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Draft: Implementation of 2-Step RA

Nuno Domingues requested to merge RA_2-Step into develop

Implementation of 2-Step RA that includes:

  • Add configuration file with support for RA 2-Step
  • Add RA 2-Step configuration parameters to SIB1
  • Compute RA 2-Step MsgB_RNTI as specified in 3GPP TS 38.321 Section 5.1.3a
  • Baseline implementation of RA 2-Step MsgA procedures at gNB and at OAI UE
  • Implementation of RA 2-Step MsgB procedures at gNB and at OAI UE
  • Encode and decode SuccessRAR MAC CE.

Future work:

  • Implementation of a timer and procedures for msgB-ResponseWindow
  • Implementation of FallbackRAR and corresponding procedures (Switch between 2-Step RA and 4-Step RA)
  • Test 2-Step RA interoperability with COTS UE.

This is part of the work developed by Allbesmart within the project Imagine Beyond 5G (

Instructions for running this MR:


cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/ --rfsim --sa


cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-uesoftmodem -r 106 --numerology 1 --band 78 -C 3619200000 --rfsim --sa --uicc0.imsi 001010000000001
Edited by Nuno Domingues

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