Patent ID: 8509148

Claim:
A method for application layer gateway (ALG) assisted local IP access (LIPA) at a base station by network address translation (NAT), applicable to a system having an IP multimedia subsystem (IMS), an originating entity, a terminating entity and a local network having an ALG and a Home eNode B (HeNB) having a NAT/Router/DHCP-Client module, said method comprising: said IMS identifying a request from said originating entity for using LIPA, facilitated by NAT, to determine whether said originating entity is allowed to use LIPA, and if not, stopping said method; when said terminating entity is in same local network as said originating entity, said IMS relaying that information of said originating and terminating entities residing in said same local network to said ALG, and said ALG changing transport address information (TAI) in said request response and TAI in an ACK message to a local TAI; when in case of a handover situation, said ALG changing the TAI from said local TAI back to an original TAI; and said IMS informing said originating entity that said terminating entity not being in the same local network and regular charging being applied or notifying to said originating entity to determine whether to proceed with a call setup when said terminating entity not residing in the same local network.