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PHY: fix: breakpoint distances use the 3.0e8 m/s the reports define
TR 36.814 Table B.1.2.1-1, TR 36.873 Table 7.2-1 and TR 38.901 Table 7.4.1-1 all introduce the breakpoint distance with the same note: c = 3.0e8 m/s is the propagation velocity in free space. The three models divided by INET's SPEED_OF_LIGHT, 299792458 m/s, which puts every breakpoint 0.07% further out than specified. That reads like a rounding difference of no consequence, and it would be if the breakpoint only chose a branch. It does more: dBP appears in the beyond-breakpoint LOS formulas themselves, in the -9 log10(dBP^2 + (hBS - hUT)^2) term of 3D-UMi, UMi-Street Canyon and UMa and in the PL1(dBP) + 40 log10(d3D/dBP) form of RMa. Every LOS result past a breakpoint therefore came out about 0.005 dB below the specified value. The value is named rather than repeated at each of the thirteen sites, so that the reason it is not the exact speed of light stays attached to it.
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4 files changed

Lines changed: 23 additions & 13 deletions

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‎src/simu5g/stack/phy/channelmodel/PathLossModel.h‎

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -49,6 +49,16 @@ class PathLossModel
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double log10CarrierFrequencyGHz_ = 0;
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bool tolerateMaxDistViolation_ = false;
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52+
/*
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* Propagation velocity in free space, as the breakpoint-distance notes of
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* all three reports define it. This is the rounded 3.0e8 m/s they write,
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* not the exact speed of light: the breakpoint distance appears in the
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* beyond-breakpoint path-loss formulas themselves and not only in the
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* branch condition, so the two choices differ by about 0.005 dB on every
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* LOS link past a breakpoint.
59+
*/
60+
static constexpr double PROPAGATION_VELOCITY = 3.0e8;
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public:
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virtual ~PathLossModel() {}
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‎src/simu5g/stack/phy/channelmodel/Tr36814PathLossModel.cc‎

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -91,7 +91,7 @@ double Tr36814PathLossModel::getShadowingStdDev(double d3D, double d2D, bool los
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{
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// Breakpoint distance of the RMa/SMa path loss, the only scenarios whose
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// LOS branch uses different sigma values below and above it.
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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return selectStdDev(d3D < dbp, losState);
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}
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@@ -167,7 +167,7 @@ double Tr36814PathLossModel::computeUrbanMicro(double d, bool los)
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d = 10;
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double dbp = 4 * (hNodeB_ - 1) * (hUe_ - 1)
170-
* (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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* (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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if (los) {
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// LOS situation
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if (d > 5000) {
@@ -200,7 +200,7 @@ double Tr36814PathLossModel::computeUrbanMacro(double d, bool los)
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d = 10;
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double dbp = 4 * (hNodeB_ - 1) * (hUe_ - 1)
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* (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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* (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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if (los) {
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if (d > 5000) {
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if (tolerateMaxDistViolation_)
@@ -238,7 +238,7 @@ double Tr36814PathLossModel::computeSubUrbanMacro(double d, double& dbp, bool lo
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d = 10;
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dbp = 2 * M_PI * hNodeB_ * hUe_
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* (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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* (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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if (los) {
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if (d > 5000) {
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if (tolerateMaxDistViolation_)
@@ -281,7 +281,7 @@ double Tr36814PathLossModel::computeRuralMacro(double d, double& dbp, bool los)
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d = 10;
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dbp = 2 * M_PI * hNodeB_ * hUe_
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* (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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* (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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if (los) {
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// LOS situation
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if (d > 10000) {

‎src/simu5g/stack/phy/channelmodel/Tr36873PathLossModel.cc‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -83,7 +83,7 @@ double Tr36873PathLossModel::getShadowingStdDev(double d3D, double d2D, bool los
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// Breakpoint distance of the RMa/SMa path loss, the only scenarios whose
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// LOS branch uses different sigma values below and above it. Unlike
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// TR 36.814, the comparison uses the 2D distance (Q1).
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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return selectStdDev(d2D < dbp, losState);
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}
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@@ -140,7 +140,7 @@ double Tr36873PathLossModel::computeUrbanMicro3D(double threeDimDistance, double
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// compute break-point distance
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double hNodeB = hNodeB_ - 1.0;
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double hUe = hUe_ - 1.0;
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double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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double pLoss_los = 0.0;
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if (twoDimDistance < dbp)
@@ -208,7 +208,7 @@ double Tr36873PathLossModel::computeUrbanMacro3D(double threeDimDistance, double
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double hNodeB = hNodeB_ - hEnvir;
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double hUe = hUe_ - hEnvir;
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211-
double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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double pLoss_los = 0.0;
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if (twoDimDistance < dbp)
@@ -243,7 +243,7 @@ double Tr36873PathLossModel::computeRuralMacro3D(double threeDimDistance, double
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throw cRuntimeError("Error: rural macrocell path loss model is valid for d < 10000 m");
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}
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246-
double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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double a1 = (0.03 * pow(hBuilding_, 1.72));
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double b1 = 0.044 * pow(hBuilding_, 1.72);

‎src/simu5g/stack/phy/channelmodel/Tr38901PathLossModel.cc‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -85,7 +85,7 @@ double Tr38901PathLossModel::getShadowingStdDev(double d3D, double d2D, bool los
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// the LOS branch of that scenario uses different sigma values below and
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// above it. The comparison uses the 2D distance (Q1), like the base
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// classes' shadowing breakpoint.
88-
double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
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double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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bool belowBreakpoint = d2D < dbp;
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9191
switch (scenario_) {
@@ -185,7 +185,7 @@ double Tr38901PathLossModel::computeUrbanMacro3D(double threeDimDistance, double
185185
}
186186
double hNodeB = hNodeB_ - hEnvir;
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double hUe = hUe_ - hEnvir;
188-
double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
188+
double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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190190
// Compute LOS path loss
191191
double pLoss_los = 0.0;
@@ -225,7 +225,7 @@ double Tr38901PathLossModel::computeUrbanMicro3D(double threeDimDistance, double
225225
double hEnvir = 1.0;
226226
double hNodeB = hNodeB_ - hEnvir;
227227
double hUe = hUe_ - hEnvir;
228-
double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
228+
double dbp = 4 * hNodeB * hUe * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
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230230
// Compute LOS path loss
231231
double pLoss_los = 0.0;
@@ -268,7 +268,7 @@ double Tr38901PathLossModel::computeRuralMacro3D(double threeDimDistance, double
268268
}
269269

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// Compute break-point distance
271-
double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / SPEED_OF_LIGHT);
271+
double dbp = 2 * M_PI * hNodeB_ * hUe_ * (carrierFrequencyHz_ / PROPAGATION_VELOCITY);
272272

273273
double h = 5.0; // Average building height
274274
double A = 0.03 * pow(h, 1.72);

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