HARQ Timing Management in Dynamic TDD LTE Systems
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Solution Overview
Problem
Current LTE technology faces challenges in efficiently managing HARQ-ACK reporting and UL grant adjustments in TDD interband CA, leading to interference and complexity in DL and UL HARQ timing management, especially with dynamic subframe configuration changes.
Innovation Solution
The solution involves defining reference subframe configurations for both DL and UL HARQ operations, allowing for simplified management of HARQ timing by fixing certain subframes and using a cell-specific UL index configuration to avoid collisions between UL index and UL DAI bits in DCI format 0/4, and employing flexible UL grant timing to resolve issues with UL DAI bit ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic subframe configuration changes are implemented for eIMTA in TDD LTE, then network flexibility and traffic adaptation capability are improved, but HARQ timing management complexity and interference increase
Solution Approach 1:
The patent segments the HARQ timing management by introducing separate reference subframe configurations for downlink (DL) and uplink (UL) HARQ operations. This segmentation allows independent management of DL and UL timing relationships, simplifying the overall complexity while maintaining dynamic subframe configuration capability for eIMTA.
Solution Approach 2:
The patent establishes reference subframe configurations in advance before dynamic subframe changes occur. These reference configurations serve as pre-defined timing templates that remain stable even when actual subframe assignments change dynamically, thereby simplifying HARQ timing management while enabling traffic adaptation.
2Adaptability or versatility
If UL index and UL DAI bits are used in DCI format 0/4 for dynamic TDD configuration, then scheduling flexibility is improved, but bit collision and ambiguity occur
Solution Approach 1:
The patent resolves the bit collision by introducing a new dimension for UL DAI indication through a separate field in DCI format 0/4. Instead of reusing the UL index bits for both purposes, the invention adds an explicit UL DAI field, eliminating ambiguity while preserving scheduling flexibility for dynamic TDD configurations.
3Reliability
If flexible UL grant timing is implemented to resolve DAI ambiguity, then HARQ-ACK transmission accuracy is improved, but control signaling overhead increases
Solution Approach 1:
The patent makes the UL DAI field in DCI format 0/4 serve multiple functions: it simultaneously provides uplink scheduling information and downlink acknowledgment information. This multi-functionality allows accurate HARQ-ACK transmission without requiring separate dedicated fields for each purpose, thereby limiting the increase in control signaling overhead.
Data Source
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AI summary
A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus receives, by a user equipment (UE) during a first subframe, an indication of a dynamic uplink / downlink (UL/DL) subframe configuration. The apparatus determines an uplink hybrid automatic repeat request (HARQ) timing based on an uplink reference subframe configuration and at least one of the dynamic UL/DL subframe configuration or a downlink reference subframe configuration. The apparatus selects an uplink subframe for communication based on the determined uplink HARQ timing.