HARQ ACK/NACK Bit Management in TDD-FDD Carrier Aggregation
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Solution Overview
Problem
In next-generation mobile communication systems, the combination of FDD-based and TDD-based cells in carrier aggregation technology poses challenges for HARQ (Hybrid Automatic Repeat Request) operations, particularly in efficiently managing HARQ ACK/NACK bits within the limited capacity of PUCCH formats.
Innovation Solution
A method is introduced where a user equipment (UE) configures carrier aggregation with a TDD-based primary cell and FDD-based secondary cells, limiting the maximum number of cells to ensure that HARQ ACK/NACK bits do not exceed the maximum allowed in the PUCCH format, and utilizing specific UL-DL configurations to optimize HARQ timing and bit transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If both TDD-based cell and FDD-based cell are included in carrier aggregation, then frequency utilization and data communication speed are improved, but HARQ operation complexity increases and PUCCH bit capacity is exceeded
Solution Approach 1:
The patent segments the carrier aggregation configuration by designating one cell as primary cell (PCell) and others as secondary cells (SCell). This segmentation allows differentiated HARQ operation modes: the PCell uses conventional HARQ timing while SCells follow PCell's timing, simplifying the overall HARQ management in multi-cell CA scenarios
Solution Approach 2:
The patent introduces dynamic adjustment of HARQ timing based on the PCell's UL-DL configuration. The HARQ timing for SCells is dynamically aligned with the PCell's timing structure, allowing the system to adapt to different TDD configurations while maintaining consistent HARQ operation across aggregated cells
2Adaptability or versatility
If maximum number of cells in carrier aggregation is increased, then frequency utilization is improved, but the number of HARQ ACK/NACK bits exceeds PUCCH format capacity
Solution Approach 1:
The patent merges the HARQ timing structures of multiple cells by aligning all SCell HARQ timings with the PCell's timing. This merging approach consolidates the HARQ feedback mechanism, allowing efficient bit management in PUCCH even when multiple cells are aggregated, as the timing alignment reduces the total number of independent HARQ processes
Data Source
AI summary
One disclosure of the present specification provides a method for operating a HARQ from user equipment (UE). The method comprises the steps of: the UE receiving downlink data from each cell, when at least one TDD-based cell and at least one FDD based cell are established according to carrier aggregation (CA), a specific TDD-based cell is established as a primary cell of the carrier aggregation (CA), and the at least one FDD-based cell is established as a secondary cell of the carrier aggregation (CA); the UE confirming a PUCCH format to be used for transmitting a HARQ ACK/NACK for the downlink data; and the UE determining the number of bits for transmitting the HARQ ACK/NACK when use of the specific PUCCH format for transmitting the HARQ ACK/NACK is confirmed.