UE State Transition for Circuit-Switched Call Setup Latency
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Solution Overview
Problem
In UMTS networks, transitioning from CELL_PCH or URA_PCH states to CELL_DCH state during circuit-switched voice call setup is inefficient, leading to increased latency and potential call setup failures due to reliance on CELL_FACH state, which lacks dedicated channels and closed-loop power control, especially in boundary areas where soft handover is not possible.
Innovation Solution
A method for user equipment (UE) to transition directly to a CELL_DCH state by sending a cell update message with a traffic volume indicator exceeding a threshold, or using a traffic volume measurement report, to facilitate faster circuit-switched call setup, reducing latency and improving call success rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the network keeps the device in CELL_FACH state during call setup, then network signaling is simplified, but call setup latency increases
Solution Approach 1:
The UE proactively sends a cell update message with traffic volume indicator before the network transitions it to CELL_DCH state, pre-triggering the transition process. This preliminary action reduces the time the device remains in CELL_FACH state during call setup, resolving the contradiction by initiating the state transition in advance while maintaining simplified network signaling procedures.
2Loss of time
If the device transitions directly to CELL_DCH state, then call setup latency is reduced, but network signaling complexity increases
Solution Approach 1:
The UE autonomously determines when to send the cell update message with traffic volume indicator based on its own traffic conditions and call setup requirements, without requiring complex network signaling protocols. The device self-manages the state transition timing, reducing call setup latency while avoiding increased network signaling complexity by using existing signaling mechanisms.
3Use of energy by moving object
If the device remains in CELL_PCH or URA_PCH state, then power consumption is reduced, but connection establishment time increases
Solution Approach 1:
The UE sends the cell update message with traffic volume indicator in advance during call setup, pre-triggering the transition from CELL_PCH or URA_PCH to CELL_DCH state. This preliminary action reduces the time the device needs to spend in low-power states during connection establishment, resolving the contradiction by initiating the transition before full connection is required.
4Device complexity
If soft handover is not possible in CELL_FACH state, then device complexity is reduced, but call setup reliability decreases in boundary areas
Solution Approach 1:
The UE proactively triggers the transition to CELL_DCH state by sending the cell update message with traffic volume indicator before call setup begins. This preliminary transition ensures the device is in a state that supports soft handover before entering boundary areas, resolving the contradiction by establishing the appropriate radio resource control state in advance to ensure reliable call setup.
Data Source
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AI summary
A method at a user equipment for establishing a circuit switched call, the user equipment being in a Cell Forward Access CHannel (CELL_FACH) state, a Cell Paging CHannel (CELL_PCH) state or a UTRAN Registration Area Paging CHannel (URA_PCH) state, the method receiving an indication that a circuit switched call is pending; sending to a network element a message to facilitate the user equipment to transition to a Cell Dedicated CHannel (CELL_DCH) state, the message being one of a cell update message having a traffic volume indicator information element indicating that pending uplink data exceeds a threshold or an RRCConnectionRequest message; and establishing the circuit switched call.