Link Failure Detection and Interworking System Relocation in Circuit Switched Fallback

摘要

Detect failure of an S102 link (118, 119) between an Evolved Packet Core, EPC, network (72) based Mobility Management Entity, MME, (112) and an Interworking System, IWS, (114, 115) in a Mobile Switching Center, MSC, pool (116) deploying Circuit Switched Fallback, CSFB, for the EPC network. A heartbeat (keep alive or echo) message exchange between an MME-IWS pair augments the current standards to provide a simple and direct method to monitor the application layer status of the S102 link (UDP based) between the EPC-based MME and the MSC pool-based IWS. Upon detecting a link failure, message flows can be quickly re-routed to another S102 link or MSC (i.e. MME is updated). Reverse use of an A21 Event Notification message from an IWS to MME, or a re-assigned IWS's delayed acknowledgement of an initial call-related message from an MME also augment the current standards to address IWS relocation related message-bouncing in MSC pool-based deployments of CSFB, thereby allowing efficient routing of messages.