Near soft-output maximum likelihood detection for multiple-input multiple-output systems using reduced list detection

A method for generating soft-decision output values for a set of transmitted spatial streams in a multiple-input multiple-output (MIMO) communication system, comprising:

• looping over a plurality of constellation points for respective transmitted spatial streams to estimate values for other transmitted streams based at least in part on Reduced List Detection (RLD);
• determining a set of distance metrics as values of the plurality of constellation points for the respective transmitted spatial streams;
• and
• generating soft-decision outputs for the respective transmitted streams based at least in part on the set of distance metrics
• further utilizing Enhanced Metric Usage (EMU), wherein the determining further comprises:
• storing initial distance metrics for a set of constellation points for the set of transmitted streams;
• determining distance metrics as values of the plurality of constellation points for respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams;
• storing distance metrics for respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams in place of higher stored distance metrics for the respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams;
• and
• generating soft-decision outputs for the respective transmitted streams based at least in part on the stored distance metrics.

An apparatus for generating soft-decision output values for a set of transmitted spatial streams in a multiple-input multiple-output (MIMO) communication system, comprising:

• a processor;
• memory in electronic communication with the processor;
• instructions stored in the memory, the instructions being executable by the processor to:
• loop over a plurality of constellation points for respective transmitted spatial streams to estimate values for other transmitted streams based at least in part on Reduced List Detection (RLD);
• determine a set of distance metrics as values of the plurality of constellation points for the respective transmitted spatial streams;
• and
• generate soft-decision outputs for the respective transmitted streams based at least in part on the set of distance metrics,
• wherein the plurality of constellation points are assigned to a particular spatial stream based on the signal strength of the spatial stream, the noise level of the spatial stream, the Signal-to-Noise Ratio (SNR) of the spatial stream, or the capacity of the spatial stream, and
• wherein the spatial streams are sorted in ascending order based on signal strength and a spatial stream with the weakest signal strength is looped over more constellation points than a spatial stream with a stronger signal strength, wherein the signal strength of a spatial stream is indicated by the absolute value of the (Nt,Nt)th element in the corresponding triangular matrix R produced in QR decomposition.

An apparatus for generating soft-decision output values for a set of transmitted spatial streams in a multiple-input multiple-output (MIMO) communication system, comprising:

• a processor;
• memory in electronic communication with the processor;
• instructions stored in the memory, the instructions being executable by the processor to:
• loop over a plurality of constellation points for respective transmitted spatial streams to estimate values for other transmitted streams based at least in part on Reduced List Detection (RLD);
• determine a set of distance metrics as values of the plurality of constellation points for the respective transmitted spatial streams;
• and
• generate soft-decision outputs for the respective transmitted streams based at least in part on the set of distance metrics,
• further utilizing Enhanced Metric Usage (EMU), wherein the determining further comprises:
• storing initial distance metrics for a set of constellation points for the set of transmitted streams;
• determining distance metrics as values of the plurality of constellation points for respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams;
• storing distance metrics for respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams in place of higher stored distance metrics for the respective sets of transmitted spatial streams and corresponding estimated values for other transmitted streams;
• and
• generating soft-decision outputs for the respective transmitted streams based at least in part on the stored distance metrics.

An apparatus for generating soft-decision output values for a set of transmitted spatial streams in a multiple-input multiple-output (MIMO) communication system, comprising:

• means for looping over a plurality of constellation points for respective transmitted spatial streams to estimate values for other transmitted streams based at least in part on Reduced List Detection (RLD);
• means for determining a set of distance metrics as values of the plurality of constellation points for the respective transmitted spatial streams;
• and
• means for generating soft-decision outputs for the respective transmitted streams based at least in part on the set of distance metrics,
• wherein the plurality of constellation points are assigned to a particular spatial stream based on the signal strength of the spatial stream, the noise level of the spatial stream, the Signal-to-Noise Ratio (SNR) of the spatial stream, or the capacity of the spatial stream, and
• wherein the spatial streams are sorted in ascending order based on signal strength and a spatial stream with the weakest signal strength is looped over more constellation points than a spatial stream with a stronger signal strength, wherein the signal strength of a spatial stream is indicated by the absolute value of the (Nt,Nt)th element in the corresponding triangular matrix R produced in QR decomposition.

A computer-program product for generating soft-decision output values for a set of transmitted spatial streams in a multiple-input multiple-output (MIMO) communication system, the computer-program product comprising a non-transitory computer readable medium having instructions thereon, the instructions comprising:

• code for looping over a plurality of constellation points for respective transmitted spatial streams to estimate values for other transmitted streams based at least in part on Reduced List Detection (RLD);
• code for determining a set of distance metrics as values of the plurality of constellation points for the respective transmitted spatial streams;
• and
• code for generating soft-decision outputs for the respective transmitted streams based at least in part on the set of distance metrics,
• wherein the plurality of constellation points are assigned to a particular spatial stream based on the signal strength of the spatial stream, the noise level of the spatial stream, the Signal-to-Noise Ratio (SNR) of the spatial stream, or the capacity of the spatial stream, and
• wherein the spatial streams are sorted in ascending order based on signal strength and a spatial stream with the weakest signal strength is looped over more constellation points than a spatial stream with a stronger signal strength, wherein the signal strength of a spatial stream is indicated by the absolute value of the (Nt,Nt)th element in the corresponding triangular matrix R produced in QR decomposition.