Patent ID: 8144659

Claim:
A handover processing method performed by a first gateway connected to a PSTN, an IP network, and a mobile communications network including a base station arranged to receive a communication source call from a mobile terminal in the mobile communications network, in which the communication source code is retrieved in the IP network without use of the PSTN, the method comprising: receiving at the first gateway, from the base station, a communication request relating to the communication source call, which communication source call is either a voice over Internet (VoIP) or a line exchange type and determining whether the communication request is a handover call, and a1) on determination that the communication request is not a handover call, performing at the first gateway, without use of the PSTN, either a line exchange connection through the PSTN or a VoIP connection through the IP network depending upon the type of the communication source call; or a2) on determination that the communication source call is a handover call, determining, without use of the PSTN, whether the first gateway is managing the communication source call, and b1) on determination that the first gateway is managing the communication source call, retrieving the communication source call from the first gateway wholly within the IP network and performing at the first gateway, without use of the PSTN, handover through the PSTN or the IP network depending upon the type of the communication source call, the handover being performed by the gateway itself; or b2) on determination that the first gateway is not managing the communication source call, determining, without use of the PSTN, whether the communication source call is being managed by another gateway connected to the gateway via the IP network, and c1) on determination that the communication source call is not being managed by the other gateway, performing at the first gateway, without use of the PSTN, handover itself through the PSTN; or c2) on determination that the other gateway is managing the communication source call, retrieving the communication source call from the other gateway wholly within the IP network and performing handover at the first gateway without use of the PSTN and through the IP network by taking over management of the communication source call from the other gateway.