Apparatus for maintaining continuous synchronous encryption and decryption in a wireless communication system throughout hand-off

PORTABLE AND FIXED COMMUNICATION UNITS (CUS) (120, 102) MAINTAIN A SYNCHRONIZED ENCRYPTION AND DECRYPTION OF INFORMATION WITHOUT INTERRUPTION THROUGHOUT A HAND-OFF IN A WIRELESS COMMUNICATION SYSTEM.THE CUS (120,102) COMPRISE ENCRYPTION SYNCHRONIZATION COUNTERS (ESCS) (414, 314) AND TIME-DIVISION MULTIPLE -ACCESS (TDMA) TRANSCEIVERS (402, 302) FOR SENDING AND RECEIVING A DIGITAL SIGNAL (201) HAVING A RECURRING SYNCHRONIZATION MARKER (204). THE CUS (120,102) MAINTAIN SYNCHRONIZED ENCRYPTION AND DECRYPTION BY TRANSFERRING A CONTINUATION VALUE (419, 320) AND A TIME (420, 318) OF HAND-OFF COMPLETION TO A FIXED CU (102) ABOUT TO RECEIVE A HAND-OFF, THE CONTINUATION VALUE COMPRISING A VALUE EXPECTED IN THE ESC (414) OF THE PORTABLE CU (120) BEING HANDED-OFF AT THE TIME (420, 318) OF HAND-OFF COMPLETION. THE ESCS (414, 314) THROUGHOUT THE SYSTEM MAINTAIN FRAME SYNCHRONIZATION THROUGH THE SYNCHRONIZATION MARKER (204) FROM THE FIXED CUS (120, 102). (FIG. 7)