xRAN Fronthaul Control, User and Synchronization Plan Specification Version 2.0 and xRAN Fronthaul Management Plane Specification Version 1.0

The xRAN Fronthaul Specification document specifies the control plane, user plane and synchronization plane protocols used over the fronthaul interface linking the lls-CU (lower-layer split Central Unit) with the RU (Radio Unit) with a Lower Layer Functional Split-7-2x based architecture. The scope of this document includes both LTE and NR (5G).

This 2nd major version of CUS-plane specification incorporates several enhancements over the first version including:

  • Support for 2 radio categories (A and B) to enable both simple and more complex functionality leveraging largely the same interface specification
  • Support for critical items such as synchronization and timing to enable commercialization and interoperability in deployments
  • Support for additional LTE system features like LAA, NB-IOT, including improved efficiency in parsing of U-plane packets

The 1st version of M-plane specification is a significant milestone for the industry. It provides an open multi-vendor M-plane model for radios based on standardized modern protocols like NETCONF/YANG and includes below key capabilities:

  • Support for features and capabilities in v1.0 of CUS specification and many enhancements in v2.0 of CUS specification
  • Support for hierarchical deployments, including traditional and hybrid (multiple NETCONF clients or EMS can directly communicate with radio) approaches



xRAN Overview White Paper

The xRAN Forum was formed to develop, standardize and promote an open alternative to the traditionally closed, hardware-based RAN architecture. xRAN fundamentally advances RAN architecture in three areas – decouples the RAN control plane from the user plane, builds a modular eNB software stack that operates on common-off-the-shelf (COTS) hardware and publishes open north- and south-bound interfaces to the industry.


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