Random Access Preamble Collision Avoidance via Backoff Offset
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Solution Overview
Problem
In wireless communication systems, particularly in the context of the New Radio Access Technology (NR) system, the random access procedure faces challenges with random access preamble collisions, which are undesirable and increase latency, necessitating a new method to support the RA procedure effectively.
Innovation Solution
A method for user equipment (UE) to perform a random access procedure by transmitting a first random access preamble, receiving a message with a backoff indicator (BI) and one or more backoff offset (BO) values, and selecting a backoff time based on these values for retransmitting a second random access preamble, where the backoff time is uniformly distributed between the BI and BO values, thereby avoiding collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple UEs transmit random access preambles simultaneously, then the random access procedure can be initiated by multiple UEs, but preamble collisions occur increasing latency
Solution Approach 1:
The base station preliminarily determines a backoff parameter value and includes it in the random access response message before the UE transmits the preamble. This preliminary assignment of backoff timing prevents simultaneous preamble transmissions by different UEs, resolving the collision issue while maintaining efficient access initiation
Solution Approach 2:
The random access response message provides feedback to the UE including a backoff parameter value that indicates when the UE should retransmit the preamble. This feedback mechanism controls the timing of preamble retransmissions to avoid collisions with other UEs, reducing access latency caused by collisions
Data Source
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Figure 3(a)~3(b)
AI summary
The method for a user equipment (UE) performing a random access procedure according to an embodiment of the present invention includes transmitting a first random access preamble; receiving a message including a backoff indicator (BI) and a backoff offset (BO) value; when a random access using the first random access preamble fails, selecting a backoff time based on the BI and the BO value; and transmitting a second random access preamble after the selected backoff time.