RRC Connected Mobility State for LTE Power Saving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing LTE DRX mechanism in RRC Connected mode fails to realize significant power savings due to interruptions for handover measurements, measurement reports, and timing advance updates, especially in urban areas with frequent cell changes, limiting the effectiveness of power-saving modes during periods of low data activity.
Innovation Solution
Introducing a new RRC Connected Mobility state that allows user equipment (UE) to maintain a long DRX cycle and RRC connection while reselecting cells within a designated reselection area, reducing the need for handover measurements and timing advance updates, and using a shared CRNTI for multiple UEs to minimize signaling and collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the UE utilizes conventional DRX in RRC Connected mode, then power consumption is reduced during inactive periods, but DRX is frequently interrupted due to handover measurements, measurement reports, and timing advance updates
Solution Approach 1:
The patent segments the RRC Connected mode into two distinct sub-states: RRC Connected Normal (for stationary or slow-moving UEs requiring frequent network coordination) and RRC Connected Mobility (for moving UEs where cell reselection is more frequent). This segmentation allows the network to apply different DRX and mobility management strategies appropriate to each scenario, preventing unnecessary DRX interruptions in mobility scenarios.
Solution Approach 2:
The patent introduces dynamic state transitions between RRC Connected Normal and RRC Connected Mobility based on UE movement patterns and network conditions. The network can dynamically switch a UE between these states, adjusting the level of network control and DRX configuration accordingly, thereby optimizing both power consumption and connection reliability adaptively.
2Reliability
If the UE performs frequent handover measurements and sends measurement reports in RRC Connected mode, then mobility management is maintained, but signaling load increases and power savings are reduced
Solution Approach 1:
The patent applies different quality levels of network control to different UE scenarios. In RRC Connected Mobility state, the network provides minimal control (allowing autonomous cell reselection) while maintaining basic connectivity, whereas in RRC Connected Normal state, full network control with frequent measurements is maintained. This local differentiation optimizes the balance between mobility management quality and power consumption for each UE context.
Solution Approach 2:
The patent changes key parameters when transitioning between RRC Connected Normal and RRC Connected Mobility states, including DRX cycle lengths, measurement reporting frequencies, and handover trigger thresholds. These parameter adjustments reduce signaling overhead and power consumption in mobility scenarios while maintaining adequate mobility management.
3Use of energy by moving object
If the UE transitions to RRC Idle state to save power, then power consumption is reduced, but data transmission capability and network connectivity are lost
Solution Approach 1:
The patent inverts the conventional approach by allowing the UE to remain in RRC Connected state (with data transmission capability maintained) while implementing mobility-based power saving through the new RRC Connected Mobility state. Instead of transitioning to Idle to save power, the UE can use autonomous cell reselection in the Connected Mobility state to reduce signaling and power consumption while maintaining connectivity and data transmission capability.
4Reliability
If the network maintains strict control over UE mobility in RRC Connected mode, then connection reliability is improved, but device complexity and signaling overhead increase
Solution Approach 1:
The patent implements dynamic mobility management where the network adjusts its level of control based on UE state. In RRC Connected Mobility state, the network adopts a more dynamic, trust-based approach allowing autonomous cell reselection, reducing both network and device complexity. In RRC Connected Normal state, strict network control is maintained. This dynamic adjustment optimizes the balance between connection reliability and complexity.
Data Source
AI summary
A new RRC Connected (mobility) state is described in which a UE utilizes a temporary identifier to monitor a downlink control channel in accordance with a discontinuous reception cycle; and maintains the new connected state, the discontinuous reception cycle and the temporary identifier while the UE re-selects to a second/serving access node which lies within a same designated reselection area as a first/source access node. In various specific embodiments, the DRX cycle is maintained but re-aligned with a system frame number of the second access node; the temporary identifier is a CRNTI and the designated re-selection area is defined by all contiguous cells in which respective access nodes broadcast the CRNTI in system information; the UE re-selects to the second access node in the absence of control signaling; and the UE enters the new connected mobility state automatically upon expiry of a time alignment timer or upon explicit network signaling while in a different connected state.