Abstract

In a conventional case where a preamble length is adjusted in a communication network, even if there is a frame (cycle) in which the length of the preamble has already been adjusted by a preceding station in the direction in which it is increased or decreased, if it is determined on the basis of the decision conditions of an active station that the length of the preamble of such a frame should be increased or decreased, the length of the preamble is adjusted in the direction in which it is further increased or decreased. However, according to the present invention, the length of each preamble which is inputted to a buffer is monitored, and if it is determined that the preamble length of a frame has already been adjusted in the same increasing or decreasing direction, adjustment of the preamble length of the frame is inhibited and such adjustment is carried forward to a succeeding frame. If it is determined that the preamble length of the succeeding frame has also already been adjusted in the same increasing or decreasing direction, the adjustment of the preamble length of the frame is further carried forward to a following frame. Accordingly, repetition of preamble length adjustment with respect to the same frame is prevented, so that resistance to data destruction can be remarkably improved.