PHY: LtePhyEnb: reject non-positive beaconInterval instead of silently disabling beacons

A zero (or negative) cellInfo.beaconInterval previously meant "no beacons",
conflating the beacon on/off decision with the interval value. Make a
non-positive interval a hard error at initialization so the two knobs stay
orthogonal and configuration is predictable: enableBeacons is the on/off
switch, beaconInterval is always a positive period.

enableBeacons still defaults to enableHandover, so beacon emission is unchanged
in every existing simulation and fingerprints are unaffected (full suite
132/132 OK; no baseline sets beaconInterval<=0).

Author: avarga

src/simu5g/stack/phy/LtePhyEnb.cc

@@ -71,17 +71,16 @@ void LtePhyEnb::initialize(int stage)
         }
 
         beaconInterval_ = cellInfo_->par("beaconInterval");
-        bool enableHandover = par("enableHandover");
+        if (beaconInterval_ <= 0)
+            throw cRuntimeError("cellInfo.beaconInterval must be positive (got %gs); beacons are "
+                    "switched off with enableBeacons=false, not with a zero interval", beaconInterval_);
         bool enableBeacons = par("enableBeacons");
-        bool beaconsWillFlow = enableBeacons && beaconInterval_ != 0;
         // Handover feasibility assessment (and radio link monitoring) in the UEs is driven by
         // these beacons, so handover cannot silently work without them.
-        if (enableHandover && !beaconsWillFlow)
-            throw cRuntimeError("enableHandover=true requires the eNB to broadcast beacons, but "
-                    "they are disabled (enableBeacons=%s, cellInfo.beaconInterval=%gs); set "
-                    "enableBeacons=true and beaconInterval>0, or set enableHandover=false",
-                    enableBeacons ? "true" : "false", beaconInterval_);
-        if (beaconsWillFlow) {
+        if (par("enableHandover").boolValue() && !enableBeacons)
+            throw cRuntimeError("enableHandover=true requires enableBeacons=true: handover "
+                    "feasibility assessment in the UEs is driven by the eNB's periodic beacons");
+        if (enableBeacons) {
             beaconStarter_ = new cMessage("beaconStarter");
             scheduleAt(NOW, beaconStarter_);
         }

src/simu5g/stack/phy/LtePhyEnb.ned

@@ -25,15 +25,17 @@ simple LtePhyEnb extends LtePhyBase
         @class("LtePhyEnb");
 
         // Marks this eNB as a handover target: its beacons are used by UEs for handover
-        // feasibility assessment. Requires enableBeacons (beacons are the input to that
-        // assessment); the module errors out at initialization if beacons are disabled.
+        // feasibility assessment. Requires enableBeacons=true (the default when handover is
+        // on); the module errors out at initialization if beacons are disabled while
+        // handover is enabled.
         bool enableHandover = default(false);
 
         // Enables broadcasting periodic beacons (at cellInfo.beaconInterval). Beacons are the
         // measurement signal UEs use both for handover feasibility assessment and for radio
-        // link monitoring (RLF detection), so they are decoupled from enableHandover to allow
-        // radio link monitoring without handover. Defaults to enableHandover for backward
-        // compatibility. Broadcasting also requires cellInfo.beaconInterval > 0.
+        // link monitoring (RLF detection), decoupled from enableHandover so radio link
+        // monitoring can run without handover. Defaults to enableHandover (beacons flow
+        // exactly when handover is enabled). cellInfo.beaconInterval must be positive: a
+        // zero/negative interval is an error -- switch beacons off with enableBeacons=false.
         bool enableBeacons = default(enableHandover);
 
         double targetBler = default(0.001);