Method for On-Line Recovery of Parameter Synchronization for Ciphering Applications

A method for restoring hyper frame number, called HFN hereafter, synchronization in a wireless communications system, the method comprising the following steps:

• (a) adopting an initial HFN at a commencement of a ciphering session;
• and
• (b) detecting HFN un-synchronization between a plurality of stations of the wireless communications system during the ciphering session (802, 902);
• characterized by the steps of:
• (c) adjusting a current HFN of a station of the wireless communications system to derive an adjusted HFN (805, 905);
• and
• (d) adopting the adjusted HFN for subsequent operations of the ciphering session.

A method for ensuring hyper frame number, called HFN hereafter, synchronization in a receiving station of a wireless communications system, the method comprising:

• adopting an initial HFN at a commencement of a ciphering session;
• and
• detecting an irregularity in sequence number values;
• characterized by the step of:
• discarding a received protocol data unit (93) if the received protocol data unit (93) has an sequence number that is out of sequence according to a preceding PDU (92) and a following PDU (94).

A method for restoring hyper frame number, called HFN hereafter, synchronization in a receiving station of a wireless communications system, the method comprising the following steps:

• (a) adopting an initial HFN that is shared with a transmitting station at a commencement of a ciphering session;
• and
• (b) detecting HFN un-synchronization at a receiving station during the ciphering session (802, 902);
• characterized by the steps of:
• (c) adjusting a current HFN of the receiving station to derive an adjusted HFN (805, 905);
• and
• (d) adopting the adjusted HFN at the receiving station for subsequent operations of the ciphering session.

A method for restoring hyper frame number, called HFN hereafter, synchronization in a receiving station of a wireless communications system, the method comprising:

• (a) adopting an initial HFN that is shared with a transmitting station at a commencement of a ciphering session;
• characterized by the steps of:
• (b) detecting HFN un-synchronization at a receiving station during the ciphering session (802, 902) by detecting a symptom of an illegal state of a length indicator of a PDU, or by detecting a symptom of an unmatched predefined padding pattern of a PDU;
• (c) incrementing a current HFN value by one to derive an adjusted HFN (805, 905);
• (d) adopting the adjusted HFN at the receiving station for subsequent operations of the ciphering session;
• and
• (e) prohibiting HFN adjustment for a predetermined period of time commencing after a PDU is received, wherein the predetermined period of time is no shorter than a time required to transmit SN space number of PDUs, and the PDU contains a length indicator and no HFN un-synchronization is detected when the PDU is deciphered using the current HFN.