HARQ-ACK Timing Alignment in Mixed Duplex Carrier Aggregation
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Solution Overview
Problem
The efficiency of downlink (DL) HARQ-ACK timing is affected when carrier aggregation (CA) is performed with cells operating in different duplex modes, such as time division duplex (TDD) and frequency division duplex (FDD), leading to reduced data transfer rates and operational challenges in wireless communications systems.
Innovation Solution
A method and apparatus for establishing DL HARQ-ACK timing by using HARQ-ACK timing established in the duplex mode of the primary cell (Pcell) for both the Pcell and secondary cell (Scell), even when they operate in different duplex modes, ensuring efficient data transmission by aligning the timing with the switch-point periodicity and UL subframe-specific DL association sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation is performed with cells operating in different duplex modes (TDD and FDD), then network capacity and data transfer rates are improved, but downlink HARQ-ACK timing efficiency deteriorates due to misalignment between different duplex mode timing requirements
Solution Approach 1:
The patent merges the HARQ-ACK timing mechanisms of TDD and FDD cells by introducing a unified timing reference based on TDD uplink-downlink configuration. The base station aligns the HARQ-ACK timing of FDD cells with the TDD cell's uplink subframe structure, creating a coordinated timing framework that resolves the conflict between different duplex mode requirements while maintaining carrier aggregation benefits
Solution Approach 2:
The patent changes the timing parameters of FDD cell HARQ-ACK transmissions by introducing an offset value (k) that shifts the FDD HARQ-ACK timing to align with TDD uplink subframes. This parameter adjustment allows FDD downlink transmissions to have their acknowledgments received in TDD uplink subframes, resolving the timing misalignment issue
2Adaptability or versatility
If separate HARQ-ACK timing is established for each cell in carrier aggregation, then cell-specific optimization is achieved, but system complexity increases due to multiple timing configurations
Solution Approach 1:
The patent creates a universal HARQ-ACK timing framework where the TDD uplink-downlink configuration serves as a reference for both TDD and FDD cells. This multi-functional timing reference allows the system to handle different duplex modes through a single configuration mechanism, reducing complexity while maintaining cell-specific adaptability through offset adjustments
3Reliability
If HARQ-ACK timing is aligned with TDD uplink subframes for FDD cells, then timing efficiency improves, but flexibility in FDD operation is reduced
Solution Approach 1:
The patent introduces dynamic offset adjustment capability where the timing offset (k) for FDD cells can be flexibly configured based on network conditions and requirements. This dynamic parameter allows the system to optimize HARQ-ACK timing efficiency by aligning with TDD uplink subframes when needed, while retaining the ability to adjust or relax the alignment constraint to maintain FDD operational flexibility when required
Data Source
AI summary
Provided area a method for establishing downlink (DL) HARQ-ACK timing, and an apparatus therefor. The method establishes downlink HARQ-ACK timing when a primary cell and a secondary cell having different duplex modes are established for a user equipment. The user equipment receives a DL signal on the secondary cell. The user equipment applies HARQ-ACK timing established to be used in the duplex mode of the primary cell as HARQ-ACK timing regarding the received downlink signal.