PURPOSE: To obtain the system high in availability without deteriorating communication quality by controlling an error correction encoding ratio regardless of a decided occupied band width of single line so as to reduce an average occupied band in the digital satellite communication network system employing the demand assignment multiple access system.

CONSTITUTION: In the digital satellite communication network system employing the demand assignment multiple access system having plural communication stations 3-6 including a network centralized management station 2, each of the communication stations 3-6 is provided with a C/N measurement section 8, which informs the result of C/N measurement to the network centralized management station 2 at any time. Thus, the network centralized management station 2 controls an error correction encoding ratio of a communication station during communication.