Synchronization scheme for a digital communications system
AssigneeAT&T Bell Laboratories
InventorsMassimo Sorbara, Jean-Jacques Werner
Life of this patent
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Abstract
A synchronization scheme for a digital communications system wherein customer data is connected to a synchronous communications network utilizes auxiliary symbols to provide frame synchronization. Each such auxiliary symbol lies outside of a conventional symbol constellation and is only used to represent framing information. Variations of the customer data rate relative to an expected rate are compensated for by the use of stuff and delete bits in each frame. These bits can be either customer data bits or ancillary bits depending on the direction of this variation. Advantageously, the auxiliary symbols also provide a determination of whether the stuff and delete bits in any frame are customer data or ancillary bits.
Claims20
Apparatus for use in a communications system, said apparatus comprising a transmitter and receiver respectively connected to different ends of a communications channel, said transmitter comprising
- means for receiving customer data bits and arranging them into a succession of frames, each frame including a predetermined number of bits, and
- means for generating a succession of data symbols representative of said customer data bits in each frame along with a framing symbol which identifies each frame so as to enable delineation of one frame from another in said succession, each framing symbol being different from any of the data symbols and lying outside of a boundary encompassing said plurality of data symbols and formed by interconnecting outermost data symbols in said symbol constellation, and said receiver comprising
- means for examining said framing symbols, and
- means responsive to the examination of said framing symbols for mapping said data symbols into their representative customer data bits and for identifying each frame in said succession of frames.
Apparatus for use in a digital communications system wherein a plurality of data symbols forming a symbol constellation are transmitted through a communications channel, each symbol being representative of a plurality of customer data bits, said apparatus comprising
- means for receiving said customer data bits and arranging them into a succession of frames, each frame including a predetermined number of bits, and
- means for generating a succession of data symbols representative of said customer data bits in each frame along with at least one framing symbol which identifies each frame so as to enable delineation of one frame from another in said succession, each framing symbol being different from any of the data symbols and lying outside of a boundary encompassing said plurality of data symbols and formed by interconnecting outermost data symbols in said symbol constellation.
A method for use in a digital communications system wherein a plurality of data symbols forming a symbol constellation are transmitted through a communications channel, each data symbol being representative of a plurality of customer data bits, said method comprising the steps of
- receiving said customer data bits and arranging them into a succession of frames, each frame including a predetermined number of bits, and
- generating a succession of data symbols representative of said customer data bits in each frame along with a framing symbol which identifies each frame so as to enable delineation of one frame from another in said succession, each framing symbol being different from any of the data symbols and lying outside of a boundary encompassing said plurality of data symbols and formed by interconnecting outermost data symbols in said symbol constellation.
Apparatus for use in a digital communications system wherein a plurality of data symbols forming a symbol constellation are transmitted through a communications channel, each data symbol being representative of a plurality of customer data bits said bits being arranged into a succession of frames, said apparatus comprising
- means for examining auxiliary symbols which have also been transmitted through said communications channel and are different from any of said data symbols, and
- means responsive to the examination of said auxiliary symbols for mapping said data symbols into their representative customer data bits and for identifying each frame in said succession of frames.
Apparatus for use in the communication system wherein a plurality of symbols forming a symbol constellation are transmitted through a communications channel, said apparatus comprising
- means for receiving a succession of symbols arranged into frames, each frame including symbols which are representative of customer data bits, and framing symbols which serve to delineate one frame from another, and
- means for extracting said framing symbols in said received succession of symbols and outputting customer data bits representative of each symbol, said framing symbols being different from any of the data symbols and lying outside of a boundary encompassing said plurality of data symbols and formed by interconnecting outermost data symbols in said symbol constellation.
Apparatus for use in a communications system which receives and delivers bits representing customer data, said apparatus comprising
- means for arranging the customer data bits into a succession of frames, each frame including a plurality of customer data bits along with other bits, each of these other bits being selected from one of a plurality of sources based on a predetermined criteria, and
- means for providing a predetermined pattern of bits per frame, said pattern serving to delineate one frame from another and also to identify the selected source for each of the other bits.
Apparatus for use in a digital communications system wherein a plurality of symbols forming a symbol constellation are transmitted through a communications channel, said apparatus comprising
- means for receiving customer data bits and arranging them into a succession of frames, each frame including a predetermined number of bit positions allocated for customer data bits and a predetermined number of other bit positions into which bits from different bit sources can be inserted, and
- means for generating a succession of symbols representative of the bits in the bit positions in said succession of frames along with at least one framing symbol for each frame, said framing symbol identifying each frame and being different from any of the symbols and said framing symbol serving to identify the source of each bit in said other bit positions.
Apparatus for use in the communications system which receives and delivers bits representing customer data, said apparatus comprising
- means for receiving a succession of frames, each frame including at least one framing bit, a plurality of customer data bits and other bits, each these other bits being selected from one of a plurality of sources based on a predetermined criteria, and
- means responsive to an examination of said framing bits for identifying the source of each of said other bits in said succession of frames.
Apparatus for use in a digital communications system wherein a plurality of symbols forming a symbol constellation are transmitted through a communications channel, said apparatus comprising
- means for receiving a succession of symbols arranged into frames, each frame including first symbols, second symbols, and framing symbols, and
- means for examining said framing symbols in said received succession of symbols and outputting customer data bits representative of each first symbol, said examining means also outputting customer data bits representative of said second symbols and not outputting customer data bits representative of these symbols in response to different results of said examination.
Dependencies are inferred from the claim text.