Conditional Handover Resource Reservation for 5G
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Solution Overview
Problem
In conditional handover (CHO) procedures for 5G networks, there is a significant delay between reference signal index specific measurements and the transmission of a random access preamble, leading to potential drops in random access resource quality, which may result in increased handover interruption times.
Innovation Solution
The proposed solution involves configuring user devices to report reference signal index specific measurements to the serving gNB, which then signals these measurements to target cells. These target cells reserve contention-free random access resources, allowing the user device to perform a contention-free random access when the conditions are met, thereby reducing handover interruption times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the user device waits for the network to process measurements and allocate random access resources before accessing the target cell, then the handover reliability is improved, but the handover interruption time increases
Solution Approach 1:
The network performs preliminary actions by allocating contention-free random access resources to the target cell in advance based on measurement reports from the user device. This allows the user device to immediately access the target cell using pre-allocated resources when handover conditions are met, eliminating the need to wait for resource allocation during handover execution, thus reducing handover interruption time while maintaining reliability
2Device complexity
If the user device performs random access using contention-based random access resources, then the device complexity is reduced, but the handover interruption time increases and reliability decreases
Solution Approach 1:
The user device autonomously determines when to switch from contention-based to contention-free random access by monitoring whether the target cell has allocated CFRA resources based on its measurement reports. This self-service mechanism allows the device to automatically use the simpler contention-free access method when available, reducing both handover interruption time and improving reliability without increasing device complexity
Data Source
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AI summary
An apparatus suitable for at least to: receive, from a serving access node, a random access update precondition and a configuration with regard to a conditional handover, wherein the configuration indicates at least one handover candidate cell; carry out measurements according to the configuration, and if the random access update precondition is fulfilled, transmit a message to the serving access node, the message comprising information obtained by the measurements and indicating at least one beam of at least one handover candidate cell and/or at least one handover candidate cell that caused the random access update precondition being fulfilled for obtaining a random access resource configuration for carrying out the conditional handover.