System for digital television broadcasting using modified 2/3 trellis coding

A receiver for vestigial-sideband amplitude-modulation (VSB AM) signal, successive symbols of the modulating signal for said VSB AM signal defining a digital signal in accordance with an eight-level symbol alphabet superposed on a pedestal, said digital signal composed of successive frames each composed of two respective fields of digital-signal symbols, each said field composed of a respective initial segment of 832 digital-signal symbols succeeded by respective 312 consecutive further segments of 832 digital-signal symbols apiece, the four initial digital-signal symbols of each of said segments of 832 digital-signal symbols being a prescribed data segment synchronizing signal sequence, the final 828 digital-signal symbols of said 312 further segments of each said field of digital-signal symbols having prescribed ⅔ trellis coding, three-bit symbols of said ⅔ trellis coding being mapped to said eight-level symbol alphabet in such manner as to generate binary-coded modulation superposed on said pedestal, at least some said respective 312 further segments of said fields of digital-signal symbols including within selected portions thereof digital-signal symbols generated by said prescribed ⅔ trellis coding responding to mobile/handheld (M/H)-service data that has been randomized and encoded with an outer coding, two-bit symbols of which outer coding are subjected to symbol interleaving and anti-Gray-coding before being ⅔ trellis coded, said receiver comprising:

• apparatus for receiving a selected vestigial-sideband amplitude-modulation signal and converting it to a baseband digital signal including successive reproduced eight-level symbols of 12-phase ⅔ trellis-coded baseband digital signal;
• an inner soft-input/soft-output (SISO) decoder connected for trellis decoding said successive reproduced eight-level symbols of 12-phase ⅔ trellis-coded baseband digital signal to generate an inner decoder response composed of soft decisions concerning two-bit symbols previously encoded within said eight-level symbols, each soft decision composed of a respective hard decision as to the value of each of said two-bit symbols and an accompanying indication of the probability of that said respective two-bit symbol being correct;
• a symbol processor for generating a succession of processed soft decisions by symbol de-interleaving selected successive ones of said soft decisions generated by said inner decoder and by re-coding said selected successive ones of said soft decisions generated by said inner decoder so as to appear as though having been extracted from a Gray-coded modulating signal, said selected successive ones of said soft decisions generated by said inner decoder being those that concern anti-Gray-coded two-bit symbols of symbol-interleaved M/H-service data encoded with said outer coding, each processed soft decision being supplied by said symbol processor as a respective symbol composed of two soft bits;
• and
• an outer soft-input/soft-output (SISO) decoder for said M/H-service data encoded with an outer coding connected for receiving said processed soft decisions supplied from said symbol processor and further decoding said processed soft decisions as so received to generate soft decisions concerning two-soft-bit symbols of said M/H-service data.