Soft demapping for MIMO decoding

A method comprising:

• providing a look-up table that comprises distance information corresponding to a distance between a potential candidate symbol and a most proximate competing symbol for each bit of a plurality of potential candidate symbols;
• receiving a plurality of candidate symbols that are provided a maximum likelihood solution and correspond to a plurality of antenna layers of a multiple input multiple output (MIMO) wireless communication system;
• selecting a first candidate symbol from the plurality of candidate symbols, wherein the first candidate symbol corresponds to a first potential candidate symbol of the plurality of candidate symbols;
• obtaining the distance information for each bit of the first potential candidate symbol from the look-up table;
• and
• determining likelihood indicium for each bit of the first candidate symbol as a function of the distance information for each bit of the first potential candidate symbol, wherein the likelihood indicium for a given bit is indicative of a likelihood that a value for the given bit is a logic 1 or a logic 0,
• wherein symbols transmitted in a first data stream corresponding to a first of the plurality of antenna layers are modulated using a first type of modulation, symbols transmitted in a second data stream corresponding to a second of the plurality of antenna layers are modulated using a second type of modulation, which is different than the first type of modulation, and the look-up table comprises distance information corresponding to the distance between the potential candidate symbol and the most proximate competing symbol for each bit of a plurality potential candidate symbols for both the first type of modulation and the second type of modulation.

A multiple input multiple output (MIMO) decoding system comprising:

• a look-up table comprising distance information corresponding to a distance between a potential candidate symbol and a most proximate competing symbol for each bit of a plurality of potential candidate symbols;
• and
• a MIMO decoder configured to:
• receive a plurality of candidate symbols that are provided in a maximum likelihood solution and correspond to a plurality of antenna layers of a MIMO wireless communication system;
• select a first candidate symbol from the plurality of candidate symbols, wherein the first candidate symbol corresponds to a first potential candidate symbol of the plurality of candidate symbols;
• obtain the distance information for each bit of the first potential candidate symbol from the look-up table;
• determine likelihood indicium for each bit of the first candidate symbol as a function of the distance information for each bit of the first potential candidate symbol, wherein the likelihood indicium for a given bit is indicative of a likelihood that a value for the given bit is a logic 1 or a logic 0;
• determine a product of a maximum likelihood solution vector comprising the plurality of candidate signals and an overall channel matrix;
• and
• subtract the product from the received signal vector to determine a residual noise vector, wherein the likelihood indicium for each bit is a further function of the residual noise vector.