Polar Decoder Soft-Information Exchange for HARQ Retransmissions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for decoding polar codes over multiple transmissions in HARQ systems are suboptimal due to limited block error performance, as they do not account for information in previous transmissions and exchange hard bits without considering reliability.
Innovation Solution
A method where soft information, such as probabilities or log-likelihood ratios, is exchanged among polar decoders for different transmissions to facilitate iterative decoding, allowing each information bit to benefit from all relevant transmissions rather than just the most recent one.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hard bits are exchanged among polar decoders for different transmissions, then the decoding process is simplified, but the block error performance deteriorates due to loss of reliability information
Solution Approach 1:
The patent transforms the decoding approach by changing the parameter representation from hard bits (0/1) to soft information (log-likelihood ratios). This parameter change allows the system to maintain reliability information while performing iterative decoding across multiple transmissions, resolving the contradiction between simplicity and performance.
Solution Approach 2:
The patent implements a feedback mechanism where soft information from previous transmissions is fed back into the current transmission decoding process. Each polar decoder exchanges soft information with other decoders handling different transmissions, creating an iterative feedback loop that improves block error performance while maintaining manageable complexity.
2Device complexity
If only the most recent transmission is used for decoding, then the decoding complexity is reduced, but the block error rate increases due to loss of information from previous transmissions
Solution Approach 1:
The patent merges information from multiple transmissions by combining soft information from previous transmissions with the current transmission data. The log-likelihood ratios from different transmissions are aggregated, allowing the decoder to leverage all available information while maintaining a unified decoding process that doesn't exponentially increase complexity.
Solution Approach 2:
The patent performs preliminary decoding of previous transmissions to extract soft information before using it in the current transmission decoding. This preliminary action prepares reliability information in advance, which is then integrated into the current decoding process, improving performance without requiring complex joint decoding of all transmissions simultaneously.
3Reliability
If more retransmissions are performed to achieve target block error rate, then the reliability is improved, but the transmission time increases
Solution Approach 1:
The feedback mechanism of soft information exchange enables the system to achieve better block error rates with fewer retransmissions. By continuously refining the reliability information across iterations, the system converges to accurate decoding faster, reducing the total time required compared to systems that must rely on more retransmissions.
Data Source
AI summary
A node receives transmissions associated with a given set of information bits, wherein each of the transmissions use a different polar code and share one or more information bits of the given set of information bits. The node determines, at each of a plurality of polar decoders of the node, soft information for each information bit included in an associated one of the transmissions, wherein each of the plurality of polar decoders is associated with a different transmission of the transmissions. The node provides, from each polar decoder of the plurality to one or more other polar decoders of the plurality, the determined soft information for any information bits shared by their respective associated transmissions, and uses the provided soft information in an iterative decoding process to decode one or more of the received transmissions.