Patent ID: 8243842

Claim:
A signal demultiplexing apparatus that is used in a wireless receiving apparatus of a multi-input and multi-output scheme and that carries out signal demultiplexing in two stages according to a maximum likelihood detection scheme, the signal demultiplexing apparatus comprising: a channel matrix rearranging section that generates a second channel estimation matrix by rearranging rows of a first channel estimation matrix; a decomposition section that performs QR decomposition using the first and second channel estimation matrices and calculates a unitary matrix and a triangular matrix of each of the first and second channel estimation matrices; a multiplying section that multiplies a conjugate transpose matrix of the unitary matrix and a received signal for each of the first and second channel estimation matrices and calculates a first received signal after orthogonalization and a second received signal after orthogonalization; a maximum likelihood detection section that: calculates a distance using a first transmission signal candidate and the first received signal after orthogonalization in a first stage for each first transmission signal candidate; determines a second transmission signal candidate by performing threshold decision for each first transmission signal candidate in a second stage and, further, calculates, for each first transmission signal candidate, a distance using the first transmission signal candidate, the second received signal after orthogonalization and the second transmission signal candidate determined with respect to the first transmission signal candidate; and adds the distance calculated in the first stage and the distance calculated in the second stage for each first transmission signal candidate and outputs an addition result associated in a one-to-one correspondence with each first transmission signal candidate; and a log likelihood ratio calculating section that selects from the addition result a shortest distance in case where a bit of the first transmission signal candidate is zero and a shortest distance in case where the bit of the first transmission signal candidate is one and calculates a log likelihood ratio based on the selected shortest distance in case where the bit is zero and the selected shortest distance in case where the bit is one.