Circular constellations with coherent gain/differential phase and pilots
View Patent ↗The modulation method and system of the presented herein involves mapping data onto a constellations comprising a set of concentric circles in a two-dimensional plane, one dimension for the amplitude and one for the phase. The phase dimension is coded differentially, while the amplitude dimension is coded coherently. The circles in each constellation may contain equal number of points, and in other embodiments more points may be used on the outer circles. The data may be coded with dual Trellis codes, one code for the phase data and another code for the amplitude data.
1. A method for robust signaling over a transmission medium, said method comprising:
obtaining data for transmission over said transmission medium;
obtaining a transfer function of said transmission medium;
selecting a data transmission rate using said transfer function;
selecting a set of tones capable of supporting said transmission rate at a predefined error rate; and
encoding said data at said data transmission rate, using a plurality of encoders, across said set of tones;
mapping said data onto a set of concentric circular rings as a plurality of constellation points, wherein each of said rings includes a portion of said plurality of constellation points, and wherein each of said rings has an amplitude relative to the innermost ring defining a ring radius for each of said rings, and wherein each of said constellation points on each of said rings has the same ring radius as other constellation points on the same ring.
2. The method of claim 1 , wherein said encoding said data comprises:
determining a pair of amplitudes from said amplitude of each of said rings for all of said set of tones, wherein said pair of amplitudes is transmitted over two time symbols;
determining a cumulative phase angle for each of said set of tones from a phase of each of said rings.
3. The method of claim 2 , wherein said plurality of encoders comprises an amplitude encoder and a phase encoder.
4. The method of claim 3 , wherein said amplitude encoder is a Pulse Amplitude Modulation encoder.
5. The method of claim 3 , wherein said phase encoder uses trellis coded modulation.
6. The method of claim 3 , wherein said amplitude and said phase are coded independently.
7. The method of claim 1 , wherein said transmission medium is subdivided into channels.
8. The method of claim 7 , wherein said transfer function is signal-to-noise ratio of each of said channels.
9. The method of claim 1 , further comprising:
decoding said amplitude coherently; and
decoding said phase differentially.
10. The method of claim 9 , wherein said decoding said phase comprises:
applying symbol-interleaving to break up consecutive phase-delta errors; and
applying erasures decoding to eliminate unreliable data.
11. A device for robust signaling over a transmission medium, said device comprising:
a channel gain estimator for determining a transfer function of a transmission medium;
a rate selector for selecting a data transmission rate using said transfer function;
a constellation mapper for mapping data to be transmitted over a set of tones capable of supporting said transmission rate at a predefined error rate, wherein the constellation mapper is configured to map said data onto a set of concentric circular rings as a plurality of constellation points, wherein each of said rings includes a portion of said plurality of constellation points, and wherein each of said rings has an amplitude relative to the innermost ring defining a ring radius for each of said rings, and wherein each of said constellation points on each of said rings has the same ring radius as other constellation points on the same ring; and
a plurality of encoders for encoding said data at said data transmission rate across said set of tones.
12. The device of claim 11 , wherein said encoding said data comprises:
determining a pair of amplitudes from said amplitude of each of said rings for all of said set of tones, wherein said pair of amplitudes is transmitted over two time symbols;
determining a cumulative phase angle for each of said set of tones from a phase of each of said rings.
13. The device of claim 12 , wherein said plurality of encoders comprises an amplitude encoder and a phase encoder.
14. The device of claim 13 , wherein said amplitude encoder is a Pulse Amplitude Modulation encoder.
15. The device of claim 13 , wherein said phase encoder uses trellis coded modulation.
16. The device of claim 13 , wherein said amplitude and said phase are coded independently.
17. The device of claim 11 , wherein said transmission medium is subdivided into channels.
18. The device of claim 17 , wherein said transfer function is signal-to-noise ratio of each of said channels.
19. The device of claim 11 , further comprising:
a coherent amplitude decoder with or without phase decisions; and
a differential phase decoder employing symbol-interleaving to break up consecutive phase-delta errors and erasures decoding to eliminate unreliable data.