VoIP Terminal WLAN LTE Handover Signal Monitoring
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Solution Overview
Problem
In wireless communication systems using LTE/SAE and LTE Advanced, VoIP services over wireless local area networks (WLANs) face disruptions when users move out of coverage, leading to unnecessary resource wastage and call delays due to the lack of immediate recognition of connection losses by the Proxy-Call Session Control Function (P-CSCF).
Innovation Solution
A system and method that monitor signal intensity and packet loss rates during VoIP communication, switching to an always-on IP connection using a second mobile IP from the LTE/SAE network if the WLAN signal weakens or packet loss exceeds a threshold, allowing seamless VoIP service continuity by re-establishing SIP and RTP sessions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the terminal uses wireless LAN for VoIP service, then the cost is reduced and service is provided, but the service continuity cannot be guaranteed when the user moves away from the access point
Solution Approach 1:
The patent combines wireless LAN and wireless packet network modules in a single terminal, allowing the device to utilize both networks. The terminal can switch between WLAN and packet network based on signal conditions, ensuring continuous VoIP service while maintaining cost benefits of WLAN when available.
Solution Approach 2:
The terminal performs SIP registration with the packet network in advance, maintaining an always-on IP connection. This preliminary action ensures that when WLAN connection is lost, the terminal can immediately switch to the pre-established packet network connection without service interruption.
2Reliability
If the terminal repeatedly performs registration refresh procedures, then the connection state is maintained, but resources are wasted by unnecessary retransmission when connection is already lost
Solution Approach 1:
The system implements feedback mechanisms where the terminal monitors packet reception from the network. When the terminal detects that packets are not being received (indicating connection loss), it stops performing unnecessary registration refresh procedures and SIP retransmissions, thereby conserving resources while maintaining connection state awareness.
3Reliability
If the terminal monitors signal intensity and switches to always-on IP connection, then VoIP service continuity is maintained, but the device complexity increases
Solution Approach 1:
The terminal is designed with multi-functionality, incorporating both wireless LAN and wireless packet network modules that can serve dual purposes. The same hardware components are used for both cost-effective WLAN operation and reliable always-on packet network connection, reducing the need for additional specialized equipment.
Data Source
AI summary
In a system to control a VoIP service, a user terminal performs a first registration procedure of a CSCF through a first P-CSCF using a first mobile IP allocated from a wireless LAN, monitors a signal intensity of the wireless LAN while receiving the VoIP service over the wireless LAN, and performs a second registration procedure through a second P-CSCF using a second mobile IP allocated from a wireless packet network upon booting if the signal intensity of the wireless LAN becomes weaker than a reference value. The CSCF sends a VoIP call to the second P-CSCF if the user terminal performs the second registration procedure and the user terminal then receives an incoming VoIP call.