Polar Code Puncturing Using Reliability-Based Nested Index Sets

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Solution Overview

Problem

Conventional Polar codes require codeword lengths to be a power of two, making it challenging to efficiently achieve desired codeword lengths through puncturing or repetition while maintaining performance, especially in wireless communication systems.

Innovation Solution

The method involves determining a set of indices for punctured code bits based on an ordered code-bit index sequence derived from the ordered bit-channel index sequence, allowing for flexible target block lengths without re-adjusting the information set, using nested sequences of puncturing patterns to select bit-channels and code-bit indices for data transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional Polar codes use fixed power-of-two codeword lengths, then code structure is simple and encoding is efficient, but adaptability to various target block lengths is poor

Engineering Contradiction:

Improveadaptability to target block lengthsVSAvoidcode structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The code bits are segmented into different groups based on their channel reliability rankings. The method divides the N code bits into information bits and frozen bits based on the ordered bit-channel index sequence, and further segments them for puncturing decisions. This segmentation allows flexible adaptation to different target block lengths while maintaining a structured approach to code construction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The puncturing pattern is made dynamic by using the ordered code-bit index sequence derived from bit-channel rankings. Instead of fixed puncturing patterns, the method dynamically selects which bits to puncture based on their reliability rankings, allowing the code to adapt to various target block lengths while maintaining optimal performance.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If puncturing is applied to achieve desired codeword lengths, then adaptability to various block lengths is improved, but performance degradation occurs due to catastrophic bit-channels

Engineering Contradiction:

Improveflexibility in codeword lengthVSAvoiddecoding performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The method performs preliminary ranking of bit-channels before encoding and puncturing. By determining the ordered bit-channel index sequence in advance and using it to generate the ordered code-bit index sequence, the system identifies which bits are most suitable for puncturing before the actual transmission. This preliminary action prevents catastrophic bit-channels from being punctured, thereby maintaining decoding performance while achieving flexible code lengths.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The method changes the parameter of bit selection by using reliability-based rankings instead of fixed position-based selection. By transforming the static code structure into a dynamic one where bit selection depends on channel conditions and reliability rankings, the system can adapt puncturing patterns to maintain performance across different code lengths.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If information set is re-adjusted for different code lengths, then performance is maintained, but computational effort and storage requirements increase

Engineering Contradiction:

Improvedecoding performanceVSAvoidstorage and computation requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ordered bit-channel index sequence serves multiple functions: it determines the information set for any code length, generates the ordered code-bit index sequence for puncturing, and provides the basis for both encoding and rate-matching operations. This universal sequence eliminates the need for separate information set adjustments for different code lengths, reducing both storage requirements and computational effort.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The method pre-computes and stores the ordered bit-channel index sequence once, which can then be reused for determining information sets and puncturing patterns across all code lengths. This preliminary action avoids repeated computation and storage of multiple information sets, significantly reducing device complexity while maintaining performance.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11184036B2Methods and devices for puncturing a polar code

Publication Date: 2021.11.23 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Methods and devices for puncturing of a polar code in a wireless network, wherein nested puncturing sets are determined based on a puncturing order which is determined based on a reliability order of information bit channels, so that only one index sequence needs to be stored for both the determination of the information set and the determination of the punctured set and so that puncturing does not require to adjust the information set at error prone indexes corresponding to puncturing indexes. The puncturing order might start with indexes corresponding to high reliability bit channels or to low reliability bit channels.