REVIEW 4 major objections 5 minor 32 references
Average Reward Reinforcement Learning for Wireless Radio Resource Management
T0 review · 4 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash
Pith's one-line read The paper claims that the standard discounted-reward RL formulation is misaligned with wireless RRM objectives and shows that an average-reward version of SAC closes the gap with a 15% gain.
desk verdict The mismatch story is real, but the proposed ARO-SAC is not SAC, so the 15% gain is confounded. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the average-reward TD error and the trainable average reward estimator $\rho$. In discounted SAC the TD target is $r + \gamma \min_i Q_{\phi_{targ,i}}(s', \tilde a')$; in ARO-SAC it becomes $r - \rho + \min_i Q_{\phi_{targ,i}}(s', \tilde a')$. The estimator $\rho$ is trained by gradient descent on $\varepsilon_t = r(s_t,a_t) - \rho_t - \min(Q_1(s_t,a_t), Q_2(s_t,a_t))$, following the off-policy estimation strategy from ARO-DDPG. This machinery replaces geometric discounting of future rewards with a constant subtraction of the estimated average reward, making the value function measure deviations from the long-term average rather than a shrinking tail. It is what lets the policy optimize the undiscounted objective without setting the discount factor to one.
What would settle it
Train ARO-SAC and discounted SAC on a synthetic MDP whose optimal average reward per step is known analytically; if ARO-SAC's learned $\rho$ does not track the true average reward or its policy converges to a lower average reward than the optimal policy, the claim that it solves the average-reward objective fails. A simpler check is to run ARO-SAC on the RAN slicing task with the $\rho$ update disabled and a fixed $\rho=0$; if performance keeps the 15% gain, the gain would be attributable to the algorithm change rather than to the average reward estimate.
Extended reading notes
Core claim
The paper's central claim is that the widely used discounted reward RL formulation is misaligned with wireless RRM objectives, which are undiscounted long-term average QoS, and that switching to average reward RL closes the gap. The discovery is an algorithm, ARO-SAC: take SAC's actor-critic updates, drop the discount factor, and instead maintain a trainable average reward estimate, updated by gradient descent on the temporal-difference residual. The TD target becomes the reward minus the estimated average reward plus the target value of the next state, so the critic learns a differential value function rather than a discounted one. In the RAN slicing testbed with fixed horizon, ARO-SAC achieves a 15% gain over the best discounted SAC and avoids the divergence that appears with a discount factor of one. The author's intended conclusion is that average reward RL should replace discounted reward RL in RRM because it matches the true network objective.
Load-bearing premise
The load-bearing premise is that the modified Bellman updates in Algorithm 1 define a valid and convergent average-reward SAC: the paper assumes the trainable average reward estimate $\rho$ converges and that the altered TD target remains a sound learning signal, but it provides no proof.
Editorial extensions
If this is right
- In the tested RAN slicing setup, a larger discount factor with fixed horizon increases cumulative reward, showing that discounted agents leave performance on the table.
- Extending the environment horizon at a fixed discount factor improves average reward per step, confirming that horizon truncation compounds the objective mismatch.
- Setting the discount factor to one is not a workable fix because training becomes unstable, motivating the average-reward reformulation.
- ARO-SAC with a properly tuned learning rate for the average reward estimate delivers a 15% gain over vanilla SAC with a discount factor of 0.99 in the simulator.
- The average reward RL framework adds one trainable parameter and one extra hyperparameter to SAC, so the gain comes with a modest tuning cost.
Reading between the lines
- Beyond the paper's claims: the same TD-target swap should transfer to other off-policy actor-critic algorithms, suggesting the 15% gain reflects objective alignment rather than a SAC-specific quirk.
- Because the mismatch is about the objective, the benefit should grow in tasks with long horizons and non-stationary traffic; a testable prediction is that ARO-SAC's margin over discounted SAC increases as the episode period grows beyond the tested value.
- The paper's update for the average reward estimate resembles a differential baseline, so convergence may depend on the ratio of learning rates between the estimator and the critics; the reported choice of a smaller learning rate for the estimator is a plausible practical rule.
- Under the average reward objective, reward shaping choices such as the delay-violation penalty weight should be re-tuned, so the reported 15% gain may shift with different QoS trade-offs.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper argues that the standard discounted-reward RL objective is misaligned with the long-term average QoS goals of radio resource management (RRM), and uses a RAN slicing task to illustrate this. It proposes ARO-SAC, an adaptation of Soft Actor-Critic to the average-reward setting, and reports a 15% performance gain over vanilla SAC with gamma=0.99. The paper also studies the effect of the discount factor and horizon on the discounted formulation, showing that larger gamma and longer horizons help but gamma=1 is unstable.
Significance. If the central claim were supported, the paper would address a real and under-appreciated mismatch between the RL objective and wireless network optimization goals. The use of an industry-grade simulator (NetworkGym/NS-3) and the systematic study of discount factor and horizon effects are useful and credit-worthy. However, the proposed ARO-SAC algorithm is not a valid average-reward SAC: it removes SAC's entropy regularization and uses an unjustified update for the average-reward estimate. The empirical headline result is therefore confounded by multiple algorithmic changes and lacks reported uncertainty. As presented, the paper does not support its main contribution.
major comments (4)
- [Section V-B, Eq. (8), Algorithm 1 line 19] The average-reward estimator is updated by minimizing eps_t = r - rho - min Q(s,a), whose fixed point is rho = r - Q(s,a), a state-action-dependent residual rather than the average reward. This omits the successor value that appears in the differential TD error of Eq. (6), delta_t = R_{t+1} - rho + V(S_{t+1}) - V(S_t). No convergence or consistency argument is provided; the paper itself defers theoretical guarantees to Section VI. This invalidates the claim that Algorithm 1 implements an average-reward RL algorithm.
- [Algorithm 1, lines 12 and 17] Algorithm 1 is not Soft Actor-Critic. The policy update in line 17 is the plain policy gradient sum log pi(a|s) Q(s,a) without SAC's entropy regularization term -alpha log pi(a|s), and the target in line 12 is y = r - rho + min Q_targ(s', a') rather than SAC's r + gamma(min Q - alpha log pi). ARO-SAC therefore differs from the vanilla SAC baseline in both the return criterion and the policy-update rule. Consequently, the 15% gain in Fig. 3 cannot be attributed to alignment with the average-reward objective; it may stem from removing entropy regularization or from the altered update altogether.
- [Fig. 3] The headline comparison lacks error bars or confidence intervals, even though Fig. 2 reports them. The text states the result is averaged over 5 independent runs and 5 user-number combinations, but no variance is reported. Given that the central claim is an empirical performance gain, the absence of uncertainty quantification makes the 15% figure difficult to assess.
- [Section III-B] The motivating example states that with gamma = 0.95, rewards beyond 50 time steps contribute only about 0.01 of their original value. This is quantitatively wrong: 0.95^50 is approximately 0.077, not 0.01. While illustrative, the error weakens the numerical motivation for the paper's central mismatch argument.
minor comments (5)
- [Abstract] There is a grammatical error: 'called the Average Reward Off policy Soft Actor Critic (ARO SAC) is an adaptation' should be 'called the Average Reward Off-policy Soft Actor-Critic (ARO-SAC), which is an adaptation.'
- [Section III-B] There are missing citation placeholders '[?]' in the paragraph on previous DRL studies of RAN slicing; these should be filled before publication.
- [Section V-A, Eq. (3)] Equation (3) uses r(pi) for the average reward, while later equations use rho. The notation should be unified.
- [Algorithm 1, line 19] The line 'Update average reward estimator rho: nabla_rho 1/|B| sum (eps_t)^2' is not a complete update rule; it should specify the loss and the learning rate or optimizer used.
- [Section V-C] The paper states that the learning rate for rho needs careful selection and was set to 1e-5, but it does not report how this value was chosen or how sensitive the result is to it, which is relevant given the new hyperparameter.
Circularity Check
No significant circularity; the 15% gain is an empirical comparison, though the SAC naming and convergence assumptions are correctness risks.
full rationale
ARO-SAC's central claim is an empirical comparison (Fig. 3), not a derivation from its own assumptions. The average-reward estimator rho is fitted online, but the reported gain is the measured policy performance, not the fitted rho, and no equation forces the outcome by construction. The alignment in Sec. V-A is definitional (setting r(t) to the QoS function makes the average-reward objective Eq. (2) equal the wireless objective Eq. (1)), but it is used as motivation rather than as a predicted result, so it is not load-bearing circularity. The algorithm design is explicitly adapted from the external ARO-DDPG work [3] and standard average-reward RL [1]; the self-citations to prior wireless RL work [13, 18, 21, 22] are background and do not support the average-reward extension. The more substantive concerns—that Algorithm 1 omits SAC's entropy regularization and that the rho update has no convergence proof—are validity/correctness issues, not circularity; the paper itself acknowledges the missing theory in Section VI ('Interesting future works include providing theoretical guarantees of ARO-SAC'). No fitted parameter is renamed as a prediction, no uniqueness theorem is imported from the authors, and no self-citation chain forces the method. Verdict: no significant circularity.
Assumptions & free parameters
free parameters (4)
- Reward penalty weight alpha =
4
- Average reward estimator learning rate =
1e-5
- Baseline discount factor gamma =
0.99
- Episode/reset horizon T =
200
assumptions (5)
- domain assumption The RAN slicing MDP and its netgymenv/NS-3 simulation faithfully represent real wireless network behavior.
- standard math The average reward Bellman equation for differential returns is applicable to this MDP.
- ad hoc to paper Removing SAC's entropy regularization still yields a valid average reward Soft Actor Critic algorithm.
- domain assumption The scalar reward R(t)=sum_i(Trx,i - 4 Dvio,i) captures QoS objectives for RAN slicing.
- domain assumption The softmax normalized action space over N-1 proportions is sufficient to represent optimal RBG allocation.
Cite this review
Pith. "Pith review of Average Reward Reinforcement Learning for Wireless Radio Resource Management." pith.science (2026). https://pith.science/paper/SSYCKOKQ
@misc{pith2026250106700,
author = {Pith},
title = {Pith review of: Average Reward Reinforcement Learning for Wireless Radio Resource Management},
year = {2026},
howpublished = {\url{https://pith.science/paper/SSYCKOKQ}},
note = {Machine review of arXiv:2501.06700}
}
read the original abstract
In this paper, we address a crucial but often overlooked issue in applying reinforcement learning (RL) to radio resource management (RRM) in wireless communications: the mismatch between the discounted reward RL formulation and the undiscounted goal of wireless network optimization. To the best of our knowledge, we are the first to systematically investigate this discrepancy, starting with a discussion of the problem formulation followed by simulations that quantify the extent of the gap. To bridge this gap, we introduce the use of average reward RL, a method that aligns more closely with the long-term objectives of RRM. We propose a new method called the Average Reward Off policy Soft Actor Critic (ARO SAC) is an adaptation of the well known Soft Actor Critic algorithm in the average reward framework. This new method achieves significant performance improvement our simulation results demonstrate a 15% gain in the system performance over the traditional discounted reward RL approach, underscoring the potential of average reward RL in enhancing the efficiency and effectiveness of wireless network optimization.
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Reviewed August 10, 2026 · model on record in the stance chip above.
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