Stopping criteria for turbo decoder

Patent metadata

Field	Value
Publication number	US-10567008-B2
Application number	US-201615174413-A
Country	US
Kind code	B2
Filing date	Jun 6, 2016
Priority date	Jul 2, 2015
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

This disclosure relates to providing negative stopping criteria for turbo decoding for a wireless device. A device may wirelessly receive turbo coded data. Turbo decoding may be performed on the turbo coded data. Performing turbo decoding may use one or more negative stopping criteria for early termination of the turbo decoding for each code block of the turbo coded data. The negative stopping criteria may be selected to terminate the turbo decoding of a code block early under poor wireless medium conditions. Turbo decoding of a code block may be terminated early if the one or more negative stopping criteria for the code block are met.

First claim

What is claimed is:

1. A wireless device, comprising:
a radio;
a processing element coupled to the radio;
wherein the radio and the processing element are configured to:
wirelessly receive turbo coded data;
perform turbo decoding on the turbo coded data,
wherein performing turbo decoding uses one or more negative stopping criteria for early termination of unsuccessful turbo decoding for each code block of the turbo coded data, wherein the one or more negative stopping criteria are selected to terminate the unsuccessful turbo decoding of a code block early under poor wireless medium conditions, wherein the one or more negative stopping criteria are based at least in part on computed a priori likelihood ratios of information bits of the turbo coded data; and
terminate the unsuccessful turbo decoding of a code block early if the one or more negative stopping criteria for the code block are met.

2. The wireless device of claim 1 ,
wherein a first negative stopping criterion comprises a value of a metric being below a first threshold after a first number of turbo decoding iterations.

3. The wireless device of claim 2 , wherein a second negative stopping criterion comprises the value of the metric being below a second threshold after a second number of turbo decoding iterations.

4. The wireless device of claim 1 , wherein a negative stopping criterion of the one or more negative stopping criteria comprises a value of a metric being below a variable threshold at a turbo decoding iteration, wherein the variable threshold is a function of the turbo decoding iteration.

5. The wireless device of claim 1 , wherein a negative stopping criterion of the one or more negative stopping criteria comprises a value of a metric at a turbo decoding iteration being below or equal to the value of the metric at a preceding turbo decoding iteration, for any turbo decoding iteration starting at a predetermined turbo decoding iteration.

6. The wireless device of claim 1 , wherein a negative stopping criterion of the one or more negative stopping criteria comprises a value of a metric at a turbo decoding iteration being below or equal to the value of the metric at a preceding turbo decoding iteration, for any of a selected subset of turbo decoding iterations.

7. The wireless device of claim 1 ,
wherein the one or more negative stopping criteria are based at least in part on an average absolute extrinsic information (AAEXI) metric, wherein the AAEXI metric is defined as:

1
C

⁢

∑

i
=
0

C
-
1

⁢



L
e

⁡

(
i
)



,

wherein C comprises a number of bits in a code block,
wherein L e comprises a likelihood ratio of an information bit in a code block as computed by a constituent turbo decoder and used as a priori likelihood ratio of the information bit by the other constituent turbo decoder in its next iteration.

8. The wireless device of claim 1 ,
wherein performing turbo decoding also uses one or more positive stopping criteria for early termination of the turbo decoding for each code block of the turbo coded data, wherein a first positive stopping criterion comprises an appended cyclic redundancy check value of a code block successfully checking against a cyclic redundancy check value calculated from decoded information bits of the code block.

9. The wireless device of claim 1 , wherein the radio and the processing element are further configured to:
monitor a metric that is based at least in part on computed a priori likelihood ratios of information bits of the turbo coded data; and
select when to check whether a positive stopping criterion is met based at least in part on a value of the metric.

10. The wireless device of claim 1 ,
wherein the one or more negative stopping criteria are selected based at least in part on design characteristics of one or more of the wireless device or a wireless device from which the turbo coded data was received.

11. An apparatus, comprising a processing element configured to cause a wireless device to:
wirelessly receive a code block of turbo coded data;
performing turbo decoding of the code block of turbo coded data for up to a predetermined maximum duration;
determine whether any of one or more positive stopping criteria or one or more negative stopping criteria for the turbo decoding have been met prior to the predetermined maximum duration,
wherein the turbo decoding of the code block of turbo coded data is stopped upon meeting a positive stopping criterion, a negative stopping criterion, or the predetermined maximum duration,
wherein the one or more positive stopping criteria, the one or more negative stopping criteria, and the predetermined maximum duration are configured to cause a duration of the turbo decoding of the code block to vary in a manner correlated with wireless medium conditions when receiving the code block of turbo coded data, and
in response to one or more negative stopping criteria being met, terminate turbo decoding without successfully decoding the turbo coded data.

12. The apparatus of claim 11 ,
wherein the one or more positive stopping criteria, the one or more negative stopping criteria, and the predetermined maximum duration are configured to cause the duration of the turbo decoding of the code block to be shorter in poor and good wireless medium conditions than in moderate medium conditions,
wherein the poor wireless medium conditions comprise a signal to interference to noise (SINR) region below a first threshold,
wherein the good wireless medium conditions comprise a SINR region above a second threshold,
wherein the moderate wireless medium conditions comprise a SINR region between the first threshold and the second threshold.

13. The apparatus of claim 11 ,
wherein the predetermined maximum duration is selected based at least in part on a device class of a device from which the code block of turbo coded data is received,
wherein a higher predetermined maximum duration is selected when the device class of the device from which the code block of turbo coded data comprises a link budget limited device class than when the device class of the device from which the code block of turbo coded data comprises a non link budget limited device class.

14. The apparatus of claim 11 ,
wherein the predetermined maximum duration is selected based at least in part on wireless medium conditions between the wireless device and the device from which the code block of turbo coded data is received,
wherein a higher predetermined maximum duration is selected when the wireless medium conditions are poor than when the wireless medium conditions are good.

15. The apparatus of claim 11 ,
wherein the one or more negative

Assignees

• Apple Inc

Inventors

• Hussain Awais M
• Tabet Tarik
• Elsayed Moustafa M

Classifications

• H04L1/0051

  Stopping criteria · CPC title

• H03M13/09

  Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit · CPC title

• H04B17/336

  Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] · CPC title

• H03M13/2975 Primary

  Judging correct decoding, e.g. iteration stopping criteria · CPC title

• H04W88/02

  Terminal devices · CPC title