HARQ-ACK Feedback Using PUCCH Format 3 for TDD Carrier Aggregation
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Solution Overview
Problem
In LTE systems with carrier aggregation, existing HARQ feedback mechanisms struggle with interband Time Division Duplex (TDD) configurations that have different Uplink/Downlink configurations on different bands, leading to inefficiencies and increased complexity in Rel-11 scenarios.
Innovation Solution
A method and system for generating HARQ-ACK feedback using PUCCH format 3, where the number of HARQ feedback bits is determined by the minimum value between the Downlink Assignment Index (DAI) and the association set size for each serving cell, allowing reuse of PUCCH format 3 for Rel-11 TDD CA configurations with differing UL/DL configurations, without substantial increases in complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing HARQ feedback mechanisms are used for interband TDD CA configurations with different UL/DL configurations, then backward compatibility with Rel-8 is maintained, but feedback reliability and efficiency deteriorate in Rel-11 scenarios
Solution Approach 1:
The patent applies dynamics by making the HARQ feedback mechanism adaptive to different UL/DL configurations through dynamic determination of the number of HARQ feedback bits. The system dynamically adjusts the feedback structure based on the minimum value between DAI and association set size for each serving cell, enabling the same PUCCH format 3 to accommodate varying configuration requirements without sacrificing reliability
Solution Approach 2:
The patent changes the parameter of HARQ feedback bit determination from fixed to variable. By using the minimum value between DAI (Downlink Assignment Index) and association set size as the determining factor, the system adapts the feedback structure to match the actual downlink transmission requirements, enabling reliable feedback across different UL/DL configurations
2Adaptability or versatility
If new HARQ feedback mechanisms are developed for Rel-11 TDD CA configurations, then adaptability to different UL/DL configurations improves, but implementation complexity increases substantially
Solution Approach 1:
The patent applies universality by enabling PUCCH format 3 to serve multiple functions across different Rel-11 TDD CA configurations. The same PUCCH format 3 structure is reused with adaptive bit determination, eliminating the need for configuration-specific feedback formats and reducing implementation complexity while maintaining broad adaptability
Solution Approach 2:
The patent segments the HARQ feedback determination process into cell-specific components. Each serving cell's feedback bit count is independently determined based on its own DAI and association set size, allowing the overall feedback structure to adapt to heterogeneous UL/DL configurations without requiring a completely new unified mechanism
3Reliability
If the number of HARQ feedback bits is determined by association set size only, then feedback completeness is ensured, but feedback efficiency decreases when DAI indicates fewer scheduled subframes
Solution Approach 1:
The patent applies partial action by transmitting only the necessary number of HARQ feedback bits rather than always transmitting for the full association set size. When DAI indicates fewer scheduled subframes, the system transmits feedback only for those scheduled subframes, avoiding unnecessary transmissions and improving efficiency while maintaining completeness for actually scheduled data
Data Source
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AI summary
In one aspect, the teachings herein provide a system and method for reusing the PUCCH format 3 to address the new HARQ-ACK feedback cases encountered in Rel-11, where different UL/DL configurations are involved in the CA configuration of a UE, such as Rel-11 interband TDD CA with different UL/DL configurations on different bands. The various embodiments illustrated by way of example in this disclosure enable reliable and efficient HARQ-ACK feedback for Rel-11 TDD CA without a substantial increase in specification and implementation complexity.