Equalizer for heavily clipped or compressed communications signals

A method of equalization in a receiver, the method comprising:

• receiving a communications signal having symbols embedded therein;
• converting the received communications signal from analog form to digital form to generate a digital received signal comprising soft symbols, wherein the digital received signal is quantized to at least 3 bits;
• selectively equalizing a current soft symbol sample based at least partly on a determination of whether or not at least one of the current soft symbol sample or an immediately prior soft symbol sample to the current soft symbol sample has been non-linearly distorted beyond a threshold, wherein the threshold indicates clipping and/or harsh compression, wherein selective equalizing further comprises:
• applying no equalization to the current soft symbol sample when the current soft symbol sample is above the threshold;
• applying linear equalization to the current soft symbol sample when both the current soft symbol sample and the symbol sample immediately prior to the current soft symbol sample are below the threshold;
• and
• applying modified equalization to the current soft symbol sample when the current soft symbol sample is below the threshold and the symbol sample immediately prior to the current soft symbol sample is above the threshold, wherein the modified equalization comprises modifying an effective value of an equalizer coefficient by a modified weight wmod, wherein wmod is greater than or equal to 1 and less than or equal to w_max, wherein
• w_max
• =
• 1
• -
• 2
• -
• num
• ⁢
• ⁢
• _
• ⁢
• ⁢
• A
• ⁢
• ⁢
• D
• ⁢
• ⁢
• C
• ⁢
• ⁢
• _
• ⁢
• ⁢
• bits
• clip_level
• wherein num_ADC_bits represents a number of bits quantized by an analog-to-digital converter for the soft symbol samples and wherein clip_level represents a magnitude level wherein a soft symbol is clipped.

An apparatus for equalization in a receiver, the apparatus comprising:

• a detection circuit configured to receive a digital received signal comprising soft symbols, wherein the digital received signal is quantized to at least 3 bits, wherein the detection circuit is configured to determine whether a sample has been non-linearly distorted beyond a threshold, wherein the threshold indicates clipping and/or harsh compression;
• and
• an equalizer configured to receive the digital received signal, the equalizer configured to selectively equalize a current soft symbol sample based at least partly on a determination of whether or not at least one of the current soft symbol sample or an immediately prior soft symbol sample to the current soft symbol sample has been non-linearly distorted beyond the threshold, wherein the equalizer is further configured to:
• bypass equalization to the current soft symbol sample when the current soft symbol sample is above the threshold;
• and
• apply linear equalization to the current soft symbol sample when the current soft symbol sample is below the threshold.

An apparatus for equalization in a receiver, the apparatus comprising:

• a detection circuit configured to receive a digital received signal comprising soft symbols, wherein the digital received signal is quantized to at least 3 bits, wherein the detection circuit is configured to determine whether a sample has been non-linearly distorted beyond a threshold, wherein the threshold indicates clipping and/or harsh compression;
• and
• an equalizer configured to receive the digital received signal, the equalizer configured to selectively equalize a current soft symbol sample based at least partly on a determination of whether or not at least one of the current soft symbol sample or an immediately prior soft symbol sample to the current soft symbol sample has been non-linearly distorted beyond the threshold, wherein the equalizer is further configured to:
• bypass equalization to the current soft symbol sample when the current soft symbol sample is above the threshold;
• apply linear equalization to the current soft symbol sample when both the current soft symbol sample and the soft symbol sample immediately prior to the current soft symbol sample are below the threshold;
• and
• apply modified equalization to the current soft symbol sample when the current soft symbol sample is below the threshold and the soft symbol sample immediately prior to the current soft symbol sample is above the threshold, wherein the modified equalization comprises modifying an effective value of an equalizer coefficient by a modified weight wmod, wherein wmod is greater than or equal to 1 and less than or equal to w_max, wherein
• w_max
• =
• 1
• -
• 2
• -
• num
• ⁢
• ⁢
• _
• ⁢
• ⁢
• A
• ⁢
• ⁢
• D
• ⁢
• ⁢
• C_
• ⁢
• ⁢
• bits
• clip_level
• wherein num_ADC_bits represents a number of bits quantized by an analog-to-digital converter for the soft symbol samples and wherein clip_level represents a magnitude level wherein a soft symbol is clipped.