# US 2014/0092948 A1 · Automated erasure slicer threshold control and modification of symbol estimates to be erased > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0092948 A1 - Document ID: US20140092948A1 - Status: Published application - Kind: A1 - Application number: 13/631,229 - Filed: 2012-09-28 - Published: 2014-04-03 - Earliest claimed: 2012-09-28 - Assignees: Intel Corporation - Inventors: Noam Tal - Web page: https://patentgrep.com/patent/US20140092948A1 ## CPC - H04L 25/0307: {using blind adaptation} - H04L 25/063: {Setting decision thresholds using feedback techniques only} - H04L 2025/0342: {QAM} - H04L 2025/03694: {Stop and go} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Methods and systems to vary an erasure slicer threshold based on a measure computed from prior soft and/or hard symbol decisions, identify reliable symbol estimates based on the threshold, identify unreliable symbol estimates for erasure based on the threshold, modify the identified symbol estimates, output the reliable symbol estimates and the modified symbol estimates as erasure slicer decisions, and filter the decisions in a feedback filter of a decision feedback equalizer (DFE). The erasure slicer threshold may be based on signal-to-noise ratio (SNR) or mean-squared-error (MSE). A symbol estimate may be identified for erasure when a coordinate of the corresponding soft decision is within an erasure area defined by the threshold. Symbol modification may include replacing a corresponding coordinate of the symbol estimate with a coordinate of a decision boundary associated with the erasure area. ## Claims ### Claim 1 An apparatus, comprising: an erasure slicer to evaluate soft decisions of symbols of a quadrature amplitude modulated (QAM) signal for erasure based on a threshold; and a threshold module to compute the threshold based on a measure computed from prior symbol decisions and to vary the threshold based on variations in the measure. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the threshold module is configured to compute the threshold as a running average of the measure over a sliding window of the symbols. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the threshold module is configured to compute the threshold based on a signal-to-noise ratio of the symbols. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the threshold module is configured to compute the threshold based on a mean squared error between the soft decisions and corresponding hard decisions. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the threshold module includes an infinite impulse response filter to compute the threshold over a sliding window of the symbols. ### Claim 6 (depends on 1) The apparatus of claim 1, further including a weighting module to weight the measure with a user-configurable weight. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the erasure slicer is configured to: evaluate the soft decisions with respect to erasures areas that extend from decision boundaries of a QAM constellation by a distance based on the threshold; estimate a symbol of a soft decision based on proximity of the soft decision to a point in the QAM constellation and output the symbol estimate as a decision if the soft decision is not within an erasure area; and modify the symbol estimate when the soft decision is within an erasure area and output the modified symbol estimate as the decision. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the erasure slicer is further configured to: identify a coordinate of the soft decision that is within the erasure area; and replace a corresponding coordinate of the symbol estimate with a coordinate of a decision boundary of the erasure area. ### Claim 9 (depends on 7) The apparatus of claim 7, further including: a decision feedback equalizer including a feedback filter to filter decisions of the erasure slicer, including symbol estimates and modified symbol estimates. ### Claim 10 A non-transitory computer readable medium encoded with a computer program, including instructions to cause a processor to: evaluate soft decisions of symbols of a quadrature amplitude modulated (QAM) signal for erasure based on a threshold; and compute the threshold based on a measure computed from prior symbol decisions, and vary the threshold based on variations in the measure. ### Claim 11 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor to compute the threshold as a running average of the measure over a sliding window of the symbols. ### Claim 12 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor to compute the threshold based on a signal-to-noise ratio of the symbols. ### Claim 13 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor to compute the threshold based on a mean squared error (MSE) between the soft decisions and corresponding hard decisions. ### Claim 14 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor to compute the threshold with an infinite impulse response filter over a sliding window of the symbols. ### Claim 15 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor weight the measure with a user-configurable weight. ### Claim 16 (depends on 10) The computer readable medium of claim 10, further including instructions to cause the processor to: evaluate the soft decisions with respect to erasures areas that extend from decision boundaries of a QAM constellation by a distance based on the threshold; estimate a symbol of a soft decision based on proximity of the soft decision to a point in the QAM constellation and output the symbol estimate as a decision if the soft decision is not within an erasure area; and modify the symbol estimate when the soft decision is within an erasure area and output the modified symbol estimate as the decision. ### Claim 17 (depends on 16) The computer readable medium of claim 16, further including instructions to cause the processor to: identify a coordinate of the soft decision that is within the erasure area; and replace a corresponding coordinate of the symbol estimate with a coordinate of a decision boundary of the erasure area. ### Claim 18 (depends on 16) The computer readable medium of claim 16, further including instructions to cause the processor to: filter decisions of the erasure slicer, including symbol estimates and modified symbol estimates, in a feedback filter of a decision feedback equalizer. ### Claim 19 A method, comprising: evaluating soft decisions of symbols of a quadrature amplitude modulated (QAM) signal for erasure based on a threshold; and computing the threshold based on a measure computed from prior symbol decisions and varying the threshold based on variations in the measure. ### Claim 20 (depends on 19) The method of claim 19, further including computing the threshold as a running average of the measure over a sliding window of the symbols. ### Claim 21 (depends on 19) The method of claim 19, further including computing the threshold based on a signal-to-noise ratio of the symbols. ### Claim 22 (depends on 19) The method of claim 19, further including computing the threshold based on a mean squared error between the soft decisions and corresponding hard decisions. ### Claim 23 (depends on 19) The method of claim 19, further including computing the threshold with an infinite impulse response filter over a sliding window of the symbols. ### Claim 24 (depends on 19) The method of claim 19, further including weighting the measure with a user-configurable weight. ### Claim 25 (depends on 19) The method of claim 19, further including: evaluating the soft decisions with respect to erasures areas that extend from decision boundaries of a QAM constellation by a distance based on the threshold; estimating a symbol of a soft decision based on proximity of the soft decision to a point in the QAM constellation and outputting the symbol estimate as a decision if the soft decision is not within an erasure area; and modifying the symbol estimate when the soft decision is within an erasure area and outputting the modified symbol estimate as the decision. ### Claim 26 (depends on 25) The method of claim 25, further including: identifying a coordinate of the soft decision that is within the erasure area; and replacing a corresponding coordinate of the symbol estimate with a coordinate of a decision boundary of the erasure area. ### Claim 27 (depends on 25) The method of claim 25, further including: filtering decisions of the erasure slicer, including symbol estimates and modified symbol estimates, in a feedback filter of a decision feedback equalizer. ### Claim 28 A system, comprising: a processor system and memory; a user interface system; and a communication system to interface between a wireless access point of a communication network and one or more of the processor and the user interface system, wherein the communication system includes a demodulator, and wherein the demodulator includes, an erasure slicer to evaluate soft decisions of symbols of a quadrature amplitude modulated (QAM) signal for erasure based on a threshold, and to provide decisions to a feedback filter of a decision feedback equalizer (DFE), and a threshold module to compute the threshold based on a measure computed from prior symbol decisions and to vary the threshold based on variations in the measure. ### Claim 29 (depends on 28) The system of claim 28, wherein the threshold module is configured to compute the threshold based on a mean squared error (MSE) between the soft decisions and corresponding hard decisions. ### Claim 30 (depends on 28) The system of claim 28, wherein the erasure slicer is configured to: evaluate the soft decisions with respect to erasures areas that extend from decision boundaries of the QAM constellation by a distance based on the threshold; estimate a symbol of a soft decision based on proximity of the soft decision to a point in the QAM constellation and output the symbol estimate as a decision if the soft decision is not within an erasure area; and modify the symbol estimate when the soft decision is within an erasure area and output the modified symbol estimate as the decision. ### Claim 31 (depends on 30) The system of claim 30, wherein the erasure slicer is further configured to: identify a coordinate of the soft decision that is within the erasure area; and replace a corresponding coordinate of the symbol estimate with a coordinate of a decision boundary of the erasure area.