To realize a wideband data transmission which can transmit mass data in a short time and to establish a connection which can perform data transmission in a session format by using both a wideband channel and a mobile radio telephone channel.

A method of transmitting data via at least one wideband channel includes the step of guaranteeing a validation and authentication of the last user by a mobile terminal 50 which is easy to use and is excellent in portability. A control sentence (control statement) for wideband data transmission (control statement) is transmitted via a mobile radio telephone network of at least one channel.