| 摘要 |
A method for call establishment in a cellular radio system comprising a mobile services switching centre (MSC) and a private branch exchange (PBX) connected thereto, and a visitor location register (VLR) for storing subscriber data on subscribers (CPP) located within the service area of the mobile services switching centre. To optimize call establishment, when the private branch exchange (PBX) receives a connection establishment request (101) from a subscriber (CPP) located within its service area, it checks whether the private branch exchange (PBX) is the home private branch exchange of the subscriber (CPP) 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 (202), activation of ciphering procedures (203) and assignment (201) of a temporary subscriber identity and only thereafter sends a connection establishment request (204) to the mobile services switching centre; if the first call-related message sent by the private branch exchange (PBX) to the mobile services switching centre (MSC) is a connection establishment request (204) instead of a service request (102), the mobile services switching centre initiates (205) connection establishment (115, 116, 117, 119, 120, 121, 122, 123) without an interrogation to the visitor location register.
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