METHOD TO CREATE HIERARCHICAL MODULATION IN OFDM

摘要

The present invention involves a method for transmitting data using an orthogonal frequency division multiplex (OFDM) transmission system, such as over a terrestrial network used in satellite digital audio radio. A OF'DM signal is generated based on first input data. A variation is introduced in the OFDM signal based on second input data to generate a modified OFDM signal which is transmitted. The modified OFDM signal is decoded by performing a demodulation of the modified OFDM signal then a first and second detection to obtain the first input data and the second input data. The introduction of a variance may include introducing an additional phase offset across adjacent OFDM sub-carriers, across adjacent OFDM symbols, an additional phase offset in the OFDM signal., an additional amplitude offset in the OFDM signal, an additional amplitude augmentation in the OFDM signal, and/or a second variation in the first OFDM signal based on third input data.