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arxiv: 2604.17938 · v1 · submitted 2026-04-20 · 📡 eess.SP

A Novel CSI-RS Reporting Scheme for RIS Optimization in O-RAN-based NextG Networks

Ali Fuat Sahin , Sefa Kayraklik , Ali Gorcin , Ibrahim Hokelek , Ertugrul Basar , Halim Yanikomeroglu This is my paper

Pith reviewed 2026-05-10 04:42 UTC · model grok-4.3

classification 📡 eess.SP
keywords Reconfigurable Intelligent SurfaceO-RANCSI-RSComplex Channel InformationRIS OptimizationChannel Estimation
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The pith

A CSI-RS reporting scheme supplies complex channel data to enable RIS optimization inside O-RAN networks.

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

The paper develops a CSI reference signal scheme that extracts downlink complex channel information so reconfigurable intelligent surfaces can be adjusted in real time from the base station in open radio access networks. It adapts standard estimation methods for O-RAN use and tests the full setup on a physical testbed with open-source O-RAN software and an RIS prototype at n78 frequencies. A sympathetic reader would care because successful integration would let network operators shape wireless paths using flexible, vendor-independent systems rather than closed proprietary equipment.

Core claim

The CSI-RS-based reporting scheme for downlink complex channel information establishes extraction and reporting procedures that integrate existing RIS optimization algorithms into the O-RAN architecture, with real-world testbed results showing improved received signal power for both near and far users.

What carries the argument

The CSI-RS reporting scheme for extracting downlink complex channel information (CCI), which carries the tailored Hadamard and orthogonal matching pursuit algorithms into the O-RAN control loop.

If this is right

  • Real-time RIS adjustments become feasible inside open O-RAN systems.
  • Received signal strength rises for users both close to and distant from the base station.
  • Channel estimation methods already used in literature can be reused inside the O-RAN framework.
  • The approach demonstrates working operation on hardware at n78 frequencies.

Where Pith is reading between the lines

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

  • Network operators might reduce dependence on closed vendor solutions for dynamic signal control.
  • The same reporting structure could be checked on other frequency bands to test broader use.
  • Standardized interfaces for CCI reporting might speed RIS adoption across different O-RAN deployments.

Load-bearing premise

That the adapted channel estimation algorithms fit cleanly into O-RAN without large overhead or compatibility barriers and that results from the single-band testbed extend to other frequencies and deployments.

What would settle it

A run of the O-RAN-RIS testbed that yields no measurable rise in received signal power for near or far users or that encounters integration failures would show the scheme does not deliver the claimed practical gains.

Figures

Figures reproduced from arXiv: 2604.17938 by Ali Fuat Sahin, Ali Gorcin, Ertugrul Basar, Halim Yanikomeroglu, Ibrahim Hokelek, Sefa Kayraklik.

Figure 1
Figure 1. Figure 1: System model of an RIS-assisted cellular network including the CSI-RS reporting scheme for downlink CCI. [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: CSI-RS bitmaps. station, a near-real-time RAN intelligent controller (near-RT RIC) is embedded to develop custom applications for enhanc￾ing network capabilities. Through near-RT RIC, two control applications are operated [11]: the first one continuously col￾lects channel-related metrics for each UE (channel monitoring xApp, CM xApp) while the second one is responsible for utilizing the channel-related met… view at source ↗
Figure 3
Figure 3. Figure 3: 5G NR downlink CSI-RS grids. where k ′ , l ′ are the intra-pattern offsets and kj , lj are the base frequency and time offsets for the CDM group j. Additionally, mRB is the starting subcarrier index. Hence, m and n can be given as the indices of the subcarrier and OFDM symbol, respectively. Moreover, let us denote the known CSI-RS sym￾bol on the CSI-RS port p as xp[m, n]. Similarly, the received RE on the … view at source ↗
Figure 4
Figure 4. Figure 4: b plots the empirical PDF of the UE-side channel￾amplitude estimates collected over time. The dominant mass near |Hk| ≈ 0 corresponds to REs that do not carry user data (guard subcarriers, unscheduled REs, and control RBs), whereas the smaller lobe around ∼ 0.06 (after normalization) reflects active data-bearing REs. The simulation reproduces both behaviors, supporting the validity of the CCI extraction. (… view at source ↗
Figure 5
Figure 5. Figure 5: RIS optimization measurements utilizing CCI through the CSI-RS-based reporting. [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
read the original abstract

Reconfigurable intelligent surface (RIS) technology is a promising enabler for next-generation (NextG) wireless systems, capable of dynamically shaping the propagation environment. Integrating RIS within the open radio access network (O-RAN) architecture enables flexible and intelligent control of wireless links. However, practical RIS-assisted operation requires efficient acquisition and reporting of channel state information (CSI) to support real-time control from the base station side. This paper proposes a CSI reference signal (CSI-RS)-based reporting scheme for downlink complex channel information (CCI) to facilitate RIS optimization in an O-RAN-compliant environment. The proposed framework establishing CCI extraction and CSI-RS reporting procedures is experimentally validated on a real-world testbed integrating an open-source O-RAN system with an RIS prototype operating in the n78 frequency band. Existing channel estimation-based RIS optimization algorithms, including Hadamard and orthogonal matching pursuit (OMP), are tailored for integration into the O-RAN architecture. Experimental results demonstrate notable improvements in received signal power for both near and far users, highlighting the effectiveness and practical viability of the proposed scheme.

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

0 major / 3 minor

Summary. The paper proposes a CSI-RS-based reporting scheme for extracting downlink complex channel information (CCI) to enable RIS optimization within O-RAN-compliant NextG networks. It adapts existing Hadamard and orthogonal matching pursuit (OMP) algorithms for this setting and experimentally validates the overall framework on a real testbed that combines an open-source O-RAN stack with an RIS prototype operating in the n78 band, reporting received-signal-power gains for both near and far users.

Significance. If the experimental results hold, the work is significant because it supplies concrete, hardware-in-the-loop evidence that RIS control can be realized inside an O-RAN architecture using standard CSI-RS procedures. The use of an open-source O-RAN implementation together with a physical RIS prototype at a 5G frequency band constitutes a reproducible demonstration of practical viability, which is still rare in the RIS literature and directly addresses the gap between theoretical optimization algorithms and deployable systems.

minor comments (3)
  1. [Abstract] Abstract: the phrase 'notable improvements in received signal power' is not accompanied by any numerical values, confidence intervals, or measurement conditions; adding at least the observed dB gains and basic test conditions would make the central claim immediately assessable.
  2. [Experimental Validation] Experimental section: the description of the testbed procedures, CCI extraction steps, and the exact modifications made to the Hadamard and OMP algorithms would benefit from a concise pseudocode listing or parameter table to facilitate replication by other O-RAN/RIS groups.
  3. [Experimental Setup] The paper should explicitly state the number of independent trials, environmental conditions, and any calibration steps performed on the RIS prototype; these details are standard for experimental wireless papers and would strengthen the reproducibility claim.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive assessment of our manuscript, the accurate summary of its contributions, and the recommendation for minor revision. The significance statement correctly highlights the value of our hardware-in-the-loop O-RAN + RIS demonstration. No specific major comments were provided in the report, so we have prepared the revised manuscript with minor editorial and clarification improvements while preserving all technical content.

Circularity Check

0 steps flagged

No significant circularity; experimental validation is self-contained

full rationale

The paper proposes a CSI-RS reporting scheme for RIS optimization in O-RAN and validates it via real-world testbed experiments at n78 band, showing received power gains for near/far users. No mathematical derivation chain exists that reduces predictions or results to inputs by construction, self-definition, or fitted parameters renamed as outputs. Algorithm tailoring (Hadamard, OMP) is presented for O-RAN compatibility but serves as implementation detail, not a load-bearing premise justified only by self-citation. The central claim rests on external empirical benchmarks (testbed measurements), making the work self-contained with no internal reductions. This matches the provided reader's assessment of minimal circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review yields no identifiable free parameters, axioms, or invented entities; the contribution is an engineering scheme and experimental demonstration rather than a theoretical derivation.

pith-pipeline@v0.9.0 · 5514 in / 981 out tokens · 32485 ms · 2026-05-10T04:42:16.394043+00:00 · methodology

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Reference graph

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