Signal generation method and signal generation device
A transmission method simultaneously transmitting a first modulated signal and a second modulated signal at a common frequency performs precoding on both signals using a fixed precoding matrix and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.
1. A signal generation method for generating, from a plurality of baseband signals, a plurality of signals for transmission on a same frequency band and at a same time, comprising the steps of:
applying a phase change to a first baseband signal generated from a first set of bits and a second baseband signal generated from a second set of bits; and
applying a precoding to the first baseband signal and the second baseband signal according to a predetermined matrix F, wherein
the phase change is continually applied to the first baseband signal and the second baseband signal using a phase change value sequentially selected from among N phase change values, N being an integer greater than two and greater than the number of baseband signals, and each of the N phase change values being selected at least once within a predetermined period, and
a difference between two adjacent phase change values of the N phase change values is 2π/N.
2. The signal generation method according to claim 1 , wherein
the precoding satisfies the relation:
( z 1, z 2) T =F ( s 1, s 2) T
wherein z 1 and z 2 are signals after the precoding, s 1 and s 2 are signals before the precoding, (z 1 , z 2 ) is a row vector composed of the signals z 1 and z 2 , (z 1 , z 2 ) T is a transpose vector of the row vector (z 1 , z 2 ), (s 1 , s 2 ) is a row vector composed of the signals s 1 and s 2 , (s 1 , s 2 ) T is a transpose vector of the row vector (s 1 , s 2 ), and F(s 1 , s 2 ) T is a matrix product of the predetermined matrix F and the transpose vector (s 1 , s 2 ) T .
3. The signal generation method according to claim 1 , wherein the precoding is applied after applying the phase change.
4. The signal generation method according to claim 1 , wherein the phase change is applied after applying the precoding.
5. A signal generation apparatus for generating, from a plurality of baseband signals, a plurality of signals for transmission on a same frequency band and at a same time, comprising:
phase changing circuitry applying a phase change to a first baseband signal generated from a first set of bits and a second baseband signal generated from a second set of bits; and
precoding circuitry applying a precoding to the first baseband signal and the second baseband signal according to a predetermined matrix F, wherein
the phase change is continually applied to the first baseband signal and the second baseband signal using a phase change value sequentially selected from among N phase change values, N being an integer greater than two and greater than the number of baseband signals, each of the N phase change values being selected at least once within a predetermined period, and
a difference between two adjacent phase change values of the N phase change values is 2π/N.
6. The signal generation apparatus according to claim 5 , wherein
the precoding satisfies the relation:
( z 1, z 2) T =F ( s 1, s 2) T
wherein z 1 and z 2 are signals after the precoding, s 1 and s 2 are signals before the precoding, (z 1 , z 2 ) is a row vector composed of the signals z 1 and z 2 , (z 1 , z 2 ) T is a transpose vector of the row vector (z 1 , z 2 ), (s 1 , s 2 ) is a row vector composed of the signals s 1 and s 2 , (s 1 , s 2 ) T is a transpose vector of the row vector (s 1 , s 2 ), and F(s 1 , s 2 ) T is a matrix product of the predetermined matrix F and the transpose vector (s 1 , s 2 ) T .
7. The signal generation apparatus according to claim 5 , wherein the precoding is applied after applying the phase change.
8. The signal generation apparatus according to claim 5 , wherein the phase change is applied after applying the precoding.
9. A signal demodulation method for demodulating a reception signal obtained by receiving a plurality of transmission signals for communication transmitted from different antennas in a same frequency band and at a same time, the signal demodulation method comprising the steps of:
obtaining the reception signal; and
demodulating the reception signal in accordance with a phase change value sequentially selected from among N phase change values, wherein
the transmission signals are generated by applying a phase change to a first baseband signal generated from a first set of bits and a second baseband signal generated from a second set of bits, and applying a precoding to the first baseband signal and the second baseband signal according to a predetermined matrix F,
the phase change is continually applied to the first baseband signal and the second baseband signal using the sequentially selected phase change value, N being an integer greater than two and greater than the number of baseband signals, each of the N phase change values being selected at least once within a predetermined period and
a difference between two adjacent phase change values of the N phase change values is 2π/N.
10. The signal demodulation method according to claim 9 , wherein
the precoding satisfies the relation:
( z 1, z 2) T =F ( s 1, s 2) T
wherein z 1 and z 2 are signals after the precoding, s 1 and s 2 are signals before the precoding, (z 1 , z 2 ) is a row vector composed of the signals z 1 and z 2 , (z 1 , z 2 ) T is a transpose vector of the row vector (z 1 , z 2 ), (s 1 , s 2 ) is a row vector composed of the signals s 1 and s 2 , (s 1 , s 2 ) T is a transpose vector of the row vector (s 1 , s 2 ), and F(s 1 , s 2 ) T is a matrix product of the predetermined matrix F and the transpose vector (s 1 , s 2 ) T .
11. The signal demodulation method according to claim 9 , wherein the precoding is applied after applying the phase change.
12. The signal demodulation method according to claim 9 , wherein the phase change is applied after applying the precoding.
13. A signal demodulation apparatus for demodulating a reception signal obtained by receiving a plurality of transmission signals for communication transmitted from different antennas in a same frequency band and at a same time, the signal demodulation apparatus comprising:
obtaining circuitry obtaining the reception signal; and
demodulating circuitry demodulating the reception signal in accordance with a phase change value sequentially selected from among N phase change values, wherein
the transmission signals are generated by applying a phase change to a first baseband signal generated from a first set of bits and a second baseband signal generated from a second set of bits, and applying a precoding to the first baseband signal and the second baseband signal according to a predetermined matrix F,
the phase change is continually applied to the first baseband signal and the second baseband signal using the sequentially selected phase change value, N being an integer greater than two and greater than the number of baseband signals, each of the N phase change values being selected at least once within a predetermined period, and
a difference between two adjacent phase change values of the N phase change values is 2π/N.
14. The signal demodulation apparatus according to claim 13 , wherein
the precoding satisfies the relation:
( z 1, z 2) T =F ( s 1, s 2) T
wherein z 1 and z 2 are signals after the precoding, s 1 and s 2 are signals before the precoding, (z 1 , z 2 ) is a row vector composed of the signals z 1 and z 2 , (z 1 , z 2 ) T is a transpose vector of the row vector (z 1 , z 2 ), (s 1 , s 2 ) is a row vector composed of the signals s 1 and s 2 , (s 1 , s 2 ) T is a transpose vector of the row vector (s 1 , s 2 ), and F(s 1 , s 2 ) T is a matrix product of the predetermined matrix F and the transpose vector (s 1 , s 2 ) T .
15. The signal demodulation apparatus according to claim 13 , wherein the precoding is applied after applying the phase change.
16. The signal demodulation apparatus according to claim 13 , wherein the phase change is applied after applying the precoding.