Uplink Feedback Control for Mixed Duplex Carrier Aggregation
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Solution Overview
Problem
In carrier aggregation (CA) systems, the conventional feedback mechanism struggles to adequately transmit delivery acknowledgement signals and channel quality information when different duplex modes (TDD+FDD) are employed between multiple cells, leading to potential limitations in uplink transmission.
Innovation Solution
The proposed solution involves configuring UL subframes in both FDD and TDD cells to allow for simultaneous PUCCH transmission, prioritizing A/N feedback in one cell while allowing CQI and scheduling requests to be transmitted in overlapping timings, and dynamically controlling PUCCH resources to ensure effective use of available UL subframes across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback mechanism is used in carrier aggregation with different duplex modes (TDD+FDD), then system complexity is reduced, but uplink transmission reliability deteriorates due to inadequate delivery acknowledgement signal transmission
Solution Approach 1:
The patent segments the feedback transmission by cell type, with FDD cells handling A/N feedback and TDD cells handling CQI feedback separately. This segmentation allows each cell type to operate with its own optimized feedback timing and resources, resolving the contradiction by maintaining simplicity within each segment while achieving overall reliability through coordinated operation.
Solution Approach 2:
The patent introduces a new dimension of feedback transmission by allowing simultaneous PUCCH transmission in both FDD and TDD cells. This dimensional expansion from sequential to simultaneous transmission enables reliable uplink communication without requiring complex coordination mechanisms, as each cell type operates independently in its own time domain.
2Productivity
If simultaneous PUCCH transmission is configured in both FDD and TDD cells, then uplink transmission capacity is improved, but resource management complexity increases due to overlapping timings
Solution Approach 1:
The patent applies local quality by allowing different transmission characteristics in different cells. FDD cells transmit A/N feedback with specific timing while TDD cells transmit CQI feedback with different timing, even though both can transmit simultaneously. This local differentiation simplifies resource management by allowing each cell to optimize its own transmission parameters independently.
Solution Approach 2:
The patent uses PUCCH (Physical Uplink Control Channel) as an intermediary that can handle multiple types of feedback signals simultaneously. This intermediary capability allows both A/N and CQI feedback to be transmitted at the same time without requiring complex resource management, as the PUCCH structure naturally accommodates different signal types with different timing requirements.
3Reliability
If A/N feedback is prioritized in one cell while allowing CQI and scheduling requests in overlapping timings, then feedback reliability is improved, but transmission scheduling complexity increases
Solution Approach 1:
The patent implements self-service by allowing each cell type to autonomously determine its feedback transmission timing based on its duplex mode characteristics. FDD cells naturally prioritize A/N feedback transmission while TDD cells handle CQI feedback, with each cell type self-managing its own scheduling without requiring complex centralized coordination. This autonomous operation maintains feedback reliability while minimizing scheduling complexity.
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3B
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, a transmission control section that allocates and transmits delivery acknowledgement signals in response to the received DL signals, channel quality information or scheduling requests in predetermined UL subframes, and, when a UL subframe is configured in both the FDD cell and the TDD cell, the transmission control section transmits a delivery acknowledgement signal in one UL subframe or both UL subframes, and controls whether or not to transmit channel quality information or a scheduling request having an overlapping transmission timing with the delivery acknowledgement signal.