REVIEW 3 major objections 6 minor 32 references
A soft actor-critic agent can jointly allocate subchannels, power, and RIS phases in shared-spectrum local networks, reaching about 96% of an exhaustive-search benchmark's utility at far lower computational cost.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
SAC-based deep reinforcement learning jointly allocates subchannels, power, and RIS phases in a multi-operator spectrum-sharing setting, outperforming DDPG and approaching an exhaustive-search benchmark in simulation.
T0 review reviewed 2026-08-02 challenge →
load-bearing objection Useful engineering framework with a genuinely new problem formulation, but the headline 'near-optimal' claim rests on a benchmark that never optimizes RIS phases, so the 96% number is not evidence of near-optimality. the 3 major comments →
DRL-Based Spectrum Sharing for RIS-Aided Local High-Quality Wireless Networks
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
Core claim
The paper's central claim is that the mixed-integer utility-maximization problem for RIS-aided multi-VSP spectrum sharing—maximizing VSP revenue minus spectrum, RIS, and power costs under QoS constraints—can be solved nearly optimally by a SAC-based agent. The agent observes full CSI, achieved rates, and the previous action; its actor outputs a continuous vector that is projected onto the feasible action set by thresholding and clipping, covering subchannel assignment, BS association, transmit powers, and RIS phases. In simulations with two VSPs, up to twelve users, and a sixteen-element RIS, SAC attains approximately 96 percent of the EDS-SCA benchmark reward and outperforms DDPG in converg
What carries the argument
The carrying mechanism is the MDP formulation plus the SAC learning rule. The state stacks instantaneous CSI for direct, base-station-to-RIS, and RIS-to-user links, achieved user rates, and the previous feasible action to preserve the Markov property. The action space is hybrid; the actor outputs continuous relaxations that a deterministic projection maps into feasible binary subchannel and association decisions and bounded power and phase values. SAC's entropy-regularized objective with twin critics and an automatically tuned temperature provides stable exploration over the combinatorial decisions, while the EDS-SCA benchmark—exhaustive enumeration of discrete variables followed by successi
Load-bearing premise
The load-bearing premise is that the agent can observe perfect instantaneous channel state information for every direct, base-station-to-RIS, and RIS-to-user link at each time step, so the learned policy's near-optimal performance has not been shown to survive channel-estimation error, delayed feedback, or mobility.
What would settle it
Train the identical SAC agent on the same simulated network, but replace the perfect CSI in the state with noisy estimates (for example, independent Gaussian errors calibrated to a realistic pilot-based estimator) or delay the state by one time slot. If the attained utility falls substantially below the claimed 96 percent of the EDS benchmark—say, below 80 percent—the central deployability claim is falsified.
If this is right
- eLSA-style dynamic spectrum sharing among vertical service providers could run at runtime, since online decisions reduce to neural-network inference rather than combinatorial search.
- RIS leasing becomes economically attractive: with phase configuration optimized by the same policy, VSP utility improves enough to offset the leasing cost.
- Spectrum partitioning policy is a first-order lever: dedicated subchannels can raise utility several-fold over heavily shared ones, giving operators guidance on reuse factors.
- The MDP-and-projection recipe is a template for larger, multi-antenna or multi-RIS deployments where exhaustive benchmarks are infeasible.
Where Pith is reading between the lines
- The EDS benchmark fixes RIS phases during enumeration, so the 96 percent figure likely understates the joint phase-optimization benefit; a benchmark that also searches phases might shift the comparison.
- The perfect-CSI state assumption is the main gap between simulation and deployment; training the same agent under channel-estimation noise and measuring how the 96 percent degrades would test deployability.
- Because RIS-BS association is fixed by proximity rather than optimized, the reported gains may not capture the full value of RIS placement; making association a decision variable could close part of that gap.
- The same MDP-and-projection approach could extend to uplink/downlink joint scheduling or multi-cell coordination, which share the hybrid action-space structure.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a deep reinforcement learning (DRL) framework for joint subchannel assignment, transmit power control, and RIS phase configuration in an eLSA-based multi-VSP spectrum-sharing system. The resource allocation problem is formulated as a mixed-integer nonlinear program (MINLP) with QoS constraints and economic costs, then modeled as a Markov decision process. Two DRL algorithms, DDPG and SAC, are tailored to the hybrid discrete-continuous action space via a feasibility projection. Numerical results compare the DRL policies against an exhaustive discrete search (EDS) with SCA-based power refinement, reporting that SAC reaches roughly 96% of the benchmark reward for M1=16 and outperforms DDPG in stability and convergence. The paper concludes that the SAC-based solution is near-optimal and suitable for real-time deployment.
Significance. If the central near-optimality claim were supported, the paper would make a useful contribution by addressing a timely problem: scalable DRL-based resource management for RIS-assisted spectrum sharing in local high-quality networks. The paper has several strengths: a detailed system and MDP formulation, explicit treatment of the hybrid discrete-continuous action space through projection, a constrained EDS-SCA benchmark, and ablation studies on learning-rate and mini-batch sensitivity. However, the main quantitative claim, that SAC attains approximately 96% of the near-optimal benchmark, is currently not supported because the benchmark never optimizes the RIS phase variables that are part of the original problem and of the DRL action space. This is a load-bearing issue that affects the abstract, the numerical results, and the conclusion. The paper also leaves open questions about QoS feasibility of the learned policies and about robustness to imperfect CSI, both of which are relevant to the stated deployability claim.
major comments (3)
- [Section III-D and Section IV-C] The EDS benchmark does not optimize RIS phases. Section III-D states that during the exhaustive enumeration of (ω, φ) the transmit power is fixed to a uniform allocation and the RIS phase shifts are kept fixed; the SCA refinement in (56) optimizes only p. However, the original problem (20d) includes θ as a decision variable, and the DRL action (29) and the complexity expressions (58)-(59) explicitly include θ. Therefore the reported '96% of the benchmark reward' is a ratio against a θ-fixed baseline, not an upper bound on problem (20), and the 'near-optimal' wording in the abstract, Section IV-C, and the conclusion is unsupported. Please either augment the benchmark to optimize θ (e.g., alternating SCA over p and θ) or explicitly reframe all near-optimal claims as 'within 96% of EDS with fixed RIS phases'.
- [Section II-C, Eq. (20b) and Section III-A.4, Eq. (31)] The QoS constraints are hard constraints in the optimization problem (20b), but the DRL reward enforces them only through a penalty term λ_qos max(0, R^th - R). The EDS-SCA benchmark, by contrast, enforces the QoS constraints directly in (56b). The paper does not report QoS violation rates for the SAC or DDPG policies. If the learned policies violate the constraints, the penalized reward is not the same objective as (20a), so the comparison against the constrained benchmark is not apples-to-apples. Please report the fraction of users meeting R^th and, if necessary, restrict the comparison to feasible policies or use a constrained projection for the QoS requirements.
- [Section IV-B and Eq. (26)-(27)] The state space assumes perfect instantaneous CSI for all direct, BS-RIS, and RIS-user links at every time slot, and the simulator provides this information exactly. The paper's concluding claim is that the framework enables low-complexity real-time decision-making, but no experiment addresses CSI estimation error, delayed feedback, or mobility, even though cascaded RIS channel acquisition is known to be expensive and noisy. As it stands, the results are an idealized upper-bound study rather than evidence of deployability. Please either add a robustness experiment under imperfect CSI or explicitly state that the contribution is limited to the perfect-CSI idealized setting and soften the deployment claims accordingly.
minor comments (6)
- [Abstract] Typographical spacing issue: 'reaching up to96%' should read 'reaching up to 96%'.
- [Section III-D paragraph before Eq. (49)] The notation G_b,k^c depends on ω, φ, and θ but the dependence on the fixed θ is not written explicitly. This makes the SCA derivation harder to follow; please write G_b,k^c(θ) or state clearly that θ is fixed throughout the benchmark.
- [Section III-E, Eq. (58)] The action-dimension expression contains two identical terms V B_v K_v C, presumably representing scheduling and power, plus J M_j for RIS phases. However, the action vector in (29) also includes BS association φ and the text mentions RIS association d, which are not reflected in (58). Please clarify what is included in the action dimension and why φ is omitted.
- [Section II-B, Eq. (8)] The notation M_j is used both as the cardinality of the reflecting elements and as an index set through '∀m ∈ M_j'. Please use a distinct symbol, e.g., {1,...,M_j}, for the index set.
- [Section IV-D, Fig. 5] The text says the reusable subchannel case uses C_r=2, but the legend includes configurations such as C_d=0, C_r=3. The description and figure are inconsistent; please align the legend entries with the text.
- [Section II-C, Eq. (20c)] Constraint (20c) says 'ω, φ, ∀v,b,k,c,j', but j is not present in ω or φ. The 'j' is likely a typo; the RIS-association variable d, if used, should be explicitly included in the set of optimization variables.
Circularity Check
No circular reduction found; the 96% near-optimal claim is weakened by a benchmark that fixes RIS phases, but that is a benchmarking limitation, not circularity.
full rationale
The paper's chain is: formulate MINLP (20), recast as MDP with state (26)-(27), action (29), and reward (31), train SAC/DDPG, compare against the EDS+SCA benchmark (Section III-D), and report that SAC attains about 96% of the EDS reward for M1=16. I find no step in which an output is defined in terms of an input, no fitted parameter is relabeled as a prediction, and no load-bearing argument rests on a self-citation. The RL agent maximizes the same reward (31) on which it is later evaluated; this is standard RL practice and does not reduce the comparison to construction, because the EDS benchmark and the learned policies are computed independently on the same utility function and channel realizations. The closest concern is that the EDS benchmark keeps RIS phase shifts fixed during enumeration and its SCA refinement (56) optimizes only p, whereas the original problem (20d) treats the RIS phases as decision variables and the SAC action (29) includes them. Therefore the reported 96% does not rigorously establish near-optimality for the full problem (20); it establishes closeness to a RIS-phase-fixed reference. That is a benchmark-validity or overclaiming issue, not a circularity. Self-citations such as [8], [13]-[16], and [24] appear only as background and are not load-bearing, and no uniqueness theorem or ansatz is imported from the authors' prior work.
Axiom & Free-Parameter Ledger
free parameters (6)
- Profit coefficient beta_v and scaling factors Phi_1, Phi_2
- Subchannel prices lambda_r, lambda_d =
0.2, 0.5
- RIS leasing cost psi_j =
0.3
- Power cost coefficient alpha_power =
0.1
- QoS penalty coefficient lambda_qos =
50
- Path-loss exponent beta =
2.5
axioms (6)
- domain assumption Perfect instantaneous CSI of all direct, BS-RIS, and RIS-user links is available to the agent at every slot.
- domain assumption Links between users and non-associated RISs are negligible; each user benefits from at most one RIS.
- domain assumption The environment is quasi-static with i.i.d. Rayleigh fading; training and evaluation share the same distribution.
- domain assumption The feasibility projection Pi_F exactly enforces constraints (2)-(7) through thresholding, clipping, and normalization.
- standard math Standard Shannon-rate SINR model and convex SCA lower bound are valid.
- ad hoc to paper RIS phase shifts are frequency-independent and identical across all subchannels.
Cite this review
Pith. "Pith review of DRL-Based Spectrum Sharing for RIS-Aided Local High-Quality Wireless Networks." pith.science (2026). https://pith.science/paper/PAF5FKRM
@misc{pith2026260325332,
author = {Pith},
title = {Pith review of: DRL-Based Spectrum Sharing for RIS-Aided Local High-Quality Wireless Networks},
year = {2026},
howpublished = {\url{https://pith.science/paper/PAF5FKRM}},
note = {Machine review of arXiv:2603.25332}
}
read the original abstract
This paper investigates a smart spectrum-sharing framework for reconfigurable intelligent surface (RIS)-aided local high-quality wireless networks (LHQWNs) within a mobile network operator (MNO) ecosystem. Although RISs are often considered harmful due to interference, this work shows that properly controlled RISs can enhance quality of service (QoS). The proposed system enables temporary spectrum access for multiple vertical service providers (VSPs) by dynamically allocating radio resources. The spectrum is divided into dedicated subchannels assigned to individual VSPs and reusable subchannels shared among multiple VSPs, while RIS improves propagation conditions and zero-forcing (ZF) precoding is adopted at the multiantenna base station (BS) to cancel inter-user interference. We formulate a multi-VSP utility maximization problem that jointly optimizes subchannel assignment, transmit power, and RIS phase configuration while accounting for spectrum access costs, RIS leasing costs, and QoS constraints. The resulting mixed-integer non-linear program (MINLP) is modeled as a Markov decision process (MDP) and solved using deep reinforcement learning (DRL). Deep deterministic policy gradient (DDPG) and soft actor-critic (SAC) algorithms are developed and compared. Numerical results show that SAC generally outperforms DDPG in convergence, stability, and utility, particularly in larger-scale scenarios. In the reduced-scale ablation study, both joint DRL methods outperform the heuristic benchmark by at least 6.6% in final moving-average reward.
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This paper was first reviewed by deepseek-v4-flash on August 2, 2026.
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