# US 2014/0153628 A1 · Systems and methods for advanced iterative decoding and channel estimation of concatenated coding systems

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- Number: US 2014/0153628 A1
- Document ID: US20140153628A1
- Status: Published application
- Kind: A1
- Application number: 14/019,289
- Filed: 2013-09-05
- Published: 2014-06-05
- Earliest claimed: 2012-12-03
- Assignees: Digital PowerRadio, LLC
- Applicants: Digital PowerRadio, LLC
- Inventors: Branimir R. Vojcic; Hakan Dogan
- Web page: https://patentgrep.com/patent/US20140153628A1

## CPC

- H03M 13/1108: {Hard decision decoding, e.g. bit flipping, modified or weighted bit flipping}
- G06F 11/1625: {in communications, e.g. transmission, interfaces}
- H03M 13/1111: {Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms}
- H03M 13/112: {with correction functions for the min-sum rule, e.g. using an offset or a scaling factor}
- H03M 13/1131: {Scheduling of bit node or check node processing}
- H03M 13/114: {Shuffled, staggered, layered or turbo decoding schedules}
- H03M 13/1154: {Low-density parity-check convolutional codes [LDPC-CC]}
- H03M 13/1191: {Codes on graphs other than LDPC codes}
- H03M 13/1515: {Reed-Solomon codes}
- H03M 13/23: using convolutional codes, e.g. unit memory codes
- H03M 13/255: {with Low Density Parity Check [LDPC] codes}
- H03M 13/27: using interleaving techniques
- H03M 13/2792: {Interleaver wherein interleaving is performed jointly with another technique such as puncturing, multiplexing or routing}
- H03M 13/2906: {using block codes (H03M13/2957 takes precedence)}
- H03M 13/2933: {using a block and a convolutional code (H03M13/2957 takes precedence)}
- H03M 13/2948: {Iterative decoding (H03M13/2957 takes precedence)}
- H03M 13/3707: {Adaptive decoding and hybrid decoding, e.g. decoding methods or techniques providing more than one decoding algorithm for one code}
- 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}
- H03M 13/3746: {with iterative decoding}
- H03M 13/3784: {for soft-output decoding of block codes}
- H03M 13/45: Soft decoding, i.e. using symbol reliability information (H03M13/41 takes precedence)
- H03M 13/451: {using a set of candidate code words, e.g. ordered statistics decoding [OSD]}
- H03M 13/453: {wherein the candidate code words are obtained by an algebraic decoder, e.g. Chase decoding}
- H03M 13/612: {Aspects specific to channel or signal-to-noise ratio estimation (H03M13/63 takes precedence)}
- H03M 13/616: {Matrix operations, especially for generator matrices or check matrices, e.g. column or row permutations}
- H03M 13/6325: {Error control coding in combination with demodulation}
- H03M 13/6337: {Error control coding in combination with channel estimation}
- H03M 13/6541: {DVB-H and DVB-M}
- H03M 13/6552: {DVB-T2}
- H03M 13/658: {Scaling by multiplication or division}
- H04B 17/309: Measuring or estimating channel quality parameters
- H04L 1/004: {by using forward error control (H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00)}
- H04L 1/0045: {Arrangements at the receiver end}
- H04L 1/005: {Iterative decoding, including iteration between signal detection and decoding operation}
- H04L 1/0057: {Block codes (H04L1/0061, H04L1/0064 take precedence)}
- H04L 1/0059: {Convolutional codes}
- H04L 1/0065: {Serial concatenated codes}
- H04L 1/0071: {Use of interleaving (interleaving per se H03M13/27)}
- H04L 25/022: {of frequency response}
- H04L 25/0222: {Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency}
- H04L 25/0224: {using sounding signals}
- H04L 25/0236: {using estimation of the other symbols}
- H04L 27/261: {Details of reference signals}
- H04L 27/2649: {Demodulators}
- H03M 13/09: Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit
- H03M 13/3938: {Tail-biting (H03M13/2996 takes precedence)}
- H03M 13/6362: {by puncturing}
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## 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

### Claim 1

A method for iterative channel response estimation in a receiver of a multicarrier communication system that relies on forward-error-correction decoding, the method comprising:
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;
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;
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;
performing forward-error-correction decoding using said channel response estimate to obtain improved estimates of coded bits;
obtaining improved estimates of data symbols using said improved estimates of coded bits;
calculating an updated channel response estimate using a shorter filter length for at least one filter and a larger fraction of said data symbols; and
repeating the steps of performing forward-error-correction decoding and obtaining estimates of data symbols based on said updated channel response estimate, and calculating further updated channel response estimates based on improved estimates of data symbols.

### Claim 2 (depends on 1)

The method of claim 1 wherein at least one of said time and frequency selectivity is estimated using a level crossing rate estimate of said channel response.

### Claim 3 (depends on 1)

The method of claim 1 wherein at least one of said time and frequency selectivity is estimated using a rate of change estimate of said channel response.

### Claim 4 (depends on 1)

The method of claim 1 wherein said selected filter lengths are used to smooth said channel response.

### Claim 5 (depends on 1)

The method of claim 1 wherein said selected filter lengths are different for time and frequency domain processing.

### Claim 6 (depends on 1)

The method of claim 1 wherein a criterion for selecting said fraction of more reliable data symbols is based on at least one of the following:
the channel response at a given symbol position is larger than a first threshold; and
the signal-to-noise ratio or the signal-to-noise plus interference ratio at a given symbol position is larger than a second threshold.

### Claim 7 (depends on 6)

The method of claim 6 wherein at least one of said first and second thresholds is selected based on said estimated channel response time selectivity or frequency selectivity.

### Claim 8 (depends on 1)

The method of claim 1 further comprising estimating noise power using the following steps:
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;
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;
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
filtering said estimated noise power over time with a first filter length and over frequency with a second filter length.

### Claim 9 (depends on 8)

The method of claim 8 wherein said first filter length is selected according to time selectivity of noise or interference and where said second filter length is selected according to frequency selectivity of noise or interference.

### Claim 10 (depends on 1)

The method of claim 1 wherein said calculating of further updated channel response estimates is based on one or both of further decreasing the filter length and further increasing the fraction of data symbols.