Flexible TTI Bundling and HARQ Timing in LTE TDD Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LTE TDD systems face challenges in UL coverage enhancement and transmission performance due to limited TTI bundling support in certain configurations and HARQ timing mismatches during dynamic configuration switching.
Innovation Solution
Implementing a flexible TTI bundling operation that allows bundling of UL sub-frames even in configurations with less than 4 UL sub-frames, and synchronizing HARQ timing for ACK/NACK messages based on a reference configuration or a fixed sub-frame, to maintain consistent transmission performance across configuration changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic TDD configuration switching is implemented to adapt to traffic conditions, then traffic adaptation performance is improved, but HARQ timing mismatches occur causing transmission performance degradation
Solution Approach 1:
The patent implements dynamic TDD configuration switching that allows the system to adapt UL/DL allocation based on instantaneous traffic conditions. The configuration can change from semi-static to dynamic allocation, enabling the system to respond to varying traffic demands while maintaining reliable HARQ operations through proper timing alignment mechanisms.
Solution Approach 2:
The patent changes the HARQ timing parameter alignment strategy by introducing a reference configuration concept. Instead of using configuration-specific timing, the system aligns HARQ timing across different TDD configurations to a common reference, preventing timing mismatches during configuration switching while maintaining adaptability.
2Device complexity
If TTI bundling is restricted to configurations with at least 4 UL sub-frames, then HARQ timing is simplified, but UL coverage enhancement is limited in configurations with fewer UL sub-frames
Solution Approach 1:
The patent makes TTI bundling universally applicable across all TDD configurations, not just those with at least 4 UL sub-frames. By allowing flexible bundling of any number of contiguous UL sub-frames (1 or more), the system achieves UL coverage enhancement in all configurations while maintaining manageable HARQ timing through reference configuration alignment.
Solution Approach 2:
The patent introduces dynamic TTI bundling where the number of bundled sub-frames can be flexibly adjusted based on the specific configuration and coverage requirements. This dynamic approach allows configurations with fewer UL sub-frames to benefit from bundling by bundling all available UL sub-frames, rather than being restricted by a fixed threshold.
3Reliability
If the number of UL sub-frames is increased to support TTI bundling in all configurations, then UL coverage enhancement is improved, but the flexibility of TDD configuration is reduced
Solution Approach 1:
The patent segments the TTI bundling mechanism into configuration-specific implementations. Each TDD configuration can apply TTI bundling independently with the appropriate number of bundled sub-frames based on its UL sub-frame availability, allowing all configurations to benefit from coverage enhancement while maintaining their unique configuration characteristics and flexibility.
Data Source
AI summary
A communication method applicable for a LTE TDD system is disclosed. The communication method includes: if a radio frame has a plurality of UL sub-frames, adopting a flexible TTI bundling operation on at least one of the UL sub-frames in the radio frame; and when the radio frame is changed from a first configuration into a second configuration, the HARQ timing for a eNB to transmit ACK/NACK messages for the bundled UL sub-frames is the same as the HARQ timing for the eNB to transmit ACK/NACK messages for the last sub-frame of the bundled UL sub-frames in the second configuration.