Laurent Martinod - FP7 EMPHATIC project: Airbus D&S current view and study

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FP7 EMPHATIC project: Airbus D&S
current view and study
- Current PMR status
- Migration problematic and issues
- FMT evolution on 3GPP LTE scheme
Laurent Martinod
07/01/2015

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PMR legacy systems: actually deployed (Focus on EU case)
The PMR systems considered in EMPhATic project are:
• TETRAPOL:
– It is an AIRBUS proprietary PMR system (RUBIS – 1988).
– It is a digital narrowband system meant mainly for voice and low data rate transmission.
– It is specified in ETSI TETRAPOL PAS
– It is following coexistence constraints as defined in ETSI EN 300 113-1
– TETRAPOL is used mainly in 400 MHz band (380-470 MHz)
• TETRA:
– It is a European PMR standard developed by ETSI (1995).
– It is a digital narrowband system meant mainly for voice and low data rate transmission.
– It is following specifications on coexistence constraints defined in ETSI EN 300 392-2
– TETRA1 (excluding TEDS) is also known as TETRA phase modulation mode
– TETRA system can be used in different UHF bands
– The main band of interest is 400 MHz band (380-470 MHz)
• TEDS (TETRA2):
– It is an evolution of TETRA European ETSI Standard.
– It is a digital wideband system meant for data transmission.
– It is following specifications on coexistence constraints defined in ETSI EN 300 392-2 (same as TETRA)
– TEDS is also known as TETRA QAM modulation mode (multicarrier modulation scheme)
– TEDS system can be used in different UHF bands
– The main band of interest is 400 MHz band (380-470 MHz)
9 March 2015
FP7 EMPHATIC project: Airbus D&S current view and study - FMT scheme
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PMR systems: modulation main characteristics
• TETRAPOL:
– TETRAPOL Radio System can support a 5 MHz bandwidth corresponding to 500 radio channels of 10
kHz or 400 radio channels of 12.5 kHz (channel spacing). The frequency shift between the uplink and
downlink (FDD mode of operation) is constant (duplex spacing): typ. 10 MHz in the UHF band.
– Generally, terminals operate in half-duplex mode
– Transmission is organised in Frames of 160 bits, each Frame being transmitted during a 20 ms Time
Interval (equivalent to 160 modulation symbols) in both directions
– The modulation type is Gaussian Minimum Shift Keying (GMSK), with parameter BT = 0,25
– The modulation rate is 8 kbit/s. Therefore, the period T is 125 μs
• TETRA / TEDS (TETRA2):
– For phase modulation the modulation scheme is π/4-shifted Differential Quaternary Phase Shift Keying
(π/4-DQPSK) or π/8-shifted Differential 8 PSK (π/8-D8PSK)
– The modulation rate is 36 kbit/s for π/4-DQPSK (TETRA1)
– The modulation rate is 54 kbit/s for π/8-D8PSK (specific TEDS 8 states Phase modulation case)
– For QAM (TEDS or TETRA2) the modulation scheme is 4-QAM, 16-QAM or 64-QAM. A multi sub-carrier
approach with 8 sub-carriers per 25 kHz is used, i.e. 8, 16, 32 and 48 sub-carriers in 25 kHz, 50 kHz, 100
kHz and 150 kHz carriers respectively.
– The modulation symbol rate on each sub-carrier is 2 400 symbols/s
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Principal frequency band in Europe
380-385 / 390-395 MHz
10 MHz FDD Duplex
Other sub-bands are defined in 400 MHz band: 410-430 MHz and 450-470 MHz (with same FDD Duplex)
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4
380 385 390 395
PMR Band
UL DL
MHz
10 to 25 kHz
10MHz

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PMR specific needs (services)
Overall system architecture very similar to cell-based public radiocommunication systems
(GSM/…) but:
- Establishment time reduced to minimum
- Group call / conference
- Priority call / preemption
- Emergency call
- E2E encryption (cyphering in the handheld)
- DMO (Direct Mode Operation)
- Push to Talk
- Very low datarate vocoder (down to 2.45kbits/s, ex. AMBE)
- Very wide cell range (proprietary radio network)
- …
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Cell-based radio planning
• High order frequency reuse pattern (> 12)
• Scarcely used spectrum
• Up to 24 channels per radio site
(TTPOL)
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1
2
3
Spectrum used by
NB network in cell
#2
Spectrum used by
NB network in cell
#1
Spectrum used by
NB network in cell
#3
Overall spectrum (Cells 1 to 3)

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PMR specifications: far more stringent requirements
PMR radio specifications and requirements are far more stringent than 3GPP LTE for example
Example of blocking characterisics required
RX: TETRAPOL MS RX Mask LTE 1.4 MHz bandwidth UE RX Mask
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7
Blocking (dB)
0
10
20
30
40
50
60
70
80
90
100
110
-10 -8 -6 -4 -2 0 2 4 6 8 10
Frequency Offset (MHz)
Mask (dBc)
Mask of Blocking Response
0
10
20
30
40
50
60
70
-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16
Frequency Offset (MHz)
Min. Requirement (dBm)
Mask (dB)
ACS 40dB
ACS + NB Blocking 40dB

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Evolutions and context: higher datarates needed
Hence the following important services that are of WB and BB nature cannot be supported by these networks:
• video conferencing;
• video streaming (CCTV on scene);
• full Satellite Navigation (AVLS works well on narrowband but not as comprehensive);
• passport and bio-metric checks (secure information) undertaken remotely as this requires data rates just
above those available on narrowband;
• improved on-line access to contacts data base that can be shared to know all those organisations /
people that should be contacted depending on, for example, the incident;
• full e-mail;
• intranet browsing;
• improved transfer of files (maps and pictures);
• improved transfer of medical information;
• ability to move the back office into the field;
• Increased over the air key programming downloads of new software updates. Allows the staff to be kept
operational which could be a significant cost and operational benefit;
• Biometric monitoring;
• …
9 March 2015
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Evolutions and context: migration towards broadband
These services require much higher data rates than currently deployed PMR PPDR systems.
• Broadband techniques using bandwidths in the range of 1.4, 3, 5 MHz bandwidth such as LTE enable high data
rates transmissions and demanding PPDR data applications.
• It shall be noted that these services have to be provided on dedicated networks in order to ensure the access to
the network even in Disaster conditions when commercial networks are out of order due to congestion.
• The introduction of new broadband PMR technologies for broadband requires new available capacity for such
usage.
There are two ways to increase the capacity:
• Allocate new frequency bands to Public Safety usage (PPDR applications) below 1 GHz for economical
reasons linked to the propagation conditions that are much better in UHF frequency range in order to enable
sufficient territorial coverage with a limited number of Base Stations. Not for tomorrow !
• Improve spectrum efficiency of PMR PPDR systems in the bands that are already allocated to PMR (i.e.
bands for PPDR: 380-385/390-395 MHz, and other bands allocated to PMR: 430-450 MHz band and 450-
470 MHz band). The goal is then to improve broadband technologies and to enable coexistence in the same
band of current (narrowband) technologies and new broadband technologies by inserting broadband in
bands already deployed with narrowband systems and networks.
The objective of EMPHATIC project is to study techniques especially on the lower layer that enable intrinsic
better spectrum efficiency of broadband systems and their cohabitation with narrowband systems in the same
band.
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9 March 2015
BB system introduction into NB world
Typical cases and generic one
10
10

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3GPP LTE as a candidate: this is not straightforward
• CP-OFDM poor spectral containment (high adjacent side-lobes)
• Blanking RBs is not the solution: the spectrum is not cleared
9 March 2015
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Empty RB
LTE constellation
LTE spectrum
Reserved area
3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6
x 106
-60
-40
-20
0
20
40
PSD (dB)
Frequency (Hz)

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Proposed solution: evolved 3GPP LTE Layer 1 using pulse shaping
• Replace CP-OFDM by Filter Bank Multi-Carrier (FBMC) modulation: EMPHATIC purpose
• Our own contribution: FMT usage
• Frequency Multi Tone (FMT) : filter bank composed of non overlapping filters
(or with slight overlapping) – frequency domain
• Main idea: suppress temporal OFDM CP, and use an equivalent guard interval in the
frequency domain
• Iso radio resources, Fs unchanged, frame structure remains identical, …
• Main advantage: spectrum shaping
• Main drawback: temporal support of the pulse shaping function (delay)
9 March 2015
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What could it look like ?
First view and comparison between classical 3GPP LTE and evolved LTE with FMT
implementation
LTE spectrum in blue and FMT LTE spectrum in red
Overall spectrum Zoom on blank sub-carriers
9 March 2015
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FMT characteristics: some maths
• FMT BB signal:
– M is the number of sub-carriers,
– N is the number of modulated symbols on each sub-carrier,
– T is the symbol duration on each sub-carrier
– g(t) is the ideal symbol waveform, obtained by the inverse Fourier transform of a square root raised cosine
spectrum G(f), defined as follows:
– Thus:
9 March 2015
   
 
n
n
n
m
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j
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(n)
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)
(
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 
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14

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3GPP LTE reminder: main PHY parameters (BW definition)
9 March 2015
15

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3GPP LTE DL physical channels reminder
9 March 2015
16

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3GPP LTE and FMT main parameters
• Classical 3GPP LTE figures, and new parameters:
• Goal: keep 3GPP LTE parameters unchanged !
• FMT implementation is transparent for 3GPP upper layers.
9 March 2015
• Configuration parameters • 3GPP LTE Standard + FMT
• Basic modulation access mode • OFDMA (downlink mode)
• Frequency carrier • 450 MHz
• Bandwidth • 1.4 MHz
• FFT size (Nfft) • 128
• Sampling Frequency • 1.92 MHz
• Sub-carrier spacing (∆f) • 15 kHz
• CP • 512/2048=1/4
• Symbol duration • 160 samples: Nfft(1+CP)
• Number of used sub-carriers (N
used
) • 72 (6 RBs)
• Pulse shaping filter size • L*(Nfft+CP))
• Roll-off factor • Alpha Tx / Rx
17

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FMT advantage: spectrum behaviour
example – carrier blanking
• As an example: one subcarrier is dismissed
- Adjacent sub-carrier rejection = -49dB (FMT) vs -10dB (CP-OFDM)
- Pulse shaping filter characteristics: L = 8, alpha = 0.35
9 March 2015
-5.8 -5.6 -5.4 -5.2 -5 -4.8 -4.6 -4.4 -4.2
x 105
-80
-70
-60
-50
-40
-30
-20
-10
0
Frequency
Magnitude (dB)
Filtered LTE signal with blank sub-carrier
OFDM
FMT
Unused OFDM subcarrier
Unused FMT subcarrier
18

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FMT drawback: ICI / limited pulse shaping temporal support
example – EVM at receiver side (no propagation channel)
• Depending on temporal pulse shaping length and truncation, EVM could be not negligible
(ideal case – no propagation channel):
9 March 2015
-1.5 -1 -0.5 0 0.5 1 1.5
-1.5
-1
-0.5
0
0.5
1
1.5
64 QAM symbols, L=6, Alpha= 0.33, EVM=0.041
-1.5 -1 -0.5 0 0.5 1 1.5
-1.5
-1
-0.5
0
0.5
1
1.5
64 QAM symbols, L=7, Alpha=0.33, EVM=0.02
-1.5 -1 -0.5 0 0.5 1 1.5
-1.5
-1
-0.5
0
0.5
1
1.5
64 QAM symbols, L=18, Alpha=0.23, EVM=0.003
19

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FMT: parameters choice (EVM and rejection criteria)
• EVM depending on roll-off factor (asymmetric roll-off factor: Rx / Tx pulse shaping filters)
• Filter length = 12 OFDM symbols (1 LTE sub-frame)
• Optimal point: (AlphaTx: 0.22, AlphaRx: 0.18) => Rejection: 48.7dB, EVM: 1.0%
9 March 2015
alphaTx
alphaRx
EVM with filter length:12, 64QAM, 1 subcarrier removed
0.2 0.25 0.3 0.35 0.4 0.45
0.2
0.25
0.3
0.35
0.4
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.2 0.25 0.3 0.35 0.4 0.45 0.5
43
44
45
46
47
48
49
50
Rejection with filter length:12, 64QAM, 1 subcarrier removed
alphaTx
20

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FMT modulator - basics
9 March 2015
Pulse Shape
Filter h (t)
e
j 
0
t
tx
Subchannel 0
Subchannel
Symbol
Generator
Pulse Shape
Filter h (t)
e
j  t
1
tx
Subchannel 1
Subchannel
Symbol
Generator
Pulse Shape
Filter h (t)
e
j  t
N-1
tx
Subchannel N-1
Subchannel
Symbol
Generator
+
Zero IF
Modulation
Data Input 0
Data Input 1
Data Input N-1
k bits
k bits
k bits
21

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Our FMT implementation: overlap-add in the temporal domain
9 March 2015
IDFT + replication
overlap-add with
previous FMT symbols
M.m bits
bits/ symbols
mapping
M symbols
demultiplexing on M subcarriers
0
M -1
..
.. ..
..
..
.. ..
..
..
.. ..
.. ..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
IDFT
+
replication
time
time
Filter h (t)
tx
Filter h (t)
tx
time
22

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MATLAB LTE / FMT PHY simulation:
overall synoptic (DL case)
• Complete PHY layer simulation available:
Synchronization in time and frequency is perfect !
9 March 2015
Data
bits
CHANNEL CODING
CRC
encoder
Rando-
mizer
FEC
encoder
Inter-
leaver
Rate
mat-
ching
SYMBOL
QAM
mapper
MIMO
MIMO
encoder
BURST MAPPING
PHY-channel
mapping
PN seq.
generator
Pilots
insertion
Frame
structure
OFDM
IFFT
CP
insert.
PROPAGATION CHANNEL
Multiple
paths
Delays
Uncorrelated
fadings
Multiple paths
summation
AWGN
FFT
CP
remove
OFDM
INIT
MIMO decoder
&
Channel
estimation
Channel
compensate
PHY-channel
demapping
Pilots
removal
QAM
Demod.
Received
Data bits
CRC
decoder
Derand-
omizer
FEC
decoder
Deinter-
leaver
Rate
demat-
ching
BER/FER
calculation
+ EVM
FMT
FMT
23

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MATLAB LTE PHY simulation: propagation channel model
What is this for ?
Radio-communications context
Moving UEs
Physical phenomena during propagation
9 March 2015
24
UE#1
Base
Station
UE#2
Cell B
Cell A
A: free space
B: reflection
C: diffraction
D: scattering
E: shadowing
F: Doppler

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MATLAB LTE PHY simulation: propagation channel model
Example of multipath fading channel models:
• HT200: Hilly Terrain environment and 200km/h mobile speed 6 multi-paths with Rayleigh fading channel
and following characteristics
• Representation
in time and frequency plan
(example): amplitude only
• Due to UHF high temporal delay spread
Extended CP configuration case is
mandatory
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25
Path 1 2 3 4 5 6
Delay( s
 ) 0.0 0.1 0.3 0.5 15.0 17.2
Attenuation (dB) 0.0 -1.5 -4.5 -7.5 -8.0 -17.7

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MATLAB 3GPP LTE / FMT PHY simulation:
3GPP LTE DL physical channels overview (reused with FMT scheme)
9 March 2015
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FMT vs LTE simulation results – AWGN SISO
9 March 2015
Perfect channel estimation Real MAP channel estimation
27

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FMT vs LTE simulation results – dynamic EVA 50 SISO
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Perfect channel estimation Real MAP channel estimation

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FMT tests: HPA linearity and spectrum regrowth experiments
Several waveforms generated with the following characteristics and feeding Base Station HPA:
• Fs = 7.68Msamples/s
• No Crest Factor reduction is applied (as a consequence, PAPR is roughly 12dB)
• Modulation = 64QAM
• BW = 1.4MHz (6 RBs)
• Two RBs are blanked
CP-OFDM 3GPP LTE waveform
1st FMT waveform:
L = 6, roll-off = 0.25
(ACP rejection ~ 40dB)
2nd FMT waveform:
L = 12, roll-off = 0.25
(ACP rejection ~ 60dB)
9 March 2015
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FMT tests: HPA linearity and spectrum regrowth experiments
Experiment with real RF hardware
(HPA base station output)
using the 2nd FMT waveform
• blue curve = HPA base station
output (@ max power output
+48dBm ~ 60W)
• black curve = R&S SMU200
output (reference measurement)
We do no need to have
more stringent specifications !
9 March 2015
30

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Confidential
9 March 2015
Thank you for your attention!
Questions ?
31
31

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Laurent Martinod - FP7 EMPHATIC project: Airbus D&S current view and study

Laurent Martinod - FP7 EMPHATIC project: Airbus D&S current view and study

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