Polar Code Bit-Channel Ranking 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 reliability relationships among bit channels, which is not optimized for SC 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
1Reliability
If the traditional Polarization Weight (PW) sequence is used to determine information bit locations, then the coding structure is simple and universal, but the finite-length performance is not competitive with LDPC and Turbo codes
Solution Approach 1:
The patent applies local quality by creating code-length-specific information sequences rather than using a universal PW sequence. Each code length (e.g., N=64, 128, 256, 512) has its own optimized information sequence that tailors the bit channel selection to that specific length, improving finite-length performance for each case while accepting increased complexity in managing multiple sequences.
Solution Approach 2:
The patent changes the parameter of information sequence selection from a fixed universal PW sequence to variable code-length-specific sequences. This parameter change allows the system to adapt the information bit locations to match the specific code length being used, thereby optimizing performance for finite-length codes while maintaining the underlying polar coding structure.
2Reliability
If the PW sequence imposes artificial reliability relationships among bit channels, then the coding process is simplified, but the performance is not optimized for SCL decoders
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimized information sequences for various code lengths before actual encoding/decoding operations. These sequences are determined in advance through numerical optimization specifically tailored for SCL decoder performance, so that during operation, the system simply selects the appropriate pre-computed sequence rather than performing optimization in real-time.
Solution Approach 2:
The patent introduces dynamics by making the information sequence selection adaptive to the specific code length and SCL decoder configuration being used. Rather than a static universal sequence, the system dynamically selects from multiple pre-computed sequences that are optimized for different scenarios, allowing the information bit locations to adapt to the specific operating conditions.
3Reliability
If a universal information sequence is used for all code lengths, then the system is more adaptable and easier to implement, but the performance is not optimized for specific code lengths
Solution Approach 1:
The patent applies segmentation by dividing the universal information sequence problem into code-length-specific segments. Instead of one sequence for all N values, the patent creates separate optimized sequences for N=64, 128, 256, 512, and potentially other lengths. This segmentation allows each sequence to be optimized for its specific code length while the overall system maintains versatility by supporting multiple code lengths through sequence selection.
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.