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

Abstract

Serially concatenated convolutional coding (SCCC) transmitting ancillary data within DTV signals incorporates the ⅔ trellis coding used for all DTV signals as its inner convolutional coding. The outer convolutional coding of the SCCC is subjected to _“anti-Gray”_ coding, either before or after its interleaving, but before its inner convolutional coding. In a receiver for ancillary data as so transmitted, simple logic circuitry recodes portions of the trellis decoded DTV signal containing soft decisions as to the symbol-interleaved convolutionally coded ancillary data to provide a Gray-code mapping of symbols to modulation levels. This recoding is done either before or after symbol de-interleaving, but before decoding the outer convolutional coding to recover ancillary data. Soft decisions concerning extrinsic information to be fed back to the ⅔ trellis decoder to close a turbo decoding loop are derived from soft decisions as to the ancillary data, and this derivation includes recoding for a binary-code mapping of symbols to modulation levels.

Description

[0001]This application is filed under 35 U.S.C. 111(a) claiming, pursuant to 35 U.S.C. 119(e)(1), benefit of the filing date of provisional U.S. patent application Ser. No. 61 / 133,294 filed pursuant to 35 U.S.C. 111(b) on Jun. 27, 2008.[0002]The invention relates to over-the-air broadcasting of digital television (DTV) signals and more particularly to receivers for such broadcast DTV signals.BACKGROUND OF THE INVENTION[0003]The Advanced Television Systems Committee (ATSC) published a Digital Television Standard in 1995 as Document A / 53, hereinafter referred to simply as “A / 53” for sake of brevity Digital television. A / 53 specifies the eight-level-modulation vestigial-sideband amplitude-modulation signals known as “8VSB” signals that are used for over-the-air DTV broadcasting in the United States of America. In late May 2009 ATSC completed the writing of a “Candidate Standard: ATSC Mobile DTV Standard”, referred to hereinafter simply as “A / 153” for sake of brevity, which candidate st...

AI Technical Summary

Benefits of technology

[0016]Each of the recoding procedures can be performed using read-only memory, but preferably is performed using simple logic circuitry. In some receiver designs that embody the

Problems solved by technology

This makes a double-bit error likely when noise causes an adjacent-bin error during data slicing in this region of the symbol map.

However, when further convolutional coding is introduced before the ⅔ trellis coding at the transmitter, the double-bit errors are more disruptive than single-bit errors when decoding that further convolutional coding in the receiver.

However, symbol mapping using Gray code over all eight modulation levels is incompatible with the ⅔ trellis coding of ordinary 8VSB coding.

So, initially, the inventor was unable to discern how to utilize effectively the general idea of avoiding an adjacent-bin error during data slicing generating double-bit errors in a special type of turbo coding designed for digital television broadcasting.

When a spike of noise energy or a drop-out in received signal obliterates a few 8VSB symbols or causes distant-bin errors in the coded symbols, the information for resolving adjacent-bin errors in subsequent symbols is corrupted and is apt to generate recurring error for some time.

After the inventor's insight into how to avoid an adjacent-bin error during data slicing generating double-bit errors in symbols each composed of a Z-sub-2 bit and a Z-sub-1 bit, there remained further problems of designing DTV transmitter and DTV receiver configurations to exploit the insight.

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