Transcript Cognitive Radios for Open Access to Spectrum Narayan Mandayam Christopher Rose Predrag Spasojevic Roy Yates (in partnership with Lucent Technologies) Rutgers University www.winlab.rutgers.edu Email: [email protected].

Cognitive Radios for Open Access to Spectrum
Narayan Mandayam
Christopher Rose
Predrag Spasojevic
Roy Yates
(in partnership with Lucent Technologies)
Rutgers University
www.winlab.rutgers.edu
Email: [email protected]
Project Motivation
Triumph of Technology vs. Triumph of Economics
• What everyone agrees on:
– Spectrum use is inefficient
– FCC licensing has yielded false scarcity
• The Spectrum Debate:
– Open Access (Commons)
• [Noam, Benkler, Shepard, Reed …]
• Agile wideband radios will dynamically share a commons
– Spectrum Property Rights
• [Coase, Hazlett, Faulhaber+Farber]
• Owners can buy/sell/trade spectrum
• Flexible use, flexible technology, flexible divisibility,
transferability
• A spectrum market will (by the force of economics) yield an
efficient solution
The Open Access Conundrum
• Systems of end-user devices
• Technology Panacea
– Spread spectrum, UWB, MIMO
– Short range communications
– Ad hoc multi-hop mesh networks
• Evidence: success of 802.11 vs. 3G
• Minor technical rules for transceivers
– power, spreading
• Technical arguments against Open Access
– Partially developed theory
• ad hoc network capacity, with/without mobility
• IT relay and interference channel
– Infant technology
• UWB, antenna arrays
• Transmitter agility
– Technology not separable from user assumptions
• Capabilities of technology vary with cooperation
Technology for Enabling Open Access?
Research themes that have emerged from
adhoc/sensor networks research:
• Hierarchical Architecture wins
– Capacity scaling, energy efficiency, increases
lifetimes, facilitates discovery
• Cooperation wins
– Fundamental performance limits via information
theoretic relay and broadcast channels
• “Global” awareness and coordination wins
– Space, time and frequency awareness and coordination
beyond local measurements
Technology for Enabling Open Access?
Require radios that can :
–
–
–
–
Discover
Cooperate
Collaborate
Self-Organize into hierarchical networks
• Agility is necessary at every layer of the
“protocol stack”
• But cannot yet predict environments
The Answer? “Cognitive Radios”

Cognitive Radios for Enabling Open Access
POOF! Let there be cognitive radios!
(let Bryan worry about details)
Then What???
• Discovery strategies for available spectrum
– Algorithms and protocols for frequency selection, coordination and
cooperation
• Coding strategies for efficient sharing
– Cooperative diversity and coding for increased spectrum utilization
• Information strategies for efficient cooperation
– “Spectrum Servers” to advise/mediate sharing
• Negotiation strategies for situations of conflict
– Pricing and game theoretic strategies to promote cooperation
• Domination strategies for situations of conflict
– Spectrum warfare with agile waveforms
Spectrum Policy Server (SPS)
Internet-based Spectrum Policy Server can help to coordinate
wireless networks
-
needs connection to Internet even under congested conditions (...low bit-rate OK)
some level of position determination needed (..coarse location OK)
spectrum coordination achieved via etiquette protocol centralized at server
Spectrum
Policy Server
www.spectrum.net
Internet
WLAN
operator A
AP1
Access Point
(AP2)
Etiquette
Protocol
AP1: type, loc, freq, pwr
AP2: type, loc, freq, pwr
BT MN: type, loc, freq, pwr
WLAN
operator B
Master
Node
Ad-hoc
Bluetooth
Piconet
Wide-area
Cellular data
service
SPS Methodology
• New users get an SPS
address
SPS
– Analogous to DHCP
• Users send activity traces to
SPS server
• SPS maintains database of
activity traces
SPS Issues
•
•
•
•
What to measure?
Coarseness of measurements?
Trace update frequency?
SPS database organization to
facilitate fast searching?
SPS Actions
• Share wireless node
descriptors?
• Coordinate comm. between
nodes?
• Mediate spectrum sharing
among nodes?
Incentives for Forwarding?
• Forwarding reduces
interference, saves battery
life, increases coverage area
• There are two kinds of costs
associated with packet
forwarding:
– Power Consumption (REAL
COST)
– Delay in Own Data
(OPPORTUNITY COST)
• Why (and how) will
autonomous nodes forward ?
Fostering Cooperation Through “Bribery”
A Microeconomic Framework for Enabling
Forwarding: Pricing & Reimbursement
• Nodes control their:
–
–
–
to
Transmit powers
Forwarding Preferences
Destination Preferences
maximize bits/Joule
• The network controls:
– Pricing Coefficient 
– Reimbursement
Coefficient:
to maximize its revenue
NETWORK ( ACCESS POINT )
Runs an optimization algorithm to determine the
Price for channel use
Reimbursement for forwarding
to maximize the revenue
The network declares the
pricing parameters
The network inspects the
revenue as an output of
declared pricing
parameters

Flow of parameters between adjacent nodes
USER
USER
USER
te
xt
te
xt
te
xt
THE USERS PLAY A NON-COOPERATIVE GAME TO MAXIMIZE THEIR UTILITIES
Two User-One Access Point Example
10
19
Aggregate bits/Joule
Aggregate bits/Joule, no reimbursement.
Horizontal Trajectory
10
18
ACCESS POINT
10
Radio tower
POSITIONS OF
USER 1 IN
HORIZONTAL
GEOMETRY
5m
5m
10
-
USER 2
(POTENTIAL
FORWARDER)
16
10 m
10
-5 m
17
USER 1(NONFORWARDER)
10
15
14
0
1
2
3
4
5
6
user 2 distance
• Incentives for forwarding works when nodes tend to “cluster”
• The aggregate bits/Joule in network is higher
• Network revenue is also higher
7
What You Learned in Kindergarten
The World Is A Rough Place
• Everybody wants what they want
– Greed is the norm
• The Golden Rule
– Be Polite
– Play Nice
• The REAL Golden Rule
–
–
–
–
Be aware of your surroundings
Develop a good left hook
Bruises are bad
Forgiveness is divine (when you have a good left hook)
A Toy Problem
2 Users with Unit Power
2 Orthogonal ChanNels
Symmetric -10dB Interference
High (30dB) SNR
Signal Space Game
1.0 1.0
5.7 2.2
5.0 5.0
2.2 5.7
2.0 2.0
2.2 5.7
5.0 5.0
5.7 2.2
1.0 1.0
Preliminary Results
If Better Performers Survive in
Marketplace…
• Adaptive Policy
– tit for tat
• Even Better
– tit for tat with random start
– forgiveness is divine
• Use Genetic Algorithms
– evolve against chosen policies
– evolve against evolving policies
Evaluation of Cognitive Approaches
• Capacity performance
– Information rates, spectral
efficiency, BER, FER, outage
Efficiency
• Cost performance
– Hardware complexity
– Software complexity
• Emulation of large-scale
networks of cognitive
radios
– ORBIT Testbed
– Emergent behavior
Hardware
Complexity
Agile
radio
Spectrum
server
Protocol
Complexity
Pricing
collaboration
Cognitive
protocols
Coded
cooperation