Communication apparatus and communication method
Modulated signal A is transmitted from a first antenna, and modulated signal B is transmitted from a second antenna. As modulated signal B, modulated symbols S 2 ( i ) and S 2 ( i +1) obtained from different data are transmitted at time i and time i+1 respectively. In contrast, as modulated signal A, modulated symbols S 1 ( i ) and S 1 ( i )′ obtained by changing the signal point arrangement of the same data are transmitted at time i and time i+1 respectively. As a result the reception quality can be changed intentionally at time i and time i+1, and therefore using the demodulation result of modulated signal A of a time when the reception quality is good enables both modulated signals A and B to be demodulated with good error rate performances.
1. A transmitting apparatus comprising:
a frame configuration section that is configured to select a mapping pattern of a predefined modulation operation from among a first mapping operation having a first pattern and a second mapping operation, which is different from the first mapping operation and which comprises one or more second patterns, and to output a frame configuration signal including information related to the selected mapping pattern;
a modulation section that is configured to output at least one of a plurality of modulated signals, which are mapped using the first mapping operation, as a first modulated signal based solely on the first mapping operation, to re-map the rest of the plurality of modulated signals other than the first modulated signal, which is mapped using the first mapping operation, using the selected mapping pattern included in the frame configuration signal to produce a re-mapped signal, and to output the re-mapped signal as a second modulated signal; and
a plurality of antennas that are configured to transmit the first modulated signal and the second modulated signal, respectively, at the same time period and in the same frequency band, wherein;
the first mapping operation and the second mapping operation are operations for mapping a signal point corresponding to a bit set, which consists of a plurality of bits, on an IQ plane;
a first phase formed between an I axis of the IQ plane and a line drawn between an origin of the IQ plane and a first signal point on the IQ plane, to which a first bit set is mapped using the first mapping operation, is different from a second phase formed between the I axis of the IQ plane and a line drawn between the origin of the IQ plane and a second signal point on the IQ plane, to which the first bit set is mapped using the second mapping operation;
a distance between the first signal point and the origin is the same as a distance between the second signal point and the origin; and
the first bit set is selected from all combinations possible with the plurality of bits.
2. The transmitting apparatus according to claim 1 , wherein the modulation section is further configured to output a signal indicative of the selected mapping pattern used for the second modulated signal, and the plurality of antennas are further configured to transmit the signal indicative of the selected mapping pattern used for the second modulated signal.
3. The transmitting apparatus according to claim 1 , wherein the first modulated signal and the second modulated signal are orthogonal frequency-division multiplexing (OFDM) signals.
4. A transmission method comprising:
(a) selecting a mapping pattern of a predefined modulation method from among a first mapping method having a first pattern and a second mapping method, which is different from the first mapping method and which comprises one or more second patterns, and outputting a frame configuration signal including information related to the selected mapping pattern;
(b) outputting at least one of a plurality of modulated signals, which are mapped using the first mapping method, as a first modulated signal based solely on the first mapping method, re-mapping the rest of the plurality of modulated signals other than the first modulated signal, which is mapped using the first mapping method, using the selected mapping pattern included in the frame configuration signal to produce a re-mapped signal, and outputting the re-mapped signal as a second modulated signal; and
(c) transmitting the first modulated signal and the second modulated signal from the plurality of antennas, respectively, at the same time period and in the same frequency band, wherein:
the first mapping method and the second mapping method are methods for mapping a signal point corresponding to a bit set, which consists of a plurality of bits, on an IQ plane;
a first phase formed between an I axis of the IQ plane and a line drawn between an origin of the IQ plane and a first signal point on the IQ plane, to which a first bit set is mapped using the first mapping method, is different from a second phase formed between the I axis of the IQ plane and a line drawn between the origin of the IQ plane and a second signal point on the IQ plane, to which the first bit set is mapped using the second mapping method;
a distance between the first signal point and the origin is the same as a distance between the second signal point and the origin; and
the first bit set is selected from all combinations possible with the plurality of bits.
5. The transmission method according to claim 4 , wherein step (b) further comprises outputting a signal indicative of the selected mapping pattern used for the second modulated signal, and step (c) further comprises transmitting the signal indicative of the selected mapping pattern used for the second modulated signal.
6. The transmitting method according to claim 4 , wherein the first modulated signal and the second modulated signal are orthogonal frequency-division multiplexing (OFDM) signals.