MIMO soft demodulation using hard-decision candidate selection

A system for reconstructing digital information in a multiple-input receiver from signals transmitted by a multiple-output transmitter, in a multiple-input multiple-output (MIMO) communications channel, the system comprising:

• a plurality of antennas that obtain a plurality of signal streams from a plurality of transmitted signals, wherein the plurality of signal streams includes a first signal stream and a second signal stream;
• a hard-decision demodulator that selects a first candidate signal value for the first signal stream and a second candidate signal value for the second signal stream;
• a demodulator that selects a first plurality of additional candidate signal values for the first signal stream based on the first candidate signal value and a second plurality of additional candidate signal values for the second signal stream based on the second candidate signal value;
• a soft-decision demodulator that computes a first and a second log-likelihood ratio (LLR) from the plurality of signal streams, wherein the first LLR is computed based on the first candidate signal and the first plurality of additional candidate signal values, and the second LLR is computed based on the second candidate signal and the second plurality of additional candidate signal values;
• and
• a decoder that estimates the digital information based on the computed LLR.