Spectrum Management and
Cognitive Radios Alessandro Guidotti, XXIV ciclo
Bologna, 24-25/01/2012
DEIS – Fondazione Ugo Bordoni
Is spectrum lacking?
• Command & Control spectrum allocation model
– Static spectrum allocation
• Ever increasing demand for new wireless services
– Broadband access to anyone, anywhere, at anytime
Commonly shared feeling of spectrum scarcity
Great amount of
underused resources
Is spectrum lacking?
• Two main approaches to this issue
– Flexible spectrum access
• Cognitive Radios
– Release of spectrum bands thanks to more
efficient wireless technologies
• Digital swtich-on process (DVB-T)
My Ph. D. activity Spectrum Management
&
Cognitive Radios
Cognitive
Radios
Spectrum
Release
Mutual interference between DVB-T
and LTEAmount of spectrum potentially available
as White Space
Geolocation databases
Characterization of the Hidden Node Margin
Cooperative energy detection algorithms
Coexistence between CRs and TETRA
Cognitive Satellite Terrestrial Radios
Stochastic Geometry for network interference
characterization
CEPT SE43
CEPT
CPG PT-D
SUPELEC
FP7 Project
Introduction of broadband services in
the 800 MHz band
Network interference
• Modeling of network interference is a key issue in
next-generation systems
– Interference mitigation, control of e.m. emissions, etc.
– CRs: network performance, harmful interference control
• Three main factors
1. Spatial distribution of the nodes
2. Transmission characteristics
3. Propagation characteristics
Spatial distribution
• Deterministic model
– Known locations
– Locations constrained to fixed structures (e.g.,
hexagonal grid)
• Cognitive Radio networks
– Inherent unplanned, irregular and random distribution
– No deterministic approach
– Extensive and complex system-level simulations
• Advanced mathematical tools for statistical
modeling
– Spatial average performance metrics
Stochastic Geometry
• Network: snapshot of a stationary random model in
the Euclidean space
• Nodes locations: realization of a Point Process
• d-dimensional Euclidean space
• set S of all the possible sequences of points in it,
s.t. any Φ in S is finite and simple
PP: r.v. whose values are the point
patterns Φ taken from S
-10 -8 -6 -4 -2 0 2 4 6 8 10
-10
-8
-6
-4
-2
0
2
4
6
8
10
X [m]
Y [
m]
Poisson Point Process
• The homogeneous PPP is the most used model
• Spatial invariance properties
– Superposition, thinning, mapping
– Slivnyak’s Theorem: removing a point does not change the
distribution of the other points
Number of nodes: Poisson r.v.
Locations: uniformly distributed
Interference as PPP
• Exponential power-decaying path-loss model, α>2
• Objective: closed-form of the MGF in b(o,R1,R2)
– Coverage probability, average downlink rate, ASEP
• Previous works: closed-form in b(o,R) with
Rayleigh fading only, no modulation
Moment Generating Function
• Procedure
– Condition on having k nodes
• The single interference terms are i.i.d.
– Solve the expectations on modulation
and node activity
– Decondition on having k nodes
– Restrict integration bounds to b(o,R1,R2)
Moment Generating Function
• Generalized modulation coefficients, nodes
activity and network layout
Moment Generating Function
• Nakagami-m fading channels Rayleigh fading
• Series expansion of Γ(a,x) and Hypergeometric functions:
Moment Generating Function
• Lower values for decreasing α
• Lower values for increasing p, λ
α=4 α=5 Nakagami-m, m0=2
Rayleigh
• Slight dependence on the
channel model
Average downlink rate
• BSs distributed according to homogeneous PPP
in Rd with density λ
• The intended node (y≡o) communicates with the
closest BS, all the other BSs act as interferers
• Previous works: three-fold integral expression
with Rayleigh fading and α=4
Average downlink rate
• Proposed model: MGF-based approach
Rate: function of the MGF of the aggregate
interference and the intended link fading
Average downlink rate
Meijer-G function properties
• Single-integral with Meijer-G function
• Generalized fading channels
• Different channel models on intended and interfering
links
Average downlink rate
• Nakagami-m fading
• Lognormal fading
Hermite polynomials
Average downlink rate
• The rate significantly
improves for higher α
α=4 α=5 Nakagami-m vs Rayleigh, m0=2
Rayleigh
• Slight improvements for
increasing m0 (Rayleigh)
Results
• Coverage
– Single-integral, Rayleigh, α=4 closed-form,
generalized fading, α>2
• Average downlink rate
– Three-fold integral, Rayleigh, α=4 single-integral,
generalized fading, α>2
• Average Symbol Error Probability
– Semi-analytical model single-integral
– Synchronous case upper bounds the asynchronous
• Many parameters of interest in closed-form
Future works
• MIMO systems
– Statistical characterization of uncorrelated paths
• Cooperative sensing
– Theoretical expression with generalized fading
• Relay networks
– Effect of multi-hop communications
• Cognitive Satellite networks
– Aggregate interference at Ground Stations
International activities
• CEPT CPG PT-D – WRC-12 agenda items 1.5, 1.7, 1.8, 1.17, 1.18, 1.20, and 1.25
• CEPT SE43 – Technical and operational requirements for the operation of
cognitive radio systems in the „white spaces‟ of the frequency
band 470-790 MHz
• CoRaSat (FP7)
– Cognitive Radio for Satellite Communications
• Cost Action IC0902 – Cognitive Radio and Networking for Cooperative Coexistence of
Heterogeneous Wireless Networks
Personal contributions • A. Guidotti, M. Di Renzo, G. E. Corazza, and F. Santucci, “Simplified Expression of Coverage Probability and
Average Rate of Cellular Networks Using Stochastic Geometry,” IEEE Transactions on Communications (to be
submitted), 2012
• A. Guidotti, M. Di Renzo, G. E. Corazza, and F. Santucci, “Simplified Expression of the Average Rate of Cellular
Networks Using Stochastic Geometry,” IEEE International Conference on Communication 2012 (ICC 2012), June
2012
• C. Merola, A. Guidotti, M. Di Renzo, F. Santucci, and G. E. Corazza, “Average Symbol Error Probability in the
Presence of Network Interference and Noise,” IEEE International Conference on Communication 2012 (ICC 2012),
June 2012
• A. Guidotti, D. Guiducci, M. Barbiroli, C. Carciofi, P. Grazioso, and G. Riva, “Coexistence and Mutual Interference
between Mobile and Broadcasting Systems,” IEEE Vehicular Technology Conference - Spring 2011 (VTC Spring
2011), May 2011
• A. Guidotti, P. Grazioso, M. Barbiroli, C. Carciofi, D. Guiducci, and G. Riva, “Analysis of coexistence and mutual
interference between mobile and digital television systems,” Systemas y Telematica (S&T), October 2010
• M. Barbiroli, A. Guidotti, P. Grazioso, and G. Riva, “Coexistence and mutual interference between mobile radio and
broadcast systems – Preliminary simulation results,” COST 2100 TD(09)709, February 2009
• “WRC-12 AI 1.17 - Broadcasting versus mobile: theoretical analysis of mutual interference,” Tech. Rep.
CPGPTD(10)109, Italian Contribution to CPG PT-D - Agenda Item 1.17, Aug. 2010
• “WRC-12 AI 1.17 - Options for method A1,” Tech. Rep. CPGPTD(10)156, Italian Contribution to CPG PT-D -
Agenda Item 1.17, Aug. 2010
• “WRC-12 AI 1.17 - Options for method A1,” Tech. Rep. CPGPTD(11)33, Italian Contribution to CPG PT-D -
Agenda Item 1.17, Aug. 2011
• M. Barbiroli, C. Carciofi, D. Guiducci, A. Guidotti, E. Tarantino, and G. Riva, “Advantages and disadvantages of the
introduction of IMT systems in the 800 MHz band,” International Conference on Electromagnetics in Advanced
Applications 2011 (ICEAA 2011), September 2010
Personal contributions • “Availability of spectrum for white space devices in the band 470-790 MHz,” Tech. Rep. SE43(10)22, Italian
Contribution to CEPT SE43, Jan. 2010
• “Calculation of the Hidden Node Margin in a real Italian scenario,” Tech. Rep. SE43(10)123, Italian Contribution to
CEPT SE43, Aug. 2010
• M. Barbiroli, C. Carciofi, A. Guidotti, and D. Guiducci, “Evaluation and Analysis of the Hidden Node Margin for
Cognitive Radio System Operation in a Real Scenario,” European Conference on Antennas and Propagation 2011
(EuCAP 2011), April 2011
• S. Kandeepan, L. De Nardis, M.-G. Di Benedetto, A. Guidotti, and G. E. Corazza, “Cognitive Satellite Terrestrial
Radios,” IEEE Global Communications Conference (GLOBECOM 2010), December 2010
• “Enforcement issues related to the geolocation database approach,” Tech. Rep. SE43(10)96, Italian Contribution to
CEPT SE43, Jun. 2010
• “Translation of the information provided to the geolocation database into elements of authorisation to the WSD,”
Tech. Rep. SE43(10)124, Italian Contribution to CEPT SE43, Aug. 2010
• “Proposal of an application methodology to combine geo-location database and sensing,” Tech. Rep. SE43(11)38,
Italian Contribution to CEPT SE43, Jul. 2011
• “Performance analysis of cooperative energy detection sensing,” Tech. Rep. SE43(11)37, Italian Contribution to
CEPT SE43, Jul. 2011
• “Feasibility of autonomous operation of WSDs using sensing,” Tech. Rep. SE43(11)62, Italian Contribution to
CEPT SE43, Sep. 2011
• “Consideration of coexistence between WSD and TETRA,” Tech. Rep. SE43(11)39, Italian Contribution to CEPT
SE43, Jul. 2011
• R. Suffritti, G. E. Corazza, A. Guidotti, V. Petrini, D. Tarchi, A. Vanelli-Coralli, and M. Di Renzo, “Cognitive hybrid
satellite-terrestrial systems,” International Conference on Cognitive Radio and Advanced Spectrum Management
2011 (CogART 2011), October 2011
Short courses
• Long Term Evolution e 4G
• Compatibilità Elettromagnetica LS
• Nuove frontiere nella gestione dello spettro radio
• SatNEx Summer School
• Newcom++ Spring School
– Cognitive Wireless Communication Networks
• COST2100/CONET/Newcom++ Training School
– Cooperating Objects and Wireless Sensor Networks
Thank you!