A communication array was a small network of transmitting and receiving antennas, sometimes containing subspace amplifiers, designed to enhance or support communications through interstellar space. Communication arrays were often interconnected with sensor arrays and could be deployed as platforms in space, as essential components of starships, or in larger installations on planets.
A communication array could be individual installations such as Epsilon IX station, or linked into networks as in the Hirogen communications network. (Star Trek: The Motion Picture; VOY: "Message in a Bottle")
Communication arrays were a vital form of technology for interstellar travel and could have tremendous scientific as well as military value. The Dominion communication array on AR-558 was an example of the latter and was the focus of considerable resources during the Dominion War. (DS9: "The Siege of AR-558")