UE Pico-Cell Attachment Angle Threshold Mechanism
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Solution Overview
Problem
Heterogeneous networks (HetNets) face challenges in providing seamless connections and robust mobility for user equipment (UE), particularly during transitions between macro and small cells, due to interference and varying Reference Signal Receiving Power (RSRP) from pico cells, leading to increased radio link failures (RLF) and handover failures (HOF), especially for medium or high-speed UEs.
Innovation Solution
Implementing a smart handover mechanism in user equipment (UE) that determines an angle or distance threshold to decide whether to permit or inhibit pico-cell attachment based on the moving direction and target pico eNB, using processing circuitry to calculate and set thresholds to minimize RLF and HOF, and communicating with macro and pico eNBs via OFDMA techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a UE attaches to a pico cell with high RSRP, then the user throughput and network capacity are improved, but the radio link failure rate and handover failure rate increase due to rapid RSRP variations when moving at medium or high speed
Solution Approach 1:
The UE performs preliminary actions by determining its moving state (stationary, slow-moving, or fast-moving) based on measurement information before making attachment decisions. For fast-moving UEs, the system proactively configures a second threshold value that is higher than the first threshold, preventing attachment to pico cells that would cause rapid RSRP variations and subsequent failures. This preliminary classification and threshold configuration avoids the reliability issues before they occur.
Solution Approach 2:
The invention changes the threshold parameter dynamically based on the UE's moving state. When the UE is determined to be fast-moving, a second threshold value (higher than the first threshold) is configured for pico cell attachment decisions. This parameter change adapts the attachment criteria to the UE's mobility characteristics, allowing attachment for stationary or slow-moving UEs while preventing attachment for fast-moving UEs, thus resolving the contradiction between throughput and reliability.
2Reliability
If frequent handover is performed for medium or high speed UEs to maintain connection, then the connection robustness is improved, but the overhead for both eNBs and UEs increases excessively
Solution Approach 1:
The system performs preliminary classification of UE mobility states and configures appropriate threshold values before handover decisions are made. For fast-moving UEs, the second (higher) threshold is configured in advance, which prevents unnecessary handover attempts to pico cells that would result in rapid failure and re-handover cycles. This preliminary action eliminates excessive handover overhead while maintaining connection robustness through appropriate cell selection.
Solution Approach 2:
The UE provides feedback to the network about its measurement information and moving state, which enables the network to determine the appropriate threshold configuration. This feedback mechanism allows the system to adapt handover parameters based on actual UE mobility patterns, preventing excessive handover overhead for fast-moving UEs while maintaining robust connections for slower UEs through informed, feedback-driven parameter adjustment.
3Productivity
If the UE uses a lower threshold for pico cell attachment, then more UEs can attach to pico cells improving network capacity, but more UEs will experience RLF and HOF due to rapid RSRP variations
Solution Approach 1:
The invention implements parameter changes by configuring different threshold values based on UE moving state. The first threshold (lower) is used for stationary or slow-moving UEs to maximize network capacity and pico cell utilization. The second threshold (higher) is configured for fast-moving UEs to prevent attachment to pico cells with rapidly varying RSRP. This parameter adaptation resolves the contradiction by allowing aggressive attachment policies for suitable UEs while applying conservative policies for fast-moving UEs.
Solution Approach 2:
The system applies local quality by tailoring the attachment threshold to each UE's specific mobility characteristics. Instead of using a uniform threshold for all UEs, the system determines individual UE moving states and configures appropriate thresholds locally for each UE. This allows the network to maximize capacity for stationary UEs while preventing failures for fast-moving UEs through localized, adaptive threshold configuration.
Data Source
AI summary
Embodiments of user equipment (UE) and method for pico-cell attachment and attachment inhibiting are generally described herein. In some embodiments, the UE may determine an angle threshold, calculate an angle between a moving direction and a direction toward the target pico eNB, permit pico-cell attachment if the calculated angle is less than or equal to the angle threshold and inhibit pico-cell attachment when the calculated angle is greater than the angle threshold. In some angle-limitation embodiments, the UE may be configured to receive the angle threshold that is broadcasted by a target pico eNB using the SIBs which may be transmitted on the DL-SCH. In some minimum-distance threshold embodiments, the UE is configured to calculate the angle threshold from a distance threshold and a distance to a target pico eNB.