TDD Secondary Cell DL/UL Configuration for Carrier Aggregation Throughput
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Solution Overview
Problem
Existing mechanisms in LTE and LTE-A systems face challenges in improving throughput when carrier aggregation is employed between cells using different duplex modes, particularly due to the asymmetrical nature of downlink (DL) and uplink (UL) traffic and the limitations of existing DL/UL configurations in TDD systems.
Innovation Solution
A new DL/UL configuration (configuration 7) is introduced for TDD cells to enable DL communication in all subframes, allowing for improved spectral efficiency and flexible traffic management by treating a TDD cell as a secondary cell, and controlling acknowledgement/negative acknowledgement feedback as if it were an FDD cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing DL/UL configurations in TDD are used, then uplink and downlink communication can be maintained with standard configurations, but throughput cannot be improved sufficiently due to fixed subframe allocation ratios
Solution Approach 1:
The patent introduces a new DL/UL configuration (configuration 7) that allows dynamic adaptation of subframe allocation. Specifically, it enables all subframes to be used for downlink communication when needed, transforming the static TDD configuration into a more dynamic system that can adapt to varying traffic conditions, thereby improving throughput while maintaining necessary uplink capabilities through other mechanisms.
Solution Approach 2:
The patent changes the fundamental parameter of subframe allocation by introducing configuration 7, which differs from traditional configurations 0-6. This parameter change allows the system to allocate all subframes for downlink communication in carrier aggregation scenarios, fundamentally altering the DL/UL ratio parameter to optimize throughput for asymmetric traffic patterns.
2Adaptability or versatility
If carrier aggregation employs different duplex modes between multiple CCs, then flexible traffic management can be achieved, but UL-DL interference and synchronization complexity increase
Solution Approach 1:
The patent segments the carrier aggregation system into a primary cell (PCell) and secondary cell (SCell) with different duplex mode configurations. The PCell maintains standard TDD or FDD operation, while the SCell can operate in a specialized mode where all subframes are used for downlink. This segmentation allows flexible traffic management while isolating potential interference issues to specific cell segments.
Solution Approach 2:
The patent introduces an intermediary mechanism where the primary cell acts as a reference for synchronization and uplink/downlink timing, while the secondary cell with configuration 7 focuses on downlink traffic. This intermediary relationship allows the system to achieve flexible traffic management without allowing UL-DL interference to propagate across the entire carrier aggregation system.
3Productivity
If a TDD cell is configured with all downlink subframes, then spectral efficiency for downlink traffic is improved, but uplink communication capability in that cell is lost
Solution Approach 1:
The patent applies multi-functionality by introducing configuration 7 specifically for secondary cells in carrier aggregation scenarios. While this configuration eliminates uplink capability in the secondary cell, the overall system maintains universal communication capability through the primary cell, which retains standard uplink/downlink functionality. This allows the secondary cell to specialize in downlink while the system as a whole maintains full functionality.
Solution Approach 2:
The patent applies local quality by allowing different DL/UL configurations in different cells within the carrier aggregation system. The secondary cell with configuration 7 has specialized local quality optimized for downlink traffic, while the primary cell maintains standard qualities. This local optimization improves overall system performance without requiring all cells to sacrifice uplink capability.
Data Source
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AI summary
The present invention is designed to improve throughput when CA is executed between multiple cells including a TDD cell. A user terminal carries out radio communication with a plurality of cells by employing carrier aggregation, and has a receiving section that, when a connection is established with a TDD cell, receives information about a predetermined DL/UL configuration that is selected from a plurality of DL/UL configurations, and a control section that controls transmission and reception to and from the TDD cell based on the predetermined DL/UL configuration received, and a DL/UL configuration to carry out DL communication in all subframes is included as one in the plurality of DL/UL configurations, and the control section uses the DL/UL configuration to carry out DL communication in all subframes as one of the DL/UL configurations only when the connecting TDD cell is a secondary cell.