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inet-framework
AckingMac don't work properly
Hi to all, the last two weeks I try to make a simple scenario of two nodes client and server to communicate wirelessly. I connect the two nodes with a router. I use for radio medium the simplest model the UnitDiskRadioMedium and for mac the AckingMac.
When I run the simulation I get the following error
Received frame from upper layer while already transmitting. -- in module (inet::physicallayer::UnitDiskRadio)
To run the simulation properly I need to add a low value to
**.propagation.propagation speed.
From that, I know the radio communication on an Ideal medium is almost the speed of light.
After some conversation in the oment++ forum, we find that maybe is a bug in AckingMac. I have attached below the files to reproduce the bug (.ned and .ini). I use omnet++ 5.6 and INET Version 4.2.2
I encountered the same error when using UnitDiskRadioMedium and AckingMac. I was using a transport layer protocol that sent 2 packets back to back in one function, then AckingMac::handleUpperPacket() was invoked back to back (i.e. twice) before Radio::handleUpperPacket() was invoked for the first packet. The problem was AckingMac::handleUpperPacket() uses radio->getTransmissionState() to check if radio is already transmitting a packet, if so, it should delay packet transmission, however, when AckingMac::handleUpperPacket() was invoked for the second packet, the first packet hasn't gone through Radio::handleUpperPacket() yet, hence AckingMac doesn't know the radio should be occupied by the first packet, and sends the second packet to transmission as well.
Right now I set useAck = true to bypass the problem, but I guess AckingMac should be fixed to keep state about radio transmission status. That's just my thought.
Which INET version are you using? Can you check if the problem also happens in the latest INET master branch?
