Method and mobile communication system capable of establishing peer-to-peer transmission

A mobile communication system being a universal mobile telecommunication system, comprising:

• a network;
• a plurality of mobile stations;
• and
• a server device, for storing an Internet Protocol (IP) address and device information of the plurality of mobile stations;
• wherein a first mobile station of the plurality of mobile stations requests the network for a first IP address via a first packet data protocol (PDP) context activation procedure, and transmits a message to the network to indicate to the second mobile station to trigger a peer-to-peer (P2P) transmission when the first mobile station starts to establish the P2P transmission with the second mobile station;
• the network transmits the message received from the first mobile station to the second mobile station;
• the second mobile station requests the network for a second IP address via a second PDP context activation procedure according to the message received from the network, and the second IP address is available to a third mobile station before the second mobile station acquires the second IP address in order to save network resources;
• the first mobile station and the second mobile station updates receiving statuses of the first IP address and the second IP address to the server device according to reception of the first IP address and the second IP address;
• and the server device actively transmits information of the second IP address to the first mobile station after the receiving statuses updated by the first mobile station and the second mobile station indicates that the first mobile station has obtained the first IP address and the second mobile station has obtained the second IP address, to allow the first mobile station to establish the P2P transmission with the second mobile station accordingly.