Carrier Aggregation Feedback Control for TDD FDD Uplink Reliability
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Solution Overview
Problem
In carrier aggregation (CA) systems, the use of different duplex modes between multiple cells, such as TDD and FDD, poses challenges for adequate uplink transmission of acknowledgement signals, leading to potential transmission failures due to limited available UL subframes.
Innovation Solution
A user terminal is designed to communicate with both FDD and TDD cells using carrier aggregation, employing a feedback control mechanism that allocates acknowledgement signals in predetermined UL subframes, allowing feedback through either or both cells, ensuring effective uplink transmission regardless of the primary cell configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different duplex modes (TDD+FDD) are employed between multiple cells in carrier aggregation, then system adaptability and bandwidth utilization are improved, but uplink transmission reliability deteriorates due to limited available UL subframes for acknowledgement signals
Solution Approach 1:
The patent introduces a new dimension for resource allocation by allowing PUCCH transmission in both TDD and FDD cells simultaneously. Instead of being constrained to a single cell for acknowledgement feedback, the system now utilizes the spatial dimension of multiple cells with different duplex modes, enabling flexible selection of UL subframes across TDD and FDD cells to ensure reliable feedback transmission.
Solution Approach 2:
The patent implements dynamic selection of PUCCH transmission cells based on the availability of UL subframes. The system can adaptively choose to transmit PUCCH in TDD cells when UL subframes are available, or fall back to FDD cells when TDD UL subframes are not available, providing dynamic adjustment to maintain transmission reliability under varying conditions.
2Device complexity
If acknowledgement signals are multiplexed in a specific primary cell as in conventional CA, then device complexity is reduced, but uplink transmission reliability deteriorates when the primary cell lacks sufficient UL subframes
Solution Approach 1:
The patent makes both TDD and FDD cells capable of serving as PUCCH transmission cells. Instead of designating a single primary cell for all feedback functions, the system enables multiple cells with different duplex modes to universally perform the PUCCH transmission function, ensuring that acknowledgement signals can be transmitted reliably regardless of which cell type is being used.
3Use of energy by moving object
If UL subframes are limited in TDD cells, then frequency resource efficiency is improved, but the quantity of available uplink resources for feedback decreases
Solution Approach 1:
The patent merges the uplink resource pools of both TDD and FDD cells to provide feedback transmission. By combining the limited UL subframes available in TDD cells with the continuous UL availability of FDD cells, the system creates a unified and sufficient resource pool for acknowledgement signal transmission, maintaining frequency efficiency while increasing total available feedback resources.
Data Source
AI summary
The present invention is designed so that uplink transmission is carried out adequately even when CA to apply different duplex modes between multiple cells is executed. A user terminal communicates with an FDD cell and a TDD cell by employing carrier aggregation, and has a receiving section that receives DL signals transmitted from each cell, and a feedback control section that allocates delivery acknowledgement signals in response to the DL signals received, by allocating the delivery acknowledgment signals in a predetermined UL subframe, and, regardless of the cell that is configured as the primary cell, when UL subframes are configured in both the FDD cell and the TDD cell, the feedback control section feeds back the delivery acknowledgement signals by using a UL subframe of one or both of the cells, and, when a UL subframe is configured only in the FDD cell, the feedback control section feeds back the delivery acknowledgement signals by using the UL subframe of the FDD cell.