A system for improving the transmission efficiency of channels involved in multilink communication and reducing the load of processing. A first data transmission apparatus changes the number of transmission channels involved in multilink communication from “x” to “y”, acquires SS (sampling size) and SPF(samples per frame) associated with the number of transmission channels “y” from an SS/SPF table, generates multilink frames based on the acquired SS and SPF, and transmits them to a second data transmission apparatus. When it is detected that the number of transmission channels has been changed from “x” to “y”, the second data transmission apparatus acquires the SS and SPF associated with the number of transmission channels “y” from the SS/SPF table, generates multilink frames based on the acquired SS and SPF, and transmits them to the first data transmission apparatus.