Polar Code Information Sequences for Finite-Length SCL Decoding
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Solution Overview
Problem
Polar codes' finite-length performance under Successive Cancellation (SC) decoding is not competitive with other modern channel coding schemes like LDPC and Turbo codes, and the existing Polarization Weight (PW) sequence imposes artificial relationships among bit channel reliabilities, which is not optimized for Successive Cancellation List (SCL) decoders.
Innovation Solution
Numerically optimized information sequences for specific code lengths are developed, accounting for the performance of SCL decoders at different Block Error Rate (BLER) levels, which are used to map information bits to optimal bit locations in polar encoding and decoding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the Polarization Weight (PW) sequence is used to determine information bit locations, then the coding structure is simple and easy to implement, but the finite-length performance under SC decoding is not competitive with other modern channel coding schemes
Solution Approach 1:
The patent changes the parameter of information sequence ranking from the conventional Polarization Weight function to a numerically optimized sequence specifically designed for SCL decoding. This involves computing optimal bit-channel reliabilities through numerical optimization and using these to rank information bit locations, thereby improving finite-length performance while maintaining implementation feasibility through predefined sequences for standard code lengths.
2Device complexity
If the conventional PW sequence is used, then the information sequence can be generated using a simple weight function, but it imposes artificial relationships among bit channel reliabilities that are not optimized for SCL decoders
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing optimized information sequences for standard code lengths (e.g., N=64, 128, 256, 512, 1024) before actual communication operations. These sequences are calculated in advance through numerical optimization and then directly applied during encoding/decoding, eliminating the need for complex real-time computations while achieving optimal performance.
3Ease of operation
If information bits are mapped to suboptimal bit locations, then the encoding process is simpler, but the decoding reliability and error correction performance deteriorate
Solution Approach 1:
The patent applies local quality by optimizing the mapping of information bits to specific bit-channel locations based on their individual reliabilities. The optimized information sequences ensure that information bits are placed in the most reliable bit-channel positions for each specific code length and SCL list size configuration, maximizing the local quality of each bit position's contribution to overall decoding performance.
Data Source
AI summary
According to some embodiments, a method of operation of a transmit node in a wireless communication system comprises performing polar encoding of a set of K information bits to thereby generate a set of polar-encoded information bits. The K information bits are mapped to the first K bit locations in an information sequence SN. The information sequence SN is a ranked sequence of N information bit locations among a plurality of input bits for the polar encoding where N is equivalent to a code length. A size of the information sequence SN is greater than or equal to K. The information sequence SN is optimized for the specific value of the code length (N). The method may further comprise transmitting the set of polar-encoded information bits.