Random Access Response Reserved Bit for 5G NR-U Identification
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Solution Overview
Problem
In 5G NR-U communication systems, the prolonged random access response window leads to confusion in RA-RNTI identification due to fierce competition for unlicensed frequency band resources, resulting in failed random access attempts.
Innovation Solution
Incorporating a reserved bit in the random access response message to uniquely identify the receiving terminal within the extended random access response window, allowing for accurate determination of the user equipment and successful access even in overlapping transmission units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the random access response window length is increased to provide more transmission opportunities, then the access success rate is improved, but RA-RNTI identification confusion occurs
Solution Approach 1:
The random access response window is divided into multiple transmission units (e.g., slots or subframes). Each transmission unit can independently carry a random access response message with its own RA-RNTI identification. This segmentation allows the system to extend the response window duration while maintaining clear RA-RNTI identification in each segment, thereby resolving the contradiction between providing more transmission opportunities and avoiding identification confusion.
2Duration of action of moving object
If the random access response window exceeds one radio frame, then more transmission opportunities are available, but terminal identification becomes ambiguous
Solution Approach 1:
A new identification field or enhanced identification mechanism is introduced as an intermediary element within the random access response message. This intermediary carries precise terminal identification information (such as preamble identifier or timing advance information) that can uniquely identify the target terminal even when the response window spans multiple radio frames. This resolves the ambiguity in terminal identification while maintaining the extended window duration for more transmission opportunities.
Data Source
AI summary
A method for random access includes: after sending a random access preamble, monitoring a random access response message in a random access response window, wherein a length of the random access response window exceeds a preset value, the random access response message includes a reserved bit that indicates a receiving terminal of the random access response message; reading a value of the reserved bit in the random access response message; determining the receiving terminal of the random access response message according to the value of the reserved bit; and when determining that the receiving terminal is the first user equipment, sending a Message3 based on a message content of the random access response message.