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What's New in Simu5G

v1.4.3 (2026-02-18)

This release represents a major milestone in the complete overhaul of the Simu5G codebase to make it architecturally more compliant with the 3GPP specifications, modernize the code, and adopt the best practices of the INET Framework on which it is based. The goal is to pave the way for a clean implementation of new protocol features such as TSN support.

Tested with INET-4.5.4 and OMNeT++ 6.3, updated for INET-4.6.0 compatibility.

Key achievements in this release:

  • More explicit Control Plane modeling: Simu5G is advertised as a User Plane simulator, but since it was also used to model dynamic scenarios such as handovers, it always contained elements of the Control Plane distributed across various modules. The new direction is to make these elements more explicit and centralized, such as creating dedicated RRC (Radio Resource Control) and Session Management Function (SMF) implementations. It is an explicit non-goal to simulate Control Plane messaging -- its functionality will be implemented with C++ method calls across modules. Thus, Simu5G remains a User Plane simulator, but with the possibility to more faithfully model dynamic scenarios with heavy Control Plane involvement. While this goal is not fully realized in this release, many changes point into that direction.

  • Control info refactoring: Cleaned up UserControlInfo and FlowControlInfo by removing 5+ unused fields and splitting out smaller, focused tags. For example, IPv4 addresses, only used between Ip2Nic and PDCP, have been factored out into an IpFlowInd tag. This improves modularity, reduces coupling between protocol layers, and makes the code easier to maintain and extend.

  • Added vital missing fields to PDCP and MAC headers: Protocol layers now use proper header fields instead of "tunnelling" information via UserControlInfo and FlowControlInfo packet tags that would not exist in a real implementation. For example, PDCP sequence numbers are now carried in PDCP headers, and LCIDs are stored in MAC PDU subheaders. This makes the simulation more realistic and packet contents more inspectable in Qtenv.

  • Explicit setup of logical connections instead of on-the-fly discovery: This is a key architectural change, which also largely motivated the previous items. In previous iterations of Simu5G, data structures associated with logical connections / bearers were created in each protocol layer as they encountered packets that belonged to new connections. Moreover, part of the connection state was carried along by the packets in FlowControlInfo tags instead of stored inside the protocol. While this modeling approach still allowed for faithful simulation of the traffic while keeping the implementation simple, it has become a roadblock for implementing complex dynamic scenarios where connections come and go. In this iteration, centralized session and bearer management (SMF-like functionality) was added to the Binder module, and RRC modules were added to NICs to carry out local configuration. This brings the architecture closer to the 3GPP control/user plane separation, making it easier to implement features like handovers correctly. This is work in progress: SMF is still part of Binder and not a separate module, and connection setup is still triggered by the first packet of the connection hitting PDCP on the way out. However, moving the SMF code into its own module will be trivial, and the single Binder method call in PDCP can now be easily replaced with static configuration or with calls from a more detailed Control Plane implementation.

  • Removed incomplete MIMO support: Removed MIMO-related code and parameters. The existing MIMO code was incomplete (e.g., PMI values were computed but never used). Removing it simplifies the codebase and model parameterization, and avoids confusion about capabilities. MIMO support will be added in a future release, with a different approach.

  • Initialization cleanup: Reorganized module initialization into well-defined, Simu5G-specific init stages. This eliminates hidden cross-module dependencies, makes the initialization order explicit and verifiable, and prevents subtle bugs caused by modules accessing uninitialized data in other modules.

Further notable changes:

  • In UE models, masterId and nrMasterId were renamed to servingNodeId and nrServingNodeId. The old names were confusing because "Master" has a specific meaning in Dual Connectivity (Master eNB vs Secondary gNB), unrelated to the UE's serving node.

  • In UE models, the macCellId, nrMacCellId parameters were removed. In practice, the code already used the serving node ID as cell ID.

  • macNodeId assignment was moved to NED, and now it is based on the new simu5g_seq() NED function that generates an integer sequence. This replaces the earlier approach where node IDs were assigned by Ip2Nic during initialization, and stored back into the module parameters for other modules to use.

  • LteRlcPduNewData and LteRlcSdu packet chunks were converted to packet tags, as they represent internal metadata rather than actual protocol data.

  • In the C++ code, merged the ENODEB and GNODEB node type enum values into a single NODEB value, with a separate isNr flag where needed. This change simplified a large number of "if" conditions throughout the codebase.

To port your existing Simu5G simulations to this version, apply the following changes to the ini files:

  • Change masterId to servingNodeId (and nrMasterId to nrServingNodeId), unless it refers to the Master/Secondary distinction in a Dual Connectivity setup.

  • Remove macCellId and nrMacCellId parameter assignments for UE modules.

  • Delete ini entries that set the following removed MIMO-related parameters: numRus, ruRange, ruStartingAngle, ruTxPower, antennaCws, muMimo, pmiWeight, lambdaMinTh, lambdaMaxTh, lambdaRatioTh, feedbackGeneratorType.

  • For initialTxMode, the following values are no longer valid: SINGLE_ANTENNA_PORT5, OL_SPATIAL_MULTIPLEXING, CL_SPATIAL_MULTIPLEXING, MULTI_USER. Remove the parameter assigment to use the default.

There are many more changes that potentially affect existing simulations, and projects extending, or built on top of, Simu5G. They cannot all be covered here in detail - see the git history for details.

v1.4.2 (2025-11-27)

This is primarily a bugfix release.

  • Pdcp: Fixed Dual Connectivity bug where separate PDCP entities were incorrectly created for LTE and NR legs of a Split Bearer instead of using a single shared entity. This fix breaks RLC-UM packet loss statistics which (incorrectly) inferred packet loss from PDCP sequence numbers.

  • RlcUm: Removed packet loss statistics that incorrectly relied on PDCP sequence numbers (PDCP sequences are not contiguous in Dual Connectivity setups)

  • PacketFlowManager: Renamed to PacketFlowObserver, updated NED documentation.

  • Statistics collection refined, e.g. remove recording "sum" and/or "mean" where it does not make sense; use new "rateavg" filter for computing average throughput.

  • Binder: New utility functions: isGNodeB(), getUeNodeId().

  • Apps: Added sequence numbers to VoIP and VoD packet names, to facilitate tracing with Qtenv.

  • NED documentation: Added content to simu5g-index.ned including version number and WHATSNEW.

v1.4.1 (2025-10-06)

This is a minor update that brings further refactoring of the C++ code for clarity, improvements in the C++ interface of the Binder module, and some minor bug fixes. These improvements were contributed by Andras Varga (OMNeT++ Core Team).

Notable changes:

  • Binder: Partial rationalization of the C++ interface, via renaming/replacing/removing methods. See the git history for changes.

  • Updated IP addresses in the IPv4 configuration files: use 10.x.x.x addresses for the Core Network, and 192.168.x.x addresses for external addresses

  • Visual improvement: node IDs are now displayed over module icons

  • In MEC, do not use module IDs for bgAppId, deviceAppId and other IDs, and do not encode module ID into module names. That practice made simulations brittle for regression testing via fingerprints.

  • PDCP: Eliminated tweaking of srcId/destId in FlowControlInfo when sending downlink packets over the X2 link in a Dual-Connectivity setup.

  • Various additional fixes and changes to improve code quality.

v1.4.0 (2025-09-18)

Compatible with OMNeT++ 6.2.0 and INET 4.5.4.

This release marks an important milestone in the ongoing transformation of Simu5G. While not introducing behavioral changes, this intermediate release focuses on restructuring the codebase to improve clarity, safety, and maintainability. Major updates include a reorganized directory structure, enforcing a consistent naming convention, making make packets more easily inspectable, and refactoring of parts of the C++ code to pave the way for changes in future versions. Although the release is not source-compatible with previous versions, existing simulations will continue to work unchanged once adjusted to follow the various rename operations. These improvements were contributed by Andras Varga (OMNeT++ Core Team).

Renames:

  • Sources are now under src/simu5g/ instead of just src/, so that C++ includes start with "simu5g/". This helps identifying Simu5G includes when Simu5G is used as a dependency of other projects.

  • Some folders were moved inside the source tree to a more logical location. For example, the simu5g/nodes/mec/ subtree was promoted to simu5g/mec/.

  • Several source folders were renamed to more closely follow the all-lowercase convention. For example, mec/UALCMP/ became mec/ualcmp/, and mec/MECPlatform became just mec/platform.

  • Several classes were renamed to ensure that only the first letters of acronyms are uppercase. For example, MECHost became MecHost.

  • Several parameters were renamed to enforce camelcase names. For example, bs_noise_figure became bsNoiseFigure, and fading_paths became numFadingPaths. If you have existing Simu5G simulations, review the ini files carefully and update the parameter assignments accordingly. (Caveat: Assignment lines that refer to the old names will be simply ignored by the simulation -- there is no error message for that!)

  • The PdcpRrc modules were renamed to just Pdcp. Likewise, pdcpRrc submodules in NIC compound modules became pdcp.

Further refactoring:

  • Several protocol header classes, while defined in msg files, contained heavy customization in C++ code, including the addition of new fields. Since the writing of those classes, the message compiler in OMNeT++ gained enough features so that most of the customizations were no longer needed, and the desired effect could be achieved in msg files only. This refactoring has the benefit of making packets more inspectable from Qtenv, and packet contents can now be serialized using parsimPack (useful for more thorough fingerprint tests).

  • MacCid is a central data type that pairs an LCID with a nodeId to uniquely identify a logical channel. It used to be a packed integer, and now it was turned into a C++ class with separate fields for the node ID and LCID and with accessor methods, for increased type safety.

  • carrierFrequency used to be a variable of the type double throughout the codebase. The type was changed to GHz (using INET's units.h) for increased type safety. This also helped identifying a bug in certain channel models (LteRealisticChannelModel, BackgroundCellChannelModel) where a double representing GHz instead of Hz was used in computing path loss, resulting in underestimated path loss values.

  • Binder received several WATCHes for increased transparency in Qtenv, and an overhaul of a subset of its API and internal data structures.

  • In the Pdcp modules, the unused EUTRAN_RRC_Sap port (and associated handling code) was removed.

  • Refactoring of internals in several protocol modules, including MAC, PDCP and RLC implementations.

Build:

  • Made the command line build consistent with the IDE build. src/Makefile is now generated/updated implicitly on every build, no need to type "make makefiles".

v1.3.1 (2025-09-18)

This is a minor update for Simu5G-1.3.0. In addition to fixing regressions in the previous release and making some cosmetic improvements, the main highlight of this release is the revamp of the fingerprint test suite, which now provides a more comprehensive safety net against future regressions. Changes in this release were contributed by Andras Varga (OMNeT++ Core Team).

Changes:

  • Example simulations: Marked abstract configs as such (abstract=true) in omnetpp.ini files
  • FlowControlInfo's MacNodeId fields are now properly shown in Qtenv object inspectors
  • Replaced EV_ERROR << lines with throwing cRuntimeError
  • TrafficLightController: fixed startState NED parameter (also changed type from int to string)
  • Fingerprints: CSV files merged into simulations.csv, added missing simulations, standardized on the set of fingerprints computed (tplx, ~tNl, sz), translated gen_runallexamples.py into Python and improved it

Fix regressions in v1.3.0:

  • MECResponseApp: fixed wrong @class annotation
  • BackgroundScheduler: fix "binder_ not initialized" error
  • MecRequestForegroundApp, MecRequestBackgroundGeneratorApp: add back lost parameter defaults
  • BackgroundCellTrafficManager: fix "Not implemented" thrown from getBackloggedUeBytesPerBlock()
  • tutorials/nr/omnetpp.ini: fix missing unit for txPower parameter (dBm)

v1.3.0 (2025-02-06)

  • Compatible with OMNeT++ 6.1.0 and INET 4.5.4
  • New modules: MultiUEMECApp, MecRnisTestApp, UeRnisTestApp
  • Added NED documentation for modules
  • Increased reusability of modules via changes such as replacing hardcoded module paths in the C++ code with NED parameters (binderModule, macModule, etc.), and elimination of ancestorPar() calls by introducing local parameters instead. *
  • Other NED adjustments, such as removal of unused NED parameters and splitting NED files to have one module per file. See doc/NED-changes.txt for details. *
  • Extensive C++ modernization, and adaption of more OMNeT++ best practices. *
  • Various bug fixes.
  • Changes marked with an asterisk were contributed by Andras Varga (OMNeT++ Core Team).

v1.2.3 (2025-01-10)

  • Added support for OMNeT++ 6.1.0 and INET 4.5.4.

v1.2.2 (2023-04-19)

  • Compatible with OMNeT++ 6.0.1 and INET 4.5.
  • Tested on Ubuntu 22.04 and macOS Ventura.

v1.2.1 (2022-07-19)

  • Compatible with OMNeT++ 6.0 and INET 4.4.0.
  • Tested on Ubuntu 20.04.
  • Modifications to support the latest versions of OMNeT++ 6.0 and INET v4.4.0.
  • Refactoring of simulation and emulation folders.
  • Various bug fixes.

v1.2.0 (2021-08-30)

  • Compatible with OMNeT++ 6.0 (pre10 and pre11) and INET 4.3.2.
  • Tested on Ubuntu 16.04, 18.04, 20.04, macOS Catalina, and Windows 7.
  • Added modelling of ETSI MEC entities.
  • Support for real-time emulation capabilities (Linux OS only).
  • Modelling of background cells and background UEs for larger scale simulations and emulations.
  • Several bug fixes.

v1.1.0 (2021-04-16)

  • Compatible with OMNeT++ 5.6.2 and INET 4.2.2.
  • Tested on Ubuntu 16.04, 18.04, 20.04, macOS Catalina, and Windows 7.