ

φ KI I φ(1)φ

(1)

(1)

( , )

( , )

Maximize 1

H

S p

H

S p

SINR

SNR

φ

φ

ψ KS ψ

ψ KI I ψ (1)ψ

(1)

(1)

( , )

( , )

Maximize 1

H

S p

H

S p

SINR

SNR

ψ

ψ

φ KS φ

φ KI I φ(2)

φ 75

Optimization Philosophy

φ

ψ

(0)φ

(0)ψ

(1)φ

(1)ψ

(2)φ

76SINR

Equal-SINR curves

(Contour plot of SINR)

SINR maximum

First Optimization Technique

SINR

0

ψ

( , ) ( , )

1S p S p

SINR φ φ

KI ψ KS ψ

Generalized Eigenvalue Problem

Find the eigenvector with the smallest eigenvalue

SINR

0

φ

( , ) ( , )

1S p S p

SINR ψ ψ

KI φ KS φ

77

Second Optimization Technique

( , )

( , )

H

S p

H

S p

SINR

φ

φ

ψ KS ψ

ψ KIN ψ

( , )

H

S p φKIN UΛU

: Unitary Matrix

: Diagonal Positive Matrix

U

Λ

( , )

H H H H

S p φψ KIN ψ ψ UΛU ψ u u

1/2 Hu Λ U ψ

H

HSINR

u Φu

u u

1/2 1/2

( , )

H

S p

φΦ Λ U KS UΛ

maxFind the eigenvector of with maximum eigenvalueu Φ

1/ 2

max

1/ 2

max

opt

UΛ uψ

UΛ u78

Signal and Interference Kernel Computation

1/3

1

( , )

0

( )k

KH

S p nN k p

n k

φ

K Σ Σ φφ Ω

0 ( ( )) if ( )mod 0

0 else

D s

pq

QJ B T p q p q Q

1

0 ( , )

0

( )k

KH

S p k p

k

φ

K Σ φφ Π

0( ( ))pq D sJ B T p q

( , ) 0 ( , )S p S p φ φKS K ( , ) ( , ) 0 ( , )S p S p S p φ φ φ

KI K K

Π Q Ω

Dependence on channel Doppler; Computed once

DN Q

79


2/3

φ H φφ

1

0

( )k

KH

k p

k

Σ φφ

Duration: DT

DN samples

80

Matrix shifts according to

The multipath power profile


3/3

1

0

( )k

KH

nN k p

n k

Σ Σ φφ

Matrix shifts according to

the normalized symbol duration N

81

Numerical Results: Impact of Initialization and

Existence of Local Maxima

82

Local maxima

Numerical Results: Evolution of Transmit and

Receive Pulse Shapes Through the Iterations

83

Iterations: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,…,20,…,30,…,100

φ ψ

Initialization: Gaussian pulse

Numerical Results: Doppler Spread-Delay Spread

Balancing

84

Best balancing

Numerical Results: Doppler Spread-Delay Spread

Balancing

85

Numerical Results: Optimized Waveforms

86

Numerical Results: Optimized Waveforms

87

Numerical Results: Performance and Gain in

SINR – Identical Pulse Shape Durations

88

Gain > 5dB

Numerical Results: Performance and Gain in

SINR – Different Pulse Shape Durations

89

Numerical Results: Ventilation of Complexity

Between Transmitter and Receiver

90

PHY delay = (D+D)/2

Numerical Results: Spectrum of One Subcarrier

91

~ 60 dB

Numerical Results: Spectrum of 64 Subcarriers

92

~ 60 dB

Numerical Results: Sensitivity to an Estimation

Error on BdTm

93

Numerical Results: Sensitivity to Synchronization

Errors in Frequency

94

Numerical Results: Sensitivity to Synchronization

Errors in Time

95

38-sample error tolerence

34-sample error tolerence

Conclusion

We proposed a new and straightforward technique for the

systematic optimization of transmit and receive waveforms

for OFDM/FBMC/GFDM systems

Increased SINR

6 orders of magnitude reduction in out-of-band emissions

Robustness to synchronization errors

96

Perspectives

Extension to OFDM/OQAM

Extension to multi-pulse OFDM/QAM and OFDM/OQAM

Extension to single-carrier communications

Extension to underwater acoustic communications

OFDM pulse shapes optimized for partial equalization

OFDM tolerant to bursty communications with relaxed

synchronization

OFDM pulse shapes optimized for carrier aggregation and reduced

out-of band emissions

OFDM pulse shapes optimized for further OFDM pulse shapes

optimized for a lower latency

Optimization of RADAR pulses

97

98

Thank You for Listening

Mohamed SIALA

Ecole Supérieure des Communications de Tunis (SUP’COM)

12th International Multi-Conference on Systems, Signals &

Devices (SSD’2015)

March 16 - 19, 2015 - Mahdia, Tunisia

References 1/4

M. Siala, T. Kurt, and A. Yongaçoglu, “Orthonormalization for Multi-Carrier Transmission,”

Canadian Workshop on Information Theory 2005 (CWIT’05), Montreal, Quebec, Canada, June 2005.

T. Kurt, M. Siala, and A. Yongaçoglu, “Multi-Carrier Signal Shaping Employing Hermite

Functions,” European Signal Processing Conference 2005 (EUSIPCO’05), Antalya, Turkey,

September 2005.

N. Debbabi, M. Siala, and H. Boujemâa, “Optimization of the OFDM Prototype Waveform for

Highly Time and Frequency Dispersive Channels Through a Maximization of the SIR,” 12th

IEEE International Conference on Electronics, Circuits and Systems 2005 (ICECS’05), Gammarth,

Tunisia, December 2005.

A. Ben Salem, M. Siala, and H. Boujemâa, “Performance Comparison of OFDM and

OFDM/OQAM Systems Operating in Highly Time and Frequency Dispersive Radio-Mobile

Channels,” 12th IEEE International Conference on Electronics, Circuits and Systems 2005

(ICECS’05), Gammarth, Tunisia, December 2005.

M. Siala, T. Kurt, and A. Yongaçoglu, “A Unified Framework for the Construction of

OFDM/OQAM Systems,” 12th IEEE International Conference on Electronics, Circuits and Systems

2005 (ICECS’05), Gammarth, Tunisia, December 2005.

99

References 2/4

A. Ben Salem, M. Siala, and H. Boujemâa, “OFDM systems with hexagonal time-frequency

lattices and well time frequency localized prototype functions,” Third International Symposium

on Image/Video Communications over fixed and mobile networks 2006 (ISIVC’06), Hammamet,

Tunisia, September 2006.

M. Siala, “Novel OFDM/OQAM system with hexagonal time-frequency lattice,” Third

International Symposium on Image/Video Communications over fixed and mobile networks

(ISIVC’06), Hammamet, Tunisia, September 2006.

I. Trigui, M. Siala, and H. Boujemâa, “Optimized pulse shaping for OFDM multi-user

communications over doubly dispersive channels,” 9th International Symposium on Signal

Processing and its Applications (ISSPA’07), Sharjah, United Arab Emirates, February 2007.

M. Siala and A. Yongaçoglu, “Prototype waveform optimization for an OFDM/OQAM system

with hexagonal time-frequency lattice structure,” 9th International Symposium on Signal

Processing and its Applications (ISSPA’07), Sharjah, United Arab Emirates, February 2007.

I. Trigui, M. Siala, S. Affes and A. Stephenne, “SIR Optimized Hermite-Based Pulses for BFDM

Systems in Doubly Dispersive Channels,” International Symposium on Signals, Systems and

Electronics (ISSSE’07), Montreal, Quebec, Canada, July 2007.

100

References 3/4

R. Ayadi, I. Kammoun, and M. Siala, “Optimization of the pulse shape of OFDM systems Using

the Arrow-Hurwicz Algorithm,” 4th International Symposium on Wireless Communication

Systems (ISWCS’07), Trondheim, Norway, October 2007.

R. Ayadi, M. Siala, and I. Kammoun, “Transmit/receive pulse-shaping design in BFDM systems

over time-frequency dispersive AWGN channel,” IEEE International Conference on Signal

Processing and Communications (ICSPC’07), Dubai, United Arab Emirates, November 2007.

I. Trigui, M. Siala, S. Affes, A. Stephenne, and H. Boujemaa, “Optimum Pulse Shaping for

OFDM/BFDM Systems Operating in Time Varying Multi-Path Channels,” IEEE Global

Telecommunications Conference (GLOBECOM’07), Washington DC, USA, November 2007.

M. Bellili, M. Siala, and L. Ben Hadj Slama, “Pulse design for maximizing SIR in partially

equalized OFDM/BFDM systems,” IEEE 19th International Symposium on Personal, Indoor and

Mobile Radio Communications (PIMRC’08), Cannes, France, September 2008.

M. Bellili, L. Ben Hadj Slama, and M. Siala, “Multi-pulse/single-pulse design for maximizing SIR

in partially equalized OFDM systems over highly dispersive channels,” 16th IEEE International

Conference on Electronics, Circuits, and Systems, 2009 (ICECS 2009), Hammamet, Tunisia,

December 2009.

101

References 4/4

R. Ayadi, I. Kammoun, and M. Siala, “Optimal OFDM Pulse Design, Analysis and

Implementation Over Doubly Dispersive Channel,” 21st European Signal Processing Conference

(EUSIPCO 2013), Marrakech, Morocco, September 9-13, 2013.

M. Siala, F. Abdelkefi and Z. Hraiech, “Novel Algorithms for Optimal Waveforms Design in

Multicarrier Systems,” IEEE Wireless Communications and Networking Conference

(WCNC’2014), Istanbul, Turkey, April 2014.

Z. Hraiech, M. Siala, and F. Abdelkefi, “Numerical Characterization for Optimal Designed

Waveform to Multicarrier Systems in 5G,” 22nd European Signal Processing Conference 2014

(EUSIPCO 2014), Lisbon, Portugal, 1-5 September 2014.

Z. Hraiech, F. Abdelkefi, and M. Siala, “POPS-OFDM: Ping-pong Optimized Pulse Shaping-

OFDM for 5G systems,” accepted at IEEE International Conference on Communications (ICC’15),

London, UK, June 2015.

Z. Hraiech, F. Abdelkefi, and M. Siala, “POPS-OFDM: Ping-pong Optimized Pulse Shaping-

OFDM for 5G systems,” Accepted at IEEE Vehicular Technology Conference – Spring 2015

(VTC’S15), Glasgow, Scotland, May 2015.

102