| 摘要 |
PROBLEM TO BE SOLVED: To protect a user frame certainly against damage and to surely prevent a maintenance frame from being left untransmitted. SOLUTION: First, it is detected whether a user frame and a maintenance frame are transmitted or not. As the result of this detection, when it is detected that the user frame is being transmitted, a maintenance frame accompanied with a ceratin IFG is transmitted after the user frame is transmitted. On the other hand, it is detected that the maintenance frame is being transmitted, the user frame accompanied with a certain IFG is transmitted after the maintenance frame is transmitted. As mentioned above, the maintenance frame accompanied with a certain IFG is incorporated without simply delaying the user frame so as to incorporate the maintenance frame into IFG, so that the user frame is protected intrinsically against damage, and the maintenance frame prevented substantially from being left untransmitted. COPYRIGHT: (C)2006,JPO&NCIPI
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