SPS PDSCH Cancelation After NACK on Shared HARQ ID
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Solution Overview
Problem
In wireless communication systems, when a semi-persistent scheduling (SPS) physical downlink shared channel (PDSCH) transmission fails and is followed by another SPS PDSCH with the same hybrid automatic repeat request (HARQ) identifier (ID), the user equipment (UE) flushes the HARQ buffer, preventing successful combination with retransmissions, and network resources are wasted on unmonitored transmissions.
Innovation Solution
The UE refrains from monitoring SPS PDSCH transmissions with the same HARQ ID after sending a negative acknowledgment (NACK) and implements a timer to avoid flushing the HARQ buffer, while the network cancels scheduled SPS PDSCH transmissions with the same HARQ ID after receiving a NACK, indicating dynamic grant (DG) PDSCH transmissions to manage resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE monitors SPS PDSCH transmissions with the same HARQ ID after sending a NACK, then the network can maintain scheduled transmissions, but the UE flushes the HARQ buffer preventing successful combination with retransmissions
Solution Approach 1:
The UE performs preliminary action by sending a NACK for the first PDSCH transmission, which triggers the network to cancel subsequent SPS PDSCH transmissions with the same HARQ ID. This preliminary NACK transmission prevents the harmful buffer flushing action before it occurs, allowing the UE to maintain the HARQ buffer for potential retransmission combination.
Solution Approach 2:
The system implements feedback through the NACK transmission from the UE to the network. This feedback mechanism allows the UE to inform the network about the unsuccessful reception of the first PDSCH transmission, enabling the network to adjust its scheduling decisions and cancel subsequent SPS transmissions that would otherwise cause buffer flushing.
2Productivity
If the network transmits SPS PDSCH transmissions with the same HARQ ID after a NACK, then network resources are utilized, but the transmissions are not successfully received and combine with flushed buffer
Solution Approach 1:
The network performs preliminary anti-action by canceling subsequent SPS PDSCH transmissions with the same HARQ ID after receiving a NACK. This cancelation prevents the harmful effect of transmitting data that would be discarded due to buffer flushing, thereby avoiding waste of network resources on unsuccessful transmissions.
3Reliability
If the UE continuously monitors SPS PDSCH transmissions, then no transmission is missed, but power consumption increases due to monitoring unsuccessful transmissions
Solution Approach 1:
The UE sends a preliminary NACK to inform the network of unsuccessful reception, which enables subsequent cancelation of redundant SPS transmissions. This preliminary action allows the UE to potentially stop monitoring for those canceled transmissions, reducing power consumption while maintaining reliability for actual transmissions.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Various aspects generally relate to cancelation of semi-persistent scheduling (SPS) physical downlink shared channel (PDSCH) transmissions, and more particularly to cancelation of an SPS PDSCH transmission that follows an unsuccessfully received PDSCH transmission that has the same hybrid automatic repeat request (HARQ) identifier (ID) as the SPS PDSCH. In some aspects, a user equipment (UE) may refrain from monitoring for a scheduled SPS PDSCH transmission that has a same HARQ ID as a PDSCH transmission for which the UE transmitted a negative acknowledgment (NACK). In some aspects, a network entity may cancel (for example, may not transmit) a scheduled SPS PDSCH transmission that has a same HARQ ID as a PDSCH transmission for which the network entity received a NACK. The NACKed PDSCH transmission may be a DG PDSCH transmission or a prior SPS PDSCH transmission.