UMTS call handling methods and apparatus
View Patent ↗Methods and apparatus for transparently switching a local instance of a UMTS protocol-based call from a first card or module of a media gateway to a second card or module of the media gateway, such that the remote end of the call is not aware that the call has been switched between the first and second cards or modules. Moreover, initially establishing call media flow may include implementing two timers of different duration during which call-initialization is retried if no Positive-Acknowledgement of call initialization is received, where a shorter-duration timer is relied upon to attempt retries if a Negative-Acknowledgement is received, and a longer-duration timer is relied upon to attempt retries if neither a Positive-Acknowledgement nor a Negative-Acknowledgement is received.
1. A method of establishing media flow for a universal mobile telecommunications service (UMTS) call between a local call instance and a remote call instance, the method comprising:
transmitting an initialization message from the local call instance to the remote call instance;
at the local call instance, starting, substantially simultaneously, a negative-acknowledgement timer and a no-acknowledgement timer, wherein the negative-acknowledgement timer is configured to expire after a first predetermined duration, the no-acknowledgement timer is configured to expire after a second predetermined duration, and the second predetermined duration is substantially longer than the first predetermined duration; and
re-transmitting the initialization message from the local call instance to the remote call instance until the earliest of:
receipt of positive-acknowledgement the remote call instance;
expiration of the negative-acknowledgement timer at the local call instance if negative-acknowledgement is received from the remote call instance; and
expiration of the no-acknowledgement timer at the local call instance if neither the positive-acknowledgement nor the negative-acknowledgement is received from the remote call instance, wherein the local call instance resides on a local media gateway and the remote call instance resides on a remote radio network controller (RNC); the method further comprising: stopping the negative-acknowledgement and no-acknowledgement timers when the positive-acknowledgement is received from the remote call instance; and stopping the no-acknowledgement timer when the negative-acknowledgement is received from the remote call instance.
2. The method of claim 1 wherein re-transmitting the initialization message includes re-transmitting the initialization message at periodic time intervals.
3. A media gateway apparatus configured to support media flow of a universal mobile telecommunications service (UMTS) call between a local call instance and a remote call instance, comprising:
a negative-acknowledgement timer implemented at the local call instance and being active for a first predetermined duration commencing substantially simultaneously with initial transmission of an initialization message from the local call instance to the remote call instance;
a no-acknowledgement timer implemented at the local call instance and being active for a second predetermined duration commencing substantially simultaneously with the initial transmission of the initialization message, wherein the second predetermined duration is substantially greater than the first predetermined duration; and
means for re-transmitting the initialization message from the local call instance to the remote call instance until the earliest of:
receipt of positive-acknowledgement from the remote call instance;
expiration of the negative-acknowledgement timer at the local call instance if negative-acknowledgement is received from the remote call instance; and
expiration of the no-acknowledgement timer at the local call instance if neither the positive-acknowledgement nor the negative-acknowledgement is received from the remote call instance, wherein the local call instance resides on the media gateway apparatus and the remote call instance resides on a remote radio network controller (RNC); wherein the negative-acknowledgement and no-acknowledgement timers are configured to be stopped upon receipt of the positive acknowledgement from the remote call instance prior to termination of either the first or second predetermined durations, and wherein the no-acknowledgement timer is configured to be stopped upon receipt of the negative-acknowledgement from the remote call instance prior to termination of the first predetermined duration.
4. The media gateway apparatus of claim 3 wherein the initialization message retransmitting means is configured to stop re-transmitting the initialization message if neither the positive-acknowledgement, the negative-acknowledgement, nor no-acknowledgement is received upon expiration of the negative-acknowledgement and no-acknowledgement timers.