Semi-Persistent Scheduling NACK Feedback Compression
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Solution Overview
Problem
In wireless communication systems using semi-persistent scheduling (SPS), the existing NACK-only feedback schemes increase network overhead due to a higher number of NACK transmissions, especially when there are more empty SPS transmission occasions than non-empty ones.
Innovation Solution
The method involves receiving downlink control information (DCI) from a base station indicating a semi-persistent schedule for PDSCH occasions within a transmission window and a quantity of empty PDSCH occasions. The user equipment (UE) then receives downlink data transmissions based on the schedule and transmits feedback messages indicating the number of NACKs associated with empty or non-empty PDSCH occasions only when the total number of NACKs exceeds the initial quantity of empty occasions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If NACK-only feedback schemes are used in semi-persistent scheduling, then feedback transmission simplicity is improved, but network overhead increases due to higher number of NACK transmissions
Solution Approach 1:
The base station performs preliminary action by indicating the quantity of empty PDSCH occasions in the DCI before the transmission window. This allows the UE to know in advance how many NACKs would be generated if all occasions were transmitted, enabling the UE to decide whether to compress feedback based on this预先 information.
Solution Approach 2:
The feedback transmission becomes dynamic rather than static. The UE dynamically decides whether to transmit compressed feedback or individual NACKs based on the actual number of NACKs generated during the transmission window, which depends on the number of empty occasions indicated in the DCI.
2Measurement precision
If all PDSCH occasions are transmitted individually, then feedback accuracy is improved, but network overhead increases due to unnecessary NACK transmissions during low traffic periods
Solution Approach 1:
Multiple individual NACK transmissions are merged into a single compressed feedback message when the number of NACKs exceeds the number of empty occasions. This combining approach reduces the total number of transmissions while maintaining feedback accuracy about which occasions failed.
Solution Approach 2:
The feedback mechanism changes parameters based on conditions. When the number of NACKs exceeds empty occasions, the system switches from transmitting individual NACKs to compressed feedback. The parameter being changed is the feedback transmission format, selected based on the count relationship between NACKs and empty occasions.
3Adaptability or versatility
If dynamic scheduling is used, then resource allocation flexibility is improved, but control channel overhead increases due to frequent grant transmissions
Solution Approach 1:
The patent uses periodic action through semi-persistent scheduling where transmission resources are allocated for multiple occasions without requiring individual dynamic grants for each occasion. The SPS configuration establishes a periodic pattern that reduces the frequency of control channel transmissions compared to fully dynamic scheduling.
Data Source
AI summary
A method for wireless communication by a UE includes receiving, from a base station, DCI indicating both a semi-persistent schedule for PDSCH occasions within a transmission window and a first quantity of a first group of empty PDSCH occasions. The PDSCH occasions may include the first group of empty PDSCH occasions and a second group of non-empty PDSCH occasions. The method also includes receiving, from the base station, downlink data transmissions within the transmission window based on the semi-persistent schedule. The method further includes transmitting, to the base station, a feedback message indicating a second quantity of either a first group of NACKs associated with the first group of empty PDSCH occasions or a second group of NACKs associated with the second group of non-empty PDSCH occasions based on a total quantity of both the first group of NACKs and the second group of NACKs being greater than the first quantity.