| 摘要 |
PURPOSE:To perform efficient data transmission by paying attention to the cause of deterioration in circuit characteristics when an error of transmission is detected, and indicating one of plural error control levels selectively to a transmitting station. CONSTITUTION:The system controller 206 of a receiving station 200 once detecting an error occurring to receive data refers to circuit state information from a main channel modulator and demodulator 202. The controller 206 decides on whether the error occurs accidentally or not on the basis of the state information, and discriminates the state after the error occurrence, i.e. the force of recovery from the error. When the decision that recovery to an excellent state is possible is made, the return of a negative acknowledge signal to the transmitting station 100 is indicated to a backward channel modulator and demodulator 204. When the decision that the recovery is impossible is made, the return of a specific control signal is indicated to the transmitting station 100. The backward channel modulator and demodulator 104 of the transmitting station 100 demodulates the signal and a system controller 106 reports that to the main channel modulator and demodulator 106 of this transmitting station 100 according to the indication of the control signal. |
