# US 8,543,883 B2 · Decoding low-density parity check (LDPC) codewords

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- Number: US 8,543,883 B2
- Document ID: US8543883B2
- Status: Granted
- Kind: B2
- Application number: 13/607,609
- Filed: 2012-09-07
- Published: 2013-01-03
- Granted: 2013-09-24
- Earliest claimed: 2008-12-30
- Assignees: QUALCOMM Incorporated
- Applicants: Qifan Chen; Ning Zhang
- Inventors: Qifan Chen; Ning Zhang
- Web page: https://patentgrep.com/patent/US8543883B2

## CPC

- H03M 13/1128: {Judging correct decoding and iterative stopping criteria other than syndrome check and upper limit for decoding iterations}
- H03M 13/114: {Shuffled, staggered, layered or turbo decoding schedules}
- H03M 13/353: {Adaptation to the channel}
- H03M 13/356: {Unequal error protection [UEP]}
- H03M 13/6527: {IEEE 802.11 [WLAN]}
- H03M 13/6544: {IEEE 802.16 (WIMAX and broadband wireless access)}
- H03M 13/658: {Scaling by multiplication or division}
- H03M 13/1165: {QC-LDPC codes as defined for the digital video broadcasting [DVB] specifications, e.g. DVB-Satellite [DVB-S2]}
- H03M 13/23: using convolutional codes, e.g. unit memory codes
- H03M 13/41: using the Viterbi algorithm or Viterbi processors
- 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)

## Abstract

A low-density parity-check (LDPC) codeword is decoded by performing a partial parity check, and based on the partial parity check, determining whether an iteration condition is met. Determining whether the iteration condition is met includes determining whether a time to decode a last codeword is approaching. Determining whether the iteration condition is met can additionally include determining whether a number of partial iterations reaches a maximum number of iterations and/or determining whether hardware resources are becoming limited. If the iteration condition is met, a decoding result is reported. If the iteration condition is not met, then a plurality of check nodes are updated and a parity check is performed.

## Claims

### Claim 1

A method of decoding a low-density parity-check (LDPC) codeword, the method comprising:
performing a partial parity check;
based on the partial parity check, determining whether an iteration condition is met, wherein determining whether the iteration condition is met includes determining whether a time to decode a last codeword is approaching;
when the iteration condition is met, reporting a decoding result; and
when the iteration condition is not met, updating a plurality of check nodes and performing a parity check.

### Claim 2 (depends on 1)

The method of claim 1, wherein determining whether the iteration condition is met includes determining whether a number of partial iterations is equal to a maximum number of iterations.

### Claim 3 (depends on 2)

The method of claim 2, further including storing the maximum number of iterations as a dynamic value.

### Claim 4 (depends on 2)

The method of claim 2, further including performing a simulation, and storing a result of the simulation as the maximum number of iterations.

### Claim 5 (depends on 1)

The method of claim 1, wherein determining whether the iteration condition is met includes determining whether hardware resources are limited.

### Claim 6 (depends on 5)

The method of claim 5, wherein determining whether hardware resources are limited includes monitoring a buffer level and indicating the hardware resources are limited when the buffer level is approaching full.

### Claim 7 (depends on 1)

The method of claim 1, wherein determining whether the time to decode the last codeword is approaching is based on a short interframe space (SIFS).

### Claim 8 (depends on 1)

The method of claim 1, wherein determining whether the time to decode the last codeword is approaching is based on a power amplifier activation time.

### Claim 9 (depends on 1)

The method of claim 1, wherein reporting the decoding result includes decoding of an OFDM transmission.

### Claim 10

A system for decoding a low-density parity-check (LDPC) codeword, the system comprising:
a partial parity check module configured to perform a partial parity check based on updates to a portion of variable nodes;
an iteration condition checker coupled to the partial parity check module and configured to determine whether an iteration condition of a plurality of iteration conditions has been met, wherein the iteration condition checker is configured based on a latency to decode a last codeword; and
an iteration condition storage module configured to store at least one iteration condition.

### Claim 11 (depends on 10)

The system of claim 10, further comprising:
a last code word checker configured to determine whether a codeword being received is a last codeword of a transmission, the last code word checker coupled to the iteration condition checker.

### Claim 12 (depends on 10)

The system of claim 10, wherein the iteration condition checker is configured to monitor a buffer usage level.

### Claim 13 (depends on 10)

The system of claim 10, wherein the iteration condition checker is configured to check results of the partial parity check module.

### Claim 14 (depends on 10)

The system of claim 10, wherein the iteration condition checker is configured to report a decoding result based on a maximum number of partial iterations being performed, the maximum number of partial iterations being stored as the at least one iteration condition.

### Claim 15

A system for decoding a low-density parity-check (LDPC) codeword, the system comprising:
a partial parity check module configured to perform a partial parity check based on updates to a portion of variable nodes;
an iteration condition checker coupled to the partial parity check module, wherein the iteration condition checker is configured to determine whether an iteration condition of a plurality of iteration conditions has been met, and to report a decoding result based on a maximum number of partial iterations being performed, the maximum number of partial iterations being based on a latency to decode a last codeword; and
an iteration condition storage module configured to store at least one iteration condition.

### Claim 16

A computer-readable, non-transitory media comprising instructions therein that, when executed by a processor, implement a method of decoding a low-density parity check (LDPC) codeword, the method comprising:
performing a partial parity check;
based on the partial parity check, determining whether an iteration condition is met, wherein determining whether the iteration condition is met includes determining whether a time to decode a last codeword is approaching;
when the iteration condition is met, reporting a decoding result; and
when the iteration condition is not met, updating a plurality of check nodes and performing a parity check.

### Claim 17 (depends on 16)

The computer-readable media of claim 16, wherein the computer-readable media comprises a firmware update.

### Claim 18 (depends on 16)

A computer-readable media of claim 16, wherein the decoding result is a decoding of an 802.11n transmission.