| 摘要 |
Procedures performed prior to convolutional interleaving of 8VSB digital television signals restrict the alphabet of symbols in novel methods of generating trellis-coded digital television signals that include more robust symbol coding using a restricted alphabet of symbols selected from a full 8VSB symbol alphabet consisting of −7, −5, −3, −1, +1, +3, +5 and +7 normalized modulation levels superposed on a background modulation level. Certain of these novel procedures generate pseudo-2VSB or P-2VSB robust symbol coding with a restricted alphabet of symbols consisting of −7, −5, +5 and +7 normalized modulation levels superposed on a background modulation level. Others of these novel procedures generate prescribed-coset-pattern-modulation or PCPM robust symbol coding intermixing two restricted alphabets of symbols according to a prescribed pattern. One of the two restricted alphabets of symbols used in PCPM consists of −3, −1, +5 and +7 normalized modulation levels superposed on a background modulation level. The other of the two restricted alphabets of symbols used in PCPM consists of −7, −5, +1 and +3 normalized modulation levels superposed on a background modulation level.
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