UE Retransmission Management During BWP Switching
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Solution Overview
Problem
Wireless communication systems face inefficiencies and delays due to unnecessary retransmissions and beam switching in bandwidth part (BWP) transitions, particularly in non-terrestrial networks (NTNs), leading to system latency and degraded user experience.
Innovation Solution
Implementing techniques that allow user equipment (UE) to manage retransmissions by transmitting feedback information on the source BWP before switching to the target BWP, and determining the timing for retransmissions based on BWP switching windows and resource availability, thereby avoiding duplicate transmissions and reducing system latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE transmits feedback information after switching to the target BWP, then the UE uses the updated frequency resources, but the base station may not recognize the feedback due to BWP switching causing loss of feedback information
Solution Approach 1:
The UE transmits feedback information for downlink signals received on the source BWP before completing the BWP switch to the target BWP. This preliminary transmission ensures the base station receives the feedback on the source BWP where it can properly decode and recognize it, preventing feedback loss despite the upcoming BWP transition.
2Reliability
If the UE sends retransmissions after BWP switching, then the UE ensures uplink signal delivery, but unnecessary duplicate retransmissions occur increasing system latency
Solution Approach 1:
The base station monitors the feedback information transmitted by the UE on the source BWP to determine whether retransmission is necessary. By properly receiving and processing this feedback before the BWP switch, the base station can make an informed decision about retransmission needs, avoiding unnecessary duplicate transmissions that would increase latency.
Solution Approach 2:
The determination of retransmission necessity is made before the BWP switching occurs, based on feedback received on the source BWP. This preliminary determination prevents the UE from sending unnecessary retransmissions on the target BWP, thereby reducing system latency while ensuring reliable uplink delivery.
3Adaptability or versatility
If the UE switches beams during BWP transition, then the UE adapts to new frequency resources, but beam switching causes additional delays and complexity
Solution Approach 1:
The UE completes feedback transmission on the source BWP before initiating the beam switch to the target BWP. This sequencing ensures that critical feedback is sent while the original beam is still active, avoiding the need for retransmission after beam switching and thereby reducing the overall time loss associated with beam transitions.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) receives one or more downlink signals using a first beam associated with a first set of frequency resources, switches from the first beam to a second beam associated with a second set of frequency resources, selects a set of frequency resources for transmitting feedback information associated with the one or more downlink signals, and transmits the feedback information to the base station using the selected set of frequency resources. In some examples, the UE transmits one or more uplink signals to a base station using a first beam associated with a first set of frequency resources, switches from the first beam to a second beam associated with a second set of frequency resources, and determines whether to send a retransmission of the one or more uplink signals based at least in part on switching.