Method for synchronizing a start value for security in a wireless communications network

A method for synchronizing a hyperframe number (HFN) between peer radio bearers (RBs) respectively supported by a user equipment (UE) and a Universal Terrestrial Radio Access Network (UTRAN), the peer RBs created by a Radio Bearer Setup procedure performed in conjunction with a Serving Radio Network Subsystem (SRNS) relocation procedure, the method comprising:

• sending a Radio Bearer Setup message from the UTRAN to the UE, the Radio Bearer Setup message indicating that SRNS relocation is to be performed and that a new RB is to be established in a first domain;
• in response to the Radio Bearer Setup message, the UE assigning a first START value to a START_VALUE_TO_TRANSMIT variable according to the HFNs of all established RBs in the first domain;
• the UE utilizing the START_VALUE_TO_TRANSMIT variable to set an HFN of the new RB;
• in response to the Radio Bearer Setup message, the UE generating a START list containing a plurality of entries corresponding to a plurality of domains, the plurality of domains including the first domain;
• the UE filling the entries with corresponding START values, wherein the UE synchronizes the entry corresponding to the first domain to hold a value that is identical to the value of the START_VALUE_TO_TRANSMIT variable;
• in response to the Radio Bearer Setup message, the UE composing a reply message, the reply message including the START list;
• and
• the UE sending the reply message to the UTRAN.