ACK Feedback Timing During Backhaul Link Subframe Switching
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Solution Overview
Problem
Current LTE systems lack a solution for feeding back UL ACK/NACK information during switching of backhaul link subframe configuration, leading to potential interference and inefficiencies in data transmission.
Innovation Solution
A method and device for feeding back ACK information on an available UL subframe after a specified delay (N ms) following the last transmission, ensuring correct feedback during subframe configuration switching without introducing additional signaling overhead, using a feedback mode compatible with LTE and LTE-A systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay switches from transmitting to receiving within the MBSFN subframe gap, then the backhaul link can receive data from eNB, but the UL ACK/NACK feedback timing relationship (4ms interval) is disrupted
Solution Approach 1:
The patent applies dynamics by making the UL subframe configuration adaptable rather than fixed. When backhaul subframe configuration changes, the UL subframe used for ACK feedback is dynamically selected from available UL subframes after the switching point, rather than being bound to a predetermined 4ms interval. This allows the system to adjust feedback timing based on actual switching conditions.
Solution Approach 2:
The patent changes the timing parameter for ACK feedback from a fixed 4ms interval to a flexible selection based on available UL subframes. Specifically, the feedback is transmitted on the first available UL subframe occurring at least N ms (where N≥4) after the last DL transmission, allowing the timing parameter to adapt to backhaul switching configurations.
2Reliability
If additional signaling overhead is introduced to manage ACK feedback during subframe switching, then feedback reliability improves, but system complexity increases
Solution Approach 1:
The patent applies self-service by enabling the UE to autonomously determine the appropriate UL subframe for ACK feedback without requiring additional network signaling. The UE independently identifies available UL subframes based on the backhaul subframe configuration and selects the first suitable subframe occurring at least N ms after the last DL transmission, eliminating the need for extra feedback timing indicators from the network.
Solution Approach 2:
The patent uses the existing UL subframe structure as an intermediary mechanism to handle feedback timing adjustments. Rather than introducing new signaling protocols, the solution leverages the existing UL subframe availability and timing relationships already present in the LTE/TDD system to implicitly manage feedback scheduling during backhaul switching.
3Stability of the object's composition
If the system maintains strict 4ms ACK feedback interval, then HARQ timing consistency is preserved, but adaptability to backhaul subframe switching is lost
Solution Approach 1:
The patent transforms the static 4ms HARQ timing rule into a dynamic selection process. Instead of enforcing a rigid 4ms interval, the system dynamically selects UL subframes based on when the relay completes its switching from transmit to receive mode. The feedback is sent on the first available UL subframe at least N ms after the last DL transmission, allowing timing to adapt to switching conditions while maintaining the minimum 4ms processing requirement.
Solution Approach 2:
The patent segments the HARQ feedback process into two independent components: the minimum processing time requirement (N≥4 ms) and the actual feedback transmission timing (first available UL subframe). This segmentation allows the processing time constraint to be maintained while the actual transmission timing adapts to backhaul switching configurations, preserving both timing consistency and flexibility.
Data Source
AI summary
The disclosure provides a method and a device for feeding back Acknowledgment (ACK) information during switching of backhaul link subframe configuration, and the method includes during the switching of the backhaul link subframe configuration, if Uplink (UL) ACK/Negative ACK (NACK) information, which corresponds to a last transmission before the switching of one or more Downlink (DL) Hybrid Automatic Repeat Request (HARQ) transmissions, is not fed back on a UL subframe which is before the switching, feeding back the ACK/NACK information on an available UL subframe which is after the switching since Nms after the last transmission, wherein N is an integer. The disclosure achieves the effect of correctly feeding back the ACK information during switching of the backhaul link subframe configuration.