What is Section Type in Open RAN Fronthaul?

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In Open RAN network deployments, interface between DU and RU is known as Fronthaul. As shown in below picture, the fronthaul carrier, the fronthaul carries Control and User Plane (C/U) data, Sync and Management using eCPRI standard defined format.

  • C-Plane (Control Plane): Control plane messages define the scheduling, coordination required for data transfer,  beam-forming etc.
  • U-Plane (User Plane): User plane messages for efficient data transfer within the strict time limits of 5G numerologies.
  • S-Plane (Synchronization Plane) : Synchronization plane is responsible for the timing and sync aspects between the O-DU and O-RU.
  • M-plane (Management Plane) : Management plane messages are used to manage the radio unit.

In the C-Plane, messages are encapsulated using a two-layered header approach.

  • First layer header is an eCPRI header to indicate the message type
  • Second layer is an Application Common header including necessary fields for control and synchronization

Section Definition

A “section” defines the characteristics of U-plane data to be transferred or received from a beam with one pattern id within the application common header. Section is 8 bit and can have possible 2^8=256 types called section type, but at present only 6 section types are in use.

  • Control Plane has following 6 section types in use :
    1. Section Type 0 – used for indicating idle or guard periods from O-DU and O-RU
    2. Section Type 1 – used for most DL and UL radio channels
    3. Section Type 3 – used for PRACH and mixed-numerology channels
    4. Section Type 5 – used for UE scheduling information
    5. Section Type 6 – used for sending channel information for a specific UE ID
    6. Section Type 7 – used to support LAA
  • User-plane has following 4 section types in use:
    1. Section Type 1
    2. Section Type 3
    3. Section Type 5
    4. Section Type 6

Sections Structure

The structure of a “section” is consist of  transport header (shown in yellow color), radio application head (pink color) and other others are repeated sections.

  • Section Types#0 Structure

  • Section Types#1 Structure

  • Section Types#3 Structure

 

  • Section Types#5 Structure

  • Section Types#6 Structure

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