Uplink Synchronization Timer Handling During Wireless Handover
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Solution Overview
Problem
In wireless communication systems, handover failures occur due to the absence of a time alignment timer (TAT) value when a default Medium Access Control (MAC) configuration is used during the handover process, leading to unsuccessful uplink transmissions.
Innovation Solution
The method involves receiving a handover command from the network, determining if a default MAC configuration is included, and if so, obtaining an additional TAT value either from the target cell's broadcast information or the handover message to perform the handover procedure successfully.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a default MAC configuration is used during handover, then the handover command size is reduced and processing is simplified, but the uplink synchronization timer value is missing causing handover failure
Solution Approach 1:
The patent applies preliminary action by having the terminal retrieve the uplink synchronization timer value from pre-stored target cell information before the handover actually occurs. The terminal stores timer values for multiple target cells in advance, so when handover is needed, the terminal can immediately access the required timer value without waiting for network provisioning, ensuring handover success while maintaining command simplicity.
2Reliability
If the terminal waits for network to provide TAT value, then uplink transmission can be enabled, but handover time is extended and continuity is broken
Solution Approach 1:
The terminal performs preliminary action by pre-storing timer values for multiple target cells during the cell search and measurement phase. When handover is triggered, the terminal immediately retrieves the required timer value from its local storage rather than waiting for the network to provide it, eliminating the waiting time and maintaining continuous communication.
Solution Approach 2:
The patent applies self-service by enabling the terminal to autonomously retrieve and apply the uplink synchronization timer value from its own stored target cell information. The terminal independently completes the handover preparation without requiring continuous network intervention, thereby reducing handover time and ensuring continuity.
Data Source
AI summary
Disclosed is the radio (wireless) communication system providing a radio communication service and the terminal, and more particularly, to a method of handling an uplink synchronization timer during a handover procedure in an Evolved Universal Mobile Telecommunications System (E-UMTS) evolved from the Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.