Signal generating method and signal generating apparatus
View Patent ↗A transmission method for simultaneously transmitting a first modulated signal and a second modulated signal at the same frequency includes performing precoding on both signals using a fixed precoding matrix and regularly changing the phase of at least one of the signals. In this method, the power ratio between a plurality of signals transmitted from a plurality of antennas at the same frequency and at the same time differs from the power ratio between a plurality of pilot signals transmitted from the plurality of antennas at the same frequency and at the same time, whereby the accuracy of channel estimation by a reception device is improved.
1. A signal generation method for generating, from a plurality of baseband signals, a plurality of signals to be transmitted from a plurality of antennas at the same frequency and at the same time, and for generating a plurality of pilot signals to be transmitted from the plurality of antennas at the same frequency and at the same time, the method comprising:
generating a first baseband signal s 1 from a first set of bits, and generating a second baseband signal s 2 from a second set of bits;
performing phase change on each of the first baseband signal s 1 and the second baseband signal s 2 , this generating a first phase-changed baseband signal s 1 ′ and a second phase-changed baseband signal s 2 ′;
applying weighting according to a predetermined matrix F to the first phase-changed baseband signal s 1 ′ and the second phase-changed baseband signal s 2 ′, thus generating a first weighted signal z 1 and a second weighted signal z 2 ;
performing power change on the first weighted signal z 1 and the second weighted signal z 2 , thus generating a first power-changed signal z 1 ′ and a second power-changed signal z 2 ′ as the plurality of signals to be transmitted at the same frequency and at the same time; and
generating a first pilot signal p 1 and a second pilot signal p 2 , the first pilot signal p 1 being a pilot signal to be transmitted from the same antenna as the first power-changed signal z 1 ′, and the second pilot signal p 2 being a pilot signal to be transmitted from the same antenna as the second power-changed signal z 2 ′, wherein
the first weighted signal z 1 and the second weighted signal z 2 satisfy the relation:
( z 1, z 2) T =F ( s 1′, s 2′) T ,
(z 1 , z 2 ) T being a transposed vector of (z 1 , z 2 ),
(s 1 ′, s 2 ) T being a transposed vector of (s 1 ′, s 2 ′), and
a ratio of an average power of the first power-changed signal z 1 ′ to an average power of the second power-changed signal z 2 ′ differs from a ratio of an average power of the first pilot signal p 1 to an average power of the second pilot signal p 2 .
2. An apparatus for generating, front a plurality of baseband signals, a plurality of signals to be transmitted from a plurality of antennas at the same frequency and at the same time, and for generating a plurality of pilot signals to be transmitted from the plurality of antennas at the same frequency and at the same time, the apparatus comprising:
a mapper generating a first baseband signal s 1 from a first set of bits, and generating a second baseband signal s 2 from a second set of bits;
a phase changer performing phase change on each of the first baseband signal s 1 and the second baseband signal s 2 , thus generating a first phase-changed baseband signal s 1 ′ and a second phase-changed baseband signal s 2 ′;
a weighting unit applying weighting according to a predetermined matrix F to the first phase-changed baseband signal s 1 ′ and the second phase-changed baseband signal s 2 ′, thus generating a first weighted signal z 1 and a second weighted signal z 2 ;
a power changer performing power change on the first weighted signal z 1 and the second weighted signal z 2 , thus generating a first power-changed signal z 1 ′ and a second power-changed signal z 2 ′ as the plurality of signals to be transmitted at the same frequency and at the same time; and
a pilot inserter generating a first pilot signal p 1 and a second pilot signal p 2 , the first pilot signal p 1 being a pilot signal to be transmitted from the same antenna as the first power-changed signal z 1 ′, and the second pilot signal p 2 being a pilot signal to be transmitted from the same antenna as the second power-changed signal z 2 wherein
the first weighted signal z 1 and the second weighted signal z 2 satisfy the relation:
( z 1, z 2) T =F ( s 1′, s 2′) T ,
(z 1 , z 2 ) T being a transposed vector of (z 1 , z 2 ),
(s 1 ′, s 2 ′) T being a transposed vector of (s 1 ′, s 2 ′), and
a ratio of an average power of the first power-changed signal z 1 ′ to an average power of the second power-changed signal z 2 ′ differs from a ratio of an average power of the first pilot signal p 1 to an average power of the second pilot signal p 2 .