User Equipment 2-Step RACH Fallback to 4-Step Random Access
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Solution Overview
Problem
The operations of retransmission in the 2-step RACH of the radio communication system are unclear, leading to inefficiencies in latency reduction and success rate of random access, especially in poor communication environments.
Innovation Solution
The user equipment is equipped with a transmitting unit for the first data in the first step of a 2-step RACH and a receiving unit for the second data, with the capability to fallback to a 4-step RACH during retransmissions, based on specific conditions such as successful preamble or PUSCH reception, to optimize power ramping and number of retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If 2-step RACH is used to reduce latency, then random access latency is reduced, but retransmission operations become unclear leading to lower success rate in poor communication environments
Solution Approach 1:
The patent implements dynamic fallback from 2-step RACH to 4-step RACH based on retransmission count and communication conditions. The system transitions from a static 2-step procedure to a dynamic hybrid approach where the access method adapts based on success/failure conditions, ensuring reliability while maintaining low latency when possible
Solution Approach 2:
The patent changes the operational parameters of the RACH procedure by introducing conditional fallback mechanisms. When retransmission conditions are met (e.g., maximum retransmission count reached or NACK received), the system changes from 2-step to 4-step RACH mode, adjusting the procedural parameters to ensure successful access in poor communication environments
2Reliability
If fallback to 4-step RACH is performed at retransmission, then success rate increases in poor communication environments, but procedure complexity increases
Solution Approach 1:
The patent employs feedback mechanisms where the base station sends ACK/NACK indications to the terminal based on successful reception of MsgA. This feedback drives the fallback decision, automatically triggering a switch from 2-step to 4-step RACH when needed, thereby managing complexity through condition-based automation rather than complex procedural design
Solution Approach 2:
The system performs self-service by automatically detecting retransmission conditions and initiating fallback to 4-step RACH without requiring complex external control. The terminal monitors its own transmission status and base station responses, and autonomously decides when to switch procedures, simplifying the overall system architecture
Data Source
AI summary
A user equipment includes a transmitting unit configured to transmit first data in a first step of a 2-step RACH; and a receiving unit configured to receive second data in a second step of the 2-step RACH. The user equipment performs fallback to a 4-step RACH at the time of retransmission of the first data. In addition, provided is a user equipment including: a transmitting unit configured to transmit first data in a first step of a 2-step RACH; and a receiving unit configured to receive second data in a second step of the 2-step RACH. The user equipment performs fallback to a 4-step RACH according to the received second data.