Polar Code CRC Interleaving for Early Error Detection

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Solution Overview

Problem

The finite-length performance of polar codes under successive cancellation decoding is not competitive with other modern channel coding schemes like LDPC and Turbo codes, and the two-step decoding process with CRC codes is sub-optimal and increases decoding latency.

Innovation Solution

Applying a specific bit-interleaver with a predetermined interleaving pattern between a linear outer CRC code and a polar inner code, allowing for early termination of decoding and single-step decoding that accounts for the structure of both codes, reducing latency and false-alarm rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a two-step decoding process with CRC codes is used, then decoding performance is improved, but decoding latency increases

Engineering Contradiction:

Improvedecoding performanceVSAvoiddecoding latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the CRC code into multiple distributed CRC bits that are interleaved with information bits. This allows the decoder to perform early error detection at multiple points during decoding rather than waiting for complete decoding, thereby reducing latency while maintaining performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary error detection by placing CRC bits at strategic positions throughout the code block. The decoder can detect errors early in the decoding process and terminate prematurely, avoiding the need to complete the full two-step decoding process and reducing overall latency.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If all CRC bits are attached at the end of the code block, then implementation is simplified, but early error detection capability is lost

Engineering Contradiction:

Improveimplementation simplicityVSAvoidearly error detection capability

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The patent divides the single block of CRC bits at the end into multiple distributed CRC bits that are interleaved with information bits throughout the code block. This segmentation enables early error detection at multiple positions while maintaining a systematic approach to implementation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from a one-dimensional arrangement (all CRC bits at the end) to a two-dimensional interleaved arrangement where CRC bits are distributed across different positions in the code block. This dimensional change enables early error detection without significantly complicating the implementation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11165442B2CRC interleaving pattern for polar codes

Publication Date: 2021.11.02 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

According to some embodiments, a method of operation of a wireless transmitter in a wireless communication network comprises: encoding a set of information carrying data bits u of length K with a linear outer code to generate a set of outer parity bits p along with the data bits u; interleaving the set of outer parity bits p and the data bits u using a predetermined interleaving mapping function that depends on the number of data bits K and is operable to distribute some bits of the set of parity bits p in front of some data bits u; and encoding the interleaved bits using a Polar encoder to generate a set of encoded bits x. Various interleaving mapping functions are disclosed.