Institute for Telecommunication Sciences / About ITS / 2025 / Lessons Learned from ITS Open RAN System Integration

Lessons Learned from ITS Open RAN System Integration: A Resource for Engineers, System Integrators, and Stakeholders Aiming to Deploy Open RAN Systems

The key to successful Open RAN deployments — the ability of subsystems from different vendors to seamlessly interoperate — is also the greatest challenge.

Commercial Tier 1 radio access networks (RANs) deployed today generally consist of closed, proprietary systems using products from a single manufacturer. Open RAN presents a different approach to this by disaggregating hardware and software, enabling multi-vendor interoperability. This approach means that system integration is crucial for Open RAN deployments, which require precise compatibility, timing synchronization, and interoperability management.

ITS performs research, development, test, and evaluation (RDT&E) of Open RAN components, systems, and deployments in the Communications Research and Innovation Network (CRAIN) Laboratory. This laboratory environment allows ITS engineers to deploy multiple Open RAN systems and conduct extensive testing to analyze interface compatibility, strict timing requirements, and hardware dependencies. In 2025, ITS completed integration of three Open RAN systems procured on the open market, two from Vendor 1 and one from Vendor 2, into the CRAIN lab, with the goal of validating the Open RAN systems in a high-performance, carrier-grade environment.

 

annotated image of equipment in a screen room
During inter- and intra-frequency handover tests in the laboratory, O-RU 1 and O-RU 2 were oriented to face in opposite directions in the RF screen room to reduce interference of one into the other.

 

The ITS integration effort highlighted some actionable insights regarding potential interface bit rate incompatibilities, signal timing, and synchronization dependencies with manual and often error-prone network configuration requirements in a multi-vendor RAN environment.

All the equipment in the CRAIN laboratory met the specifications issued by the 3rd Generation Partnership Project (3GPP) (which develops international technical specifications for cellular telecommunications technologies) and the O-RAN ALLIANCE (an industry-led effort to develop technical specifications for Open RAN architecture). Both 3GPP and O-RAN specifications, however, allow for options in the way individual vendors configure their equipment to conform to the open network interfaces defined in the standards.

The ITS team, which served as both the system integrator and principal tester of the Open RAN vendor equipment for this effort, held numerous debugging sessions with the two Open RAN manufacturers, 5G core engineering and test equipment manufacturing team, and the internal ITS networking group. Some key findings were:

  • Interworking challenges persist, even when interfaces follow 3GPP and O-RAN ALLIANCE standards. During testing, issues such as misconfigured timers, differences in message handling, bit rate incompatibilities, and standards-version mismatches created non-interoperability events that required detailed debugging.
  • Integration and upgrade processes are resource intensive. The deployment and software update cycles for first-generation Open RAN equipment were observed to take longer than comparable processes for traditional Tier 1 RAN systems.
  • It is efficient to verify early on that parameters across subsystems are compatible. Flexibility in system configuration is critical. Integration was more efficient when parameters were software-configurable rather than hard-coded. This underscored the importance of early verification of configuration options.

The ITS team continues to evaluate and test the performance and interoperability of these and other Open RAN systems in the CRAIN Laboratory. The goal of this testing is to compare the performance of RANs from a traditional Tier 1 RAN vendor and two Open RAN vendors, based on a subset of tests from the O-RAN ALLIANCE Test and Integration Focus Group (TIFG) end-to-end open RAN tests. The team is planning to release a report that provides a comparison of test results for an initial group of tests performed on a traditional RAN and a first-generation Open RAN.

Future research by the CRAIN Laboratory team will examine differences between FPGA/ASIC–based Tier 1 RAN systems and server-based Open RAN systems with real time–processing capabilities. ITS also plans to collaborate with international Open RAN labs on shared test cases, contributions to O RAN ALLIANCE Working Groups, standardized Telecom Infra Project (TIP) test cases, and the development of consistent RIC based energy saving applications. ITS plans to share its Open RAN testing and collaboration lessons learned/best practices with other labs to help drive the community towards repeatable and reproducible testing.