Handoff Processes on Lrwpan

[abou...@gmail.com]

Dear ns-3 community,
Please i would like to get some clarification regarding the Handoff Processes on Lrpwan.
So, when a source node moves and become outside the coverage of its destination node, all packets sent will be dropped until this source node returns to the same coverage zone. I tested the script lr-wpan-error-distance-plot.cc
My question is which Method/class in the source code can take decision if the packet sent must be delivered or dropped?
Also, which Methode/Class detects that this node isn't in the same coverage.
Many thanks in advance.

[Tommaso Pecorella]

Hi,

please study a bit the code. It's not that hard and it avoids many misunderstandings.

The packet is classified as erroneous (and dropped) by the LrWPanPhy. To be precise in LrWpanPhy::EndRx, but the problem is: if you're asking this, you'll have a hard time in understanding that function... I'm just realistic.

T.

[jhon abraham]

Thank you very Much Tommaso,

i studied the code and specifically the LrWpanPhy::StartRx and LrWpanPhy::EndRx Methods.

if i understand, in the LrWpanPhy::StartRx Method, we calculate the Interference and Noise of every received packet.

After that, we calculate the SNR as a function if m_signal->GetSignalPsd (), lrWpanRxParams->psd, and m_noise variables.

if the SNR<-5 we set the frame as false in the "m_currentRxPacket " variable.

and in the LrWpanPhy::EndRx we test if this value is false or not. if it's false we decode the packet, otherwise, the packet is droped.

My question her is in the SNR calcualtion, i can't see which variable can modify this value given that lrWpanRxParams->psd, m_phyPIBAttributes.phyCurrentChannel, lrWpanRxParams->psd, and m_noise are declared at constructor and don't see if one of these variables has been modified and therfore the SNR.

Thank you for your Help.

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[Tommaso Pecorella]

hi,

you're partially right. The psd is recorded in StartRx, but the interference (and if the packet have to be dropped) is calculated in EndRx.

The only exception is if you receive a packet while you're already receiving another one. In that case the packet is marked as to be dropped in StartTx (it should, I'll double check).

About where to change the params you mentioned, the whole SNR calculation process is handled by the Spectrum model, and for LrWpan in the following files: lr-wpan-spectrum-signal-parameters.{cc,h} and lr-wpan-spectrum-value-helper.{cc,h}

I'd check them.

T.