A radio system includes a radio voice terminal, a relay server, a command center and a radio network gateway. The radio network gateway includes a communication module in communication with the relay server; a radio voice control module in communication with the first radio voice terminal, receiving a radio voice signal from the first radio voice terminal; and a processing module in communication with the communication module and the radio voice control module, converting the radio voice signal into a digital voice file, executing a voice recognition process to extract at least one keyword from the digital voice file, and transmitting the at least one keyword to the relay server through the communication module.