I'm somewhat new to Veins and I'm trying to record collision statistics within the sample "RSUExampleScenario" provided in the VM. I found this question which describes what line to add to the .ini file, which I have, but I'm unable to find the "ncollisions" value in the results folder, which makes me think either I ran the wrong .ini line or am looking in the wrong place.
Thanks!
Because collision statistics take time to compute (essentially: trying to decode every transmission twice: once while considering interference by other nodes as usual, then trying again while ignoring all interference), Veins 5.1 requires you to explicitly turn collision statistics on. As discussed in https://stackoverflow.com/a/52103375/4707703, this can be achieved by adding a line *.**.nic.phy80211p.collectCollisionStatistics = true to omnetpp.ini.
After altering the Veins 5.1 example simulation this way and running it again (e.g., by running ./run -u Cmdenv -c Default from the command line), the ncollisions field in the resulting .sca file should now (sometimes) have non-zero values.
You can quickly verify this by running (from the command line)
opp_scavetool export --filter 'module("**.phy80211p") and name("ncollisions")' results/Default-\#0.sca -F CSV-R -o collisions.csv
The resulting collisions.csv should now contain a line containing (among other information) param,,,*.**.nic.phy80211p.collectCollisionStatistics,true (indicating that the simulation was executed with the required configuration) as well as many lines containing (among other information) scalar,RSUExampleScenario.node[10].nic.phy80211p,ncollisions,,,1 (indicating that node[10] could have received one more message, had it not been for interference caused by other transmissions in the simulation.