Puhelunmuodostusmenetelmä

PCT No. PCT/FI94/00266 Sec. 371 Date Dec. 22, 1995 Sec. 102(e) Date Dec. 22, 1995 PCT Filed Jun. 16, 1994 PCT Pub. No. WO95/01075 PCT Pub. Date Jan. 5, 1995A method for call establishment in a cellular radio system including a mobile services switching center and a private branch exchange connected thereto, and a visitor location register for storing subscriber data on subscribers located within the service area of the mobile services switching center. To optimize call establishment, when the private branch exchange receives a connection establishment request from a subscriber located within its service area, the private branch exchange checks whether the private branch exchange is the home private branch exchange of the subscriber that sent the connection establishment request. If the private branch exchange is the home private branch exchange of the subscriber, the private branch exchange performs independently authentication, activation of ciphering procedures and assignment of a temporary subscriber identity and only thereafter sends a connection establishment request to the mobile services switching center. If the first call-related message sent by the private branch exchange to the mobile services switching center is a connection establishment request instead of a service request, the mobile services switching center initiates connection establishment without an interrogation to the visitor location register.