Signal generation method, transmission device, reception method, and reception device
A signal generation method is used in a transmission device that transmits a plurality of transmission signals from a plurality of antennas at the same frequency and at the same time, in the case where larger power change is performed on a first transmission signal than on a second transmission signal during generation process of the first transmission signal and the second transmission signal, the first transmission signal and the second transmission signal are mapped before the power change such that a minimum Euclidian distance between possible signal points for the first signal is longer than a minimum Euclidian distance between possible signal points for the second signal.
1. A signal generation method for use in a transmission device, the signal generation method comprising:
generating a first modulated signal s 1 (i) from first transmission data of g bits, and generating a second modulated signal s 2 (i) from second transmission data of h bits;
generating a first signal z 1 (i) and a second signal z 2 (i) that satisfy formula from the first modulated signal s 1 (i) and the second modulated signal s 2 (i), the generating of the first modulated signal s 1 (i), the second modulated signal s 2 (i), the first signal z 1 (i) and the second signal z 2 (i) being performed by the transmitting device; and
transmitting, using the transmission device, a plurality of transmission signals from a plurality of antennas at the same frequency and at the same time,
(
z
1
(
i
)
z
2
(
i
)
)
=
1
α
2
+
1
(
Q
1
0
0
Q
2
)
(
e
j
0
α
×
e
j
0
α
×
e
j
0
e
j
π
)
(
s
1
(
i
)
s
2
(
i
)
)
(
formula
)
where α denotes an arbitrary complex number other than zero, j denotes an imaginary unit, and Q 1 and Q 2 each denote a real number and satisfy Q 1 >Q 2 , and
when a third signal u 1 (i) and a fourth signal u 2 (i) are defined such that z 1 (i)=Q 1 ×u 1 (i) and z 2 (i)=Q 2 ×u 2 (i) are satisfied,
D 1 >D 2 is satisfied, where D 1 represents a minimum Euclidian distance between possible signal points for the third signal u 1 (i) in an I (in-phase)-Q (quadrature) plane, and D 2 represents a minimum Euclidian distance between possible signal points for the fourth signal u 2 (i) in an I (in-phase)-Q (quadrature) plane.
2. A transmission device that transmits a plurality of transmission signals, the transmission device comprising:
a mapper generating a first modulated signal s 1 (i) from first transmission data of g bits, and generating a second modulated signal s 2 (i) from second transmission data of h bits;
a weighting unit generating a first signal z 1 (i) and a second signal z 2 (i) that satisfy formula from the first modulated signal s 1 (i) and the second modulated signal s 2 (i); and
a plurality of antennas for transmitting the plurality of transmission signals at the same frequency and at the same time,
(
z
1
(
i
)
z
2
(
i
)
)
=
1
α
2
+
1
(
Q
1
0
0
Q
2
)
(
e
j
0
α
×
e
j
0
α
×
e
j
0
e
j
π
)
(
s
1
(
i
)
s
2
(
i
)
)
(
formula
)
where α denotes an arbitrary complex number other than zero, j denotes an imaginary unit, and Q 1 and Q 2 each denote a real number and satisfy Q 1 >Q 2 , and
when a third signal u 1 (i) and a fourth signal u 2 (i) are defined such that z 1 (i)=Q 1 ×u 1 (i) and z 2 (i)=Q 2 ×u 2 (i) are satisfied,
D 1 >D 2 is satisfied, where D 1 represents a minimum Euclidian distance between possible signal points for the third signal u 1 (i) in an I (in-phase)-Q (quadrature) plane, and D 2 represents a minimum Euclidian distance between possible signal points for the fourth signal u 2 (i) in an I (in-phase)-Q (quadrature) plane.
3. A reception method comprising:
acquiring, using an acquirer, reception signals obtained by receiving a first transmission signal and a second transmission signal that are transmitted from a plurality of antennas at the same frequency and at the same time, the first transmission signal and the second transmission signal being generated by applying a predetermined generation process; and
demodulating, using a demodulator, the reception signals according to the predetermined generation process to obtain reception data,
the predetermined generation process includes:
generating a first modulated signal s 1 (i) from first transmission data of g bits, and generating a second modulated signal s 2 (i) from second transmission data of h bits; and
generating a first signal z 1 (i) and a second signal z 2 (i) that satisfy formula from the first modulated signal s 1 (i) and the second modulated signal s 2 (i),
(
z
1
(
i
)
z
2
(
i
)
)
=
1
α
2
+
1
(
Q
1
0
0
Q
2
)
(
e
j
0
α
×
e
j
0
α
×
e
j
0
e
j
π
)
(
s
1
(
i
)
s
2
(
i
)
)
(
formula
)
where α denotes an arbitrary complex number other than zero, j denotes an imaginary unit, and Q 1 and Q 2 each denote a real number and satisfy Q 1 >Q 2 , and
when a third signal u 1 (i) and a fourth signal u 2 (i) are defined such that z 1 (i)=Q 1 ×u 1 (i) and z 2 (i)=Q 2 ×u 2 (i) are satisfied,
D 1 >D 2 is satisfied, where D 1 represents a minimum Euclidian distance between possible signal points for the third signal u 1 (i) in an I (in-phase)-Q (quadrature) plane, and D 2 represents a minimum Euclidian distance between possible signal points for the fourth signal u 2 (i) in an I (in-phase)-Q (quadrature) plane.
4. A reception device comprising:
an acquirer for acquiring reception signals obtained by receiving a first transmission signal and a second transmission signal that are transmitted from a plurality of antennas at the same frequency and at the same time, the first transmission signal and the second transmission signal being generated by applying a predetermined generation process; and
a demodulator for demodulating the reception signals according to the predetermined generation process to obtain reception data,
the predetermined generation process includes:
generating a first modulated signal s 1 (i) from first transmission data of g bits, and generating a second modulated signal s 2 (i) from second transmission data of h bits; and
generating a first signal z 1 (i) and a second signal z 2 (i) that satisfy formula from the first modulated signal s 1 (i) and the second modulated signal s 2 (i),
(
z
1
(
i
)
z
2
(
i
)
)
=
1
α
2
+
1
(
Q
1
0
0
Q
2
)
(
e
j
0
α
×
e
j
0
α
×
e
j
0
e
j
π
)
(
s
1
(
i
)
s
2
(
i
)
)
(
formula
)
where α denotes an arbitrary complex number other than zero, j denotes an imaginary unit, and Q 1 and Q 2 each denote a real number and satisfy Q 1 >Q 2 , and
when a third signal u 1 (i) and a fourth signal u 2 (i) are defined such that z 1 (i)=Q 1 ×u 1 (i) and z 2 (i)=Q 2 ×u 2 (i) are satisfied,
D 1 >D 2 is satisfied, where D 1 represents a minimum Euclidian distance between possible signal points for the third signal u 1 (i) in an I (in-phase)-Q (quadrature) plane, and D 2 represents a minimum Euclidian distance between possible signal points for the fourth signal u 2 (i) in an I (in-phase)-Q (quadrature) plane.