Communication system and communication controlling method

Abstract

A communication method in LIPA/SIPTO architecture is provided which, when a user equipment (UE) is to connect from a serving area to an external network, allows re-selection of an optimal gateway. The communication method allows selecting a gateway apparatus physically or topologically close to a site, where the user equipment is attached.

1 . A communication method in Selected IP Traffic Offload (SIPTO) architecture, the method comprising:
 a mobility management entity (MME) sending a first signal for setting re-attachment to a user equipment, when the MME decides that it is necessary to re-select a gateway apparatus;   the user equipment, on receipt of the first signal, transmitting a second signal for re-attachment to the MME; and   the MME receiving a delete session request from the gateway apparatus and performing re-selection of a gateway apparatus.   
     
     
         2 . The communication method according to  claim 1 , wherein the gateway apparatus includes a serving gateway apparatus. 
     
     
         3 . A communication system in Selected IP Traffic Offload (SIPTO) architecture, the system comprising:
 a mobility management entity (MME) that sends a first signal for setting re-attachment, when the MME decides that it is necessary to re-select a gateway apparatus;   a user equipment that, on receipt of the first signal, transmits a second signal for re-attachment to the MME; and   a plurality of gateway apparatuses, re-allocation thereof controlled by the MME,   the MME receiving a session delete request from the gateway apparatus and performing re-selection of a gateway apparatus.   
     
     
         4 . The communication system according to  claim 3 , wherein the gateway apparatus includes a serving gateway apparatus. 
     
     
         5 . A user equipment in a communication system by Selected IP Traffic Offload (SIPTO) architecture, wherein the user equipment receives a first signal that sets re-attachment from a mobility management entity (MME) and transmits a second signal for re-attachment to the MME, which receives a delete session response from a gateway apparatus, to cause the MME to perform re-selection of a gateway apparatus.