Communication apparatus and communication system

Abstract

A communication apparatus includes a reference signal generating section, a transmitting section, a propagation estimating section, a first data acquiring section, and a decoding section. The reference signal generating section generates a first reference signal to enable a communicating party to estimate a propagation environment. The transmitting section transmits the first reference signal. The propagation estimating section estimates a first propagation estimation value of the propagation environment using a second reference signal transmitted from the communicating party. The first data acquiring section generates first data using the first propagation estimation value. The decoding section decodes a transmission signal encoded using a second propagation estimation value that is estimated by the communicating party using the first reference signal, to obtain second data using the first data.

The invention claimed is: 
     
       1. A communication apparatus, comprising:
 a reference signal generating section that generates a first reference signal to enable a communicating party to estimate a propagation environment;   a transmitting section that transmits the first reference signal;   a storing section that stores a known signal known between the apparatus and the communicating party   a propagation estimating section that obtains correlation between the known signal and a second reference signal transmitted from the communicating party, and generates a delay profile as an estimation value of propagation environment;   a first data acquiring section that reads out first data associated with the delay profile generated in the propagation estimating section, from a reference table that associates the delay profile with the first data; and   a decoding section that decodes a transmission signal encoded and transmitted using an estimation value of the propagation environment estimated by the communicating party using the first reference signal, to obtain second data using the first data read out by the first data acquiring section.   
     
     
       2. The communication apparatus according to  claim 1 , wherein the first data acquiring section calculates convolution of correlation between the known signal and the second reference signal, and a quantization vector stored in the reference table, and selects and reads out a vector code as the first data by performing metric calculation using the delay profile and the quantization vector subjected to the convolution. 
     
     
       3. The communication apparatus according to  claim 1 , wherein the first data acquiring section performs orthogonal conversion on the delay profile generated in the propagation estimating section to condense signal components, and reads out the first data using signal components. 
     
     
       4. A communication method, comprising:
 generating, in a first communication apparatus, a first reference signal to enable a second communication apparatus to estimate a propagation environment;   transmitting the first reference signal from the first communication apparatus to the second communication apparatus;   storing, in the first communication apparatus, a known signal known between the first communication apparatus and the second communication apparatus;   obtaining, in the first communication apparatus, correlation between the known signal and a second reference signal transmitted from the second communication apparatus, and generating, in the first communication apparatus, a delay profile as an estimation value of the propagation environment;   reading out, in the first communication apparatus, first data associated with the generated delay profile, from a reference table that associates the delay profile with the first data; and   decoding, in the first communication apparatus, a transmission signal encoded and transmitted using an estimation value of the propagation environment estimated by the second communication apparatus using the first reference signal, to second data using the first data read out.   
     
     
       5. A transmission method performed by a communication apparatus, the transmission method comprising:
 generating two transmission signals by dividing a data signal;   selecting a phase for each of the two transmission signals to be transmitted based on a signal from another communication apparatus;   performing a precoding process on the two transmission signals, after the phase for each of the two transmission signals is selected, based on the signal from the other communication apparatus, wherein the precoding process includes changing at least a phase of each of the two transmission signals in response to the selected phase, and wherein the phase of data of the two transmission signals is different from phases of reference signals of the two transmission signals; and   transmitting the two transmission signals subjected to the precoding process via different antennas, respectively, with a same frequency band at a same timing.   
     
     
       6. A communication apparatus comprising:
 a transmission modulator that
 generates two transmission signals by dividing a data signal, 
 selects a phase for each of the two transmission signals to be transmitted based on a signal from another communication apparatus, and 
 performs a precoding process on the two transmission signals, after the phase for each of the two transmission signals is selected, based on the signal from the other communication apparatus, wherein the precoding process includes changing at least a phase of each of the two transmission signals in response to the selected phase, and wherein the phase of data of the two transmission signals is different from phases of reference signals of the two transmission signals; and 
 a transmitter that transmits the two transmission signals subjected to the precoding process via different antennas, respectively, with a same frequency band at a same timing. 
   
     
     
       7. A reception method performed by a communication apparatus, the reception method comprising:
 receiving two signals, transmitted with a same frequency band at a same timing, the two signals having been subjected to a precoding process,   wherein a phase is selected in each of the two signals that were transmitted based on a signal from the communication apparatus,   wherein the precoding process is performed, after the phase for each of the two signals is selected, based on the signal from the communication apparatus,   wherein the precoding process includes changing at least a phase of each of the two signals in response to the selected phase, and   wherein the phase of data of the two signals is different from phases of reference signals of the two signals; and   demodulating a data signal included in the two signals.   
     
     
       8. A communication apparatus comprising:
 a receiver that receives two signals, transmitted with a same frequency band at a same timing, the two signals having been subjected to a precoding process; and   a transmitter, which in operation, transmits a signal used for a determination of a phase of each of the two signals,   wherein at least a phase of each of the two signals is a modified phase that is based on the determined phase, and   wherein the modified phase of data of the two signals is different from phases of reference signals of the two signals; and   a demodulator that demodulates the two signals generated by the determined phase.