Signal is too weak ? (Omnet++& Mixim)

Question

What are the causes of this warning "Signal is too weak" in the output of the network simulation ?

Currently, i'm using Omnet++ 4.2, Mixim 2.2 and Veins 2.0-rc1

I know that is related to many factors including the TwoRayInterferance model, in order to understand the underlying cause, i have several hypothesis :

1. The distance between the two nodes equal or exceed the transmission range, so the signal is too weak to be correctly interpreted.

2. Channel switch of 802.11p (SCH vs CCH) occur juste before such warning, is it possible that the switch causes such thing ? (i read that channel switch causes time guard, where the channel is considered busy)

3. Collision of 2 packets, that are scheduled at the same time : with the CSMA/CA broadcast mode of 802.11p, air frames are directly send if the channel is detected as idle, so if two nodes decide to send air frames at the same time, collision can occur and produce "signal is too weak" warning

Can someone confirm what i'm suggesting ?

Many thanks,

Answer 1

I am commenting just for future reference: the "signal too weak" in Veins 1 referred to signals that were received weaker than the sensitivity threshold (see code). From Veins 2 onwards, the debug message was replaced with the somewhat more verbose "packet was not detected by the card. power was under sensitivity threshold" (see code)