Simu5G 1.5.0

This release continues the architectural overhaul of Simu5G. Major themes include consolidating Control Plane functions under the RRC module, adding QoS support via DRBs and the SDAP protocol, restructuring Ip2Nic and other modules for cleaner architecture, and improving type safety throughout the codebase.

Tested with INET-4.5.4 and OMNeT++ 6.3, compatible with INET-4.6.0 and OMNeT++ 6.1 through 6.4.

More explicit Control Plane modeling

Continuing the direction set in v1.4.3, code fragments that implement pieces of
the 3GPP Control Plane have been identified throughout the codebase and collected
under the Rrc module. Rrc is now a compound module with the following
submodules:

• BearerManagement: The former simple Rrc module, renamed and extended.
  It now owns the lifecycle (creation, deletion, lookup) of all PDCP and RLC
  entities. Previously, entity management was scattered across the monolithic
  PDCP module and the LteRlcUm/LteRlcAm modules.

• Registration: Node registration and deregistration logic, previously
  embedded in Ip2Nic, was moved here.

• HandoverController: Handover decision and execution logic was extracted
  from LtePhyUe into this new module. This is architecturally more correct,
  as handover is an RRC function, not PHY. The internal "handover packet"
  misnomer was corrected to "beacon" (HANDOVERPKT -> BEACONPKT,
  broadcastMessageInterval -> beaconInterval). Several parameters were
  exposed as NED parameters (hysteresisFactor, handoverDetachmentTime,
  isNr).

• D2DModeController: D2D mode selection was moved here from the former
  stack/d2dModeSelection/ directory, and D2D peer tracking from
  LteRlcUmD2D.

QoS support: SDAP, DRBs and per-bearer PDCP/RLC entities

QoS (Quality of Service) support was added through Data Radio Bearers (DRBs)
and the SDAP (Service Data Adaptation Protocol) layer, which is part of the 5G
NR protocol stack. The code is based on a contribution by Mohamed Seliem
(University College Cork); see releases v1.4.1-sdap and v1.4.1-sdap-2 for
details. In this release, the code was substantially reworked and integrated
into the main codebase.

In accordance with the 3GPP architecture, the PDCP and RLC layers were
transformed so that they purely consist of per-DRB entities, created and
configured by BearerManagement (RRC). Each DRB has dedicated PDCP TX/RX and
RLC TX/RX entity modules, wired directly to each other via per-bearer gate
connections.

Details:

• SDAP protocol layer: An SDAP implementation was added, providing
  QFI-to-DRB routing with a JSON-configured DrbTable. The SDAP layer is
  optional in NR NICs (enabled via hasSdap=true).

• QFI propagation via GTP-U: QFI is set by the application via DSCP,
  picked up by TrafficFlowFilter/UPF, carried in the GTP-U protocol header
  (mirroring the 3GPP PDU Session Container extension header), and extracted
  by the gNB for SDAP routing.

• QoS-aware proportional fairness scheduler: A QoSAwareScheduler was
  added to MAC, supporting QFI-based scheduling with configurable weight
  constants. Enable with LteMacEnb.schedulingDisciplineDl/Ul = "QOS_PF".

• DRB configuration in JSON: DRB configuration is split between SDAP
  (sdap.drbConfig for QFI-to-DRB routing) and MAC (mac.drbQosConfig for
  QoS scheduler parameters), both in JSON format.

• Non-IP PDU session support: SDAP was generalized for non-IP PDU session
  types, with PduSessionType enum and upperProtocol in DRB configuration.

• PDCP refactored into per-bearer entities: The former monolithic PDCP
  module (which had six subclass variants for LTE/NR × UE/eNB/D2D) was
  replaced with per-bearer PdcpTxEntity and PdcpRxEntity modules, plus
  PdcpMux for upper-layer routing and DcMux for Dual Connectivity X2
  forwarding. Bypass entities handle the DC secondary leg. Entities communicate
  via OMNeT++ gates, not C++ method calls.

• RLC refactored into per-bearer entities: The former LteRlc compound
  module (containing LteRlcUm/LteRlcUmD2D, LteRlcAm, LteRlcTm) was
  replaced with per-bearer TX/RX entity modules for all three RLC modes (UM,
  AM, TM), plus RlcMux for MAC↔entity routing.

• PDCP↔RLC directly wired: PDCP and RLC entities are connected directly
  via per-bearer gates. All submodules now reside directly at NIC level -- the
  former PdcpLayer and LteRlc compound modules no longer exist.

• Example simulations: simulations/nr/standalone_drb/ with
  multi-UE, multi-QFI configurations.

Ip2Nic decomposed, further module architecture improvements

The Ip2Nic module, which had accumulated various unrelated responsibilities
over time, was decomposed. Several code fragments were factored out into
separate modules:

• analyzePacket() moved to Ip2Nic from PDCP: Packet classification
  (filling FlowControlInfo tags) was moved to where it logically belongs --
  at the IP-to-NIC boundary. The IpFlowInd tag was eliminated. RLC type NED
  parameters (conversationalRlc, etc.) also moved from PDCP to Ip2Nic.

• HandoverPacketHolderUe/Enb: Handover packet buffering was factored out
  of Ip2Nic into separate modules. X2 tunneled packets are now received via
  gates instead of C++ method calls.

• TechnologyDecision: Dual Connectivity technology selection logic was
  extracted into a separate, configurable module that uses NED expressions.

Further module architecture improvements:

• MAC turned into compound module: MAC is now a compound module with AMC
  and DL/UL Scheduler as proper cSimpleModule submodules (previously
  created via new in C++). They perform their own staged initialization.

• UPF and PgwStandard now derive from INET's ApplicationLayerNodeBase.

• PacketFlowObserver refactored to use OMNeT++ signals: Direct C++ calls
  from PDCP, RLC, and MAC into PacketFlowObserver were replaced with
  OMNeT++ signals, fully decoupling the observer from protocol modules.

• Replaced method-call-based packet passing with gate connections in several
  places: LteHandoverManager, DualConnectivityManager, Ip2Nic (X2 path).

Type safety improvements

• Strong typedefs: SIMU5G_STRONG_TYPEDEF macro applied to MacNodeId,
  DrbId, LogicalCid, and Qfi, preventing accidental mixing of ID types.

• Direction enum: LteControlInfo.direction changed from unsigned short
  to a proper Direction enum.

• C++ types extracted: Types previously defined in LteCommon.msg were
  moved into a dedicated LteTypes.h header.

• ROHC header: PDCP header compression now uses a proper ROHC header
  representation instead of simply truncating the IP header.

• FlowControlInfo: lcid field renamed to drbId.

Naming and layout cleanup

• Gate renames throughout the NIC for clarity and consistency:
  MAC_to_RLC/RLC_to_MAC -> upperLayerIn/upperLayerOut and
  macIn/macOut; MAC_to_PHY/PHY_to_MAC -> phyOut/phyIn;
  filterGate -> dnPppg. Several inout gates split into separate input
  and output gates.

• Submodule renames: pdcpUpperMux -> pdcpMux, rlcLowerMux -> rlcMux,
  pppIf -> dpPpp (in UPF/PGW).

• Module renames: DualConnectivityManager -> DcX2Forwarder,
  LteHandoverManager -> HandoverX2Forwarder.

• Improved NED layout of NIC internals for better visualization in Qtenv:
  data-path modules arranged vertically, control-plane modules on the left
  edge, dynamically created PDCP/RLC entities positioned between muxes.

Bug fixes

• LteSchedulerEnb: Fixed multi-UE starvation in multi-DRB scheduling.

Other

• Added tilx fingerprints (resistant to module renames) to the fingerprint
  test suite. Fingerprint test coverage for MEC simulations improved.

• SplitBearersTable turned into std::ordered_map.