UE TTI Bundle Retransmission Using HARQ Feedback Logic
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE wireless communication systems, TTI bundling retransmissions often result in improper Hybrid Automatic Repeat Request (HARQ) retransmissions due to non-adaptive retransmission strategies, leading to inefficiencies and potential interference with other user equipment (UE) transmissions.
Innovation Solution
A method and apparatus for handling TTI bundling retransmissions in user equipment (UE) where the first transmission of a TTI bundle is generated based on an uplink grant received on the Physical Downlink Control Channel (PDCCH), and follow-up transmissions are performed in a non-adaptive retransmission manner, with the decision to generate a non-adaptive retransmission determined by the last received HARQ feedback, even if no uplink grant is received.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If non-adaptive retransmissions are performed without checking HARQ feedback, then retransmission speed is improved, but system reliability deteriorates due to improper retransmissions
Solution Approach 1:
The patent applies feedback by checking the last received HARQ feedback (ACK/NACK) before performing non-adaptive retransmissions. The UE determines whether to generate a non-adaptive retransmission based on the feedback status, ensuring that retransmissions only occur when necessary (when NACK was received) rather than blindly retransmitting regardless of feedback status. This resolves the contradiction by maintaining fast non-adaptive retransmission机制 while preventing improper retransmissions that would harm reliability.
2Duration of action of stationary object
If non-adaptive retransmissions are always generated, then transmission continuity is improved, but system efficiency deteriorates due to unnecessary retransmissions
Solution Approach 1:
The patent uses HARQ feedback to conditionally trigger non-adaptive retransmissions. When the last feedback is ACK, no non-adaptive retransmission is generated, avoiding unnecessary transmissions and improving system efficiency. When the last feedback is NACK, non-adaptive retransmission is generated to maintain transmission continuity. This feedback-based conditional approach resolves the contradiction between transmission continuity and system efficiency.
Solution Approach 2:
The patent implements partial action by selectively applying non-adaptive retransmissions only in specific scenarios (when NACK feedback is received) rather than always performing them. This partial application of the retransmission mechanism avoids the excessiveness of always retransmitting, thereby improving system efficiency while maintaining transmission continuity where needed.
3Device complexity
If the number of HARQ processes is reduced from 8 to 4 for TTI bundling, then device complexity is reduced, but adaptability deteriorates due to fewer available processes
Solution Approach 1:
The patent introduces dynamic behavior to the reduced set of 4 HARQ processes by implementing conditional non-adaptive retransmission logic. The system dynamically adjusts retransmission behavior based on HARQ feedback and transmission opportunity context, allowing the limited 4 processes to adaptively handle various scenarios (first transmission within bundle, retransmission opportunities, ACK/NACK states) that would otherwise require more processes. This dynamic adaptation resolves the contradiction between reduced complexity and maintained adaptability.
Data Source
AI summary
A method for handling Transmission Time Interval (TTI) bundle retransmission in a user equipment (UE) of a wireless communication system is disclosed. The UE operates in a TTI bundling mode. The method includes steps of performing a bundle retransmission of a TTI bundle, which is triggered by a Hybrid Automatic Retransmission Request (HARQ) process responsible for the TTI bundle, and determining whether to generate a non-adaptive retransmission for a current transmission opportunity according to a last received feedback of this HARQ process no matter whether the current transmission opportunity is a first transmission opportunity of the bundle retransmission when no uplink grant for the current transmission opportunity has been received on a Physical Downlink Control Channel (PDCCH).