Synchronization related to data streams

• US 5,335,228 A
• Filed: 09/30/1992
• Issued: 08/02/1994
• Est. Priority Date: 09/30/1992
• Status: Expired due to Fees

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Bottiglieri, Michael P., Dempsey, Peter A. A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Nguyen, Chau T.
• Application Number:
  US07/954,218
• Time in Patent Office: 671 Days
• Field of Search: 370/100.1, 370/105.1, 370/105.4, 370/106, 370/107, 370/94.2, 370/105.2, 370/105.5, 370/110.1, 370/79, 370/82, 370/83, 370/99, 371/67.1, 375/114, 375/116, 375/31, 375/32, 375/112
• US Class Current: 370/512
• CPC Class Codes: H04J 3/0605 Special codes used as synchronising signal

Abstract

A remote terminal for a subscriber loop carrier network operates by flow from one to another of units in the terminal of time division multiplexer data streams of binary valued digital bits. Each stream has the format of periodic frames of time slots of which each frame consists of (a) a service time slot containing only service bits, and (b) a plurality of customer slots which contain mostly bits coded with data from customers of the network, but which also include a less number of service bits. Each unit includes encoding means responsive to local synchronizing and clock pulses derived from data incoming to the unit to encode on each frame of the outgoing data stream synchronizing information consisting of (c) a synchronizing pattern comprising a coded sequence of service bits localized in the frame'"'"'s service slot and (d) a spoiler pattern formed of service bits distributed over customer slots in the frame. The spoiler pattern is interrelated with the synchronizing pattern so that no fortuitous bit sequence occurring in the stream and including any bit beating customer data can falsely duplicate the synchronizing pattern. Each unit also includes decoding means responsive to the presence of synchronizing patterns in an incoming data stream to produce signals for synchronizing the operation of that unit with the pre-established timing of the incoming stream. Such units may be circuit cards having mounted thereon encoding and decoding means in the form of semiconductive integrated circuits and including binary counters used to implement the encoding and decoding functions.

Claims

1. The improvement in apparatus comprising data handling means for receiving data, processing it and forwarding it as at least one time division multiplex data stream constituted of periodic consecutive binary bits and having the format of a plurality of periodic frames of time slots of which each frame comprises a service slot for only service bits and a plurality of customer slots for customer bits and a lesser number of service bits, said improvement comprising:

encoding means operable on said stream to generate in each of said frames both a synchronizing pattern of reserved service bits comprising a sequence of synchronizing bits in said service slot and, also, a spoiler pattern of reserved service bits comprising spoiler bits in said customer slots, said spoiler pattern being interrelated with said synchronizing pattern to preclude any bit sequence present in said stream and including any customer bit from duplicating said synchronization pattern.

2. The improvement according to claim 1 in which said sequence of synchronizing bits consists of 2 m bits where m is an integer, each pair of bits in such sequence for which the two bits in each pair are separated by an m bit interval is a pair of bits of which the combination of their respective binary values has a feature in common with the combinations of values of all other of such bit pairs, and in which in said spoiler pattern each adjacent two of such spoiler bits have respective values so that such pair of values does not duplicate said common feature.

3. The improvement according to claim 2 in which said common feature is that each such pair of bits in said sequence of synchronizing bits have respective values which match each other, and in which each adjacent two spoiler bits in said spoiler pattern have non-matching values.

4. The improvement according to claim 3 in which said sequence of synchronizing bits corresponds in its bit values to a sequence of binary values respective to time sequential bits generated at one bit position in a set of multiple bit position binary number representations of a set of consecutive integers taken in order.

5. The improvement according to claim 1 in which said synchronizing pattern includes a header section disposed in said data stream prior to said sequence of synchronizing bits, said header section producing at the start of said synchronizing pattern a group of bits different in coding than any other group of bits in said synchronizing pattern.

6. The improvement according to claim 4 in which said synchronizing pattern includes a header section disposed in said data stream prior to said sequence of synchronizing bits, said header section producing at the start of said synchronizing pattern a group of bits different in coding than any other group of bits in said synchronizing pattern.

7. The improvement according to claim 1 in which said data handling means is a circuit pack.

8. The improvement according to claim 1 in which said data handling means receives a data stream which is separate from the aforesaid data stream forwarded by said data handling means, and which received data stream has the same format as said forwarded data stream so as to also include a synchronizing pattern and a spoiler pattern in each of a plurality of frames in such stream, and in which said improvement further comprises decoding means responsive to and only to the presence in said received data stream of the entirety of the last named synchronizing pattern to produce a synchronizing signal.

9. The improvement according to claim 8 in which said decoding means is provided by a circuit pack.

10. The improvement in a remote terminal comprising a primary distribution unit for exchanging information with a central office, a plurality of secondary distribution units for exchanging information with telephone sets of customers at remote locations from said terminal, and information transfer facilities interconnecting said primary unit and secondary units to implement exchange of information through said primary unit and secondary units between said central office and said telephone sets via first time division multiplex data streams transmitted from said primary unit to each of said secondary units, and via second time division multiplex data streams transmitted from each of said secondary units to said primary unit, each of said time division multiplex data streams being constituted of periodic consecutive binary bits and having the format of a plurality of periodic frames of time slots of which each of said frames comprises a service slot for only service bits and a plurality of customers slots for customer bits and a lesser number of service bits, and said improvement comprising:

a first plurality of encoding means each incorporated in said primary unit and respectively corresponding to said first data streams and each operable on the corresponding first stream to generate in each of the frames therein both a synchronizing pattern of reserved service bits comprising a sequence of synchronizing bits in the service slot of such frame and, also, a spoiler pattern of reserved service bits comprising spoiler bits in customer slots of such frame, said spoiler pattern being interrelated with said synchronizing pattern to preclude any bit sequence present in the last named stream and including any customer bit from duplicating said synchronizing pattern, a first plurality of decoding means incorporated said primary unit and respectively corresponding to said second data streams and operable to detect the binary values of the bits therein, each such decoding means in said first plurality thereof being responsive to and only to detection thereby of the presence in the corresponding second data stream of a full synchronizing pattern to produce a synchronizing signal utilized by the primary unit, a second plurality of encoding means respectively corresponding to and incorporated said secondary distribution units and operable in the same manner as said encoding means in said first plurality thereof to generate synchronization and spoiler patterns in the second data streams transmitted from said secondary units to said primary unit, and a second plurality of decoding means respectively corresponding to and incorporated in said secondary distribution units and each operable in the same manner as said decoding means in said first plurality thereof to be responsive to and only to the presence of a full synchronizing pattern in the first data stream reaching the secondary distribution unit corresponding to that decoding means to produce a synchronizing signal utilized by that secondary distribution unit.

11. A method of introducing synchronizing information into a time division multiplex data stream constituted of periodic consecutive binary bits and having the format of a plurality of periodic frames of time slots of which each frame comprises a service slot for service bits only and a plurality of customer slots for customer bits and for a lesser number of service bits, said method comprising, generating in each of said frames in said stream a synchronizing pattern comprising a sequence of reserved synchronizing bits in said service slot, and further generating in each such frame a spoiler pattern of reserved service bits comprising spoiler bits in said customer slots, said synchronizing pattern and spoiler pattern being interrelated to preclude any bit sequence present in said stream and including any customer bit from duplicating such synchronization pattern.

12. Apparatus comprising, a circuit card usable in equipment in a telecommunications network for conveying information of customers thereof, circuitry on said card to receive and process data and to forward it in the form of an outgoing time division multiplexer stream of periodically recurring consecutive binary valued digital bits, said stream having the format of periodic flames of time slots of which each frame consists of a service time slot comprising service bits, and, also, of a plurality of customer time slots each consisting of customer bits for carrying customer information and of a lesser number of service bits, and encoding means mounted on said card and in the form of a semiconductive integrated circuit, said encoding means being responsive to local synchronizing signals derived from said received data to generate in said stream both a synchronizing pattern comprising the binary values of a sequence of service bits in said service slot and reserved for such pattern and, also, a spoiler pattern comprising the binary values of a plurality of spoiler service bits which are respectively distributed over and included in said plurality of customer slots and are reserved for said spoiler pattern, said synchronous pattern and spoiler pattern being interrelated to prevent any bit sequence in said stream which includes any customer bit from fully duplicating said synchronization pattern.