NACK-Based Feedback for Semi-Persistent Scheduling
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Solution Overview
Problem
Current wireless communication systems using semi-persistent scheduling (SPS) face inefficiencies in uplink signaling, particularly due to the potential for base stations to miss negative acknowledgment (NACK) feedback from user equipment (UE), leading to unnecessary retransmissions and increased power consumption.
Innovation Solution
Implementing conditional NACK-based feedback, where the UE transmits a NACK only if the SPS transmission is not successful and refrains from sending an acknowledgment (ACK) if the transmission is successful, based on triggering events such as good uplink channel conditions or retransmissions, to reduce unnecessary signaling and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE transmits both ACK and NACK feedback for SPS transmissions, then the base station can reliably determine transmission success or failure, but the uplink signaling overhead increases and power consumption rises
Solution Approach 1:
The patent extracts only the NACK feedback transmission from the traditional ACK/NACK feedback mechanism. When NACK-based feedback is configured, the UE transmits only NACK for unsuccessful SPS transmissions and omits ACK transmissions for successful transmissions, thereby reducing uplink signaling overhead and power consumption while maintaining reliability through the selective NACK transmission approach
Solution Approach 2:
The patent inverts the traditional feedback approach by transmitting only negative acknowledgments instead of both positive and negative acknowledgments. This inversion transforms the feedback mechanism from an ACK/NACK dual-mode system to a NACK-only system under specific configurations, reducing signaling overhead while preserving essential error detection functionality
2Loss of energy
If the base station assumes successful transmission when no feedback is received, then power consumption is reduced, but unnecessary retransmissions occur when NACK feedback is missed
Solution Approach 1:
The patent applies preliminary action by configuring the NACK-based feedback mechanism in advance through RRC signaling before SPS transmissions occur. This pre-configuration establishes clear rules for feedback transmission, allowing the base station to reliably interpret the absence of NACK as successful transmission, thereby avoiding unnecessary retransmissions while maintaining power efficiency
Solution Approach 2:
The patent implements a refined feedback mechanism where the UE provides NACK feedback only for unsuccessful transmissions. This selective feedback approach, combined with base station configuration, creates a reliable implicit acknowledgment system where the absence of NACK signifies successful reception, resolving the contradiction between power savings and transmission accuracy
3Reliability
If the UE transmits NACK feedback for every unsuccessful SPS transmission, then transmission reliability is improved, but uplink signaling overhead increases
Solution Approach 1:
The patent extracts only the essential error indication (NACK) from the complete feedback mechanism, transmitting it selectively only when transmission failures occur. This extraction approach maintains reliability by ensuring error feedback is always provided while minimizing signaling overhead by eliminating unnecessary ACK transmissions for successful packets
Data Source
AI summary
A user equipment (UE) determines an occurrence of a triggering event for providing negative acknowledgment (NACK) based feedback for a semi-persistent scheduling (SPS) transmission. The apparatus monitors for the SPS transmission. The apparatus transmits a NACK if the SPS transmission is not successfully received and refrains from sending an ACK if the SPS transmission is successfully received based on the occurrence of the triggering event for providing NACK based feedback. The base station determines an occurrence of a triggering event for a UE to provide NACK based feedback for an SPS transmission. The apparatus transmits the SPS transmission and determines that the UE successfully received the SPS transmission based on an absence of a NACK from the UE for the SPS transmission.