SYSTEMS AND METHODS FOR ADVANCED ITERATIVE DECODING AND CHANNEL ESTIMATION OF CONCATENATED CODING SYSTEMS

• US 20140376650A1
• Filed: 07/29/2014
• Published: 12/25/2014
• Est. Priority Date: 12/03/2012
• Status: Active Grant

• Current Assignee: Digital PowerRadio, LLC
• Original Assignee: Digital PowerRadio, LLC
• Inventors: Vojcic, Branimir R., Dogan, Hakan
• Granted Patent: US 9,838,154 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: G06F 11/1625 in communications, e.g. transmission, interfaces
• CPC Class Codes: H03M 13/09 Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit
• CPC Class Codes: H03M 13/1108 Hard decision decoding, e.g. bit flipping, modified or weighted bit flipping
• CPC Class Codes: H03M 13/1111 Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms
• CPC Class Codes: H03M 13/112 with correction functions for the min-sum rule, e.g. using an offset or a scaling factor
• CPC Class Codes: H03M 13/1131 Scheduling of bit node or check node processing
• CPC Class Codes: H03M 13/114 Shuffled, staggered, layered or turbo decoding schedules
• CPC Class Codes: H03M 13/1154 Low-density parity-check convolutional codes [LDPC-CC]
• CPC Class Codes: H03M 13/1191 Codes on graphs other than LDPC codes
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/23 using convolutional codes, e.g. unit memory codes
• CPC Class Codes: H03M 13/255 with Low Density Parity Check [LDPC] codes
• CPC Class Codes: H03M 13/27 using interleaving techniques
• CPC Class Codes: H03M 13/2792 Interleaver wherein interleaving is performed jointly with another technique such as puncturing, multiplexing or routing
• CPC Class Codes: H03M 13/2906 using block codes H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2933 using a block and a convolutional code H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2948 Iterative decoding H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/3707 Adaptive decoding and hybrid decoding, e.g. decoding methods or techniques providing more than one decoding algorithm for one code
• CPC Class Codes: H03M 13/373 with erasure correction and erasure determination, e.g. for packet loss recovery or setting of erasures for the decoding of Reed-Solomon codes
• CPC Class Codes: H03M 13/3746 with iterative decoding
• CPC Class Codes: H03M 13/3784 : for soft-output decoding of block codes
• CPC Class Codes: H03M 13/3938 : Tail-biting H03M13/2996 takes precedence
• CPC Class Codes: H03M 13/45 : Soft decoding, i.e. using symbol reliability information H03M13/41 takes precedence
• CPC Class Codes: H03M 13/451 : using a set of candidate code words, e.g. ordered statistics decoding [OSD]
• CPC Class Codes: H03M 13/453 : wherein the candidate code words are obtained by an algebraic decoder, e.g. Chase decoding
• CPC Class Codes: H03M 13/612 : Aspects specific to channel or signal-to-noise ratio estimation H03M13/63 takes precedence
• CPC Class Codes: H03M 13/616 : Matrix operations, especially for generator matrices or check matrices, e.g. column or row permutations
• CPC Class Codes: H03M 13/6325 : Error control coding in combination with demodulation
• CPC Class Codes: H03M 13/6337 : Error control coding in combination with channel estimation
• CPC Class Codes: H03M 13/6362 : by puncturing
• CPC Class Codes: H03M 13/6541 : DVB-H and DVB-M
• CPC Class Codes: H03M 13/6552 : DVB-T2
• CPC Class Codes: H03M 13/658 : Scaling by multiplication or division
• CPC Class Codes: H04B 17/309 : Measuring or estimating channel quality parameters
• CPC Class Codes: H04L 1/004 : by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0045 : Arrangements at the receiver end
• CPC Class Codes: H04L 1/005 : Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0057 : Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0059 : Convolutional codes
• CPC Class Codes: H04L 1/0065 : Serial concatenated codes
• CPC Class Codes: H04L 1/0071 : Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 25/022 : of frequency response
• CPC Class Codes: H04L 25/0222 : Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
• CPC Class Codes: H04L 25/0224 : using sounding signals
• CPC Class Codes: H04L 25/0236 : using estimation of the other symbols
• CPC Class Codes: H04L 27/261 : Details of reference signals
• CPC Class Codes: H04L 27/2649 : Demodulators
• CPC Class Codes: H05K 999/99 : dummy group

Abstract

Systems and methods for decoding block and concatenated codes are provided, including channel state information estimation such as by using optimum filter lengths based on channel selectivity and adaptive decision-directed channel estimation. These improvements enhance the performance of various communication systems and consumer electronics, including HD Radio receivers and systems.

Claims

1. A communication system with adaptive pilot symbol structure comprising:

a. a measurement device in a receiver that measures one or more signal attributes of a signal received over a first communication channel;

b. a processing device that analyzes said measurements of one or more received signal attributes to determine a preferred pilot symbol structure, wherein the preferred pilot symbol structure is selected from at least two possible pilot symbol structures; and

c. a transmitting device that conveys via a second communication channel to a transmitter of said received signal that was measured in the receiver an indicator of preferred pilot symbol structure.

2. The system of claim 1 wherein the one or more signal attributes comprise time selectivity of the first communication channel.

3. The system of claim 1 wherein the one or more signal attributes is selected from the group consisting of signal-to-noise ratio, received signal power and received signal strength indicator.

4. The system of claim 1 wherein the one or more signal attributes include at least time selectivity and an indication of signal strength.

5. The system of claim 1 wherein the processing device determines said preferred pilot symbol structure using said measurements of one or more signal attributes and one or more look-up tables.

6. The system of claim 1 wherein the processing device determines said preferred pilot symbol structure using said measurements of one or more signal attributes and one or more thresholds.

7. The system of claim 1 wherein said indicator consists of one or more bits transmitted as a separate data field.

8. The system of claim 1 wherein said indicator is combined with another indicator into an integrated indicator supporting adaptive communication between the transmitter and the receiver over the said first communication channel.

9. A method for estimating channel response in a receiver of a multicarrier communication system comprising:

a. selecting filter lengths for time and frequency domain channel estimation based on estimated time selectivity and frequency selectivity of said channel response wherein said time selectivity and frequency selectivity are estimated using at least one of known pilot symbols and unknown data symbols;

b. estimating said channel response using said selected filter lengths by using available pilot symbols and a first set of data symbols, the first set of data symbols being selected as a fraction of data symbols that are more reliable than a remaining fraction of data symbols in a second set of data symbols that are considered less reliable; and

c. with respect to symbol positions corresponding to said second set of data symbols, estimating the channel response by interpolation based on estimated values of channel response obtained from said pilot symbols and said first set of data symbols.

10. The method of claim 9 wherein said time or frequency selectivity is estimated using a level crossing rate estimate of said channel response.

11. The method of claim 9 wherein said time or frequency selectivity is estimated using a rate of change estimate of said channel response.

12. The method of claim 9 wherein said selected filter lengths for channel response estimation are different for time and frequency domain processing.

13. The method of claim 9 wherein a criterion for selecting said fraction of more reliable data symbols is based on at least one of the following:

a. the channel response at a given symbol position is larger than a first threshold; and

b. the signal-to-noise ratio or the signal-to-noise plus interference ratio at a given symbol position is larger than a second threshold.

14. The method of claim 13 wherein at least one of said first and second thresholds is selected based on said estimated channel response time selectivity or frequency selectivity.

15. A method for estimating noise power by first obtaining a channel response estimate using the method of claim 9, the method for estimating noise power further comprising:

a. estimating noise samples on the positions of said known pilot symbols by subtracting from received noisy symbol samples the product of the corresponding estimated channel response and the pilot symbol values;

b. estimating noise samples on the positions of said first set of data symbols by subtracting from the received noisy symbol samples the product of the corresponding estimated channel response and the estimated values of the first set of data symbols;

c. estimating the power of said estimated noise samples by either calculating the squared magnitude of said estimated noise samples, or by squaring real and imaginary parts of said estimated noise samples; and

d. filtering said estimated noise power over time with a first filter length and over frequency with a second filter length.

16. The method of claim 15 wherein said first filter length is selected according to time selectivity of noise and/or interference and where said second filter length is selected according to frequency selectivity of noise and/or interference.

17. The method of claim 9 wherein said selected filter lengths are used to smooth said channel response.

18. The method of claim 17 wherein said selected filter lengths for smoothing of said channel response are different for time and frequency domain processing.

19. A method for iterative channel state estimation in a multicarrier communication system with forward error correction wherein an initial channel response estimate and an initial noise power estimate are obtained using the method of claim 15, the method for iterative channel response estimation further comprising at least one iteration of the following steps:

a. performing forward error correction decoding using said initial channel response estimate to obtain improved estimates of coded bits;

b. obtaining estimates of data symbols using said improved estimates of coded bits; and

c. calculating an updated channel response estimate using a shorter filter length for at least one filter and a larger fraction of said data symbols.

20. The method of claim 19 further comprising performing another iteration of forward error correction decoding and obtaining updated estimates of data symbols based on said updated channel response estimate, and calculating a further updated channel response estimate based on one or both of further decreasing the length of one or more filters and increasing the fraction of data symbols.

21. A method for estimating channel response in a receiver of a single carrier communication system comprising:

a. selecting a filter length for time domain channel estimation based on estimated time selectivity of said channel response wherein the said time selectivity is estimated using at least one of known pilot symbols and unknown data symbols;

b. estimating said channel response using said selected filter length by using available pilot symbols and a first set of data symbols, the first set of data symbols being selected as a fraction of data symbols that are more reliable than a remaining fraction of data symbols in a second set of data symbols that are considered less reliable; and

c. with respect to symbol positions corresponding to said second set of data symbols, estimating the channel response by interpolation based on estimated values of channel response obtained from said pilot symbols and said first set of data symbols.

22. The method of claim 21 wherein said time selectivity is estimated using a level crossing rate estimate of said channel response.

23. The method of claim 21 wherein the said time selectivity is estimated using a rate of change estimate of said channel response.

24. The method of claim 21 wherein a criterion for selecting the said fraction of more reliable data symbols is based on at least one of the following:

a. the channel response at a given symbol position is larger than a first threshold; and

b. the signal-to-noise ratio or the signal-to-noise plus interference ratio at a given symbol position is larger than a second threshold.

25. The method of claim 24 wherein at least one of said first and second thresholds is selected based on said estimated channel response time selectivity.

26. A method for estimating noise power by first obtaining a channel response estimate using the method of claim 21, the method for estimating noise power further comprising:

a. estimating noise samples on the positions of said known pilot symbols by subtracting from the received noisy symbol samples the product of the corresponding estimated channel response and the pilot symbol values;

b. estimating noise samples on the positions of said first set of data symbols by subtracting from the received noisy symbol samples the product of the corresponding estimated channel response and the estimated values of the first set of data symbols;

c. estimating the power of said estimated noise samples by either calculating the squared magnitude of said estimated noise samples, or by squaring real and the imaginary parts of said estimated noise samples; and

d. filtering said estimated noise power over time with a selected filter length.

27. The method of claim 26 wherein said selected filter length is selected accordingly to time selectivity of noise and/or interference.

28. The method of claim 21 wherein said selected filter length is used to smooth said channel response.

29. A method for iterative channel state estimation in a single carrier communication system with forward error correction wherein an initial channel response estimate and an initial noise power estimate are obtained using the method of claim 26, the method for iterative channel response estimation further comprising at least one iteration of the following steps:

a. performing forward error correction decoding using said initial channel response estimate to obtain improved estimates of coded bits;

b. obtaining estimates of data symbols using said improved estimates of coded bits; and

c. calculating an updated channel response estimate using a shorter filter length for at least one filter and a larger fraction of said data symbols.

30. The method of claim 29 further comprising performing another iteration of forward error correction decoding and obtaining updated estimates of data symbols based on said updated channel response estimate, and calculating a further updated channel response estimate based on one or both of further decreasing the length of one or more filters and increasing the fraction of data symbols.