Fallback Procedure for 2-Step RACH in Wireless Systems
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Solution Overview
Problem
The existing 2-step random access channel (RACH) procedure in wireless communications may fail to ensure reliable data transmission due to detection failures by the gNB, leading to potential retransmissions and increased latency.
Innovation Solution
A fallback procedure is introduced where the user equipment (UE) determines whether to switch from a 2-step RACH procedure to a 4-step RACH procedure based on specific criteria, such as the number of transmissions without receiving a response message (MsgB) or a predefined time threshold, allowing for more reliable data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the 2-step RACH procedure is used to reduce latency, then the transmission speed is improved, but the reliability of data transmission deteriorates due to detection failures by gNB
Solution Approach 1:
The system dynamically switches between 2-step and 4-step RACH procedures based on detection success. When MsgB is not received within the threshold time, the UE transitions from the faster 2-step procedure to the more reliable 4-step procedure, making the system adaptive to channel conditions and detection outcomes
Solution Approach 2:
The system changes the procedural parameter (number of RACH steps) based on the receipt of MsgB. The threshold mechanism monitors time or message count parameters, and when thresholds are exceeded, the system transitions from 2-step to 4-step procedure to ensure reliable delivery
2Loss of time
If the 2-step RACH procedure is used to avoid retransmissions, then the time consumption is reduced, but the reliability of data transmission deteriorates
Solution Approach 1:
The system prepares for potential failure by implementing a fallback mechanism in advance. The threshold-based monitoring (time threshold or message count threshold) acts as a cushioning measure that triggers transition to the 4-step procedure if the 2-step procedure fails, preventing complete transmission failure
Solution Approach 2:
The MsgB message serves as an intermediary indicator that determines the transmission path. The presence or absence of MsgB within the threshold period mediates the decision between continuing with 2-step procedure or switching to 4-step procedure, ensuring reliable data delivery
3Reliability
If the UE switches to 4-step RACH procedure when 2-step fails, then the reliability of data transmission is improved, but the device complexity increases
Solution Approach 1:
The UE implements dynamic procedure selection with a clear decision threshold (time threshold or message count threshold). This dynamic mechanism automates the complexity management by switching procedures based on objective criteria rather than requiring complex adaptive algorithms
Solution Approach 2:
The system uses simple parameter monitoring (message count or time duration) to trigger procedure switching. This parameter-based approach keeps the complexity manageable by relying on straightforward threshold comparisons rather than complex decision-making logic
Data Source
AI summary
Some embodiments of this disclosure include apparatuses and methods for a fallback procedure for a 2-step random access channel (RACH) procedure for data transmission in a wireless communication system where the apparatuses and methods include at least generating, by a user equipment (UE), a first signal that includes a first message (MsgA) for a 2-step random access channel (RACH) procedure, transmitting, by the UE, the first signal to a next generation NodeB (gNB), determining, by the UE, whether a 4-step RACH procedure is to be used to further transmit the first signal including the MsgA, and further transmitting, by the UE, the first signal to the gNB using the 4 step RACH procedure based on determining that the 4-step RACH procedure should be used.