Polar-Coded HARQ Switching by First-Transmission Code Rate
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing bit errors due to varying channel conditions, particularly in future networks beyond LTE, where traditional error correcting codes and HARQ algorithms may not provide optimal performance.
Innovation Solution
A hybrid automatic repeat request (HARQ) algorithm for wireless communication systems utilizing polar codes, which selectively employs either incremental redundancy HARQ (HARQ-IR) or chase combining HARQ (HARQ-CC) based on the code rate of the first transmission, thereby optimizing performance across different code rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If incremental redundancy HARQ (HARQ-IR) is used for retransmission, then error correction performance is improved at higher code rates, but system complexity increases
Solution Approach 1:
The patent changes the HARQ retransmission strategy based on the code rate parameter. When code rate exceeds a threshold, HARQ-IR is selected; when code rate is at or below the threshold, HARQ-CC is selected. This parameter-based adaptation resolves the contradiction by matching the complexity of the retransmission scheme to the actual error correction needs dictated by the code rate.
2Device complexity
If chase combining HARQ (HARQ-CC) is used for retransmission, then system complexity is reduced, but error correction performance deteriorates at higher code rates
Solution Approach 1:
The patent dynamically adjusts the HARQ retransmission approach based on the code rate. At higher code rates where error correction performance is more sensitive, HARQ-IR is employed to maintain reliability. At lower code rates where HARQ-CC suffices, the simpler scheme is used to reduce complexity. This resolves the contradiction by adapting the scheme to the operational context.
3Device complexity
If a fixed HARQ algorithm is used for all code rates, then device complexity is reduced, but overall system performance is suboptimal
Solution Approach 1:
The patent implements a dynamic HARQ algorithm selection mechanism that adapts to the code rate of the first transmission. The system transitions from a static, fixed algorithm approach to a dynamic one where the retransmission strategy changes based on channel conditions and code rate. This resolves the contradiction by allowing the system to optimize performance for each specific operating point without requiring complex algorithms across all scenarios.
4Reliability
If HARQ-IR is used at lower code rates, then performance gains are minimal, but the increased complexity is not justified
Solution Approach 1:
The patent introduces a code rate threshold that determines when to apply HARQ-IR versus HARQ-CC. By monitoring the code rate parameter and comparing it against the threshold, the system avoids applying the more complex HARQ-IR scheme when it would not provide significant performance benefits (at lower code rates), thus resolving the contradiction between complexity and performance.
Data Source
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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.