Communication apparatus and communication method
A communication apparatus includes a receiver and a decoder. The receiver includes a plurality of antenna elements and, in operation, receives from a base station apparatus a modulated signal mapped to one of a plurality of subframes defined in a frame corresponding to a communicable range to which the communication apparatus belongs. The plurality of subframes are defined by time-division, frequency-division, or time-and-frequency division of the frame. A maximum number of modulated signals that can be simultaneously transmitted in a subframe from the base station apparatus varies depending on the communicable range. The decoder, in operation, decodes the received modulated signal.
1. A communication apparatus comprising:
a signal processor which, in operation, generates a modulated signal for each of a plurality of terminals, and maps the modulated signal to one of a plurality of subframes defined in a frame corresponding to a communicable range to which a corresponding one of the plurality of terminals belongs, wherein the plurality of subframes are defined by time-division, frequency-division, or time-and-frequency division of the frame, wherein a maximum number of modulated signals that can be simultaneously transmitted in a subframe from the communication apparatus varies depending on the communicable range; and
a transmitter, which comprises a plurality of antenna elements and which, in operation, performs precoding on the modulated signal and transmits the precoded modulated signal from the plurality of antenna elements, wherein a transmission power for the precoded modulated signal is set by the precoding and wherein a total transmission power for a plurality of transmission beams is equal to or less than a threshold value regardless of a number of transmission beams to be transmitted in a single time period.
2. The communication apparatus according to claim 1 , wherein
the transmitter transmits the precoded modulated signal using directive transmission.
3. The communication apparatus according to claim 1 , wherein
as the communicable range becomes smaller, the maximum number of modulated signals that can be simultaneously transmitted from the communication apparatus in the frame becomes larger.
4. The communication apparatus according to claim 1 , wherein
as the communicable range becomes smaller, the maximum number of modulated signals that can be simultaneously transmitted from the communication apparatus in the subframe becomes larger.
5. The communication apparatus according to claim 1 , wherein
an outer edge of the communicable range is defined by a distance from the communication apparatus.
6. The communication apparatus according to claim 1 , wherein
when a plurality of modulated signals are simultaneously transmitted from the communication apparatus, each of the plurality of modulated signals is mapped to a corresponding one of the plurality of subframes defined in the frame.
7. The communication apparatus according to claim 1 , wherein
a plurality of modulated signals are simultaneously transmitted from the communication apparatus in a same time period and in a same frequency band.
8. The communication apparatus according to claim 1 , wherein
a first number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same time period and in a same frequency band within a first communicable range;
a second number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same period of time and in a same frequency band within a second communicable range that is exclusive of the first communicable range; and
the first number of modulated signals is larger than the second number of modulated signals.
9. The communication apparatus according to claim 8 , wherein
a third number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same period of time and in a same frequency band within a third communicable range that is exclusive of the second communicable range, and
the second number of modulated signals is larger than the third number of modulated signals.
10. A communication method for a communication apparatus, the communication method comprising:
generating a modulated signal for each of a plurality of terminals, and mapping the modulated signal to one of a plurality of subframes defined in a frame corresponding to a communicable range to which a corresponding one of the plurality of terminals belongs, wherein the plurality of subframes are defined by time-division, frequency-division, or time-and-frequency division of the frame, wherein a maximum number of modulated signals that can be simultaneously transmitted in a subframe from the communication apparatus varies depending on the communicable range; and
performing precoding on the modulated signal and transmitting the precoded modulated signal from a plurality of antenna elements, wherein a transmission power for the precoded modulated signal is set by the precoding and wherein a total transmission power for a plurality of transmission beams is equal to or less than a threshold value regardless of a number of transmission beams to be transmitted in a single time period.
11. The communication method according to claim 10 , wherein
the precoded modulated signal is transmitted using directive transmission.
12. The communication method according to claim 10 , wherein
as the communicable range becomes smaller, the maximum number of modulated signals that can be simultaneously transmitted from the communication apparatus in the frame becomes larger.
13. The communication method according to claim 10 , wherein
as the communicable range becomes smaller, the maximum number of modulated signals that can be simultaneously transmitted from the communication apparatus in the subframe becomes larger.
14. The communication method according to claim 10 , wherein
an outer edge of the communicable range is defined by a distance from the communication apparatus.
15. The communication method according to claim 10 , wherein
when a plurality of modulated signals are simultaneously transmitted from the communication apparatus, each of the plurality of modulated signals is mapped to a corresponding one of the plurality of subframes defined in the frame.
16. The communication method according to claim 10 , wherein
a plurality of modulated signals are simultaneously transmitted from the communication apparatus in a same time period and in a same frequency band.
17. The communication method according to claim 10 , wherein
a first number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same time period and in a same frequency band within a first communicable range;
a second number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same period of time and in a same frequency band within a second communicable range that is exclusive of the first communicable range; and
the first number of modulated signals is larger than the second number of modulated signals.
18. The communication method according to claim 17 , wherein
a third number of modulated signals is a maximum number of transmission beams that can be simultaneously transmitted in a same period of time and in a same frequency band within a third communicable range that is exclusive of the second communicable range, and
the second number of modulated signals is larger than the third number of modulated signals.