HARQ Feedback Handling in LTE UL/DL Configuration Conflicts
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Solution Overview
Problem
In LTE/LTE-A systems, conflicts arise when advanced UEs change their UL/DL configurations faster than legacy UEs, leading to issues in receiving HARQ feedback due to differences in PHICH groups, causing advanced UEs to miss HARQ feedbacks intended for legacy UEs.
Innovation Solution
A method where the advanced UE determines whether HARQ feedback exists in the PHICH of a subframe based on its own and legacy UE's UL/DL configurations, and if not, detects it through DL control information in the PDCCH, ensuring accurate acknowledgement or retransmission handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If advanced UE changes UL/DL configuration frequently to adapt to varying traffic characteristics, then system adaptability is improved, but HARQ feedback reception reliability deteriorates due to PHICH group conflicts with legacy UE
Solution Approach 1:
The patent applies dynamics by enabling the advanced UE to dynamically switch between different PHICH group configurations based on the detected UL/DL configuration. The UE monitors system information and adjusts its PHICH group selection dynamically to match the current network configuration, allowing frequent UL/DL changes without losing HARQ feedback reliability
Solution Approach 2:
The patent changes the parameter of PHICH group selection based on UL/DL configuration. When the advanced UE detects a UL/DL configuration that differs from its currently configured PHICH groups, it changes the selected PHICH group parameter to match the network's current configuration, resolving the conflict and ensuring reliable HARQ feedback reception
2Reliability
If eNB schedules legacy UE to avoid subframes with different transmission directions, then legacy UE HARQ feedback delivery is improved, but advanced UE HARQ feedback reception deteriorates due to subframe access restrictions
Solution Approach 1:
The patent applies dynamics by enabling the advanced UE to dynamically adjust its PHICH group configuration based on real-time UL/DL configuration detection. This dynamic adaptation allows the advanced UE to access subframes that would otherwise be restricted, maintaining both legacy UE compatibility and advanced UE flexibility without requiring eNB scheduling restrictions
Solution Approach 2:
The patent applies copying by having the advanced UE copy the PHICH group configuration of the legacy UE when conflicts are detected. By adopting the same PHICH group settings as legacy UEs during conflicting subframes, the advanced UE ensures that HARQ feedback can be successfully received without interfering with legacy UE operations
3Reliability
If PHICH groups are increased to support advanced UE with multiple UL/DL configurations, then advanced UE HARQ feedback reception is improved, but PHICH resource allocation complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the PHICH resources into multiple groups that can be selectively activated based on UL/DL configuration. Instead of always allocating resources for all possible configurations, the system segments PHICH groups and activates only the relevant ones for the current configuration, reducing allocation complexity while maintaining support for multiple configurations
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AI summary
A method of handling a hybrid automatic repeat request (HARQ) feedback in a subframe for a first communication device in a wireless communication system comprises determining whether the HARQ feedback exists in a physical HARQ indicator channel (PHICH) in a downlink (DL) control region of the subframe transmitted by a network of the wireless communication system according to a first uplink (UL)/DL configuration of the first communication device and a second UL/DL configuration of a second communication device in the wireless communication system communicating with the network; detecting the HARQ feedback in the PHICH of the subframe, if the HARQ feedback exists in the PHICH; and detecting the HARQ feedback according to DL control information (DCI) in a physical DL control channel (PDCCH) in the DL control region, if the HARQ feedback does not exist in the PHICH.