FriisPropagationLossModel

[Leticia]

Dear all:

I have an important doubt, Im studying the LteHelper and Propagation-loss-model code for Friis Propagation and I saw that this model dont use the frequency of uplink, I dont know if is working properly cause lambda is not set according the frequency of downlink and for uplink and this will affect the performance of the network.

I must have a pathloss for uplink and another one for downlink and for this it must use two different frequencies and indeed two different lambda values.

I will appreciate any help on this matter.

Regards

[Fadhil Firyaguna]

I would try to instance two different channel helpers in the script, and set up the lambda value for each channel separately. Just a vague idea...

[Marco Miozzo]

Hi all,

the frequency in LTE module is set according the EARFCN parameter both
for downlink and uplink. More info at the following link:
http://lena.cttc.es/manual/lte-user.html#configuration-of-lte-model-parameters

Regards,
marco.

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[Nicola Baldo]

I confirm what reported by Marco. However, this works only for propagation models that support the "Frequency" attribute, which Friis does not support, as reported in bug 1421:
https://www.nsnam.org/bugzilla/show_bug.cgi?id=1421

Needless to say, if someone could fix the problem by preparing a patch for bug 1421, it would be very much appreciated.

Regards,

Nicola

[Leticia]

Dear all, thank you very much for your kind response!

Nicola: Due to I need to use Friis propagation model I  tried to fix this bug in a very quick way by changing the lte-helper as following:

 (I am not sure if this is enough to set the the lambda value for both channel, uplink and downlink but I think it can work for this propagation model)

Thank you in advanced for your help!

Leticia

See in red the changes!

  NS_LOG_LOGIC ("set the propagation model frequencies");
  double dlFreq = LteSpectrumValueHelper::GetCarrierFrequency (dev->GetDlEarfcn ());
  NS_LOG_LOGIC ("DL freq: " << dlFreq);
  bool dlFreqOk = m_downlinkPathlossModel->SetAttributeFailSafe ("Frequency", DoubleValue (dlFreq));
  if (!dlFreqOk)
    {
      m_downlinkPathlossModel->SetAttribute ("Lambda", DoubleValue (300000000/dlFreq));
      NS_LOG_WARN ("DL propagation model does not have a Frequency attribute");
    }
  double ulFreq = LteSpectrumValueHelper::GetCarrierFrequency (dev->GetUlEarfcn ());
  NS_LOG_LOGIC ("UL freq: " << ulFreq);
  bool ulFreqOk = m_uplinkPathlossModel->SetAttributeFailSafe ("Frequency", DoubleValue (ulFreq));
  if (!ulFreqOk)
    {
      m_uplinkPathlossModel->SetAttribute ("Lambda", DoubleValue (300000000/ulFreq));
      NS_LOG_WARN ("UL propagation model does not have a Frequency attribute");