Constellation selection threshold adaptation for slicer
View Patent ↗System and method of adapting thresholds for constellation selection based on statistic distributions of received data symbols. To determine an adapted threshold, an expected ratio of received symbols with values in a certain range is preset based on an expected statistic distribution of data symbols across the multiple constellations. A first and a second ratios are defined based on the expected ratio, the first ratio being the expected ratio minus an error ratio and the second ratio being the expected ratio plus the error ratio. A first value is determined which makes the received symbols in a firs range to constitute the first ratio of a set of slicer inputs. A second value is determined which makes the received symbols in the second range to constitute the second ratio of a set of slicer outputs. The adapted threshold is then obtained based on the first and the second value.
1. A method of dynamically determining a threshold of a slicer, the method comprising:
accessing a first plurality of inputs for supply to said slicer;
comparing each of said first plurality of inputs with a first value;
based on said comparing with said first value, determining a first count ratio of first inputs to said first plurality of inputs, wherein each of said first inputs is comprised in said first plurality of inputs and has a value encompassed in a first range that is defined by said first value; and
determining said threshold of said slicer based on said first value and said first count ratio.
2. The method of claim 1 , further comprising:
accessing a second plurality of inputs for supply to said slicer;
comparing each of said second plurality of inputs with a second value; and
based on said comparing with said second value, determining a second count ratio of second inputs to said second plurality of inputs, wherein each of said second inputs is comprised in said second plurality of inputs and has a value encompassed in a second range that is defined by said second value;
wherein said determining said threshold of said slicer is further based on said second value and said second count ratio.
3. The method of claim 2 , wherein said determining said threshold comprises averaging said first value and said second value.
4. The method of claim 2 further comprising determining said first value and said second value, wherein said determining said first value comprises adjusting said first value until said first count ratio equals a nominal ratio minus a preset value, and wherein said determining said second value comprises adjusting said second value until said second count ratio equals said nominal ratio plus said preset value.
5. The method of claim 4 , wherein said slicer is configured to use Pulse Amplitude Modulation (PAM) comprising N constellation levels, wherein N is an integer greater than 1, wherein said nominal ratio equals
i
N
,
wherein i is an integer greater than 0 and smaller than N, and wherein said preset value is equal to or less than 5.
6. The method of claim 4 , wherein said slicer is configured to use Quadrature Amplitude Modulation (QAM) comprising 2×N constellation levels, wherein N is an integer greater than 1, wherein said nominal ratio equals
i
N
,
wherein i is an integer greater than 0 and smaller than N, and wherein said preset value is equal to or less than 5.
7. The method of claim 2 , wherein said first plurality of inputs and said second plurality of inputs are output from an equalizer in a receiver.
8. The method of claim 2 , wherein said first range encompasses any value below said first value, and wherein said second range encompasses any value below said second value.
9. A device comprising:
a slicer configured to:
produce a first output value responsive to an input greater than a threshold, and
produce a second output value responsive to an input smaller than said threshold; and
a threshold adaptation unit coupled to said slicer, the threshold adaptation unit comprising:
a comparator configured to compare each of a first plurality of inputs with a first value, wherein said first plurality of inputs are supplied to said slicer; and
a first counter configured to, responsive to comparison decisions output from said comparator, produce a number of first inputs comprised in said first plurality of inputs and each having a value encompassed in a first range, wherein said first range is defined by said first value;
wherein the threshold adaptation unit is configured to:
determine a first count ratio of said number of first inputs to a total number of said first plurality of inputs, and
determine an adapted threshold of said slicer based on said first value and said first count ratio.
10. The device of claim 9 , wherein said threshold adaptation unit is further configured to access a second plurality of inputs for supply to said slicer; said comparator compares each of said second plurality of inputs with a second value; and wherein said threshold adaptation unit further comprises a second counter configured to, based on said comparison with said second value, determine a second count ratio of second inputs to said second plurality of inputs, wherein each of said second inputs is comprised in said second plurality of inputs and has a value encompassed in a second range that is defined by said second value,
wherein said adapted threshold is determined also based on said second value and said second count ratio.
11. The device of claim 10 , wherein said threshold adaptation unit is further configured to average said first value and said second value to generate said adapted threshold for said slicer.
12. The device of claim 10 , wherein said threshold adaptation unit is further configured to:
determine said first value by varying said first value until said first count ratio equals a nominal ratio minus a preset value; and
determine said second value by varying said second value until said second count ratio equals said nominal ratio plus said preset value.
13. The device of claim 12 , wherein said slicer is further configured to use Pulse Amplitude Modulation (PAM) comprising N constellation levels, wherein N is an integer greater than 1, wherein said first output value and said second output value are selected from said N constellation levels, and wherein said nominal ratio equals
i
N
,
wherein i is an integer greater than 0 and smaller than N, and wherein said preset value is equal to or less than 5.
14. The device of claim 12 , wherein said slicer is further configured to use Quadrature Amplitude Modulation (QAM) comprising 2×N constellation levels, wherein N is an integer greater than 1, wherein said nominal ratio equals
i
N
,
wherein i is an integer greater than 0 and smaller than N, and wherein said preset value is equal to or less than 5.
15. The device of claim 10 , wherein said first range encompasses any value below said first value, and wherein said second range encompasses any value below said second value.
16. A receiver comprising:
an analog-to-digital converter (ADC) configured to convert received analog signals to digital signals;
an equalizer coupled to said ADC and configured to:
generate equalized signals responsive to said digital signals, and
send said equalized signals as inputs to a slicer;
said slicer coupled to said equalizer and configured to:
produce a first output value responsive to an input greater than a threshold, and
produce a second output value responsive to an input smaller than said threshold; and
a threshold adaptation unit coupled to said slicer and configured to:
access a first plurality of inputs for supply to said slicer,
compare each of said first plurality of inputs with a first value,
based on comparison with said first value, determine a first count ratio of first inputs to said first plurality of inputs, wherein each of said first inputs is comprised in said first plurality of inputs and has a value encompassed in a first range that is defined by said first value,
access a second plurality of inputs for supply to said slicer,
compare each of said second plurality of inputs with a second value,
based on comparison with said second value, determine a second count ratio of second inputs to said second plurality of inputs, wherein each of said second inputs is comprised in said second plurality of inputs and has a value encompassed in a second range that is defined by said second value,
determine an adapted threshold based on said first value, said second value, said first count ratio, and said second count ratio, and
send said adapted threshold to said slicer.
17. The receiver of claim 16 , wherein said threshold adaptation unit is further configured to determine said adapted threshold by averaging said first value and said second value.
18. The receiver of claim 16 , wherein said threshold adaptation unit is further configured to:
determine said first value by adjusting said first value until said first count ratio equals a nominal ratio minus a preset value, and
determine said second value by adjusting said second value until said second count ratio equals said nominal ratio plus said preset value.
19. The receiver of claim 16 , wherein said slicer is configured to use one of Pulse Amplitude Modulation (PAM) comprising N constellation levels and Quadrature Amplitude Modulation (QAM) comprising 2×N constellation levels, wherein N is an integer greater than 1, wherein said nominal ratio equals
i
N
,
wherein i is an integer greater than 0 and smaller than N, and wherein said preset value is equal to or less than 5.
20. The receiver of claim 16 , wherein said first range encompasses any value below said first value, and wherein said second range encompasses any value below said second value.