How are collisions handled in UnetStack's "BasicAcousticChannel"

[viktorlidstrom]

AFAIK, this is not described in the unet handbook. When two packets collide in "BasicAcousticChannel" (overlap in time), are both lost? Are they used to adjust the SNR of each other when simulating the bit errors in "BPSKFadingModel", or is some other approach used?

[mchitre]

The HalfDuplexModem model used as the default in the simulator permits only one reception at a time. If it detects a second reception while one reception is ongoing, it generates a CollisionNtf for the second reception and discards it.

The BasicAcousticChannel tracks all the incoming receptions to compute SINR. For on ongoing reception, any new incoming receptions (even if HalfDuplexModem rejects them as collisions) contribute to the interference term in the SINR. Currently, the BasicAcousticChannel is conservative and counts any overlap in time as interference (i.e., does not reduce interference contribution for partial overlaps). When the reception ends, if the SINR is used to drive the random process that determines successful reception or otherwise. The BasicAcousticChannel delegates that to the BPSKFadingModel that uses a simple model appropriate for BPSK in a Rayleigh/Rician fading channel to decide on packet success.

[viktorlidstrom]

Perfect! Thank you for the answer, Mandar :)