Method for implementing wide area Centrex

A method for implementing Wide Area Centrex (WAC), wherein a corresponding relationship between long number and short number of the WAC users is set and saved, the method comprising:

• routing a call a calling user initiates to a soft-switch;
• receiving by the soft-switch call information the calling user initiates and determining that the calling user is a WAC user by analyzing and recognizing a calling number;
• determining a route by the soft-switch to a called WAC user based on the call information and completing the call;
• wherein the WAC is implemented by trunk equipment, when said calling user is a Public Switched Telephone Network (PSTN) or Public Land Mobile Network (PLMN) user;
• and
• the step of routing the call the calling user initiates to the soft-switch comprises:
• the PSTN or PLMN user dialing an out-group prefix of the WAC or a long number of the called user, and a Local Switch (LS) to which the PSTN or PLMN user belongs routing the call to the soft-switch;
• the step of the soft-switch receiving the call information the calling user sends comprises:
• the soft-switch receiving the out-group prefix or the called long number that the LS sends;
• the step of determining the route by the soft-switch to the called user and completing the call comprises:
• the soft-switch obtaining the data of the Centrex according to the calling number, starting its own analysis of Centex numbers to determine that the call is an out-group call, and starting the procedure for handling an out-group call in IP Centrex service;
• wherein the WAC implemented by means of trunk equipment refers to routing the call the calling user initiates by the LS to which the PSTN or PLMN user belongs to the soft-switch by means of the trunk equipment.