Digital communications synchronization scheme
AssigneeAT&T Bell Laboratories
InventorJean-Jacques Werner
Life of this patent
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Abstract
A synchronization scheme for use in digital communications systems selectively replaces data-representative symbols that would ordinarily be transmitted through a plurality of communications channels with associated replacement symbols that represent the data and provide a synchronization mechanism. In the receiver, the replacement symbols are detected and control circuitry which determines the difference in propagation delay between communications channels. Advantageously, this scheme can provide a determination of the propagation delay difference between communications channels while such channels are being used to transmit customer data and does not alter the timing or format of such data.
Claims21
Apparatus for use in a digital communications system wherein symbols representative of information are transmitted through a plurality of communications channels, said apparatus comprising
- means for supplying said information;
- and
- means responsive to said supplied information for providing said symbols for transmission through said communications channels, said providing means also providing a replacement symbol in lieu of one of said symbols for each of said channels upon an occurrence of a predetermined condition, each replacement symbol being different from any of said symbols and each replacement symbol and the symbol it replaces being representative of the same information.
Apparatus for use in a digital communications system wherein symbols representative of information are received from a plurality of communications channels, each of said communications channels having propagation delay, said apparatus comprising
- means for detecting said received symbols from each communications channel;
- and
- means responsive to certain detected received symbols for determining any difference in signal propagation delay between said communications channels, each of said certain detected received symbols being a replacement symbol which was transmitted in lieu of one of said symbols for each of said channels upon an occurrence of a predetermined condition, each replacement symbol being different from any of said symbols and each replacement symbol and the symbol it replaces being representative of the same information.
A digital communications system wherein symbols representative of information are transmitted through a plurality of communications channels, each of said communications channels having signal propagation delay, said system comprising
- a transmitter comprising
- means for supplying said information;
- and
- means responsive to said supplied information for providing said symbols for transmission through said communications channels, said providing means also providing a replacement symbol for in lieu of one of said symbols for each of said channels upon an occurrence of a predetermined condition, each replacement symbol being different from any of said symbols and each replacement symbol and the symbol it replaces being representative of the same information;
- and a receiver comprising
- means for detecting said received symbols from said communications channels;
- and
- means responsive to certain detected received symbols for determining any difference in signal propagation delay between said communications channels.
A method for use in a digital communications system wherein symbols representative of information are transmitted through a plurality of communications channels, said method comprising the steps of
- providing a replacement symbol in lieu of one of said symbols for each of said channels upon an occurrence of a predetermined condition, each replacement symbol being different from any of said symbols and each replacement symbol and the symbol it replaces being representative of the same information;
- detecting said replacement symbols from said communications channels;
- and
- determining any difference in signal propagation delay between said communications channels in response to said detected replacement symbols.
Receiver apparatus for use in a digital communications system wherein symbols representative of information are transmitted through a plurality of communications channels, each of said communications channels having propagation delay, said apparatus comprising
- means for detecting received replacement symbols from each of said communications channels, each replacement symbol being transmitted in lieu of one of said symbols, each replacement symbol being different from any of said symbols and each replacement symbol and the symbol it replaces being representative of the same information;
- and
- means responsive to replacement symbols from each of said communications channels for determining any difference in signal propagation delay between said communications channels.
Dependencies are inferred from the claim text.