Base Station Grant Recovery for Msg3 Failure in Random Access
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wireless communication systems face challenges in recovering from failures during the random access (RA) procedure, particularly when a base station fails to decode the Msg3 message from user equipment (UE), leading to increased power consumption and resource inefficiency at the UE due to repeated blind decoding and contention-based RA procedures.
Innovation Solution
The base station transmits a grant to the UE to retransmit Msg3 on the same or different frequency resources, with optional adjustments to transmit power and modulation and coding scheme (MCS), allowing the UE to retransmit Msg3 based on the grant, thereby facilitating successful decoding without excessive power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station fails to decode Msg3 during RA procedure, then the RA procedure cannot be completed successfully, but the UE continues to perform blind decoding and retransmission attempts which increases power consumption
Solution Approach 1:
The base station provides explicit feedback to the UE through a grant message indicating whether Msg3 was successfully decoded. This feedback mechanism allows the UE to stop blind decoding attempts when the message is successfully received, thereby reducing power consumption while ensuring reliable RA procedure completion.
Solution Approach 2:
The system enables the UE to autonomously determine when to stop retransmission attempts based on receiving an acknowledgment from the base station. The UE self-manages its power consumption by ceasing blind decoding operations once successful message delivery is confirmed through the grant feedback.
2Reliability
If the UE performs repeated blind decoding and contention-based RA procedures to recover Msg3, then message delivery may eventually succeed, but resource utilization efficiency decreases
Solution Approach 1:
The base station sends a grant message as explicit feedback to confirm successful Msg3 decoding. This feedback eliminates the need for repeated blind decoding and contention-based RA procedures, thereby improving resource utilization efficiency while maintaining message delivery success.
Solution Approach 2:
Instead of allowing the UE to perform multiple excessive retransmission attempts through blind decoding, the system uses a targeted partial action approach where the base station provides selective feedback only when needed, optimizing resource usage while ensuring reliable delivery.
3Measurement precision
If the base station monitors the first resource for Msg3 transmission, then it can detect successful reception, but if decoding fails the UE must continue monitoring and retransmitting which increases time delay
Solution Approach 1:
The base station provides timely feedback through the grant message to indicate whether Msg3 decoding was successful. This feedback mechanism reduces time loss by allowing the UE to immediately stop retransmission attempts upon receiving confirmation, rather than continuing with unnecessary monitoring and retransmission cycles.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. In some examples, a base station may recover a UE from a Msg3 failure during an RA procedure. During the RA procedure, the base station may transmit a RAR message to the UE and in response to the RAR message the UE may transmit an uplink message (e.g., Msg3) to the base station over a first resource indicated in the RAR message. If the base station fails to decode or receive the uplink message over the first resource, the base station may transmit a grant to the UE indicating a second resource for retransmitting the uplink message and the UE may retransmit uplink message to the base station according to the grant.