Practical RIS Gain without the Pain: Randomization and Opportunistic Scheduling in 5G NR

TL;DR

This work demonstrates that practical gains from a reconfigurable intelligent surface (RIS) can be realized in a real-time 5G NR system without explicit RIS phase optimization. By randomly switching RIS states while leveraging the inherent proportional-fair scheduling of 5G NR, the system exploits multi-user diversity to approach the performance of optimally configured RIS while avoiding CSI overhead and signaling burden. The authors provide experimental validation in an OpenAirInterface-based testbed, showing RSRP gains of about 7–8 dB and throughput improvements of roughly 20–25% compared to no RIS, and they show that throughput under randomized RIS with PF scheduling can approach the optimized RIS gains as the EWMA parameter is tuned. The findings indicate a practical, low-complexity path to RIS deployment in real networks, scalable to larger multi-user scenarios with minimal overhead.

Abstract

We experimentally demonstrate the performance gains achieved by an in-house built reconfigurable intelligent surface (RIS) integrated with a real-time 5G new radio (NR) system implemented using the OpenAirInterface (OAI) framework. We first quantify the gain in throughput achievable by integrating an RIS with a 5G system. Next, we show that randomly setting the RIS phase configuration and leveraging the inherent proportional fair (PF) scheduling mechanism of 5G NR can yield near-optimal throughput, provided the throughput averaging window of the PF scheduler is chosen judiciously. This occurs because, in each time slot, the PF scheduler naturally prioritizes data transmission to the user equipment (UE) that experiences the best channel conditions, namely, the UE to which the randomly configured RIS is aligned. Subsequently, we experimentally evaluate key performance metrics, including the reference signal received power (RSRP), block error rate (BLER), modulation and coding scheme (MCS) index, and throughput, under random RIS configurations. These results confirm that even a randomly configured RIS with negligible overhead can deliver performance comparable to optimized RIS designs, in real-world 5G NR wireless communication systems.

Figures (5)

• Figure 1: Schematic diagram for the unit-cell of $1$-bit digitally coded RIS: Perspective 3D view and Equivalent circuit of PIN diode Malleboina_EuCAP_2025.
• Figure 2: Experimental setup used in this work. The system uses an OAI-based $5$G NR implementation with $1$ gNB and $2$ UEs connected to it via an RIS.
• Figure 3: Variation of performance metrics of a randomized RIS-aided $5$G NR system using a proportional-fair scheduler with $\alpha=0.00005$.
• Figure 4: System throughput vs. $1/\alpha$.
• Figure 5: Fraction of time slots allotted by PF scheduler with $\alpha=0.00005$.

Theorems & Definitions (2)

• Remark 1
• Remark 2: Choice of $\alpha$ and $T_s$