Patent ID: 7822151

Claim:
A receiving apparatus that receives a modulated signal transmitted from a transmitting apparatus, said receiving apparatus comprising: a channel fluctuation estimation section that finds a channel estimate of each modulated signal; and a Euclidian distance calculation section that has said channel estimate and said received signal as input, finds a candidate signal point from said channel estimate, and calculates an approximation of a Euclidian distance between said candidate signal point and said received signal using a bit shift and an adder, wherein: said Euclidian distance calculation section: outputs a Euclidian distance approximation as |y| when a size relationship of an I-direction distance x and Q-direction distance y for said candidate signal point and said reception signal point on an IQ plane is |x|<|y| and is also 0<|x|<|y|×(¼+⅛), outputs a Euclidian distance approximation as |y|×(1+⅛) when said size relationship is |x|<|y| and is also|y|×(¼+⅛)<|x|<|y|×(½+⅛), outputs a Euclidian distance approximation as |y|×(1+¼) when said size relationship is |x|<|y| and is also |y|×(½+⅛)<|x|<|y|×(½+¼+⅛), and outputs a Euclidian distance approximation as |y|×(1+¼+⅛) when said size relationship is |x|<|y| and is also |y|×(½+¼+⅛)<|x|.