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Towards Semantic-Aware Transport Layer Protocols: A Control Performance Perspective

Polina Kutsevol, Onur Ayan, Wolfgang Kellerer

TL;DR

This work targets control performance in networked control systems (NCSs) by evaluating transport layer (TL) policies under shared CSMA/CA networks and showing that conventional TL schemes fail to meet control objectives in realistic conditions. It introduces a semantic- and network-aware TL policy that filters updates using process state semantics and network congestion signals, combining ideas from event-triggering and congestion control. The paper further develops an adaptive threshold mechanism for zero-wait event-triggering and demonstrates through a real-time emulation framework that the proposed approach outperforms UDP, TCP, ACP, and content-agnostic ET in both AoI and LQG cost metrics. This cross-layer strategy enables more effective, real-time control over dense networks, contributing to viable NCS designs for 6G-like environments where application-specific goals drive communication decisions.

Abstract

Networked control systems (NCSs) are an example of task-oriented communication systems, where the purpose of communication is real-time control of processes over a network. In the context of NCSs, with the processes sending their state measurements to the remote controllers, the deterioration of control performance due to the network congestion can be partly mitigated by shaping the traffic injected into the network at the transport layer (TL). In this work, we conduct an extensive performance evaluation of selected TL protocols and show that existing approaches from communication and control theories fail to deliver sufficient control performance in realistic network scenarios. Moreover, we propose a new semantic-aware TL policy, which uses the process state information to filter the most relevant updates and the network state information to prevent delays due to network congestion. The proposed mechanism is shown to outperform all the considered TL protocols with respect to control performance.

Towards Semantic-Aware Transport Layer Protocols: A Control Performance Perspective

TL;DR

This work targets control performance in networked control systems (NCSs) by evaluating transport layer (TL) policies under shared CSMA/CA networks and showing that conventional TL schemes fail to meet control objectives in realistic conditions. It introduces a semantic- and network-aware TL policy that filters updates using process state semantics and network congestion signals, combining ideas from event-triggering and congestion control. The paper further develops an adaptive threshold mechanism for zero-wait event-triggering and demonstrates through a real-time emulation framework that the proposed approach outperforms UDP, TCP, ACP, and content-agnostic ET in both AoI and LQG cost metrics. This cross-layer strategy enables more effective, real-time control over dense networks, contributing to viable NCS designs for 6G-like environments where application-specific goals drive communication decisions.

Abstract

Networked control systems (NCSs) are an example of task-oriented communication systems, where the purpose of communication is real-time control of processes over a network. In the context of NCSs, with the processes sending their state measurements to the remote controllers, the deterioration of control performance due to the network congestion can be partly mitigated by shaping the traffic injected into the network at the transport layer (TL). In this work, we conduct an extensive performance evaluation of selected TL protocols and show that existing approaches from communication and control theories fail to deliver sufficient control performance in realistic network scenarios. Moreover, we propose a new semantic-aware TL policy, which uses the process state information to filter the most relevant updates and the network state information to prevent delays due to network congestion. The proposed mechanism is shown to outperform all the considered TL protocols with respect to control performance.
Paper Structure (21 sections, 8 equations, 5 figures)

This paper contains 21 sections, 8 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Related Work
  3. Our Contribution
  4. System Model and Implementation
  5. Control Model
  6. Network Model
  7. Implementation
  8. Control Performance of Existing Transport Layer Protocols
  9. Conventional Transport Layer Protocols
  10. UDP
  11. TCP
  12. Zero-Wait Policy
  13. Age Control Protocol
  14. Network-Unaware Event-Triggering
  15. Numerical results for existing TL protocols
  16. ...and 6 more sections

Figures (5)

  • Figure 1: The considered scenario with $N$ feedback control loops closed over the shared wireless network. In our implementation, we use various TL policies on top of FCFS MAC queue and CSMA/CA access scheme.
  • Figure 2: Average AoI and its 99% confidence interval for UDP, TCP, zero-wait (ZW), event-triggering (ET) and age control protocol (ACP) policies.
  • Figure 3: Average LQG cost and its 99% confidence interval for UDP, TCP, ZW, ET and ACP policies. AoI-based ACP from shreedhar2019age outperforms other techniques for $N=8$ and $N=12.$
  • Figure 4: Average AoI and its 99% confidence intervals for zero-wait event-triggering (ZW ET) with different thresholds, adaptive threshold (AT) and ACP.
  • Figure 5: Average LQG cost and its 99% confidence intervals for ZW ET with different thresholds, AT and ACP. Semantic- and network-aware techniques outperform ACP, which aims at improving information freshness.