HARQ Scheme Selection for URLLC Retransmission
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing retransmissions for ultra-reliable and low-latency communications, particularly in determining the appropriate HARQ (Hybrid Automatic Repeat Request) scheme and coding strategies to ensure high reliability and low latency.
Innovation Solution
The system employs a processor to determine the type of HARQ scheme (CC-HARQ, IR-HARQ, or IF-HARQ) based on device capabilities and available resources, and adjusts coding parameters such as mother code length, bit channel reliability, and parity check frozen bits for retransmitting URLLC data and control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Chase Combining (CC-HARQ) is used for retransmission, then implementation complexity is reduced and latency is minimized, but reliability improvement is limited compared to more advanced schemes
Solution Approach 1:
The system dynamically selects between CC-HARQ and IF-HARQ based on real-time channel conditions, device capabilities, and QoS requirements. The processor determines the appropriate HARQ scheme by evaluating current transmission status and available resources, allowing the system to adaptively balance between simplicity and reliability improvement.
Solution Approach 2:
The system changes coding parameters such as mother code length, coding rate, and bit channel mapping based on the selected HARQ scheme. For IF-HARQ, the system increases mother code length and adjusts coding rates to optimize reliability, while for CC-HARQ it maintains simpler parameters for lower complexity operations.
2Reliability
If Incremental Freezing (IF-HARQ) is used for retransmission, then reliability is improved through increased mother code length and lower coding rates, but latency increases due to additional encoding and transmission time
Solution Approach 1:
The system dynamically adapts the HARQ scheme selection based on channel conditions and QoS requirements. When high reliability is critical and latency tolerance exists, IF-HARQ with increased mother code length is applied. When latency is more critical, the system may opt for CC-HARQ or optimized IF-HARQ configurations.
Solution Approach 2:
The system segments the retransmission process by determining whether to transmit only failed data or both failed data and new control information. This segmentation allows optimization of the retransmission content based on what was actually failed, reducing unnecessary transmission time while maintaining reliability for critical data.
3Reliability
If retransmission resources are allocated to increase mother code length and coding rate, then reliability of URLLC data is improved, but spectral efficiency and data rate are reduced
Solution Approach 1:
The system applies different coding strategies to different parts of the transmission. For URLLC data requiring high reliability, the system increases mother code length and uses lower coding rates. For control information or less critical data, the system maintains higher coding rates and better spectral efficiency, creating localized optimization across the transmission.
Solution Approach 2:
The system dynamically adjusts coding parameters based on the selected HARQ scheme and available resources. When IF-HARQ is selected for high reliability, the system allocates more resources to coding overhead. When CC-HARQ is selected or resources are constrained, the system optimizes for data rate and spectral efficiency.
4Reliability
If bit channel mapping prioritizes retransmitted data to more reliable channels, then reliability of retransmitted data is improved, but complexity of code block segmentation and mapping increases
Solution Approach 1:
The system performs preliminary sorting and mapping of bit channels based on reliability before the actual retransmission. The processor pre-determines which bit channels should carry retransmitted data versus new control information based on the selected HARQ scheme and channel conditions, simplifying the actual transmission process while maintaining optimization.
Data Source
AI summary
Systems, methods, and instrumentalities are disclosed for advanced coding on retransmission of data and/control information. The systems methods, and instrumentalities may include one or more of the following: chase combining for retransmission; incremental redundancy (IR) hybrid automatic repeat request (IR-HARQ); or incremental freezing (IF) HARQ. IF-HARQ may use lower coding rates and/or increased mother codeword length. IF-HARQ for retransmission with joint encoding and transmission of failed data and/or control message(s) (e.g., new control message(s)) may be used. This may include one or more of the following: increased priority for retransmission data and mapping retransmitted data to more reliable bit channels; or allocating more PC frozen bits for retransmitted data. A HARQ decision may be provided. For example, a decision may be made between the use of chase combining (CC) HARQ, IR-HARQ, or IF-HARQ. For IF-HARQ, additional decisions may be made.