Method and system for decoding multilevel signals
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Abstract
A multilevel optical receiver can comprise a plurality of comparators that generally correspond with the number of levels in a multilevel data stream. Each comparator can be individually controlled and fed a decision threshold in order to decode a multilevel signal. The multilevel optical receiver can generate a statistical characterization of the received symbols in the form of a marginal cumulative distribution function (CDF) or probability density function (pdf). This characterization can be used to produce a set of ε-support estimates from which conditional pdfs are derived for each of the transmission symbols. These conditional pdfs may then be used to determine decision thresholds for decoding the received signal. The conditional pdfs may further be used to continuously estimate the fidelity or error rate of the received signal without the transmission of a testing sequence. The ε-supports may further be used to automatically control the gain on the receiver.
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Citations
90 Claims
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1-70. -70. (canceled)
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71. A desymbolizer for receiving and decoding a multilevel communication signal, comprising:
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an analog-to-digital converter for receiving and decoding the multilevel communication signal and comprising one or more comparators;
a signal integrity unit coupled to the analog-to-digital converter, comprising a microcontroller for controlling a threshold voltage of each comparator located in the first analog-to-digital controller, the microcontroller calculating at least one of a cumulative distribution function and a probability density function derived from the multilevel signal and associated with the threshold voltage of each comparator. - View Dependent Claims (72, 73, 74, 75, 76, 77)
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78. A desymbolizer for receiving and decoding a multilevel communication signal, comprising:
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an analog-to-digital converter for receiving and decoding the multilevel communication signal;
a signal integrity unit coupled to the analog-to-digital converter for calculating and controlling one or more threshold voltages supplied to the analog-to-digital converter, for calculating at least one of a cumulative distribution function and a probability density function derived from the multilevel signal and associated with the one or more threshold voltages; and
a signal conditioning filter that equalizes and optimally filters the multilevel communication signal prior to the analog-to-digital converter, where the signal integrity unit selects an operating point of the signal conditioning filter based upon the determination of the fidelity of the multilevel signal. - View Dependent Claims (79, 80, 81, 82, 83, 84, 85, 86, 87)
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88. A method for determining threshold voltages of comparators in a multilevel signal receiver system, comprising the steps of:
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evaluating voltage levels of a multilevel signal at predetermined time intervals;
estimating a probability density function based on the voltage levels;
determining one or more statistical centers positioned on local minima that are present in the probability density function; and
adjusting one or more threshold voltage levels based on the one or more statistical centers. - View Dependent Claims (89, 90)
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Specification