Handover Resource Reservation Using Frame Number Offset
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Solution Overview
Problem
Mobile radio communications systems face inefficiencies in handover procedures due to limited availability of Random Access (RA) preambles, leading to potential handover delays and failures, especially when RA preambles are reserved for extended periods without being used.
Innovation Solution
The method involves reserving handover resources for a limited time period and communicating timing information using a frame number offset between the source and target cells, allowing for more efficient allocation and use of RA preambles by ensuring they are not reserved for failed or non-occurring handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover resources (RA preambles) are reserved for extended periods to ensure availability, then handover reliability is improved, but resource efficiency deteriorates due to potential long-term allocation to unused or failed handovers
Solution Approach 1:
The patent implements dynamic resource reservation by introducing a time-limit counter that automatically expires reserved RA preambles after a predetermined period. This dynamic mechanism allows the system to adapt between ensuring handover reliability through reservation and maintaining resource efficiency through automatic expiration, resolving the contradiction between these two opposing requirements
Solution Approach 2:
The patent changes the parameter of resource reservation from static (indefinite allocation) to dynamic (time-limited allocation with automatic expiration). By introducing the time-limit counter parameter, the system can control the duration of resource reservation, thereby balancing handover reliability with resource efficiency
2Reliability
If RA preambles are allocated for long periods to prevent handover failures, then handover success rate is improved, but system productivity deteriorates due to reduced availability for other users
Solution Approach 1:
The patent implements periodic action through the time-limit counter that periodically checks and expires reserved RA preambles. This periodic expiration mechanism ensures that resources are continuously reused for new handovers, maintaining high system productivity while providing sufficient reservation period to ensure handover success
Solution Approach 2:
The dynamic time-limit counter allows the system to balance between maintaining handover success rate through adequate reservation time and maximizing system productivity through timely resource release and reuse for other users
3Reliability
If handover resources are reserved without time limits to ensure availability, then handover reliability is improved, but loss of time deteriorates when resources remain allocated to failed handovers
Solution Approach 1:
The patent applies preliminary action by pre-configuring a time-limit counter with a predetermined expiration period. This preliminary setup ensures that resources are automatically released after the specified time, preventing indefinite allocation to failed handovers and reducing time loss while maintaining reliability during the active reservation period
Data Source
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AI summary
A method and arrangement for handover wherein the handover resource (the dedicated random access preamble) is reserved by the target radio base station (RBS) for a limited period of time, thus increasing the handover efficiency and thereby allowing random access preambles to be used for initial access to a larger extent. The information about the reserved time interval is sent to the UE in the handover command message by means of a frame number offset between the source RBS and the target RBS. The UE uses the information to calculate when to send its synchronisation message to the target RBS. The frame number offset is calculated either by source RBS or by target RBS.