One of the major challenges to the adoption of open RAN in 5G networks in dense, urban environments is its sub-optimal support for massive MIMO radios. While there are several reasons behind this performance deficit, a key reason is that the O-RAN Alliance 7.2x open fronthaul specification was not originally designed to accommodate massive MIMO radio systems. Recently, the O-RAN Alliance announced a new fronthaul interface specification designed specifically for use with massive MIMO radio systems in dense, high-traffic environments.

This Technology Report provides an objective analysis of the O-RAN Alliance’s Next Generation Lower-Layer Split (LLS) and discusses the implications of the new interface on the adoption of open RAN massive MIMO radios.

Key Takeaway 1: Impact of Incumbents

With the availability of the new NG-LLS fronthaul split, it “appears” that the open RAN community has united around a single specification which will enable open RAN to be adopted in high-traffic urban regions. This should be welcome news as it means that operators will be able to use open RAN technology across all parts of their networks, from rural deployments to dense, high traffic urban environments.  However, the NG-LLS standard has brought major incumbents such as Ericsson and Nokia into the open RAN limelight. While this brings scale and credibility to open RAN in the high-end 5G market, it also raises questions about open RAN’s goal of diversifying the radio supply chain and lowering barriers to smaller vendors.

Key Takeaway 2: Massive MIMO Use Cases Suitable for Split 7.2b

Although Split 7.2b has limitations when deployed in dense, high-traffic urban networks, Counterpoint Research believes that it will continue to be a good choice for other mMIMO use cases. For example, in uses cases with moderate traffic loads, where cell sizes are larger and where end-user mobility is low such as in Fixed Wireless Access applications. Radios based on Split 7.2b will also benefit from reduced complexity and lower costs compared to NG-LLS based radios. In future, the application of advanced AI/ML algorithms in the DU may narrow the performance differential between Split 7.2b and NG-LLS for some use cases.

The full version of this Technology Report, including a complete set of Key Takeaways is published in the following report, available to clients of Counterpoint Research’s 5G Network Infrastructure Service (5GNI).

Table of Contents:

• Snapshot
• Key Takeaways
• Introduction
• Overview of 5G Fronthaul Splits
• The Split 7.2x vs Split 7.3 (or 7.2c) Debate
• Next-Generation Lower-Layer Split
      • Overview of ULPI Class B and Class A
      • WBDF vs ULPI
            • Beamforming
            • Equalisation
      • ULPI Performance Gains vs Increased RU Complexity
      • Benefits of Equaliser in DU
      • Leveraging AI for Channel Estimation
      • Massive MIMO Uses Cases Suitable for Split 7.2b
      • Non-massive MIMO Use Cases
• Implications for 5G RAN Ecosystem
• Analyst Viewpoint

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