Polar Code Length Adaptation with Puncturing and HARQ Extension
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Solution Overview
Problem
Polar codes are inflexible in terms of codeword length and inefficient in decoding, limiting their adaptability to varying channel conditions and throughput constraints, with existing techniques for modifying their length either increasing decoding complexity or reducing correction capability.
Innovation Solution
A method and device that utilize punctured shortened polar codes optimized for pre-selected modulation, generating extension bits for hybrid automatic repeat request (HARQ) schemes, allowing for variable codeword lengths with low decoding complexity and error correction, while maintaining the efficiency of original polar codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polar codes are used with fixed power of two lengths, then decoding complexity is reduced and error correction capability is improved, but adaptability to varying channel conditions and throughput constraints deteriorates
Solution Approach 1:
The code is segmented into information bits and frozen bits in the input vector, with the intermediate codeword further segmented to identify which bits to puncture and shorten. This segmentation allows flexible code length adaptation while maintaining the structured decoding process of polar codes.
Solution Approach 2:
Specific bits are extracted and removed from the intermediate codeword according to a predetermined pattern - frozen bits are shortened and other bits are punctured. This extraction enables variable code length without requiring complete re-encoding, thus reducing decoding complexity while improving adaptability.
2Adaptability or versatility
If code length is modified to achieve variable lengths, then adaptability to throughput constraints is improved, but decoding efficiency deteriorates
Solution Approach 1:
The pattern for puncturing and shortening is predetermined based on the desired code length and rate. This preliminary determination of which bits to remove avoids complex real-time decisions during decoding, maintaining decoding efficiency while enabling flexible code length adaptation for different throughput requirements.
3Adaptability or versatility
If punctured and shortened bits are removed to achieve variable lengths, then code flexibility is improved, but correction capability deteriorates
Solution Approach 1:
Different types of bits are treated differently in the puncturing and shortening process. Frozen bits (which provide structural support for error correction) are shortened rather than punctured, while information bits are selectively punctured. This local differentiation maintains error correction capability while achieving code flexibility.
Data Source
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AI summary
According to the present invention, an input vector for polar encoding is computed (201), wherein the input vector comprises a set of information bits and a set of frozen bits, and an intermediate codeword is generated (202) by executing a polar encoding of the input vector. Further, punctured and shortened bits are removed (203) from the intermediate codeword, to obtain a reduced intermediate codeword, and an output codeword is generated (204) by applying a permutation operation oh the reduced intermediate codeword. A sequence of extension bits is selected (205) from the intermediate codeword bits and information bits, and modulated symbols are generated (206) by applying bitmapping on the output codeword and on the sequence of extension bits. The invention can be employed in an Hybrid ARQ system.