Polar Code Soft-Output Decoding for SIC Receivers
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Solution Overview
Problem
Existing polar code decoders do not generate soft output for code bits, which are essential for successive interference cancellation (SIC) receivers and advanced iterative demodulation and decoding processes, limiting their performance in wireless communication systems.
Innovation Solution
A method and system for generating soft information for code bits of polar codes using a tree structure within the decoder, allowing for the reverse propagation of log likelihood ratios (LLRs) to produce soft outputs that can be utilized by other modules or processors, enabling improved performance in SIC receivers and iterative demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If successive cancellation (SC) decoding is used for polar codes, then decoding complexity is kept low, but soft output for code bits cannot be generated
Solution Approach 1:
The decoding process is segmented into two distinct phases: a forward pass that computes information bit estimates using SC decoding, and a backward pass that propagates soft information from information bits to code bits. This segmentation allows the decoder to maintain low complexity during the forward pass while generating soft outputs during the backward pass, resolving the contradiction between low complexity and soft output capability.
Solution Approach 2:
Instead of generating soft information for code bits during the forward decoding process, the patent inverts the approach by first completing the forward SC decoding to obtain information bit estimates, then propagating this soft information backward through the polar code structure to derive code bit soft outputs. This inversion enables soft output generation without increasing forward decoding complexity.
2Reliability
If soft output generation is implemented in polar code decoders, then performance in SIC receivers and iterative demodulation is improved, but decoder complexity increases
Solution Approach 1:
The forward SC decoding is performed as a preliminary action to obtain accurate information bit estimates before the soft information propagation to code bits begins. This preliminary computation of reliable information bit soft values provides a solid foundation for the subsequent backward pass, ensuring high decoding performance while avoiding redundant computations that would increase complexity.
Solution Approach 2:
The decoder uses its own internal structure and previously computed information to generate soft outputs for code bits. The backward pass leverages the existing polar code transformation structure and the already-computed information bit estimates, allowing the decoder to serve its own need for soft outputs without requiring external assistance or significantly increasing complexity.
3Ease of manufacture
If existing polar code decoders are used, then implementation is simple, but soft information for code bits is not available for other modules
Solution Approach 1:
The enhanced decoder maintains the universal SC decoding functionality for obtaining information bits while adding the multi-functionality of soft output generation for code bits. The backward propagation mechanism allows the same decoder structure to serve multiple purposes: standard SC decoding for information recovery and soft information generation for code bits to support SIC receivers and iterative demodulation, without compromising implementation simplicity.
Data Source
AI summary
According to certain embodiments, a method is provided for generating soft information for code bits of polar codes. The method includes receiving, by a decoder of a receiver, soft information associated with coded bits from a first module of the receiver and using a tree structure of the polar code to generate updated soft information. The updated soft information is output by the decoder for use by a second module of the receiver.