Sphere decoding apparatus

A decoding method comprising:

• receiving a codeword comprising a plurality of symbols, each symbol corresponding to at least one of a plurality of candidate constellation points;
• for a first symbol:
• computing a cost metric for each candidate constellation point of said first symbol;
• storing in a memory only those candidate constellation points whose computed cost metrics meet first preferred criteria;
• for each following symbol, and for each candidate constellation point previously stored in said memory for the symbol immediately preceding said following symbol:
• computing a cost metric for each candidate transition from said previously stored candidate constellation point to a candidate constellation point of said following symbol;
• and
• storing in said memory only those candidate transitions whose computed cost metrics meet second preferred criteria.

A decoder apparatus comprising:

• a receiver configured to receive at least one codeword sent over a multiple-input multiple-output (MIMO) channel, wherein the at least one codeword comprises a plurality of layers, each layer comprising a constellation point selected from a plurality of candidate constellation points;
• and
• a processor configured to, for at least one layer, compute a constellation point metric for the at least one layer, and to select preferred constellation points of the at least one layer whose state cost metrics meet first preferred criteria;
• the processor further configured to compute a constellation point cost metric for each transition from a preferred constellation point of the layer to each constellation point of a following layer, and selecting preferred transitions to said following layer whose constellation point cost metrics meet second preferred criteria.

A processor readable media comprising instructions thereon that may be utilized by a processor, the instructions comprising:

• instructions for a first symbol, of a codeword comprising a plurality of symbols, each symbol corresponding to at least one of a plurality of candidate constellation points, computing a cost metric for each candidate constellation point of said first symbol;
• instructions for storing in a memory only those candidate constellation points whose computed cost metrics meet first preferred criteria;
• and
• instructions, for each following symbol and for each candidate constellation point previously stored in said memory for the symbol immediately preceding said following symbol, computing a cost metric for each candidate transition from said previously stored candidate constellation point to a candidate constellation point of said following symbol.