Method for inter system soft hand-off

PURPOSE: A soft hand off method between different mobile communication systems is provided to perform a soft hand off by using a global router performing the change of a protocol, an address and a message. CONSTITUTION: In the first step, the first mobile communication system(452) received the request of hand off from a mobile station transmits the message requesting hand off to the global router(513). In the second step, the global router(513) performs the change of a protocol, an address and a message to the hand off request message and then transmits to the second mobile communication system. In the third step, the second mobile communication system allocates the corresponding channel and transmits the hand off response message to the global router. In the fourth step, the global router(513) performs the change of a protocol, an address and a message to the hand off response message and then transmits to the first mobile communication system. In the sixth step, the first communication system commands hand off to the mobile station. In the seventh step, the mobile station(501) transmits the hand off finish message to the first mobile communication system and performs transmission/reception of signal to the first and second mobile communication systems.