Precoding method, transmitting device, and receiving device
A transmission scheme for transmitting a first modulated signal and a second modulated signal in the same frequency at the same time. According to the transmission scheme, a precoding weight multiplying unit multiplies a precoding weight by a baseband signal after a first mapping and a baseband signal after a second mapping and outputs the first modulated signal and the second modulated signal. In the precoding weight multiplying unit, precoding weights are regularly hopped.
1. A transmission device comprising:
modulation circuitry configured to generate two modulated signals to be demodulated by a reception device, the modulation circuitry generating the two modulated signals by modulating two data sequences by using a modulation scheme selected from among a plurality of modulation schemes;
precoding circuitry configured to generate two precoded signals by performing phase change on the two modulated signals while switching between precoding matrices in accordance with Equation 1;
power adjustment circuitry configured to generate two amplitude-changed signals by changing the amplitudes of the two precoded signals; and
transmission circuitry configured to transmit the two amplitude-changed signals from different antennas at a same frequency and at a same time, wherein
Equation 1 is expressible as:
F
[
i
]
=
1
2
(
e
j
θ
11
(
i
)
e
j
(
θ
11
(
i
)
+
λ
)
e
j
θ
21
(
i
)
e
j
(
θ
21
(
i
)
+
λ
+
π
)
)
,
and
Equation 1 satisfies Equation 2, Equation 2 expressible as:
e
j
(
θ
11
(
x
+
1
)
-
θ
21
(
x
+
1
)
)
e
j
(
θ
11
(
x
)
-
θ
21
(
x
)
)
=
e
j
(
π
N
)
for
∀
x
(
x
=
0
,
1
,
2
,
…
,
N
-
2
)
,
where N=2, λ=0, θ 11 (i) and θ 21 (i) are each a real number equal to or more than 0 and less than 2π, i is an integer equal to or more than 0 and equal to or less than N−1, and π is a circular constant.
2. A transmission method comprising:
generating two modulated signals to be demodulated by a reception device, the two modulated signals being generated by modulating two data sequences by using a modulation scheme selected from among a plurality of modulation schemes;
generating two precoded signals by performing phase change on the two modulated signals while switching between precoding matrices in accordance with Equation 3;
generating two amplitude-changed signals by changing the amplitudes of the two precoded signals; and
transmitting the two amplitude-changed signals from different antennas at a same frequency and at a same time, wherein
Equation 3 is expressible as:
F
[
i
]
=
1
2
(
e
j
θ
11
(
i
)
e
j
(
θ
11
(
i
)
+
λ
)
e
j
θ
21
(
i
)
e
j
(
θ
21
(
i
)
+
λ
+
π
)
)
,
and
Equation 3 satisfies Equation 4, Equation 4 expressible as:
e
j
(
θ
11
(
x
+
1
)
-
θ
21
(
x
+
1
)
)
e
j
(
θ
11
(
x
)
-
θ
21
(
x
)
)
=
e
j
(
π
N
)
for
∀
x
(
x
=
0
,
1
,
2
,
…
,
N
-
2
)
,
where N=2, λ=0, θ 11 (i) and θ 21 (i) are each a real number equal to or more than 0 and less than 2π, i is an integer equal to or more than 0 and equal to or less than N−1, and π is a circular constant.
3. A reception device comprising:
reception circuitry configured to receive a reception signal transmitted from two different antennas of a transmission device, the reception signal including two precoded signals; and
demodulation circuitry configured to demodulate the reception signal to output two data sequences by using a modulation scheme selected from among a plurality of modulation schemes, wherein
the transmission device transmits the two precoded signals by:
generating two modulated signals by modulating two data sequences by using the selected modulation scheme;
generating the two precoded signals by performing phase change on the two modulated signals while switching between precoding matrices in accordance with Equation 5;
generating two amplitude-changed signals by changing the amplitudes of the two precoded signals; and
transmitting the two amplitude-changed signals from different antennas at a same frequency and at a same time, wherein
Equation 5 is expressible as:
F
[
i
]
=
1
2
(
e
j
θ
11
(
i
)
e
j
(
θ
11
(
i
)
+
λ
)
e
j
θ
21
(
i
)
e
j
(
θ
21
(
i
)
+
λ
+
π
)
)
,
and
Equation 5 satisfies Equation 6, Equation 6 expressible as:
e
j
(
θ
11
(
x
+
1
)
-
θ
21
(
x
+
1
)
)
e
j
(
θ
11
(
x
)
-
θ
21
(
x
)
)
=
e
j
(
π
N
)
for
∀
x
(
x
=
0
,
1
,
2
,
…
,
N
-
2
)
,
where N=2, λ=0, θ 11 (i) and θ 21 (i) are each a real number equal to or more than 0 and less than 2π, i is an integer equal to or more than 0 and equal to or less than N−1, and π is a circular constant.
4. A reception method comprising:
receiving a reception signal transmitted from two different antennas of a transmission device, the reception signal including two precoded signals; and
demodulating the reception signal to output two data sequences by using a modulation scheme selected from among a plurality of modulation schemes, wherein
the transmission device transmits the two precoded signals by:
generating two modulated signals by modulating two data sequences by using the selected modulation scheme;
generating the two precoded signals by performing phase change on the two modulated signals while switching between precoding matrices in accordance with Equation 7;
generating two amplitude-changed signals by changing the amplitudes of the two precoded signals; and
transmitting the two amplitude-changed signals from different antennas at a same frequency and at a same time, wherein
Equation 7 is expressible as:
F
[
i
]
=
1
2
(
e
j
θ
11
(
i
)
e
j
(
θ
11
(
i
)
+
λ
)
e
j
θ
21
(
i
)
e
j
(
θ
21
(
i
)
+
λ
+
π
)
)
,
and
Equation 7 satisfies Equation 8, Equation 8 expressible as:
e
j
(
θ
11
(
x
+
1
)
-
θ
21
(
x
+
1
)
)
e
j
(
θ
11
(
x
)
-
θ
21
(
x
)
)
=
e
j
(
π
N
)
for
∀
x
(
x
=
0
,
1
,
2
,
…
,
N
-
2
)
,
where N=2, λ=0, θ 11 (i) and θ 21 (i) are each a real number equal to or more than 0 and less than 2π, i is an integer equal to or more than 0 and equal to or less than N−1, and π is a circular constant.