Virtual wide area centrex

• US 5,892,821 A
• Filed: 12/13/1996
• Issued: 04/06/1999
• Est. Priority Date: 06/02/1995
• Status: Expired due to Term

• Current Assignee: Bell Sygma, Inc. (BCE Incorporated)
• Original Assignee: Bell Sygma, Inc. (BCE Incorporated)
• Inventors: Turner, George W.
• Primary Examiner(s): Wolinsky, Scott
• Application Number:
  US08/766,277
• Time in Patent Office: 844 Days
• Field of Search: 379/201, 379/207, 379/219, 379/220, 379/221, 379/229, 379/230, 379/211, 379/234
• US Class Current: 379/221.08
• CPC Class Codes: H04M 2207/45 public-private interworking, e.g. centrex
• CPC Class Codes: H04M 3/42314 in private branch exchanges
• CPC Class Codes: H04M 7/009 in systems involving PBX or KTS networks
• CPC Class Codes: H04Q 2213/13091 CLI, identification of calling line
• CPC Class Codes: H04Q 2213/13097 Numbering, addressing
• CPC Class Codes: H04Q 2213/13102 Common translator
• CPC Class Codes: H04Q 2213/13103 Memory
• CPC Class Codes: H04Q 2213/13176 Common channel signaling, CCS7
• CPC Class Codes: H04Q 2213/13222 PBX circuits in public exchange, centrex
• CPC Class Codes: H04Q 2213/13345 Intelligent networks, SCP
• CPC Class Codes: H04Q 2213/13399 Virtual channel/circuits
• CPC Class Codes: H04Q 3/58 Arrangements providing connection between main exchange and sub-exchange or satellite

Abstract

A method is disclosed which brings together a combination of special IN features and techniques to allow Centrex stations supported by a plurality of central office switching systems, each at different locations, to function from the customer'"'"'s perspective as though they were served by a single central office switch. The key to Virtual Wide Area Centrex is a total separation of the telephone numbers seen and used by customers (Customer Number Address--CNA) from the telephone numbers used internally by the network for call routing purposes (Network Node Address--NNA), such that there are two separate and distinct numbering plan domains. A central database, interconnected with each of the Centrex switches, maintains the mapping between CNA and NNA. This database is called upon, as required, to do both forward and reverse translations--i.e., from CNAs to NNA and vice-versa. The net result is that CNAs identify people (e.g., a customer'"'"'s specific employees and agents) whereas NNAs identify locations (e.g., offices and conference rooms). This permits an environment in which individuals may move from one physical location to another, regardless of the serving central office switch, while keeping their CNA and their network access privileges.

Claims

1. A method of configuring a telephone network for providing Wide Area Centrex services to a number of customer sites having a plurality of telephone network devices, said telephone network having a number of telephone switching offices equipped with SSPs (Service Switching Points) operating with AIN (Advanced Intelligent Network) application software for providing Centrex functionality to said telephone network devices at said customer sites, comprising the steps of:

a) assigning, as a switch resident datafill, a network node address (NNA) to each telephone network device used at said customer sites requiring Centrex functionality;

b) assigning a customer network address (CNA) to each of said telephone network devices, each assigned CNA having a corresponding NNA;

c) assigning, as a switch resident datafill, a Business Group ID (BGID) to each of said telephone network devices to enable a Centrex subscriber using said telephone network device to reach another telephone network device in one of said customer sites using abbreviated dialing of said CNA; and

d) providing, to each of said SSPs, access to a number translation database table to provide when requested by said SSPs a translation of a CNA to a corresponding NNA and of a NNA to a corresponding CNA when Centrex and Public Switched Telephone Network (PSTN) calls are received and initiated from and to one of said telephone network devices.

2. A method as defined in claim 1, wherein each number dialed for all originating calls, whether dialed by a Centrex subscriber or received from the PSTN, is treated as a CNA.

3. A method as defined in claim 1, wherein the BGID plus the dialed abbreviated CNA are translated at said number translation table into an NNA to determine how to route a call to a telephone network device at any one of the customer sites served by the Centrex type services.

4. A method as defined in claim 3, wherein an originating switch-supplied Centrex Calling Line ID (CLID) is translated at said number translation table, from an NNA to a CNA prior to authorizing the switch to execute call completion, either to an internal Centrex station or to the PSTN.

5. A method as defined in claim 4, wherein an AIN trigger datafill is assigned, as switch-resident datafill, such that at least some Centrex related calls generate queries to said number translation table if certain criteria are met.

6. A method as defined in claim 5, wherein a conversion flag is set on the call after a called number translation, at the SSP that launched the query to indicate that the called number has been converted from a CNA to an NNA.

7. A method as defined in claim 6, wherein said conversion flag is used at a terminating switch to ensure that no call can be terminated at a Centrex station unless the called number has been converted to an NNA.

8. A method as defined in claim 1, wherein said number translation table is located at a remotely located Service Control Point (SCP).

9. A method as defined in claim 8, wherein incoming calls from the PSTN having a CNA are routed to any one of said telephone network devices by:

receiving at an SSP associated with said CNA a call having a number of digits sent from a calling station;

identifying said call by a combination of the digits sent and the absence of an indicator signifying prior translation of said digits;

formulating a Transaction Capabilities Application Part (TCAP) query message appropriate to an AIN trigger used, containing the received digits;

transmitting the query message from the SSP of the first customer site to said remotely located SCP via a common channel transport facility;

pre-translating at the SCP the received digits into a set of digits that can be used to route the call to any one of said customer sites served by SSPs; and

formulating a TCAP response message at the SCP containing the routing number associated with said CNA.

10. A method is defined in claim 9, wherein calls are determined to be directed to the PSTN if the dialed digits are preceded by an escape code.

11. A method as defined in claim 8, wherein a Centrex type call from a telephone network device of a first customer site to a telephone network device of a second customer site is routed by:

receiving at the SSP of the first customer site the digits sent from the calling telephone network device;

upon receipt of all digits, formulating a Transactions Capabilities Application Part (TCAP) query message appropriate to an AIN trigger used, containing the called number;

transmitting the query message from the SSP of the first customer site to the remotely located SCP via a common channel transport facility;

determining at the SCP if a valid user has been assigned to the calling telephone network device;

determining if the digits sent from the calling station indicate a PSTN or Centrex type call by the presence or absence of an escape code;

pre-translating at the SCP the called number to determine how to route the call to any one of said customer sites served with Centrex type services; and

formulating a TCAP response message at the SCP containing the routing number associated with said CNA.

12. A method of providing Wide Area Centrex services to a number of customer sites having a plurality of telephone network devices, said telephone network having a number of telephone switching offices equipped with SSPs (Service Switching Points) operating with AIN (Advanced Intelligent Network) application software for providing Centrex functionality to said telephone network devices at said customer sites, comprising the steps of:

a) assigning, as a switch resident datafill, a network node address (NNA) to each telephone network device used at said customer sites requiring Centrex functionality;

b) assigning a customer network address (CNA) to each of said telephone network devices, each assigned CNA having a corresponding NNA;

c) assigning, as a switch resident datafill, a Business Group ID (BGID) to each of said telephone network devices to enable a Centrex subscriber using said telephone network device to reach another telephone network device in one of said customer sites using abbreviated dialing of said CNA;

d) providing, to each of said SSPs, access to a number translation database table to provide when requested by said SSPs a translation of a CNA to a corresponding NNA and of a NNA to a corresponding CNA;

e) receiving at an SSP of a first customer site a call having a number of digits sent from a calling station;

f) identifying from the dialed digits an internal Centrex call and formulating a Transaction Capabilities Application Part (TCAP) query message appropriate to the AIN trigger used, containing the received digits;

g) transmitting the TCAP message from the SSP of the first customer site to a remotely located SCP, containing said number translation table, via a common transport facility;

h) pre-translating at the SCP the called number to determine how to route the call to any one of the said customer sites served with Centrex type services;

i) formulating a TCAP response message at the SCP containing the NNA associated with said CNA;

j) transmitting the formulated message to the SSP of the first customer site to instruct the telephone network how to complete the call; and

k) translating the switch-supplied NNA of the calling station to a CNA such that Centrex type terminating station features can be maintained at each customer site.

13. A method as defined in claim 12, further comprising the steps of:

determining if the digits sent from the calling telephone network device are indicative of a Centrex type call or a Public Switched Telephone Network (PSTN) type call; and

if the digits sent are indicative of a Centrex call, identifying an SCP process from the identity of the SSP'"'"'s AIN trigger.

14. A method is defined in claim 13, wherein calls are determined to be directed to the PSTN if the dialed digits are preceded by an escape code.

15. A telephone network for providing Wide Area Centrex services, having a plurality of Centrex switching offices equipped with Service Switching Points (SSPs) operating with Advanced Intelligent Network (AIN) application software, said network having a switching office for providing Centrex functionality to a number of customer sites, each served by separate switching offices, comprising:

a Service Control Point (SCP) connected to each switching office and having a number translation database containing customer network addresses (CNAs) that have been assigned to each telephone device used at the customer sites;

each SSP of a customer site being adapted to receive a number of digits sent from a calling station;

means for identifying, at the SSP, the criteria necessary to trigger a query to the SCP;

means for formulating a Transaction Capabilities Application Part (TCAP) query message appropriate to the AIN trigger used;

means for transmitting a Signalling System 7 (SS7) message from the SSP to the SCP via a common transport facility;

means for pre-translating at the SCP the received message to determine a routing number to route the call to any one of said customer sites served with Centrex type services;

means for formulating a TCAP response message at the SCP containing the routing number;

means for transmitting the formulated message to the SSP of the customer site to instruct the telephone network how to complete the call; and

means for translating the switch-supplied network node address (NNA) of the calling station to a CNA such that Centrex type terminating station features can be maintained at each customer site.

16. A network as defined in claim 15, further comprising:

means for determining if the digits sent from the calling station are indicative of a Centrex type call or a Public Switched Telephone Network (PSTN) type call, and if the digits sent are indicative of a Centrex call, identifying an SCP process from the identity of the SSP'"'"'s AIN trigger.