Radio apparatus and metric calculation method

摘要

A subtraction section subtracts from a received signal point a replica obtained by reflecting an influence of a propagation path state in a likely transmitted signal point. A calculation section calculates a metric for the received signal point and the replica from a value which the subtraction section calculates by subtracting the replica from the received signal point by the use of a linear interpolation formula obtained by separating a quadratic function at a power of 2.

主权项

1. A radio apparatus for performing radio communication by the use of a plurality of antennas, the apparatus comprising:
a subtraction section which subtracts from a received signal point a replica obtained by reflecting an influence of a propagation path state in a likely transmitted signal point; and a calculation section which calculates a metric for the received signal point and the replica from a value calculated by the subtraction section by the use of a linear interpolation formula obtained by separating a quadratic function at a power of 2; wherein: the linear interpolation formula is given by
2n-1{|x|+2(|x|−2n-1)} where x is the value calculated by the subtraction section and n is a number of digits of the x; and the calculation section includes:
an absolute value calculator which calculates |x| of the x;a detector which detects the n from the |x|;an extractor which extracts lowest (n−1) bits from the |x| and which outputs (|x|−2n-1);a first shifter which performs a bit shift on the (|x|−2n-1) and which outputs 2(|x|−2n-1);an adder which adds the |x| and the 2(|x|−2n-1) to calculate {|x|+2(|x|−2n-1)}; anda second shifter which performs a bit shift on the {|x|+2(|x|−2n-1)} and which outputs 2n-1{|x|+2(|x|−2n-1)}.