Call Manager Handover Between LTE and Circuit Switched Networks
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Solution Overview
Problem
Current wireless communication systems face challenges in performing seamless handover between Circuit Switching (CS) and Long Term Evolution/Service Architecture Evolution (LTE/SAE) systems, especially for terminals using only one radio channel, which leads to potential dropped calls due to movement between different networks.
Innovation Solution
A handover method and apparatus that utilizes a call manager to establish an Internet Protocol (IP) bearer between networks, allowing a terminal to switch from an LTE network to a CS network using a single radio channel by interacting with a Mobile Switching Center (MSC) and Internet Protocol Multimedia Subsystem (IMS) for anchoring calls, ensuring continuous service during handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a terminal uses only one radio channel to access either CS or LTE network, then the terminal cost is reduced and device complexity is lowered, but handover between networks becomes difficult and call continuity cannot be guaranteed
Solution Approach 1:
The patent introduces a call manager as an intermediary entity that anchors the call between the terminal and the network. The call manager receives the initial INVITE from the terminal via LTE, establishes the call, and enables handover by receiving a replacement INVITE from the target base station. This intermediary resolves the contradiction by managing the single radio channel terminal's handover without requiring dual radio channels, thus maintaining call continuity while keeping terminal complexity low.
2Adaptability or versatility
If handover is performed between CS and LTE systems, then network adaptability and service continuity are improved, but the complexity of the handover mechanism increases
Solution Approach 1:
The call manager serves multiple functions: it acts as an anchoring point for the terminal's call, manages handover between different network types (CS and LTE), and coordinates with both base stations and the IMS network. This multi-functional entity simplifies the overall handover mechanism by centralizing control, thereby improving network adaptability without proportionally increasing system complexity.
Solution Approach 2:
The call manager mediates between the terminal, source base station, and target base station during handover. It receives the replacement INVITE from the target base station, coordinates the call transfer, and ensures seamless handover. This intermediary approach simplifies the handover mechanism by providing a centralized coordination point, reducing the complexity that would otherwise arise from direct peer-to-peer interactions between multiple network elements.
3Use of energy by moving object
If simultaneous access to both CS and LTE networks is not available, then terminal power consumption and complexity are reduced, but dropped calls may occur during handover
Solution Approach 1:
The terminal performs measurements and sends handover requests to the call manager before actually switching networks. The call manager prepares for handover by receiving the replacement INVITE and coordinating with the target base station in advance. This preliminary action ensures that handover resources are prepared before the terminal switches networks, preventing dropped calls while maintaining single radio channel operation and keeping power consumption low.
Solution Approach 2:
The terminal continuously monitors network conditions and provides feedback to the call manager about signal quality and handover needs. The call manager uses this feedback to determine when to initiate handover procedures. This feedback mechanism ensures reliable handover execution without requiring simultaneous access to both networks, maintaining call connection reliability while keeping terminal power consumption and complexity low.
Data Source
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Figure 3A~3B
AI summary
Provided is a method for performing a handover between heterogeneous networks by a call manager of a network having a Circuit Switching, CS, network supporting a CS call, a Long Term Evolution, LTE, network supporting a packet call, and an Internet Protocol Multimedia Subsystem, IMS, network for anchoring a call, provides handover, from the LTE network to the CS network, to a user Equipment, UE, that uses a single radio channel and can access the CS network and the LTE network. The method includes receiving a handover request message from ENB of the LTE network, the handover request message being generated based on a measurement report of the UE; transmitting a handover prepare request message to a Mobile Switching Center, MSC, of the CS network; upon receiving a handover prepare complete message from the MSC, transmitting, to the UE, a handover command message to switch a LTE radio to a CS radio; and deleting a session of the LTE network for the UE.