Signal communications system and method for noisy links
View Patent ↗A system and method for communicating signals over a noisy channel is provided wherein an input signal may be sampled and modulated to make the signal more noise insensitive. In accordance with one embodiment, of the invention, an signal code modulation (SCM) scheme may be used wherein digital and analog signals representing the original signal are generated. In another embodiment, an original modulated signal may be demodulated and then remodulated using a more robust modulation scheme. The system may be used to a variety of applications including wireless internet access.
1. A signal code modulator, comprising:
an input interface for receiving one or more time-discrete samples of a signal; and
a signal code modulation Mapper circuit that converts the aggregate of the one or more time-discrete samples to analog and digital output symbols representing a mix of analog and digital values, wherein said analog output symbols represent amplitude values of a selected subspace of a stretched transformation of said aggregated one or more time-discrete samples and said digital output symbols represent an indication of the subspace chosen in the stretched transformation.
2. The signal code modulator of claim 1 , wherein said signal code modulation Mapper circuit further comprises a stretching transformation circuit for mapping the one or more of said signal samples onto a transformed signal space represented by an aggregate of one or more transformed signal samples and a subspace slicer that selects one or more subspaces from said transformed signal space and outputs said mix of analog and digital symbols based on the selected subspace and the one or more transformed signal samples.
3. The signal code modulator of claim 1 further comprising means for forward error correcting said digital output symbols before transmission.
4. The signal code modulator of claim 2 , wherein said stretching transformation circuit further comprises a linear expansion circuit for linearly expanding the sample signals in one or more dimensions.
5. The signal code modulator of claim 2 , wherein said stretching transformation circuit further comprises a non-linear expansion circuit that transforms a quarter-circle sub space onto a full circle transformed signal space.
6. The signal code modulator of claim 2 , wherein said stretching transformation circuit further comprises conformal mapping.
7. The signal code modulator of claim 1 further comprising a multiplexer for multiplexing the analog and digital symbols for transmission over a common communications channel.
8. The signal code modulator of claim 7 , further comprising a signal code modulation Mapper comprising means for pairing said multiplexed symbols and a quadrature amplitude modulator for quadrature amplitude modulating each pair of signals to generate QAM signals.
9. The signal code modulator of claim 8 , wherein each of the QAM signals comprise analog symbols or digital symbols as originated from the output of said signal code modulation Mapper.
10. The signal code modulator of claim 9 , wherein the QAM signals comprise a mix of both analog and digital symbols as originated from the output of said signal code modulation Mapper.