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Reimagining Testing for Open RAN


by Steve Douglas, Head of Market Strategy, Spirent Communications

In the last few years, many Communication Service Providers (CSP) have been trialing Open Radio Access Network (Open RAN) technologies. The potential benefits of open, standardized multi-vendor architectures in supply chain flexibility, increased competition, innovative new use cases, and more, have been too great to ignore. Now though, we’ve reached a milestone in the evolution of these architectures. CSPs are no longer just talking about Open RAN potential; they’re tentatively deploying it in production networks.

This year, multiple CSPs—DISH, Telefonica, 1&1, and others—are rolling out production Open RAN architectures. Given the novelty of Open RAN specifications, technologies, and even vendors, these early efforts pose unique challenges. Yet we can already draw important lessons from these early rollouts about how best to test Open RAN. The most important takeaway: Open RAN testing requirements are radically different from yesterday’s networks.

Figure 1: Open RAN adds layers of testing complexity

Reimagining RAN Testing

Validating any new network technology is a significant undertaking. Operators must test everything from user equipment to disaggregated network functions to radios themselves. Open RAN only adds to the challenge.

As CSPs shift from closed, proprietary solutions to open standards, they must first test for compliance with Open RAN specifications. Even here, Open RAN brings unique challenges, encompassing contributions from 3GPP, the O-RAN Alliance, the European Telecommunications Standards Institute (ETSI), and several other standards bodies. Early standards also remain open to interpretation, with different vendors implementing them differently, making simple plug-and-play integration challenging.

Given the novelty of Open RAN architectures and technologies, operators must test and validate the full range of basic network functions, including:

  • Feature conformance
  • Multi-vendor interoperability
  • Mobility and handovers
  • Capacity and scalability
  • Synchronization and timing
  • Performance and robustness

CSPs must test for these attributes in individual network functions, in combinations of adjacent functions, and anywhere in the network where different vendor components interact. Finally, they need to test the performance and scalability of the end-to-end network for the services it will support, including voice, data, video, and emergency services.

Adding New Wrinkles

These requirements themselves may not seem particularly novel. But with Open RAN, CSPs must now test them across a distributed architecture encompassing more vendors and many brand new architectural elements. These attributes, as well as the demanding requirements of the next-generation services that these RANs will support, require CSPs to heighten testing focus on:

  • Latency: One of 5G’s most important innovations is the ability to support much lower latency. But when next-generation services demand consistent latencies measured in microseconds, every part of a multivendor radio network must be exhaustively tested and tuned to ensure that nothing impairs performance.
  • Software-driven architectures: Open RAN, along with 5G Standalone core, pushes CSPs to adopt software-driven architectures. Among other benefits, this allows them to receive continuous software updates from more vendors, more often accelerating innovation. But it also makes testing more complex. Different vendors may now release updates every few weeks, each on their own cadence. For every update, CSPs must test the network to re-validate interoperability, performance, and security.

These are just high-level requirements. For each node, CSPs must perform conformance and interoperability tests, functional and application tests, and performance tests—each focusing on the unique aspects of that node. A full set of Open RAN test cases should include the following:

  • Open Radio Unit (RU) wraparound testing
  • Open Distributed Unit (DU) testing
  • Open Centralized Unit (CU) testing
  • Open RAN Intelligent Controller (RIC) testing
  • End-to-end (E2E) testing
  • Security testing
  • Fronthaul transport testing
  • Synchronization testing
  • Cloud-native DU and CU resiliency validation
  • Field testing

It all adds up to a huge number of Open RAN testing combinations that CSPs need to address—and a validation process 10 to 15 times more complex than traditional RANs. And, unlike yesterday’s architectures, there is no single vendor to turn to when there’s an issue. In this complex, software-driven world, manual testing is a nonstarter. As the first movers have discovered, automated, repeatable, continuous testing is a core requirement for successful Open RAN rollouts.

Automating RAN Testing

Open RAN introduces not just new technologies but also entirely new operating models, and no area demands fresh approaches more than testing and validation. CSPs can no longer view radio testing as a discrete process that unfolds over months in the lab, with one or two implementations per year in fixed maintenance windows. To support a constantly changing multi-vendor architecture, they need continuous, automated testing, with the ability to automatically revalidate interoperability and performance after every vendor software update and every network change. Indeed, it’s hard to imagine a successful Open RAN rollout without vendor-neutral, automated test environments where vendors can safely collaborate to solve problems and get solutions to market.

The CSPs leading the way in Open RAN are using continuous testing frameworks that extend across both lab and live environments. They’re automating testing for performance and latency, standards compliance, scalability, synchronization and timing, and other factors. They’re using real-world traffic emulation to simulate both typical conditions and unexpected events. And they’re drawing on repeatable, shareable, reproducible test scripts to make complex Open RAN testing more efficient and economical.

The CSPs aiming to be first to market with Open RAN expect significant benefits through new use cases, innovations, and efficiencies. But they’re also blazing a trail for the rest of the market. They’re proving that with intelligent, automated approaches to multi-vendor testing and validation, the real-world advantages of Open RAN are now within reach.