Vehicular Communications and Networks Employing Cognitive Radio
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
• Vehicular DSA
• Measurement Campaign
• Capacity Analysis
• Experimental Validation
• Concluding Remarks
• More Information
Introduction
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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)
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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
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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
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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
Wireless Innovation Laboratory
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• 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?
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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
Vehicular DSA
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• Several automobile manufacturers are looking at increasing the level of information connectivity amongst road vehicles
• Several technological initiatives are underway for developing vehicular communications─US Dept. of Transportation’s IntelliDrive
program to provide V2V and V2I communications
Emergence of Vehicular Comms
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• Vehicular communications have several uses─ Emergency information Deer, road conditions, sudden traffic situations
─ Infotainment Sharing Disney DVDs between minivans
─Obtaining diagnostic information from the vehicle itself Remote roadside assistance
─Supporting autonomous system implementations “Platooning”, self-driving vehicles
Different Supported Applications
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DTV Spectrum an Attractive Option!
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Vehicular Dynamic Spectrum Access
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Notice how the spectrum occupancy changes as a function of distance!
Spectrum Occupancy as a Function of Speed???
Measurement Campaign
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• Although spectrum occupancy models give part of the story, empirical measurements can help provide further insights
• Forty eight locations chosen across I-90 in the state of Massachusetts approximately 2 miles apart
• Spectrum measurements taken in a moving vehicle on 06/30/2009
Understanding of DTV Spectrum
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A map of the locations close to I-90 between Boston, MA and West Stockbridge, MA over which spectrum measurements were collected on 06/07/2009, 06/11/2009, 06/12/2009 and
06/30/2009
Measurement Locations
~217 km
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• Measurement setup consists of─ A spectrum analyzer,─ A laptop installed with
SQUIRREL (both of them located inside the car) and
─ A mini-discone antenna
• Frequency resolution chosen – 20 kHz
• Time sweeps per site – 10
Measurement Setup
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Frequency (in MHz)
Sw
eep
Inde
x
500 550 600 650 700 750
50
100
150
200
250
300
350
400
450
-120
-110
-100
-90
-80
-70
-60
-50
Energy Spectral Density plots for the TV frequencies in the higher frequency range i.e.,
470 – 806 MHz across 48 locations close to I-90 between Boston, MA and West Stockbridge, MA.
Boston
MA/NY
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Raw Measurements
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TV Channel availability at different locations along I-90 in the state of Massachusetts.
Spectrum Occupancy Results
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The total available bandwidth for secondary usage at different locations along I-90 in the state of Massachusetts.
How does low bandwidth availability
coupled with high traffic density affect secondary access to wireless spectrum?
How does low bandwidth availability
coupled with high traffic density affect secondary access to wireless spectrum?
Available Bandwidth
Capacity Analysis
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• Model bandwidth resources as servers─ In queuing theory one job at a time per
server
• Model bandwidth requests made by vehicles as service requests from users
• Model sub-channel occupation time of each request as the service time of each job
• Multi-server model with a single queue
Problem Formulation
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TV bands
Quit bandCh 21
Ch 22
Ch 51
Service time :General,Deterministic,Exponential,…
Model Functionality
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• This model incorporates location dependent channel availability change by turning on/off servers
• Channel availability depends on─Spatial-temporal channel availability
map─Vehicle location and current time Function of speed and location on the
highway
DTV Spectrum Map
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Bandwidth requests
TV bands
Server down if
occupied by PU
Suppose same λfor all cars of the
same priority class, N changes
depending on time and location
Priority Access
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Predicted performance measures in the case when all cars are of the same priority, where M/D/m model assumes deterministic service time, and M/M/m model
assumes exponential service time.
Results
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Predicted performance measures in the case where cars have different priorities and same message rate of 60 msg/sec. The number of higher class customers is 10% that
of lower class customers. M/D/m model assumes deterministic service time, and M/M/m model assumes exponential service time.
Results
Experimental Evaluation
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• Various research efforts into assessing the feasibility of performing DSA within vehicular networks─ Examination of candidate frequency bands for supporting
VDSA networks─ Defining networking protocols for enabling VDSA
communications─ Assessment of theoretical capacity for VDSA networks
• There have only been a couple of attempts to experimentally assess VDSA in hardware─ IEEE WiVec 2011: “The Kyushu Experiment”
Theory & Simulation Are Nice But ...
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Isolated region on the island
of Kyushu
First Point-to-Point DTV VDSA Experiment!
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So how do you do VDSA
experimentally?
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Step 1: Dedicated Students
December 2010
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Step 2: Students with Cars
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Step 3: Lots of SDRs!!
Cre
dit
: G
eorg
e E
ich
ing
er, 2
011
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Step 4: Gather Results
Secondary wireless of vehicular communications
Experimental results for the WI Lab VDSA experimental test-bed.
A
BC
D
Multi-hop VDSA transmissions via vehicles ABCD
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
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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/
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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
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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/