UE Handover from Network Energy Saving Cell
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Solution Overview
Problem
In wireless communications, user equipment (UE) handover from a network energy saving (NES) cell poses challenges due to the uncertainty of when the source cell enters sleep mode, leading to potential radio link failures (RLF) and inefficient battery usage.
Innovation Solution
The proposed solution involves a conditional handover configuration that includes handover conditions, a first timer value, and a second timer value. The UE starts a first timer when handover conditions are met and receives a second signaling before the timer expires, allowing for a controlled handover to a candidate cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the source cell enters sleep mode to save energy, then network energy consumption is reduced, but handover reliability deteriorates due to uncertainty of sleep mode entry timing
Solution Approach 1:
The network entity performs preliminary actions by sending a first signaling indicating conditional handover configuration and a second signaling indicating start of sleep time before the source cell actually enters sleep mode. This allows the UE to prepare for handover in advance, measuring and evaluating candidate cells while the source cell is still active, thereby ensuring reliable handover execution even when the source cell enters sleep mode unexpectedly.
2Measurement precision
If the UE continuously monitors handover conditions without a time frame, then handover decision accuracy is improved, but battery consumption increases
Solution Approach 1:
The patent introduces dynamic timer mechanisms (first timer and second timer) that adapt the handover monitoring process. The first timer is started when handover conditions are met, and the second timer is started when the UE receives the second signaling. These timers create a finite, dynamic time frame for measurement and evaluation, allowing the UE to stop monitoring when the timer expires, thus reducing battery consumption while maintaining handover decision accuracy within the active monitoring period.
3Reliability
If the UE performs measurements and evaluations indefinitely, then handover reliability is improved, but loss of time increases due to unnecessary prolonged monitoring
Solution Approach 1:
The network entity sends the second signaling indicating start of sleep time in advance, allowing the UE to know when the source cell will enter sleep mode. The UE then performs measurements and evaluations within the finite time frame defined by the timers, focusing efforts on the critical period before sleep mode entry. This preliminary information allows the UE to avoid indefinite monitoring while ensuring reliable handover decisions are made in the most critical time window.
Data Source
AI summary
Various aspects of the present disclosure relate to user equipment (UE) handover from a network energy saving cell. A timeline of different events allows the UE to make a reliable decision on executing a handover to a target cell, e.g., by providing the UE with the knowledge that there is a finite time before the source cell sleeps and therefore measurement or evaluation to find a target cell for handover may continue. For example, a remaining time to sleep (RTS) value may be defined that indicates an amount of time that the source cell remains active after sending a cell switch off indication to the UE. The source cell enters sleep only after the RTS time indicated in the cell switch off indication elapses. The UE remains active in the source cell until the RTS time elapses and performs measurement and measurement evaluation of candidates.