| 摘要 |
In a data communication system with an automatic repeat request (ARQ) protocol, a method/system capable of setting an optimum value of the RTF, which is used for threshold value of waiting time from transmitting a certain frame until retransmitting the same frame due to no acknowledgement during the waiting time, is provided. During the operation for establishing synchronization, in which a frame for control signal is transmitted repeatedly until receiving acknowledgement from the other end of apparatus, between arbitrary two apparatuses, the transmission delay is detected by using a forward count control information and backward count control information which are newly added in the forward channel information field of the frame format. The forward count control information is incremented by one for every repeated frame, and when the receiving apparatus has received one of the repeated frames, the value of the forward count control information is copied to the backward count control information in a frame to be returned. At the transmission apparatus, when the acknowledgement frame has been received, transmission delay is calculated by subtracting the value of the backward count control information in the received frame from the value of the forward count control information for a frame having been transmitted just before. This subtracted value is used as the RTF.
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