Abstract: A method for implementing communication services includes: after receiving a call request, determining whether a user subscribes to an IP Centrex service and an intelligent network (IN) service according to the obtained subscription information of the user; if the user subscribes to the IP Centrex service and IN service, checking with an application server (AS) whether the call request is for an intra-group call; if the call request is for an intra-group call, performing corresponding service processing according to the checking result to implement discount charging on the intra-group call. By using the method of the present invention, if the user subscribes to the IP Centrex service and the IN service, no conflict occurs between the IP Centrex service and the IN service, and discount charging is implemented on the intra-group call. A network device and a mobile communication system are also provided.

Abstract: The present invention relates to communication technologies, and discloses a method, an apparatus, and a system for transmitting a signal to ensure normal communication between the calling party and the called party. The method includes: A first node sends Global Text Telephone (GTT) signal encoded in a Cellular Text Telephone Modem (CTM) format to a second node after the first node receives the GTT signal and if transmission between the first node and the second node is based on an Internet Protocol (IP) network. The present invention is primarily applicable to the GTT service.

Abstract: The present invention relates to communication technologies, and discloses a method, an apparatus, and a system for transmitting a signal to ensure normal communication between the calling party and the called party. The method includes: A first node sends Global Text Telephone (GTT) signal encoded in a Cellular Text Telephone Modem (CTM) format to a second node after the first node receives the GTT signal and if transmission between the first node and the second node is based on an Internet Protocol (IP) network. The present invention is primarily applicable to the GTT service.

Abstract: A method for implementing communication services includes: after receiving a call request, determining whether a user subscribes to an IP Centrex service and an intelligent network (IN) service according to the obtained subscription information of the user; if the user subscribes to the IP Centrex service and IN service, checking with an application server (AS) whether the call request is for an intra-group call; if the call request is for an intra-group call, performing corresponding service processing according to the checking result to implement discount charging on the intra-group call. By using the method of the present invention, if the user subscribes to the IP Centrex service and the IN service, no conflict occurs between the IP Centrex service and the IN service, and discount charging is implemented on the intra-group call. A network device and a mobile communication system are also provided.