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spectrum: Calculate PSD by combining received power, even when no precoding matrix is set

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This commit is contained in:
Gabriel Ferreira
2024-12-11 14:50:08 +01:00
parent fb5ed767be
commit e299ddba3a
2 changed files with 45 additions and 35 deletions
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65
src/spectrum/model/three-gpp-spectrum-propagation-loss-model.cc
View File

@@ -280,49 +280,50 @@ ThreeGppSpectrumPropagationLossModel::CalcBeamformingGain(
numRxPorts,
isReverse);
// The precoding matrix is not set
NS_ASSERT_MSG(rxParams->psd->GetValuesN() == rxParams->spectrumChannelMatrix->GetNumPages(),
"RX PSD and the spectrum channel matrix should have the same number of RBs ");
// Calculate RX PSD from the spectrum channel matrix H and
// the precoding matrix P as: PSD = (H*P)^h * (H*P)
MatrixBasedChannelModel::Complex3DVector psd;
MatrixBasedChannelModel::Complex3DVector p;
if (!rxParams->precodingMatrix)
{
// Update rxParams->Psd.
// Compute RX PSD from the channel matrix
auto vit = rxParams->psd->ValuesBegin(); // psd iterator
size_t rbIdx = 0;
while (vit != rxParams->psd->ValuesEnd())
// When the precoding matrix P is not set, we create one with a single column
p = ComplexMatrixArray(rxParams->spectrumChannelMatrix->GetNumCols(), 1, 1);
// Initialize it to the inverse square of the number of txPorts
p.Elem(0, 0, 0) = 1.0 / sqrt(rxParams->spectrumChannelMatrix->GetNumCols());
for (size_t rowI = 0; rowI < rxParams->spectrumChannelMatrix->GetNumCols(); rowI++)
{
// Calculate PSD for the first antenna port (correct for SISO)
*vit = std::norm(rxParams->spectrumChannelMatrix->Elem(0, 0, rbIdx));
vit++;
rbIdx++;
p.Elem(rowI, 0, 0) = p.Elem(0, 0, 0);
}
// Replicate vector to match the number of RBGs
p = p.MakeNCopies(rxParams->spectrumChannelMatrix->GetNumPages());
}
else
{
NS_ASSERT_MSG(rxParams->psd->GetValuesN() == rxParams->spectrumChannelMatrix->GetNumPages(),
"RX PSD and the spectrum channel matrix should have the same number of RBs ");
// Calculate RX PSD from the spectrum channel matrix, H and
// the precoding matrix, P as:
// PSD = (H*P)^h * (H*P),
// where the dimensions are:
// H (rxPorts,txPorts,numRbs) x P (txPorts,txStreams, numRbs) =
// HxP (rxPorts,txStreams, numRbs)
MatrixBasedChannelModel::Complex3DVector hP =
*rxParams->spectrumChannelMatrix * (*rxParams->precodingMatrix);
// (HxP)^h dimensions are (txStreams, rxPorts, numRbs)
MatrixBasedChannelModel::Complex3DVector hPHerm = hP.HermitianTranspose();
p = *rxParams->precodingMatrix;
}
// When we have the precoding matrix P, we first do
// H(rxPorts,txPorts,numRbs) x P(txPorts,txStreams,numRbs) = HxP(rxPorts,txStreams,numRbs)
MatrixBasedChannelModel::Complex3DVector hP = *rxParams->spectrumChannelMatrix * p;
// Then (HxP)^h dimensions are (txStreams, rxPorts, numRbs)
MatrixBasedChannelModel::Complex3DVector hPHerm = hP.HermitianTranspose();
// Finally, (HxP)^h x (HxP) = PSD (txStreams, txStreams, numRbs)
MatrixBasedChannelModel::Complex3DVector psd = hPHerm * hP;
// Update rxParams->Psd
for (uint32_t rbIdx = 0; rbIdx < rxParams->psd->GetValuesN(); ++rbIdx)
// Finally, (HxP)^h x (HxP) = PSD(txStreams, txStreams, numRbs)
psd = hPHerm * hP;
// Update rxParams->Psd
for (uint32_t rbIdx = 0; rbIdx < rxParams->psd->GetValuesN(); ++rbIdx)
{
(*rxParams->psd)[rbIdx] = 0.0;
for (size_t txStream = 0; txStream < psd.GetNumRows(); ++txStream)
{
(*rxParams->psd)[rbIdx] = 0.0;
for (size_t txStream = 0; txStream < psd.GetNumRows(); ++txStream)
{
(*rxParams->psd)[rbIdx] += std::real(psd(txStream, txStream, rbIdx));
}
(*rxParams->psd)[rbIdx] += std::real(psd(txStream, txStream, rbIdx));
}
}
return rxParams;
}

15
src/spectrum/test/three-gpp-channel-test-suite.cc
View File

@@ -934,9 +934,18 @@ ThreeGppSpectrumPropagationLossModelTest::DoRun()
// 1) check that the rx PSD is equal for both the direct and the reverse channel
auto rxParamsNew =
lossModel->DoCalcRxPowerSpectralDensity(txParams, rxMob, txMob, rxAntenna, txAntenna);
NS_TEST_ASSERT_MSG_EQ((*rxParamsOld->psd == *rxParamsNew->psd),
true,
"The long term for the direct and the reverse channel are different");
if ((rxParamsOld->spectrumChannelMatrix->GetNumCols() ==
rxParamsNew->spectrumChannelMatrix->GetNumCols()) &&
(rxParamsOld->spectrumChannelMatrix->GetNumRows() ==
rxParamsNew->spectrumChannelMatrix->GetNumRows()) &&
(rxParamsOld->spectrumChannelMatrix->GetNumCols() == 1) &&
(rxParamsOld->spectrumChannelMatrix->GetNumRows() == 1))
{
// this is only really true in case of SISO (1x1 non-polarized port array)
NS_TEST_ASSERT_MSG_EQ((*rxParamsOld->psd == *rxParamsNew->psd),
true,
"The long term for the direct and the reverse channel are different");
}
// 2) check if the long term is updated when changing the BF vector
// change the position of the rx device and recompute the beamforming vectors