Reducing occurrence of user equipment registration expiry during calls

A communication system, the system comprising:

• an Internet Protocol (IP) Multimedia Subsystem (IMS) network;
• and
• User Equipment (UE) for communicating with the IMS network, for registering with the IMS network for a registration period, for comparing a duration of a remaining portion of the registration period at a particular time with a re-registration threshold time period, and for attempting to re-register 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 at least one of the UE and the IMS network determines said re-registration threshold time period, and
• further wherein said re-registration threshold time period is at least one of set to a value greater than 600 seconds, determined independently of a length of a registration period, and determined according to one or more of:
• a remaining talk time of the UE at said particular time,
• a state of the UE at said particular time,
• a duration of at least one previous call made by the UE,
• a statistical parameter of a plurality of calls made by the UE,
• a statistical parameter of a plurality of calls made by at least one UE, and
• a predefined maximum call duration.

User Equipment (UE) for communicating with an Internet Protocol (IP) Multimedia Subsystem (IMS) network, wherein the UE is adapted to:

• register with the IMS network for a registration period;
• determine a re-registration threshold time period;
• compare a duration of a remaining portion of the registration period at a particular time with the re-registration threshold time period;
• and
• attempt to re-register 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, and
• wherein said re-registration threshold time period is at least one of set to a value greater than 600 seconds, determined independently of a length of a registration period, and determined according to one or more of:
• a remaining talk time of the UE at said particular time,
• a state of the UE at said particular time,
• a duration of at least one previous call made by the UE,
• a statistical parameter of a plurality of calls made by the UE,
• a statistical parameter of a plurality of calls made by at least one UE, and
• a predefined maximum call duration.

A method for reducing the occurrence of User Equipment (UE) registration expiry during calls from the UE, the method comprising:

• registering a UE with a 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 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.