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3GPP RAN and Core Platforms

Implementation Detail

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Category: 3GPP Implementations

What This Project Implements​

This project provides the 5G network infrastructure that other 5G-MAG reference tools run against. 5G-MAG maintains forks of established open-source Radio Access Network (RAN) and Core software, adds the components needed for its media and broadcast work, and documents how to stand up a working network in a lab or testbed.

In 5G terminology the RAN can be split into a Central Unit (CU) and a Distributed Unit (DU); the network core is the 5G Core (5GC); and Software Defined Radio (SDR) hardware is used to transmit and receive the radio signal. The forks below add support for the different delivery technologies 5G-MAG works on.

A note on the delivery technologies referenced here:

  • MBS (Multicast-Broadcast Services), also written 5MBS, is the 3GPP feature for delivering the same content to many devices over the 5G Core and NR radio.
  • 5G Broadcast (LTE-based) delivers free-to-air TV and radio over LTE/eMBMS radio, without a 5G core or return channel. It reuses Further evolved Multimedia Broadcast Multicast Service (FeMBMS).

These are distinct technologies; the forks below follow this split.

Upstream software we build on​

Some Reference Tools Projects make use of software developed by other Open-Source Software initiatives.

In particular:

  • srsRAN Project, in its two variants:

    • srsran/srsRAN_Project: Open source O-RAN 5G CU/DU solution from Software Radio Systems (SRS), used primarily as the NG-RAN to build Reference Tools demonstrators and PoCs and as the basis for the development of NG-RAN related components for MBS
    • srsran/srsRAN_4G: Open source SDR 4G software suite from Software Radio Systems (SRS), used primarily as the basis for the LTE-based 5G Broadcast components, emergency alerts over 5G Broadcast and the development of UE functionalities for MBS

  • Open5GS Project, used primarily as the 5GC to build Reference Tools demonstrators and PoCs and as the basis for the development of 5GC related components for MBS

What this project provides​

This project does not deliver media itself; it provides a working radio access network and core so that MBS and 5G Broadcast components have something to attach to in a lab or testbed. The pieces map to 5G terminology as follows:

  • NG-RAN (gNB), split into CU and DU: built from rt-srsRAN_Project, 5G-MAG's fork of the srsRAN Project (an O-RAN-native 5G CU/DU with a full L1/L2/L3 implementation from Software Radio Systems). This is the NR side used for MBS demonstrators and for developing NG-RAN components for MBS.
  • 5G Core (5GC): built from 5G-MAG's fork of Open5GS. For MBS this includes the multicast/broadcast core functions; published 5G-MAG material describes using Open5GS for functions including the AMF, MB-SMF and MB-UPF.
  • LTE-based radio and UE, for 5G Broadcast: built from srsRAN_4G (the SDR 4G suite from SRS). This is the basis for the LTE-based 5G Terrestrial Broadcast transmitter and for developing UE-side functionality.
  • SDR hardware: Software Defined Radio front-ends transmit and receive the radio signal that the software above generates and processes.

The two delivery technologies, and why the forks split​

The forks are organised around two distinct delivery technologies.

MBS (5MBS)5G Broadcast (LTE-based)
Radio5G NRLTE / eMBMS (reuses FeMBMS)
Core5G Core (multicast/broadcast functions)None; free-to-air, no return channel
RAN software basisrt-srsRAN_Project (NR CU/DU)srsRAN_4G (eNodeB with MBMS)
Typical useSame content to many devices over 5GC and NRFree-to-air TV and radio over broadcast, receive-only

Further evolved Multimedia Broadcast Multicast Service (FeMBMS) is the LTE broadcast feature reused by 5G Broadcast. Published 5G-MAG material notes that the LTE-based 5G Broadcast transmitter builds on the MBMS implementation in the srsRAN_4G eNodeB, extended towards the 3GPP Release 17 LTE-based 5G Terrestrial Broadcast feature set (for example channel estimation and reference signals for the 1.25 kHz and 7.5 kHz subcarrier spacings used by dedicated broadcast). The dedicated 5G Broadcast transmitter and modem live in separate repositories (for example rt-mbms-tx and rt-mbms-modem), which depend on this project for the underlying radio software.

How this relates to the media reference tools​

The MBS and 5G Broadcast media stacks depend on a working network to run against. This project supplies that network so the media components do not each have to stand up a RAN and core. Because the RAN and core are forks of upstream open-source projects (srsRAN, Open5GS), 5G-MAG tracks the upstream projects and maintains the additions needed for its broadcast and multicast work.

Getting Started​

  1. Decide which technology you are building for: MBS (5G NR plus 5GC) or LTE-based 5G Broadcast. This determines which fork you need.
  2. For MBS, build the NG-RAN from 5G-MAG/rt-srsRAN_Project and the core from 5G-MAG/open5gs, using their 5mbs branch.
  3. For 5G Broadcast, use the LTE-based transmitter path built on srsRAN_4G; see the dedicated transmitter and modem repositories.
  4. Follow the Tutorials for the network and SDR setup guides, including SDR front-end configuration.

Forks at a glance​

PWS (Public Warning System) is the cell-broadcast mechanism used for emergency alerts.

RepositoryBranchUse case
open5gsmainRegular 5G network (baseline core)
open5gs5mbs5MBS implementations
rt-srsRAN_ProjectmainRegular 5G network (baseline NG-RAN)
rt-srsRAN_Project5mbs5MBS implementations
srsRAN_4GmainLTE-based 5G Broadcast / MBMS, and emergency alerts (PWS)
srsRAN_4G5mbs5MBS implementations
srsRAN (discontinued version prior to srsRAN_4G)mainLTE-based 5G Broadcast / MBMS
note

Refer to the rt-srsRAN_Project and open5gs repositories to contribute to this project. See How to Contribute for the process.