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Clarification on ChannelLoad and CBR? #50

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m-wegner opened this issue Nov 23, 2018 · 2 comments
Closed

Clarification on ChannelLoad and CBR? #50

m-wegner opened this issue Nov 23, 2018 · 2 comments

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@m-wegner
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m-wegner commented Nov 23, 2018

In our simulations, we are recording the channel load and CBR via two different ways:

  1. In our service, we determine the current CBR via the following snippet:
auto cpp { getFacilities().getConstPtr<artery::DccFacility>()->getChannelProbeProcessor(channel) };
auto scpp { notNullPtr(dynamic_cast<vanetza::dcc::SmoothingChannelProbeProcessor*>(cpp)) };
auto channelBusyRatio = scpp->channel_load().value();
emit(scSignal_channelBusyRatio, channelBusyRatio);
  1. We placed a passive probe based on an earlier implementation in our scenario which does not have a middleware and ITS-G5 services, thus we record the ChannelLoad from VanetRx.cc roughly as follows:
simsignal_t const cSignalChannelLoad = cComponent::registerSignal( "ChannelLoad" );

void Probe::initialize(int stage) {
  // ...
  inet::getContainingNode( this )->subscribe( cSignalChannelLoad, this );
}

void Probe::receiveSignal(..., double cbr, ...) {
  // ...
  vector.record( cbr );
}

As far as we understand it, the CBR according to 1. is a DCC-specific or DCC-dependent metric while the latter one in 2. is a more generic metric for the load on the channel.

Our goal is to investigate how much additional stress our service is putting on the channel, e.g., in addition to CA service. With regards to this goal: Can you give any suggestion which metric is the better one to use?

Thanks in advance!

@riebl
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riebl commented Nov 23, 2018

Some DCC specifications require to smooth the raw measurements before they are used to control channel load. ChannelProbeProcessor is just the interface to integrate such pre-processing stuff. I think it is just fine to record the raw CBR from VanetRx at passive probes.

@m-wegner
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Ok, thanks for the clarification. I think, this confirms our approach.

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