PRACH Preamble Transmission for 5G Random Access Latency
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Solution Overview
Problem
In 5G New Radio (NR) networks, UEs without Tx/Rx beam correspondence face increased access latency due to the inability to determine the best Tx beam for RACH messages, leading to inefficient random access procedures and potential misadjustment of transmission parameters by the gNB, resulting in unnecessary retransmissions and decreased system efficiency.
Innovation Solution
Allowing UEs to transmit multiple PRACH preambles within a given RAR window and enabling them to respond to all received RARs in MSG3, with the gNB synchronizing which procedures to continue and adjusting parameters based on this information, thereby reducing access latency and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE transmits multiple PRACH preambles to handle beam uncertainty, then access reliability improves, but access latency increases
Solution Approach 1:
The patent applies preliminary action by having the UE transmit multiple preambles in advance within the same RAR window before the gNB finalizes beam selection. The UE transmits preambles corresponding to multiple candidate beams proactively, allowing the gNB to receive and evaluate multiple beams simultaneously rather than sequentially, thereby reducing the time needed for beam determination while maintaining reliability.
Solution Approach 2:
The patent implements dynamics by allowing flexible transmission of multiple preambles within the RAR window rather than following a fixed single-preamble procedure. The UE dynamically selects and transmits multiple preambles based on beam correspondence conditions, and the gNB dynamically adjusts its response based on which preambles were received, creating an adaptive system that optimizes both reliability and latency.
2Measurement precision
If gNB transmits separate RAR for each detected preamble, then response accuracy improves, but system efficiency decreases
Solution Approach 1:
The patent applies merging by combining multiple separate RAR responses into a single consolidated RAR message. Instead of transmitting individual RARs for each detected preamble, the gNB aggregates all detected preambles and their corresponding RAR information into one unified response message, thereby maintaining response accuracy while significantly improving system efficiency by reducing redundant transmissions.
Solution Approach 2:
The patent implements universality by designing the RAR response to serve multiple functions simultaneously. The single RAR message universally addresses multiple preambles and UEs, providing a multi-functional response that can handle various scenarios (single preamble, multiple preambles, beam correspondence cases) within one standardized message structure, thereby improving efficiency without sacrificing accuracy.
3Manufacturing precision
If UE waits for RAR before transmitting MSG3, then transmission accuracy improves, but access latency increases
Solution Approach 1:
The patent applies preliminary action by allowing the UE to prepare and transmit MSG3 before receiving the final RAR confirmation. The UE proactively transmits MSG3 containing its identity and beam information within the RAR window based on preliminary preamble transmissions, rather than waiting passively for the RAR, thereby reducing latency while maintaining accuracy through subsequent RAR confirmation.
Data Source
AI summary
A method including, detecting, by a base station in a wireless communication system, within an RAR window, at least one of multiple first messages from a plurality of user equipments, wherein the plurality of user equipments is permitted to transmit multiple first messages within the RAR window, and wherein each first message includes a PRACH preamble; in response to receiving at least one PRACH preamble in the at least one of multiple first messages, transmitting at least one second message including an RAR downlink channel for each preamble received; receiving at least one third message, from at least one user equipment of the plurality of user equipments, including a beam connection request and transmitting at least one fourth message to the at least one user equipment on the requested beam.