WE CLAIM:
1. A transmission apparatus that performs transmission
using an orthogonal frequency division multiplexing scheme
in one or a plurality of frequency bands, the transmission
apparatus comprising:
a symbol multiplexing unit to multiply a column vector containing a first number of modulated symbols generated by primary modulation in a frequency domain, by a precoding matrix having as many rows and columns as the first number to generate a multiplexed symbol group containing the first number of multiplexed symbols each containing a second number of the modulated symbols that are multiplexed, where the first number is two or more, and the second number is equal to or more than two and equal to or less than the first number; and
a subcarrier allocation unit to allocate the multiplexed symbols contained in the multiplexed symbol group to different subcarriers.
2. The transmission apparatus according to claim 1, wherein the precoding matrix is a matrix that causes a sum of power values of the first number of the modulated symbols before multiplication by the precoding matrix to match a sum of power values of the first number of the multiplexed symbols calculated by multiplication by the precoding matrix.
3. The transmission apparatus according to claim 2, wherein the precoding matrix is a matrix that causes each of the power values of the first number of the modulated symbols before multiplication by the precoding matrix to match a corresponding one of power values of respective modulated symbol elements obtained by conversion, into

power values, of the first number of the multiplexed symbols calculated by multiplication by the precoding matrix.
4. A transmission apparatus that performs transmission
using an orthogonal frequency division multiplexing scheme
in one or a plurality of frequency bands, the transmission
apparatus comprising:
a symbol multiplexing unit to generate a first number of first column vectors each containing a different combination of a second number of elements among the first number of modulated symbols generated by primary modulation in a frequency domain, where the first number is two or more, and the second number is equal to or more than two and equal to or less than the first number; to multiply the first number of the first column vectors by a precoding matrix having as many rows and columns as the second number to generate the first number of second column vectors each containing the second number of elements; and to select one element from each of the first number of the second column vectors to generate a multiplexed symbol group containing the first number of multiplexed symbols; and
a subcarrier allocation unit to allocate the multiplexed symbols contained in the multiplexed symbol group to different subcarriers, wherein
the symbol multiplexing unit selects an element from the first number of the second column vectors such that each of the first number of the modulated symbols is contained, as one element, in the first number of the multiplexed symbols.
5. The transmission apparatus according to claim 4,
wherein the symbol multiplexing unit selects an element

from the first number of the second column vectors to cause a sum of power values of the first number of the modulated symbols before multiplication by the precoding matrix to match a sum of power values of the first number of the multiplexed symbols.
6. The transmission apparatus according to claim 5, wherein the symbol multiplexing unit selects an element from the first number of the second column vectors to cause each of the power values of the first number of the modulated symbols before multiplication by the precoding matrix to match a corresponding one of power values of respective modulated symbol elements obtained by conversion, into power values, of the first number of the multiplexed symbols.
7. The transmission apparatus according to any one of claims 1 to 6, wherein, in a case in which the one or a plurality of frequency bands is one frequency band and one symbol in the orthogonal frequency division multiplexing scheme includes a third number of the subcarriers, where the third number is greater than the first number, the subcarrier allocation unit allocates the first number of the multiplexed symbols contained in the multiplexed symbol group to subcarriers separated from each other by a fourth number of the subcarriers, where the fourth number is calculated by division of the third number by the first number.
8. The transmission apparatus according to any one of claims 1 to 6, wherein, in a case in which the one or a plurality of frequency bands is a plurality of frequency bands, the subcarrier allocation unit allocates the first

number of the multiplexed symbols contained in the multiplexed symbol group to subcarriers of symbols in the orthogonal frequency division multiplexing scheme in different frequency bands.
9. The transmission apparatus according to any one of claims 1 to 6, wherein the subcarrier allocation unit allocates the first number of the multiplexed symbols contained in a multiplexed symbol group having a higher required transmission quality level to subcarriers relatively widely separated from each other in a frequency direction, and allocates the first number of the multiplexed symbols contained in a multiplexed symbol group having a lower required transmission quality level than a required transmission quality level of the multiplexed symbol group having the higher required transmission quality level, to subcarriers less separated from each other in the frequency direction than the subcarriers to which the first number of the multiplexed symbols contained in the multiplexed symbol group having the higher required transmission quality level are allocated.
10. The transmission apparatus according to any one of claims 1 to 6, wherein the subcarrier allocation unit changes the subcarriers to which the multiplexed symbols are allocated each time a symbol in the orthogonal frequency division multiplexing scheme in each of the one or plurality of frequency bands is output.
11. The transmission apparatus according to any one of claims 1 to 10, further comprising:
a symbol spreading unit to perform a spreading operation on the modulated symbol generated by primary

modulation to generate post-spread symbols that are generated by spreading of the modulated symbol, wherein
the symbol multiplexing unit generates the multiplexed symbol group containing the first number of the multiplexed symbols using the post-spread symbols.
12. A transmission method of a transmission apparatus that
performs transmission using an orthogonal frequency
division multiplexing scheme in one or a plurality of
frequency bands, the transmission method comprising:
a symbol multiplexing step, performed by a symbol multiplexing unit, of multiplying a column vector containing a first number of modulated symbols generated by primary modulation in a frequency domain, by a precoding matrix having as many rows and columns as the first number to generate a multiplexed symbol group containing the first number of multiplexed symbols each containing a second number of the modulated symbols that are multiplexed, where the first number is two or more, and the second number is equal to or more than two and equal to or less than the first number; and
a subcarrier allocation step, performed by a subcarrier allocation unit, of allocating the multiplexed symbols contained in the multiplexed symbol group to different subcarriers.
13. A transmission method of a transmission apparatus that
performs transmission using an orthogonal frequency
division multiplexing scheme in one or a plurality of
frequency bands, the transmission method comprising:
a first column vector generation step, performed by a symbol multiplexing unit, of generating a first number of first column vectors each containing a different

combination of a second number of elements among the first number of modulated symbols generated by primary modulation in a frequency domain, where the first number is two or more, and the second number is equal to or more than two and equal to or less than the first number;
a second column vector generation step, performed by the symbol multiplexing unit, of multiplying the first number of the first column vectors by a precoding matrix having as many rows and columns as the second number to generate the first number of second column vectors each containing the second number of elements;
a symbol multiplexing step, performed by the symbol multiplexing unit, of selecting the first number of elements from each of the first number of the second column vectors to generate a multiplexed symbol group containing the first number of multiplexed symbols; and
a subcarrier allocation step, performed by a subcarrier allocation unit, of allocating the multiplexed symbols contained in the multiplexed symbol group to different subcarriers, wherein
in the symbol multiplexing step, the symbol multiplexing unit selects an element from the first number of the second column vectors such that each of the first number of the modulated symbols is contained, as one element, in the first number of the multiplexed symbols.