Third Party Call Control Signaling via Tunneled FACILITY Messages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current voice telephony systems face challenges in efficiently transporting control and status information over packet-switched networks, particularly for third-party call control, as existing signaling formats like DTMF tones are susceptible to corruption and filtering, and do not effectively support data channel availability for mobile devices.
Innovation Solution
The system employs the FACILITY message, which is defined in ISDN and GSM standards, to encode control and status information in a format that deviates from standard phone number conventions, allowing it to be interpreted as control or status information by third-party call control servers, even when transmitted over different protocols like SIP, ISDN, SS7, and GSM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DTMF tones are used for control signaling, then compatibility with legacy systems is maintained, but reliability deteriorates due to susceptibility to corruption and filtering
Solution Approach 1:
The patent introduces an intermediary encoding scheme that translates control commands into non-standard phone number formats. These encoded numbers are transmitted through the telephony network as if they were regular calling numbers, but are actually decoded by the receiving end to extract control commands. This intermediary layer protects the reliability of control signaling while maintaining compatibility with legacy DTMF-based systems.
Solution Approach 2:
The patent changes the parameter representation of control signals by encoding them as non-standard phone numbers rather than using traditional DTMF tones or in-band signaling. By modifying the format parameter (from audio tones to structured numeric strings) and utilizing out-of-band data channels, the system achieves both reliability and legacy compatibility.
2Device complexity
If traditional signaling formats are used, then simplicity is maintained, but adaptability deteriorates for mobile devices and packet-switched networks
Solution Approach 1:
The patent creates a universal signaling mechanism that works across multiple network types (circuit-switched and packet-switched) and device types (landline and mobile). By encoding control information in a standardized format that can be transported through various protocols (SS7, SIP, GSM), the system achieves multi-functionality without significantly increasing the complexity of individual components.
Solution Approach 2:
The encoded phone number format serves as a universal intermediary that can be processed by different network infrastructures. The same encoding scheme works whether the signal traverses traditional SS7 networks, modern SIP-based VoIP networks, or mobile GSM networks, providing adaptability while maintaining a relatively simple core signaling format.
3Ease of manufacture
If in-band signaling is used, then ease of implementation is maintained, but information loss occurs due to filtering and corruption
Solution Approach 1:
The patent extracts control information from the voice band (in-band signaling) and places it in the out-of-band data channel or signaling channel. By separating the control information extraction from the voice transmission path, the system avoids the filtering and corruption issues that affect in-band signaling, while the implementation remains relatively simple by utilizing existing network capabilities.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Aspects relate to call control by third parties, where IP or a similar transport is used over a part of the channel for a given call and circuit-switched signaling protocols are used on a different part. For example, a PBX can communicate using SIP signaling to a gateway to a PSTN network, to which a Public Land Mobile Network (PLMN) is coupled, and which a mobile device, uses for voice communication. Controlling or updating status in these kinds of situations can be accomplished by forming a Q.931/932 message, such as a FACILITY message, which has fields (Information Elements) for pre-defined purposes (other than third party call control), and providing control or status information in such field(s). The message (the info) is tunneled through the gateway and the network(s), and arrives at its destination device. That device determines that a field does not comport with a valid format interpretation, and on that basis, can determine that the field has contents to be interpreted as call control or status information.