I use Veins-4a2 and I have modified the scenario of the demo example. I have added a new wsm which is ACK when a node reveives a message, it sends an ACK message to the source node. I have add this line in onData() function:
sendWSM(prepareWSM("ack", ackLengthBits, type_SCH, ackPriority, sourcenode.idNode, 2));
and I changed certainly the prepareWSM and handleLowerMsg() functions in BaseWaveApplLayer.cc, but when I execute the simulation, it crashes after 10 seconds. This is the error message:
Error in module (Mac1609_4) RSUExampleScenario.node[2].nic.mac1609_4 (id=240) at event #1196, t=9.210177776741: Model error: ASSERT: condition useSCH false in function handleUpperMsg, veins/modules/mac/ieee80211p/Mac1609_4.cc line 259.
Is that I do not have the right to reuse the SCH channel for the ACK message? How can I correct this problem please?
The 1609.4 MAC layer of Veins 4a2 can be used in one of two operation modes: single channel and multi channel. The behavior can be configured by setting this parameter of the .ned file:
// cycle between an SCH and the CCH (or stay on CCH all the time) bool useServiceChannel = default(true);
From the error message you are posting it appears you have set this parameter to false, meaning you want the radio to always stay on the Control Channel (CCH). At the same time, the code you posted requests a message to be transmitted over a Service Channel (SCH).
You are thus requesting mutually exclusive behavior.
Veins correctly identified this and aborted your simulation.