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Hongwei Zhang , Xiaohui Liu , Chuan Li , Yu Chen , Xin Che , Feng Lin*, Le Yi Wang * , George Yin Department of Computer Science, Wayne State University, Detroit, Michigan, {hongwei,xiaohui,chuan,yu_chen}@wayne.edu - PowerPoint PPT Presentation
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Co-channel interference as a major obstacle for predictable reliability, real-time, and throughput in wireless networking
Reliability as low as ~30% in current wireless scheduling/MAC protocols, thus not suitable for real-time, safety-critical networked control
Despite decades of research and practice, high-fidelity interference models that are suitable for distributed, field-deployable protocol design are still missing
Ratio-K model (i.e., protocol model) is local but not of high-fidelity SINR model (i.e., physical model) is of high-fidelity but non-local
PRK-Based Scheduling for Predictable Link Reliability in PRK-Based Scheduling for Predictable Link Reliability in Wireless Networked Sensing and ControlWireless Networked Sensing and Control
Hongwei Zhang, Xiaohui Liu , Chuan Li , Yu Chen , Xin Che , Feng Lin*, Le Yi Wang*, George Yin
Department of Computer Science, Wayne State University, Detroit, Michigan, {hongwei,xiaohui,chuan,yu_chen}@wayne.edu*Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, {flin,lywang}@wayne.edu
Department of Mathematics, Wayne State University, Detroit, Michigan, gyin@wayne.edu
From Open-loop Sensing to Closed-loop Sensing and ControlFrom Open-loop Sensing to Closed-loop Sensing and Control
Key idea: use link reliability requirement as the basis of instantiating the ratio-K model Model: given a transmission from node S to node R, a concurrent transmitter C does not
interfere with the reception at R iff.
Control-Oriented Wireless Networking: Physical-Ratio-K (PRK) ModelControl-Oriented Wireless Networking: Physical-Ratio-K (PRK) Model
Distributed PRK-Based Scheduling for Predictable Link ReliabilityDistributed PRK-Based Scheduling for Predictable Link Reliability
Behavior of Ratio-K-Based Scheduling
Physical-Ratio-K (PRK) Interference Model
Challenges of PRK-Based Scheduling
RSTRSK
RSPRCP
,,,
),(),(
Optimality of PRK-Based Scheduling
10 20 30 40 50 60 70 80 90 95 99
0
5
10
15
20
25
Thr
ough
put l
oss(
%)
PDR requirement(%)
Throughput loss is small, and it tends to decrease as the PDR requirement increases
-5 0 5-100
-50
0
50
100
150
200
k
Pos
sibl
e pe
rfor
man
ce g
ain
(%)
Median PDR gainMedian throughput gain
Ratio-K-based scheduling is highly sensitive to the
choice of K
Highest throughput is usually achieved at a K less than the minimum K for ensuring a certain min. link reliability, and
this is especially the case when link reliability requirement is high (e.g., for mission-critical sensing and control)
From passive to active safety: lane departure warning, collision avoidance From single-vehicle control to platoon control & integrated infrastructure-
vehicle control: networked fuel economy and emission control
From wired intra-vehicle networks to wireless intra-vehicle networks Multiple controller-area-networks (CANs) inside vehicles
• 50+ kg of wires increased, reduced fuel efficiency
• Lack of scalability: hundreds of sensors, controllers, and actuators
• Wiring unreliability: warranty cost, reduced safety
Connected VehiclesSmart grid: From centralized generation to distributed generation
Other Controllable
Loads
Washer
Dryer
Water Heater
Uncontrollable Loads
Plug-in Hybrid Electric Vehicle
Home Renewable & Energy
Storage System
A/C
Home Controller(s)
Microgrid Distributed Generator &
Combined Heat and Power System
MicroturbineFC
MicrogridController(s)
MicrogridRenewable & Energy
Storage System
Commercial Microgrid
Other Microgrids
Industrial Microgrid
Residential Microgrid
GridController(s)
Grand societal challenges Power grid With ~2,459 million metric tons of CO2
emission per year, electricity generation accounts for ~41% of USA’s total CO2 emission
Over 60% of today’s energy is wasted during distribution
Transportation Car accidents cause over 1.4 million
fatalities and 50 million injuries per year across the world
Motor vehicles account for >20% of the world’s energy use and >60% of the world’s ozone pollution
On-the-fly instantiation of the PRK model parameter
Dynamics and uncertainties in application requirements as well as network and environmental conditions
Protocol signaling in the presence of large interference range as well as anisotropic, asymmetric, and probabilistic wireless communication
RSTRSK
,,,
SR
C
RSTRSK
RSP
,,,
),(
PRK model instantiation: As minimum-variance regulation control Basic problem formulation
Reference input: desired link reliability Control output: actual link reliability Control input: PRK model parameter
Interference from outside exclusion region treated as disturbance
• Minimize variance of while ensuring its mean value of
Challenge: Difficult to identify closed-form relation between control input and control output
RST ,
RSTRSK
,,,
RSY ,
RSY ,
RST ,
Refined control problem formulation
Leverage communication theory result on the relation between and receiver-side SINR (i.e., )
“Desired change in receiver-side interference ” as control input
Linearization of the non-linear f(.)
RRS IP ,
RI
RRSRS IPfY ,,
RSY ,
))()(())()(())()(()(
))()(()(
where
)())()()(()(
,'
,,
,'
,,
tItPftItPtItPftb
tItPfta
tbtItPtatY
RRSRRSRRS
RRS
RRSRS
Minimum-variance regulation controller The control input that minimizes
while ensuring
and the minimum value of is
)()()1(
)()1()()( ,, t
tac
TtYctcytI U
RSRSR
1)][y(tvar is)]1([ ,RSTtyE
)()()1()1( 2222min, ttact Uy
region.exclusion theoutside from ceinterferen of changes
theof varianceandmean theare )( and )( where 2U ttU
1)][y(tvar
)1( to)( From,,, tKtIRSTRSR
Protocol signaling via local signal maps Local signal map: maintains wireless
signal power attenuation between nodes close-by
Simple approach to online estimation of wireless signal power attenuation
RCtx
ItotalRC
PP
PPP
,
,
losspower
PRKS: architecture of PRK-based scheduling
Predictable link reliability in PRKS
Convergence of distributed controllers
Comparison with existing protocols
Larger networks
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