Wireless communication apparatus

Abstract

Before data is transmitted from a plurality of antennas, a plurality of known symbol sequences are transmitted from these antennas. Each known symbol sequence contains a plurality of known symbols having different subcarrier arrangements. Known symbols transmitted from different antennas have different subcarrier arrangements.

1 . A wireless communication apparatus comprising:
 a receiving unit configured to receive a plurality of known symbol sequences and a data symbol following the known symbol sequences, each of the known symbol sequences containing a plurality of known symbols, and a plurality of known symbols simultaneously transmitted from different antennas having different subcarrier arrangements;   a channel estimating unit configured to obtain a channel estimation value from the received known symbol sequence; and   a reproducing unit configured to reproduce the data symbol by using the channel estimation value.   
     
     
         2 . An apparatus according to  claim 1 , wherein
 the receiving unit is configured to receive the plurality of known symbol sequences repetitively transmitted a plurality of times, and   the channel estimating unit obtains the channel estimation value by accumulate waveforms in the frequency domain corresponding to the repetitively transmitted known symbol sequences.   
     
     
         3 . An apparatus according to  claim 1 , wherein
 the receiving unit is configured to receive the known symbol sequence, a phase of the known symbol transmitted last of the known symbol sequences being inverted, and   the reproducing unit is configured to obtain a correlation between temporary adjacent known symbols with respect to waveforms in the frequency domain respectively corresponding to the known symbol sequences, and, to estimate, if the correlation value is negative, the number of antennas on the basis of the number of known symbols received so far, and reproduce the data symbol in accordance with the estimated number of antennas.   
     
     
         4 . An apparatus according to  claim 1 , wherein
 the receiving unit is configured to receive the plurality of known symbol sequences repetitively transmitted a plurality of times, and a phase of a known symbol sequence transmitted last is inverted, and   the reproducing unit includes means for (a) accumulating waveforms in the frequency domain respectively corresponding to identical first known symbol sequences which are repetitively transmitted, and holds a first accumulated value, (b) accumulating waveforms in the frequency domain respectively corresponding to second identical known symbol sequences repetitively transmitted following the first known symbol sequences to hold a second accumulated value, (c) correlating the first and second accumulated values, and (d) estimating, if the correlation value is negative, the number of antennas on the basis of the number of known symbols received so far, to reproduce the data symbol in accordance with the estimated number of antennas.   
     
     
         5 . An apparatus according to  claim 1 , wherein
 the receiving unit is configured to receive a second known symbol sequence transmitted by using one antenna selected from the plurality of antennas, the second known symbol sequence containing a plurality of temporary continuous known symbols having the same subcarrier arrangement and opposite phases, and   the reproducing unit is configured to correlate a waveform in the frequency domain corresponding to a known symbol received first of the second known symbol sequence and a waveform in the frequency domain corresponding to a known symbol received next, estimate that the number of antennas used in transmission is one if the correlation value is negative, estimate that the number of antennas used in transmission is not less than two if not, and reproduce the data symbol in accordance with the estimated number of antennas.