Session 1 | Brain-to-brain coupling: a mechanism for creating and sharing a social world

On our first session we discussed: Hasson, Uri, et al. "Brain-to-brain coupling: a mechanism for creating and sharing a social world." Trends in cognitive sciences 16.2 (2012).

Bahador presented the paper for us, we had several problems in understanding different parts like first paragraph second page, where they claim that : 

Brain-to-brain coupling is analogous to a wireless communication system in which two brains are coupled via the transmission of a physical signal (light,sound, pressure or chemical compound) through the shared physical environment.

The phrase "wireless communication" was ambiguous to us, does it mean that we should strictly use a wireless technology to create a brain-to-brain coupling?
As we were going through the paper, we reached to the question "are all species social?", do we really need a "brain-brain" communication to understand complex behaviors?