Inter-eNB Carrier Aggregation Uplink Control Information Transmission
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Solution Overview
Problem
In wireless networks, particularly in LTE systems with inter-eNB carrier aggregation, the existing methods for providing uplink control information (UCI) between macrocells and smallcells across different eNBs result in increased maximum power reduction, reducing the size of the uplink coverage region due to redundant PUCCH transmissions.
Innovation Solution
The solution involves configuring the PUCCH resource jointly between macrocells and smallcells, allowing for synchronized determination of PUCCH resources, and using techniques like HARQ-ACK forwarding and overhearing to minimize latency and power reduction, while also enabling simultaneous transmission of HARQ-ACK on both macrocell and smallcell PUCCHs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE transmits PUCCH to both macrocell and smallcell simultaneously in inter-eNB CA, then UCI can be delivered to both eNBs, but maximum power reduction increases and uplink coverage region shrinks
Solution Approach 1:
The patent segments UCI transmission into two distinct paths: (1) UE transmits PUCCH to macrocell eNB, and (2) macrocell eNB forwards UCI to smallcell eNB via X2 interface. This segmentation eliminates simultaneous PUCCH transmissions to both eNBs, thereby reducing maximum power reduction while ensuring UCI reaches both macrocell and smallcell through coordinated delivery.
Solution Approach 2:
The macrocell eNB acts as an intermediary between UE and smallcell eNB. It receives PUCCH from UE, extracts UCI, and forwards relevant information to smallcell eNB via X2 interface. This intermediary approach allows indirect UCI delivery to smallcell without requiring direct UE-to-smallcell PUCCH transmission, thus reducing power reduction requirements.
2Loss of energy
If UCI is forwarded through X2 interface between eNBs, then smallcell can receive UCI without direct UE transmission, but latency increases due to additional forwarding step
Solution Approach 1:
The patent applies partial forwarding where only specific UCI information (such as HARQ-ACK) is forwarded via X2 interface, while other UCI (such as CSI) may be handled differently. This selective forwarding approach balances latency and power reduction by minimizing the overhead of X2 interface communication while ensuring critical UCI reaches the smallcell eNB.
3Ease of operation
If PUCCH resources are configured independently at each eNB, then each eNB can manage its own resources, but resource coordination becomes complex and inefficient
Solution Approach 1:
The patent merges PUCCH resource configuration by having the macrocell eNB coordinate resource allocation with the smallcell eNB via X2 interface. The macrocell eNB determines PUCCH resources for UE and communicates this configuration to the smallcell eNB, ensuring both eNBs use consistent resource allocation. This merging approach simplifies resource coordination while maintaining autonomous operation capabilities.
Data Source
AI summary
A user equipment (UE) for communication in a wireless network supporting inter-EUTRAN Node B (eNB) carrier aggregation has a receiver to communicate with a first eNB corresponding to a primary cell (PCell) in the wireless network and a second eNB corresponding to a secondary cell (SCell) in the wireless network. The receiver is configured to receive downlink data through a physical downlink shared channel (PDSCH) in the SCell. The UE has a processor configured to, in response to receiving the downlink data, generate a hybrid automatic repeat request acknowledgement (HARQ-ACK) for the SCell. A transmitter of the UE is configured to transmit, through a first physical uplink control channel (PUCCH) in the PCell, uplink control information (UCI) including the HARQ-ACK for the SCell.