Frame synchronism processing apparatus and frame synchronism processing method

A frame synchronism processing apparatus comprising:

• a plurality of frame synchronism detecting units each for receiving a transmission frame including a plurality of unit frames wherein the unit frames are hierarchically arranged by nesting one another and for detecting the synchronism of the unit frames at each of the hierarchies;
• and
• a compulsory synchronism detecting retrying control unit for compulsorily bringing each of said frame synchronism detecting units at each hierarchy into a synchronism detection retrying mode if the detection of the synchronism of the unit frames by any one of said frame synchronism detecting units at any hierarchy has failed.

A frame synchronism processing method comprising the steps of:

• (a) receiving a transmission frame including a plurality of unit frames wherein the unit frames are hierarchically arranged by nesting one another and for detecting the synchronism of the unit frames at each of hierarchies;
• and
• (b) compulsorily performing a synchronism detection process for each of the unit frames at each hierarchy if the detection of the synchronism of the unit frames has failed at any hierarchy in said step (a).