Handover Timing Advance via Downlink Measurements
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Solution Overview
Problem
In heterogeneous networks, user equipment (UE) experiences data interruptions and packet delays during handovers between macro cells and small cells, such as pico cells or femto cells, leading to a poor user experience due to the unplanned deployment of low-power cells and the resulting multiple handovers.
Innovation Solution
The method involves sending a measurement report from the UE to the serving cell, which includes downlink timing measurements for the target cell, and transmitting a reconfiguration complete message to the target cell, allowing the UE to adjust its uplink transmit timing based on the measured downlink timing differences between the serving and target cells, thereby reducing the need for uplink synchronization at the target cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low-power cells are deployed in an unplanned clustered manner to increase data throughput and coverage, then network capacity and coverage are improved, but the number of handovers increases causing data interruption and packet delay
Solution Approach 1:
The patent performs preliminary actions by having the UE send measurement reports including downlink timing measurements before handover is executed. The serving cell uses these pre-collected timing measurements to calculate uplink timing advance values, so that when handover occurs, the UE can immediately transmit uplink signals with correct timing without requiring synchronization procedures at the target cell, thus reducing handover time while maintaining the benefits of clustered low-power cell deployment
2Area of stationary object
If multiple handovers occur while UE traverses macro cell coverage area in clustered deployment, then coverage is improved, but data interruption and packet delay increase resulting in poor user experience
Solution Approach 1:
The patent performs preliminary timing measurements and calculations before handover. The UE measures downlink timing from the target cell and sends this information to the serving cell in advance. The serving cell calculates the uplink timing advance value needed for the target cell based on these measurements, so that when handover occurs, the UE can immediately transmit with correct timing, eliminating data interruption and maintaining reliable data transmission across coverage areas
Solution Approach 2:
The patent uses downlink timing measurements as an intermediary parameter. Instead of directly synchronizing uplink transmissions during handover, the system uses downlink timing measurements as a mediator to calculate the required uplink timing advance. This intermediary approach allows the UE to determine the correct uplink timing for the target cell without requiring complex synchronization procedures, thus maintaining data transmission reliability during handover
Data Source
AI summary
A method at a user equipment for handover from a serving cell to a target cell, the method sending a measurement report to the serving cell; and transmitting a reconfiguration complete message to the target cell; wherein the measurement report includes downlink timing measurements for the target cell. Further, a method at a source network element for handover of a user equipment from the source network element to a target network element, the method receiving a measurement report from the user equipment; sending a handover request to the target network element; receiving a handover request acknowledgement from the target network element, the handover request acknowledgement including a reconfiguration message and at least one downlink subframe in which an uplink grant is expected at the target network element for the user equipment; and forwarding the reconfiguration message and at least one downlink subframe to the user equipment.