SPS HARQ-ACK Feedback Timing for TDD Collision Avoidance
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Solution Overview
Problem
Current 3GPP standards face challenges in handling HARQ-ACK feedback for SPS PDSCH in TDD configurations due to collisions with non-uplink symbols, leading to increased latency, resource inefficiency, and power consumption, especially in scenarios with multiple SPS configurations and TSN traffic with non-configurable periodicities.
Innovation Solution
A method for user equipment (UE) and base station to monitor and select actual SPS PDSCHs, construct HARQ-ACK codebooks only for transmitted SPS PDSCHs, and adjust HARQ-ACK feedback timing to avoid collisions, using explicit or implicit signaling to postpone transmissions to available uplink resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If HARQ-ACK feedback is transmitted according to fixed timing K1 for SPS PDSCH, then feedback timing is simple and predictable, but collision with non-uplink symbols occurs in TDD configurations causing HARQ-ACK dropping
Solution Approach 1:
The patent applies dynamics by making the HARQ-ACK feedback timing adjustable rather than fixed. The UE dynamically selects from multiple candidate K1 values based on whether the corresponding uplink slot is available, allowing the system to adapt to TDD configuration constraints while maintaining reliable feedback transmission.
Solution Approach 2:
The patent changes the parameter of feedback timing offset from a single fixed value to multiple candidate values. The UE selects the appropriate K1 value from a configured set based on uplink availability, transforming a rigid timing parameter into a flexible one that can avoid collisions with non-uplink symbols.
2Object-affected harmful factors
If HARQ-ACK is dropped when collision with non-uplink symbols occurs, then uplink resource collision is avoided, but decoding workload increases and pre-configured PDSCH resource is consumed
Solution Approach 1:
The patent applies preliminary action by having the UE determine in advance which SPS PDSCHs have available uplink slots for HARQ-ACK feedback before actually transmitting. The UE identifies and selects only those PDSCHs where the corresponding uplink slot is valid, avoiding unnecessary decoding and transmission of HARQ-ACK for colliding resources.
Solution Approach 2:
The patent extracts only the necessary HARQ-ACK feedback for SPS PDSCHs that have available uplink resources. By filtering out SPS PDSCHs whose feedback timing collides with non-uplink symbols, the system removes unnecessary processing workload and resource consumption while maintaining reliable feedback for valid transmissions.
3Object-affected harmful factors
If HARQ-ACK is dropped for SPS PDSCH, then uplink collision is avoided, but system performance degrades in terms of latency and resource efficiency
Solution Approach 1:
The patent makes the feedback timing dynamic by allowing the UE to select from multiple K1 candidate values. This enables the system to adapt to TDD configuration constraints while maintaining low latency for SPS PDSCHs that can be feedback immediately, thus preserving system performance for valid transmissions.
Solution Approach 2:
The patent applies local quality by treating different SPS PDSCHs differently based on their specific timing characteristics. Each SPS PDSCH is evaluated individually to determine if its feedback timing is valid, allowing optimal handling of each case rather than uniformly dropping all feedback, thereby maintaining resource efficiency where possible.
4Adaptability or versatility
If multiple SPS configurations are used for TSN traffic with non-configurable periodicities, then traffic flexibility is improved, but HARQ-ACK feedback management becomes complex and resource consumption increases
Solution Approach 1:
The patent segments the HARQ-ACK feedback management by processing each SPS configuration independently. The UE determines available uplink slots for each SPS PDSCH separately based on its specific timing, allowing flexible management of multiple configurations without overwhelming complexity.
Solution Approach 2:
The patent applies preliminary action by having the UE pre-determine which SPS configurations have valid uplink feedback opportunities before generating HARQ-ACK feedback. This advance identification simplifies the feedback management process for multiple TSN traffic configurations by filtering out invalid entries upfront.
Data Source
AI summary
A user equipment (UE) executes a hybrid automatic repeat request (HARQ) processing method to reduce HARQ-ACK payload by selecting semi persistent scheduling (SPS) physical downlink shared channels (PDSCHs) on a plurality of periodic SPS PDSCH resources and reporting HARQ-ACKs for the selected SPS PDSCHs. Alternatively, the UE reduces HARQ-ACK payload by reducing HARQ-ACK bits for SPS PDSCH occasions or for SPS PDSCHs. Alternatively, the UE reduces HARQ-ACK payload by skipping HARQ-ACK feedback, such as a HARQ-ACK codebook, for the SPS PDSCHs. The UE determines an adjusted slot or sub-slot location for transmission of a HARQ-ACK bit for an SPS PDSCH at slot or sub-slot n when a symbol in an original slot or sub-slot location for transmission of the HARQ-ACK bit for an SPS PDSCH is invalid or has collision.