Small Data Transmission Cell Reselection Under RAN Congestion
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Solution Overview
Problem
In 5G NR systems, frequent RRC state switching due to small but frequent data transmissions leads to a waste of signaling resources, particularly when the serving or anchor base station is congested or overloaded, hindering efficient data transmission.
Innovation Solution
A data transmission method that allows the serving access network device to reject or terminate Small Data Transmission (SDT) when resource congestion occurs, providing redirection or cell reselection parameters to the terminal device, thereby improving flexibility and reducing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device continues to wait in the current cell when SDT is rejected or fails, then the terminal device may retry SDT establishment, but this results in increased transmission delay and reduced data transmission efficiency
Solution Approach 1:
The access network device proactively provides redirection information and cell reselection priority parameters to the terminal device before SDT failure occurs. When the terminal device receives an SDT rejection or failure indication, it can immediately execute the pre-provided redirection instructions to select a new cell, avoiding the need to wait and retry in the current cell, thus reducing transmission delay while maintaining reliability
2Productivity
If the serving access network device allows SDT when congested or overloaded, then the terminal device can transmit data, but this worsens the network congestion and reduces overall system performance
Solution Approach 1:
The access network device acts as an intermediary that monitors network congestion status and intervenes by providing redirection information to the terminal device. When congestion is detected, the access network device redirects the terminal to a different cell with better resource availability, thereby preventing the congested cell from being further overloaded while still enabling the terminal to transmit data, thus resolving the contradiction between maintaining data transmission and avoiding network congestion
3Productivity
If the terminal device frequently switches RRC state for small data transmissions, then data can be transmitted, but this occupies large amounts of signaling resources and causes resource waste
Solution Approach 1:
The terminal device is enabled to perform autonomous cell reselection based on priority parameters provided by the access network device. Instead of requiring RRC state switching and network-assisted cell selection, the terminal device independently selects appropriate cells for data transmission based on the provided reselection priorities, thereby eliminating the need for frequent RRC state transitions and reducing signaling resource consumption while maintaining data transmission capability
Data Source
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AI summary
This application provides a data transmission method, an apparatus, and a system, which are applied to the field of communication technologies. The data transmission method includes: receiving, by a serving access network device, a first radio resource control RRC message from a terminal device, where the first RRC message is used to establish small data transmission SDT; and if the serving access network device does not meet a requirement of the SDT, sending a second RRC message or a third RRC message to the terminal device, where the second RRC message may be used to indicate the terminal device to terminate the SDT, and the third RRC message may be used to indicate the serving access network device to reject performing the SDT. Based on this solution, once the serving access network device does not meet the requirement of the SDT, the SDT may be rejected or terminated, so that the terminal device can subsequently reselect a cell to initiate the SDT again. Compared with a solution in which a terminal continues to wait in a current cell, data transmission efficiency of the terminal device can be improved.