Method and apparatus for achieving pass control of transmission cells

A method of pass control of transmission cells for successively receiving frames each mapped with a plurality of cells partially including a synchronizing field at a cell processing apparatus, establishing frame synchronization, dealing with one-bit errors in the headers of the cells by correcting the bits, dealing with multi-bit errors of 2 bits or more by establishing synchronization of the cells while discarding cells, and passing cells extracted from the frames through the cell processing apparatus, comprising:

• a first step of monitoring a communication quality of each frame of said successively received frames;
• a second step of temporarily buffering the plurality of cells contained in each monitored frame, frame by frame;
• a third step of determining whether or not the communication quality in bit error of bits comprising said monitored frame exceeds a predetermined threshold of a bit error level;
• and
• a fourth step of discarding only a cell or cells each including said one-bit error and/or multi-bit errors in said header from one frame's worth of the buffered cells when said communication quality deteriorates exceeding said threshold bit error level and thus prohibiting said discarded cell or cells from passing through said cell processing apparatus, while, when said communication quality does not exceed said threshold bit error level, discarding only a cell or cells each including said multi-bit errors from said one frame's worth of the buffered cells and thus passing the remaining buffered cells through said cell processing apparatus.