HARQ Feedback Mapping for LTE-LAA Carrier Groups
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Solution Overview
Problem
In a Carrier Aggregation (CA) scenario, the reliability of HARQ result feedback through a Physical Uplink Control Channel (PUCCH) is low due to CRC failures and uncertain channel availability in unauthorized spectra when Dual Connectivity (DC) is implemented between LTE and LAA systems, leading to wastage of transmission resources and degraded system performance.
Innovation Solution
A method and device for feeding back HARQ results by determining a mapping relationship between downlink and uplink carrier groups, allowing terminals to transmit HARQ results through target uplink carriers, thereby reducing the need for massive retransmissions and improving feedback reliability, even in cases of CRC failures or LBT failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If HARQ results from multiple downlink component carriers are transmitted through a single PUCCH in Carrier Aggregation, then transmission resource utilization is improved, but feedback reliability deteriorates due to CRC failures and channel availability uncertainty
Solution Approach 1:
The patent divides downlink component carriers into multiple downlink carrier groups and uplink component carriers into multiple uplink carrier groups. Each downlink carrier group is mapped to a corresponding uplink carrier group for HARQ feedback transmission. This segmentation allows HARQ results from different downlink carrier groups to be transmitted through different uplink carriers, reducing the impact of single carrier failures and improving overall feedback reliability while maintaining efficient resource utilization.
2Adaptability or versatility
If Listen Before Talk (LBT) operation is executed before data transmission in LAA system, then coexistence with other systems is improved, but channel availability becomes uncertain leading to transmission failures
Solution Approach 1:
The patent establishes mapping relationships between downlink carrier groups and uplink carrier groups in advance, before actual HARQ feedback transmission. This preliminary configuration enables the terminal to quickly determine the appropriate uplink carrier for feedback transmission without requiring channel sensing at the moment of transmission, thereby reducing the impact of LBT failures while maintaining LAA coexistence requirements.
3Measurement precision
If CRC check is added to PUCCH for improving transmission reliability, then error detection capability is improved, but any CRC failure causes retransmission of all related downlink data leading to resource waste
Solution Approach 1:
By segmenting downlink carriers into multiple groups and mapping each group to separate uplink carriers for HARQ feedback, the patent limits the scope of potential retransmissions. When a CRC failure occurs on one uplink carrier, only the downlink data in the corresponding downlink carrier group needs to be retransmitted, rather than all downlink data across all carriers. This segmentation significantly reduces resource waste from retransmissions while maintaining the error detection benefits of CRC checks.
Data Source
Figure 1A~1B
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Figure 4~5A
AI summary
Provided are a method and device for feeding back a HARQ result. The method includes that: a mapping relationship between each downlink carrier group and each uplink carrier group is determined; a target manner for acquiring a target uplink carrier from the each uplink carrier group is determined; and the mapping relationship and the target manner are sent to the terminal to enable the terminal to feed back a target HARQ result through the target uplink carrier after determining the target uplink carrier in a present uplink carrier group according to the target manner. In the present disclosure, when DC is implemented between a LTE system and a LAA system, if a base station fails in CRC over a certain PDCCH, only downlink data carried on all the downlink carriers in the downlink carrier group corresponding to the uplink carrier group is required to be retransmitted, so that the problem that massive downlink data has to be retransmitted because of a PUCCH CRC failure of the base station can be effectively alleviated, and reliability of a feedback on a HARQ result through a PUCCH in the LAA system can be improved.