A base station apparatus comprising: a transmitter configured to transmit, to a terminal, control information, which determines an orthogonal sequence associated with each of a plurality of layer numbers, the orthogonal sequence being one of a plurality of orthogonal sequences corresponding to a first orthogonal sequence [1, 1] and a second orthogonal sequence [1, -1]; and a receiver configured to receive a reference signal, which is generated using the orthogonal sequence determined based on the control information and which is transmitted from the terminal, characterized in that the layer numbers correspond to a first layer, a second layer, a third layer and a fourth layer, and the reference signal is generated using the orthogonal sequence, which is associated with each of the layer numbers by one of a plurality of associations where Nw is a positive integer, the plurality of associations including: (i) a first association for Nw=2, in which the first layer and the second layer are associated with the first orthogonal sequence, and the third layer and the fourth layer are associated with the second orthogonal sequence; (ii) a second association for Nw=2, in which the first layer and the second layer are associated with the second orthogonal sequence, and the third layer and the fourth layer are associated with the first orthogonal sequence; (iii) a third association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the first orthogonal sequence; and (iv) a fourth association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the second orthogonal sequence. a transmitter configured to transmit, to a terminal, control information, which determines an orthogonal sequence associated with each of a plurality of layer numbers, the orthogonal sequence being one of a plurality of orthogonal sequences corresponding to a first orthogonal sequence [1, 1] and a second orthogonal sequence [1, -1]; and a receiver configured to receive a reference signal, which is generated using the orthogonal sequence determined based on the control information and which is transmitted from the terminal, characterized in that the layer numbers correspond to a first layer, a second layer, a third layer and a fourth layer, and the reference signal is generated using the orthogonal sequence, which is associated with each of the layer numbers by one of a plurality of associations where Nw is a positive integer, the plurality of associations including: (i) a first association for Nw=2, in which the first layer and the second layer are associated with the first orthogonal sequence, and the third layer and the fourth layer are associated with the second orthogonal sequence; (ii) a second association for Nw=2, in which the first layer and the second layer are associated with the second orthogonal sequence, and the third layer and the fourth layer are associated with the first orthogonal sequence; (iii) a third association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the first orthogonal sequence; and (iv) a fourth association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the second orthogonal sequence. (i) a first association for Nw=2, in which the first layer and the second layer are associated with the first orthogonal sequence, and the third layer and the fourth layer are associated with the second orthogonal sequence; (ii) a second association for Nw=2, in which the first layer and the second layer are associated with the second orthogonal sequence, and the third layer and the fourth layer are associated with the first orthogonal sequence; (iii) a third association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the first orthogonal sequence; and (iv) a fourth association for Nw=4, in which all layers including the first layer, the second layer, the third layer and the fourth layer are associated with the second orthogonal sequence.