DU-high

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srsRAN Project DU-high implementation

The DU-high, or Distributed Unit - High, is responsible for the handling of both uplink and downlink traffic. Specifically the MAC and RLC processing of these signals. The DU-high, has three main components and three main interfaces. The DU-high communicates directly with the CU-CP and CU-UP via the F1-c and F1-u interfaces, the DU-low via the FAPI interface, and can also be connected to the near-RT RIC via the E2 interface.

Return to top level architecture diagram.

Components:

  • DU Manager: The DU Manager is responsible for managing the DU, specifically the connected UEs and RAN Resources.

  • RLC: The Radio Link Control (RLC) layer sits between the MAC in the DU-high and the F1AP/PDCP in the CU, and provides the transport services for SRBs and PRBs between these layers. It operates in three modes: transparent, unacknowledged and acknowledged.

  • MAC: The Medium Access Control (MAC) is responsible for the encoding and decoding of MAC PDUs, scheduling uplink and downlink grants and other control services.

Interfaces:

  • E2: Interfaces with the nRT RIC.

  • F1: Interfaces with the CU control and user plane.

  • FAPI: Interface between the DU-high and DU-low.

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