Communication system using orthogonal frequency division multiplexed signal
View Patent ↗An orthogonal frequency division multiplexed signal generator comprises a data sequence conversion means, a power changing means, an inverse discrete Fourier transform part, and an orthogonal modulation means, and modulates a first data and a second data using modulation systems independent of each other, into an orthogonal frequency division multiplexed signal. The data sequence conversion means arranges the first data to be transmitted, in a predetermined order correspondingly to two or more sub-carriers orthogonal to each other on a frequency axis. The power changing means changes powers of the sub-carriers in accordance with the second data to be transmitted which is independent of the first data. The inverse discrete Fourier transform means generates a time-base waveform by synthesizing the individual sub-carriers. The orthogonal modulation means performs orthogonal modulation on a real axis signal and an imaginary axis signal which are orthogonal to each other to synthesize them.
1. A method of generating an orthogonal frequency division multiplexed signal for generating a signal that is orthogonal-frequency-division-multiplexed into two or more sub-carriers, comprising the steps of:
converting serially-input transmission data to parallel data sequences on each of the two or more sub-carriers;
delaying said transmission data for a predetermined time to produce power-changing data;
changing powers of said sub-carriers in accordance with said power-changing data;
performing an inverse discrete Fourier transform on the two or more sub-carriers; and
performing orthogonal modulation on orthogonal real axis and imaginary axis signals generated by said inverse discrete Fourier transform.
2. A communication apparatus for communicating using an orthogonal frequency division multiplexed signal, comprising:
a transmission means for performing orthogonal frequency division multiplex modulation on a carrier in accordance with data given by an inputted signal, to transmit a multiplexed signal; and
a receiving means for performing orthogonal frequency division multiplex demodulation on the received signal to detect the modulation data and for outputting the signal given by the modulation data;
wherein said transmission means comprises:
a data sequence conversion means for arranging first data to be transmitted, in a predetermined order corresponding to two or more sub-carriers orthogonal to each other on a frequency axis;
a delay means for delaying said first data for a predetermined time to generate second data;
a power changing means for changing a power spectrum of said sub-carriers in accordance with said second data;
an inverse discrete Fourier transform means for generating a time-base waveform by synthesizing the two or more sub-carriers changed by said power changing means; and
an orthogonal modulation means for performing orthogonal modulation on a real axis signal and an imaginary axis signal which are orthogonal to each other and generated by said inverse discrete Fourier transform means, to synthesize the real axis signal and the imaginary axis signal; and
said receiving means comprises:
a quadrature detection means for performing quadrature detection on the received signal to obtain a first detection axis signal and a second detection axis signal which are quadrate to each other;
a discrete Fourier transform means for sampling respective time-base waveforms of said first detection axis signal and said second detection axis signal at a predetermined sampling frequency, and for performing discrete Fourier transform on these sampled data to obtain two or more metrics distributed in a frequency domain;
a first data extracting means for extracting said first data from respective phase changes of sub-carriers for each symbol, obtained by said discrete Fourier transform means; and
a second data extracting means for extracting said second data from an envelope of a distribution of the metrics obtained by said discrete Fourier transform means.
3. The communication apparatus according to claim 2 , wherein:
when a minimum unit for transmitting said second data is s bits, said power changing means changes a power spectrum of said sub-carriers according to 2 to the s-th power levels.
4. The communication apparatus according to claim 3 , wherein:
when a minimum unit for transmitting said first data assigned to said sub-carriers is p bits, said power conversion means selects said s bits so that s is equal to or more than p, to transmit said second data.