Communication method and radio transmitter
Radio transmission is performed even to a communication party whose bandwidth that can be used for transmission and reception is limited without having an influence of an offset of a DC component. A radio transmitter applied to an OFDMA communication system in which a plurality of different terminals performs communication using OFDM signals at the same time that includes a mapping part that allocates transmission power to each subcarrier, and also selects a subcarrier to which minimum power of the transmission power to be allocated is allocated and modulates transmission data in units of communication slots to output the modulated data; and a transmission part for transmitting radio signals including the modulated data using each of the subcarriers.
1. A first communication apparatus configured to transmit OFDM signals by using at least some of a plurality of frequency sub-channels on a frequency band without a center subcarrier positioned in a center frequency of the frequency band, each of the OFDM signals comprising OFDM symbols for a first period and OFDM symbols for a second period, the first communication apparatus comprising:
a transmitting circuit configured for transmitting the OFDM signals to a second communication apparatus by using a plurality of subcarriers allocated among an even number of contiguous frequency sub-channels that can be used simultaneously by the second communication apparatus, wherein the even number comprises at least an even number smaller than a number of the plurality of frequency sub-channels on the frequency band;
a processing circuit configured for:
allocating data for constructing each of the OFDM symbols for the first period to a first subset of subcarriers of the plurality of subcarriers without allocating data to each of respective subcarriers positioned in respective centers of frequency sub-channels among the even number of the contiguous frequency sub-channels, and
allocating data for constructing each of the OFDM symbols for the second period to a second subset of subcarriers of the plurality of subcarriers without allocating data to a subcarrier positioned in a center of a frequency band of the even number of the contiguous frequency sub-channels for the second period, the unused subcarrier being in a center between contiguous frequency sub-channels, the second subset of subcarriers comprising the respective subcarriers positioned in respective centers of frequency sub-channels among the even number of the contiguous frequency sub-channels.
2. The first communication apparatus of claim 1 , wherein the data for transmission in the first period to be allocated to the first subset of subcarriers of the plurality of subcarriers that are allocated among the even number of the contiguous frequency sub-channels comprises data representing control information.
3. The first communication apparatus of claim 2 , wherein the control information comprises information about the second period and indirectly indicating positions of subcarriers to which data is not allocated, wherein the positions of the plurality of subcarriers are known mutually between the first communication apparatus and the second communication apparatus based on the information indirectly indicating the subcarrier positions to which data is not allocated.
4. The first communication apparatus of claim 3 , wherein the information indirectly indicating the subcarrier positions to which data is not allocated includes information indicating a frequency bandwidth of the OFDM symbols for the second period.
5. The first communication apparatus of claim 1 , wherein the transmitting circuit is further configured for:
converting a digital signal represented by the plurality of subcarriers to an analog signal; and
converting the analog signal to a radio frequency signal based on a center frequency of the frequency band of the even number of the contiguous frequency sub-channels.
6. The first communication apparatus of claim 1 , wherein each of the frequency sub-channels has a bandwidth of 20 MHZ and comprises 64 subcarriers.
7. The first communication apparatus of claim 1 , wherein the processing circuit further configured for selecting a frequency bandwidth indicate the even number of contiguous frequency sub-channels to be used for transmission for each of the OFDM signals.
8. A method for transmitting OFDM signals by a first communication apparatus using at least some of a plurality of frequency sub-channels on a frequency band without a center subcarrier positioned in a center frequency of the frequency band, each of the OFDM signals comprising OFDM symbols for a first period and OFDM symbols for a second period, the method comprising:
transmitting the OFDM signals from the first communication apparatus to a second communication apparatus by using a plurality of subcarriers allocated among an even number of contiguous frequency sub-channels that can be used simultaneously by the second communication apparatus, wherein the even number comprises at least an even number smaller than a number of the plurality of frequency sub-channels on the frequency band;
allocating data for constructing each of the OFDM symbols for the first period to a first subset of subcarriers of the plurality of subcarriers without allocating data to each of respective subcarriers positioned in respective centers of frequency sub-channels among the even number of the contiguous frequency sub-channels;
allocating data for constructing each of the OFDM symbols for the second period to a second subset of subcarriers of the plurality of subcarriers without allocating data to a subcarrier positioned in a center of a frequency band of the even number of the contiguous frequency sub-channels for the second period, the unused subcarrier being in a center between contiguous frequency sub-channels, the second subset of subcarriers comprising the respective subcarriers positioned in respective centers of frequency sub-channels among the even number of the contiguous frequency sub-channels.
9. The method of claim 8 , wherein the data for transmission in the first period to be allocated to the first subset of subcarriers of the plurality of subcarriers that are allocated among the even number of the contiguous frequency sub-channels comprises data representing control information.
10. The method of claim 9 , wherein the control information comprises information about the second period and indirectly indicating positions of subcarriers to which data is not allocated, wherein the positions of the plurality of subcarriers are known mutually between the first communication apparatus and the second communication apparatus based on the information indirectly indicating the subcarrier positions to which data is not allocated.
11. The method of claim 10 , wherein the information indirectly indicating the subcarrier positions to which data is not allocated includes information indicating a frequency bandwidth of the OFDM symbols for the second period.
12. The method of claim 8 , further comprising converting a digital signal represented by the plurality of subcarriers to an analog signal and converting the analog signal to a radio frequency signal based on a center frequency of the frequency band of the even number of the contiguous frequency sub-channels.
13. The method of claim 8 , wherein each of the frequency sub-channels has a bandwidth of 20 MHZ and comprises 64 subcarriers.
14. The method of claim 8 , wherein the processing circuit further configured for selecting a frequency bandwidth indicate the even number of contiguous frequency sub-channels to be used for transmission for each of the OFDM signals.