Trellis code modulation decoder structure for advanced digital television receiver

• US 6,201,563 B1
• Filed: 06/08/1998
• Issued: 03/13/2001
• Est. Priority Date: 06/08/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Rhee, Dojun
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): DESIR, JEAN WICEL
• Application Number:
  US09/093,362
• Time in Patent Office: 1,009 Days
• Field of Search: H04/N.521, H04/N.764, 348/21, 348/17, 348/607, 348/608, 348/609, 348/725, 348/614, 348/470, 348/426, 348/723, 375/341, 375/262, 375/263, 375/265, 375/295, 375/296, 375/346
• US Class Current: 348/21
• CPC Class Codes: H03M 13/253 with concatenated codes
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H03M 13/2936 comprising an outer Reed-Solomon code and an inner convolutional code
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H03M 13/6538 ATSC VBS systems
• CPC Class Codes: H04N 19/89 involving methods or arrangements for detection of transmission errors at the decoder
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

An ATV receiver is provided with a 16-state trellis decoder to achieve improved performance in the presence of NTSC co-channel interference. In one embodiment, the ATV receiver comprises a tuner, a comb filter, and a trellis decoder. The tuner is configured to downmix a selected channel frequency signal to an intermediate frequency signal, where the comb filter is configurable to screen out most of the NTSC co-channel interference. The intermediate frequency receive signal is modified by the comb filter to resemble a partial response signal. The trellis decoder the demodulates the partial response signal in an improved fashion taking into account the state of the trellis encoder and the partial response channel. The trellis decoder may have a 16 state trellis comprised of four 4-state butterflies wherein each edge in the trellis is a single transition.

Claims

1. An ATV receiver with improved performance when subjected to NTSC co-channel interference, wherein the receiver comprises:

a tuner configured to downmix a selected channel frequency signal to an intermediate frequency signal;

a comb filter coupled to receive the intermediate frequency signal and configured to attenuate NTSC carrier frequencies from the intermediate frequency signal to produce a partial response signal;

a trellis decoder coupled to receive the partial response signal and configured to demodulate the partial response signal to produce decoded symbols using a 16 state trellis, wherein each stage of the 16 state trellis comprises four transitions leaving each state corresponding to four bipartite graphs such that each bipartite graph includes four source states and four destination states, and wherein an encoder state (S₀S₁) and partial response channel state (D) form the four bipartite graphs having the following sets of source states and destination states;

2. The ATV receiver of claim 1, wherein the 16 state trellis includes a state for every possible combination of trellis encoder state (S₀S₁) and partial response channel state (D).

3. The ATV receiver of claim 1, wherein in (I₁I₂R′

) form the transitions in the bipartite graphs have the following expected signal values and decode bits I₁I₂;

4. The ATV receiver of claim 1, wherein in (I₁I₂R′

) form the transitions in the bipartite graphs have the following expected signal values R′ and

decode bits I₁I₂;

5. A method for receiving an ATV transmission, wherein the method comprises:

downmixing a selected channel signal to an intermediate frequency signal;

filtering the intermediate frequency signal to screen out NTSC co-channel interference, wherein the filtering converts the intermediate frequency signal into a partial response signal;

converting the partial response signal into detected digital symbols, wherein the converting includes;

comparing a current partial response signal to an expected value for each transition in a trellis to determine a likelihood of a trellis path which includes that transition;

comparing all likelihoods of paths which end in common destination states to determine a most likely path to each destination state;

wherein the trellis includes 16 destination states, wherein each stage of the 16 state trellis comprises four transitions leaving each state corresponding to four bipartite graphs such that each bipartite graph includes four source states and four destination states, and wherein an encoder state (S₀S₁) and partial response channel state (D) form the four bipartite graphs having the following sets of source states and destination states;

6. The method of claim 5, wherein the 16-state trellis includes a destination state for every possible combination of encoder state and channel state.

7. The ATV receiver of claim 5, wherein in (I₁I₂R′

) form the transitions in the bipartite graphs have the following expected values R′ and

digital symbol values I₁I₂;

8. The ATV receiver of claim 5, wherein in (I₁I₂R′

) form the transitions in the bipartite graphs have the following expected values R and digital symbol values I₁I₂;

9. The method of claim 8, wherein the method further comprises transforming the detected digital symbols into digital audiovisual signals for presentation to an audience.

10. The method of claim 9, wherein the transforming includes:

de-interleaving the detected digital symbols to produce block encoded data packets;

decoding the encoded data packets to form error-corrected data packets; and

de-randomizing the error-corrected data packets to produce source data packets.

11. A Viterbi decoder which is usable to demodulate ATV transmission signals which have been filtered to reduce NTSC interference, wherein the decoder operates according to a 16 state trellis comprised of four bipartite graphs each having four source states and four destination states as follows:

12. The Viterbi decoder of claim 11, wherein the bipartite graphs have expected values R′

corresponding to transitions as follows;

13. The Viterbi decoder of claim 12, wherein the bipartite graphs have digital symbol values I₁I₂ corresponding to transitions as follows:

14. The Viterbi decoder of claim 12, wherein the bipartite graphs have digital symbol values I₁I₂ corresponding to transitions as follows: