Method for increasing ISDN channel capacity of TDM serial communication link for digital subscriber line channels

• US 5,771,236 A
• Filed: 09/10/1996
• Issued: 06/23/1998
• Est. Priority Date: 09/10/1996
• Status: Expired due to Term

• Current Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Original Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Inventors: Sansom, Michael Scott, Toth, Robert James
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US08/711,811
• Time in Patent Office: 651 Days
• Field of Search: 370/360, 370/384, 370/458, 370/465, 370/474, 370/476, 370/477, 370/522, 370/524, 370/535, 370/904, 370/916
• US Class Current: 370/458
• CPC Class Codes: H04J 3/12 Arrangements providing for calling or supervisory signals
• CPC Class Codes: H04J 3/1647 Subrate or multislot multiplexing
• CPC Class Codes: H04Q 11/0428 Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/13166 Fault prevention
• CPC Class Codes: H04Q 2213/13174 Data transmission, file transfer
• CPC Class Codes: H04Q 2213/13176 Common channel signaling, CCS7
• CPC Class Codes: H04Q 2213/13199 Modem, modulation
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/13216 Code signals, frame structure
• CPC Class Codes: H04Q 2213/13292 Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13367 Hierarchical multiplexing, add-drop multiplexing
• CPC Class Codes: H04Q 2213/13392 Channels assigned according to rules

Abstract

An overhead bit-usurping multiplexing/demultiplexing mechanism increases the overall effective ISDN channel-conveying capacity of a serial digital data communication link, and thereby enables a terminal site channel bank to provide ISDN service to an additional number of customer premises equipments, other than the eight DSL channels normally accommodated within the twenty-four time slots of a (T1) TDM frame. Each condensed TDM DSL channel contains first and second multibit B information signal time slots, a multibit D information signal time slot, and a maintenance bit. No other auxiliary bits of a standard TR-NWT-000397 mode D+ octet are included, so that the compressed content TDM DSL channels have a smaller number of bits per channel than the standard TR-NWT-000397 format. As a result, when controllably interleaved with one another, the total number of TDM DSL channels (e.g., ten DSL channels) is larger than the eight DSL channels that would normally be accommodated within the twenty-four time slots of the TDM link.

Claims

1. For use with a digital communication network having a serial communication link over which a multiplicity J of basic time division multiplexed (TDM) digital subscriber line (DSL) channels are normally conveyed within a plurality P of time division multiplexed time slots, each basic TDM DSL channel having first and second multibit bearer (B) information signal time slots and a multibit data (D) information signal time slot, said multibit (D) information signal time slot containing signalling information for said bearer (B) information signal time slots, a maintenance channel bit provided for each DSL channel, and a plurality of auxiliary overhead bits, said serial communication link being coupled to a multiple channel bank that is interfaced with a multiplicity M of integrated services digital network (ISDN) channels, a method of controlling the time division multiplexing of TDM DSL channels conveyed by said serial communication link so as to increase the number of TDM DSL channels that may be conveyed thereby and interfaced via said channel bank for an increased number of J+N ISDN channels within said P time slots, comprising the steps of:

(a) providing an additional number N of TDM DSL channels, each additional TDM DSL channel containing first and second multibit B information signal time slots, and a multibit D channel information signal time slot containing signalling information bits for said first and second B information signal time slots, and a maintenance channel bit; and

(b) combining first and second multibit B information signal time slots, D channel signalling information bits and the maintenance bits of said multiplicity J of basic TDM DSL channels with first and second multibit B information signal time slots, D channel signalling information bits and the maintenance channel bit of said additional number N of DSL channels into an increased number K of condensed TDM DSL channels, wherein K=J+N, that are contained within said plurality P of time division multiplexed time slots conveyed over said serial communication link.

2. A method according to claim 1, wherein step (b) comprises:

(b1) generating a plurality of multibit B information signal time slots, respectively associated with selected ones of said J basic TDM DSL channels and said N additional TDM DSL channels provided in step (a),

(b2) generating a first number of multibit D channel information signal time slots, each of which contains multiple pairs of first and second D channel bits carrying signalling information for B information time slots contained within said J basic TDM DSL channels;

(b3) generating a second number of multibit D channel information signal and maintenance information signal time slots, which contain N pairs of first and second D channel bits carrying signalling information for B information signal time slots contained within said N additional TDM DSL channels provided in step (a), and maintenance channel bits associated with said J basic TDM DSL channels and said additional number of N TDM DSL channels provided in step (a); and

(b4) combining said multibit B information signal time slots generated in step (b1), said first number of multibit D channel information signal time slots generated in step (b2), and said second number of multibit D channel information signal and maintenance information signal time slots generated in step (b3) into said plurality P of time division multiplexed time slots conveyed over said serial communication link.

3. For use with a digital communication network having a serial communication link, which normally conveys thereover a multiplicity J of basic time division multiplexed (TDM) digital subscriber line (DSL) channels, each basic TDM DSL channel containing first and second multibit bearer (B) information signal time slots and a multibit data (D) information signal time slot, said multibit D information time slot containing signalling information for said B information time slots, a maintenance channel bit and a plurality of auxiliary overhead bits, said serial communication link being coupled to a multiple channel bank, that is normally interfaced with a multiplicity M of integrated services digital network (ISDN) channels, a method of controlling the multiplexed transmission of TDM DSL channels over said serial communication link so as to increase the number of TDM DSL channels that may be conveyed by said serial communication link and thereby the number of ISDN channels that may be interfaced with said channel bank comprising the steps of:

(a) generating a plurality of a plurality of multibit B information signal time slots, associated with said J basic TDM DSL channels and an additional number N of TDM DSL channels;

(b) generating a first multibit D channel information signal time slot, which includes multiple pairs of first and second D bits containing signalling information for B information signal time slots contained within a first number of said condensed TDM DSL channels;

(c) generating a second multibit D channel information signal time slot, which includes multiple pairs of first and second D bits containing signalling information for B information signal time slots contained within a second number of said condensed TDM DSL channels;

(d) generating third and fourth multibit information signal time slots, which include N pairs of first and second D channel information bits containing signalling information for B information time slots within said N additional TDM DSL channels, and maintenance channel bits associated with said condensed TDM DSL channels; and

(e) combining the contents of said B information signal time slots, said first and second D channel information signal time slots and said third and fourth multibit information signal time slots with one another to form said plurality of condensed TDM DSL channels, within a plurality K of time division multiplexed time slots.

4. A method according to claim 3, wherein step (e) comprises selectively interleaving said B information signal time slots, said first and second D channel information signal time slots and said third and fourth multibit information signal time slots with one another.

5. A method according to claim 3, wherein step (e) comprises selectively interleaving said third and fourth mutlibit information time slots with said D channel information signal time slots and appending thereto said B information signal time slots.

6. A method according to claim 5, wherein said third multibit information signal time slot contains N pairs of first and second D channel bits containing signalling information for B information time slots within said additional TDM DSL channels, and N maintenance channel bits.

7. A method according to claim 6, wherein said fourth multibit information signal time slot contains J maintenance channel bits.

8. For use with a digital communication network having a serial communication link, which normally conveys thereover a multiplicity J of basic time division multiplexed (TDM) digital subscriber line (DSL) channels, each basic TDM DSL channel having first and second multibit bearer (B) information signal time slots and a multibit data (D) information signal time slot, said D time slot containing signalling information for B information time slots, a maintenance bit and a plurality of auxiliary bits, said serial communication link being coupled to a channel bank, normally interfaced with a multiplicity M of integrated services digital network (ISDN) channels,

a channel bank arrangement for multiplexing condensed TDM DSL channels over said serial communication link, so as to augment said multiplicity J of TDM DSL channels by an additional number of N TDM DSL channels, and thereby increase the total number of TDM DSL channels that may be conveyed by said serial communication link, and thus the number of ISDN channels that may be interfaced with said channel bank, said channel bank arrangement comprising a multiplexer having a plurality P of input ports respectively coupled to receive a plurality of P ISDN channels, where P=J+N, a respective one of said P condensed TDM DSL channels containing first and second multibit B information signal time slots, and a pair of D channel information bits, a serial output port coupled to said serial communication link, and a control port, and a controller coupled to said multiplexer for controlling the manner in which said plurality of P ISDN channels are multiplexed by said multiplexer onto said serial communication link in accordance with a prescribed multiplexing format that includes:

a first multibit D channel information signal time slot, which contains multiple pairs of first and second D bits, containing signalling information for B information signal time slots contained within a first number of said P condensed TDM DSL channels;

a second multibit D channel information signal time slot, which contains multiple pairs of first and second D bits, containing signalling information for B information signal time slots contained within a second number of said P condensed TDM DSL channels;

third and fourth multibit information signal time slots, which contain N pairs of first and second D channel bits containing signalling information for B information time slots within said N additional TDM DSL channels, and P maintenance bits associated with said P condensed TDM DSL channels; and

wherein

the contents of said B information signal time slots, said first and second D channel information signal time slots and said third and fourth multibit information signal time slots are combined with one another to form said plurality P of condensed TDM DSL channels, within a plurality K of time division multiplexed time slots.

9. A channel bank arrangement according to claim 8, wherein said B information signal time slots, said first and second D channel information signal time slots and said third and fourth multibit information signal time slots are selectively interleaved with one another.

10. A channel bank arrangement according to claim 8, wherein said B information signal time slots are appended to time slots containing said first and second D channel information signal time slots and said third and fourth multibit information signal time slots.

11. A channel bank arrangement according to claim 10, wherein said third multibit information signal time slot includes N pairs of first and second D channel bits containing signalling information for B information time slots within said N additional TDM DSL channels, and N maintenance bits.

12. A channel bank arrangement according to claim 11, wherein said fourth multibit information signal time slot contains M maintenance bits.