HARQ-ACK Feedback Mapping for Carrier Scheduling Efficiency
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Solution Overview
Problem
The existing HARQ-ACK feedback mechanism in LTE systems is inefficient when dealing with a large number of carriers, particularly in unlicensed frequency bands, leading to increased nonsense HARQ-ACK bits and reduced downlink peak rate due to inaccurate reflection of scheduled downlink carriers and unpredictable transmission timing.
Innovation Solution
A method for feeding back HARQ-ACK information that involves determining a mapping value for each downlink assignment index (DAI) based on the starting position of downlink HARQ transmission within a time-frequency bundling window, allowing for accurate reflection of scheduled carriers and improved feedback efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the maximum number of carriers supported by the UE is increased to handle more downlink carriers, then the downlink capacity and data transmission rate are improved, but the number of invalid HARQ-ACK bits increases and system performance deteriorates
Solution Approach 1:
The patent extracts and removes invalid HARQ-ACK bits from the feedback sequence. By identifying carriers that did not actually transmit downlink data and excluding their corresponding HARQ-ACK bits from the feedback, the system eliminates waste while maintaining support for a large number of carriers. This resolves the contradiction by keeping the carrier quantity high while improving reliability through removal of harmful elements.
Solution Approach 2:
The patent changes the parameter of HARQ-ACK bit sequence length dynamically based on the actual number of scheduled carriers. Instead of using a fixed sequence length based on maximum configured carriers, the system adjusts the feedback bit count to match actual downlink transmissions. This parameter change ensures that as carrier quantity increases, the feedback efficiency is maintained by proportionally adjusting the relevant feedback size.
2Ease of operation
If HARQ-ACK feedback is transmitted according to semi-statically configured timing, then the feedback mechanism is simple and easy to operate, but the feedback timing becomes inaccurate and unpredictable when carriers are dynamically added or removed
Solution Approach 1:
The patent introduces dynamic adjustment to the semi-static HARQ-ACK timing mechanism. The system maintains the overall semi-static framework for ease of operation but adds dynamic elements that allow timing to be adjusted based on actual carrier scheduling. This enables the feedback timing to adapt when carriers are dynamically added or removed, resolving the contradiction between operational simplicity and timing precision.
Solution Approach 2:
The patent implements a feedback mechanism where the UE reports actual carrier scheduling information to the network, and the network adjusts HARQ-ACK timing based on this feedback. This closed-loop feedback allows the system to maintain simple semi-static configuration while achieving accurate timing through continuous adaptation based on actual scheduling conditions.
3Reliability
If all configured carriers are included in HARQ-ACK feedback regardless of actual downlink transmission, then the feedback mechanism is complete and reliable, but the feedback efficiency decreases and downlink peak rate is reduced
Solution Approach 1:
The patent extracts and removes HARQ-ACK bits corresponding to carriers that did not actually transmit downlink data. By identifying and excluding these invalid bits from the feedback sequence, the system maintains feedback completeness for actually transmitted carriers while removing waste, thereby improving feedback efficiency and downlink peak rate without sacrificing reliability.
Solution Approach 2:
Instead of providing complete feedback for all configured carriers (excessive action), the patent applies partial action by providing feedback only for carriers that actually transmitted downlink data. This partial feedback approach eliminates waste while maintaining necessary reliability, resolving the contradiction between completeness and efficiency.
Data Source
AI summary
The present disclosure provides a method for feeding back hybrid automatic repeat request-acknowledgement (HARQ-ACK) information. In the method provided by the present disclosure, an evolved Node B (eNB) transmits Downlink Assignment (DL-GRANT) within a time-frequency bundling window, which corresponds to an uplink subframe feeding back HARQ-ACK. A UE receives DL-GRANT scheduling downlink HARQ transmission in the time-frequency bundling window corresponding to respective uplink subframe for feeding back HARQ-ACK in turn, obtains a DL DAI in the DL-GRANT, and determines a mapping value of each DL DAI; then, maps HARQ-ACK bits of the time-frequency bundling window corresponding to respective uplink subframe for feeding back the HARQ-ACK to corresponding bits of a feedback bit sequence according to the mapping value of the DL DAI; and transmits the HARQ-ACK on an available uplink carrier. The present disclosure also provides a method for feeding back HARQ-ACK information. The UE transmits HARQ-ACK on an indicated carrier according to indication information of a base station. According to the method and apparatus provided by the present disclosure, efficiency for feeding back the HARQ-ACK can be increased and downlink peak rate of the UE can be ensured.