[Paper Review] Prototyping Next-Generation O-RAN Research Testbeds with SDRs

Pratheek S. Upadhyaya, Aly Sabri Abdalla+3 more|arXiv (Cornell University)|May 26, 2022

Advanced MIMO Systems OptimizationEngineering23 citations

TL;DR

Describes building an end-to-end O-RAN research testbed using open-source software (srsRAN) and SDR hardware, integrating the near-RT RIC via E2, and showcasing xApps implementations.

ABSTRACT

Open RAN (O-RAN) defines an emerging cellular radio access network (RAN) architecture for future 6G wireless networks, emphasizing openness and intelligence which are considered the foundations of future 6G wireless networks. While the inherent complexity and flexibility of the RAN give rise to many new research problems, progress in developing solutions is hampered due to the lack of end-to-end, fully developed platforms that can help in pursuing use cases in realistic environments. This has motivated the formation of open-source frameworks available to the wireless community. However, the rapid evolution of dedicated platforms and solutions utilizing various software-based technologies often leaves questions regarding the interoperability and interactions between the components in the framework. This article shows how to build a software-defined radio testbed featuring an open-source 5G system that can interact with the near-real-time (near-RT) RAN intelligent controller (RIC) of the O-RAN architecture through standard interfaces. We focus on the O-RAN E2 interface interactions and outline the procedure to enable a RAN system with E2 capabilities. We demonstrate the working of two xApps on the testbed with detailed E2 message exchange procedures and their role in controlling next-generation RANs.

Motivation & Objective

• Motivate the need for end-to-end, open, programmable RAN testbeds to enable realistic 6G research.
• Describe a concrete, open-source O-RAN–compliant testbed built on SDRs and srsRAN.
• Demonstrate E2 interface integration and near-real-time RIC interactions with xApps.
• Provide deployment guidelines and open-source resources to reproduce the testbed.

Proposed method

• Assemble a software-defined radio testbed using srsRAN for LTE/5G NSA and integrate with the near-RT RIC from OSC.
• Implement the E2 interface using E2AP ASN.1 encoding and an E2 agent to connect eNB/gNB with the near-RT RIC over SCTP.
• Deploy the near-RT RIC as Kubernetes-backed microservices with xApps for RRM control and data collection.
• Demonstrate xApps by deploying KPIMON (KPI monitoring) and a RAN Slicing xApp to control resources across slices.
• Use standard O-RAN interfaces (E2, O1/A1 mediators) and open-source components to enable end-to-end closed-loop control.

Experimental results

Research questions

• RQ1 How can an end-to-end O-RAN research testbed be constructed using open-source software and SDR hardware?
• RQ2 What are the practical procedures to integrate the E2 interface with a software RAN like srsRAN and connect to the near-RT RIC?
• RQ3 How do xApps interact with RAN functions via E2 to perform monitoring and control tasks in a real-like testbed?
• RQ4 What feasibility and performance insights can be gained from implementing RAN slicing and KPI reporting in such a testbed?

Key findings

• A working O-RAN–compliant testbed is demonstrated, linking srsRAN with the near-RT RIC through the E2 interface.
• E2 setup, subscription, and INDICATION workflows are shown using ASN.1 encoding and SCTP-based signaling.
• KPIMON xApp demonstrates KPI collection and reporting flow from RAN to the near-RT RIC via E2 messages.
• RAN Slicing xApp illustrates asynchronous control of per-slice resource allocation and corresponding UE throughput changes.
• The architecture emphasizes modularity, virtualization, and open-source components to enable reproducible research in lab and production-like settings.