Simplex and Unidirectional

Simplex adjective - Allowing communication in only one direction at a time, or in telegraphy allowing only one message over a line at a time.

Unidirectional and simplex are semantically related. In some cases you can use "Unidirectional" instead an adjective "Simplex".

Unidirectional adjective - Operating or moving or allowing movement in one direction only.

Simplex and unidirectional are semantically related. You can use "Simplex" instead an adjective "Unidirectional".