Polar-Coded HARQ Switching by Code Rate Threshold
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Solution Overview
Problem
Current wireless communication systems face challenges in achieving reliable data transfer over noisy channels, particularly when bit error rates exceed the correction capabilities of existing error correcting codes, necessitating enhanced retransmission schemes beyond traditional HARQ algorithms.
Innovation Solution
A hybrid automatic repeat request (HARQ) algorithm that selectively employs either incremental redundancy HARQ (HARQ-IR) or chase combining HARQ (HARQ-CC) based on the code rate of the initial polar code transmission, switching between the two methods depending on performance thresholds to optimize error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental redundancy HARQ (HARQ-IR) is used for retransmission, then block error rate performance is improved at higher code rates, but system complexity increases
Solution Approach 1:
The system dynamically selects between HARQ-IR and HARQ-CC based on the code rate of the initial transmission. When the code rate exceeds a threshold, HARQ-IR is selected to provide superior block error rate performance. When the code rate is at or below the threshold, HARQ-CC is selected to maintain lower system complexity. This dynamic adaptation resolves the contradiction by matching the retransmission strategy to the specific operating conditions.
Solution Approach 2:
The invention changes the operating parameter (code rate) to determine the optimal HARQ strategy. By monitoring the code rate parameter and comparing it against a predefined threshold, the system automatically adjusts its retransmission approach. This parameter-based decision-making allows the system to achieve high reliability when needed (high code rates) while avoiding unnecessary complexity when not needed (low code rates).
2Device complexity
If chase combining HARQ (HARQ-CC) is used for retransmission, then system complexity is reduced, but block error rate performance deteriorates at higher code rates
Solution Approach 1:
The system employs dynamic selection between HARQ-CC and HARQ-IR based on real-time code rate conditions. When operating at higher code rates where HARQ-CC performance degrades, the system switches to HARQ-IR to maintain reliability. This dynamic behavior ensures that the system only uses the simpler HARQ-CC when it is actually effective, avoiding performance deterioration while maintaining low complexity when appropriate.
Solution Approach 2:
The invention uses the code rate parameter as a decision criterion for selecting the retransmission strategy. By changing the operational mode based on the code rate parameter value relative to a threshold, the system avoids the performance trap of using HARQ-CC at high code rates while still benefiting from its simplicity at low code rates.
3Device complexity
If a single HARQ algorithm is used for all code rates, then device complexity is reduced, but adaptability to different code rates deteriorates
Solution Approach 1:
The system implements dynamic algorithm selection that adapts to different code rate conditions. Rather than being locked into a single HARQ algorithm, the system automatically switches between HARQ-IR and HARQ-CC based on the code rate of the initial transmission. This dynamic adaptability ensures optimal performance across the full range of code rates while keeping the decision logic simple and threshold-based.
Solution Approach 2:
The invention creates a universal HARQ framework that can handle both high and low code rate scenarios through selective algorithm deployment. The system maintains multiple HARQ capabilities (both HARQ-IR and HARQ-CC) but only activates the appropriate one based on conditions, making the overall system adaptable to diverse operating conditions without requiring complex configuration or manual intervention.
Data Source
AI summary
For communication utilizing polar codes, a hybrid automatic repeat request (HARQ) algorithm is provided that takes advantage of the benefits of chase combining HARQ (HARQ-CC) and incremental redundancy HARQ (HARQ-IR), by selecting one or the other in accordance with a code rate of the first transmission. In some examples, the HARQ algorithm utilizes HARQ-IR when the code rate in the first transmission is greater than a code rate threshold, and utilizes HARQ-CC when the code rate in the first transmission is less than the code rate threshold.