PRACH Transmission to Non-Serving Cells for 5G Mobility Latency
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Solution Overview
Problem
Current 5G and New Radio communication systems lack the ability to trigger terminal devices to perform Physical Random Access Channel (PRACH) transmissions to non-serving cells, leading to increased latency and inefficiency during cell switching.
Innovation Solution
The system enables terminal devices to perform PRACH transmissions for non-serving cells by providing configuration and timing advance values, allowing base stations to send specific DCI formats that trigger PRACH transmissions, enabling uplink timing adjustment before switching to a new cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PDCCH order PRACH transmission is used, then the base station can trigger PRACH transmission for timing adjustment, but the terminal device cannot transmit PRACH to non-serving cells causing increased latency during cell switching
Solution Approach 1:
The patent applies preliminary action by enabling the terminal device to perform PRACH transmission to non-serving cells before actually switching to them. The base station triggers PRACH transmission for a non-serving cell in advance, allowing the terminal to obtain uplink timing information beforehand. This preliminary timing acquisition reduces the latency during subsequent cell switching operations.
Solution Approach 2:
The patent uses DCI format 0_1 as an intermediary mechanism to trigger PRACH transmission for non-serving cells. The DCI format serves as a mediator between the base station and terminal device, carrying instructions to perform PRACH transmission to cells that are not currently serving, thereby enabling cross-cell timing adjustment without direct connection.
2Productivity
If the terminal device performs random access procedure for non-serving cells after switching indication, then the cell switching can be completed, but the system efficiency is reduced due to enlarged latency
Solution Approach 1:
The system performs PRACH transmission to non-serving cells in advance before the actual cell switching occurs. By triggering PRACH transmission for a non-serving cell prior to switching indication, the terminal device can obtain timing advance information beforehand, eliminating the need for post-switching random access procedures and improving system efficiency.
Solution Approach 2:
The base station provides feedback in the form of timing advance values obtained from PRACH transmission to non-serving cells. This feedback mechanism allows the terminal device to use the obtained timing information for subsequent uplink transmissions to the non-serving cell, reducing the overall cell switching time and improving productivity.
Data Source
AI summary
A method includes (1) receiving, by a terminal device, configuration information of PRACH of one or more non-serving cells; (2) receiving, by the terminal device, a control signaling; (3) determining, by the terminal device, a PRACH preamble and a PRACH occasion according to the configuration information; and (4) transmitting, by the terminal device the PRACH preamble in the PRACH occasion. The control signaling indicates the terminal device to transmit PRACH information to a first non-serving cell of the one or more non-serving cells.