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Bandwidth Allocation in Sense-and-Respond Systems

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Bandwidth Allocation in Sense-and-Respond Systems Vincenzo Liberatore Research supported in part by NSF CCR-0329910, Department of Commerce TOP 39-60-04003, NASA ... – PowerPoint PPT presentation

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Title: Bandwidth Allocation in Sense-and-Respond Systems


1
Bandwidth Allocation in Sense-and-Respond Systems
  • Vincenzo Liberatore

Research supported in part by NSF CCR-0329910,
Department of Commerce TOP 39-60-04003, NASA
NNC04AA12A, and an OhioICE training grant.
2
Sense-And-Respond
  • Computing in the physical world
  • Components
  • Sensors, actuators
  • Controllers
  • Networks

3
Sense-and-Respond
  • Enables
  • Industrial automation BL04
  • Distributed instrumentation ACRKNL03
  • Unmanned vehicles LNB03
  • Home robotics NNL02
  • Distributed virtual environments LCCK05
  • Power distribution P05
  • Building structure control SLT05
  • Merge cyber- and physical- worlds
  • Networked control and tele-epistemology G01
  • Sensor networks
  • Not necessarily wireless or energy constrained
  • One component of sense-actuator networks

4
Characteristics
  • Heterogeneous collection of networked sensors,
    actuators, controllers
  • Power
  • Often plentiful, sometimes limited
  • Communication
  • Often wired, sometimes low-bandwidth wireless
  • Critical requirements
  • Safety
  • Stability
  • Dependability
  • Robustness
  • QoS
  • Scalability
  • Adaptability

5
Information Flow
  • Flow
  • Sensor data
  • Remote controller
  • Control packets
  • Timely delivery
  • Stability
  • Safety
  • Performance

6
Outline
  • Outline
  • Introduction to Sense-and-Respond
  • Bandwidth Allocation
  • Future of Cyber-Physical Infrastructure
  • Warning
  • Most EE-oriented talk I could possibly give
  • Avoid redundancy with previous talks

7
Bandwidth Allocation
8
Bandwidth Allocation
  • Definition
  • Multiple sense-and-respond flows
  • Contention for network bandwidth
  • Desiderata
  • Stability and performance of control systems
  • Must account for physics
  • Efficiency and fairness
  • Fully distributed, asynchronous, and scalable
  • Dynamic and self-reconfigurable

9
Control and Networks
  • Control over Networks (Cover N)
  • NCSs, DCSs, SANETs, CPs,
  • Control of Networks (Cof N)
  • Efficient BW allocation
  • Regulate the packet injection rate
  • Cof N scheme to better serve Cover N

10
Control of Networks
  • A bandwidth allocation scheme
  • Formulate the scheme as a Control problem
  • Control systems regulate sending rate based on
    congestion signal fed back from the network

11
Sampling Rate and Network Congestion
12
Problem Formulation
  • Define a utility fn U(r) that is
  • Monotonically increasing
  • Strictly concave
  • Defined for r rmin
  • Optimization formulation

13
Distributed Implementation
  • Two independent algorithms
  • End-systems (plants) algorithm
  • Router algorithm (later on)

Plant
Router
Controller
14
NCS-AQM Control Loop
Plant
Queue
f(q(t))
qSr(t) - C
p(t)
q(t)
tf
tb
15
Queue Controller G(s)
  • Proportional (P) Controller
  • GP(s) kp
  • Proportional-Integral (PI) Controller
  • GPI(s) kp ki/s

16
Determination of kp and ki
  • Stability region in the kikp plane
  • Stabilizes the NCS-AQM closed-loop system for
    delays less or equal d
  • Analysis of quasi-polynomials, f(s,es)

17
Simulations Results
Branicky et al. 2002
Zhang et al. 2001
18
Simulations Results (cont.)
PI
P
19
Related Work
  • Congestion Control
  • Primarily addresses elastic flows
  • Active Queue Management (AQM)
  • Utility maximization and controllers often viewed
    as alternative approaches
  • Multi-media congestion control
  • E.g., Equation-based
  • Smooth rate variation
  • No physically relevant utility
  • Time-scales
  • Approach to define time-varying utility functions
  • C of N missing

20
Outline
  • Outline
  • Introduction to Sense-and-Respond
  • Bandwidth Allocation
  • Future of Cyber-Physical Infrastructure
  • Warning
  • Most EE-oriented talk I could possibly give
  • Avoid redundancy with previous talks

21
Cyber-Physical Systems
  • Foundations and technologies for rapid and
    reliable development and integration of
    computer-centric physical and engineered systems
  • Globally virtual, locally physical
  • Major NSF initiative planned

22
Needs and Directions
  • Needs and Directions
  • New Calculus
  • Merge time- and event-based systems
  • New Tools
  • E.g., co-simulation for co-design
  • New Networks methods
  • Bandwidth allocation, play-back buffers
  • New Education
  • Multi-disciplinary education
  • Telltale sign New Metrics
  • Network-oriented metrics
  • Delay, jitter, loss rates, bandwidth
  • Impacts physics, but different from physics
    behavior
  • Control-Theoretical metrics
  • Overshoot, rise time, settling time, etc.
  • Hard to relate to network conditions
  • Multi-disciplinary metrics
  • E.g., plant tracking in terms of network
    bandwidth allocation
  • An E-Model for cyber-physical systems?

23
Example
PI
P
24
Metrics (not sure)
  • Stability (and safety)
  • Objective
  • Remote controller makes unstable system stable
  • Extensive research
  • Z01 and references therein
  • Problem
  • Errors, network partitions, failures make
    stability impossible
  • Tracking
  • Objective
  • The SR system should do what it is supposed to
  • In spite of network non-determinism (failures,
    security, etc.)
  • Problem
  • Benchmarks (NIST?)
  • Disturbance cancellation
  • Objective
  • The SR system should do what it is supposed to
    do
  • In spite of network non-determinism and
    uncertainty in the environment
  • Way out
  • Use simple tasks
  • Scalability L04
  • Number of nodes
  • Space networks?
  • Geographic
  • Administrative
  • Functional
  • Conclusion
  • RT SR benchmarks needed!

25
Acknowledgments
  • Students
  • Ahmad al-Hammouri
  • David Rosas
  • Zakaria Al-Qudah
  • Huthaifa Al-Omari
  • Nathan Wedge
  • Qingbo Cai
  • Prayas Arora
  • Colleagues
  • Michael S. Branicky
  • Wyatt S. Newman

26
Conclusions
  • Sense-and-Respond
  • Merge cyber-world and physical world
  • Critically depends on physical time
  • Bandwidth Allocation
  • Control of Networks to aid Control over Networks
  • Complete characterization of the stability region
  • Evaluation
  • Peak detection
  • Cyber-physical systems

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