D2D Multicast : MAC receives feedback on an unexisting H-ARQ tx buffer about simulte

[procodemechanics]

Upon running more trials and experimenting with the distribution of number of sender and receiver nodes, the main take away is that increasing the size of packet and the number of vehicles in the simulation results in this error. I also observe the following :

1. For less dense network of vehicles, the above problem only arises when a lot of senders are grouped together.
   For example, suppose I have 100 cars in the simulation where the Alert packet sent is of size 10 bytes,
   `.car[0..49].udpApp[].typename = "AlertSender"

.car[49..99].udpApp[].typename = "AlertReceiver"`

If the senders are grouped in smaller groups and uniformly distributed amongst the receiver nodes, the error is not encountered. For example,
`.car[0..4].udpApp[].typename = "AlertSender"

.car[5..9].udpApp[].typename = "AlertReceiver"

.car[10..14].udpApp[].typename = "AlertSender"

.car[15..19].udpApp[].typename = "AlertReceiver"

...`

If the Alert packet size is increased to 300 bytes, this above distribution of 50 Senders and 50 Receivers encounters the same error. However, if I reduce the number of senders to 25 and have 75 receivers instead of 50, the simulation works without error.

2. For highly dense vehicle network, with suppose 400 vehicles, and packet size of 300 bytes, this sender to receiver ratio (as seen in point 1 to be 25:75) needs to drop even further to somewhere about 5:75 to have a proper simulation run.

Why is this behavior observed when the only thing changing is the number of vehicles?