Transcript Junshan Zhang

Emerging Science For Interdependent Complex Networks:
“Methodological Breakthrough Needed”
Junshan Zhang
School of ECEE, Arizona State University
NITRD Workshop on Complex Engineered Networks
Washington D.C., Sept 20-21, 2012
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From Individual Networks to
Network of Networks
• Networked systems: modern world consists of an intricate web of
interconnected physical infrastructure and cyber systems, e.g.,
communication networks, power grid, transportation system, social
networks, …
• Over the past few decades, tremendous effort on studying individual
networks:
• Communication networks, e.g., Internet, wireless, sensor nets, …
• Complex networks, e.g., E-R graph, small world model, scale-free
networks …
• Little attention has been paid to interdependent networks: Many
networks have evolved to depend on each other, and depend heavily on
cyber infrastructure in particular
•
Need a theoretic foundation for cyber-physical systems and
interdependent networks per se !
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Some Examples for Interdependent networks:
Modern Power Grid & Mobile Social Networks
[Nature 2010]
Over past 4~5 years, we have been studying
1) Smart Grid: Power station operation relies on the
control of nodes in cyber infrastructure;
cyber nodes need power supply from power stations
Q) Which parts are most vulnerable and which other
parts are most resilient? Where are interdependences?
2) Mobile social networks: Social networks rely on
communication media; and network traffic is affected
by social networking.
Q) What is impact of interdependence on traffic
volume and social networking behavior?
Interdependence: Operations of one network depend
heavily on the functioning of the other network
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Methodological challenges: Modeling, Designing
and Analyzing Interdependent Networks
cross-networks support
physical system
(e.g. power grid)
cyber network
(e.g. Internet)
I) From model abstraction to problem formulation: How to model different
functionality modules and the interdependence?
- Often times disparate methods are used for cyber systems and physical
systems, e.g., differential equations for power systems whereas graph models for
communication networks
- Interdependence is asymmetric and depends on local properties, e.g., different
components of power grids have different QoS requirements; further,
more difficult to abstract dependence of comm. network on power grid
II) Engineering machineries : incommensurate (fragmented) tools for multi-scale
dynamics in spatio-temporal domains and across interdependent subsystems,
- tree-based hierarchical control meets mesh networking
- graphical models meet differential equations, Nonconvexity & stochastic
-Percolation theory meets combinatorial optimization
Cyber-Physical Systems (CPS):
Two Interdependent Networks
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A networked system consists of physical network and cyber network
Emerging as the underpinning technology for 21th century
Applications: smart grid, intelligent transportation system,
manufacturing, etc.
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