| 摘要 |
PURPOSE:To improve the transmission efficiency by storing the oldest unconfirmed state variable and starting or restarting a timer applying response reception supervisory operation every change in the oldest unconfirmed state variable so as to recover the error quickly and to reduce the transmission stop time. CONSTITUTION:A state variable storage section, in response to the result of error detection by an error check section 17, stores the transmission sequence number next to an information (I) frame confirmed newly when the oldest unconfirmed state variable changes as the oldest unconfirmed state variable. A timer control module 7 starts or restarts a timer every time the oldest unconfirmed state variable stored in a state variable storage section 18 is changed. Since a response reception supervisory timer is not started nor restarted every time the information (I) frame is sent, if an RR response or an REJ frame from the reception side B is in error, the timeout timing is quickened and the check point retransmission is executed quickly.
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