Signal generating method and signal generating device
A transmission method for transmitting a first modulated signal and a second modulated signal in the same frequency at the same time. Each signal has been modulated according to a different modulation scheme. The transmission method applies precoding on both signals using a fixed precoding matrix, applies different power change to each signal, and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.
1. A transmission signal generating method comprising:
applying precoding to a first modulated signal s1(i) and a second modulated signal s2(i) to generate a first precoded signal z′1(i) and a second precoded signal z′2(i), the first modulated signal s1(i) having been acquired by modulating, by a first modulation scheme at a modulation level denoted by a, data encoded by using a first error-correcting code of a first coding rate, the second modulated signal s2(i) having been acquired by modulating, by a second modulation scheme at a modulation level denoted by b, data encoded by using a second error-correcting code of a second coding rate, a and b being integers satisfying a<b, i being an integer more than 0;
performing a phase change on at least one of the first precoded signal z′1(i) and the second precoded signal z′2(i) to generate a first transmission signal z1(i) and a second transmission signal z2(i); and
outputting the first transmission signal z1(i) and the second transmission signal z2(i) respectively to be transmitted from a first antenna and a second antenna at the same time at the same frequency, the first transmission signal z1(i) and the second transmission signal z2(i) include respectively an information symbol regarding the first modulation scheme and the second modulation scheme,
the precoding being represented by a precoding matrix
F
(
i
)
=
1
(
α
2
+
1
)
[
ⅇ
j0
α
×
ⅇ
j
o
α
×
ⅇ
j0
ⅇ
j
k
ⅈ
]
where α=0, k being a real number greater than 0 and less than 2,
k in the precoding matrix being changed each time at least one of the first modulation scheme, the second modulation scheme, the first error-correcting code, the second error-correcting code, the first coding rate, and the second coding rate is changed, and
the transmission signal generating method further comprising:
performing a power change involving multiplication by a weighting factor u a and multiplication by a weighting factor u b , the weighting factor u a being used for the generation of the first transmission signal z1(i) from the first modulated signal s1(i), the weighting factor u b being used for the generation of the second transmission signal z2(i) from the second modulated signal s2(i), and the weighting factor u a and the weighting factor u b satisfying u a <u b .
2. A transmission signal generating apparatus comprising:
weighting circuitry which, in operation, applies precoding to a first modulated signal s1(i) and a second modulated signal s2(i) to generate a first precoded signal z′1(i) and a second precoded signal z′2(i), i being an integer more than 0,
phase changing circuitry which, in operation, performs a phase change on at least one of the first precoded signal z′1(i) and the second precoded signal z′2(i) to generate a first transmission signal z1(i) and a second transmission signal z2(i); and
an output terminal which, in operation, outputs the first transmission signal z1(i) and the second transmission signal z2(i) respectively to be transmitted from a first antenna and a second antenna at the same time at the same frequency, the first transmission signal z1(i) and the second transmission signal z2(i) include respectively an information symbol regarding the first modulation scheme and the second modulation scheme,
the first modulated signal s1(i) having been acquired by modulating, by a first modulation scheme at a modulation level denoted by a, data encoded by using a first error-correcting code of a first coding rate, the second modulated signal s2(i) having been acquired by modulating, by a second modulation scheme at a modulation level denoted by b, data encoded by using a second error-correcting code of a second coding rate,
the precoding being represented by a precoding matrix
F
(
i
)
=
1
(
α
2
+
1
)
[
ⅇ
j0
α
×
ⅇ
j
o
α
×
ⅇ
j0
ⅇ
j
k
ⅈ
]
where α=0, k being a real number greater than 0 and less than 2,
k in the precoding matrix being changed each time at least one of the first modulation scheme, the second modulation scheme, the first error-correcting code, the second error-correcting code, the first coding rate, and the second coding rate is changed, and
the transmission signal generating apparatus further comprising:
power changing circuitry which, in operation, performs a power change involving multiplication by a weighting factor u a and multiplication by a weighting factor u b , the weighting factor u a being used for the generation of the first transmission signal z1(i) from the first modulated signal s1(i), the weighting factor u b being used for the generation of the second transmission signal z2(i) from the second modulated signal s2(i), and the weighting factor u a and the weighting factor u b satisfying u a <u b .
3. A reception signal generating method comprising:
inputting a reception signal obtained by receiving a first transmission signal z1(i) and a second transmission signal z2(i) respectively transmitted from a first antenna and a second antenna at the same time at the same frequency, the first transmission signal z1(i) and the second transmission signal z2(i) having been generated by a predetermined generation process, the first transmission signal z1(i) and the second transmission signal z2(i) include respectively an information symbol regarding a first modulation scheme and a second modulation scheme, i an being integer more than 0; and
obtaining reception data by applying a demodulation process corresponding to the predetermined generation process to the reception signal based on the information symbol,
the predetermined generation process including:
applying precoding to a first modulated signal s1(i) and a second modulated signal s2(i) to generate a first precoded signal z′1(i) and a second precoded signal z′2(i); and
performing a phase change on at least one of the first precoded signal z′1(i) and the second precoded signal z′2(i) to generate the first transmission signal z1(i) and the second transmission signal z2(i),
the first modulated signal s1 having been acquired by modulating, by a first modulation scheme at a modulation level denoted by a, data encoded by using a first error-correcting code of a first coding rate, the second modulated signal s2(i) having been acquired by modulating, by a second modulation scheme at a modulation level denoted by b, data encoded by using a second error-correcting code of a second coding rate,
the precoding being represented by a precoding matrix
F
(
i
)
=
1
(
α
2
+
1
)
[
ⅇ
j0
α
×
ⅇ
j
o
α
×
ⅇ
j0
ⅇ
j
k
ⅈ
]
where α=0, k being a real number greater than 0 and less than 2,
k in the precoding matrix being changed each time at least one of the first modulation scheme, the second modulation scheme, the first error-correcting code, the second error-correcting code, the first coding rate, and the second coding rate is changed, and
the predetermined generation process further including:
performing a power change involving multiplication by a weighting factor u a and multiplication by a weighting factor u b , the weighting factor u a being used for the generation of the first transmission signal z1(i) from the first modulated signal s1(i), the weighting factor u b being used for the generation of the second transmission signal z2(i) from the second modulated signal s2(i), and the weighting factor u a and the weighting factor u b satisfying u a <u b .
4. A reception signal generating apparatus comprising:
an input terminal which, in operation, acquires a reception signal obtained by receiving a first transmission signal z1(i) and a second transmission signal z2(i) respectively transmitted from a first antenna and a second antenna at the same time at the same frequency, the first transmission signal z1(i) and the second transmission signal z2(i) having been generated by a predetermined generation process, the first transmission signal z1(i) and the second transmission signal z2(i) include respectively an information symbol regarding a first modulation scheme and a second modulation scheme, i being an integer more than 0; and
demodulation circuitry which, in operation, obtains reception data by applying a demodulation process corresponding to the predetermined generation process to the reception signal based on the information symbol,
the predetermined generation process including:
applying precoding to a first modulated signal s1(i) and a second modulated signal s2(i) to generate a first precoded signal z′1(i) and a second precoded signal z′2(i); and
performing a phase change on at least one of the first precoded signal z′1(i) and the second precoded signal z′2(i) to generate the first transmission signal z1(i) and the second transmission signal z2(i),
the first modulated signal s1(i) having been acquired by modulating, by a first modulation scheme at a modulation level denoted by a, data encoded by using a first error-correcting code of a first coding rate, the second modulated signal s2(i) having been acquired by modulating, by a second modulation scheme at a modulation level denoted by b, data encoded by using a second error-correcting code of a second coding rate,
the precoding being represented by a precoding matrix
F
(
i
)
=
1
(
α
2
+
1
)
[
ⅇ
j0
α
×
ⅇ
j
o
α
×
ⅇ
j0
ⅇ
j
k
ⅈ
]
where α=0, k being a real number greater than 0 and less than 2,
k in the precoding matrix being changed each time at least one of the first modulation scheme, the second modulation scheme, the first error-correcting code, the second error-correcting code, the first coding rate, and the second coding rate is changed, and
the predetermined generation process further including:
performing a power change involving multiplication by a weighting factor u a and multiplication by a weighting factor u b , the weighting factor u a being used for the generation of the first transmission signal z1(i) from the first modulated signal s1(i), the weighting factor u b being used for the generation of the second transmission signal z2(i) from the second modulated signal s2(i) and the weighting factor ua and the weighting factor u b satisfying u a <u b .