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 OFDM signals by using all or a part of a plurality of subcarriers on a frequency band comprising an even number of frequency channels without a center subcarrier positioned in the center of the frequency band, each of the OFDM signals comprising OFDM symbols for broadcast information data transmission and OFDM symbols for communication data transmission, the first communication apparatus comprising:
a transmitting circuit configured for transmitting the OFDM signals to a second communication apparatus by using an even number M of contiguous frequency channels that can be used simultaneously by the second communication apparatus, wherein the even number M is an even number smaller than the even number of frequency channels; and
a processing circuit configured for:
allocating data for constructing each of the OFDM symbols to a subset of the plurality of subcarriers on the even number M of the contiguous frequency channels,
allocating data for constructing each of the OFDM symbols for broadcast information data transmission without allocating data to subcarriers positioned in respective centers of the frequency channels on the even number M of the contiguous frequency channels, and
allocating data for constructing each of the OFDM symbols for communication data transmission without allocating data to a subcarrier positioned in a center of the even number M of the contiguous frequency channels and allocating data to the subcarriers positioned in respective centers of frequency channels on the even number M of the contiguous frequency channels.
2. The first communication apparatus according to claim 1 , wherein the data for constructing each of the OFDM symbols for broadcast information data transmission to be allocated among the even number M of the contiguous frequency channels comprises data representing control information.
3. The first communication apparatus according to claim 2 , wherein the control information comprises information about the OFDM symbols for communication data and 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 indicating subcarrier positions to which data is not allocated.
4. The first communication apparatus according to claim 3 , wherein the information indicating the subcarrier positions to which data is not allocated includes information indicating a frequency bandwidth of the OFDM symbols for communication data.
5. The first communication apparatus according to 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 M of the contiguous frequency channels.
6. The first communication apparatus according to claim 1 , wherein each frequency channel of the even number M of the contiguous frequency channels comprises 64 subcarriers.
7. The first communication apparatus according to claim 1 , wherein a number of frequency channels for transmitting the OFDM signals is determined by the first communication apparatus for each frame.
8. A method for OFDM signals by using all or a part of a plurality of subcarriers on a frequency band comprising an even number of frequency channels without a center subcarrier positioned in the center of the frequency band by a first communication apparatus, each of the OFDM signals comprising OFDM symbols for broadcast information data transmission and OFDM symbols for communication data transmission, the method comprising:
transmitting the OFDM signals from the first communication apparatus to a second communication apparatus by using an even number M of contiguous frequency channels that can be used simultaneously by the second communication apparatus, wherein the even number M is an even number smaller than the even number of frequency channels;
allocating data for constructing each of the OFDM symbols to a subset of the plurality of subcarriers on the even number M of the contiguous frequency channels,
characterized by:
allocating data for constructing each of the OFDM symbols for broadcast information data transmission without allocating data to subcarriers positioned in respective centers of frequency channels on the even number M of the contiguous frequency channels; and
allocating data for constructing each of the OFDM symbols for communication data transmission without allocating data to a subcarrier positioned in a center of the even number M of the contiguous frequency channels, and allocating data to the subcarriers positioned in respective centers of frequency channels on the even number M of the contiguous frequency channels.
9. The method according to claim 8 , wherein the data for constructing each of the OFDM symbols for broadcast information data transmission to be allocated among the even number M of the contiguous frequency channels comprises data representing control information.
10. The method according to claim 9 , wherein the control information comprises information about the OFDM symbols for communication data and 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 indicating subcarrier positions to which data is not allocated.
11. The method according to claim 10 , wherein the information indicating the subcarrier positions to which data is not allocated includes information indicating a frequency bandwidth of the OFDM symbols for communication data.
12. The method according to 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 M of the contiguous frequency channels.
13. The method according to claim 8 , wherein each frequency channel of the even number M of the contiguous frequency channels comprises 64 subcarriers.
14. The method according to claim 8 , wherein a number of frequency channels for transmitting the OFDM signals is determined by the first communication apparatus for each frame.