VoIP Mobile E911 Call Setup Message Routing
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Solution Overview
Problem
Supporting E911 services for VoIP mobile communications is complicated due to the lack of fixed location information and the need for accurate location determination, especially in networks that support both fixed-line and mobile stations, as conventional methods are inadequate for VoIP telephony.
Innovation Solution
The mobile station formats a call setup message with specific information, such as the type of emergency call services and wireless network tower identification, to enable the wireless network to select the appropriate Public Safety Answering Point (PSAP) and route the call accurately, using protocols like SIP INVITE messages for VoIP communications over various networks like WiMAX, LTE, and WiFi.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If databases containing location information associated with each telephone number are used for fixed-line VoIP, then E911 location accuracy is maintained, but the system cannot handle mobile stations which lack fixed location information
Solution Approach 1:
The patent implements dynamic location determination for mobile stations by continuously tracking their position through network-based techniques (triangulation, multilateration) or device-based GPS, allowing the system to adapt to changing locations rather than relying on static database lookups. This enables mobile E911 support while maintaining location accuracy requirements.
Solution Approach 2:
The patent introduces location determination mechanisms as intermediaries between the mobile station and the PSAP routing system. These intermediaries (network-based location servers or device-based GPS) translate the mobile station's dynamic position into location information that can be used for PSAP selection, bridging the gap between mobile mobility and fixed-location routing requirements.
2Adaptability or versatility
If network-based location determination is used for mobile stations, then E911 Phase I support is achieved with coarse location accuracy, but E911 Phase II requirements for finer granularity cannot be met
Solution Approach 1:
The patent implements dynamic location determination for mobile stations by continuously tracking their position through network-based techniques (triangulation, multilateration) or device-based GPS, allowing the system to adapt to changing locations rather than relying on static database lookups. This enables mobile E911 support while maintaining location accuracy requirements.
Solution Approach 2:
The patent performs preliminary location determination by obtaining the mobile station's location information before routing the emergency call to the PSAP. This includes querying location servers, using GPS data, or calculating position based on network measurements, ensuring location accuracy is established in advance for both Phase I and Phase II requirements.
3Device complexity
If a single PSAP routing system is used for both fixed-line and mobile stations, then system complexity is reduced, but accurate routing for mobile stations with varying location requirements cannot be achieved
Solution Approach 1:
The patent creates a universal PSAP routing system that handles both fixed-line and mobile stations through a common architecture. The system determines station type (fixed or mobile) and applies appropriate location determination methods accordingly, allowing a single system to serve multiple functions while meeting different accuracy requirements through conditional processing logic.
Data Source
AI summary
Systems and methods for supporting E911 for VoIP mobile communications are provided. A mobile station formats a call setup message by including particular information in a header portion of the call setup message that is used by the wireless network to select an appropriate PSAP and route the call to the appropriate PSAP.