Method of, and apparatus for, slicing a signal
OwnerPeter James Livermore, Graham Butler +1inventors
InventorsPeter James Livermore, Graham Butler, John Stuart Hill
Life of this patent
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Abstract
A method of, and apparatus for, slicing a modulated input signal is disclosed. The method comprises: generating at least one slice threshold level (20); comparing (3) the magnitude of the input signal (1) with the at least one threshold level to produce a corresponding sliced signal having a first magnitude if the input signal is greater than the threshold level and having a second magnitude if the input signal is less than the threshold level. The method further comprises detecting errors (5) in the sliced signal and producing a corresponding error signal; and setting the threshold level in response to the error signal.
Claims12
A method of slicing a modulated input signal which includes both source data and forward error correction (FEC) information, the method comprising:
- generating at least one slice threshold level;
- comparing the magnitude of the input signal with the at least one threshold level to produce a corresponding sliced signal having a first magnitude indicative of a logic “0” if the input signal is greater than the threshold level and having a second magnitude indicative of a logic “0” if the input signal is less than the threshold level, characterised by detecting errors in the sliced signal using the error correction information and producing corresponding error signals (E0, E1) indicative of a rate of logic “0s” being sliced erroneously as logic “1s” (E1) and a rate of logic “1s” being sliced erroneously as logic “0s” (E0);
- and setting the threshold level in response to the error signals (E0, E1) such as to substantially minimise the number of logic “1s” and “0s” being sliced erroneously.
A method according to any preceding claim, and further comprising:
- extracting source data form the sliced signal, detecting errors;
- correcting those errors using the forward error correction information and searching for a better slice threshold level during a period in which the rate of errors after error correction is substantially zero.
A method according to any preceding claim, and further comprising searching for a better slice threshold level by:
- varying the slice threshold level from a first level, at which the rate of errors being detected is relatively low, (a) to a second level higher than the first, at which the rate of errors being detected is some particular rate higher than said relatively low rate and (b) to a third level lower than the first, at which the rate of errors being detected is some particular rate higher than said relatively low rate, and then changing the slice level to a level between the second and third levels calculated from those levels.
Apparatus for slicing a modulated input signal, the input signal including both source data and forward error correction (FEC) information, the apparatus comprising:
- a slice threshold generator (20) for generating at least one slice threshold level (V);
- a signal slicer (3) for comparing the magnitude of the input signal with the at least one threshold level to produce a corresponding sliced signal having a first magnitude indicative of a logic “1” if the input signal is greater than the threshold level and having a second magnitude indicative of a logic “0” if the input signal is less than the threshold level;
- characterised by an error detector (5) for detecting errors in the sliced signal using the error correction information and producing error signals (E0, E1) indicative of a rate of logic “0s” being sliced erroneously as logic “1s” (E1) and a rate of logic “1s” being sliced erroneously as logic “0s” (E0);
- and means (14, 16-19) for setting the threshold level in response to the error signals (E0, E1) such as to substantially minimise the number of logic “1s” and “0s” being sliced erroneously.
Dependencies are inferred from the claim text.