Polar Decoder Frozen Bit Path Pruning for Power Reduction
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Solution Overview
Problem
Existing wireless communication systems face challenges in differentiating when to terminate polar decoding early to conserve power without prematurely abandoning successful decoding processes, especially in noisy channels or incorrect hypothesis scenarios, leading to increased decoding complexity and power consumption.
Innovation Solution
The implementation of frozen bit metrics and frozen bit path metrics allows for the pruning and early termination of decoding paths in polar decoding, enabling the decoder to discard unlikely paths and terminate processes efficiently without additional CRC or parity bits, by comparing these metrics to threshold criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If early termination is implemented to reduce power consumption, then energy efficiency improves, but decoding accuracy may deteriorate due to premature termination of successful decoding processes
Solution Approach 1:
The patent changes the parameter used for decoding evaluation from traditional path metrics at information bit locations to frozen bit metrics at frozen bit locations. This parameter change enables more reliable early termination decisions because frozen bits have predetermined values that provide a stable reference for assessing decoding progress, allowing the system to terminate early with maintained accuracy.
Solution Approach 2:
The patent introduces frozen bit metrics as an intermediary mechanism between the decoding process and the termination decision. These metrics serve as a reliable indicator that mediates between continuing decoding (to ensure accuracy) and terminating early (to save power), resolving the contradiction by providing a trustworthy early stopping criterion.
2Reliability
If traditional path metrics are used for decoding evaluation, then decoding accuracy is maintained, but decoding complexity increases preventing effective early termination
Solution Approach 1:
The patent segments the decoding evaluation into separate metrics for information bit locations and frozen bit locations. By evaluating frozen bit metrics independently, the system can make early termination decisions without needing to complete full path metric calculations for all information bits, thereby reducing complexity while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary evaluation using frozen bit metrics before completing the full decoding process. This preliminary action allows the system to identify unsuccessful decoding attempts early and terminate them, avoiding the computational complexity of completing full path metric calculations for doomed decoding paths.
3Reliability
If decoding continues for all candidate hypotheses, then detection probability is maximized, but power consumption and latency increase
Solution Approach 1:
The patent applies partial action by evaluating only frozen bit metrics rather than complete path metrics for all candidate hypotheses. This partial evaluation is sufficient to identify unsuccessful decoding attempts, allowing the system to terminate early for failed hypotheses while maintaining detection probability for successful ones, thereby reducing power consumption without sacrificing reliability.
Solution Approach 2:
The patent implements periodic evaluation of frozen bit metrics during the decoding process for multiple candidate hypotheses. This periodic checking allows the system to continuously assess decoding progress and terminate hypotheses that are unlikely to succeed, optimizing the balance between detection probability and power consumption across multiple decoding attempts.
4Use of energy by moving object
If frozen bit metrics are used for early termination, then power consumption is reduced, but additional complexity is introduced in metric calculation
Solution Approach 1:
The patent makes the frozen bit metrics serve multiple functions: they evaluate decoding progress, enable early termination decisions, and provide a reliable indicator of decoding success probability. This multi-functionality justifies the additional calculation complexity by demonstrating that the same metrics achieve multiple objectives, including power savings through early termination.
Solution Approach 2:
The frozen bit metrics are calculated as a natural byproduct of the polar decoding process itself, without requiring separate computational resources. The metrics leverage the inherent structure of polar codes and the predetermined frozen bit values, allowing the system to self-evaluate decoding progress using existing decoding computations, thereby minimizing additional complexity.
Data Source
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AI summary
Methods, systems, and devices for wireless communication are described. The examples described herein may enable a successive cancellation decoder to determine path metrics for various decoding paths based on identified frozen bit locations of a polar code. The path metric for a decoding path may be based on bit metrics determined for the identified frozen bit locations along the decoding path. Once the path metrics and bit metrics are determined, the decoder may compare these metrics to threshold criteria and determine whether to discard decoding paths based on the comparison. The techniques described herein for discarding decoding paths may allow the decoder to discard, prune, or disqualify certain decoding paths that are unlikely to provide an accurate representation of bits received from another device. Consequently, the decoder may be able to save power by terminating a decoding process early (i.e.,early termination) if all paths are discarded, pruned, or disqualified.