Patent ID: 8165582

Claim:
A method for reducing the occurrence of User Equipment (UE) Internet Protocol (IP) Multimedia Subsystem (IMS) registration expiry, the method comprising: registering a UE with an IMS network for a registration period; determining a re-registration threshold time period; comparing a duration of a remaining portion of the registration period at a particular time with the re-registration threshold time period; and attempting to re-register the UE with the IMS network for a further registration period if said remaining portion is less than or equal to said re-registration threshold time period, wherein the determining of said re-registration threshold time period comprises at least one of: setting said threshold time period to a value greater than 600 seconds; determining said threshold time period according to a remaining talk time of the UE at said particular time; determining said threshold time period according to a state of the UE at said particular time; determining said threshold time period according to a duration of at least one previous call made by the UE; determining said threshold time period according to a statistical parameter of a plurality of calls made by the UE; determining said threshold time period according to a statistical parameter of a plurality of calls made by at least one UE; determining said threshold time period according to a predefined maximum call duration; and determining said threshold time period independently of a length of the registration period.