Enhanced VSB viterbi decoder

• US 20060104391A1
• Filed: 11/14/2005
• Published: 05/18/2006
• Est. Priority Date: 11/16/2004
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Choi, In Hwan, Kang, Kyong Won
• Granted Patent: US 7,933,365 B2
• Time in Patent Office: Days
• US Class Current: 375/341
• CPC Class Codes: H03M 13/2707 Simple row-column interleaver, i.e. pure block interleaving
• CPC Class Codes: H03M 13/3961 Arrangements of methods for branch or transition metric calculation
• CPC Class Codes: H03M 13/4107 implementing add, compare, select [ACS] operations
• CPC Class Codes: H03M 13/6331 Error control coding in combination with equalisation
• CPC Class Codes: H04L 27/02 Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation H04L27/32 takes precedence
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

An enhanced VSB receiver includes a tuner which tunes an RF signal and converts it into an IF signal, an IF mixer which converts the IF signal into a baseband signal, and a demodulator which demodulates the baseband signal signal into a VSB signal. The enhanced VSB receiver further includes a map recovery unit which recovers VSB map information of the VSB signal, an enhanced equalizer for compensating channel distortion of the VSB signal and outputting an equalized symbol, and an enhanced Viterbit decoder for estimating whether polarity inversion occurred during a symbol period of the equalized symbol and Viterbi-decoding the equalized symbol based on the polarity estimation.

Claims

1. A vestigial sideband (VSB) Viterbi decoder comprising:

a first accumulate/compare/select (ACS) unit for performing ACS operation for an input symbol assuming that polarity inversion did not occur during a symbol period of the input symbol;

a second accumulate/compare/select (ACS) unit for performing ACS operation assuming that polarity inversion occurred during the symbol period;

a polarity inversion estimator for estimating polarity of the input symbol;

a first path history unit for keeping track of a first path history of the input symbol by saving symbol survivors received from the first ACS unit;

a second path history unit for keeping track of a second path history of the input symbol by saving symbol survivors received from the second ACS unit; and

a decision selection unit for selecting one of decisions outputted from the first and second path history units based on the estimated polarity.

2. The VSB Viterbi decoder of claim 1, further comprising a branch metric calculator for calculating branch metrics of the input symbol corresponding to 8 reference levels and outputting the branch metrics to the first and second ACS units.

3. The VSB Viterbi decoder of claim 1, wherein the first and second ACS units perform ACS operation using symbol attributes which are outputted from a VSB data attribute generator.

4. The VSB Viterbi decoder of claim 3, wherein the symbol attributes include at least one of a first flag indicating whether the input symbol is a main symbol or an enhanced symbol, a second flag indicating whether the input symbol is a ½

-rate enhanced symbol or a ¼

-rate enhanced symbol, a third flag indicating whether the input symbol is from a recalculated RS parity, and a fourth flag indicating whether repeated bits of two ¼

enhanced symbols remain equal to or altered differently after data randomizing.

5. The VSB Viterbi decoder of claim 1, wherein the first and second path history units keep track of the first and second path histories of the input symbol, respectively, using symbol attributes which are outputted from a VSB data attribute generator.

6. The VSB Viterbi decoder of claim 1, wherein the polarity inversion estimator outputs a polarity signal selecting a minimum of minimum metrics outputted from the first and second ACS units, respectively.

7. The VSB Viterbi decoder of claim 1, wherein the first path history unit traces back a state having a minimum metric outputted from the first ACS unit.

8. The VSB Viterbi decoder of claim 1, wherein the second path history unit traces back a state having a minimum metric outputted from the second ACS unit.

9. The VSB Viterbi decoder of claim 1, further comprising a post decoder for post-decoding a C2 bit of the selected decision.

10. The VSB Viterbi decoder of claim 9, further comprising a multiplexer for outputting an X2 bit of the selected decision as an upper bit and outputting a dummy bit as a lower bit when the input symbol is an enhanced symbol.

11. The VSB Viterbi decoder of claim 9, further comprising a multiplexer for outputting an X1 bit of the selected decision as a lower bit and outputting the post-decoded C2 bit as an upper bit when the input symbol is a main symbol.

12. The VSB Viterbi decoder of claim 1, further comprising a symbol re-ordering unit for re-ordering the selected decision by 12-way symbol de-interleaving simultaneously.

13. A method of Viterbi-decoding an input symbol in a vestigial sideband (VSB) receiver, the method comprising:

performing first accumulate/compare/select (ACS) operation for an input symbol assuming that polarity inversion did not occur during a symbol period of the input symbol;

performing second ACS operation assuming that polarity inversion occurred during the symbol period;

estimating polarity of the input symbol;

keeping track of a first path history of the input symbol by saving symbol survivors resulted from the first ACS operation;

keeping track of a second path history of the input symbol by saving symbol survivors resulted from the second ACS operation; and

selecting one of decisions obtained from the first and second path histories based on the estimated polarity.

14. The method of claim 13, further comprising calculating branch metrics of the input symbol corresponding to 8 levels, wherein the first and second ACS operations are performed using the branch metrics of the input symbol.

15. The method of claim 13, wherein the first and second ACS operations are performed using symbol attributes outputted from a VSB data attribute generator.

16. The method of claim 15, wherein the symbol attributes include at least one of a first flag indicating whether the input symbol is a main symbol or an enhanced symbol, a second flag indicating whether the input symbol is a ½

-rate enhanced symbol or a ¼

-rate enhanced symbol, a third flag indicating whether the input symbol is from a recalculated RS parity, and a fourth flag indicating whether repeated bits of two ¼

enhanced symbols remain equal to or altered differently after data randomizing.

17. The method of claim 13, wherein the estimating polarity of the input symbol comprises selecting a minimum of minimum metrics resulted from the first and second ACS operations.

18. The method of claim 13, wherein the keeping track of a first path history of the input symbol comprises tracing back a state having a minimum metric resulted from the first ACS operation.

19. The method of claim 13, wherein the keeping track of a second path history of the input symbol comprises tracing back a sate having a minimum metric resulted from the second ACS operation.

20. The method of claim 13, further comprising post-decoding a C2 bit of the selected decision.

21. The method of claim 20, further comprising outputting an X2 bit of the selected decision as a upper bit and outputting a dummy bit as a lower bit when the input symbol is an enhanced symbol.

22. The method of claim 20, further comprising outputting an X1 bit of the selected decision as a lower bit and the post-decoded C2 bit as an upper bit when the input bit is a main symbol.

23. The method of claim 13, further comprising re-ordering the selected decision by 12-way symbol de-interleaving simultaneously.

24. A vestigial sideband (VSB) receiver, comprising:

a tuner for tuning an RF signal and converting the RF signal into an IF signal;

a demodulator for demodulating the IF signal to a VSB signal;

a map recovery unit for recovering VSB map information of the VSB signal;

an enhanced equalizer for compensating channel distortion of the VSB signal and outputting an equalized symbol; and

an enhanced Viterbi decoder for estimating whether polarity inversion occurred during a symbol period of the equalized symbol and Viterbi-decoding the equalized symbol based on the polarity estimation.

25. The VSB receiver of claim 24, wherein the Viterbi decoder comprises:

a first accumulate/compare/select (ACS) unit for performing ACS operation for the equalized symbol assuming that polarity inversion did not occur during the symbol period;

a second accumulate/compare/select (ACS) unit for performing ACS operation assuming that polarity inversion occurred during the symbol period;

a polarity inversion estimator for estimating polarity of the equalized symbol;

a first path history unit for keeping track of a first path history of the equalized symbol by saving symbol survivors received from the first ACS unit;

a second path history unit for keeping track of a second path history of the equalized symbol by saving symbol survivors received from the second ACS unit; and

a decision selection unit for selecting one of decisions outputted from the first and second path history units based on the estimated polarity.

26. A method of decoding a digital broadcast signal, the method comprising:

tuning an RF signal and converting the RF signal into an IF signal;

demodulating the IF signal to a VSB signal;

recovering VSB map information of the VSB signal;

equalizing the VSB signal by compensating channel distortion of the VSB signal and outputting an equalized symbol; and

Viterbi-decoding the equalized symbol based upon estimating whether polarity inversion occurred during a symbol period of the equalized symbol.

27. The method of claim 26, wherein the Viterbi-decoding the equalized symbol comprises:

performing first accumulate/compare/select (ACS) operation for the equalized symbol assuming that polarity inversion did not occur during the symbol period;

performing second ACS operation assuming that polarity inversion occurred during the symbol period;

estimating polarity of the equalized symbol;

keeping track of a first path history of the equalized symbol by saving symbol survivors resulted from the first ACS operation;

keeping track of a second path history of the equalized symbol by saving symbol survivors resulted from the second ACS operation; and

selecting one of decisions obtained from the first and second path histories based on the estimated polarity.