  Full-duplex communication allows a terminal to transmit and receive signals
simultaneously, and hence, it is helpful in general to adapt transmissions to
received signals. However, this often requires unaffordable complexity. This
work focuses on simple non-adaptive transmission, and provides two classes of
channels for which Shannon's information capacity regions are achieved without
adaptation. The first is the injective semi-deterministic two-way channel that
includes additive channels with various types of noises modeling wireless,
coaxial cable, and other settings. The other is the Poisson two-way channel,
for which we show that non-adaptive transmission is asymptotically optimal in
the high dark current regime.
