Frame phase synchronous system and a method thereof

A method of frame phase synchronous in a digital mobile communications system in which a plurality of relay nodes, switching nodes as slave nodes of the relay nodes, and base station nodes as slave nodes of the switching nodes are provided, said method comprising:

• measuring a frame phase difference, in a relay node, with respect to other relay nodes using a method of calculating a frame phase difference from a propagation delay time through ATM cell loop-back;
• obtaining an optimum shift value as a first shift value for adjusting the phase synchronization in the relay node;
• notifying the first shift value from the relay node to a switching node connected to said relay node as a slave;
• measuring a first frame phase difference, in said switching node, with respect to said relay node and a second frame phase difference with respect to a base station node as the slave using the method of calculating a frame phase difference from a propagation delay time through ATM cell loop-back;
• obtaining a second shift value, in said switching node, by adding the notified first shift value to a shift value derived from the measured second frame phase difference with respect to said relay node for adjusting the phase synchronization in the switching node;
• obtaining a third shift value, in said switching node, by adding the second shift value to a shift value derived from the measured third frame phase difference with respect to said base station node as the slave, for notifying of the third shift value to said base station node;
• and
• adjusting the phase synchronization, in said base station node, by the third shift value notified by said switching node.