Inter-cell Handover via SRS Measurement Forwarding
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Solution Overview
Problem
In multi-sector cell deployments for LTE, traditional handover decisions and inter-cell interference management are inefficient due to lack of accurate uplink channel quality estimates and inter-cell interference coordination, leading to potential handover failures and suboptimal resource allocation.
Innovation Solution
The method involves forwarding SRS channel quality measurements among eNodeBs over the X2 interface, enabling high-quality handover decisions and inter-cell interference management by computing uplink geometry and comparing it with predefined thresholds, which allows for sector selection and improved interference coordination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional handover decisions are used in multi-sector cell deployments, then the handover procedure is simple, but handover success rate is low due to lack of accurate uplink channel quality estimates
Solution Approach 1:
The patent introduces SRS (Sounding Reference Signal) measurements as an intermediary mechanism to obtain accurate uplink channel quality estimates. The serving eNodeB configures SRS resources for UEs and collects SRS measurements from neighboring eNodeBs via the X2 interface, using these measurements as the basis for handover decisions. This intermediary measurement mechanism resolves the contradiction by providing the needed measurement precision without complicating the handover procedure itself.
Solution Approach 2:
The patent performs preliminary SRS measurements and channel quality assessments before the actual handover decision is made. The serving eNodeB proactively configures SRS resources, collects measurements from neighboring cells, and computes uplink geometry in advance, allowing for more reliable handover decisions when needed.
2Reliability
If SRS channel quality measurements are shared among eNodeBs, then handover decision quality is improved, but signaling load increases
Solution Approach 1:
The patent extracts only the essential SRS measurement data and channel quality information needed for handover decisions, rather than sharing all measurement data. The serving eNodeB requests and receives only the relevant SRS measurements from neighboring eNodeBs via X2 interface, filtering out unnecessary information to minimize signaling load while maintaining decision quality.
Solution Approach 2:
The patent implements partial measurement sharing where only the necessary SRS measurements for handover evaluation are exchanged between eNodeBs, rather than sharing all possible measurement data. This partial action approach maintains handover decision quality while controlling signaling overhead.
3Object-affected harmful factors
If sector-level interference management is implemented, then inter-cell interference is reduced, but device complexity increases
Solution Approach 1:
The patent segments the interference management function by implementing it at the sector level rather than cell level. Each eNodeB can independently manage interference for its sectors using SRS measurements, dividing the complex cell-wide interference management into simpler sector-specific tasks. This segmentation reduces the complexity of implementing granular interference management.
Solution Approach 2:
The patent applies local quality by enabling interference management decisions to be made independently for each sector based on local SRS measurements. Each eNodeB optimizes interference coordination for its specific sectors using locally available measurement data, rather than requiring complex global optimization across all sectors.
Data Source
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AI summary
A method in a controller for a first cell in a mobile cellular network for making a decision to handover a user equipment to a second cell of the mobile cellular network is described. The method may include obtaining a first measurement of an uplink signal from a user equipment at the first cell, obtaining a second measurement of an uplink signal from the user equipment at the second cell, and making a decision to handover the user equipment from the first cell to the second cell using the obtained first and second measurements.