Handover Measurement via Frequency Sub-band Segmentation
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Solution Overview
Problem
In LTE and E-UTRAN systems, existing handover measurement methods face challenges in accurately determining user equipment location and channel quality, leading to inefficient handover decisions due to varying transmission power across the cell system bandwidth and interference coordination schemes, which affect pilot symbol measurements and channel quality assessments.
Innovation Solution
The method involves performing handover measurements over specific frequency sub-bands based on pilot symbols, with varying measurement rates and frequencies depending on the user equipment's location within the cell (cell-edge or cell-center) and channel quality, allowing for more accurate handover decisions by determining the appropriate frequency sub-bands for data reception and adjusting measurement intervals accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If handover measurements are performed over the entire operating bandwidth, then measurement accuracy is improved, but power consumption increases and measurement complexity increases
Solution Approach 1:
The operating bandwidth is divided into multiple frequency sub-bands, and handover measurements are performed selectively on specific sub-bands rather than the entire bandwidth. The user equipment determines which sub-bands to measure based on its location (cell-center or cell-edge) and channel quality, thereby reducing the total measurement burden and power consumption while maintaining necessary measurement accuracy.
Solution Approach 2:
Different measurement strategies are applied to different frequency sub-bands based on local conditions. Cell-edge users measure both cell-edge and cell-center sub-bands of serving and neighboring cells, while cell-center users measure only cell-edge sub-bands of neighboring cells. This localized measurement approach optimizes power consumption according to the specific operational context of each user.
2Measurement precision
If handover measurements are performed frequently, then handover decision accuracy is improved, but power consumption and processing overhead increase
Solution Approach 1:
The measurement frequency and sub-band selection are dynamically adjusted based on the user equipment's current state. When the user is located at the cell-edge with poor channel quality, measurements are performed more frequently and on more sub-bands. When the user is at the cell-center with good channel quality, measurements are performed less frequently and on fewer sub-bands, thereby reducing processing overhead while maintaining handover decision accuracy when needed.
3Reliability
If interference coordination schemes are applied with varying transmission power across frequency, then system performance is improved, but measurement complexity and difficulty increase
Solution Approach 1:
The measurement strategy is adapted to the local frequency sub-band conditions created by interference coordination schemes. By measuring only the relevant sub-bands where the user equipment is likely to be scheduled (cell-edge sub-bands for cell-edge users, cell-center sub-bands for cell-center users), the patent simplifies the measurement process despite varying transmission powers across different frequency resources.
Data Source
AI summary
A UE performs pilot measurements over a frequency sub-band of serving cell and adjacent cells based on pilot symbols for used in handover. UE uses channel quality measurement result to adjust frequency sub-band and periodicity of pilot measurement. In interference coordination scheme, UE is classified into cell edge or cell center UE based on channel quality measurement result. For downlink data reception, UE in cell edge is allocated cell edge frequency sub-band and UE in cell center is allocated with cell center frequency sub-band. If UE is in cell edge of the serving cell, UE also performs pilot measurement over cell edge frequency sub-band. If UE is in cell center, UE also performs pilot measurement over cell center frequency sub-band of the serving cell. When UE is located in cell edge, it performs measurement at a higher rate than when it is located in cell center.