HARQ Feedback Mechanisms Using Non-Uniform Sub-Slot Segmentation
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Solution Overview
Problem
Current mechanisms for HARQ feedback in mobile communications, as defined in 3GPP Rel-15, face challenges in meeting the reliability and latency requirements of ultra-reliable low-latency communication (URLLC) traffic, particularly when handling simultaneous mixed service types, leading to restricted opportunities for HARQ codebook transmission and inefficient use of PUCCH resources.
Innovation Solution
The proposed solution involves configuring non-uniform sub-slot sizes for ACK-reporting, allowing dynamic selection between two HARQ codebooks within the same slot, and using separate PUCCH allocations and configurations for each procedure, with dynamic switching using special reserved K1 values, enabling efficient mixing of URLLC and eMBB traffics by supporting finer time distribution and more robust PUCCH formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple HARQ procedures are multiplexed into a common codebook per UL slot, then throughput is improved and intra-UE multiplexing is simplified, but HARQ feedback delay increases and reliability requirements for URLLC traffic are not met
Solution Approach 1:
The patent segments the UL slot into multiple sub-slots, each capable of carrying HARQ-ACK feedback for specific DL transmissions. This segmentation allows different HARQ procedures to be transmitted in different sub-slots rather than being forced into a single common codebook, thereby reducing feedback delay while maintaining multiplexing benefits for throughput.
2Device complexity
If a single common HARQ codebook is used for all DL transmissions, then device complexity is reduced, but the ability to meet different latency and reliability requirements for mixed traffic types is limited
Solution Approach 1:
The patent introduces dynamic HARQ codebook configuration where the UE can be configured with multiple HARQ procedures and the network can dynamically select which procedure to use for different DL transmissions. This dynamic approach allows the system to adapt to different traffic types (URLLC vs eMBB) without requiring complex manual configuration, maintaining versatility while managing complexity through automated network-side selection.
3Reliability
If PUCCH resources are allocated to meet the reliability requirement of the most critical HARQ-ACK information, then reliability is improved, but resource efficiency decreases and spectral efficiency is reduced
Solution Approach 1:
The patent applies local quality by allocating different PUCCH resource characteristics to different HARQ procedures based on their specific reliability requirements. Instead of using uniform high-reliability resources for all HARQ-ACK feedback, the system assigns appropriate resources locally to each procedure, allowing URLLC traffic to use more robust resources when needed while using more efficient resources for less critical eMBB traffic, thereby improving overall spectral efficiency.
4Ease of manufacture
If HARQ codebook transmission opportunities are restricted according to Rel-15 definitions, then implementation simplicity is maintained, but the ability to handle mixed service types with different latency requirements is restricted
Solution Approach 1:
The patent segments the UL slot into multiple sub-slots, each capable of carrying HARQ-ACK feedback for specific DL transmissions. This segmentation allows different HARQ procedures to be transmitted in different sub-slots rather than being forced into a single common codebook, thereby reducing feedback delay while maintaining multiplexing benefits for throughput.
Data Source
AI summary
Various solutions pertaining to mechanisms for feedback of multiple HARQ procedures in a same slot in mobile communications are described. An apparatus receives a plurality of downlink (DL) transmissions from a network node of a wireless network. The apparatus constructs a feedback containing a plurality of hybrid automatic repeat request (HARQ) acknowledgements (HARQ-ACKs) for the plurality of DL transmissions. The apparatus then performs an uplink (UL) transmission of the feedback to the network node in a slot comprising a plurality of sub-slots, with each of the plurality of HARQ-ACKs being in a respective one of the plurality of sub-slots in the slot.