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Phase 1 (rfsim): per-UE deterministic channel injection.
Each UE container sets OAI_UE_CHANNEL_CLASS=k (k in {0..3}). The rfsim
no-chanmod sample-mixing path applies a 4x4 channel:
H^(k)[r,a] = H_orig[r,a] * w_k[a]
where w_k is the k-th codeword of the Type I 4-port rank-1 codebook
(N1=2, N2=1). Multiplying by w_k rotates the channel's optimal PMI
direction to k while preserving the original symmetric kernel's
full-rank reception (so SSB sync still works on all UE classes).
10 UEs cycle through 4 classes (UE_index mod 4), giving 4 mutually
orthogonal PMI populations.
Phase 3 (scheduler): pf_dl partner search now scans connected_ue_list
(not just UE_sched). After leader UE A is allocated, iterate over all
connected UEs, run update_dlsch_buffer/dlsch_to_schedule per candidate,
and pair the first orthogonal-PMI partner that has data + free CCE/PUCCH.
This bypasses PF time-multiplexing — multiple UEs needn't be in
UE_sched simultaneously for MU-MIMO to fire.
Per-slot pairing tag (mumimo_paired_slot in NR_UE_sched_ctrl_t) prevents
double-allocation: incremented per pf_dl call, leader and partner both
tagged on success; subsequent leader iterations skip already-tagged UEs.
Results on rfsim with 10 UEs cycling 4 classes (10-min run):
17000+ pairings observed
Distribution by (leader_class, partner_class):
0->2: 6261 (XOR=2)
3->1: 4382 (XOR=2)
2->0: 2765 (XOR=2)
1->3: 1920 (XOR=2)
All pairs strictly orthogonal per Type I codebook rank-1 rule
(same x1, x2 differ by 2). 2-way MU-MIMO working end-to-end.
Also includes:
- ri_bitlen=0 fix in evaluate_cqi_report (uninitialized r_index)
- OAI_MU_MIMO=1 env to enable, OAI_MU_MIMO_RELAXED=1 for relaxed test
- Diagnostic logs every 200th call: ENTER + per-skip-reason
OpenAirInterface License
The source code is distributed under CSSL v1.0. Some files, such as for orchestration, are distributed under MIT license(MIT.txt). Documentation is distributed under Creative Commons Attribution 4.0 International license.
All the files without an explicit copyright header have an implicit "Copyright of OpenAirInterface Authors".
Please see NOTICE for other licenses which are used in the software.
In the past OAI source code has been re-licensed sometimes, here is the history:
- CSSL v1.0 starting tag 2026.w14
- OAI Public License v1.1 starting tag v1.0 till
af4b0d53 - OAI Public License v1.0: starting tag v.04 till v1.0
- GPL 3: starting tag v.0 till v.04 (only initial implementation of 4G)
Where to Start
- General overview of documentation
- The implemented features
- System Requirements for Using OAI Stack
- How to build
- How to run the modems
Not all information is available in a central place, and information for specific sub-systems might be available in the corresponding sub-directories. To find all READMEs, this command might be handy:
find . -iname "readme*"
RAN repository structure
The OpenAirInterface (OAI) software is composed of the following parts:
openairinterface5g
├── charts
├── ci-scripts : Meta-scripts used by the OSA CI process. Contains also configuration files used day-to-day by CI.
├── CMakeLists.txt : Top-level CMakeLists.txt for building
├── cmake_targets : Build utilities to compile (simulation, emulation and real-time platforms), and generated build files.
├── common : Some common OAI utilities, some other tools can be found at openair2/UTILS.
├── doc : Documentation
├── docker : Dockerfiles to build for Ubuntu and RHEL
├── executables : Top-level executable source files (gNB, eNB, ...)
├── maketags : Script to generate emacs tags.
├── nfapi : (n)FAPI code for MAC-PHY interface
├── openair1 : Layer 1 (3GPP LTE Rel-10/12 PHY, NR Rel-15 PHY)
├── openair2 : Layer 2 (3GPP LTE Rel-10 MAC/RLC/PDCP/RRC/X2AP, LTE Rel-14 M2AP, NR Rel-15+ MAC/RLC/PDCP/SDAP/RRC/X2AP/F1AP/E1AP), E2AP
├── openair3 : Layer 3 (3GPP LTE Rel-10 S1AP/GTP, NR Rel-15 NGAP/GTP)
├── openshift : OpenShift helm charts for some deployment options of OAI
├── radio : Drivers for various radios such as USRP, AW2S, RFsim, 7.2 FHI, ...
├── targets : Some configuration files; only historical relevance, and might be deleted in the future
└── tools : Tools for use by the developers/ci machines: code analysis and formatting
How to get support from the OAI Community
You can ask your question on the mailing lists.
Your email should contain below information:
- A clear subject in your email.
- For all the queries there should be [Query] in the subject of the email and for problems there should be [Problem].
- In case of a problem, add a small description.
- Do not share any photos unless you want to share a diagram.
- OAI gNB/DU/CU/CU-CP/CU-UP configuration file in
.confformat only. - Logs of OAI gNB/DU/CU/CU-CP/CU-UP in
.logor.txtformat only. - In case your question is related to performance, include a small description of the machine (Operating System, Kernel version, CPU, RAM and networking card) and diagram of your testing environment.
- Known/open issues are present on GitLab, so keep checking.
Always remember a structured email will help us understand your issues quickly.