Electronic apparatus configured for combination with a dual-carrier-modulation (DCM) coded orthogonal-frequency-division-multiplex (COFDM) signal conveyed by a plurality of quadrature-amplitude-modulated (QAM) electromagnetic carrier waves, said combination useful in an enabling manner within in a communication system for conveying coded digital data, said DCM-COFDM signal further characterized by:
- (a) a first half of said plurality of electromagnetic carrier waves being amplitude modulated by respective ones of a first set of successive square QAM symbols of a specific size larger than 16QAM, each superposition-coded-modulation (SCM) mapped in accordance with a first pattern of lattice-point labeling, thereby to convey a respective set of soft bits of coded digital data via each QAM symbol in said first set of successive square QAM symbols, each QAM symbol SCM mapped in accordance with said first pattern of SCM mapping square QAM symbol constellations comprising a respective −I,+Q quadrant and a respective +I,+Q quadrant and a respective +I,−Q quadrant and a respective −I,−Q quadrant, each of said quadrants in said first pattern of SCM mapping digital lattice-point labels to QAM symbol constellations being composed of an innermost sub-quadrant thereof and an outermost sub-quadrant thereof and two flanking sub-quadrants thereof;
- (b) a second half of said plurality of electromagnetic carrier waves being amplitude modulated by respective ones of a second set of successive square QAM symbols of said specific size larger than 16QAM, each SCM mapped in accordance with a second pattern of lattice-point labeling, thereby to convey a respective set of soft bits of said coded digital data via each QAM symbol in said second set of successive square QAM symbols, each QAM symbol SCM mapped in accordance with said second pattern of SCM mapping square QAM symbol constellations comprising a respective −I,+Q quadrant and a respective +I,+Q quadrant and a respective +I,−Q quadrant and a respective −I,−Q quadrant, each of said quadrants in said second pattern of SCM mapping digital lattice-point labels to QAM symbol constellations being composed of an innermost sub-quadrant thereof and an outermost sub-quadrant thereof and two flanking sub-quadrants thereof
- (c) the lattice points in the outermost sub-quadrants of said four quadrants of said second pattern of SCM mapping having respective digital map labels corresponding to digital map labels of lattice points in the innermost sub-quadrants of said four quadrants of said first pattern of SCM mapping, the lattice points in the innermost sub-quadrants of said four quadrants of said second pattern of SCM mapping having respective digital map labels corresponding to digital map labels of lattice points in the outermost sub-quadrants of said four quadrants of said first pattern of SCM mapping;
- (d) each lattice-point label associated with higher energy in said first pattern of lattice-point labeling being associated with lower energy in said second pattern of lattice-point labeling, each lattice-point label associated with lower energy in said first pattern of lattice-point labeling being associated with higher energy in said second pattern of lattice-point labeling;
- (e) bits more likely to experience error in the lattice-point labeling of the first set of successive QAM symbols per said first mapping pattern correspond to bits less likely to experience error in the lattice-point labeling of the second set of successive square QAM symbols per said second mapping pattern;
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- (f) bits more likely to experience error in the lattice-point labeling of the second set of successive square QAM symbols per said second mapping pattern correspond to bits less likely to experience error in the lattice-point labeling of the first set of successive square QAM symbols per said first mapping pattern.