This document summarizes the work of a radio-over-fiber research group at the Technical University of Denmark. The group consists of 6 staff members and 12 PhD researchers from 15 different countries. Their work focuses on developing next generation access networks using radio-over-fiber technology. This involves using optical fiber to transmit radio frequency signals from a central office to remote antenna bases. Key challenges include improving receiver sensitivity, reach, and the number of supported users while increasing tolerance to fiber impairments. The group is exploring using phase modulation formats and digital signal processing techniques at the receiver to address these challenges. Their goal is to develop a converged optical network that can transport both wired and wireless signals on a common infrastructure.
3. 3
Team members
Staff (6)
Idelfonso Tafur Monroy, Prof.
Darko Zibar, Assoc. Prof.
Jesper B. Jensen, Asst. Prof.
J.J.Vegas Olmos, Asst. Prof.
Antonio Caballero, Postdoc
PhD Researchers (12 )
Cyd Delgado
Jose Estaran
Bomin Li
Valeria Arlunno
Xiaodan Pang
Alexander Lebedev
Maisara Othman
Roberto Rodes
Tien Thang Pham
Robert Borkowski
Supannee Learkthanakhachon
Gerson de Los Santos
A Copenhagen based, young and dynamic team, that combines
diversity in expertise and cultural backgrounds (15 nationalities)
Ongoing MSc students projects
(6)
David Montero, visit. Asst.
Prof.
4. 4
Next generation access networks services
Central Office
PSTN
Internet
Private Home with
Small Repeater
Mobile access
Wireless
Stuff
Wireless
Access in
the City
Requirements:
• Versatile – handle a variety of signals
• Efficient bandwidth utilization
• Bidirectional
• Dynamic and reconfigurable
• Long-reach (~100 km)
5. 5
Hybrid fiber wireless networks
CO
Service integration
Unified optical
network platform
Different
modulation
formats
BS
Different
bit rates
Radio over fiber (RoF) technology to increase
the capacity, coverage and mobility
Challenges:
• Integration with existing infrastructures
• Fulfill optical power budget
• Increase receiver sensitivity, reach and number of
users
• Improve the tolerance to fiber transmission
impairments
• Perform signal detection and demodulation of
different modulation formats and bit rates
6. 6
Where? Network scenario1
[1] Alcatel Radio-over-Fibre solution, 2007
Convergence between fixed and wireless networks the goal to bring the
bandwidth of fixed network to mobile user
7. 7
To take into account: Global data traffic
1 Exabyte = 1018 bytes
Drivers for traffic growth
Mobility
Cloud
Video
From CISCO analysis
10. 10
100 Gbit/s wireless links
Bring the capacity of baseband optical links to
wireless links
1988 1992 1996 2000 2004 2008 2012
10Mbps
100Mbps
1Gbps
10Gbps
100Gbps
W
ireless
links
(standard
W
LAN)
W
ireless links (research)
Optical serial interface (products)
Bitrate
Year
Optical serial interface (research)
11. 11
How to achieve multi gigabit wireless links
Higher RF carrier frequencies
• GHz of bandwidth available
• Higher Air attenuation
Courtesy of J. Mitchell, UCL1
Frequency (GHz)
10
GSM
900MHz
1800MHz
UMTS
~2GHz
WLAN
2.4GHz
5.1GHz
LMDS
28GHz
29GHz
31GHz
HiperAccess
18GHz
42GHz
MVDS
40GHz
WIMAX
2.5GHz
3.5GHz
802.20
~3.5GHz
UWB
3.1-10.6 GHz
Wireless HD
60GHz
6040 75 110
Future gigabit
links
Advanced modulation techniques
• High spectral efficiency
• Stringent requirements on
linearity and SNR
12. 12
How to achieve multi gigabit wireless links
75-110GHz
An untapped
frequency band
1 100 500
Wireless HD
60GHz
Saturated frequency bands (i.e
GSM, UMTS, WiFi, WiMAX, WLAN, U
WB, HiperAccess, LMDS, MVDS...)
Frequency
(GHz)
300-
500GHz
Augmented reality
HD Video Streaming
Interactive Apps
3D Skype on ipads
Mobile e-Health
Machine-to-machine
synch and go
Disaster recovery
Need for wireless bandwidth beyond current up to 10 GHz bands
13. 13
BTS Coverage vs Distributed Antenna Systems
DAS approach
•DAS attributes:
•Centralization of complex equipment and simple remote antennas
•Handover and load distribution/re-configurability
•Power consumption
BTS
BTS
BTS: base transceiver station
14. TU Dresden
Communications Laboratory
C.G. Schaeffer DTU Feb. 2009
Why Fibre Optics in Radio Systems ?
numerous lowcost base stations
without RF oscillators & modulators
with superior RF properties
higher RF carriers:
- reduced cell-size
- more subscribers per area
- frequency-reuse
- reduced RF power (EMI)
low fibre attenuation for
feeding the base stations
remote optical generation
of RF carriers
broadband data signals
15. 15
Radio over fibre: basics
Baseband
Intermedeiate
frequency (IF)
up-conversion
Frequency
up-
conversion
GHz
E/O
conversion
Light source
Optical spectrum
THz
Optical spectrum
fo fo
fr
fr
RF spectrum
Intensity modulaiton
THz
Optical fiber link
Radio transmitter
Radio-over-fibre
16. TU Dresden
Communications Laboratory
C.G. Schaeffer DTU Feb. 2009
Intensity Modulation & Direct Detection
Optical
Receiver
Optical to RF
Optical Fibre
RF
Output
RF Input
Optical
Transmitter
RF to Optical
Optical Power Spectrum
Optical
Frequency
RF-Components contributing
to fRF
fRF
f0
Phase sensitive
summation of all
optically generated
RF-Components at fRF
19. TU Dresden
Communications Laboratory
C.G. Schaeffer DTU Feb. 2009
Intensity Modulation & Fibre
Dispersion
Fibre length L (km)
Periodical RF power transfer:
Fibre Dispersion:
Wavelength:
Velocity of Light:
D
ps
km nm
17
1540nm
c
m
s
3 108
222
cos f
c
DL
0 2 4 6 8
60 GHz
40 GHz
1
0.5
Opt. power
Fundamental
3-dB frequency:
DL
c
f dB
2
1
3
27. 27
Hybrid wireless-fibre systems
To metropolitan
network
Central
office
Antenna
base station:
: Optical fibre
Goal: Unified optical wireline and wireless signal transport systems
Coherent detection and DSP All-optical envelope detection
Approaches under study
Recovery &
protection Broadband
wireless bridge
Optical
fiber link
Optical
fiber link
28. 28
All-optical envelope detection for wireless
signals
Modulation
(envelope)
DC Bias
EAM
Radio-frequency carrier
Outputopticalpower
- Vbias
Half-wave
rectified signal
Lightwave carrier
Base station
Envelope
detector
Baseband
data out
•No High frequency mixers and
oscillators
•No frequency and bandwidth fixed
operation
For high carrier frequencies and
large bandwidth reduced
complexity is desirable
Envelope detection with
straightforward connectivity to
fiber links is an interesting
approach
29. 29
All-optical envelope detection
Example: upstream channel EPON
Desirable to use same technology for both wireline and wireless
Key enabling techniques based on all-optical wireless-to-optical
conversion
30. 30
Challenges/potential
Why optical phase-modulation?
0
0.5
1
Transmission
MZ phase (rad)
100%
0
2
4
6
0 0.5 1 1.5 2
Outputphase(rad)
Drive signal (V)
600%
(equivalent)
Linearity:
• Optical intensity modulators nonlinear
Mach-Zehnder – sinusoidal
EAM – exponential
• Optical phase linear
If dominated by linear electro-optic effect
Phase-modulation has no fundamental limit on the dynamic range.
Large dynamic range enabling wide range of power levels
31. 31
Nonlinear and linear optical phase demodulation
0
0.5
1
Transmission
MZ phase (rad)
Photocurrent
Signal – LO phase difference
Large-signal
Modulation
•Open loop
•Closed loop
signal
LO
i~sin( signal - LO)
• Sinusoidal response of the receiver
Benefits of linear phase-modulation lost
90o
optical hybrid
LO
Signal in I(t)
Q(t)
Y(t)= I(t)+jQ(t)=exp( (t))exp( (t))
Linear phase demodulation
32. 32
Converged fixed and wireless network
Central office
Metropolitan network
CWlaser
Analog-to-digital
conversion
RFcarrierrecovery
Lineardemodulation
Digitalcarrierrecovery
Digital coherent receiver
LO laserc
Transmitter
Phase
modulator
b
Photonic wireless-wireline
converged network
a
Carrier recovery and demodulation performed using DSP
larger tolerances to phase noise and impairment compensation using DSP
Same receiver structure for fixed and wireless signal detection
OPSCODER project
33. 33 33
Radio over fiber (RoF) systems
Phase-modulated (PM) RoF systems
38. 38 38
The basis:Analog-to-Digital
Converter
DigitalSignal
Processing
1. DPLL
2. Linear demodulator
3. RF signal demodulation
0
( ) 2 Re ( ) j t
Basebanddata t S t e
Complex baseband representation
0
( ) 2 Re ( ) j t
Basebanddata t S t e
Frequency downconversion
Quadrature demodulator
Synchronizer
40. 40 40
The basis: problem statement
Phase offset
( ) kj
k Baseband ky s k e
Noise
41. 41
41
Classical solution: Viterbi and Viterbi
( ) kj
k Baseband ky s k e
2
( )
( ) ( ) ( )
l
j
M
Baseband I Qs k s t js t e
2
( )
( ) ( ) ( )
l
j
M
Baseband I Qs k s t js t e
4MQPSK
2
( )
(2 )
( ) 1
l
j M
M j lM
Basebands k e e
2
( )
(2 )
( ) 1
l
j M
M j lM
Basebands k e e
No data
(Non-data-aided)
42. 42
Classical solution: Viterbi and Viterbi
2
( )
(2 )
( ) 1
l
j M
M j lM
Basebands k e e
No data
(Non-data-aided)
( ) kjMM M M
k Baseband ky s k e
Objective function( ) Re kjMM
k k
k
L y eexp[ ]kjM M
k
k
e j y It is maximized
for one phasor
ky ( )kF y
arg( )ky
(.)
k
1
arg(.)
M
M
ky
• How to recover the phase of multi-amplitude
signals?
• How to estimate other data signal parameters such
as modulation format?
• How to track time-varying data transmission
conditions?
43. 43
A novel point of view: data clustering
Phase offset
K-means
clustering
Cluster
Centroid
• Phase offset estimation and compensation
• Reconfigurable phase offset estimation
• Modulation format recognition
• Frequency offset compensation
45. 45
RF phase recovery:
Flexible configuration and simple upgrade for
supporting different modulation formats
Cluster
Prototype
Phase
compensation
Symbol 3
Symbol 4
Symbol 5
Symbol 6
Symbol 7
Symbol 8
Symbol 1
Symbol 2
Demodulation
46. 46
12 14 16 18 20 22
4
3
2
B2B, Viterbi & Viterbi
B2B, k-means
40 Km, Viterbi & Viterbi
40 Km, k-means
-log(BER)
OSNR [dB]
1 dB
312.5 Mbaud 8PSK single carrier at 5 GHz
Viterbi and Viterbi vs. K-means:
K-means performs equally well as
Viterbi and Viterbi
48. 48
Automatic modulation format detection:
Level threshold
Level 1
Level 2
Level 3
Multilevel detection
Centroid k
Cluster
dmin(k,j+1)
dmin(k,j)
Centroid
k+2
dmin(k+2,j)
dmin(k+2,j+1)
Centroid
minvar( ( , ) )s d k j
Condition of symmetry
Signal
Histogram/
K-means clustering
Number of
levels/
Number of
clusters
Multilevel?/
Symmetry?
Right
16QAM/8PSK/
QPSK Signal
Format
Recognition
K-means
Re-initialization
AMFD process
Reconfigurable
CarrierRecovery
Wrong
49. 49
Automatic modulation format detection:
Centroid k
Cluster
dmin(k,j+1)
dmin(k,j)
Centroid
k+2
dmin(k+2,j)
dmin(k+2,j+1)
Centroid
minvar( ( , ) )s d k j
Condition of symmetry
100 1000
0,000
0,001
0,002
0,003
0,004
0,005
0,006
0,007
Symmetry
Data samples
OSNR 20 dB
OSNR 24 dB
Threshold
QPSK 8PSK
0,000
0,005
0,010
0,015
0,020
Threshold
Hypothesis
Wrong QPSK id.
Symmetry
True QPSK id.
Truedetection
Wrongdetection
200 data-samples are required for
automatic modulation format detection
Modulation format = 8PSK
50. 50
Frequency offset compensation:
The reconfigurable k-means clustering
algorithm allows multifunctional tasks
Frequency offset
effect
N samples
First N/2
samples
Second N/2
samples
Cluster
Centroid
Blue
constellation
rotation by
(1: )cleary N
( 1: 2 )darky N N
51. 51
Frequency offset compensation:
The reconfigurable k-means clustering
algorithm allows multifunctional tasks
12 13 14 15 16 17 18 19 20 21 22
4
3
2
Without frequency offset compensation
With frequency offset compensation
-log(BER)
OSNR [dB]
2.7 dB
1200 1100 1000 900 800 700 600
4
3
OSNR 22 dB
OSNR 20 dB
-log(BER) Data-symbols / time-blocks
Frequency offset 10 kHz
a) b)
312.5 Mbaud 8PSK single carrier at 5 GHz
60. 60
-26 -25 -24 -23 -22 -21 -20
5
4
3
2
B2B single channel
78km single channel
-log(BER)
Received Power [dBm]
Coherent VCSEL(a)
-26 -25 -24 -23 -22 -21 -20
5
4
3
2
B2B single channel
78km single channel
78km all wavelengths
-log(BER)
Received Power [dBm]
Coherent VCSEL(a)
No penalty for
multichannel
case
61. 61
-30 -29 -28 -27 -26
4
3
2
B2B single channel
78km single channel-log(BER)
Received Power [dBm]
(b) QPSK
-30 -29 -28 -27 -26
4
3
2
B2B single channel
B2B all wavelengths
78km single channel
78km all wavelengths
-log(BER)
Received Power [dBm]
(b) QPSK
0.5 dB penalty
for multichannel
case
62. 62
-26 -24 -22 -20 -18
5
4
3
2
1
B2B single channel
B2B all wavelengths
78km single channel
78km all wavelengths
-log(BER)
Received Power [dBm]
(c) IR-UWB
-26 -24 -22 -20 -18
5
4
3
2
1
B2B single channel
78km single channel
-log(BER)
Received Power [dBm]
(c) IR-UWB
No penalty for
multichannel
case
63. 63
-32 -31 -30 -29 -28 -27
5
4
3
2
B2B single channel
78 km single channel
-log(BER)
Received Power [dBm]
(d) OFDM RoF
-32 -31 -30 -29 -28 -27
5
4
3
2
B2B single channel
B2B all wavelengths
78 km single channel
78 km all wavelengths
-log(BER)
Received Power [dBm]
(d) OFDM RoF
No penalty for
multichannel
case
64. 64
Receiver sensitivity:
• -24 dBm for directly modulated VCSEL
• -27 dBm for QPSK baseband
• -23 dBm for phase-modulated IR-UWB
• -27.5 dBm for phase-modulated OFDM
65. 65
PM-OFDM
Baseband
VCSEL
AWG
AWG
78 km
Deployed Fiber
EDFA
20mW
PPG
DATA DATA /
MZM
/2
CW
PPG
DATA DATA /
VOA
10 dB
1
2
4
IR-UWB
AWG
TLS
M
3
Single Coherent Receiver
10 dBVOA
90°Optical
Hybrid
PwrMn
LO
1 2 3 4
VCSEL
DigitalPhotonic
Receiver
DSO
Serial-Parallel
Mapper
IFFT
CP
DATAIN
AWG
VSG
CW
M
1 m wireless
transmission
Summary:
• Successful WDM signal demodulation for all
four subsystems was demonstrated
• 78 km of optical fiber transmission was
achieved
• A BER value below FEC threshold was
achieved for all four subsystems
66. 100 Gbps Wireless Link in 75-110 GHz
Band Using Photonic Technologies
67. 67 DTU Fotonik, Danmarks Tekniske Universitet
Applications to gigabit wireless links
• Sync and go
• All wireless connectivity at business and home
• HD video streaming (uncompressed)
• Cloud computing
• Video-calls
http://wirelessgigabitalliance.org/
• Beyond LTE Cellular networks
• Disaster recovery links
• Fast deployment wireless networks
• Extension of optical fiber links
Optical fiber
Optical fiber
Optical fiber
68. 68 DTU Fotonik, Danmarks Tekniske Universitet
Principle of RF generation by optical heterodyning
•High capacity optical baseband generation
•Incoherent beating of the lasers at the PD
•Stringent requirement on laser linewidth
•Scalable to high RF frequencies
[1] U. Gliese et al., MTT 1998
[2] I. Insua et al., OFC 2009
[3] R. Sambaraju et al., PTL 2010
[4] D. Zibar et al., PTL 2011
69. 69 DTU Fotonik, Danmarks Tekniske Universitet
Ƭ
16-QAM Optical Baseband
Transmitter
PolMux
Emulator
Heterodyne
Upconversion
PC X
Y XX
Y Y
W-band
LNA
EDFA
x2
LO
37 GHz
75–110 GHz
1551.6nm
1550.9
nm
LO
PD212.5 Gb/s
PPG
Ƭ
80GS/sADC
Downconversion
I/QSeparation
TimingOffsetRecovery
DecisionandBERTest
Equalizer
Receiver
π/2
87.5 GHz
1550.9 1551.6
PD1
d
X
Y
36cm
6dB
Ƭ
6dB
Ƭ
Experimental Setup
•Optical baseband 16-QAM generation using binary signal generator
•Free running ECL (100 kHz linewidth) as LO for photonic up-conversion
•Double-stage down-conversion:
1. Electrically W-band to 1-26GHz;
2. Digitally from 1-26 GHz to baseband
16-QAM Optical Baseband
Transmitter
PC
1550.9
nm
12.5 Gb/s
PPG
Ƭ
π/2
6dB
Ƭ
6dB
Ƭ
16-QAM Optical Baseband
Transmitter
PC
1550.9
nm
12.5 Gb/s
PPG
Ƭ
π/2
6dB
Ƭ
6dB
Ƭ
Ƭ
PolMux
Emulator
X
Y
Ƭ
PolMux
Emulator
X
Y
Heterodyne
Upconversion
XX
Y Y
1551.6nm
LO
PD2
PD1
X
Y
Heterodyne
Upconversion
XX
Y Y
1551.6nm
LO
PD2
PD1
X
Y
EDFA
W-band
LNA
x2
LO
37 GHz
80GS/sADC
Downconversion
I/QSeparation
TimingOffsetRecovery
DecisionandBERTest
Equalizer
Receiver
W-band
LNA
x2
LO
37 GHz
80GS/sADC
Downconversion
I/QSeparation
TimingOffsetRecovery
DecisionandBERTest
Equalizer
Receiver
87.5 GHz
1550.9 1551.6
70. 70 DTU Fotonik, Danmarks Tekniske Universitet
Experiment Setup
• For information:
– Both signal laser and LO laser has ~100 kHz linewidth, but drifting
fast within the range of 300 MHz;
– Signal and LO power are set to be equal;
– W-band LNA has 25 dB gain, max input power = -20 dBm;
– W-band Mixer is driven by LO at 74 GHz. With input RF with
frequency between 75-100 GHz, the output IF lies in the frequency
range 1-26 GHz;
71. 71 DTU Fotonik, Danmarks Tekniske Universitet
Experiment Setup
W-band
Antenna
100 GHz
PD
W1-WR10
Adaptor
W-band
Antenna
W-band
LNA
W-band
Mixer
LO
IF
72. 72 DTU Fotonik, Danmarks Tekniske Universitet
Experiment results
-1 0 1 2 3 4 5 6 7 8 9 10
5
4
3
2
1
Wireless d = 50cm
Wireless d = 150cm
Wireless d = 200cm
-log(BER)
Optical power into PD (dBm)
FEC
50 Gbit/s
•BER curves for 50 Gbit/s single
polarization 16-QAM with different
wireless distances
-1 0 1 2 3 4 5 6 7 8 9
5
4
3
2
1
Wireless d = 50 cm
Wireless d = 75 cm
Wireless d = 120 cm
-log(BER)
Optical power into PD (dBm)
FEC
100 Gbit/s
•BER curves for 100 Gbit/s PolMux
16-QAM with different wireless
distances
-1 0 1 2 3 4 5 6 7 8 9 10
5
4
3
2
1
Wireless d = 50cm
-log(BER)
Optical power into PD (dBm)
FEC
50 Gbit/s
-1 0 1 2 3 4 5 6 7 8 9 10
5
4
3
2
1
Wireless d = 50cm
Wireless d = 150cm
-log(BER)
Optical power into PD (dBm)
FEC
50 Gbit/s
-1 0 1 2 3 4 5 6 7 8 9
5
4
3
2
1
Wireless d = 50 cm
-log(BER)
Optical power into PD (dBm)
FEC
100 Gbit/s
-1 0 1 2 3 4 5 6 7 8 9
5
4
3
2
1
Wireless d = 50 cm
Wireless d = 75 cm
-log(BER)
Optical power into PD (dBm)
FEC
100 Gbit/s
73. 73 DTU Fotonik, Danmarks Tekniske Universitet
Experiment results
Ƭ
16-QAM Optical Baseband
Transmitter
PolMux
Emulator
Heterodyne
Upconversion
PC X
Y XX
Y Y
W-band
LNA
EDFA
x2
LO
37 GHz
75–110 GHz
1551.6nm
1550.9
nm
LO
PD212.5 Gb/s
PPG
Ƭ
80GS/sADC
Downconversion
I/QSeparation
TimingOffsetRecovery
DecisionandBERTest
Equalizer
Receiver
π/2
87.5 GHz
1550.9 1551.6
PD1
d
X
Y
36cm
6dB
Ƭ
6dB
Ƭ
X branch Y branch
X branch
Y branch
Constellations for 100 Gbit/s PolMux 16-QAM signal
•120 cm wireless distance
•8 dBm optical power into the photodiode
74. 74
Introduction to MIMO technique
1. If all Tx antennas transmits the same
data:
• Increase SNR
• Robust against physical disaster
2. If each Tx antenna transmits different
data simultaneously:
• Increase link capacity
• Diversity
75. 75
Training-based MIMO channel estimation
1t ,0
T
XT
2 Yt 0,
T
T
Time
X
Y
Training period Training period
DATATX
TY
TX
TY
t1 t2
DATA
DATA
DATA
x1 2 1
1 2 2
0
0
xx yX X
Y Y xy yy
RT RT T
RT RT T
h h
h h
x 1 1 2 2
1 1 2 2
xx y X X
Y Yxy yy
RT T RT T
RT T RT T
h h
h h
Channel transfer
matrix derived
Pros
Simple expression
Cons
Required synchronization
Reduced the spectral efficiency due to the overhead
77. 77
MIMO-OFDM WDM PON with DM-VCSEL
Various separationVarious distance
Successfully demodulated below the FEC limit over 7%
overhead
198.5 Mb/s net data rate with 5.65 GHz
Training symbols compensate for impairments in wireless link
78. 78
Experimental Setup of 2x2 MIMO-OFDM
Fiber-Wireless transmission system based
on PDM technique
79. 79
2x2 MIMO-OFDM Fiber-Wireless
Transmission System Based on PDM
Technique
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4
5
4
3
2
1
Pol-x 22.8km SMF d=1m
Pol-y 22.8km SMF d=1m
Pol-x 22.8km SMF d=2m
Pol-y 22.8km SMF d=2m
Pol-x 22.8km SMF d=3m
Pol-y 22.8km SMF d=3m
-log(BER)
Received optical power at PD [dBm]
FEC
-1
1
-1 1
-1
1
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4
5
4
3
2
1
Pol-x QPSK 22.8km SMF d=1m
Pol-y QPSK 22.8km SMF d=1m
Pol-x 16QAM 22.8km SMF d=1m
Pol-y 16QAM 22.8km SMF d=1m
-log(BER)
Received optical power at PD [dBm]
FEC
-3 -1 1 3
-3
-1
1
3
-3
-1
1
3
4-QAM-OFDM 797 Mb/s
16-QAM-OFDM 1.5 Gb/s
Training symbols compensate the optical polarization rotation
and crosstalk in the wireless link
80. Find out more, videos of experiments,…
metroaccessgroup
idtm@fotonik.dtu.dk
We look for:
Researchers exchange & collaboration
EU Marie Curie postdoc grant applicants, August 2013
MSc & PhD studies and research stays
82. 82
Conclusions of MIMO RoF
• Increase link capacity
• Channel estimation algorithm effectively
compensate for impairments in the wireless link
• VCSELs are an alternative optical source for
next generation access networks
• PDM alternative solution to double the capacity
• High potential for future in-door networks
system supporting gigabit/s wireless service
Hinweis der Redaktion
In the central office (CO), two different real valued 64-subcarrier 4-QAM OFDM baseband signals with 198.5 Mb/s net data rate (excluding the training symbols) and 312 MHz of bandwidth are generated by an arbitrary waveform generator (ArbWaveGen). The OFDM symbols are arranged in frames of 10 symbols. The first 3 symbols implement the trainingsequence, and 10% cyclicprefix is added. A dualchannel baseband MIMO-OFDM signal is generated in the ArbWaveGen, which is thenup-converted to a 5.65 GHz radio frequency (RF) carrier; the signal in one arm is up-convertedusing a mixer and the other arm implements RF up-conversionusing the vector signal generator (VSG).