Download - Software Defined Radio and Cognitive Radio:
Software Defined Radio and Cognitive Radio: Implementations & Test-Beds
Alexander M. Wyglinski, Ph.D.
Associate Professor of Electrical and Computer Engineering
IEEE Vehicular Technology Society Distinguished Lecturer
Worcester Polytechnic Institute
Presentation Outline
• Introduction
• The Information Age
• Wireless Innovation Laboratory
• Spectrally Agile Waveforms
• SDR and CubeSats
• Concluding Remarks
• More Information
Introduction
Worcester Polytechnic Institute
Definition: Cognitive radio
A cognitive radio is a kind of two-way radio that automatically changes its transmission or reception parameters, in such a way that the entire wireless communication network - of which it is a node -communicates efficiently, while avoiding interference with licensed or unlicensed users.
A cognitive radio, as defined by the researchers at Virginia Polytechnic Institute and State University, is "a software defined radio with a cognitive engine brain".
http://en.wikipedia.org/wiki/Cognitive_radio
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So what is Cognitive Radio?
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Intelligence
Optim
izat
ion
Adaptation
Environmental Awareness
AgileFlexible
Spectrally Efficient
Learning
Cooperative
Op
po
rtu
nis
tic
Autonomous
Dynamic Spectrum Access
Cognitive radio means …
The Information Age
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Several Key Innovators
Marconi Shannon ShockleyBardeen Brittain
Wireless Transmission
Digital Communications
Transistors
Source: Wikipedia
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Progress of Technology
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Evolution of Wireless Systems“C
ognitiv
e Rad
io C
om
munic
atio
ns
and N
etw
ork
s: P
rinci
ple
s an
d P
ract
ice”
By
A.
M.
Wyg
linsk
i, M
. N
ekove
e, Y
. T.
Hou (
Els
evie
r, D
ecem
ber
2009)
Worcester Polytechnic Institute
Quick Survey
How many of you:─Own a cell phone?─Use a laptop with WiFi?─Use an ATM?─Fly on a plane?─Traveled in a car?
11
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Increasing Demand262 Million Subscribers!
Source: CTIA
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Increasing Demand
1.1 Trillion Minutes!
Source: CTIA
Worcester Polytechnic Institute
US Spectrum Scarcity!
So
urc
e:
NT
IA
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Across the Pond in the UK!
So
urc
e:
Ro
ke M
an
or
Worcester Polytechnic Institute
Oh Canada!S
ou
rce:
Ind
ust
ry C
an
ad
a
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Apparent Scarcity
• Measurement studies have shown that in both the time and frequency domains that spectrum is underutilized
Spectrum measurement across the 900 kHz –1 GHz band (Lawrence, KS, USA)
Spectrum Holes
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Potential Solution
Spectrum measurement across the 900 kHz –1 GHz band (Lawrence, KS, USA)
• Dynamic Spectrum Access (DSA)
Fill with secondary
users
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Enabling Transmission Agility
PROGRAMMABLE FIXED
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Sample SDR Platforms
Universal Software Radio Peripheral 2 (USRP2) Unit.
COSMIAC FPGA board currently being retrofitted for better memory access, to add USB functionality and
to make the board SPA compatible.
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Mitola & Cognitive Radio
Mitola
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Cognitive Radio: A Black Box Model
What you want
What you see
What you can do
What you can tune
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Flexible RF Front Ends Needed
88 MHz
5.8 GHz
Can I do this with just one
RF front end?
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RF MEMS Can Help!
• A single RF front end would not normally be able to support a very wide frequency range of operations─ Radio Frequency
Micro-Electro-Mechanical Systems (RF MEMS) can be used to “tune” the RF front end to the corresponding frequency Source: Wireless ICs and MEMS
Laboratory, McGill University
Close-Up of MEMS Tunable LC Filter.
CapacitorInductor
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RF MEMS
• RF MEMS can be used to implement:─ Antennas (e.g., fractal antennas)─ Filters (e.g., tunable RF bandpass filters)─ Oscillators
• Real-time operations very difficult to support─ Time needed to physically change configurations on the
order of seconds Compared to the rate at which data is transmitted, this is
considered to be ages!
Wireless Innovation Laboratory
Worcester Polytechnic Institute
• Associate Professor, WPI ECE
• Director, Wireless Innovation Laboratory─ 8 Ph.D. students, 5 M.S. students
• Distinguished Lecturer, IEEE Vehicular Technology Society (2012-2014)
• Technical Editor, IEEE Communications Magazine
• Editor, IEEE Transactions on Wireless Communications
• General Co-Chair, IEEE VTC 2015-Fall (Boston, MA, USA)
• ~35 journal publications, ~75 conference papers, 9 book chapters, 2 books
• Served or is serving as PI/co-PI for several federal and industrial grants
Who is Alex Wyglinski?
Worcester Polytechnic Institute
~60 km
Where is WPI?
Worcester Polytechnic Institute
• Founded in 1865; 3rd oldest US polytechnic
─ Model for most engineering schools in US
─ Nationally ranked as 64th Best College in U.S. (2011 US News Rankings)
─ Voted one of the Top 10 Best U.S. Colleges for “Young Einsteins” by Unigo (together with MIT, CalTech, Princeton, Dartmouth, Stanford, Johns Hopkins, Case Western, Georgia Tech, and Cornell)
• 3800 students & 220 faculty─ ECE: 318 undegraduate, 250
graduate, 21 faculty
What is WPI?
Worcester Polytechnic Institute
What is “Lehr und Kunst”?
• Project-based education at the core of “The WPI Plan”
• Many ECE students conduct their senior capstone design projects (called “Major Qualifying Projects”or MQPs) at off-campus locations:─ MIT Lincoln Laboratory─ MITRE (Bedford Campus)─ General Dynamics (Groton Campus)─ Silicon Valley─ Wall Street─ Etc …
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Wireless Innovation Laboratory
• 2 USRP (Version 1) software-defined radio platforms
• 14 USRP (Version 2) software-defined radio platforms
• 15 USRP (Version N210) software-defined radio platforms
• 1 Agilent CSA N1996A 0-3 GHz spectrum analyzer (with battery packs)
• 1 Mini-discone antenna (100 – 1600 MHz, with 3’ tripod)
• 1 WG horn antenna (0.7 – 18.0 GHz, with tripod)
• 1 Xilinx Virtex 5 HW-V5-ML506-UNI-G Prototyping Board
• 25 complete licenses of MATLAB and Simulink with associated toolboxes and blocksets
• 2 OPNET licenses
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WI Lab External Sponsorship
Worcester Polytechnic Institute
SDR Activities at WPI
Photograph of a supervised laboratory session for ECE4305 “Software-Defined
Radio Systems and Analysis” during February 2011.
Screen capture of a functioning ECE4305 course design project in MATLAB showing four SDR units
forming an ad hoc wireless network.
http://www.sdr.wpi.edu/
Spectrally Agile Waveforms
Worcester Polytechnic Institute
Opportunistic Spectrum Access
• Opportunistic spectrum access (OSA) is a significant paradigm shift in the way wireless spectrum is accessed─ Instead of PUs possessing exclusive access to licensed
spectrum, SUs can temporarily borrow unoccupied frequency bands
─ SUs must respect the incumbent rights of the PUs with respect to their licensed spectrum
• OSA enables greater spectral efficiency and facilitates greater user and bandwidth capacity
Worcester Polytechnic Institute
• The utilization efficiency of “prime” wireless spectrum has been shown to be poor
A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548)
OSA Motivation
A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.
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Worcester Polytechnic Institute
Leveraging the Electrospace
Several dimensions of the electrospace include space, time,
and frequency, although there do
exist others such as code, polarization,
and directional.
“Cognitiv
e Rad
io C
om
munic
atio
ns
and N
etw
ork
s: P
rinci
ple
s an
d P
ract
ice”
By
A.
M.
Wyg
linsk
i, M
. N
ekove
e, Y
. T.
Hou (
Els
evie
r, D
ecem
ber
2009)
Worcester Polytechnic Institute
Several Possible Approaches
• Secondary transmission in licensed spectrum can be classified into three categories:– Cooperative Approach
• Primary and secondary users coordinate with each other regarding spectrum usage
– Underlay Approach• Secondary signals transmitted at very low power
spectral density; undetected by primary users• e.g., ultra wideband (UWB)
– Overlay Systems• Secondary signals fill in the spectrum unoccupied by
primary users
Worcester Polytechnic Institute
Spectral Opportunities!
A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548)
A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.
empty empty emptyempty
Worcester Polytechnic Institute
Underlay Solution
A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548)
A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.
underlay transmissions
Worcester Polytechnic Institute
Overlay Solution
A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548)
A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.
overlay transmissions
Worcester Polytechnic Institute
Multicarrier-Based OSA
• Multicarrier modulation is a variant of the conventional frequency division multiplexing (FDM)─ Orthogonal Frequency Division Multiplexing
(OFDM) an efficient form of multicarrier modulation
• In order to utilize unused portions of licensed spectrum, several subcarriers can be turned OFF to avoid interfering with the primary signals
• Each subcarrier experiences flat-fading and hence high data-rates are possible if several unused bands of secondary spectrum are available
Worcester Polytechnic Institute
Multicarrier Overlay Solution
A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548)
A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.
multicarrier overlay transmissions
Worcester Polytechnic Institute
Spectral Agility In Action!
PU signal!
multicarrier overlay SU transmission wraps around PU
As seen in this close-up of the multicarrier overlay transmission, subcarriers located within the vicinity of
a PU can be deactivated in order to avoid interference
with that signal.
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Spectrally Agile Multicarrier
H.
Boguck
a, A
. M
. W
yglin
ski, S
. Pa
gadar
ai, A
. Klik
s. “
Spec
trally
Agile
Multic
arr
ier
Wav
eform
s fo
r O
pport
unis
tic
Wirel
ess
Acc
ess”
. IE
EE C
om
munic
atio
ns
Mag
azin
e, J
une
2011.
Worcester Polytechnic Institute
Major Issue: Out-of-band Emission
• Out-of-band (OOB) interference problem with OFDM-based cognitive radios
• Power spectral density of the transmit signal over one subcarrier:
• Mean relative interference to a neighboring legacy system subband:
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Sinc Pulses Have High OOB Levels!
-6 -4 -2 0 1 2 4 6-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
Subcarrier Index
Nor
mal
ized
pow
er s
pect
rum
(in
dB
) OFDM carrier spacing
Interference power to the first adjacent
sub-band
−10 −5 0 5 10 15 20 25 30
0
0.5
1
Other
Transmissions
Other
Transmissions
Other
Transmissions
Subcarrier index
Nor
mal
ized
am
plitu
de
−10 −5 0 5 10 15 20 25 30
−60
−40
−20
0
Subcarrier index
Nor
mal
ized
pow
er in
dB
m
OtherTransmissions
OtherTransmissions
OtherTransmissions
OOB
OOB
Worcester Polytechnic Institute
Several Solutions
• Cancellation Carriers─ Non-data bearing subcarriers whose phase and amplitude
values cancel OOB
• Modulated Filter Banks─ Attenuates OOB in stopband region
• Combine cancellation carriers (CCs) with modulated filter banks (MFBs) to attenuate OOB emissions
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Cancellation Carriers
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Filtering with CCs
−4 −2 0 2 4 6 8 10 12 14 16
−0.2
0
0.2
0.4
0.6
0.8
1
Subcarrier Index
Nor
mal
ized
Am
plitu
de
Raised−Cosine Filter
CC1 CC2
Worcester Polytechnic Institute
Hardware Experimentation
Photograph of a spectrally agile wireless transceiver test-bed at Poznan
University of Technology, Poznan, Poland.
Photograph of a spectrally agile wireless transceiver test-bed at Worcester Polytechnic Institute,
Worcester, MA, USA.
Worcester Polytechnic Institute
Spectrally Agile Waveform ResultsP.
Kry
szki
ewic
z, H
. Boguck
a, A
. M
. W
yglin
ski. "
Prote
ctio
n o
f Pr
imar
y U
sers
in D
ynam
ically
Vary
ing R
adio
Envi
ronm
ent:
Pr
actica
l Solu
tions
and C
halle
nges
." Acc
epte
d for
public
atio
n in
the
EU
RASIP
Journ
al o
n W
irel
ess
Com
munic
atio
ns
and
Net
work
ing
Dec
ember
23
2011
Worcester Polytechnic Institute
Performance with notches of different size
53
Worcester Polytechnic Institute
Performance with different number of notches
54
Worcester Polytechnic Institute
Digital Pre-Distortion Results
55
Output PSD of PA model
0 0.05 0.1 0.15 0.2 0.250
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
PA Input Magnitude
Nor
mal
ized
Out
put M
agni
tude
Nonlinear PA modelLinearized PA model
−1 −0.5 0 0.5 1−160
−140
−120
−100
−80
−60
−40
−20
0
20
Normalized Frequency (x π rad/sample)
Pow
er S
pect
ral D
ensi
ty [d
B]
1st ILA iteration2nd ILA iteration3rd ILA iteration
AM/AM
Zhu Fu, Lauri Anttila, Mikko Valkama and Alexander M. WyglinskiA. M. Wyglinski. "Digital Pre-distortion of Power Amplifier Impairments in Spectrally Agile Transmissions." Proceedings of the 2012 IEEE Sarnoff
Symposium, Newark, NJ, USA, May 2012.
CubeSat SDR
56
Worcester Polytechnic Institute
Motivation
• Challenges associated with time-varying satellite communication links
• Leverage existing technologies in order to enhance transmission quality via an efficient, low-cost approach─Software-defined radio (SDR) employed
to achieve highly responsive space platforms
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Proposed Solution
• CubeSat-based SDR platform prototype developed─ Custom designed FPGA board possessing Spartan 3A
XC3S1400A device incorporated into CubeSat platform ─ Contains customized variant of commercially available
Universal Software Radio Peripheral (USRP) SDR platform
• Several satellite communication baseband modules implemented for FPGA─ Migrated to COSMIAC Small Form Factor CubeSat FPGA
Board (CCFB) possessing customized USRP SDR
Worcester Polytechnic Institute
Project Vision
• Creation of adaptive satellite communications link based on a combination of reconfigurable FPGA-based software-defined radio (SDR) platforms and cognitive radio concept─ Enables “data throttling” for maximizing data
throughput─CubeSat SDR platforms aware of environmental
conditions
Worcester Polytechnic Institute
COSMIAC FPGA
1”
COSMIAC Xilinx Spartan 3A FPGA
Worcester Polytechnic Institute
COSMIAC CubeSat Modules
COSMIAC CubeSat FPGA Board with Sensor and Power Daughtercards (no RF daughtercards are present in this photo)
FPGA Board
Optical SensorBoard
Power Board
Worcester Polytechnic Institute
FPGA-Based Embedded Controller Board
Spartan 3AFPGA
4 GbNAND Flash
Memory
2 GbDDR2 SDRAM
Memory
LEDs &Switch
JTAG
RS232Level Shift
EthernetLAN8700
1 MbNOR Flash
Config Memory
USB2USB3300
AT90 (SPA-U)Microcontroller
SPA-UConnector
SPA-1Header
Connectors to Daughter Card
Worcester Polytechnic Institute
MicroBlaze
USB2 Controller
SPI Controller
I2C Controller
Modified USRP
Flash Memory Controller
DDR2 Memory Controller
Ethernet ControllerRS232 UARTRS232 UART
(AT90)
USB Data
RFDaughte
Card
Worcester Polytechnic Institute
Laboratory Testing
Current SatCom laboratory setup at COSMIAC
Concluding Remarks
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These are interesting times!
• Numerous advances in cognitive radio, dynamic spectrum access, and software-defined radio have recently occurred─ Secondary access of digital TV spectrum─ Ratification of IEEE 802.22, IEEE 802.11af standards
• Today’s wireless landscape is quickly changing due to new capabilities of wireless transceiver devices─ Largely due to smaller, faster processing devices resulting
from applications such as smart phones
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Still room for improvement
• There still exists a substantial amount of research that is needed to make future wireless devices such as cognitive radio more reliable─ Ensuring minimal interference to other wireless
transmissions─ Enabling real-time decision-making and transmission
operations─ Making RF spectrum access more reliable for everyone
involved
More Information
Worcester Polytechnic Institute
Contact Info
Professor Alexander Wyglinski
Department of Electrical and Computer EngineeringWorcester Polytechnic Institute
Atwater Kent Laboratories, Room AK230
508-831-5061
http://www.wireless.wpi.edu/
Worcester Polytechnic Institute
Cognitive Radio Textbook
Available since December 2009 (Academic Press)
20 chapters
End-of-chapter problems (with solutions guide)
Presentation slides for most chapters
Covers physical and network layers, in addition to current platforms and standards
Worcester Polytechnic Institute
New SDR Textbook
• January 2013 Publications Date (Artech House Publishers)
• 9 comprehensive chapters ─ Fundamentals in signals &
systems, probability, and digital communications
─ “Hands on” approach to learning digital communication concepts using SDR and Simulink
─ End-of-chapter problems─ Corresponding course
lecture slides
http://www.sdr.wpi.edu/