HARQ Feedback Channel Design for Carrier Aggregation
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Solution Overview
Problem
The existing HARQ feedback channel design in LTE systems is inadequate for carrier aggregation, leading to inefficient resource utilization and format mismatch between user equipment (UE) and eNB due to asymmetric UL and DL carrier configurations, resulting in unreliable decoding and increased computation complexity.
Innovation Solution
A method is proposed that includes predefined rules for HARQ format switching based on UE capability and CC configuration, and an efficient resource allocation scheme using explicit and hybrid methods to determine physical resources for HARQ ACK/NACK, reducing the risk of format mismatch and improving resource utilization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier aggregation with asymmetric UL and DL component carriers is configured, then system throughput is improved, but uplink HARQ feedback payload size increases significantly
Solution Approach 1:
The patent segments the HARQ feedback information into multiple parts transmitted through different channels. Specifically, it divides feedback for different component carriers into separate PUCCH resources, allowing the total payload to be distributed across multiple transmission instances rather than requiring a single large payload transmission.
Solution Approach 2:
The patent introduces a new dimension for feedback transmission by utilizing multiple PUCCH resources across different time slots and frequency resources. Instead of increasing payload size in a single dimension, the feedback is spread across multiple dimensional resources (time, frequency, spatial), effectively managing the large payload requirement.
2Adaptability or versatility
If multiple PUCCH channel formats are supported for different CA configurations, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic PUCCH format selection where the terminal device adapts its feedback transmission format based on the configured carrier aggregation scenario. The system dynamically chooses between different PUCCH formats (e.g., format 1, 2, 3, 4) depending on the number of component carriers and their configurations, allowing flexible adaptation without requiring all formats to be simultaneously active.
Solution Approach 2:
The patent changes key parameters such as the number of PUCCH resources, resource block allocation, and modulation scheme based on the carrier aggregation configuration. By adjusting these parameters dynamically according to the specific CA scenario, the system achieves high adaptability while maintaining a unified underlying framework that reduces overall complexity.
3Productivity
If implicit resource allocation is used for non-CA HARQ feedback, then resource utilization efficiency is improved, but resource allocation becomes inefficient for CA scenarios
Solution Approach 1:
The patent creates a universal resource allocation framework that can handle both non-CA and CA scenarios. The same PUCCH resource allocation mechanisms work for single-carrier and multi-carrier configurations, with the system automatically adapting the number and configuration of resources based on whether CA is enabled and how many component carriers are configured.
Solution Approach 2:
The patent performs preliminary configuration of PUCCH resources during RRC connection setup and carrier aggregation configuration phases. The network pre-allocates and configures the necessary PUCCH resources for potential CA scenarios, so when CA is activated, the resources are already in place and ready for use, eliminating the need for complex real-time allocation decisions.
4Reliability
If HARQ format synchronization between UE and eNB is implemented, then reliability is improved, but communication overhead increases
Solution Approach 1:
The patent implements feedback mechanisms where the terminal device reports its PUCCH format capabilities and selected format back to the network. The eNB uses this feedback to confirm and adjust the configuration, ensuring both sides are synchronized on the correct HARQ feedback format to use, thereby maintaining reliability through active confirmation rather than passive assumption.
Data Source
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AI summary
HARQ feedback channel design for carrier aggregation (CA) is proposed in a multi-carrier LTE/LTE-A system. In one novel aspect, a predefined rule for HARQ feedback channel format switching is adopted by the system. Different HARQ formats are supported: single component carrier (non-CA) mode, carrier aggregation with small payload size (CA-S) mode, carrier aggregation with large payload size (CA-L) mode, and fallback mode. From the various CA and non-CA formats, the format to be used for uplink HARQ feedback channel is determined based on: UE capability for the maximum number of CCs supported; CC configuration information by RRC layer; and detection results of downlink schedulers. The CC configuration information may include the number of CCs that are configured and a specific HARQ format to be used. Because more reliable upper layer configuration is used to make the HARQ format- switching decision, the risk of UE and eNB mismatch is greatly reduced.