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arxiv: 2605.23368 · v1 · pith:KNRRZJG5new · submitted 2026-05-22 · 📡 eess.SP

Energy-Efficient THz Sensing with Hybrid THz/VLC Communication Under Human Blockage Effects

Hanshita Prabhakar , Neetu R.R. , Vivek Ashok Bohara This is my paper

Pith reviewed 2026-05-25 04:00 UTC · model grok-4.3

classification 📡 eess.SP
keywords THz sensingVLChybrid accessenergy efficiencyhuman blockagesISACMILPindoor coverage
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The pith

Hybrid THz/VLC indoor system maintains reliable coverage and high energy efficiency by routing users to VLC access points under blockages.

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

The paper proposes a hybrid indoor framework that pairs a THz sensing access point with hybrid THz communication and VLC access points to offset THz's vulnerability to human blockages and path loss. It first allocates power between the sensing and communication THz links while evaluating monostatic detection, false-alarm, and sensing coverage probabilities under blockages, then minimizes total network power consumption by solving a mixed-integer linear program that activates the fewest VLC access points and sets their powers. Simulations indicate that without blockages most users stay on the THz communication link, yet with blockages the majority shift to VLC links while every user retains service and the network achieves high energy efficiency. The work matters because it shows how the complementary coverage of THz and VLC can support integrated sensing and communication indoors without sacrificing energy performance.

Core claim

The central claim is that optimal power allocation between the THz sensing and THz communication access points, accounting for monostatic sensing metrics under human blockages, followed by mixed-integer linear programming minimization of total network power through selective activation of VLC access points, allows all users to maintain reliable coverage while attaining high energy efficiency; without blockages the majority of users connect to the THz communication link, whereas blockages cause the majority to be served by the VLC links.

What carries the argument

Mixed-integer linear programming optimization that selects active VLC communication access points and assigns their transmit powers, after power allocation between the THz sensing and THz communication access points is set using monostatic sensing metrics under blockages.

If this is right

  • Without blockages most users remain connected to the THz communication access point.
  • With blockages the majority of users are served by the VLC access points.
  • All users maintain reliable coverage in both scenarios.
  • The network achieves high energy efficiency overall.
  • Average energy efficiency, spectral efficiency, sensing rate, and communication rate are reported as performance metrics.
  • pith_inferences

Where Pith is reading between the lines

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

  • The same optimization structure could be tested in multi-room layouts to see whether VLC activation still dominates under realistic mobility.
  • Extending the framework to include user mobility tracking might reveal how quickly the mixed-integer program must be re-solved to keep coverage.
  • The approach suggests that hybrid optical-radio systems can reduce total power by treating VLC as a low-power fallback rather than a permanent parallel layer.
  • Validating the sensing metrics against measured human blockage traces would tighten the link between the model and deployment outcomes.
  • keywords

Load-bearing premise

The monostatic sensing performance metrics under human blockages can be accurately evaluated and the mixed-integer linear program will produce the claimed energy-efficiency gains when applied to real channel conditions.

What would settle it

A physical indoor testbed measurement showing that the achieved energy efficiency falls below the simulated values when actual human movement patterns replace the blockage model, or that coverage drops for some users despite the optimization, would falsify the central claim.

Figures

Figures reproduced from arXiv: 2605.23368 by Hanshita Prabhakar, Neetu R.R., Vivek Ashok Bohara.

Figure 1
Figure 1. Figure 1: THz sensing with hybrid THz/VLC communication under the impact of human [PITH_FULL_IMAGE:figures/full_fig_p008_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Schematic diagram for calculation of blockage distances. [PITH_FULL_IMAGE:figures/full_fig_p012_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Comparison analysis with probability of detection and spectral efficiency of each user in the presence and absence of human blockages. Figs.3(a) and 3(b) present the Pd achieved by each user within the sensing coverage region with and without blockages. A detection threshold of P th d = 0.5 is employed as the criterion for access point association, ensuring a minimum level of reliable user detection. If th… view at source ↗
Figure 5
Figure 5. Figure 5: Probability of detection total N = 10 users with respect to the probability of false alarm in the presence and absence of blockages with different (γsens). satisfactory communication performance despite reduced sensing reliability. The attenuation and scattering introduced by blockages lead to a noticeable reduction in the Pd for several users. This degradation in sensing reliability restricts the users th… view at source ↗
Figure 6
Figure 6. Figure 6: Number of users association from THzc/V LCc − AP with respect to the probability of false alarm in the absence and presence of blockages [PITH_FULL_IMAGE:figures/full_fig_p021_6.png] view at source ↗
Figure 9
Figure 9. Figure 9: Probability of detection and sens￾ing coverage probability of different num￾ber of users with respect to the blockage density [PITH_FULL_IMAGE:figures/full_fig_p022_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Number of users (N = 10) association from THzc/V LCc − AP with respect to Blockage density. 4 5 6 7 8 9 10 No. of Users (N) 1 2 3 4 5 6 7 8 9 10 Avg. Spectral Efficiency (bps/Hz) [PITH_FULL_IMAGE:figures/full_fig_p023_10.png] view at source ↗
Figure 12
Figure 12. Figure 12: Number of users connected to THz/VLC-APs with respect to different room dimensions in the presence and absence of human blockages. via THzc − AP, then the larger fraction of users tend to associate with the V LCc − APs instead of the T Hzc − AP [PITH_FULL_IMAGE:figures/full_fig_p024_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Proposed model comparison op￾timized for average energy efficiency with non-optimized respect to the number of users in the presence and absence of human blockages. 2 4 6 8 Blockage Density ( B ) 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Avg. Energy Efficiency (bps/joule/Hz) Without optimized at N = 6 Without optimized N =10 Proposed at N = 6 Proposed at N = 10 [PITH_FULL_IMAGE:figures/full_fig_p025_13.png] view at source ↗
Figure 15
Figure 15. Figure 15: Comparison analysis of average communication rate with respect to the average sensing rate for different numbers of users in the presence and absence of human blockages. 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 36 38 40 42 44 46 48 50 52 54 [PITH_FULL_IMAGE:figures/full_fig_p026_15.png] view at source ↗
read the original abstract

This paper presents an energy-efficient indoor system integrating \ac{THz} with \ac{VLC}. \ac{THz} communication offers ultra-high-capacity links but is limited by severe path loss, atmospheric absorption, and susceptibility to blockages. In contrast, \ac{VLC} provides robust, wide indoor coverage with illumination support, thereby enabling reliable, high-speed hybrid connectivity. To leverage their respective strengths, we propose a hybrid framework that integrates \ac{$THz_s-AP$} with hybrid \ac{$THz_c/VLC_c-AP$}, enabling reliable coverage and enhancing the \ac{EE} from an \ac{ISAC} perspective. We first perform optimal power allocation between the \ac{$THz_s-AP$} and \ac{$THz_c-AP$} to optimized the set of users served by the \ac{$THz_c-AP$} link, considering monostatic sensing performance metrics such as \ac{$P_d$}, \ac{$FA_p$} and \ac{$SC_p$} under the impact of human blockages are evaluated. Subsequently, the overall network power consumption is minimized via a mixed-integer linear programming (MILP) optimization that optimally selects the active \ac{$VLC_c-APs$} and assigns transmit powers. Furthermore, extensive performance evaluations are conducted to analyze key metrics, including average energy efficiency, average spectral efficiency, average sensing rate, and average communication rate. Simulation results demonstrate that, under \ac{THz} sensing, most users are connected to the \ac{$THz_c-AP$} in the absence of blockages, whereas in the presence of blockages, the majority are served by the \ac{$VLC_c-APs$}. Overall, all users maintain reliable coverage with high \ac{EE}.

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

1 major / 2 minor

Summary. The manuscript proposes a hybrid THz/VLC indoor ISAC system that first optimizes power allocation between a THz sensing AP (THz_s-AP) and a hybrid THz communication AP (THz_c-AP) using monostatic sensing metrics (Pd, FAp, SCp) under human blockages, then applies MILP to select active VLC_c-APs and allocate powers to minimize total network power consumption. Simulations are reported to show that most users connect to the THz_c-AP without blockages but to VLC_c-APs with blockages, while maintaining reliable coverage and high energy efficiency.

Significance. If the blockage-affected sensing metrics and resulting optimization are accurate, the framework could offer a practical approach to combining THz's high capacity with VLC's robustness for blockage mitigation and EE gains in indoor 6G scenarios. The MILP formulation for joint AP selection and power control is a standard tool that, if correctly parameterized, supports reproducible network-level claims.

major comments (1)
  1. [Optimization procedure and simulation results (as described in abstract and power-allocation step)] The central simulation claims on user association (THz_c-AP vs. VLC_c-AP dominance) and EE rest on Pd, FAp, and SCp values produced by the blockage model; however, no channel model, closed-form expressions, or independent validation of these metrics is supplied, so the MILP inputs cannot be verified and any mismatch would invalidate the reported association counts and EE numbers.
minor comments (2)
  1. Acronyms such as THz_s-AP, THz_c-AP, and VLC_c-AP are introduced with LaTeX commands but lack an explicit first-use definition list, which would aid readability.
  2. The abstract states that 'extensive performance evaluations are conducted' for average EE, SE, sensing rate, and communication rate, but no table or figure references are given to support the headline claims.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive feedback on the optimization procedure and its dependence on the sensing metrics. We address the major comment below and will incorporate the requested details in the revised manuscript.

read point-by-point responses

  1. Referee: [Optimization procedure and simulation results (as described in abstract and power-allocation step)] The central simulation claims on user association (THz_c-AP vs. VLC_c-AP dominance) and EE rest on Pd, FAp, and SCp values produced by the blockage model; however, no channel model, closed-form expressions, or independent validation of these metrics is supplied, so the MILP inputs cannot be verified and any mismatch would invalidate the reported association counts and EE numbers.

    Authors: We agree that the current version does not supply the THz channel model under human blockages, the closed-form expressions for the monostatic sensing metrics Pd, FAp, and SCp, or independent validation of those metrics. In the revised manuscript we will add a new subsection that (i) presents the THz propagation and blockage model, (ii) derives the closed-form expressions for Pd, FAp, and SCp as functions of the allocated sensing power and blockage probability, and (iii) validates the expressions against Monte-Carlo simulations. These additions will make the inputs to the power-allocation step and the subsequent MILP fully verifiable and will allow readers to reproduce the reported user-association and EE results. revision: yes

Circularity Check

0 steps flagged

No circularity: sensing metrics evaluated independently before feeding into power allocation and MILP

full rationale

The paper's chain begins with evaluation of monostatic sensing metrics (Pd, FAp, SCp) under human blockages, followed by power allocation between THz_s-AP and THz_c-AP to optimize user sets, then MILP for VLC_c-AP selection and power minimization. No equations or text in the abstract reduce the metrics to outputs of the optimization, nor do they rely on self-citations for uniqueness or ansatz. The simulation claims about user association and EE follow from these sequential steps without the target quantities being defined by construction from the fitted or optimized values themselves. The derivation remains self-contained against external blockage models and standard MILP solvers.

Axiom & Free-Parameter Ledger

2 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard wireless optimization assumptions and blockage modeling; no new entities are introduced and free parameters are the optimized powers and AP selections.

free parameters (2)
  • Power allocation between THz_s-AP and THz_c-AP
    Optimal allocation is performed to serve users while meeting sensing metrics; values are chosen by the optimization procedure.
  • Transmit powers and active set of VLC_c-APs
    Selected via MILP to minimize total network power consumption.
axioms (2)
  • domain assumption Human blockage effects can be modeled such that monostatic sensing metrics Pd, FAp and SCp remain evaluable
    The paper states that these metrics are evaluated under the impact of human blockages.
  • domain assumption MILP formulation yields the globally optimal AP selection and power assignment for the stated objective
    The paper uses MILP to minimize overall network power consumption.

pith-pipeline@v0.9.0 · 5868 in / 1509 out tokens · 29692 ms · 2026-05-25T04:00:44.937133+00:00 · methodology

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Reference graph

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