MsgB Retransmission Monitoring in Two-Step Random Access
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Solution Overview
Problem
Existing wireless communication systems face challenges in improving the performance of the random access procedure for user equipment devices, particularly in scenarios where the downlink message transmission fails, leading to inefficient retransmission processes.
Innovation Solution
The proposed solution involves monitoring for one or more retransmissions of the downlink message, using a Radio Network Temporary Identity (RNTI) based on location parameters, and adjusting the retransmission window duration to enhance the likelihood of successful decoding, including the possibility of using a different RNTI for retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE device transmits another preamble upon failing to receive the RAR message, then the random access procedure can be restarted, but the access delay and number of retransmissions increase
Solution Approach 1:
The patent applies preliminary action by having the UE device monitor for retransmissions of the downlink message before giving up on the random access procedure. The UE device is configured with a window duration that allows it to monitor for multiple retransmissions (N retransmissions) of the MsgB downlink message. This preliminary monitoring action prevents premature restart of the random access procedure, thereby reducing access delay while maintaining reliability.
2Reliability
If the UE device monitors for multiple retransmissions of the downlink message, then the reliability of random access is improved, but the complexity of the monitoring process increases
Solution Approach 1:
The patent applies dynamics by making the monitoring window duration configurable and adaptable. The network can configure the UE device with different window durations depending on the expected number of retransmissions. The monitoring window is dynamically adjusted based on the parameter N (number of expected retransmissions), allowing the system to balance between reliability improvement and complexity management. This dynamic configuration enables the UE device to monitor for multiple retransmissions without requiring complex fixed monitoring logic.
3Measurement precision
If the RNTI is recalculated for each retransmission attempt, then the accuracy of message identification is improved, but the processing overhead increases
Solution Approach 1:
The patent applies preliminary action by calculating the RNTI once based on the location parameters of the physical resource where the preamble was initially received. This pre-calculated RNTI is then reused for monitoring all subsequent retransmissions of the downlink message within the configured window. This preliminary calculation approach maintains message identification accuracy while avoiding the energy consumption and processing overhead of recalculating the RNTI for each retransmission attempt.
Data Source
AI summary
A wireless user equipment (UE) device may transmit a random access preamble to a base station, using a physical resource on an uplink signal. After failing to receive an initial transmission of a response message from the base station (BS), the UE device may monitor for one or more retransmissions of the response message. Each of the retransmission may include a corresponding transmission number. As an alternative, each of the retransmissions may be at least partially scrambled using a corresponding Radio Network Temporary Identifier (RNTI). As another alternative, a window for monitoring and RNTI calculation may be extended to include the one or more retransmissions. The successive retransmissions may include the same set of UE-specific payloads, or, a decreasing set of payloads over time as UE devices acknowledge successful receipt of their respective payloads.