Joint FDD TDD Carrier Aggregation HARQ-ACK Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing carrier aggregation across Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes, particularly in terms of HARQ scheduling and feedback, due to differences in subframe configurations and limited UL subframes in TDD mode, which restricts data transmission and control information feedback opportunities.
Innovation Solution
A joint FDD/TDD design for carrier aggregation in LTE systems, where mobile devices establish connections with both FDD and TDD base stations, allowing for flexible subframe scheduling and HARQ-ACK feedback timing adjustments based on the operating modes of primary and secondary serving cells, enabling efficient data transmission and control information feedback across different duplex modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TDD mode is used for carrier aggregation, then spectrum utilization is improved, but the number of available uplink subframes is reduced
Solution Approach 1:
The patent segments the HARQ-ACK feedback mechanism by introducing separate feedback mechanisms for FDD and TDD component carriers. FDD SCell HARQ-ACK feedback is transmitted in uplink subframes of the FDD PCell, while TDD SCell HARQ-ACK feedback follows TDD timing relationships. This segmentation allows the system to maintain the spectrum utilization benefits of TDD while preserving adequate uplink feedback opportunities through FDD resources.
Solution Approach 2:
The patent introduces a new dimension to HARQ-ACK feedback by allowing feedback for TDD SCell to be transmitted in both TDD and FDD uplink subframes. This multi-dimensional approach to feedback timing resolves the contradiction by providing multiple pathways for acknowledgment, effectively increasing the functional capacity of uplink subframes without changing their physical quantity.
2Productivity
If joint FDD and TDD carrier aggregation is implemented, then network capacity is increased, but scheduling complexity increases
Solution Approach 1:
The patent applies local quality by allowing different HARQ-ACK scheduling behaviors for different component carriers based on their duplex modes. FDD SCell HARQ-ACK feedback follows FDD timing (n+4 relationship), while TDD SCell HARQ-ACK feedback follows TDD timing relationships. This localized scheduling approach enables joint FDD-TDD carrier aggregation to increase network capacity while managing complexity through mode-specific rules rather than a single complex unified scheduler.
3Productivity
If HARQ-ACK feedback timing is optimized for TDD mode, then feedback efficiency is improved, but compatibility with FDD mode decreases
Solution Approach 1:
The patent implements dynamic HARQ-ACK feedback timing that adapts to the duplex mode of each component carrier. The system dynamically selects between FDD-style timing (n+4 for FDD SCell) and TDD-style timing (based on TDD uplink-downlink configuration for TDD SCell). This dynamic adaptation allows the system to optimize feedback efficiency for each mode while maintaining compatibility across both FDD and TDD operations through a unified framework.
Data Source
AI summary
Embodiments of the invention are directed to a method for operating a mobile device including establishing a connection to a first base station designated as a PCell and establishing a connection to a second base station designated as a SCell. When the mobile device receives PDSCH from a TDD SCell in a subframe n, it transmits a HARQ ACK to an FDD PCell in subframe n+4. When the mobile device receives PDSCH in a downlink subframe from an FDD SCell, it transmits a HARQ ACK corresponding to the PDSCH to a TDD PCell in a selected uplink subframe. The selected uplink subframe may be the first valid uplink subframe following the downlink subframe. For example, where the downlink subframe carrying the PDSCH is subframe n, and the selected uplink subframe is subframe n+k, where k≥4.