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 reception method comprising:
receiving a reception OFDM signal based on a plurality of precoded signals z 1 and z 2 with one or more antennas;
demodulating the reception OFDM signal in accordance with a transmission scheme of the plurality of precoded signals z 1 and z 2 ;
performing error-correction decoding on the demodulated signal; and
acquiring audio data from the error-correction decoded signal, and externally outputting the audio data, wherein
the plurality of precoded signals z 1 and z 2 are transmitted in the same frequency bandwidth at the same time, the plurality of precoded signals z 1 and z 2 are generated by (i) selecting one matrix from among N matrices F[i] by regularly hopping between the N matrices F[i] which are each selected at least once within a predetermined time period and (ii) multiplying the selected matrix by two baseband signals s 1 and s 2 that are represented by in-phase components and quadrature components, where N is an integer 1 or greater, and i is an integer from 0 to N−1, the N matrices F[i] are two-by-two matrices that satisfy a first condition, a second condition, and a third condition,
the first condition is that x is an integer from 0 to N−1, y is an integer from 0 to N−1, and with respect to all x and all y satisfying x≠y, F[x]≠F[y] holds,
the second condition is that x is an integer from 0 to N−1, y is an integer from 0 to N−1, and with respect to all x and all y satisfying x≠y, no real or complex number k holding F[x]=k×F[y] exists,
the third condition is that the plurality of precoded signals z 1 and z 2 are calculated by multiplying the N matrices F[i] and the two baseband signals sl and s 2 , the N matrices F[i] satisfying Equation (1),
F
[
i
]
=
1
α
2
+
1
(
ⅇ
j
θ
11
(
i
)
α
×
ⅇ
j
(
θ
11
(
i
)
+
λ
)
α
×
ⅇ
j
θ
21
(
i
)
ⅇ
j
(
θ
21
(
i
)
+
λ
+
δ
)
)
(
1
)
where, α is a positive real number,
θ 11 (i) and θ 21 (i) each indicate a phase rotation amount [radian] for a symbol number Ni,
λ indicates a phase rotation amount [radian],
δ indicates a phase rotation amount [radian], and
j is an imaginary unit.
2. The reception method of claim 1 , further comprising
detecting, from the reception OFDM signal, control information for notifying of the transmission scheme of the plurality of precoded signals z 1 and z 2 , wherein
the demodulation of the reception OFDM signal is based on the control information.
3. The reception method of claim 1 , wherein
the two baseband signals s 1 and s 2 are the same signals.
4. A reception apparatus comprising:
an receiver that receives a reception OFDM signal based on a plurality of precoded signals z 1 and z 2 with one or more antennas;
a demodulator that demodulates the reception OFDM signal in accordance with a transmission scheme of the plurality of precoded signals z 1 and z 2 ;
a decoder that performs error-correction decoding on the demodulated signal; and
an audio output that acquires audio data from the error-correction decoded signal, and externally outputs the audio data, wherein
the plurality of precoded signals z 1 and z 2 are transmitted in the same frequency bandwidth at the same time, and the plurality of precoded signals z 1 and z 2 are generated by (i) selecting one matrix from among N matrices F[i] by regularly hopping between the N matrices F[i] which are each selected at least once within a predetermined time period and (ii) multiplying the selected matrix by two baseband signals sl and s 2 that are represented by in-phase components and quadrature components, where N is an integer 1 or greater, and i is an integer from 0 to N−1, the N matrices F[i] are two-by-two matrices that satisfy a first condition, a second condition, and a third condition,
the first condition is that x is an integer from 0 to N−1, y is an integer from 0 to N−1, and with respect to all x and all y satisfying x≠y, F[x]≠F[y] holds,
the second condition is that x is an integer from 0 to N−1, y is an integer from 0 to N−1, and with respect to all x and all y satisfying x≠y, no real or complex number k holding F[x]=k×F[y] exists,
the third condition is that the plurality of precoded signals z 1 and z 2 are calculated by multiplying the N matrices F[i] and the two baseband signals s 1 and s 2 , the N matrices F[i] satisfying Equation (2),
F
[
i
]
=
1
α
2
+
1
(
ⅇ
j
θ
11
(
i
)
α
×
ⅇ
j
(
θ
11
(
i
)
+
λ
)
α
×
ⅇ
j
θ
21
(
i
)
ⅇ
j
(
θ
21
(
i
)
+
λ
+
δ
)
)
(
2
)
where, α is a positive real number, and β≠1,
θ 11 (Ni) and θ 21 (Ni) each indicate a phase rotation amount [radian] for a symbol number Ni,
λ indicates a phase rotation amount [radian],
δ indicates a phase rotation amount [radian], and
j is an imaginary unit.
5. The reception apparatus of claim 4 , further comprising
a detector that detects, from the reception OFDM signal, control information for notifying of the transmission scheme of the plurality of precoded signals z 1 and z 2 , wherein the demodulator demodulates the reception OFDM signal based on the control information.
6. The reception apparatus of claim 4 , wherein
the two baseband signals s 1 and s 2 are the same signals.