ISDN communications controller

• US 6,243,390 B1
• Filed: 03/12/1997
• Issued: 06/05/2001
• Est. Priority Date: 03/12/1996
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Smith, Jr., Robert Lynn
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US08/820,332
• Time in Patent Office: 1,546 Days
• Field of Search: 370/410, 370/522, 370/524, 370/420, 370/421, 370/433, 370/434, 370/437, 370/465
• US Class Current: 370/437
• CPC Class Codes: H04Q 11/0457 Connection protocols

Abstract

A communications controller for interfacing multiple analog telephone terminals to an integrated services digital network (ISDN) line connected to a telecommunications network, the ISDN line having two bearer (B) channels and a data (D) channel. The controller comprises an ISDN interface providing a physical bi-directional interface to the two B-channels and the D-channel of the ISDN line. A base logic processor, and D-channel protocols process supports a Q.931 protocol with a central office of the telecommunications network and an X.25-based protocol with a remote device, via the ISDN interface and D-channel over which command and response packets to and from the base logic processor with the central office or the remote device are transmitted. Multiple analog interfaces are adapted to support respective telephone terminals for passing bi-directional analog voice signals. Selectable coders/decoders (CODECs), connected to respective analog interfaces, encode the analog voice signals to digital pulse code modulation (PCM) or adaptive differential PCM (ADPCM) and decode PCM or ADPCM to analog, as selected by the base logic processor. A bandwidth controller connects, via the ISDN interface, the encoded voice signals to or from the selectable CODECs with communication subchannels allocated among bandwidth of the B-channels, as directed by the base logic processor, forwarding precisely timed bandwidth availability. The communications controller supports up to five telephone connections concurrently through the telecommunications network.

Claims

1. In a system having a plurality of devices coupled to a first communications controller which is connected to an integrated services digital network (ISDN) line of a telecommunications network through which a call connection is established with a second communications controller, the ISDN line having two bearer channels of predetermined bandwidth and a data channel, a method of interfacing the devices to the ISDN line for concurrent communications over the call connection with the second controller, the method comprising:

negotiating, on the data channel, between the first and second communications controllers appropriation of one or more subchannels from the bandwidth of the two bearer channels; and

allocating the one or more subchannels to respective devices of the plurality of devices, wherein the subchannels are allocated bits from one or more of the bearer channels so as to allow at least five devices to be allocated different call connections from the two bearer channels, and wherein each of the devices thereby connects through at least one of the two bearer channels to a different device.

2. A method as claimed in claim 1, wherein the step of negotiating the appropriation of a subchannel includes:

one controller of the first and second communication controllers sending a request for the subchannel to the other controller, wherein the request specifies bandwidth for the subchannel;

the other controller transmitting an accession message and, after a specific period upon close of the accession message, effecting the bandwidth changeover in the full channel transmission of the other controller towards the one controller; and

the one controller transmitting an acknowledgement message and, after the specific period upon close of the acknowledgement message, effecting the bandwidth changeover in the full channel transmission of the one controller towards the other controller.

3. A method as claimed in claim 2, wherein the specific period is a predetermined time interval following the close of the accession message or the acknowledgement message.

4. A method as claimed in claim 3, wherein the specific period is immediately following the close of the accession message or the acknowledgement message.

5. A method as claimed in claim 1, wherein the plurality of devices include telephones;

and each subchannel allocated to the individual telephones, as a voice subchannel, comprises 24 Kbps bandwidth for a digital voice signal.

6. A method as claimed in claim 5, wherein the digital voice signal is encoded in three bit adaptive differential pulse code modulation (ADPCM).

7. A method as claimed in claim 6, wherein the plurality of devices includes at least one data processing device and the subchannel allocated to the at least one data processing device, as a data subchannel, comprises available bandwidth of the two bearer channels not allocated to the telephones.

8. A method as claimed in claim 7, wherein the predetermined bandwidth of the two bearer channels is 128 Kbps, which supports a maximum of five 24 Kbps voice subchannels and a minimum of 8 Kbps for the data subchannel.

9. A method as claimed in claim 8, wherein the telephones are analog telephones and further comprising, for each analog telephone having been allocated a voice subchannel:

encoding an outgoing analog voice signal from the analog telephone into an outgoing ADPCM digital voice signal which is transmitted over the voice subchannel allocated thereto; and

decoding an incoming ADPCM signal received from that voice subchannel into an incoming analog voice signal which is passed to the analog telephone.

10. A method as claimed in claim 1, further comprising sharing the predetermined bandwidth of the two bearer channels with a data device and allocating the data device at least one bit, such that the data device shares the predetermined bandwidth with up to five different call connections.

11. A method as claimed in claim 10, further comprising deallocating bandwidth that has been allocated to the data device and allocating it to a new call connection that is established.

12. A method as claimed in claim 10, further comprising allocating bandwidth from a terminated call connection to the data device to increase the bandwidth allocated to the data device.

13. A method as claimed in claim 1, wherein allocating the one or more subchannels to respective devices of the plurality of devices comprises allocating at least one bit from each of the two bearer channels to at least one of the respective devices, such that the at least one respective device is allocated bandwidth from both of the bearer channels.

14. A method as claimed in claim 1, wherein allocating the one or more subchannels to respective devices of the plurality of devices comprises allocating three bits, from one or more of the two bearer channels, to each of the respective devices.

15. A method as claimed in claim 1, further comprising communicating between the first communications controller and a line interface unit using a frame format which comprises a separate control channel and a separate data channel for each of the plurality of devices, wherein the line interface unit is disposed between the plurality of devices and the first communications controller.

16. An apparatus for interfacing a plurality of analog telephone terminals to an integrated services digital network (ISDN) line connected to a telecommunications network, the ISDN line having two bearer (B) channels and a data (D) channel, the apparatus comprising:

base logic;

an ISDN interface providing a physical bi-directional interface to the two B-channels and the D-channel of the ISDN line;

D-channel protocol means supporting communications with a central office of the telecommunications network and with a remote device, via the ISDN interface and D-channel over which command and response packets to and from the base logic with the central office or the remote device are transmitted;

a plurality of analog interfaces adapted to support respective telephone terminals for passing bi-directional analog voice signals;

a plurality of selectable coders/decoders (CODECs), connected to respective analog interfaces, for encoding the analog voice signals to digital pulse code modulation (PCM) or adaptive differential PCM (ADPCM) and decoding PCM or ADPCM to analog, as selected by the base logic; and

bandwidth control adapted to connect, via the ISDN interface, the encoded voice signals to or from the selectable CODECs with communication subchannels allocated among bandwidth of the B-channels, as directed by the base logic, synchronized to the bit level between controllers, wherein the communication subchannels are allocated bits from one or more of the B-channels, so as to allow at least five analog telephone terminals to be allocated different call connections from the two B-channels, and wherein each of the analog telephone terminals thereby connects through at least one of the two B-channels to a different device.

17. An apparatus as claimed in claim 16, wherein the D-channel protocol means supports a Q.931 protocol by which the apparatus communicates with the central office.

18. An apparatus as claimed in claim 17, wherein the D-channel protocol means supports an X.25-based protocol by which the apparatus communicates with the remote device.