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arxiv: 2509.06454 · v1 · submitted 2025-09-08 · 💻 cs.NI

Empirical Evaluation of a 5G Transparent Clock for Time Synchronization in a TSN-5G Network

Julia Caleya-Sanchez , Pablo Mu\~noz , Jorge S\'anchez-Garrido , Emilio Florent\'in , Felix Delgado-Ferro , Pablo Rodriguez-Martin , Pablo Ameigeiras This is my paper

Pith reviewed 2026-05-18 18:35 UTC · model grok-4.3

classification 💻 cs.NI
keywords time synchronizationTSN5Gtransparent clockPTPindustrial IoTresidence time
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The pith

A 5G transparent clock in a TSN network achieves 500 ns peak-to-peak synchronization accuracy on commercial equipment.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper tests whether a transparent clock can deliver the sub-microsecond timing needed for industrial applications when 5G is inserted into a Time-Sensitive Networking path. It implements residence-time correction inside the 5G segment and restores the original clock domain at the slave node, then measures performance while varying Precision Time Protocol message rates. Results show that peak-to-peak offsets remain near 500 ns, comfortably under the 1 µs industrial limit. A sympathetic reader cares because many factory automation and robotics tasks fail if end-to-end jitter exceeds that threshold.

Core claim

An end-to-end 5G transparent clock, built on commercial TSN switches that share a single clock, computes residence time across the 5G link and recovers the master clock domain at the slave; this yields 500 ns peak-to-peak synchronization error that satisfies the <1 µs requirement when PTP message rates are chosen appropriately.

What carries the argument

Transparent clock that measures and subtracts residence time inside the 5G segment while preserving the original clock domain for the downstream TSN link.

If this is right

  • Specific PTP message transmission rates minimize synchronization offsets.
  • The measured accuracy meets requirements for industrial IoT and Industry 4.0/5.0 coordination.
  • Commercial TSN switches can be used without custom hardware for the transparent-clock function.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same residence-time approach might scale to more complex 5G topologies if the single-clock assumption is relaxed.
  • Integration with other time-sensitive protocols beyond PTP could follow once the basic accuracy is confirmed.

Load-bearing premise

The single-clock commercial testbed fully captures real-world jitter, asymmetric delays, and multi-hop behavior without hidden variables.

What would settle it

Repeating the measurements on a multi-hop 5G-TSN chain that includes asymmetric wireless delays and observes whether peak-to-peak error stays below 1 µs.

Figures

Figures reproduced from arXiv: 2509.06454 by Emilio Florent\'in, Felix Delgado-Ferro, Jorge S\'anchez-Garrido, Julia Caleya-Sanchez, Pablo Ameigeiras, Pablo Mu\~noz, Pablo Rodriguez-Martin.

Figure 1
Figure 1. Figure 1: Architecture of the integrated TSN-5G network [4] [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: The TSN system includes a TSN Master, synchro [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: End-to-End Transparent Clock messages exchange [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: TSN-5G testbed dres,down and dres,up mitigate the associated problem of having different latencies in UL and DL. The TSN Slave requires a response time (dresponse) after receiving the “Sync” before generating the “Delay Request”, as shown in [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Synchronization distribution for 1 packet/s rate [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
read the original abstract

Time synchronization is essential for industrial IoT and Industry 4.0/5.0 applications, but achieving high synchronization accuracy in Time-Sensitive Networking (TSN)-5G networks is challenging due to jitter and asymmetric delays. 3GPP TS 23.501 defines three 5G synchronization modes: time-aware system, boundary clock (BC), and transparent clock (TC), where TC offers a promising solution. However, to the best of our knowledge, there is no empirical evaluation of TC in a TSN-5G network. This paper empirically evaluates an 5G end-to-end TC in a TSN-5G network, implemented on commercial TSN switches with a single clock. For TC development, we compute the residence time in 5G and recover the clock domain at the slave node. We deploy a TSN-5G testbed with commercial equipment for synchronization evaluation by modifying the Precision Timing Protocol (PTP) message transmission rates. Experimental results show a peak-to-peak synchronization of 500 ns, meeting the industrial requirement of < 1 us, with minimal synchronization offsets for specific PTP message transmission rates.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper claims to provide the first empirical evaluation of a 5G transparent clock (TC) in a TSN-5G network on commercial TSN switches using a single shared clock. Residence time is computed inside the 5G segment and the clock domain recovered at the slave; by varying PTP message transmission rates, the authors report a peak-to-peak synchronization accuracy of 500 ns that meets the industrial <1 µs requirement.

Significance. If the measured accuracy holds under the stated conditions, the work supplies the first concrete empirical data point for the transparent-clock mode of 3GPP TS 23.501 in an integrated TSN-5G setting. The use of commercial hardware and explicit residence-time implementation offers a practical reference for industrial IoT deployments that need sub-microsecond timing.

major comments (2)
  1. [Experimental Setup] Experimental Setup (single-clock testbed): the deployment uses one shared clock, thereby eliminating independent oscillator drift, variable queuing across separate gNB/UPF/UE functions, and path asymmetry. Because the headline claim is that the observed 500 ns peak-to-peak meets industrial requirements, this simplification is load-bearing; the measured offset distribution cannot be taken as representative without additional justification or multi-clock experiments.
  2. [Results] Results section: the 500 ns peak-to-peak figure is presented without error bars, standard deviation, number of runs, or any statistical characterization of variability across PTP rate settings. This absence directly weakens the supporting statement that offsets are “minimal” for specific rates and reduces confidence in the soundness of the experimental outcome.
minor comments (2)
  1. [Abstract] Abstract and §4: state the exact PTP message rates that produced the lowest offsets so that the result can be reproduced.
  2. [TC Implementation] Clarify in the residence-time computation description whether any 3GPP-specific corrections (e.g., for 5G internal delays) are applied beyond the standard PTP transparent-clock formula.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and constructive feedback on our work. We provide detailed responses to each major comment and outline the revisions we intend to make to address the concerns raised.

read point-by-point responses

  1. Referee: [Experimental Setup] Experimental Setup (single-clock testbed): the deployment uses one shared clock, thereby eliminating independent oscillator drift, variable queuing across separate gNB/UPF/UE functions, and path asymmetry. Because the headline claim is that the observed 500 ns peak-to-peak meets industrial requirements, this simplification is load-bearing; the measured offset distribution cannot be taken as representative without additional justification or multi-clock experiments.

    Authors: We agree that the single-clock testbed simplifies the evaluation by removing independent oscillator drift, variable queuing, and path asymmetry. This was a deliberate choice to provide the first empirical data on the 5G TC implementation using commercial TSN switches, isolating the residence time computation and clock recovery aspects. In the revision, we will expand the Experimental Setup section to include additional justification for this approach as a foundational study and explicitly discuss its limitations regarding representativeness in more complex deployments. We will also add text in the conclusions regarding the need for future multi-clock experiments to validate broader applicability. This addresses the concern without requiring new hardware setups at this stage. revision: partial

  2. Referee: [Results] Results section: the 500 ns peak-to-peak figure is presented without error bars, standard deviation, number of runs, or any statistical characterization of variability across PTP rate settings. This absence directly weakens the supporting statement that offsets are “minimal” for specific rates and reduces confidence in the soundness of the experimental outcome.

    Authors: We concur that the Results section would benefit from more rigorous statistical presentation. We will revise the manuscript to include error bars on the relevant figures, report standard deviations for the synchronization offsets, specify the number of runs conducted for each PTP rate, and provide additional analysis of variability. These changes will better support our statements regarding minimal offsets at particular rates and enhance the credibility of the experimental findings. revision: yes

Circularity Check

0 steps flagged

Purely empirical measurement; no derivation or prediction present

full rationale

The paper reports direct experimental measurements of PTP synchronization accuracy (peak-to-peak 500 ns) on a commercial TSN-5G testbed implementing a 5G transparent clock. Residence time is computed per standard 3GPP TS 23.501 and PTP definitions; clock recovery at the slave follows the same protocol. No equations, first-principles derivations, fitted parameters, or predictions are introduced that could reduce to self-defined inputs or self-citations. The work is self-contained against external benchmarks (industrial <1 µs requirement) and uses unmodified commercial equipment and standard protocols.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Work rests on standard PTP protocol assumptions and 3GPP TS 23.501 definitions with experimental modifications to message rates; no new physical entities or ad-hoc constants introduced beyond choosing transmission rates for evaluation.

free parameters (1)
  • PTP message transmission rates
    Varied experimentally to identify rates yielding minimal synchronization offsets
axioms (1)
  • domain assumption Commercial TSN switches and 5G equipment correctly implement boundary and transparent clock functions per 3GPP and IEEE standards
    Invoked when assuming single-clock setup and residence-time recovery behave as specified

pith-pipeline@v0.9.0 · 5767 in / 1213 out tokens · 39956 ms · 2026-05-18T18:35:39.518829+00:00 · methodology

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Reference graph

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