Uplink Control Channel Allocation in Carrier Aggregation HetNet
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Solution Overview
Problem
In the LTE-A system, carrier aggregation increases the need for feedback control information transmission, leading to resource constraints when multiple small cells are deployed within a macro cell, as existing methods require increased PUCCH resources on the macro cell, which can be inefficient.
Innovation Solution
A user terminal and radio base station system that allocates transmission acknowledgement signals to both uplink control channel resources of the primary and secondary cells, allowing flexible allocation based on the contents of the acknowledgement signals and control channel format, thereby minimizing the increase in PUCCH resources required on the macro cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control information for multiple downlink CCs is transmitted using a single uplink CC, then uplink single carrier transmission performance is maintained, but PUCCH resources on the macro cell increase in accordance with the number of small cells and downlink CCs
Solution Approach 1:
The patent divides the transmission of feedback control information across multiple uplink component carriers (CCs) corresponding to different cells. Specifically, feedback for downlink CCs of small cells is transmitted on uplink CCs of those small cells, while feedback for the macro cell is transmitted on the macro cell's uplink CC. This segmentation prevents the concentration of all feedback traffic on the macro cell's PUCCH resources.
Solution Approach 2:
The patent introduces a new dimension for feedback transmission by utilizing uplink CCs of small cells as additional transmission paths. Instead of using only the macro cell's uplink CC for all feedback, the system distributes feedback transmission across multiple spatial/frequency dimensions (different uplink CCs), thereby reducing the load on any single PUCCH resource pool.
2Productivity
If carrier aggregation is applied between macro cell and small cell in HetNet, then broadbandization is achieved, but PUCCH resources on the macro cell increase according to the number of small cells
Solution Approach 1:
The patent segments the feedback transmission responsibility among multiple cells. Each small cell's uplink CC is assigned to carry feedback for its corresponding downlink CCs, while the macro cell's uplink CC carries feedback for macro cell downlink CCs. This segmentation allows carrier aggregation to provide broadbandization without concentrating all feedback traffic on the macro cell.
Solution Approach 2:
Each small cell serves itself by using its own uplink CC to transmit feedback for its downlink transmissions. This self-service approach eliminates the need for small cell feedback to consume macro cell PUCCH resources, allowing the macro cell to maintain its PUCCH resource allocation independent of the number of aggregated small cells.
3Device complexity
If feedback control information is transmitted selectively from uplink CC of a single cell, then resource allocation is simplified, but resource efficiency decreases when multiple cells are involved
Solution Approach 1:
The patent segments feedback transmission by cell, with each cell's uplink CC handling feedback for its associated downlink CCs. This segmentation maintains relatively simple resource allocation within each cell while improving overall resource efficiency by distributing feedback traffic across multiple cells rather than concentrating it on a single cell.
Solution Approach 2:
The patent transitions from a single-dimension feedback transmission model (all feedback on one cell's uplink) to a multi-dimensional model where feedback is distributed across multiple uplink CCs of different cells. This dimensional expansion allows the system to maintain simplicity in individual cell resource allocation while achieving high efficiency through distributed transmission.
Data Source
AI summary
In order to control feedback control information in uplink transmission appropriately even when using carrier aggregation in HetNet, the present invention provides a user terminal that is able to communicate with a plurality of radio base stations having overlapping coverage areas by using carrier aggregation, the user terminal comprising: a reception section that receives downlink shared channel signals using component carriers of a primary cell and a secondary cell; a generating section that generates transmission acknowledgement signals in response to the downlink shared channel signals; and an allocating section that allocates the transmission acknowledgement signals to predetermined uplink control channel resources, wherein the allocating section allocates the transmission acknowledgement signals to either or both of uplink control channel resources of the primary cell and uplink control channel resources of the secondary cell in accordance with contents of the transmission acknowledgement signals and/or an uplink control channel format.