User Terminal ACK/NACK Feedback for Mixed Duplex Carrier Aggregation
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Solution Overview
Problem
In carrier aggregation systems, the use of different duplex modes between multiple cells poses challenges for adequate uplink transmission, particularly in scenarios where frequency division duplex (FDD) and time division duplex (TDD) modes are employed together, leading to potential issues with transmission acknowledgment signals and control feedback.
Innovation Solution
The implementation of a user terminal and radio communication method that employs channel selection using specific relationship tables based on the duplex mode of each cell, allowing for flexible PUCCH resource allocation and A/N bundling to ensure reliable uplink transmission across cells with different duplex modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation employs different duplex modes (TDD+FDD) between multiple cells, then system bandwidth and data rates are increased, but uplink transmission reliability deteriorates due to incompatible feedback mechanisms
Solution Approach 1:
The patent changes the parameters of ACK/NACK feedback transmission by introducing separate timing mechanisms for TDD and FDD cells. TDD cells use feedback timing based on uplink-downlink configuration, while FDD cells use fixed timing offsets, allowing each cell type to operate with its optimal timing parameters without conflict
Solution Approach 2:
The patent segments the feedback transmission mechanism by cell type, dividing the carrier aggregation system into TDD cell components and FDD cell components. Each segment handles ACK/NACK feedback independently with its own timing rules, preventing interference between different duplex modes while maintaining overall system functionality
2Device complexity
If conventional feedback mechanism is used in carrier aggregation with different duplex modes, then system complexity is reduced, but transmission acknowledgment signals cannot be transmitted adequately
Solution Approach 1:
The patent applies local quality by configuring feedback timing specifically for each cell type within the carrier aggregation system. TDD cells receive dedicated timing configurations based on their uplink-downlink patterns, while FDD cells receive fixed timing offsets, ensuring each cell type gets the appropriate feedback mechanism for its characteristics
3Device complexity
If PUCCH signals are multiplexed in a specific cell for intra-base station carrier aggregation, then control signaling is consolidated, but uplink transmission adequacy deteriorates when different duplex modes are used
Solution Approach 1:
The patent introduces dynamic timing selection for PUCCH transmission based on the duplex mode of each cell. The system dynamically adjusts feedback timing offsets for FDD cells and uses configuration-based timing for TDD cells, allowing flexible adaptation to different duplex mode combinations while maintaining consolidated PUCCH transmission
Data Source
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AI summary
The present invention is designed so that uplink transmission is carried out adequately even when CA is executed by applying different duplex modes between multiple cells. A user terminal communicates with an FDD cell and a TDD cell by using carrier aggregation, and has a receiving section that receives DL signals transmitted from the cells, and a feedback control section that allocates and feeds back transmission acknowledgment signals in response to each DL signal in an uplink control channel of a predetermined cell, with reference to tables in which at least the states of transmission acknowledgment signals, PUCCH resources and QPSK symbol points are associated with each other, and, in this user terminal, the tables define different contents between the FDD cell and the TDD cell, and regardless of the cell where downlink control information is detected and the cell where downlink shared data is detected, the feedback control section uses the table that corresponds to the duplex mode of the predetermined cell where the transmission acknowledgment signals are transmitted.