Cyber Physical Interface and Automation

Course Overview

• 18ECE350T Cyber Physical Interface and Automation
• Course Instructor: Dr. S. Sunithamani
• Credits: 3

Course Articulation Matrix

• Course Learning Outcomes (CLO):
  • Appreciate the features of localization in wireless sensor networks using CPS
  • Synthesize feedback control systems for CPS
  • Analyze security issues in CPS
  • Design real-time scheduling algorithms for CPS
  • Apply automated concepts in medical CPS

Assessment

• Continuous Internal Evaluation (50% weightage)
• Semester End Examination (50% weightage)

Unit I: Cyber-Physical Systems Built on Wireless Sensor Networks

• Introduction and Motivation
  • Cyber-physical systems (CPS) integrate computation, networking, and physical processes
  • CPS merge digital and physical functionalities to monitor and control physical processes
  • Applications include manufacturing, transportation, healthcare, and smart infrastructure
• System Description and Operational Scenarios
  • Wireless sensor networks (WSNs) serve as a foundational infrastructure for CPS
  • WSNs enable real-time monitoring, control, and optimization of physical systems
  • Applications include smart homes, surveillance, tracking, and environmental science
• Medium Access Control (MAC)
  • MAC protocol coordinates node actions over a shared channel
  • Energy conservation is crucial in WSNs
  • MAC protocols are optimized for low power consumption, collision avoidance, and small code size
• Routing
  • Multi-hop routing is critical for WSNs
  • WSNs operate in open environments with packet errors and asymmetry in connectivity
  • Routing protocols must adapt to these constraints### Routing in Wireless Sensor Networks
• Nodes calculate the next hop based on progress toward the destination using distance formulas, considering factors like time delays, link reliability, and energy.
• Directed diffusion integrates routing, queries, and data aggregation to reduce communication costs and enhance routing robustness.
• It adapts to environmental changes, making it a suitable framework for addressing various challenges in cyber-physical systems (CPS).

Reliability in WSN

• Ensuring high reliability on each link is crucial due to multi-hop message transmission.
• Nodes choose high-quality links for next hops and may increase power or wait for environmental changes to improve link quality.
• Retries and waiting out burst loss conditions also enhance hop-by-hop reliability.

Voids in WSN

• Voids occur in WSNs when no forwarding nodes are within range in the desired direction due to node failures, obstacles, or sleep states.
• Protocols like greedy perimeter stateless routing (GPSR) address voids by selecting alternative nodes using methods like the left-hand rule to find new routes.

Node Localization

• Node localization involves determining the geographical positions of each node within the network.
• Factors affecting localization include hardware costs, beacon nodes, required accuracy levels, environmental conditions, dimensionality, energy constraints, time efficiency, clock synchronization, and security concerns.
• Approaches include GPS capabilities, "walking GPS," and range-based and range-free schemes.

Clock Synchronization

• Clock synchronization is crucial to ensure consistent time readings within a certain margin of error.
• Specialized protocols like Reference Broadcast Synchronization (RBS), Timing-Sync Protocol for System Networks (TPSN), and Flooding Time Synchronization Protocol (FTSP) have been developed for WSNs.
• RBS achieves accuracies of about 30 microseconds for 1 hop, while TPSN achieves an accuracy of around 17 microseconds.

Power Management

• Power management is crucial in WSNs due to limited battery life.
• Approaches include hardware improvements, low-power circuits and microcontrollers, and power-saving states.
• Strategies like optimizing MAC protocols, efficient routing, neighbor discovery, time synchronization, and message reduction techniques contribute to prolonging node lifetimes.

Key Design Drivers and Quality Attributes

• Cyber-Physical System (CPS) solutions in sensor networks require consideration of various key design drivers and quality attributes.
• Examples include physical awareness, real-time responsiveness, validation capabilities, and security measures.

Physically Aware

• Cyber-technologies must possess physical awareness to understand the environment and account for physical world properties that impact system correctness and performance.
• Examples include GPSR, which addresses voids in the network, and MANET solutions that lack physical awareness.

Real-Time Aware

• Cyber-Physical Systems (CPS) in open environments face a range of timing constraints, from soft real-time to safety-critical.
• Research focuses on addressing real-time issues in CPS, including protocols like RAP, SPEED, RI-EDF, and others that provide real-time guarantees.

Runtime Validation Aware

• Cyber-Physical Systems (CPS) must operate reliably and continuously due to the high cost of system failures.
• Techniques like eScan and congestion detection and avoidance (CODA) improve the robustness of individual components, but fail to validate overall high-level functionality of the application.
• Self-healing applications strive for continuous operation but have not yet demonstrated adherence to key high-level functional requirements.### Cyber-Physical Interface and Automation

Runtime Validation Aware WSN Health-Monitoring and Runtime Assurance

• WSN health-monitoring systems (e.g., LiveNet, Memento, and MANNA) focus on low-level components and do not ensure that high-level application requirements are continuously met.
• Future Cyber-Physical Systems (CPS) built on WSNs will need more than low-level monitoring, requiring continuous or periodic runtime validation to adapt to environmental and functional changes.

Runtime Assurance (RTA) vs. Network Health Monitoring

• Runtime Assurance (RTA) and network health monitoring serve different purposes in ensuring the reliability of Wireless Sensor Networks (WSNs).
• Network health monitoring detects and reports low-level hardware faults, like node or route failures.
• RTA uses end-to-end application-level tests, offering two main advantages:
  • Fewer false positives: RTA tests only the necessary components for correct system operation, reducing unnecessary maintenance dispatches.
  • Fewer false negatives: RTA detects subtle failures like topological changes, clock drift, and new environmental obstacles that impact communication or sensing.

Cyber-Physical Systems Built on Wireless Sensor Networks

• Cyber-Physical Systems (CPS) face increased vulnerability to security attacks due to their openness and wireless accessibility in open environments.
• Ensuring security in CPS is critical due to their involvement in essential and safety-critical operations.
• Standard security properties needed include confidentiality, integrity, authenticity, identification, authorization, access control, availability, auditability, tamper resistance, and non-repudiation.

Security Challenges in CPS

• Security solutions for Wireless Sensor Networks (WSNs), a component of CPS, have seen limited success.
• Proposed solutions are often piecemeal and address specific layers like physical, networking, and middleware.
• Physical Layer Attacks:
  • Destroying or disabling devices to create a denial of service.
  • Probing devices to extract secret keys, enabling attackers to create clones that can masquerade as the original devices.
• Countermeasures:
  • Tamper-resistant packaging
  • Better attack detection
  • Fault recovery mechanisms
  • Reducing reliance on external components
  • Erasing memory upon detecting tampering
  • Shielding circuits by distributing components
  • Encrypting bus traffic
  • Randomizing data values and timing to combat side-channel attacks.

Security Issues Above the Physical Layer in CPS

• Implementing security solutions for each protocol is often impractical.
• An alternative is dynamic adaptation based on detected attacks.
• Secure Implicit Geographic Forwarding (SIGF) is a family of routing protocols for WSNs that operates efficiently without attacks and employs stronger defenses when attacks are detected.

Practitioners' Implications (Case Study)

• Group abstractions, such as Hood and abstract regions, have limitations, including inability to handle diverse networks, support for actuators, or adapt to mobile devices.
• The Bundle abstraction addresses some CPS programming challenges, but lacks completeness in correctness semantics, dependency detection and resolution, and explicit real-time and environment abstraction support.

Summary and Open Challenges

• Cyber-Physical Systems (CPS) based on Wireless Sensor Networks (WSN) hold significant potential across various application domains.
• A new multidisciplinary research field is emerging to tackle the challenges posed by CPS, necessitating innovative cyber-physical solutions.
• Open challenges include:
  • Developing effective sensing, decision-making, and control architectures
  • Designing new multichannel MAC protocols with real-time guarantees
  • Implementing routing solutions that account for the dynamics of wireless and mobile nodes
  • Creating indoor localization techniques with high precision, low power consumption, and minimal variance in accuracy across network nodes
  • Establishing efficient and highly accurate clock synchronization methods suitable for large-scale networks
  • Developing strategies to assess the impact of the physical environment on the cyber world
  • Implementing solutions that ensure adherence to timing and safety-critical constraints
  • Introducing new runtime validation mechanisms for long-lived CPS
  • Enhancing security measures for resource-limited systems
  • Designing high-level programming abstractions that simplify programming tasks while retaining essential details for demonstrating correctness concerning application performance and semantics.