CSFB Call Setup Deferring Packet-Switched Registration

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Solution Overview

Problem

Circuit-switched fallback (CSFB) calls in wireless communication systems experience long call setup times due to the need for wireless devices to change networks and perform packet-switched registration procedures, which can delay call establishment.

Innovation Solution

Delaying packet-switched registration procedures until after the circuit-switched fallback call is established, allowing the wireless device to initially focus on setting up the CSFB call and then perform PS registration, thereby reducing call setup time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If packet-switched registration procedures are performed during circuit-switched fallback call establishment, then complete service registration is achieved, but call setup time increases

Engineering Contradiction:

Improveservice registration completenessVSAvoidcall setup time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by performing the essential circuit-switched call setup procedures first to establish the call quickly, then subsequently performing the packet-switched registration procedures. This sequencing ensures the call is established with minimal delay while complete service registration is eventually achieved.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the registration process into two distinct phases: (1) circuit-switched call establishment phase where only essential CS services are registered, and (2) subsequent packet-switched registration phase where PS services are registered. This segmentation allows the critical call setup to proceed independently without being blocked by PS registration procedures.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If routing area update procedure is performed during CS call establishment, then packet-switched services are resumed, but call setup time increases by approximately 1 second

Engineering Contradiction:

Improvepacket-switched service availabilityVSAvoidcall setup time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent performs the routing area update procedure as a preliminary action that is deferred until after the CS call is established. The UE initiates the routing area update procedure after call establishment, allowing the call setup to complete without the 1-second delay that would otherwise be incurred during the security mode command and routing area update procedures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent dynamically adjusts the timing of the routing area update procedure based on the call establishment state. Rather than performing it synchronously during call setup, the system dynamically schedules the RAU procedure to occur after the call is established, optimizing the balance between service availability and call setup speed.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8817749B2Call setup for circuit switched fall back calls

Publication Date: 2014.08.26 APPLE INC

AI summary

Establishing a circuit-switched fallback (CSFB) call. A request to establish a CSFB call may be received. A first wireless link with a first cell may be released. The first cell may provide packet-switched services but not circuit-switched services. A second wireless link may be established with a second cell. The second cell may provide packet-switched services and circuit-switched services. The CSFB call may be established via the connection to the second cell. Packet-switched registration with the second cell may be performed after the CSFB call is established.