CoMP Handover Using Geometric Information for Target Cell Selection
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Solution Overview
Problem
Existing mobility management mechanisms in LTE networks do not support macro-diversity transmission or reception, leading to inaccurate target cell selection during handovers, resulting in failed handovers or return to the source cell due to reliance on signal power measurements that do not accurately determine the most suitable target cell.
Innovation Solution
Enhancing handover processing by utilizing geometric information such as angle of arrival, time advance, Round Trip Time (RTT), power headroom, and signal strength to improve target cell selection, and using this information to direct energy and improve signal measurements and transmissions between cells, thereby ensuring more reliable handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional signal power measurements are used for target cell selection, then handover decisions can be made using existing LTE mechanisms, but the accuracy of target cell selection deteriorates leading to failed handovers or return to source cell
Solution Approach 1:
The source eNB performs preliminary calculations of geometric information (angle of arrival, time advance, RTT) before handover decision, and shares this information with candidate target eNBs in advance. This allows target eNBs to prepare their reception parameters and make more informed handover decisions based on predicted UE position and geometry, rather than relying solely on instantaneous signal power measurements.
Solution Approach 2:
Geometric information acts as an intermediary parameter between the source eNB and target eNBs. Instead of directly using signal power measurements which can be ambiguous in CoMP scenarios, the patent introduces geometric information (angle, time advance, RTT) as a mediator that provides more reliable spatial and temporal context for handover decision-making.
2Measurement precision
If geometric information is shared between source and target eNBs to improve handover accuracy, then target cell selection accuracy improves, but the complexity of handover processing increases
Solution Approach 1:
The source eNB calculates geometric information (angle of arrival, time advance, RTT) in advance and shares it with candidate target eNBs before the handover execution. This preliminary action reduces the real-time processing burden during actual handover, as target eNBs receive pre-computed geometric data that they can use immediately for parameter adjustment and reception optimization.
Solution Approach 2:
Each eNB independently calculates and uses geometric information for its own handover decisions and reception optimizations. The source eNB calculates geometric info for outgoing UEs, while target eNBs calculate geometric info for incoming UEs based on shared data. This self-service approach distributes the computational burden rather than requiring centralized complex processing.
3Manufacturing precision
If geometric information is used to direct energy and improve signal measurements, then transmission quality improves, but the amount of information processing and coordination increases
Solution Approach 1:
Geometric information is used to optimize local transmission parameters at each eNB-UE interface. Each target eNB adjusts its reception parameters (beamforming, timing advance, frequency offset) based on the specific geometric relationship with the incoming UE. This localized optimization improves transmission quality without requiring global coordination of all network parameters.
Solution Approach 2:
The patent changes the parameter set used for handover decisions from traditional signal power metrics to geometric parameters (angle of arrival, time advance, RTT). These geometric parameters directly inform physical layer transmission parameters such as beam direction, timing synchronization, and frequency offset compensation, creating a more direct link between measurement and transmission optimization.
Data Source
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AI summary
In one aspect, the present invention in one or more embodiments improves mobility management-e.g., handover processing enhancement-by providing/utilizing additional information in combination with CoMP operation, for enhancing the handover procedure. For example, the additional information is used to improve judging the most suitable target cell (14). The additional information can be, for example, angle of arrival or time advance of the UE (20) in handover, RTT, power headroom or signal strength. In at least one embodiment, the information used for handover processing at source and/or target base stations (12-1, 12-2) is enhanced or otherwise made richer by the use of "geometric information" for mobile terminals (20). In one such embodiment, the geometric information used for handover processing associated with a given terminal (20) indicates something about the mobile terminal's position (relative or absolute).