Whitespace Measurement and Virtual
Backbone Construction for Cognitive Radio
Networks: From the Social Perspective
Shouling Ji and Raheem Beyah
Georgia Institute of Technology
Zhipeng Cai and Meng Han
Georgia State University
Introduction
Secondary Users (SUs)
Primary Users (PUs)
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Introduction
• Problem
– Systematically analyze the spectrum whitespace in CRNs from a social network
perspective
• Contribution
– Propose a novel metric named centrality score to measure the active weights of PUs by
considering each PU’s topological importance and the global primary network running
and traffic information
– Analyzed the whitespace for SUs under three primary activity social patterns: i.i.d.
distribution, Poisson distribution, and Gaussian distribution
– Propose a Spectrum Altitudes based Virtual Backbone (SAVB) construction algorithm
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Outline
• Introduction
• System Model
• PUs’ Social Attributes and Whitespace Analysis
• Virtual Backbone (VB) construction
• Simulation
• Conclusion
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
System Model
• Primary Network
– N Poisson distributed PUs with density of λp
– Transmission and interference radii: R and RI
– The network time is slotted with each time slot of length τ
– The licensed spectrum bandwidth W
– The primary network is dense scaling
• Secondary Network
– n randomly deployed SUs
– Transmission and interference radii: r and rI
– The secondary network is connected and dense scaling
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Outline
• Introduction
• System Model
• PUs’ Social Attributes and Whitespace Analysis
• Virtual Backbone (VB) construction
• Simulation
• Conclusion
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Centrality Score of PUs
• Motivation: local and global activity behavior of PUs
• Centrality score of a PU Si
Expected # of active PUs
The # of shortest paths in the primary network
S. Ji, Z. Cai, M. Han, and R. Beyah
The betweenness centrality of Si: the number of
shortest paths passing Si
The average # of PUs on shortest paths
Whitespace Measurement and VB Construction
Centrality Score of PUs
• Centrality score of a PU Si
The average # of active PUs on
each shortest path
The weight of a PU on each
shortest path to be active
The normalized weight of Si to be active
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Social Activity Pattern of PUs
• By recent empirical studies
– i.i.d. activity pattern
– Poisson distribution pattern
, e.g., the GSM90 uplink service
– Gaussian distribution pattern
mobile device holders, WiFi users
S. Ji, Z. Cai, M. Han, and R. Beyah
, e.g., cell phone users, cellular network users,
Whitespace Measurement and VB Construction
Whitespace Analysis
• i.i.d. activity
– The lower and upper bounds of the centrality score of PU Si
– The lower and upper bounds of the active probability of PU Si
– The lower and upper bounds of the available spectrum whitespace for a secondary link
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Whitespace Analysis
• Poisson distributed pattern
• Gaussian distributed pattern
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Outline
• Introduction
• System Model
• PUs’ Social Attributes and Whitespace Analysis
• Virtual Backbone (VB) construction
• Simulation
• Conclusion
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Virtual Backbone (VB) Construction
• Definition of VB
– A VB B of the secondary network is a subset of SUs such that (i) every SU is either in
B or has some neighbor in B; and (ii) B is connected.
• Objective
– Seek a VB with small size
– Seek a VB with more spectrum bandwidth available
•
Spectrum altitude
– Measures the average available whitespace at SU su
– A high
implies su has more neighbors and high available spectrum whitespace to its
neighbors on average
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Virtual Backbone (VB) Construction
Seek a Maximal Independent Set
(MIS) M of the secondary network
Final a minimal set C of
connectors to connect the
independent nodes in M
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Virtual Backbone (VB) Construction
• Correctness analysis of SAVB
• Performance analysis of SAVB
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Outline
• Introduction
• System Model
• PUs’ Social Attributes and Whitespace Analysis
• Virtual Backbone (VB) construction
• Simulation
• Conclusion
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Simulation
• Settings
– Time is slotted with each time slot is normalized to one
– The primary bandwidth is normalized to 100
– Examine the unicast throughput under different primary activity distributions
• Comparison
– US (Journal of Combinatorial Optimization, 2013): a VB is first constructed on top of a
cell-based network partition; then, the unicast is carried out on the VB
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Simulation
•
Whitespace estimation
•
Successful delivery ratio
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Conclusion
– We provide a mathematical framework for deriving the
whitespace for SUs
• With local and global primary activity consideration
• With typical primary social patterns consideration
– Propose a spectrum altitude based virtual backbone construction
algorithm
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction
Thank you!
Shouling Ji
sji@gatech.edu
http://users.ece.gatech.edu/sji/
S. Ji, Z. Cai, M. Han, and R. Beyah
Whitespace Measurement and VB Construction