Circuit Switched Fallback Mechanism for LTE to WCDMA Transition
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Solution Overview
Problem
Conventional LTE systems do not support circuit switched communications, preventing mobile stations from performing both transmission and reception of CS-domain services when camping on an LTE scheme.
Innovation Solution
A mobile communication system that includes a first communication scheme LTE, a second communication scheme WCDMA/GSM capable of supporting CS communications, and a mobile station with protocol processor units to facilitate protocol processing between different network apparatus, allowing the mobile station to initiate CS communications by selecting a WCDMA/GSM cell for circuit switched communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mobile station camps on an LTE system, then packet switched communications are available, but circuit switched communications cannot be performed
Solution Approach 1:
The patent introduces a relay node as an intermediary between the LTE eNodeB and the WCDMA/GSM network. This relay node enables the mobile station to access circuit switched services through the LTE network by converting packet switched traffic to circuit switched traffic, thus resolving the contradiction between LTE packet switched capability and CS-domain service requirement
Solution Approach 2:
The relay node performs multiple functions: it acts as a base station for mobile stations, connects to both LTE and WCDMA/GSM networks, provides circuit switched service capability, and enables fallback operations. This multi-functionality allows the system to support both packet switched (LTE) and circuit switched (WCDMA/GSM) communications simultaneously
2Adaptability or versatility
If circuit switched fallback to WCDMA/GSM is implemented, then CS-domain services become available, but communication setup time increases
Solution Approach 1:
The relay node is pre-configured with WCDMA/GSM network parameters and circuit switched service capabilities before the mobile station needs to access these services. This preliminary setup eliminates the need for real-time network registration and configuration, significantly reducing the communication setup time when CS services are required
Solution Approach 2:
By having the relay node as a pre-established intermediary with direct connections to both LTE and WCDMA/GSM networks, the mobile station can quickly switch between communication modes without undergoing full handover procedures, thus reducing setup time while maintaining CS service capability
3Adaptability or versatility
If a relay node is introduced to enable CS communications, then CS-domain services become available, but device complexity increases
Solution Approach 1:
The relay node is designed as a universal platform that supports multiple communication schemes (LTE and WCDMA/GSM), multiple service types (packet switched and circuit switched), and multiple operational modes (direct connection, fallback, handover). This multi-functionality consolidates what would otherwise require multiple separate systems into a single integrated node, managing complexity through functional consolidation
Data Source
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AI summary
When a mobile station (UE) is camping on a system of the LTE scheme, a function (EMM) is configured to transmit a service request signal including a "CSFB" to an MME; the MME is configured to transmit setup information including a "CSFB" to an eNB in response to the service request signal transmitted by the function (EMM); the eNB is configured to transmit, to a function (AS), instruction information instructing to select a cell in a system of the WCDMA/GSM scheme in response to the setup information transmitted by the MME; the function (AS) is configured to select the cell in the system of the WCDMA/GSM scheme in accordance with the instruction information transmitted by the eNB; and the function (MM) is configured to set up circuit switched communications via the cell in the system of the WCDMA/GSM scheme selected by the function (AS).