UE Power Saving via DRX and WLAN TIM Alignment
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Solution Overview
Problem
In Tight Coupled Interworking (TCIW) operations, existing power saving methods for User Equipment (UE) in wireless communication systems fail to efficiently align Discontinuous Reception (DRX) cycles with WLAN power saving modes, leading to suboptimal battery life and increased signaling overhead.
Innovation Solution
The UE determines a WLAN listen interval and selects a TIM message to monitor based on the DRX configuration, aligning DRX On durations with TIM transmission periods to reduce power consumption by synchronizing the monitoring of LTE and WLAN carriers, and optimizes the timing of PS_Poll frames relative to LTE DRX ON durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE monitors both LTE and WLAN carriers continuously to ensure data reception, then data reception reliability is improved, but battery power consumption increases
Solution Approach 1:
The patent implements Discontinuous Reception (DRX) cycles where the UE alternates between active monitoring periods and sleep periods. During DRX On duration, the UE monitors LTE PDCCH for downlink data. During DRX Off duration, the UE turns off its radio to save battery power. This periodic monitoring approach maintains data reception reliability while significantly reducing power consumption compared to continuous monitoring.
Solution Approach 2:
The patent aligns LTE DRX cycles with WLAN power save modes by coordinating the timing of DRX On durations with TIM transmission periods. The UE synchronizes its active monitoring windows for both LTE and WLAN carriers, allowing it to monitor both networks simultaneously during aligned active periods and enter deep sleep during coordinated inactive periods. This merging of monitoring schedules improves power efficiency while maintaining reliability for both networks.
2Use of energy by moving object
If the UE aligns DRX On durations with TIM transmission periods to reduce power consumption, then battery power saving is improved, but timing synchronization complexity increases
Solution Approach 1:
The patent adjusts the DRX cycle parameters (onDurationTimer, drx-InactivityTimer, longDRX-Cycle, drxShortCycleTimer) to align with WLAN beacon intervals and TIM transmission periods. By modifying these timing parameters, the UE synchronizes its active monitoring windows with WLAN TIM messages without requiring complex real-time synchronization protocols. This parameter-based alignment reduces timing synchronization complexity while achieving power saving goals.
3Speed
If the UE sends PS_Poll frames immediately to retrieve buffered data, then data retrieval speed is improved, but signaling overhead increases
Solution Approach 1:
The patent sends PS_Poll frames during aligned DRX On durations and TIM transmission periods, rather than immediately upon detecting buffered data. This preliminary timing alignment ensures that the UE is already in an active monitoring state for both LTE and WLAN, allowing it to send PS_Poll without incurring additional wake-up overhead. The data retrieval speed is maintained because the UE is already active, while signaling overhead is reduced by avoiding redundant wake-up sequences.
Data Source
AI summary
In some implementations, a power saving method includes receiving, from a base station, at a user equipment (UE), a Discontinuous Reception (DRX) configuration. The UE determines a WLAN listen interval that includes at least one Traffic Indication Map (TIM) period and at least one TIM transmission period. The UE selects, based on the DRX configuration, a TIM message to monitor within an associated TIM transmission period from the at least one TIM transmission period in the listen interval. The UE determines a WLAN wakeup time that overlaps the associated TIM transmission period. During the associated TIM transmission periods, the UE receives, from an Access Point (AP), the selected TIM message.