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Transcript of Tufts Wireless Laboratory School Of Engineering Tufts University “Network QoS Management in...
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
“Network QoS Management in Cyber-Physical Systems”
Nicole Ng
04/19/23 1
by Feng Xia, Longhua Ma, Jinxiang Dong, and Youxian Sun
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Goal of the paper• New generation of engineered systems => CPS• Major challenge that needs to be addressed:
QoS (Network Quality of Service)• WSANs (Wireless Sensor/Actuator Networks)
will play an essential role in CPS• Goal: Examine characteristics of WSANS and
requirements of QoS in context of CPS
04/19/23 2
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Network Design in CPS• CPS – “integrations of computation, networking, and physical
dynamics, in which embedded devices are networked to sense, monitor, and control the physical world
• Massive networking of embedded computing devices => CPS system
• WSANs => serve as underlying network infrastructure for CPS
04/19/23 3
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
The Vision for CPS
• Large number of embedded devices interconnected through WSANs that make up various autonomous subsystems
• CPS may be composed of many subsystems• To share information globally, WSANs are connected to
the internet• Cyber-physical city: cyber-physical subsystems for health
care, smart home, intelligent transportation, facilities maintenance, public security
04/19/23 4
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Physical Topology of a CPS
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•WSANS serve as the interface between the cyber system and the physical system
•WSANs enable cyber systems to monitor and manipulate behavior of the physical world
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
WSAN and QoS requirements• WSANs – new generation of sensor networks, coexistence of sensors and
actuators, active information gathering infrastructure• Characteristics
– Resource constraints• Energy conservation is critically important for extending the lifetime of the network
– Platform heterogeneity• For large-scale CPS, hardware and networking technologies used in underlying WSAN’s
may differ from one subsystem to another
– Dynamic network topology• During runtime, new nodes may be added or removed
– Mixed traffic• Diverse applications may need to share same WSAN that induce periodic and aperiodic
data• Sensors for different kinds of physical variables
04/19/23 6
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
WSAN and QoS requirements for CPS
• CPS is application-oriented– Different applications have different QoS requirements
• QoS – capability to provide assurance that service requirements of applications can be satisfied
• Existing QoS mechanisms may not be applicable to WSANs in context of CPS => more research needs to be done in this area
04/19/23 7
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
SOA• SOA – (Service-oriented architecture) architectural style
encompassing set of services for building complex systems of systems– Model where functionality is broken down into small distinct units
(services)
• Need to identify and specify services– Categories of services that should be classified
– Functionality, interface, and properties of each service
– Quality levels relevant to performance requirements
– Dealing with different between sensors and actuators when specifying services
04/19/23 8
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Communication Protocols• Paper looks at MAC (medium access control), routing, and transport
protocols• To efficiently support QoS in WSANs, protocols need to be
designed keeping in mind the heterogeneity between sensors and actuators involved in CPS => QoS-aware MAC, routing, and transport protocols developed for WSNs not suitable for WSANs
• Necessary for new QoS mechanisms to be layered on top of existing networks
04/19/23 9
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Resource Management in WSANs• Resource budgets need to be guaranteed in order to
meet certain QoS levels• Higher level of QoS = need for more resources (ex. CPU
time, memory size, bandwidth and/or energy)• Resource management in WSANs is challenging
– Complexity of CPS, dynamic feature of the networks, unpredictable and changing environments
– Need self-management technologies
04/19/23 10
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Energy Conservation• Major concern in WSANs
– Lifetime of nodes restricted by battery energy– Need to minimize energy consumption and maximize
QoS, but these are two conflicting requirements– In-network computation can be exploited to reduce
energy consumption of nodes (reduce traffic load at cost of slightly increased computation in each node)
04/19/23 11
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Possible Solution: Feedback Scheduling
• Previous work shows that feedback scheduling can handle uncertainties in resource availability by automatically adapting to dynamic changes
• Role of feedback scheduler: dynamically adjust specific scheduling parameters of relevant traffic to maintain desired QoS level
04/19/23 12
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Feedback Scheduling Framework
• System output (QoS parameter) = controlled variable• Adjustable scheduling parameters = manipulated variable• Desired value of QoS parameter = setpoint
04/19/23 13
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
An Example: A Simple WSAN• s1, s2, s3 and s4 are source (sensor) nodes• s3 is an interfering source node• s6 is an immediate node• a1 and a2 are actuator nodes
04/19/23 14
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
A Simple WSAN
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• The nodes compete for the use of the same wireless channel for data transmission
• Utilized communication protocol is ZigBee with date rate of 250 kbps
• Size of data packets transmitted is 45 bytes
• Sampling period for each source node is 10 ms
• Running the system:
• At the beginning all nodes except s3, s4, and s5 are active
• s5 is switched on at time t = 20s and off at t = 40s
• s3 and s4 are off until t = 60s
• In real-time CPS, DMR (deadline miss ratio) from each source node to actuator is a major concern
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Deadline miss ratios without QoS management
04/19/23 16
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Deadline miss ratios with QoS management
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•Controlled variable is deadline miss ratio
•Manipulated variable is sampling period of sensor
Tufts Wireless LaboratorySchool Of Engineering
Tufts University
Conclusion• Many issues and challenges to implement CPS• This paper focused on one of those challenges:
network QoS management• Feedback scheduling framework proposed as a
sample solution
04/19/23 18