Adaptive CRE Offset for LTE Handover Reliability
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Solution Overview
Problem
Conventional Cell Range Expansion (CRE) techniques in wireless communications do not account for the speed of User Equipment (UE) and the balance of downlink/uplink traffic, leading to potential handover failures and suboptimal system performance, especially for high-speed UEs experiencing mainly downlink traffic.
Innovation Solution
Adaptive CRE-based offset parameters are introduced to adjust the Received Signal Received Power (RSRP) and Received Signal Received Quality (RSRQ) thresholds based on the UE's speed and traffic balance, allowing for dynamic adjustment of CRE parameters to optimize cell selection and reduce handover failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional CRE technique is used to increase UE connection time to small cell, then small cell connection duration is improved, but handover failure rate increases for high-speed UEs
Solution Approach 1:
The patent applies dynamics by making the CRE offset parameter adaptive rather than fixed. The offset is dynamically adjusted based on UE speed measurements, allowing the system to optimize small cell connection duration for low-speed UEs while preventing handover failures for high-speed UEs. Specifically, when UE speed exceeds a threshold, the CRE offset is reduced or set to zero, ensuring reliable handover timing for moving users.
Solution Approach 2:
The patent changes the CRE offset parameter based on UE speed conditions. For low-speed UEs, a positive CRE offset is applied to extend small cell connection time and improve offloading. For high-speed UEs, the offset is reduced to zero or negative values to ensure timely handover and prevent connection failures. This parameter adaptation resolves the contradiction between extending connection time and maintaining handover reliability.
2Productivity
If conventional CRE technique is used to offload UE from macro cell to small cell, then macro cell bandwidth is saved, but system performance optimization is lost when UE speed is not considered
Solution Approach 1:
The patent changes the CRE offset parameter based on UE speed and traffic conditions. For stationary or low-speed UEs with downlink-heavy traffic, a positive CRE offset enables effective offloading to small cells, improving macro cell bandwidth utilization. For high-speed UEs or those with balanced traffic, the offset is adjusted to maintain optimal connection, ensuring system performance is not degraded. This adaptive parameter adjustment resolves the contradiction between bandwidth savings and performance optimization.
Solution Approach 2:
The patent implements feedback mechanisms where the eNB monitors UE speed, traffic balance, and connection performance. Based on this feedback, the CRE offset parameter is dynamically adjusted to optimize both macro cell bandwidth utilization and overall system performance. The system learns from actual UE behavior and adapts the offloading strategy accordingly.
3Device complexity
If fixed CRE offset parameter is used to simplify implementation, then device complexity is reduced, but handover failure and performance optimization are caused for different UE conditions
Solution Approach 1:
The patent transitions from a static CRE offset configuration to a dynamic one that automatically adapts to UE conditions. The eNB monitors UE speed and traffic patterns, then adjusts the CRE offset parameter accordingly. This dynamic approach maintains simple implementation at the UE side while improving reliability through network-side adaptation based on real-time conditions.
Solution Approach 2:
The system performs self-optimization by automatically adjusting CRE parameters based on monitored UE conditions without requiring complex UE-side processing. The eNB autonomously determines appropriate offset values based on UE speed, traffic balance, and connection performance, reducing overall system complexity while improving handover reliability.
Data Source
AI summary
Embodiments disclosed herein relate to devices and methods that provide adaptive CRE-based offset parameters that take into account the speed of a UE and that take into account the DL/UL traffic balance being experienced by the UE. For example, if the speed of a UE is greater than the predefined speed, the UE utilizes an adaptive CRE-based offset parameter that has a low value or is equal to zero. Similarly, if the balance of downlink/uplink traffic being experienced by a UE is mainly downlink traffic, the UE utilizes an adaptive CRE-based offset parameter that has a low value or is equal to zero. Consequently, the embodiments disclosed herein reduce the handover failure associated with CRE particularly for high speed UEs while also being able to increase downlink system capacity if the balance of the downlink and uplink traffic experienced by the UE is mostly downlink traffic.