Synchronization scheme for digital communications systems transporting data at a customer-controlled rate
First Claim
1. Apparatus for use in a communications system wherein data is transmitted through a communications facility, said apparatus comprisingmeans, responsive to digital signals, for forming data symbols at a first alterable symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of said data symbols;
- means responsive to the formed data symbols for providing additional symbols that are outside said signal constellation so as to raise said first symbol rate to a second symbol rate higher than said first rate; and
means for transmitting said data symbols and additional symbols said second symbol rate to said communications facility.
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Accused Products
Abstract
A synchronization scheme for bidirectional data applications where the customer supplies data for transmission at a rate which is customer controlled. In accordance with the present invention, in each transmission direction, the customer data is converted into data symbols in a predetermined constellation. In response to these data symbols, additional symbols are added. In the disclosed embodiment, the additional symbols added are symbols lying outside of the constellation and are not used to represent customer data. The additional symbols added raise the symbol rate in each transmission direction to one higher than that provided by the symbols representative of the customer data alone. This higher symbol rate in each transmission direction is preferably the same, or the higher symbol rate in one direction is related to the higher symbol rate in the other direction by a rational number. At each receiver, the additional symbols are removed and customer data is recovered from its representative data symbols.
38 Citations
17 Claims
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1. Apparatus for use in a communications system wherein data is transmitted through a communications facility, said apparatus comprising
means, responsive to digital signals, for forming data symbols at a first alterable symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of said data symbols; -
means responsive to the formed data symbols for providing additional symbols that are outside said signal constellation so as to raise said first symbol rate to a second symbol rate higher than said first rate; and means for transmitting said data symbols and additional symbols said second symbol rate to said communications facility. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for use in a communications system whereto data is transmitted through a communications facility, said method comprising the steps of forming data symbols representative of digital signals at a first symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of said data symbols;
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providing additional symbols that lie outside said signal constellation to raise said first symbol rate to a second symbol rate higher than said first rate; and transmitting said data symbols and additional symbols at said second symbol rate to said communications facility.
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9. A communication system comprising a transmitter and a receiver, said transmitter including
means responsive to digital signals for forming data symbols at a first alterable symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of said data symbols; -
means responsive to the formed data symbols for providing additional symbols that lie outsider said signal constellation so as to raise said first symbol rate to a second symbol rate higher than said first rate; and means for transmitting said data symbols and additional symbols at said second symbol rate to said communications facility and said receiver including means for receiving a sequence of said data symbols and additional symbols from said communications facility at a third symbol rate; and means for extracting said additional symbols from said sequence and for mapping each of said data symbols into its representative digital signal. - View Dependent Claims (10, 11)
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12. Apparatus for use in a communications system wherein data is transmitted through a communications facility, said apparatus comprising
means for receiving a sequence of data symbols and additional non-data related symbols from said communications facility at a first symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of data symbols, said data symbols occurring at a second rate which is less than said first symbol rate and said additional symbols being formed in response to said additional non-data related symbols so as to raise said second symbol rate to said first symbol rate; - and
means for mapping each of said data symbols into its represented digital signals, said mapping means providing said represented digital signals at a signal rate which is a multiple of said second symbol rate; wherein said additional symbols lie outside of said signal constellation and are not used to represent said digital signals. - View Dependent Claims (13, 14, 15, 16)
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17. A method for use in a communications system wherein data is transmitted through a communications facility, said method comprising the steps
receiving a sequence of data symbols and additional non-data related symbols from said communications facility at a first symbol rate, each of said data symbols being representative of a plurality of digital signals and lying in a signal constellation including a plurality of said data symbols, said data symbols occurring at a second rate which is less than said first symbol rate and said additional symbols being formed in response to said additional non-data related symbols so as to raise said second symbol rate to said first symbol rate; - and
mapping each of said data symbols into its represented digital signals, said mapping means providing said represented digital signals at a signal rate which is a multiple of said second symbol rate.
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Specification