Patent ID: 7421035

Claim:
A multiple input, multiple output communication apparatus, comprising: a receiver comprising a number M r of receive antennas, wherein the receiver is operable to receive through a communication channel a signal represented by an M r -dimensional vector r from a number M t of transmit antennas operable to transmit a number B*M t of bits in a channel period in a signaling constellation, wherein each component of the vector r corresponds to a respective signal received by a respective one of the receive antennas; and a decoder comprising logic circuitry operable to: compute an M t -dimensional vector x sub representing a sub-optimal reconstruction of the transmitted set of symbols; for each component x sub,k of the vector x sub , select a corresponding plurality of constellation points to be searched, the plurality of constellation points making up a set X k of nearest neighbor constellation points, wherein fewer than all of the constellation points in the signaling constellation are included in the set X k ; for a combination of constellation points formed by selecting one of the plurality of nearest neighbor constellation points from the set X k for each of the transmit antennas k, compute a residual error d using the received signal r and the constellation points in the combination; and compute from the residual error d a metric L(k,j) for a transmitted bit b j sent by a transmit antenna k.