LTE HARQ Buffer Handling During Transmission Mode Changes
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Solution Overview
Problem
Current LTE technologies face issues with data loss and reception failures during transmission mode changes due to the lack of clear procedures for HARQ process reconfiguration, particularly in transitioning between different numbers of transport blocks, leading to ambiguity in buffer handling and potential data transmission failures.
Innovation Solution
The proposed solution involves flushing all downlink HARQ buffers at the UE during transmission mode changes, especially when the number of transport blocks per HARQ process changes, and using DCI format 1A during uncertainty windows to ensure data transmission continuity, along with specific buffer handling procedures to maintain or discard soft bits accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmission mode changes are implemented to support multiple transport blocks, then data transmission capacity is improved, but data loss occurs during the transition due to HARQ buffer handling ambiguity
Solution Approach 1:
The patent applies preliminary action by flushing HARQ buffers before the transmission mode change takes effect. The eNB sends an RRC reconfiguration message that instructs the UE to flush downlink HARQ buffers in advance of the mode transition, ensuring that stale data is cleared before the new mode begins operation, thereby preventing data loss during the transition.
Solution Approach 2:
The patent implements dynamics by making the HARQ buffer handling adaptive to the specific transmission mode transition scenario. The system dynamically determines whether to flush buffers based on the direction of mode change (e.g., from single to dual transport block mode or vice versa), allowing flexible adaptation to different reconfiguration scenarios while maintaining reliability.
2Adaptability or versatility
If RRC reconfiguration is used for transmission mode changes, then mode transition is enabled, but timing ambiguity causes reception failures
Solution Approach 1:
The patent resolves timing ambiguity by implementing preliminary buffer flushing before the new transmission mode becomes active. The RRC reconfiguration message includes an indication to flush HARQ buffers, ensuring that the UE clears its buffers in advance of the mode change, so that when the new mode activates, there is no stale data causing reception failures.
Solution Approach 2:
The system uses feedback mechanisms where the eNB monitors the reconfiguration process and can send additional control messages if needed. The RRC reconfiguration message provides feedback about the timing and requirements of the mode change, allowing the UE to properly synchronize its buffer flushing and mode activation with the eNB's expectations.
3Reliability
If HARQ buffers are flushed during mode change, then data loss is prevented, but transmission continuity is interrupted
Solution Approach 1:
The patent minimizes transmission interruption by performing buffer flushing as a preliminary action that occurs quickly at the UE side upon receiving the RRC reconfiguration message. The flush operation is a simple memory clear operation rather than a lengthy process, allowing the system to maintain short interruption times while still ensuring reliability.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the buffer flushing and mode reconfiguration are coordinated so that data transmission can resume immediately after the transition. The eNB manages the timing of mode changes and can schedule subsequent transmissions to minimize gaps, keeping the overall data flow continuous despite the brief interruption during mode change.
Data Source
AI summary
A method and device for handling hybrid automatic repeat request (‘HARQ’) operations during transmission mode changes, the method detecting a transmission mode change; and manipulating an HARQ process buffer based on the detecting. Further, a method and network element for handling hybrid automatic repeat request (‘HARQ’) operations during transmission mode changes, the method checking when a user equipment is in a transmission mode uncertainty window; and blocking communications to the user equipment or utilizing a downlink control information format 1A for communications to the user equipment.