Pre-allocating Dedicated Preambles for Fast LTE Handover
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Solution Overview
Problem
The existing LTE handover process experiences significant delays due to X2 signaling delays, leading to potential handover failures, especially in heterogeneous network scenarios and when Discontinuous Reception (DRX) is applied, resulting in poor handover performance.
Innovation Solution
Pre-allocating resources, including dedicated random access preambles, in target cell candidates before the handover decision, allowing for immediate handover command transmission upon receiving a measurement report, thereby reducing handover delays and increasing the reliability of handover command transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If resources are allocated after handover decision in conventional LTE, then resource availability is ensured, but handover delay increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-allocating resources including dedicated random access preambles in target cells before the handover decision is made. This allows the serving eNodeB to immediately transmit the handover command to the UE without initiating resource allocation procedures after the handover decision, thereby reducing handover delay while ensuring resource availability through advance preparation
2Productivity
If X2 signaling procedures are followed for resource allocation, then resource management is proper, but handover command transmission is delayed
Solution Approach 1:
The patent performs resource allocation and obtains dedicated random access preambles in advance through X2 signaling before the handover decision is made. By completing the resource allocation procedure preliminarily, the patent eliminates the need for time-consuming X2 signaling exchanges after the handover decision, thereby accelerating handover execution while maintaining proper resource management through the initial signaling procedure
Solution Approach 2:
The patent extracts the resource allocation procedure from the post-handover decision timeline and performs it separately before the handover decision is made. This separation allows the handover command transmission to proceed immediately without waiting for resource allocation signaling, thus improving handover execution speed while maintaining the necessary signaling complexity for proper resource management
3Measurement precision
If measurement reports are waited for before handover decision, then accurate target cell selection is achieved, but handover delay increases
Solution Approach 1:
The patent performs resource allocation in target cells as a preliminary action before receiving measurement reports from the UE. This advance preparation ensures that when accurate target cell selection is made based on measurement reports, the resources are already allocated and ready, eliminating the time delay that would otherwise occur between measurement report reception and resource allocation
Solution Approach 2:
The patent applies preliminary anti-action by pre-allocating resources in potential target cells before the actual handover decision is triggered by measurement reports. This preliminary preparation counteracts the potential delay that would arise from waiting for measurement reports before initiating resource allocation, ensuring that accurate target cell selection can be immediately executed without time loss
Data Source
AI summary
The present invention relates to a method in an RBS of a wireless network, for supporting HO of a UE in a served cell. The method comprises pre-allocating resources for HO of the UE to a target cell candidate. The pre-allocated resources comprise a dedicated preamble for the target cell candidate. The method also comprises receiving a measurement report from the UE triggering a HO and comprising a list of neighbor cells, determining if a cell in the list of neighbor cells corresponds to one of the at least one target cell candidates, and when they correspond transmitting a HO command to the UE comprising the dedicated preamble for the target. The present invention also relates to a corresponding method in the target RBS and to the serving and target RBS themselves.