HITLESS FRAME SWITCHING SCHEME FOR SDH NETWORKS

In current SDH transmission equipment, channel switching for channel c utoffs and hardware failures, etc., is automated. However, instantaneo us signal loss can occur with such channel switching. Protecting a sys tem from failures with a high reliability for network failures is an i mportant task. In this paper, a new hitless frame-switching scheme tha t triggers switching by detecting bit errors for each frame is propose d. This scheme does not allow a loss of one bit in downstream equipmen t even when a sudden failure occurs. In addition, it improves the erro r rate of the downstream equipment under normal operating conditions b y switching to an error-free frame for each frame. It has been confirm ed in a trial LSI with a path (virtual container-4: VC-4) as a frame t hat these capabilities are realized with precision.