Terminal Handover Using Pre-Configured RRC And Random Access
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Solution Overview
Problem
Handover processes in cellular communication systems cause degradation of communication efficiency due to the time required for synchronization establishment and connection switching, during which user data transmission is interrupted.
Innovation Solution
The terminal apparatus receives and performs pre-configured RRC settings and executes a random access process with the target base station before actual handover, utilizing pre-measured CSI-RS and PDCCH orders to establish uplink synchronization and reserve resources, thereby reducing the time needed for handover completion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal apparatus executes synchronization establishment and connection switching processing after receiving handover instruction, then the handover connection is successfully established, but the communication efficiency deteriorates due to user data transmission interruption during processing
Solution Approach 1:
The terminal apparatus performs synchronization establishment and connection switching processing before the actual handover is triggered. Specifically, the terminal receives RRC reconfiguration messages containing target cell configuration information in advance, performs downlink synchronization establishment using CSI-RS resources, and prepares uplink resources. When handover is actually triggered, these pre-established connections enable immediate data transmission without interruption, thus resolving the contradiction between reliable handover establishment and communication efficiency.
2Reliability
If the terminal apparatus performs complete RRC layer processing during handover, then the connection switching is reliable, but the handover time increases causing communication efficiency degradation
Solution Approach 1:
The terminal apparatus performs RRC reconfiguration and synchronization establishment in advance before handover is actually triggered. The terminal receives target cell configuration information, performs downlink synchronization using pre-configured CSI-RS resources, and prepares uplink transmission resources beforehand. This preliminary processing eliminates the need for time-consuming RRC layer operations during actual handover, thus reducing handover time while maintaining reliable connection switching.
Solution Approach 2:
The handover process is divided into two distinct phases: a preparation phase where synchronization and resource configuration are established in advance, and an execution phase where the actual handover trigger occurs. This segmentation allows the terminal to perform complex RRC processing during the preparation phase without affecting the speed of the execution phase, thereby reducing overall handover time while ensuring reliable connection switching.
3Speed
If the terminal apparatus uses pre-configured CSI-RS and PDCCH orders for random access, then the synchronization establishment speed increases, but the device complexity increases due to additional pre-configuration processing
Solution Approach 1:
The base station provides the terminal with pre-configured CSI-RS resources and PDCCH order information through RRC reconfiguration messages before handover. The terminal uses these pre-configured resources to perform downlink synchronization establishment and uplink random access without needing to negotiate resources during actual handover. This approach accelerates synchronization establishment while the complexity is managed by reusing existing configuration frameworks rather than creating new processing mechanisms.
Data Source
AI summary
A base station apparatus performs, for a currently connected terminal apparatus, setting of a radio resource control (RRC) layer for another base station apparatus that is a destination candidate for a handover by the terminal apparatus from the base station apparatus, instructs the terminal apparatus to transmit a random access preamble to the other base station apparatus via a physical downlink control channel (PDCCH) order without handover to the other base station apparatus being performed, and transmits, to the terminal apparatus, a command instructing for handover to the other base station apparatus in response to the terminal apparatus being in a state for handover to the other base station apparatus.